U.S. patent application number 10/734604 was filed with the patent office on 2005-01-06 for nxm crosspoint switch with band translation.
Invention is credited to Bargroff, Keith P., Fransis, Bert L., Lazarescu, Raducu, Mellissinos, Tony, Papathanasiou, Kostas, Rampmeier, Keith J., Tarvainen, Esa, Wang, Donghai.
Application Number | 20050005296 10/734604 |
Document ID | / |
Family ID | 32512584 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050005296 |
Kind Code |
A1 |
Bargroff, Keith P. ; et
al. |
January 6, 2005 |
NxM crosspoint switch with band translation
Abstract
An N.times.M crosspoint switch allows a signal from any one of
the N inputs to be routed to one or more of the M crosspoint switch
outputs. The switches within the crosspoint switch can be
configured as voltage mode or current mode switches. In voltage
mode switching an input to the crosspoint switch is provided to an
input device, such as an amplifier, having a low output impedance.
The output of the low impedance device is provided to a switch that
connects the output of the low impedance device to a high input
impedance device, such as a band translation device. In current
mode switching, the low impedance output of the input device is
connected to selectively activated high isolation transconductance
devices having high input impedances. The outputs of the
transconductance devices are connected to low impedance devices
that operate as summing nodes.
Inventors: |
Bargroff, Keith P.; (San
Diego, CA) ; Fransis, Bert L.; (San Diego, CA)
; Rampmeier, Keith J.; (San Diego, CA) ;
Lazarescu, Raducu; (San Diego, CA) ; Papathanasiou,
Kostas; (Houston, TX) ; Tarvainen, Esa; (San
Diego, CA) ; Mellissinos, Tony; (Carlsbad, CA)
; Wang, Donghai; (San Diego, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
32512584 |
Appl. No.: |
10/734604 |
Filed: |
December 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60433066 |
Dec 11, 2002 |
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60433061 |
Dec 11, 2002 |
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60433067 |
Dec 11, 2002 |
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60433063 |
Dec 11, 2002 |
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Current U.S.
Class: |
725/63 ; 725/68;
725/71 |
Current CPC
Class: |
H03D 7/1425 20130101;
H04N 7/102 20130101; H03D 7/1458 20130101; H04N 7/20 20130101; H03F
2200/451 20130101; H04Q 2213/13322 20130101; H03F 3/19 20130101;
H04B 1/126 20130101; H03G 3/3036 20130101; H03D 2200/0043 20130101;
H04H 40/90 20130101; H03F 2200/294 20130101; H03D 7/1433 20130101;
H03D 2200/0025 20130101; H04Q 2213/13034 20130101; H03D 7/00
20130101; H04Q 3/521 20130101; H03F 2200/171 20130101; H04Q
2213/1302 20130101; H04Q 2213/1319 20130101; H04Q 2213/1304
20130101 |
Class at
Publication: |
725/063 ;
725/068; 725/071 |
International
Class: |
H04N 007/20 |
Claims
What is claimed is:
1. An integrated circuit, having N-input by M-output crosspoint
switch with band translation, for use in an RF signal distribution
system, the integrated circuit comprising: an N input switch
configured to route an input signal at any one of the N inputs to
any one of the M outputs, with each of the N inputs having a high
input impedance; and M band translation devices, each of the M band
translation devices connected to an output of the N input switch
and configured to selectively frequency translate or pass through a
signal from the output of the N input switch.
2. The integrated circuit of claim 1, wherein the N input switch
comprises N groups of M switches, with each group of M switches
having inputs connected to a separate one of the N inputs, each
group of M switches further having each of the M switch outputs
connected to a separate one of the M band translation devices.
3. The integrated circuit of claim 2, wherein each switch in the N
groups of M switches comprises a voltage mode switch and wherein
each of the band translation devices has a high impedance
input.
4. The integrated circuit of claim 2, wherein each switch in the N
groups of M switches comprises a current mode switch and wherein
each of the band translation devices has a low impedance input.
5. The integrated circuit of claim 2, wherein each switch in the N
groups of M switches comprises a transconductance device.
6. The integrated circuit of claim 2, wherein each switch in the N
groups of M switches is selectively enabled or disabled based on a
control signal.
7. The integrated circuit of claim 2, wherein each switch in the N
groups of M switches provides greater than 30 dB of signal
isolation in a disabled state.
8. The integrated circuit of claim 1, further comprising N low
noise amplifiers (LNAs), with each LNA having an output connected
to a separate input on the N input switch.
9. The integrated circuit of claim 1, wherein the N input switch
and the M band translation devices include differential signal
inputs and differential signal outputs.
10. The integrated circuit of claim 1, wherein each of the M band
translation devices is configured to frequency translate a signal
from a first RF frequency band to a second RF frequency band.
11. An integrated circuit having a crosspoint switch with band
translation for use in an RF signal distribution system, the
integrated circuit comprising: a first low noise amplifier (LNA)
having a differential input and a low impedance differential
output; a first transconductance device having a differential
output and a high impedance differential input connected to the low
impedance differential output of the first LNA; a second
transconductance device having a differential output and a high
impedance differential input connected to the low impedance
differential output of the first LNA; a first band translation
device having a differential output and a low impedance
differential input connected to the differential output of the
first transconductance device; and a second band translation device
having a differential output and a low impedance differential input
connected to the differential output of the second transconductance
device.
12. The integrated circuit of claim 11, wherein the first
transconductance device comprises a controllable current source
configured to selectively enable and disable the first
transconductance device.
13. A method of routing signals in a reconfigurable signal
distribution system, the method comprising: receiving a signal at a
matched impedance input of a low noise amplifier (LNA) having a low
output impedance; selectively routing an output voltage of the LNA,
using a first transconductance device having a high impedance
input, as a current at an output of the first transconductance
device; selectively routing an output voltage of the LNA, using a
second transconductance device having a high impedance input, as a
current at an output of the second transconductance device; and
frequency translating a signal at the output of the first
transconductance device from a first RF frequency band to a second
RF frequency band.
14. A method of routing signals in a reconfigurable signal
distribution system, the method comprising: receiving an input
signal at a matched impedance input of a input device; generating
an intermediate signal, based in part on the input signal, at the
low impedance output of the input device; providing the
intermediate signal to a high impedance input of a current source;
selectively enabling the current source to provide an output
current signal based in part on the intermediate signal; receiving
the output current signal at a low impedance input of a band
translation device; and frequency translating the output current
signal from a first frequency band to a second frequency band.
Description
PRIORITY APPLICATIONS
[0001] This application claims priority to, and hereby incorporates
by reference in their entirety, the following patent
applications:
[0002] U.S. Provisional Patent Application No. 60/433,066, filed on
Dec. 11, 2002, entitled INTEGRATED CROSSPOINT SWITCH WITH BAND
TRANSLATION;
[0003] U.S. Provisional Patent Application No. 60/433,061, filed on
Dec. 11, 2002, entitled IN-LINE CASCADABLE DEVICE IN SIGNAL
DISTRIBUTION SYSTEM WITH AGC FUNCTION;
[0004] U.S. Provisional Patent Application No. 60/43,067, filed on
Dec. 11, 2002, entitled N.times.M CROSSPOINT SWITCH WITH BAND
TRANSLATION;
[0005] U.S. Provisional Patent Application No. 60/433,063, filed on
Dec. 11, 2002, entitled MIXER WITH PASS-THROUGH MODE WITH CONSTANT
EVEN ORDER GENERATION.
BACKGROUND OF THE INVENTION
[0006] 1. Field of the Invention
[0007] The present invention relates to the field of electronic
devices. More particularly, the invention relates to integrated
circuit switches and frequency translation.
[0008] 2. Description of the Related Art
[0009] Signal distribution systems are typically required to
distribute a signal, such as an RF signal to one or more locations
within the signal distribution system. The signal distribution
system can be reconfigurable to allow routing of signals to be
changed from an initial configuration. The reconfiguration of the
signal distribution system can occur on-the-fly, while the system
is in use. Reconfiguration of signal routing paths can be
accomplished with switches.
[0010] However, switching transients can induce noise onto a signal
distribution system and can affect the signal quality of other
signal distribution paths. Additionally, switch isolation can
affect signal quality of other signals in the signal distribution
system. Low signal isolation may result in noise in the form of
crosstalk from one signal path contaminating a second signal path.
Changes in path loading, as a result of switching signal paths into
and out of a signal path, can also result in increased noise or
distortion in the signal path.
[0011] Signal distribution flexibility and the ability to
reconfigure a signal distribution system on-the-fly is desirable.
Yet signal degradation of signals distributed throughout the signal
distribution system as a result of signal routing flexibility is to
be minimized if signal quality is to be maintained within the
signal distribution system. Within a reconfigurable signal
distribution system, it is desirable to maintain signal isolation,
minimize noise contributions including noise contributed by any
switching transients, minimize signal distortion, and minimize
current consumption.
SUMMARY OF THE INVENTION
[0012] According to one aspect of the invention, an N.times.M
crosspoint switch allows a signal from any one of the N inputs to
be routed to one or more of the M crosspoint switch outputs. The
switches within the crosspoint switch can be configured as voltage
mode or current mode switches. In voltage mode switching an input
to the crosspoint switch is provided to an input device, such as an
amplifier, having a low output impedance. The output of the low
impedance device is provided to a switch that connects the output
of the low impedance device to a high input impedance device, such
as a band translation device. In current mode switching, the low
impedance output of the input device is connected to selectively
enabled high isolation transconductance devices having high input
impedances. The transconductance devices operate as switches in the
current mode switching device. The outputs of the transconductance
devices are connected to low impedance devices that operate as
summing nodes.
[0013] In another aspect, the switches are configured to provide
high input to output signal isolation in a disabled state and
connect the input to the output in an enabled state. The switch can
provide voltage gain or current gain in the enabled state.
[0014] Additionally, in another aspect, the N.times.M crosspoint
switch can be implemented as a single integrated circuit or can be
implemented as multiple integrated circuits. The use of current
mode switching or voltage mode switching is transparent to the user
of the integrated circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The features, objects, and advantages of the invention will
become more apparent from the detailed description set forth below
when taken in conjunction with the drawings in which like reference
characters identify correspondingly throughout and wherein:
[0016] FIG. 1 is a functional block diagram of a satellite
communication system configured to provide signals from multiple
satellites to multiple user devices.
[0017] FIG. 2 is a functional block diagram of an integrated
crosspoint switch with band translation.
[0018] FIGS. 3A-3D are functional block diagrams of switches.
[0019] FIG. 4 is a functional block diagram of an integrated
crosspoint switch with band translation.
[0020] FIG. 5 is a functional block diagram of an integrated
crosspoint switch with band translation.
[0021] FIG. 6 is a functional block diagram of an integrated
crosspoint switch with band translation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] FIG. 1 is a functional block diagram of one embodiment of a
satellite based communication system, such as a satellite
television system 100. However, the invention is not limited to
application in a satellite based communication system, nor is the
invention limited to use in a television system. The invention is
applicable to any communication system where multiple signals in
one or more input frequency bands can be distributed as signals in
one or more output frequency bands to one or more receivers.
[0023] The satellite television system 100 includes one or more
satellites 110a-110c that are set at various different orbital
slots. Although three satellites 110a-110c are shown in FIG. 1, any
number of satellites can exist in a particular satellite television
system 100. The satellites can operate at different carrier
frequencies and polarizations. The different carrier frequencies
and polarizations that can be used by the satellites 110a-110c
provide a degree of isolation of one satellite transmission from
another. Additionally, the satellites 110a-110c can implement a
directional antenna to provide further signal selectivity. Thus, a
receiver can select the signals from a desired satellite, for
example 110a, by receiving the broadcast signals with a
corresponding polarized antenna oriented in the general direction
of the desired satellite 110a and tuning to the desired satellite
frequency. Because each satellite 110a-110c is configured in a
similar manner, a more detailed description is provided for only
one of the satellites 110a.
[0024] A satellite 110a in a satellite television system 100 can
include a single transponder (not shown), but typically includes
multiple transponders. Each of the transponders typically transmits
at a different frequency and has an associated polarization. Two
different transponders on the same satellite 110a can transmit on
the same frequency but with different polarities if the selectivity
provided by the difference in polarities is sufficient for the
system. If each transponder transmits at a different frequency, the
different transponders on a single satellite 110a can all transmit
with the same polarity, or can use different polarities.
[0025] Additionally, some transponders can be configured with
multiple carrier frequencies having various channel offsets. Other
transponders may multiplex numerous digital channels on a single
carrier. The integrated crosspoint switch with band translation
described below can be configured to operate over one or more
frequency bands with any transponder modulation type.
[0026] For example, a satellite 110a can include a first
transponder that provides information on multiple carrier
frequencies, with the carrier frequency spacing corresponding to a
channel spacing for a television receiver. The transponders in a
satellite 110a are typically arranged as transponder groups. For
example, the transponder group can be configured to provide a
contiguous group of channels. Alternatively, the signals in a
particular transponder group can have varied channel offsets, with
one or more channels having different carrier bandwidths or symbol
rates. Additionally, the transponders in a satellite group can be
configured to all transmit using the same polarization. A typical
satellite 110a configured for a satellite television system 100 can
include two transponder groups having sixteen transponders in each
transponder group, with each group having a different polarity. Of
course, the satellite 110a is not limited to any particular
transponder configuration, nor are transponder groups necessarily
limited to sixteen transponders.
[0027] A satellite 110a configured to operate in a satellite
television system 100 typically transmits downlink signals in one
of two frequency bands. Each frequency band can include one or more
channels corresponding to one or more transponders. A first
downlink frequency band is in the C-band and typically spans
3.6-4.2 GHz. A second downlink frequency band is in the Ku-band and
typically spans 10.7-12.75 GHz. Of course, each satellite or some
other signal source may transmit signals over one or more frequency
bands. The frequency bands are not limited to the two listed
frequency bands, and may be any suitable frequency bands, including
one or more frequency bands that have yet to be defined and
allocated by regulating bodies.
[0028] Of course, the upper and lower band edges for the one or
more downlink frequency bands are not absolutes because of the
practical limitations on constructing a brick wall filter. Rather,
the frequency bands typically represent passbands and the operating
transponder downlink frequency band typically comprises a frequency
band that includes a frequency band having the upper and lower band
edges within the passband. Alternatively, the band edges can define
stop band edges and the transponder can transmit a substantially
diminished energy outside of the band edge frequencies. Thus,
practically, the downlink frequency bands can span about, or
substantially, 3.6-4.2 GHz and 10.7-12.75 GHz. Additionally, while
a satellite 110a can be configured to use a particular downlink
frequency band, the satellite 110a may not actually transmit
signals at all frequencies within the downlink frequency band. A
satellite 110a is not limited to transmitting a downlink signal in
these two frequency bands, and there can be additional downlink
frequency bands implemented by the satellite 110a. These additional
downlink frequency bands can be distinct from the previously
described downlink frequency bands or can overlap some or all of
the previously described downlink frequency bands.
[0029] The downlink signals transmitted by the satellites 110-110c
can be received by a terrestrial television system and displayed to
one or more televisions 170a-170c. An antenna 120 is typically used
to receive the signals from the satellites 110a-110c. The antenna
120 is shown in FIG. 1 as a dish antenna but other antenna 120
configurations can also be used. In the embodiment implementing a
dish antenna 120, a reflector can direct the downlink signals to an
antenna feed 122. Although the antenna 120 is shown with only one
antenna feed 122, one or more antenna feeds 122 can be implemented
on a single antenna 120. Some antenna configurations suitable for
operation within the system can not include an antenna feed 122.
The antenna 120 or antenna feed 122 can be configured to receive
signals from a particular downlink frequency band or a particular
polarization. For example, the antenna 120 and antenna feed 122 can
be configured to receive the 10.7-12.75 GHz frequency band having a
left hand circular polarization. Another antenna feed (not shown)
included as part of the antenna 120 can be configured to receive
another downlink frequency band having the same or different
polarization. Additionally, although one antenna 120 is shown in
FIG. 1, multiple antennae can be implemented in a location or
multiple locations as part of a single system.
[0030] The output from the antenna 120 is connected to a receiver
180 that is used to process the received signals. In a typical
satellite television system 100 the receiver 180 includes low noise
amplifiers that amplify the signals while minimizing the associated
noise contribution. Additionally, the signals received at the
satellite downlink frequencies are typically frequency translated
to one or more predetermined frequency bands, or common
Intermediate Frequency (IF) bands. The received downlink signals
can also be filtered to remove out of band signals that can
contribute interference.
[0031] In one embodiment the carrier frequency spacing of the
downlink signals transmitted by the satellites 110a-110c typically
corresponds to a channel spacing used by a television receiver or a
set top box. In this embodiment, it can be advantageous to
frequency convert the entire received downlink frequency band to
one of the predetermined frequency bands used by television
receivers or set top boxes. Alternatively, the received downlink
frequency band can be frequency converted to predetermined
frequency bands at intermediate frequencies for further processing
prior to conversion to frequencies compatible with television
receivers or set top boxes. In another embodiment, several channels
may be multiplexed using a single carrier. In this embodiment, one
or more multiplexed carriers can be frequency converted to input
frequencies of a set top box.
[0032] The process of low noise amplification, filtering and
initial frequency conversion can be performed by low noise block
converters (LNB) 130a-130c. Three LNB's are shown in FIG. 1, though
fewer or more can be used. A LNB, for example 130a, can be
configured to receive signals from one or more antennae, for
example 120, amplify, filter, and block frequency convert the
signals to a common IF band. A first set of downlink signals, such
as those from a first transponder group, can be block converted to
a first common IF band and a second set of downlink signals, such
as those from a second transponder group, can be block converted to
a second common IF band. For example, the LNB 130a can receive
downlink signals from two transponder groups. The multiple signals
from two transponder groups can be received at one or more antennae
120, or one or more antenna feeds 122. Additionally, the downlink
signals can originate from one satellite, for example 110a, or more
than one satellite 110a-110c.
[0033] For example, the LNB 130a can block convert the signals from
the first transponder group to a common IF band of 950-1450 MHz.
Similarly, the LNB 130a can simultaneously block convert the
signals from the second transponder group to a common IF band of
1650-2150 MHz. The block converted signals at the two common IF
bands can be combined prior to being output from the LNB 130a. This
process of block converting two transponder groups to different
predetermined frequency bands and then combining the signals from
the predetermined frequency bands is commonly referred to as
band-stacking. In the previous example, the band stacked output
from the LNB 130 comprises block converted transponder signals in a
first common IF band at 950-1450 MHz and block converted
transponder signals in a second common IF band at 1650-2150 MHz.
Conceivably, based on the channel spacing and carrier bandwidths
employed in particular transponder groups, signals from two
transponder groups can be block converted to the same common IF
band and combined without having two channels assigned to the same
carrier frequency. Typically, two independent signals would not be
combined at the same IF carrier frequency because each would appear
as an interference source for the other, potentially making both
signals unresolvable. In systems such as TDM or CDM systems, two
signals can occupy the same frequency space and still be
independently resolvable provided they occupy different spaces in
other dimensions, such as time or code.
[0034] If the number of transponder groups exceeds the number of
predetermined frequency bands, or common IF bands, it may not be
possible to band-stack the signals from all of the transponder
groups. In such a situation, the band-stacked output from a
particular LNB 130a may constitute only a subset of all available
transponder groups. Additional LNB's 130b-130c can be used to
ensure that signals from all of the transponder groups are
represented in one of the band-stacked outputs of the LNB's
130a-130c. However, the band-stacked outputs of the LNB's 130a-130c
are not limited to having signals from distinct transponder groups.
Thus, one or more of the band-stacked LNB outputs can have signals
in common with another of the band-stacked LNB outputs. In other
embodiments, band-stacking is not used, and each transponder group
is outputted from the LNB independently.
[0035] The outputs from the LNB's 130a-130c are connected to the
input of a switch configuration, referred to herein as an N.times.M
crosspoint switch 140. The N.times.M crosspoint switch 140 includes
N inputs and M outputs. Signals from each of the N inputs can be
selectively routed to any of the M outputs. Thus, the band-stacked
output from a first LNB 130a can be connected to a first input of
the crosspoint switch 140 and can be selectively routed to any of
the outputs of the crosspoint switch 140.
[0036] The crosspoint switch 140 can be configured such that only
one input can be selectively routed to an output. Alternatively,
the crosspoint switch 140 can be configured to selectively route
more than one input to the same output. Additionally, the
crosspoint switch 140 can also be configured such that an input
signal can be selectively routed to only one output. Alternatively,
the crosspoint switch 140 can be configured to selectively route an
input signal to more than one output. Typically, the crosspoint
switch 140 is configured to selectively route an input to a single
output and only one input can be routed to the particular output.
Where the crosspoint switch 140 configuration limits one output to
one input, there can be some inputs that cannot be routed to
outputs if the number if inputs, N, is greater than the number of
outputs, M. Similarly, some input signals can not be able to be
routed to an output if the crosspoint switch 140 configuration
limits an output to a signal from only one input, and one input can
be routed to multiple outputs.
[0037] Conversely, some outputs can not have any signals routed to
them if the crosspoint switch 140 configuration only allows one
input to be routed to one output and the number of inputs, N, is
less than the number of outputs, M. Similarly, some outputs may not
have any signals routed to them if multiple inputs can be routed to
the same output and an input can only be routed to one output. The
crosspoint switches in each of the embodiments can be configured in
the various alternatives discussed above.
[0038] Each of the outputs of the crosspoint switch 140 is coupled
to a corresponding input to a band translation section 150. The
band translation section 150 can represent an integrated device
that is configured to independently provide frequency band
translation to signals at each of its inputs. Alternatively, the
band translation section 150 can represent a collection of one or
more band translation devices that are configured to frequency band
translate signals at each of the inputs. In one embodiment, the
band translation section 150 can include one or more band
translation devices configured to frequency band translate one or
more signals using a common local oscillator. In another
embodiment, the band translation section can include one or more
band translation devices configured to independently frequency band
translate each of the input signals.
[0039] In one embodiment, a band translation device within the band
translation section 150 has an input connected to an output of the
crosspoint switch 140. An output of the band translation device
represents an output of the band translation section 150. The band
translation device can be configured to selectively couple an input
signal directly to the output with no frequency translation, or
alternatively to frequency translate the input signal to an output
signal at a frequency band that differs from the input frequency
band. The frequency translation device can further be configured,
such that when frequency translation is selected, to selectively
frequency translate the input signal from a first one of the
predetermined frequency bands to a second one of the predetermined
frequency bands.
[0040] In the satellite television embodiment described above,
there are two predetermined frequency bands. A first predetermined
frequency band spans 950-1450 MHz and the second predetermined
frequency band spans 1650-2150 MHz. In this embodiment, a band
translation device can frequency translate an input signal at one
of the two predetermined frequency bands to an output signal at one
of the same two predetermined frequency bands. It can be seen that
there are four distinct possibilities. An input signal in the lower
of the two predetermined frequency bands, 950-1450 MHz, can be
frequency translated by the band translation device to either the
lower, or the upper, of the two predetermined frequency bands.
Thus, in the example, the signal output from the band translation
device can be in the lower predetermined frequency band, 950-1450
MHz, or the upper predetermined frequency band, 1650-2150 MHz. Of
course, in one of the conditions, there is no frequency
translation, but rather, the input signal is coupled directly from
the input of the band translation device to the output of the band
translation device. The direct coupling from input to output
without frequency translation can be referred to as a pass through
state.
[0041] Similarly, an input signal provided to the band translation
device at the upper frequency band can be output from the band
translation device at the upper frequency band or the lower
frequency band. In one state the band translation device is
configured in pass through and in the other state the frequency
translation device is configured to frequency translate the input
signal.
[0042] The band translation section 150 can be configured to
combine the outputs from one or more band translation section.
Alternatively, external components (not shown) can combine one or
more band translation device outputs.
[0043] Thus, a receiver 180 can implement the LNB's 130a-130c, the
crosspoint switch 140, and the band translation section 150. The
receiver 180 can implement all of these elements in a single
integrated circuit or can implement one or more of the elements on
separate integrated circuits or stand-alone devices. For example,
the LNB's 130a-130c can each be implemented as stand-alone devices
and the crosspoint switch 140 with the band translation section 150
can be implemented on a single integrated circuit. The LNB's
130a-130c, crosspoint switch 140 and band translation section 150
can be implemented in a single housing. This arrangement can be
particularly advantageous where size of the components is of
concern. Additionally, combining the crosspoint switch 140 with the
band translation section 150 onto a single integrated circuit can
greatly reduce the power requirements over a discrete
configuration. Reducing the power requirements can result in
additional advantages. For example, an integrated circuit
crosspoint switch 140 and band translation section 150 having
reduced power requirements may allow a system with a smaller power
supply. Additionally, reduced power consumption typically
corresponds to reduced heat dissipation. A system having reduced
heat dissipation requirements can often use smaller heatsinks or
may eliminate heatsinks. The use of smaller heatsinks can further
reduce the size of the system. Additionally, an integrated circuit
embodiment can advantageously have reduced cost as compared to a
discrete system. The cost savings can be attributable to savings in
components and materials that can be minimized or eliminated when
the crosspoint switch 140 and band translation section 150 are
configured as an integrated circuit.
[0044] In another receiver 180 embodiment, portions of the
crosspoint switch 140 and portions of the band translation section
150 can be implemented on separate integrated circuits and one of
the integrated circuits can be packaged within a LNB, for example
130a. In still another receiver 180 embodiment, the LNBs 130a-130c
can be housed in a device that is remote from the crosspoint switch
140 and band translation section 150.
[0045] The outputs of the band translation section 150, and thus,
the outputs of the receiver 180, are coupled to corresponding
inputs of set top boxes 160a-160c. In the embodiment described, the
predetermined frequency bands do not correspond to typical
television receiver bands. Thus, the set top boxes 160a-160c can
further frequency translate the signals to television receiver
operating bands. Additionally, the output signals from the band
translation section 150 can be in a format that is not compatible
with standard television receivers 170a-170c. The set top boxes
160a-160c can then function as signal processing stages. For
example, the satellite downlink signals can be digitally modulated
in a format that is not compatible with a typical television
receiver 170a-170c. The set top boxes 160a-160c can be configured
to demodulate the digitally modulated signals, process the
demodulated signals, and then modulate a television channel carrier
frequencies with the signals for delivery to television receivers
170a-170c.
[0046] Alternatively, if the signals output from the band
translation section 150 are in a format and are at a frequency band
that is compatible with television receivers 170a-170c, the set top
boxes 160a-160c may not be required. In still another alternative,
one or more of the functions performed by the set top boxes
160a-160c can be integrated into the television receivers
170a-170c.
[0047] In the embodiment described in FIG. 1 and in the embodiments
described in the other figures, each of the television receivers
170a-170c can be connected to an output from one of the set top
boxes 160a-160c. Each of the set top boxes 160a-160c can have one
or more individually programmable outputs. However, more than one
television receiver 170a-170c can be connected to an output from a
single set top box, for example 160a. Alternatively, outputs from
more than one set top box 160a-160c, or multiple outputs from one
set top box such as 160a, can be combined or otherwise connected to
a single television receiver, for example 170a, although such a
configuration is not typical. A television receiver, for example
170a, can be configured to tune to a particular channel within the
one or more frequency bands provided by the set top box, such as
160a. The television receiver 170a can process the signal from the
selected channel to present some media content, such as video or
audio, to the user.
[0048] A user is typically provided control, such as through a
remote control for the television 170a or set top box 160a, to
selectively configure the crosspoint switch 140 or band translation
section 150. For example, a user can be allowed to select, using a
remote control configured to operate with the set top box 160a, to
receive signals from two distinct satellite transponder groups.
[0049] One of the satellite transponder groups can be received and
frequency converted to a common IF band using the first LNB 130a.
The first LNB 130a can be configured to frequency convert the
signals to the upper IF band, 1650-2150 MHz. The second of the
satellite transponder groups can be received and frequency
converted to a common IF band using the Nth LNB 130c. The Nth LNB
130c can also be configured to frequency convert the signals to the
upper IF band, 1650-2150 MHz. The LNB's of the other embodiments
can be similarly configured. Thus, the block converted signals from
the two transponder groups would ordinarily not be combinable if
any two channels in the two transponder groups share signal
bandwidths in the common IF bands.
[0050] However, in this example, the crosspoint switch 140 can be
configured by control signals to output the signals from the first
LNB 130a to a first crosspoint switch output and to output the
signals from the Nth LNB 130c to a second crosspoint switch output.
The band translation section 150 can then be configured, using the
control signals provided by the set top box 160a, to pass frequency
translate the signals from the first switch output from the upper
IF band to the lower IF band. The band translation section 150 can
also be configured to pass through the signals from the second
switch output without frequency translation. A combiner within the
band translation section can be configured to combine the output
signals from the first and second band translation outputs. The
composite signal then includes the signals from the first
transponder group, located at the upper common IF band, and the
signals from the second transponder group, located at the lower
common IF band.
[0051] Thus, the example can be generalized to allow signals from
any N signal sources, which can be satellite transponder groups, to
be combined to M distinct band stacked signals. The band stacked
signals can each include from one to M distinct frequency bands.
Each of the band stacked signals can then be delivered to a set top
box, multiple set top boxes, or one or more other receivers for
presentation to one or more users.
[0052] For example, an output from a first output of the receiver
180 can be coupled to one or more set top boxes, for example 160a
and 160b. Alternatively, multiple receiver 180 outputs that have
information in mutually exclusive bands can be power combined and
coupled to a single cable or distribution system for delivering the
signal to one or more set top boxes or receivers. In still another
embodiment, the crosspoint switch 140 may direct the same input
signal to two separate inputs of the band translation section 150.
The band translation section 150 may then frequency translate a
portion of the input to a first frequency band and may also
frequency translate a second portion of the input signal to a
second frequency band. The two frequency bands can be combined into
a signal that is directed to a single cable or distribution system.
In still other embodiments, two separate LNB's with their own
crosspoint switch with band translation section 150 having output
signals in separate frequency bands can have their signals power
combined at the LNB outside the house. In some embodiments, the
LNBs 130a-130c, crosspoint switch 140 and band translation section
150 are implemented as a single device that may be placed, for
example, at the antenna 120. In other embodiments, the LNBs
130a-130c may be implemented in a first device and the crosspoint
switch 140 and band translation section can be implemented as one
or more devices that can be located locally or remotely from the
LNBs.
[0053] The LNB's 130a-130c, crosspoint switch 140, band translation
section 150, and set top boxes 160a-160c can be assembled in many
different configurations. In each configuration, multiple
independent users can each select different channels from one or
more independent signals without affecting other users or
devices.
[0054] FIG. 2 is a functional block diagram of a crosspoint switch
with band translation 200. A two input and two output version of
the receiver 180 of FIG. 1 can be implemented with the crosspoint
switch with band translation 200 of FIG. 2 in combination with two
LNB's. For example, the receiver of FIG. 1 can include LNB modules
connected to an integrated circuit implementation of the crosspoint
switch with band translation 200. This configuration of a receiver
allows signal routing and band translation to be performed at a
location physically close to the LNBs. The physical proximity of
LNBs to the crosspoint switch with band translation 200 minimizes
the loss and induced noise experienced by the received signals.
[0055] The crosspoint switch with band translation 200 is not
limited to having only two inputs and two outputs. Other
embodiments of the crosspoint switch with band translation 200 can
include additional inputs and outputs. The number of inputs can be
generalized to any number, N. The number of inputs, N, can be, for
example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or
some other number. Similarly, the number of outputs can be
generalized to any number, M. The number of outputs, M, can be, for
example, 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30,
32, or some other number.
[0056] Additionally, the crosspoint switch with band translation
200 can be located remote from a signal source, such as an antenna
or LNB modules. For example, one or more coaxial cables can couple
the outputs from LNB modules to inputs of the crosspoint switch
with band translation 200. In an example environment such as signal
distribution within a residence, the LNB modules can be a distance
of more than 250 feet away from the crosspoint switch and can
couple to the LNB modules with coaxial cables.
[0057] The crosspoint switch with band translation 200 can be
configured using differential signal interconnections to improve
signal isolation. The device can be implemented with single ended
signal interconnections but differential signal interconnections
typically provide greater isolation. Signal isolation is of greater
concern when the device is implemented in a single integrated
circuit.
[0058] The crosspoint switch with band translation 200 has a first
signal path and a second signal path. The first signal path
includes a first low noise amplifier (LNA) 210a connected to an
arrangement of switches, 222a, 224a, 226a, and 228a, that can
selectively route a signal at the output 214a of the LNA 210a to a
first band translation device 230a or a second band translation
device 230b. The crosspoint switch with band translation 200 of
FIG. 2 is configured to provide voltage-mode switching of the
signals.
[0059] The first LNA 210a is configured with a differential input
212a and a differential output 214a. The differential input 212a of
the first LNA 210a can be, for example, matched to 75 ohm
differential. The differential output 214a of the first LNA 210a is
configured to have a low impedance. The crosspoint switch with band
translation 200 maximizes signal isolation and minimizes switching
transients by connecting a high isolation switch configuration to
the output of the first LNA 210a. Band translation devices 230a,
230b having high input impedances are connected to the outputs of
the switch configuration.
[0060] In one embodiment, a low output impedance refers to a
typical magnitude less than 10 ohms differential. In other
embodiments, low impedances may refer to other impedance magnitudes
that may be higher or lower than 10 ohms, and need not be defined
differentially. For example, a low impedance can refer to a
magnitude of substantially less than 33 ohms. In another
embodiment, a high impedance refers to a magnitude of typically
greater than 1 kohm differential. In other embodiments, high
impedances may refer to other impedance magnitudes that may be
higher or lower than 1 kohm, and need not be defined
differentially. For example, in another embodiment, high impedance
can refer to a magnitude of typically greater than 330 ohms. In
general the terms low impedance and high impedance are defined
relative to one another. That is, high impedance is defined to be
greater than or equal to approximately ten times the low impedance
value. Thus, for a low impedance value of 33 ohms, a high impedance
value is greater than approximately 330 ohms.
[0061] The in-phase output of the first LNA 210a is connected to
switches 222a and 224a that selectively switch the signal to the
in-phase inputs of the band translation devices 230a, 230b based on
switch control signals provided by, for example, the controller in
the set top box 160a of FIG. 1. In an alternative embodiment, a
microprocessor local to, or integrated with the crosspoint switch
with band translation 200 can process signals, such as one or more
control messages, from an associated set top box or receiver. The
inverted phase output of the first LNA 210a is connected to
switches 226a, 228a that selectively switch the signal to the
inverted inputs of the band translation devices 230a, 230b. A
switch connected to the in-phase output, for example 222a, is
typically paired with a switch on the inverted output, for example
226a, such that a differential signal is selectively connected by
the switch pair 222a, 226a.
[0062] Thus, the controller in the set top box can direct a first
switch pair 226a, 226a to selectively connect the differential
output of the first LNA 210a to the differential input of the first
band translation device 230a. A second switch pair 224a, 228a
selectively connects the differential output of the first LNA 210a
to the second band translation device 230b.
[0063] The first band translation device 230a can selectively
frequency translate the signal at its input to an output frequency
band. The first band translation device 230a uses a signal from a
first Local Oscillator (LO) 240a to perform the frequency
translation.
[0064] A second signal path is configured similar to the first
signal path. A second LNA 210b has a differential input 212b and a
differential output 214b. The signal at the differential output
214b of the second LNA 210b is selectively connected to the first
band translation device 230a using a third switch pair 222b, 226b.
The signal at the differential output 214b of the second LNA 210b
is selectively connected to the second band translation device 230b
using a fourth switch pair 224b, 228b.
[0065] Typically, the signals from the first LNA 210a and the
second LNA 210b are not switched to the same band translation
device, for example 230a. The output of a single LNA 210a can be
switched to both band translation devices 230a, 230b while the
other LNA signal is not provided to any of the band translation
devices 230a, 230b.
[0066] The crosspoint switch with band translation 200 is
configured to provide high signal isolation between the input
signals and the output signals from the LNA's 210a and 210b, and
high isolation through the crosspoint switch section 222a-228b.
Additionally, the crosspoint switch with band translation 200
provides high signal isolation at the input and output of the band
translation devices 230a and 230b. Additionally, the crosspoint
switch with band translation 200 has high signal isolation and low
switching transients. Low switching transients are achieved through
the use of low impedance at the LNA outputs combined with high
impedance inputs at the band translation devices 230a, 230b. High
signal isolation is achieved using differential signal
configuration and is also achieved through the use of high
isolation switches.
[0067] High signal isolation typically refers to greater than 30 dB
of isolation. It may be advantageous to achieve a high signal
isolation that is greater than approximately 40 dB. In general,
high signal isolation can refer to greater than 20 dB, 25 dB, 30
dB, 35 dB, 40 dB, 45 dB, 50 dB or some other greater level of
isolation.
[0068] FIGS. 3A-3D are embodiments of high isolation switches. Each
of the switch embodiments of FIGS. 3A-3D are single-ended
configurations. The switch embodiments can be duplicated to allow
switching of in-phase and inverted signals of differential signals.
Thus, a pair of switches from FIGS. 3A-3D can be used as the switch
pairs of FIG. 2.
[0069] FIG. 3A is a first switch embodiment having a single
transistor 302 controlled to selectively connect a signal from its
input to its output based on the signal applied to the control
input. The transistor 302 can be controlled to selectively isolate
a signal at its input from its output based on the signal applied
to its control input. Signal isolation is controlled by the ability
of the transistor 302 to isolate the input from the output. A pair
of transistors 302 can be used to switch differential signals.
[0070] FIG. 3B is a second switch embodiment. A signal is input at
the base of a first transistor 310 configured as an emitter
follower. Additionally, a bias voltage, which is typically a DC
bias voltage, is applied to the base of the first transistor 310.
The emitter of the first transistor 310 is selectively biased with
a controllable current source 312. The first transistor 310
selectively couples a signal from its base to its emitter when the
controllable current source 312 conducts. Conversely, a signal at
the base of the first transistor 310 is isolated from the emitter
when the controllable current source 312 is off. A pull up device
314 connects the emitter of the first transistor 310 to a voltage
that is greater than the bias voltage, for example (V.sub.b+1V) to
ensure the first transistor 310 is cut off when the controllable
current source 312 is off.
[0071] FIG. 3C is a third switch embodiment having multiple
transistors configured to provide increased signal isolation. A
signal is provided to a first transistor 320. The output of the
first transistor 320 is connected to an input of a second
transistor 322. The output of the second transistor 322 is the
output of the switch. A third transistor 324 is connected to the
output of the first transistor 320 and is configured to selectively
couple the output of the first transistor 320 and input of the
second transistor 322 to ground or signal return.
[0072] A differential control signal is used to control the third
switch embodiment. An in-phase control signal controls the first
transistor 320 and second transistor 322. An inverted control
signal controls the third transistor 324. Thus, when the first and
second transistors 320, 322 are controlled to be conducting, the
third transistor 324 is controlled to be cut off. Conversely, when
the first and second transistors 320, 322 are controlled to be cut
off, the third transistor 324 is controlled to be conducting.
[0073] FIG. 3D is a fourth switch embodiment. The fourth switch
embodiment is similar to the second switch embodiment with
additional transistors configured to provide additional signal
isolation.
[0074] A signal is input at the base of a first transistor 330
configured as an emitter follower. Additionally, a bias voltage,
V.sub.b, which is typically a DC bias voltage, is applied to the
base of the first transistor 330. The emitter of the first
transistor 330 is selectively biased with a controllable current
source 332. The first transistor 330 selectively couples a signal
from its base to its emitter when the controllable current source
332 conducts. Conversely, a signal at the base of the first
transistor 330 is isolated from the emitter when the controllable
current source 332 is off.
[0075] A second transistor 334 is configured to selectively pull up
the emitter of the first transistor 330 to a voltage that is
greater than the bias voltage, for example (V.sub.b+1V), to ensure
the first transistor 330 is cut off when the controllable current
source 332 is off. Additionally, the second transistor 334 can also
shunt any signal leakage at the emitter node to AC ground via the
bias point, thus improving signal isolation. A third transistor 336
has an input connected to the emitter of the first transistor 330
and an output that is the output of the switch. The third
transistor 336 is selectively controlled to couple the signal from
the emitter of the first transistor 330 to the switch output when
the controllable current source 332 is conducting. The third
transistor 336 is selectively controlled to isolate the signal from
the emitter of the first transistor 330 when the controllable
current source is off.
[0076] FIG. 4 is a functional block diagram of a crosspoint switch
with band translation 400 that can also be integrated as a portion
of the receiver 180 of FIG. 1. A two input and two output version
of the receiver 180 of FIG. 1 can be implemented with the
crosspoint switch with band translation 400 of FIG. 4 in
combination with two LNB's.
[0077] The crosspoint switch with band translation 400 is similar
to the crosspoint switch with band translation 200 of FIG. 2 with
the exception that the device of FIG. 4 uses current mode switching
while the device of FIG. 2 uses voltage mode switching. Thus, the
crosspoint switch with band translation 400 can be used
interchangeably with the device of FIG. 2. However, in some
instances, current mode switching can be advantageous because of
the ability to sum currents into a common node.
[0078] The crosspoint switch with band translation 400 has a first
signal path and a second signal path. The first signal path
includes a first LNA 410a connected to a pair of transconductance
devices, 422a and 424a that can selectively route a signal at the
output 414a of the LNA 410a to a first band translation device 430a
or a second band translation device 430b. The crosspoint switch
with band translation 400 uses the transconductance devices, for
example 422a and 422b, to provide current-mode switching of the
signals.
[0079] The first LNA 410a is configured with a differential input
412a and a differential output 414a. The differential input 412a of
the first LNA 410a can be matched to 75 ohm differential. The
differential output 414a of the first LNA 410a is configured to
have a low impedance. The crosspoint switch with band translation
400 maximizes signal isolation and minimizes switching transients
by connecting high isolation transconductance devices, 422a and
424a, to the output of the first LNA 410a. Band translation devices
430a, 430b having low input impedances are connected to the outputs
of the transconductance devices 422a and 424a.
[0080] The differential output 414a of the first LNA 410a is
connected to the high impedance differential inputs of the
transconductance devices 422a and 424a. The first LNA 410a can
drive both transconductance devices 422a and 424a because the
differential inputs of the transconductance devices 422a and 424a
are high impedance.
[0081] Each of the transconductance devices 422a and 424a includes
a control input, 423a and 425a respectively, that is used to switch
the transconductance device 422a and 424a on or off. When the
signal from the first LNA 410a is to be routed to the first band
translation device 430a, the first transconductance device 422a is
controlled to provide a current output to the input of the first
and translation device 430a. Similarly, the second transconductance
device 424a can be controlled to provide a current output to the
input of the second band translation device 430b. One or more
transconductance devices, for example 422a and 424a connected to an
LNA 410a can simultaneously be enabled such that one input, for
example a signal at 412a, can be routed to all band translation
devices 430a and 430b.
[0082] The first band translation device 430a can selectively
frequency translate the signal at its input to an output frequency
band. The first band translation device 430a uses a signal from a
first LO 440a to perform the frequency translation. The first band
translation device 430a has a low impedance input and thus,
operates as a current summing node for the currents from the
transconductance devices 422a and 422b to which its input is
connected.
[0083] A second signal path is configured similar to the first
signal path. A second LNA 410b has a differential input 412b and a
differential output 414b. The signal at the differential output
414b of the second LNA 410b is selectively connected to the first
band translation device 430a using a third transconductance device
422b. The signal at the differential output 414b of the second LNA
410b is selectively connected to the second band translation device
230b using a fourth transconductance device 424b. The second band
translation device 430b operates in conjunction with a second LO
440b.
[0084] The transconductance devices 422a, 422b, 424a, and 424b can
be any type of transconductance devices, such as transistors, FETs,
and the like. The transconductance devices 422a, 422b, 424a, and
424b have a high output impedance. Thus, multiple transconductance
devices, for example 422a and 422b can selectively provide a signal
to the same band translation device 430a without the output
impedance of the first transconductance device 422a affecting the
performance of the other transconductance device 422b. The low
input impedance band translation device 430a operates as a current
summing node.
[0085] In an alternative embodiment of the crosspoint switch with
band translation 400, the LNA's 410a and 410b are omitted and the
input signals are directly coupled to the inputs of the
transconductance devices 422a, 422b, 424a, and 424b. The inputs to
the first and second signal paths can be matched to a predetermined
impedance using a matching circuit (not shown) which can be as
simple as a resistor placed across the differential inputs.
[0086] FIG. 5 is a functional block diagram of a crosspoint switch
with band translation 500 having LNA/band translation device pairs
for each input/output combination and summing the outputs of the
band translation devices in the current domain. As with the
crosspoint switch with band translation devices of FIGS. 2 and 4,
the crosspoint switch with band translation 500 can be combined
with LNBs in the receiver 180 of FIG. 1. The devices in the
crosspoint switch with band translation 500 utilize differential
signals to minimize noise, but single-ended devices can be used in
other embodiments.
[0087] Each LNA/band translation pair can selectively provide a
signal to an output or be controlled to isolate the signal at the
input from the output. The LNA can be selectively controlled to
isolate the signal by removing the bias, or by reversing the bias
on the amplifier. For example, the controller in the set top box
160a of FIG. 1 can receive user input and control the bias control
pins, labeled A, B, C, and D, to selectively enable or disable the
bias to the LNAs 510a-b, 520a-b.
[0088] A first LNA/band translation device pair includes a first
LNA 510a connected to a first input 512a. The first LNA 510a is
controlled to selectively amplify or isolate the input signal based
on a signal provided to its control input 514a. The output of the
first LNA 510a is connected to a first band translation device 532
having a high output impedance. The output of the first band
translation device 532 is connected to a first signal output
540a.
[0089] A second LNA/band translation device pair includes a second
LNA 520a having an input connected to the first input 512a. The
controller in the set top box can control the control input 524a of
the second LNA 520a to selectively amplify or isolate the input
signal. The output of the second LNA 520a is connected to a second
band translation device 534 having a high output impedance. The
output of the second band translation device 534 is connected to a
second signal output 540b.
[0090] Thus, in order to selectively route a signal from the first
input 512a to the first signal output 540a, the controller in the
set top box selectively controls the first LNA 510a to amplify the
input signal by providing an enable signal to the control input,
514a, on the first LNA 510a. In order to isolate a signal at the
first input 512a from the first output 540a, the first LNA 510a is
selectively controlled to isolate the signal.
[0091] A second differential input 512b is connected to the inputs
of a third LNA 510b and a fourth LNA 520b. The third LNA 510b is
controlled to selectively amplify or isolate the input signal based
on a signal provided to its control input 514b. The output of the
third LNA 510b is connected to a third band translation device 536
having a high output impedance. The output of the third band
translation device 536 is connected to a first signal output
540a.
[0092] Similarly, the fourth LNA 520b is controlled to selectively
amplify or isolate the input signal based on a signal provided to
its control input 524b. The output of the fourth LNA 520b is
connected to a fourth band translation device 538 having a high
output impedance. The output of the fourth band translation device
538 is connected to a first signal output 540b.
[0093] Thus, a signal provided to the second differential input
512b can selectively be routed to the first or second signal
outputs, 540a or 540b or simultaneously to both signal outputs. In
order to route the signal from the second input 512b to the first
signal output 540a, a control signal is provided to the control
input 514b of the third LNA 510b to enable the third LNA 510b to
amplify the second input signal. In order to route the signal from
the second input 512b to the second signal output 540b, a control
signal is provided to the control input 524b of the fourth LNA 520b
to enable the fourth LNA 520b to amplify the second input
signal.
[0094] The outputs of the first and third band translation devices
532, 536 can be summed at the load if both signals are routed to
the first signal output 540a. Similarly, the outputs of the second
and fourth band translation devices 534 and 538 can be summed at
the load if both provide signals to the second signal output 540b.
Thus, by using current outputs from high impedance devices driving
matched impedance loads, multiple signals can be summed in a common
node.
[0095] FIG. 6 is another embodiment of a 2.times.2 crosspoint
switch with band translation 600. The specific embodiment is
optimized for implementation within a single integrated circuit
having impedance matched inputs and outputs. It is evident that the
number of inputs or outputs can be expanded to any other number.
The embodiment uses current mode switching. LNA's having a matched
input, variable gain, and a low impedance output are used. Signals
at a first input 612a can be routed, using first and second
transconductance devices, to one or both outputs 670a and 670b.
Similarly, signals at a second input 612b can be routed, using
third and fourth transconductance devices, to one or both outputs
670a and 670b.
[0096] The 2.times.2 crosspoint switch with band translation 600
receives the input signal at a matched signal input of the low
noise amplifiers. The low noise amplifiers generate intermediate
signals at their low impedance outputs. The intermediate signals
are provided to high impedance inputs of current sources configured
as transconductance devices. A controller can selectively control
the transconductance devices to provide an output current based in
part on the intermediate signal. Additionally, the controller can
selectively enable or disable each of the transconductance devices.
For example, the bias to each of the transconductance device may be
controllable to selectively enable or disable the device.
Alternatively, the bias current may be varied linearly to control
the gain of the transconductance devices. Alternatively, the gain
may be varied via other means and the transconductor may be enabled
and disabled by other means.
[0097] The current output of the transconductance devices can then
be received at low impedance inputs of band translation devices
that can frequency translate the current signals from a first
frequency band to a second frequency band. The band translation
devices can have matched impedance outputs.
[0098] A first signal path is configured to amplify, band
translate, and route a first signal to one of two outputs. A first
LNA 610a has a differential input 612a configured to accept the
first signal. The input 612a of the first LNA 610a can be a
differential input that is matched to a predetermined impedance,
such as 75.OMEGA. or 50.OMEGA.. The differential output of the
first LNA 610a has an in-phase output 614a and an inverted output
616a. The differential output of the first LNA 610a can be a low
output impedance, a matched output impedance, or a high output
impedance. The output impedance of the first LNA 610a can be, for
example, 200 ohms differential.
[0099] The in-phase output 614a of the first LNA 610a is connected
to a first emitter follower 622a that has a low output impedance.
The in-phase output 614a of the first LNA is connected to the base
of the first emitter follower 622a. The emitter of the first
emitter follower 624a is connected to a current source 624a that
biases the first emitter follower 624a. The output of the first
emitter follower 624a is connected to the in-phase inputs of the
differential inputs to first and second transconductance devices.
The transconductance devices have high input impedances. The
transconductance devices can be bipolar devices that can be
selectively enabled or disabled by controlling the bias
currents.
[0100] Similarly, the inverted output 616a of the first LNA is
connected to the input of a second emitter follower 626a. The
second emitter follower 626a is biased using a current source 628a
connected to its emitter. The output of the second emitter follower
626a is connected to the inverted inputs of the first and second
transconductance devices.
[0101] Alternatively, the first and second emitter followers, 622a
and 626a, with their associated current sources, 624a and 628a, can
be considered the low impedance output stage of the first LNA
610a.
[0102] The first transconductance device includes a first
transistor 632a with the base of the first transistor 632a serving
as the in-phase input of the first transconductance device. A first
resistor 633a connects the emitter of the first transistor 632a to
a controllable current source 638a. The base of a second transistor
634a is used as the inverted input of the first transconductance
device. A second resistor 635a connects the emitter of the second
transistor 634a to the controllable current source 638a.
[0103] The controllable current source 638a provides the bias for
the transistors, 632a and 634a of the first transconductance
device. The controllable current source 638a can be selectively
enabled or disabled based on a control signal. The first
transconductance device isolates a signal at its input from its
output when the controllable current source 638a is disabled, and
conversely, provides a current output that can be proportional to
the input signal when the controllable current source 638a is
enabled.
[0104] A first differential buffer amplifier having two transistors
652a and 654a is used to sum the currents from multiple
transconductance devices and provide a differential signal to the
first band translation device 660a.
[0105] The first band translation device 660a is configured with a
low input impedance and an output impedance matched to a
predetermined impedance. For example, the output of the first band
translation device 660a can be matched to 75. The differential
output of the first band translation device 660a is connected to
the first signal output 670a. The first band translation device
660a is driven with a first LO 662a. The first LO 662a frequency
can be tunable to allow the frequency translation of the first band
translation device 662a to be tuned. Alternatively the output
frequency of the first LO 662a can be fixed. The first band
translation device 662a can be configured to frequency translate
the signal or to pass the signal without frequency translation.
[0106] The first LNA 610a also provides a signal that can be
selectively routed to a second output 670b. The differential
outputs from the first and second emitter followers, 622a and 626a
are connected to the differential inputs of a second
transconductance device.
[0107] The base of a first transistor 642a in the second
transconductance device is connected to the in-phase output from
the first emitter follower 622a. The base of a second transistor
644a in the second transconductance device is connected to the
inverted output from the second emitter follower 626a. Resistors
643a and 645a connect the emitters of the first and second
transistors 642a and 644a to a controllable current source 648a
that selectively provides bias to the first and second transistors
642a and 644a. The second transconductance device provides an
output current when the controllable current source 648a is
enabled. Conversely, the second transconductance device does not
provide an output current when the controllable current source 648a
is disabled.
[0108] The differential output from the second transconductance
device is connected to the differential input of a second
differential buffer amplifier. The second differential buffer
amplifier includes two transistors 652b and 654b and is used to sum
the currents from multiple transconductance devices and provide a
differential signal to the second band translation device 660b
.
[0109] The output of the second differential buffer amplifier is
connected to the differential input of a second band translation
device 660b. The second band translation device 660b has with a low
input impedance and an output impedance matched to a predetermined
impedance such as 75. The differential output of the second band
translation device 660b is connected to the second signal output
670b. The second band translation device 660b is driven with a
second LO 662b. The second LO 662b frequency can be tunable to
allow the frequency translation of the second band translation
device 662b to be tuned. Alternatively the output frequency of the
second LO 662b can be fixed. The second band translation device
662b can be configured to frequency translate the signal or to pass
the signal without frequency translation.
[0110] The second signal input 612b is connected to the second LNA
610b and through third and fourth transconductance devices to the
first and second differential buffer amplifiers in a configuration
that is similar to the path from the first signal input 612a to the
differential buffer amplifiers.
[0111] The second signal input 612b is connected to the input of
the second LNA 610b. The differential output of the second LNA is
connected to a pair of emitter followers, one emitter follower for
each of the signal outputs of the second LNA 610b.
[0112] The in-phase LNA output 614b is connected to a first emitter
follower 622b that includes a first current source 624b connected
to its emitter to provide a bias. The inverted LNA output 616b is
connected to a second emitter follower 626b that includes a second
current source 628b connected to its emitter to provide a bias.
[0113] The output of the first emitter follower 622b is connected
to the in-phase inputs of third and fourth transconductance
devices. The output of the second emitter follower 626b is
connected to the inverted inputs of the third and fourth
transconductance devices.
[0114] The third transconductance device includes first and second
transistors 632b and 634b arranged in a differential configuration.
The base of the first transistor 632b is the in-phase input of the
transconductance device and the base of the second transistor 634b
is the inverted input of the third transconductance device. The
emitters of the first and second transistors, 632b and 634b, are
connected via first and second resistors, 633b and 635b, to a
controllable current source 638b. The controllable current source
selectively enables or disables the third transconductance device.
The collectors of the first and second transistors, 632b and 634b,
are connected to the differential inputs of the first differential
buffer amplifier.
[0115] Similarly, the fourth transconductance device includes first
and second transistors 642b and 644b arranged in a differential
configuration. The base of the first transistor 642b is the
in-phase input of the transconductance device and the base of the
second transistor 644b is the inverted input of the fourth
transconductance device. The emitters of the first and second
transistors, 642b and 644b, are connected via first and second
resistors, 643b and 645b, to a controllable current source 648b.
The controllable current source 648b selectively enables or
disables the fourth transconductance device. The collectors of the
first and second transistors, 642b and 644b, are connected to the
differential inputs of the second differential buffer amplifier. Of
course, the transconductance devices shown in FIG. 6 only represent
embodiments of typical transconductance devices. Other embodiments
of transconductance devices may be used in other embodiments.
[0116] Thus, various crosspoint switch with band translation
devices have been disclosed. The devices can be implemented in
single integrated circuits and can be configured to switch any
number, N, of inputs to any number, M, outputs. The devices can be
configured to perform voltage mode switching of signals or current
mode switching of signals. One or more input signals can be routed
to the same signal output. Additionally, one input signal can be
routed to one or more signal outputs. Additionally, the device can
be configured to selectively perform frequency band translation of
the input signals. One or more of the crosspoint switch with band
translation devices can be combined with LNBs to provide a receiver
for a signal distribution system. Alternatively, the LNB63 s can be
remote from the crosspoint switch with band translation. The use of
crosspoint switch with band translation devices allows greater
flexibility in signal routing within the signal distribution
system.
[0117] The switch configuration provides input and output signal
isolation. The configuration of input and output impedances for the
intermediate stages of the crosspoint switch with band translation
ensures minimal switching transients. The configuration of input
and output impedances for the intermediate stages is based in part
on whether voltage mode or current mode switching is implemented. A
controllable current source can be used to selectively enable and
disable transconductance devices to enable switching of signals.
Differential signals can also be used to further minimize noise
induced onto the desired signals.
[0118] Electrical connections, couplings, and connections have been
described with respect to various devices or elements. The
connections and couplings can be direct or indirect. A connection
between a first and second device can be a direct connection or can
be an indirect connection. An indirect connection can include
interposed elements that can process the signals from the first
device to the second device.
[0119] Those of skill in the art will understand that information
and signals can be represented using any of a variety of different
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips that can
be referenced throughout the above description can be represented
by voltages, currents, electromagnetic waves, magnetic fields or
particles, optical fields or particles, or any combination
thereof.
[0120] Those of skill will further appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the embodiments disclosed herein can
be implemented as electronic hardware, computer software, or
combinations of both. To clearly illustrate this interchangeability
of hardware and software, various illustrative components, blocks,
modules, circuits, and steps have been described above generally in
terms of their functionality. Whether such functionality is
implemented as hardware or software depends upon the particular
application and design constraints imposed on the overall system.
Skilled persons can implement the described functionality in
varying ways for each particular application, but such
implementation decisions should not be interpreted as causing a
departure from the scope of the present invention.
[0121] The various illustrative logical blocks, modules, and
circuits described in connection with the embodiments disclosed
herein can be implemented or performed with a general purpose
processor, a digital signal processor (DSP), an application
specific integrated circuit (ASIC), a field programmable gate array
(FPGA) or other programmable logic device, discrete gate or
transistor logic, discrete hardware components, or any combination
thereof designed to perform the functions described herein. A
general-purpose processor can be a microprocessor, but in the
alternative, the processor can be any processor, controller,
microcontroller, or state machine. A processor can also be
implemented as a combination of computing devices, for example, a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0122] The steps of a method or algorithm described in connection
with the embodiments disclosed herein can be embodied directly in
hardware, in a software module executed by a processor, or in a
combination of the two. A software module can reside in RAM memory,
flash memory, ROM memory, EPROM memory, EEPROM memory, registers,
hard disk, a removable disk, a CD-ROM, or any other form of storage
medium. An exemplary storage medium can be coupled to the processor
such the processor can read information from, and write information
to, the storage medium. In the alternative, the storage medium can
be integral to the processor. The processor and the storage medium
can reside in an ASIC.
[0123] The above description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
invention. Various modifications to these embodiments will be
readily apparent to those skilled in the art, and the generic
principles defined herein can be applied to other embodiments
without departing from the spirit or scope of the invention. Thus,
the invention is not intended to be limited to the embodiments
shown herein but is to be accorded the widest scope consistent with
the principles and novel features disclosed herein.
* * * * *