U.S. patent application number 15/086248 was filed with the patent office on 2017-10-05 for fully flexible multi-tuner front end architecture for a receiver.
The applicant listed for this patent is Silicon Laboratories Inc.. Invention is credited to Russell Croman, Michael Johnson, Dan B. Kasha, Michael R. May, Nebojsa Stanic.
Application Number | 20170288764 15/086248 |
Document ID | / |
Family ID | 59885842 |
Filed Date | 2017-10-05 |
United States Patent
Application |
20170288764 |
Kind Code |
A1 |
Croman; Russell ; et
al. |
October 5, 2017 |
FULLY FLEXIBLE MULTI-TUNER FRONT END ARCHITECTURE FOR A
RECEIVER
Abstract
In an example, a method includes: in a first mode, causing a
first tuner of an entertainment system to receive and process a
first RF signal from a first antenna configured for a first band to
output a first audio signal of a first radio station and causing a
second tuner of the entertainment system to receive a second RF
signal from a second antenna configured for the first band to
determine signal quality metrics for one or more radio stations of
the first band; in a second mode, causing the first tuner to output
a first signal representation of the first RF signal and causing
the second tuner to receive and process the second RF signal to
output a second signal representation of the second RF signal; and
causing a phase diversity combining circuit to process the first
and second signal representations to output an audio signal of the
first radio station, without disruption of output from the
entertainment system of a broadcast of the first radio station.
Inventors: |
Croman; Russell; (Buda,
TX) ; Stanic; Nebojsa; (Austin, TX) ; Johnson;
Michael; (Austin, TX) ; Kasha; Dan B.;
(Seattle, WA) ; May; Michael R.; (Austin,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Silicon Laboratories Inc. |
Austin |
TX |
US |
|
|
Family ID: |
59885842 |
Appl. No.: |
15/086248 |
Filed: |
March 31, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 7/08 20130101; H04B
1/0064 20130101; H04B 1/16 20130101; H04B 1/0075 20130101 |
International
Class: |
H04B 7/08 20060101
H04B007/08; H04B 1/16 20060101 H04B001/16; H04B 1/00 20060101
H04B001/00 |
Claims
1. An apparatus comprising: a first low noise amplifier (LNA) to
receive and amplify a first radio frequency (RF) signal of a first
band, received from a first antenna; a first tuner having a first
plurality of mixers including a first mixer to selectively be
coupled to the first LNA to receive and downconvert the first RF
signal received from the first LNA to a first downconverted signal,
the first tuner to process the first downconverted signal; a second
LNA to receive and amplify a second RF signal of a second band,
received from a second antenna; and a second tuner having a second
plurality of mixers including a second mixer to selectively be
coupled to the second LNA to receive and downconvert the second RF
signal received from the second LNA to a second downconverted
signal and a first mixer to selectively be coupled to the first LNA
to receive and downconvert the first RF signal received from the
first antenna to a third downconverted signal, the second tuner
controllable to process a selected one of the second downconverted
signal and the third downconverted signal provided by a selected
one of the second mixer and the first mixer of the second
tuner.
2. The apparatus of claim 1, wherein in a first mode of operation,
the first LNA is coupled to provide the first RF signal to the
first tuner and to the second tuner simultaneously.
3. The apparatus of claim 2, further comprising a third LNA to
receive and amplify a third RF signal of the first band, received
from a third antenna, the third LNA coupled to provide the third RF
signal to the second tuner to enable phase diversity reception of
the first band in a second mode.
4. The apparatus of claim 3, wherein the apparatus further
comprises an audio processor and a phase diversity combining
circuit to seamlessly transition from the first mode to the second
mode without audible impact to an audio signal output from the
apparatus.
5. The apparatus of claim 1, wherein the first plurality of mixers
further includes a second mixer to selectively be coupled to the
second LNA to receive and downconvert the second RF signal to a
fourth downconverted signal.
6. The apparatus of claim 1, further comprising a first
loop-through buffer coupled to an output of the first LNA to
receive the first RF signal and output the first RF signal to a
second receiver coupled to the apparatus, the apparatus comprising
a first receiver.
7. The apparatus of claim 6, further comprising a second
loop-through buffer coupled to an output of the second LNA to
receive the second RF signal and output the second RF signal to the
second receiver.
8. The apparatus of claim 7, further comprising a selector coupled
to an output of the first loop-through buffer and an output of the
second loop-through buffer and controllable to output a selected
one of the first RF signal and the second RF signal to the second
receiver.
9. The apparatus of claim 1, wherein the first tuner comprises a
multiplexer coupled to an output of the first plurality of mixers,
the multiplexer controllable to provide an output of one of the
first plurality of mixers to a signal processing path of the first
tuner.
10. The apparatus of claim 1, wherein the first tuner comprises a
first frequency generator to operate at a first frequency and the
second tuner comprises a second frequency generator to operate at a
second frequency substantially different than the first frequency
when the first tuner and the second tuner are to operate in a first
band.
11. The apparatus of claim 10, further comprising a filter coupled
to an output of the first LNA to provide a notch response to reduce
coupling from the second frequency generator.
12. The apparatus of claim 10, wherein the first LNA, the first
tuner, the second LNA and the second tuner are configured on a
first semiconductor die.
13. A non-transitory computer readable medium including
instructions that when executed enable an entertainment system to:
in a first mode, cause a first tuner of the entertainment system to
receive and process a first radio frequency (RF) signal from a
first antenna configured for a first band to output a first audio
signal of a first radio station and cause a second tuner of the
entertainment system to receive a second RF signal from a second
antenna configured for the first band to determine signal quality
metrics for one or more radio stations of the first band; in a
second mode, cause the first tuner to output a first signal
representation of the first RF signal and cause the second tuner to
receive and process the second RF signal from the second antenna to
output a second signal representation of the second RF signal;
cause a phase diversity combining circuit to process the first and
second signal representations to output an audio signal of the
first radio station, while a broadcast of the first radio station
is output from the entertainment system; and in a third mode, cause
the first tuner to receive and process the first RF signal from the
first antenna to generate a first audio signal of the first radio
station, and cause the second tuner to receive and process the
second RF signal from the second antenna to generate a second audio
signal of a second radio station, and cause a linker circuit to
transition from the first audio signal to the second audio signal,
the linker circuit to output a final audio signal without
impairments due to the transition.
14. (canceled)
15. A system comprising: a first integrated circuit (IC) including
a first tuner and a second tuner, the first IC including: a first
pad to receive a first radio frequency (RF) signal from a first
frequency modulation (FM) antenna and symmetrically output the
first RF signal to the first tuner and the second tuner, and to a
first loop-through buffer to provide the first RF signal to a
second IC; a second pad to receive a second RF signal from a second
FM antenna and symmetrically output the second RF signal to the
first tuner and the second tuner, and to a second loop-through
buffer to provide the second RF signal to the second IC; the first
tuner having a first plurality of mixers including a first mixer to
receive and downconvert the first RF signal to a first
downconverted signal, a second mixer to receive and downconvert the
second RF signal to a second downconverted signal, and a first
signal processing path to process a selected one of the first
downconverted signal and the second downconverted signal; the
second tuner having a second plurality of mixers including a second
mixer to receive and downconvert the second RF signal to a fourth
downconverted signal, a first mixer to receive and downconvert the
first RF signal to a third downconverted signal, and a second
signal processing path dynamically controllable to process a
selected one of the third downconverted signal and the fourth
downconverted signal; and a microcontroller to dynamically control
transitions of the first tuner and the second tuner between a
plurality of operating modes while a first audio signal is output
by at least one of the first and second tuners; and the first and
second antennas coupled to the first IC.
16. The system of claim 15, wherein the plurality of operating
modes includes a single tuner reception mode, a dual tuner
reception mode, a phase diversity reception mode, and a seamless
linking reception mode.
17. The system of claim 15, wherein in a first operating mode, the
first tuner is to output the first downconverted signal of a first
radio station obtained via the first RF signal, the second tuner is
to output a second downconverted signal of the first radio station
obtained via the second RF signal received from the second antenna,
and a phase diversity circuit is to combine the first downconverted
signal and the second downconverted signal to produce an audio
output signal
18. The system of claim 17, wherein in a second operating mode, the
first tuner is to output the first audio signal of the first radio
station obtained via the first RF signal, and the second tuner is
to output one or more signal quality metrics of one or more other
radio stations.
19. The system of claim 15, wherein the first tuner comprises a
first frequency generator to operate at a first frequency and the
second tuner comprises a second frequency generator to operate at a
second frequency substantially different than the first frequency
when the first tuner and the second tuner are to operate at a first
band, the first frequency generator coupled to a first local
oscillator coupled to the first plurality of mixers and the second
frequency generator coupled to a second local oscillator coupled to
the second plurality of mixers.
20. The system of claim 18, wherein the IC further comprises a
first low noise amplifier (LNA) coupled to the first pad to receive
and amplify the first RF signal, the first LNA comprising a buffer
to buffer the amplified first RF signal and output the amplified
first RF signal to one of the first plurality of mixers, one of the
second plurality of mixers, and the first loop-through buffer.
21. An integrated circuit (IC) comprising: a first voltage
controlled oscillator (VCO) to oscillate at a first oscillation
frequency; a second VCO to oscillate at a second oscillation
frequency; a first divider coupled to the first VCO to produce a
first LO signal; a second divider coupled to the second VCO to
produce a second LO signal; wherein the first LO signal and the
second LO signal are substantially at a common frequency, and a
frequency range of the first oscillation frequency and a frequency
range of the second oscillation frequency are mutually
exclusive.
22. The IC of claim 21, wherein the IC comprises a single
semiconductor die including a first tuner and a second tuner.
23. The IC of claim 22, wherein the first tuner comprises a first
plurality of mixers each to selectively receive the first LO signal
and a second plurality of mixers each to selectively receive the
second LO signal.
24. The IC of claim 23, wherein in a first mode the first tuner and
the second tuner are to process concurrently a common signal band
obtained from a first antenna.
25. The IC of claim 23, wherein in a second mode the first tuner is
to process a signal from a first antenna and, concurrently, the
second tuner is to process a signal from a second antenna.
Description
BACKGROUND
[0001] In certain radio reception environments such as an
automotive environment, multiple antennas and tuners may be present
to enable a variety of use cases such as phase diversity reception,
dual band reception, audio and data reception, among others.
Existing fully-integrated techniques can share one antenna between
multiple radio frequency (RF) and/or intermediate frequency (IF)
signal paths only with degraded performance on one or both of the
signal paths. For instance, if a loop-through buffer is used to
feed the RF signal to a secondary path, the secondary path's
performance is generally compromised relative to the primary path
due to the loop-through buffer's RF characteristics. This
asymmetric performance is undesirable for a number of reasons.
[0002] As another example, if one antenna is connected to two RF
inputs, and those inputs are designed to each present twice the
desired termination impedance for the antenna, an effective RF
split is realized, but the two paths will be compromised due to
sharing power between the inputs. One solution to this problem is
inclusion of an external (to one or more integrated tuners) active
splitter circuit to buffer the antenna signal. However, this
circuit increases component counts, raises costs and complexity,
including routing issues and power consumption.
SUMMARY OF THE INVENTION
[0003] In one aspect, an apparatus comprises a first low noise
amplifier (LNA) to receive and amplify a first radio frequency (RF)
signal of a first band, received from a first antenna and a first
tuner having a first plurality of mixers including a first mixer to
selectively be coupled to the first LNA to receive and downconvert
the first RF signal received from the first LNA to a first
downconverted signal. The first tuner may be configured to process
the first downconverted signal. In addition, the apparatus further
comprises a second LNA to receive and amplify a second RF signal of
a second band, received from a second antenna, and a second tuner
having a second plurality of mixers including a second mixer to
selectively be coupled to the second LNA to receive and downconvert
the second RF signal received from the second LNA to a second
downconverted signal and a first mixer to selectively be coupled to
the first LNA to receive and downconvert the first RF signal
received from the first antenna to a third downconverted signal.
The second tuner may be configured to be controllable to process a
selected one of the second downconverted signal and the third
downconverted signal provided by a selected one of the second mixer
and the first mixer of the second tuner.
[0004] In a first mode of operation, the first LNA is coupled to
provide the first RF signal to the first tuner and to the second
tuner simultaneously. The apparatus may further include a third LNA
to receive and amplify a third RF signal of the first band,
received from a third antenna, where the third LNA is coupled to
provide the third RF signal to the second tuner to enable phase
diversity reception of the first band in a second mode.
[0005] In an example, the apparatus may further include an audio
processor and a phase diversity combining circuit to seamlessly
transition from the first mode to the second mode without audible
impact to an audio signal output from the apparatus.
[0006] In an example, the first plurality of mixers further
includes a second mixer to selectively be coupled to the second LNA
to receive and downconvert the second RF signal to a fourth
downconverted signal. The apparatus may further include a first
loop-through buffer coupled to an output of the first LNA to
receive the first RF signal and output the first RF signal to a
second receiver coupled to the apparatus, where the apparatus
includes a first receiver. The apparatus may further include a
second loop-through buffer coupled to an output of the second LNA
to receive the second RF signal and output the second RF signal to
the second receiver. The apparatus may further include a selector
coupled to an output of the first loop-through buffer and an output
of the second loop-through buffer and controllable to output a
selected one of the first and second RF signals to the second
receiver.
[0007] In an example, the first tuner may include a multiplexer
coupled to an output of the first plurality of mixers, the
multiplexer controllable to provide an output of one of the first
plurality of mixers to a signal processing path of the first tuner.
The first tuner may further include a first frequency generator to
operate at a first frequency and the second tuner may further
include a second frequency generator to operate at a second
frequency substantially different than the first frequency when the
first tuner and the second tuner are to operate in a first band. A
filter may be coupled to an output of the first LNA to provide a
notch response to reduce coupling from the second frequency
generator. In an example, the first LNA, the first tuner, the
second LNA and the second tuner are configured on a first
semiconductor die.
[0008] In another aspect, a method includes: in a first mode,
causing a first tuner of an entertainment system to receive and
process a first RF signal from a first antenna configured for a
first band to output a first audio signal of a first radio station
and causing a second tuner of the entertainment system to receive a
second RF signal from a second antenna configured for the first
band to determine signal quality metrics for one or more radio
stations of the first band; in a second mode, causing the first
tuner to output a first signal representation of the first RF
signal and causing the second tuner to receive and process the
second RF signal from the second antenna to output a second signal
representation of the second RF signal; and causing a phase
diversity combining circuit to process the first and second signal
representations to output an audio signal of the first radio
station, without disruption of output from the entertainment system
of a broadcast of the first radio station.
[0009] In an example, the method further includes, in a third mode,
causing the first tuner to receive and process the first RF signal
from the first antenna to generate a first audio signal of the
first radio signal, and causing the second tuner to receive and
process the second RF signal from the second antenna to generate a
second audio signal of a second radio station, and causing a linker
circuit to transition from the first audio signal to the second
audio signal, where the linker circuit is to output a final audio
signal without impairments due to the transition.
[0010] In another example, a non-transitory computer readable
medium include(s) instructions that when executed enable the
entertainment system to perform one or more methods as described
herein.
[0011] In yet another aspect, a system includes, at least, multiple
antennas and a first integrated circuit (IC) including a first
tuner and a second tuner. In an example, the first IC includes: a
first pad to receive a first RF signal from a first FM antenna and
symmetrically output the first RF signal to the first tuner and the
second tuner, and to a first loop-through buffer to provide the
first RF signal to a second IC; and a second pad to receive a
second RF signal from a second FM antenna and symmetrically output
the second RF signal to the first tuner and the second tuner, and
to a second loop-through buffer to provide the second RF signal to
the second IC. In turn, the first tuner may have a first plurality
of mixers including a first mixer to receive and downconvert the
first RF signal to a first downconverted signal, a second mixer to
receive and downconvert the second RF signal to a second
downconverted signal, and a first signal processing path to process
a selected one of the first downconverted signal and the second
downconverted signal. In turn, the second tuner may have a second
plurality of mixers including a second mixer to receive and
downconvert the second RF signal to a fourth downconverted signal,
a first mixer to receive and downconvert the first RF signal to a
third downconverted signal, and a second signal processing path
dynamically controllable to process a selected one of the third
downconverted signal and the fourth downconverted signal. In an
example, the first IC may further include a microcontroller to
dynamically control transitions of the first tuner and the second
tuner between a plurality of operating modes while a first audio
signal is output by at least one of the first and second
tuners.
[0012] In yet another aspect, an IC includes a first voltage
controlled oscillator (VCO) to oscillate at a first oscillation
frequency, a second VCO to oscillate at a second oscillation
frequency, a first divider coupled to the first VCO to produce a
first LO signal, and a second divider coupled to the second VCO to
produce a second LO signal. In an example, the first LO signal and
the second LO signal are substantially at a common frequency, and a
frequency range of the first oscillation frequency and a frequency
range of the second oscillation frequency are mutually
exclusive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1A and 1B are block diagrams of a receiver in
accordance with an embodiment.
[0014] FIG. 2 is a block diagram of a multi-chip radio system in
accordance with an embodiment.
[0015] FIG. 3 is a flow diagram of a method in accordance with an
embodiment.
DETAILED DESCRIPTION
[0016] In various embodiments, a radio receiver including one or
more tuners may have an integrated active splitter to route an
incoming RF signal to multiple paths in a symmetric and seamless
manner. Still further, embodiments enable full flexibility in
choosing which of multiple antennas feeds which of multiple signal
paths. This selection can be changed dynamically in real time as a
radio reception environment and/or listener station selection
changes. An architecture as described herein allows for fully
flexible reception of one or more radio stations for primary
reception, phase diversity reception, secondary reception (e.g.,
rear-seat entertainment), background/alternate station scanning,
and/or traffic data reception from one or more antennas with
symmetric performance and/or minimal performance loss.
[0017] As will be described further herein, different and dynamic
modes of operation are possible. For example, reception could begin
by receiving an FM station from one antenna connected to a first IF
path of a first tuner. Subsequently, a second antenna may be
connected to a second IF path of a second tuner and tuned to the
same station, to realize phase diversity reception. The system
could subsequently return to single antenna reception, and the
second IF signal path could be used for background station scanning
from either antenna input, all without perturbing the audio content
being listened to from the first IF path. In other use cases, the
second path could subsequently be tuned to a digital audio
broadcast (DAB) station using a Band-III antenna input for the
purposes of DAB/FM seamless linking. Once the link to DAB audio
content is made, the first IF path of the first tuner could be
configured to receive its input from the second Band-III antenna to
realize phase diversity reception for DAB. Or the first tuner may
be configured to perform background scanning, either for DAB or FM
bands, while the second tuner is to output the audio content via
the second IF path. In addition to background scanning, the tuners
may be used also to obtain supplemental content such as radio
broadcast data system/radio data system (RBDS/RDS) content, traffic
message channel (TMC) content, and Transport Protocol Exports Group
(TPEG) content. Note that during any or all of the above modes,
selected RF inputs received on-chip via one or more RF input pads
may be output to a downstream component via a loop-through
path.
[0018] Referring now to FIGS. 1A and 1B, shown are block diagrams
of a receiver in accordance with an embodiment. More specifically,
receiver 100 may be a multi-tuner arrangement, which may be
configured on a single semiconductor die. As described herein,
receiver 100 provides for integrated active splitting of incoming
RF signals from one or more antennas, to enable dual tuners to
process the same RF signal with symmetric performance. That is, the
same RF signal is provided simultaneously to the two tuners at the
same power level such that the two tuners process an identical (or
at least nearly or substantially identical) signal. Still further,
with active splitting as described herein, embodiments enable
seamless transitions between different modes of operation in which
RF inputs from different antennas can be switchably coupled to the
different tuners.
[0019] As illustrated in FIG. 1A, receiver 100 includes a number of
inputs pads 105.sub.1-105.sub.5. In the illustration shown, each
input pad 105 may receive an RF input obtained from a given antenna
(not shown in FIG. 1A, as such antennas may be implemented
off-chip). In the embodiment of FIG. 1A, these RF inputs may be
received in multiple bands. Specifically, two FM RF inputs (FMA and
FMB), two Band-III RF inputs (B3A and B3B), and a single AM band RF
input (AMI) are provided. As illustrated, the incoming RF input
signals are coupled to corresponding amplifiers 110a, 110b, 112a,
112b, and 114. In an embodiment, each amplifier may be implemented
as a low noise amplifier (LNA), possibly followed by an RF
buffer.
[0020] In some cases, a simple buffer either integrated within the
LNAs (as schematically shown in FIG. 1A) or coupled to an output of
such LNAs, may be provided to buffer the amplified RF signal. This
buffer may be provided, given that the amplifier output may couple
to multiple tuners (and also potentially be output off-chip via a
loop-through buffer). Thus to better accommodate this loading, such
buffer may be incorporated within the corresponding LNAs or coupled
to an output thereof.
[0021] In addition, embodiments may further provide a filtering
function within or closely coupled to the output of the LNAs. More
specifically, such a filter, which can be a low pass filter having
a predetermined notch capability, can be used to filter noise from
a frequency synthesizer of another tuner on-die. In one embodiment,
this filter may be configured to have a notch at a frequency
substantially around 2.8 Gigahertz (GHz). By providing this
filtering capability substantially at the output of the LNAs,
individual filters at an input of each of downstream mixers can be
avoided.
[0022] As discussed above, receiver 100 is a dual-tuner receiver
including a first tuner 130.sub.1 and a second tuner 130.sub.2. The
tuners may be configured as intermediate frequency (IF) tuners to
downconvert and process the incoming signals at a given IF
frequency. However embodiments are not so limited and in other
cases, the tuners may be configured as low IF or zero-IF (ZIF)
tuners. With reference first to first tuner 130.sub.1, a set of
mixers 120.sub.11-120.sub.15 are provided. As seen, each mixer is
coupled to receive an incoming amplified RF signal from one of
amplifiers 110a/b, 112a/b, and 114. In turn, each mixer 120
downconverts the received RF signal with a mixing signal, received
from a local oscillator (LO) 124.sub.1, which in turn receives an
incoming clock signal, generated by an RF synthesizer 122.sub.1. In
one embodiment, RF synthesizer 122.sub.1 may be configured for
operation at substantially around 3.0 GHz. Depending upon the
frequency of a desired channel or station, LO 124.sub.1 may be
controlled (e.g., by an on-chip microcontroller (MCU) 150) to
output the mixing signal at a given frequency. Further, to enable
operation with minimal power consumption, MCU 150 may control the
corresponding mixers 120 of the different tuners such that only a
single mixer of each tuner is active at a given time. Such control
may be effected, e.g., by disabling the non-selected mixers. In
some cases, MCU 150 may disable the LO input to unselected (i.e.,
unused) mixers 120.
[0023] The downconverted signals output by mixers 120 are coupled
through a selector 125.sub.1 (which in an embodiment may be
implemented as a multiplexer) to a programmable gain amplifier
126.sub.1. After amplification and filtering in PGA 126.sub.1, the
signal is digitized in an analog-to-digital converter (ADC)
128.sub.1. From there the digitized downconverted signal may be
provided to a signal processing path of tuner 130.sub.1, which may
perform various additional processing, including filtering, gain
control, decoding and/or demodulation to output a demodulated
signal such as demodulated FM or AM signals. In some cases,
depending upon the band of operation, the output of a given tuner
130.sub.1 may be a modulated signal, such as in the case of DAB or
HD input.
[0024] As further shown in FIG. 1A, loop-through paths are provided
to enable output of the amplified RF signals (from the output of
amplifiers 110/112/114) to be communicated to one or more other
components, such as other ICs including tuners or other processing
circuits, such as background scan or traffic data receivers.
Specifically, loop-through buffers (LTB) 111a and 111b couple to
outputs of amplifiers 110a and 110b, to output a corresponding RF
FM signal via loop-through pads (LTA and LTB). As seen, switches S1
and S2 may be controlled (e.g., under control of MCU 150) to enable
output of such FM signals. Similarly, loop-through buffers 113a and
113b couple to outputs of amplifiers 112a and 112b, to output a
corresponding RF Band-III signal via the loop-through pads, as
controlled by switches S1 and S2. As also shown, a loop-through
buffer 115 may output an AM RF signal output by LNA 114 via another
loop-through pad, AMO.
[0025] With reference now to second tuner 130.sub.2 on the same IC,
a second set of mixers 120.sub.21-120.sub.25 are provided. As seen,
each mixer is coupled to receive an incoming amplified RF signal
from one of amplifiers 110a/b, 112a/b, and 114. In turn, each mixer
120 downconverts the received RF signal with a mixing signal,
received from a LO 124.sub.2, which in turn receives an incoming
clock signal, generated by an RF synthesizer 122.sub.2. In one
embodiment, RF synthesizer 122.sub.1 may be configured for
operation at substantially around 4.4 GHz or another frequency
substantially separated from the output of RF synthesizer
122.sub.1.
[0026] The downconverted signals output by mixers 120 are coupled
through a selector 125.sub.2 (which in an embodiment may be
implemented as a multiplexer) to a programmable gain amplifier
126.sub.2. After amplification in PGA 126.sub.2, the signal is
digitized in an ADC 128.sub.2. From there the digitized
downconverted signal may be provided to a signal processing path of
tuner 130.sub.2, which may perform various processing, including
filtering, gain control, decoding and/or demodulation to output a
demodulated signal such as demodulated FM or AM signals, or a
modulated signal, such as in the case of DAB or HD input.
[0027] More specifically, FIG. 1B illustrates high level circuitry
further present in a multi-tuner IC. More specifically, after
digitization in corresponding ADCs 128.sub.1, 128.sub.2 the
digitized downconverted signals are provided to separate signal
processing paths of tuners 130.sub.1, 130.sub.2. In the embodiment
shown, such tuner circuitry may be implemented as radio digital
signal processors (DSPs) 135.sub.1, 135.sub.2. As described above,
depending upon particular mode and band of operation, radio DSPs
135 may further condition and process the digitized signals and
demodulate the signals to result in demodulated signals, e.g., of
an FM band, which can be directly output from radio DSPs 135.
[0028] Still further, additional processing circuitry may be
provided. As shown, an audio processor 140 may be provided to
further process the demodulated signals. In the illustrated
embodiment, audio processor 140 includes a phase diversity circuit
142. In various embodiments, phase diversity circuit 142 may be
configured to receive common content, e.g., of a given radio
station by way of the multiple signal processing paths and perform
phase diversity by selecting a given one of the two signals for
output, e.g., based on signal quality metrics. In another
embodiment, phase diversity circuit 142 may be configured to
perform phase diversity processing based on a maximal ratio
combining technique.
[0029] As further illustrated, audio processor 140 may further
include a linker circuit 144. In various embodiments, linker
circuit 144 may be configured to perform seamless linking, such
that the same audio content as obtained from two different antennas
(and potentially two different bands), can be linked together. For
example, linker circuit 144 may be configured to enable a smooth
transition from audio content obtained from an FM signal output to
audio content obtained from a DAB signal output when reception
conditions for the FM signal fall below a threshold (and vice
versa). This linking may be performed seamlessly or transparently
to the user, such that the user does not detect the transition, nor
is the audio output adversely affected. As further illustrated,
audio processor 140 may further include an audio DSP 146, which may
perform further audio processing as desired to output a stream to a
digital-to-analog converter (DAC) 150, such that an audio output is
provided.
[0030] Still further shown, audio processor 140 may further receive
incoming audio input, e.g., from a similarly configured second IC
including one or more receivers/tuners (and/or from a downstream
external linker circuit/demodulator).
[0031] Thus in the embodiment of FIGS. 1A and 1B, each tuner 130
can receive its input from any one of two FM, two Band-III, and one
AM RF antenna input. Each RF input can simultaneously drive either
or both of the IF signal paths of these tuners and/or a
loop-through buffer for connecting to a downstream receiver such as
a background scan or traffic data receiver. When one RF input is
used to feed both IF signal paths, both paths will have symmetric
performance (which is a desirable characteristic in that signal
levels, phases, and other characteristics are identical (or nearly
identical)). Another benefit of an architecture as in FIGS. 1A and
1B is that a substantially seamless transition between different
operating states can be accomplished entirely on-chip under control
of MCU 150. That is, a transition of operating mode can occur in a
manner transparent to a listener, as the transition occurs without
any audible click, pop, delay or other signal distortion.
[0032] In an embodiment, frequency synthesizers 122.sub.1,122.sub.2
may include LC tank-based voltage controlled oscillators (VCOs)
that operate at substantially different frequencies, to reduce
unwanted coupling. In the example described above, frequency
synthesizer 122.sub.1 may operate at approximately 3.0 GHz, while
frequency synthesizer 122.sub.2 is to operate substantially at
approximately 4.4 GHz. Understand that these frequency synthesizers
can be dynamically controlled by MCU 150 to operate at a given
frequency, which may vary depending upon band of operation. In any
case, these frequency synthesizers (and more specifically the VCOs
included therein) may be constrained from operation within a given
frequency range of each other. In one embodiment, MCU 150 may
control the VCOs to maintain a minimum frequency separation of 500
megahertz (MHz). In addition, frequency synthesizers 122 may be
controlled to vary frequency using a rasterization technique, such
that any changes to the VCO frequencies occur in steps of at least
500 kilohertz (kHz), to minimize harmful coupling between VCOs and
reduce spurs in the LO outputs.
[0033] With this frequency separation of frequency synthesizers
122, frequencies generated by the different VCOs, which may include
the fundamental oscillation frequency of each oscillator as well as
harmonic frequencies thereof, avoid coupling to one another,
preventing large spurs in each other. By using frequency
synthesizers that operate at two very different frequency ranges
(and which are mutually exclusive ranges), the level of the spurs
can be greatly reduced, in that the LC tank frequency response of
the VCOs can attenuate the energy coupled from one VCO to the
other. In one example, the LC tanks of the two different frequency
synthesizers can be of substantially different inductances to
realize the frequency separation. As one such example, to enable RF
synthesizer 122.sub.2 to operate at 4.4 GHz, the LC tank may have a
given capacitance (e.g., x picoFarads, where x can vary in
different embodiments) and an inductance of approximately 800
picoHenries in an example embodiment. In turn, RF synthesizer
122.sub.1, to operate at 3.0 GHz may have a capacitance of 1.6 x
picoFarads and an inductance of approximately 1 nanoHenry.
[0034] To further reduce spurs, LOs 124.sub.1, 124.sub.2 may be
implemented within respective shielded regions. Two different FM or
Band-III stations can be received within the same IC and not have
the spurs that would be associated when using two VCOs of the same
frequency range. Understand while shown at this high level in the
embodiment of FIGS. 1A and 1B, many variations and alternatives are
possible.
[0035] Referring now to FIG. 2, shown is a block diagram of a
multi-chip radio system in accordance with an embodiment. As shown
in FIG. 2, system 200 may be implemented as an automotive radio
system that has multiple tuner chips, namely a first tuner chip 220
and a second tuner chip 260, along with a third demodulator chip
250. Understand while shown with three different ICs in this
embodiment, in other cases some or all of the hardware circuitry of
these three different ICs can be implemented into one or more die
of a single IC. Still further, different variations in the amount
and type of circuitry of each IC is possible.
[0036] As illustrated, incoming RF signals are received by a
plurality of antennas 210.sub.1-210.sub.2. Understand while shown
with two antennas for ease of illustration, in many cases a given
vehicle may include more than two antennas. As examples, some
vehicles may include two (or more) FM antennas, two (or more)
Band-III antennas, and at least one AM antenna. However for ease of
illustration, two representative antennas are shown (understanding
that this representation of two may actually be implemented as more
than two antennas).
[0037] To recover RF signals of given bands, antennas 210 may
couple to filters/antenna switches 215.sub.1-215.sub.2, which may
perform appropriate filtering to thus output RF signals of at least
three bands, namely FM, DAB and AM. In particular vehicle
installations, antennas 210 and switches 215 may be implemented at
a given location, e.g., near a rear of a vehicle, as antennas 210
may be implemented on rear windows, rear side windows, a roof or
trunk-mounted unit or so forth. Circuitry may be provided in close
proximity to such antennas to provide the RF signals, e.g., via one
or more coaxial cables, to tuners 220/260.
[0038] In the embodiment shown, tuners 220/260 may be separate
instantiations of the same tuner device. However, these different
tuners may be differently configured to perform different primary
functions. As such, each tuner is shown with different constituent
components in FIG. 2. Thus as illustrated, tuner 220 may be
configured to operate as a primary FM and AM tuner, while tuner 260
may be configured to operate as a primary DAB tuner. More
specifically, with reference to tuner 220, it includes dual tuner
circuitry 230 to perform FM phase diversity processing, dual FM
channel processing (e.g., two different FM channels, one for a
primary entertainment system and one for a secondary (e.g., rear
seat) entertainment system), FM and DAB seamless linking, and AM
band operations (and of course single channel FM reception).
[0039] As such, tuner 220 is configured to directly receive FM RF
signals from antennas 210.sub.1 and 210.sub.2 via input pads
222.sub.a and 222.sub.b. In addition, to enable the same signals to
be provided to second tuner 260, the incoming FM RF signals may be
output via loop-through pads 223.sub.a and 223.sub.b. Similarly, as
tuner 220 acts as a secondary DAB tuner, it receives incoming DAB
band RF signals indirectly from second tuner 260, rather than
directly from antennas 210, via input pads 224.sub.a/224.sub.b. As
further illustrated, tuner 220 receives an AM band RF signal via
input pad 225.
[0040] After appropriate processing of one or more FM signals in
dual tuner circuitry 230, resulting demodulated signals can be
provided to an audio digital signal processor (DSP) 235 for
additional audio processing (e.g., multi-channel processing) such
that audio outputs can be provided via multiple channels
236.sub.a-236.sub.c including corresponding digital-to-analog
converters to enable audio output to desired destinations (e.g.,
multiple channels of speakers). As further shown, demodulated FM
audio can be output via pad 238 to demodulator 250, as described
below. As further shown, blended audio can be received via pad 240
to enable further audio processing in audio DSP 235 and output from
tuner 220.
[0041] In similar manner, tuner 260 includes dual tuner circuitry
270 to perform DAB phase diversity or multi-ratio combining
processing, dual DAB channel processing (e.g., two different DAB
channels, one for a primary entertainment system and one for a
secondary (e.g., rear seat) entertainment system), FM and DAB
seamless linking.
[0042] As such, tuner 260 is configured to directly receive DAB RF
signals from antennas 210.sub.1 and 210.sub.2 via input pads
264.sub.a and 264.sub.b. In addition, to enable the same signals to
be provided to first tuner 220, the incoming DAB RF signals may be
output via loop-through pads 263.sub.a and 263.sub.b. Similarly, as
tuner 260 acts as a secondary FM tuner, it receives incoming FM RF
signals indirectly from first tuner 220, rather than directly from
antennas 210, via input pads 262.sub.a/262.sub.b. As further
illustrated, tuner 260 receives an AM band RF signal via
loop-through pad 265.
[0043] After appropriate processing of one or more DAB signals in
dual tuner circuitry 270, resulting DAB-modulated signals can be
provided to demodulator 250 via pad 266 for demodulation and
potentially linking with an FM signal from first IC 220.
[0044] As further illustrated in FIG. 2, demodulator 250 may be
configured to demodulate incoming modulated DAB signals received
from tuner 260. More specifically, dual tuner circuitry 270 may
output DAB signals from both tuners as two sets of I/Q data to
demodulator 250, which may thus demodulate the DAB signals and
provide the demodulated DAB signals to first tuner 220 for further
audio processing and output. Similarly, when a mode of operation
for FM-DAB blending is active, demodulator 250 may perform seamless
linking between the same audio content from these two different
bands. To this end, demodulator 250 may include a large amount of
memory, e.g., buffer circuitry, to buffer processed audio of a
leading one of these bands, so that the common content of the two
bands may be linked up in time such that transitioning between
either stream is not noticeable to the listener. Note also that
demodulator 250 may further perform maximal ratio combining (MRC)
phase diversity for HD and/or DAB signals.
[0045] Understand also that while FIG. 2 shows an implementation
with multiple separate ICs, embodiments are not so limited and in
another implementation more than two tuners may be adapted within a
single IC, e.g., all adapted on a single semiconductor die or as
separate die within a multichip module (MCM). In some cases, the
external modulator/linker 250 also may be implemented within an IC,
e.g., on a single semiconductor die or as part of a MCM.
[0046] Referring now to FIG. 3, shown is a flow diagram of a method
in accordance with an embodiment. As shown in FIG. 300, a control
logic, such as a hardware-based microcontroller of a tuner, which
may be in communication with a host processor of an entertainment
system, may be configured to cause a multi-tuner as described
herein to perform in a wide variety of different operation modes.
Understand that the following discussion of FIG. 3 is primarily
with regard to receipt and processing of a first radio station
desired by a listener. Of course understand that many of the
different modes of operation and transitions between them can occur
when a listener desires to tune to a different station. In the
various modes of operation described herein, background operations
also may be performed. Such operations, which may be performed on
one or both tuners, can be used to perform background scans of
available stations and determine signal quality metrics thereof
[0047] In addition, non-audio data such as RDS and/or traffic data
may be obtained by these background operations. Information
determined by way of these tuners can be provided to the
microcontroller, which in turn may be in communication, e.g., via a
given software application programming interface (API), with the
host processor. As such, the host processor may be the primary
initiator of audio system mode transitions described herein, based
on user input and operating program. In turn, the host processor
provides instructions to the microcontroller, to cause the
microcontroller to flexibly configure and re-configure the
multi-tuner to perform in a given mode of operation and transition
as appropriate between operating modes.
[0048] With reference to FIG. 3, in a first mode of operation
(block 310), a first radio station is tuned using a first FM
antenna and a first tuner. After appropriate signal processing of
the received FM signal, an audio signal of the first radio station
can be output, from the first tuner to an output of the
entertainment system (e.g., speakers).
[0049] In another mode of operation (block 320), phase diversity
may be performed to cause this same first radio station to be
output by both tuners as modulated signal to be combined in a phase
diversity combining circuit, and thereafter demodulated and output
as an audio signal. Here, each tuner is coupled to a different
antenna, to enable this phase diversity operation. This transition
may be initiated when the first antenna suffers an impairment in
signal reception, e.g., due to multipath fading. Note that the
transition between single antenna reception and phase diversity
reception may occur seamlessly, that is without any audio artifact,
pop, click or other audible distortion.
[0050] At block 330 another mode of operation may occur to perform
background scanning. More specifically, the microcontroller may
cause the second tuner to be switched to a background scan mode to
determine signal quality metrics for one or more background radio
stations (as well as for the first radio station). As discussed
above, this information as determined in the second tuner can be
provided to the microcontroller that in turn provides it to the
host processor. In this mode, the first tuner may continue to tune
and output the first radio station.
[0051] In addition to determining signal quality metrics for FM
channels, the tuner may also perform such background scan
operations with regard to DAB channels. As such, in another mode of
operation as shown at block 340 this second tuner may be switched
to receive an input from a Band-III antenna to perform such
background scanning. In this mode still, the first tuner may
process and output the first radio station.
[0052] Assume that as a vehicle travels, its signal quality for
this first radio station received via the FM band begins to
degrade. However, assume also presence of an available DAB channel
for this same radio station. In this instance, at block 350 another
mode of operation enables the first radio station to be tuned in a
DAB channel via the second tuner. These two signals of the same
content may then be seamlessly linked, accounting for delay
differences between the two signals. In an embodiment, this
seamless linking may be performed by downstream circuitry such as a
separate demodulator/linker chip. Thereafter, operation may
continue with the first radio station being received and processed
using the DAB channel. Thus at this point the first tuner is
available, and at block 360 another mode of operation enables phase
diversity processing for the DAB channel. As such, the first tuner
may be controlled to receive a Band-III signal from a Band-III
antenna and output the DAB channel to perform phase diversity
processing.
[0053] In some instances, audio content of a given radio station
may be transmitted on multiple or alternate frequencies, e.g.,
where each of multiple transmit antennas is located in a different
geographic location. Assume that a vehicle is travelling such that
it begins losing the signal from a first transmit antenna that
transmits at a first frequency. However, based on background
scanning it is determined that the same audio content is available
on an alternate frequency, e.g., via a same or different radio
station having a transmit antenna that transmits at a second
frequency. Thus as shown at block 370, alternate frequency
switching may be performed such that the second tuner is switched
to tune to the radio station via an alternate frequency (e.g.,
using a DAB input). After appropriate blending, audio content of
this alternate frequency station can be output via the second
tuner.
[0054] As further shown in FIG. 3, at block 380 (shown in a dashed
box as being optional), one or more of the received RF signals can
be provided to one or more downstream tuners via bypass paths, such
as the loop-through buffers described above.
[0055] Understand while shown with these particular modes of
operation and switching of control between the different tuners is
shown, many variations and alternatives are possible. Furthermore,
while specific transitions between the different modes of operation
are described above, it is possible for many other transitions
between the modes described above and other modes to occur. Still
further, while specific representative tuners to process given RF
signals from given antennas were discussed above, understand that
such selection is arbitrary, and a given programming of an MCU or
other control logic with programmable instructions stored in a
non-transitory storage medium may call for the operation to be
performed by different tuners or combinations of tuners. And while
the above examples relate to AM, FM and DAB bands, embodiments
apply to tuners and control logic configured for additional radio
bands.
[0056] While the present invention has been described with respect
to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations as fall within the true spirit and scope of this present
invention.
* * * * *