U.S. patent application number 09/948498 was filed with the patent office on 2002-05-09 for cryogenic devices.
Invention is credited to Laubacher, Daniel B., Lauder, Alan, Pang, Philip Shek Wah, Shen, Zhi-Yuan.
Application Number | 20020053215 09/948498 |
Document ID | / |
Family ID | 26924458 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020053215 |
Kind Code |
A1 |
Laubacher, Daniel B. ; et
al. |
May 9, 2002 |
Cryogenic devices
Abstract
This invention relates generally to cryogenic devices and, more
particularly, to cryogenic devices of very small size based on
superconducting elements, low thermal transmission interconnects
and low dissipated power semiconductor devices.
Inventors: |
Laubacher, Daniel B.;
(Wilmington, DE) ; Shen, Zhi-Yuan; (Wilmington,
DE) ; Pang, Philip Shek Wah; (Media, PA) ;
Lauder, Alan; (Kennett Square, PA) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
26924458 |
Appl. No.: |
09/948498 |
Filed: |
September 7, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60230682 |
Sep 7, 2000 |
|
|
|
60265917 |
Feb 2, 2001 |
|
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Current U.S.
Class: |
62/259.2 |
Current CPC
Class: |
H01P 1/30 20130101 |
Class at
Publication: |
62/259.2 |
International
Class: |
F25D 023/12 |
Claims
What is claimed is:
1. A cryogenic device comprising a cryogenic electronic portion, a
non-cryogenic electronic portion and an interconnect connecting the
cryogenic electronic portions and the non-cryogenic electronic
portions, wherein the interconnect comprises a thermal break
between the cryogenic electronic portion and non-cryogenic
electronic portions.
2. The cryogenic device of claim 1, wherein the interconnect
comprises a microstrip line on a low thermal conductivity
substrate.
3. The cryogenic device of claim 2, wherein the substrate comprises
one or more of a fused silica and an aerogel.
4. The cryogenic device of claim 1, wherein the cryogenic
electronic portion comprises one or both of a high temperature
superconductor filter element and a cryogenic active semiconductor
circuit.
5. The cryogenic device of claim 1, wherein the cryogenic
electronic portion comprises a high temperature superconductor
filter element comprising one or more mini-filters based on
self-resonant spiral resonators.
6. A cryogenic device comprising: (1) a cryogenic electronic
portion contained within a vacuum dewar assembly, the cryogenic
electronic portion having an input end and an output end; (2) an
ambient to cryogenic input connector having an ambient end passing
through the vacuum dewar assembly to a cryogenic end connected to
the input end of the cryogenic electronic portion, (3) a cryogenic
to ambient output connector having a cryogenic end connected to the
output end of the cryogenic electronic portion, passing through the
vacuum dewar assembly to an ambient end; and (4) a cryogenic source
connected to the vacuum dewar assembly so as to be in intimate
contact with the cryogenic electronic portion, wherein: (i) the
cryogenic electronic portion comprises at least one of a high
temperature superconductor filter element and a cryogenic active
semiconductor circuit, (ii) an active semiconductor circuit, if
present, produces a total dissipated power into the cryogenic
electronic portion of less than about 850 mW, and (iii) the
cryogenic device has a maximum cooler lift of less than about 3 W
at 80 K at an ambient temperature of 20.degree. C.
7. The cryogenic device of claim 6, wherein the cryogenic
electronic portion comprises a high temperature superconductor
filter element having an input end and an output end, and an active
semiconductor circuit having an input end and an output end,
wherein: the input end of the active semiconductor circuit is
connected to the cryogenic end of the input connector via the high
temperature superconductor filter element; the input end of the
filter element is connected to the cryogenic end of the input
connector; and the output end of the filter element is connected to
the input end of the active semiconductor circuit.
8. The cryogenic device of claim 6, wherein the cryogenic
electronic portion comprises an active semiconductor circuit
selected from one or a combination of amplifiers, mixers,
analog-to-digital converts and digital processors.
9. The cryogenic device of claim 8, wherein the active
semiconductor circuit is a cryogenic amplifier.
10. The cryogenic device of claim 6, wherein the cryogenic
electronic portion comprises a high temperature superconductor
filter element comprising one or more mini-filters based on
self-resonant spiral resonators.
11. The cryogenic device of claim 10, further comprising a
superconducting plate above at least the filter element and in
intimate contact with the cryogenic source.
12. The cryogenic device of claim 6, wherein one or both of the
ambient to cryogenic input connector and cryogenic to ambient
output connector is a thermal break.
13. The cryogenic device of claim 6, wherein the cryogenic source
is a cryocooler, wherein the cryocooler and vacuum dewar assembly
are formed as an integral unit or assembly.
14. The cryogenic device of claim 6, wherein the cryogenic
electronic portion comprises a high temperature superconductor
filter element comprising one or more mini-filters based on
self-resonant spiral resonators; wherein one or both of the ambient
to cryogenic input connector and cryogenic to ambient output
connector is a thermal break; and wherein the cryogenic source is a
cryocooler, wherein the cryocooler and vacuum dewar assembly are
formed as an integral unit or assembly.
15. A cryogenic receiver comprising the cryogenic device of claim
6.
16. The cryogenic receiver of claim 15, wherein the cryogenic
source is a cryocooler, wherein the cryocooler and vacuum dewar
assembly are formed as an integral unit or assembly.
17. The cryogenic receiver of claim 15, wherein the cryogenic
electronic portion comprises a high temperature superconductor
filter element comprising one or more mini-filters based on
self-resonant spiral resonators; wherein one or both of the ambient
to cryogenic input connector and cryogenic to ambient output
connector is a thermal break; and wherein the cryogenic source is a
cryocooler, wherein the cryocooler and vacuum dewar assembly are
formed as an integral unit or assembly.
18. An integrated antenna assembly comprising the cryogenic
receiver of claim 15 and an antenna assembled as an integrated
unit.
19. The integrated antenna assembly of claim 18, wherein the
cryogenic source is a cryocooler, wherein the cryocooler and vacuum
dewar assembly are formed as an integral unit or assembly.
20. The integrated antenna assembly of claim 18, wherein the
cryogenic electronic portion comprises a high temperature
superconductor filter element comprising one or more mini-filters
based on self-resonant spiral resonators; wherein one or both of
the ambient to cryogenic input connector and cryogenic to ambient
output connector is a thermal break; and wherein the cryogenic
source is a cryocooler, wherein the cryocooler and vacuum dewar
assembly are formed as an integral unit or assembly.
21. A method of tuning a cryogenic receiver comprising a high
temperature superconducting filter element, said cryogenic receiver
being programmed to operate at a specified operating frequency at a
specified temperature, comprising the step of altering the
specified operating temperature to induce a shift in the operating
frequency of the cryogenic receiver.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims prior under 35 U.S.C. .sctn.119 from
U.S. Provisional Application Ser. No. 60/230,682, filed Sep. 7,
2000, and U.S. Provisional Application Ser. No. 60/265,917, filed
Feb. 2, 2001, both of which are incorporated by reference herein as
if fully set forth.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to cryogenic front-end
receivers and, more particularly, to cryogenic front-end receivers
of minimal size based on superconducting elements, low thermal
transmission interconnects, self-resonating filters and low
dissipated power profile.
[0004] 2. Description of the Related Art
[0005] Until the late 1980s, the phenomenon of superconductivity
found very little practical application due to the need to operate
at temperatures in the range of liquid helium. In the late 1980s
ceramic metal oxide compounds containing rare earth centers began
to radically alter this situation. Prominent examples of such
materials include YBCO (yttrium-barium-copper oxides, see
WO88/05029 and EPA-0281753), TBCCO (thallium-barium-calcium-copper
oxides, see U.S. Pat. No. 4,962,083) and TPSCCO
(thallium-lead-strontium-calcium-copper oxides, see U.S. Pat. No.
5,017,554). All of the above publications are incorporated by
reference for all purposes as if fully set forth herein.
[0006] These compounds, referred to as HTS (high temperature
superconductor) materials, exhibit superconductive properties at
temperatures sufficiently high enough to permit the use of liquid
nitrogen as a coolant. Because liquid nitrogen at 77 K (196.degree.
C./321.degree. F.) cools twenty times more effectively than liquid
helium and is ten times less expensive, a wide variety of potential
applications began to hold the promise of economic feasibility. For
example, HTS materials have been used in applications ranging from
diagnostic medical equipment to particle accelerators.
[0007] Currently one of the fastest growing applications for
superconductivity lies in the area of electronics and associated
microwave engineering, due to the astronomical growth in the
telecommunications industry and the increased use of consumer
electronics by the general population. In spite of the recent
advances in superconductivity, however, size, cost and power
requirements have limited the commercial use of this promising
technology in all but high-end applications such as space
instrumentation and military applications.
[0008] An essential component of many electronic devices, and
particularly in the communications field, is the filter element.
HTS filters have significant advantages in extremely low in-band
insertion loss, high off-band rejection and steep skirts due to the
extremely low radio frequency (RF) loss in the HTS materials.
[0009] However, the conventional transmission line HTS filters,
having conventional HTS resonators (such as strip line resonators)
as building blocks require a large substrate area due to the area
requirement that at least one dimension of the resonator is equal
to approximately a half wavelength (i.e. .lambda./2).
[0010] See, for example, U.S. Pat. No. 5,616,538 (incorporated by
reference for all purposes as if fully set forth herein). Thus,
conventional low frequency HTS filter design having is multiple
poles and coupled with conventional semiconductor electronic
components, such as gallium arsenide (GaAs) amplifiers, the
cryogenic coolers required to cool the HTS materials to below their
critical temperature (T.sub.c) are relatively large and require
power levels of at least 6 watts at 80 K at an ambient temperature
of 20.degree. C.
[0011] FIG. 1 is a prior art perspective view of such a
conventional cryogenic receiver. The overall integrated package
consists of several distinct elements. The connectors 110 are used
for bringing power and RF signals in and out of the cryoelectronic
section, which consists of a dewar assembly 120 containing
cryoelectronic components 130 such as RF filters and amplifiers.
The dewar assembly 120 is the vacuum cavity necessary to reduce
convective heat loading to the cryoelectronic components from
molecules within the dewar assembly 120. A cryogenic source, in
this case a cooler 140, provides the cooling for the cryoelectronic
section. The enclosure 150 is an outer package containing the
previously described elements as well as circuit boards 160 which
provide control functions for the cooler and other error or failure
detection and alarms, and a fan 170 for cooling the circuit boards
160.
[0012] The size of a conventional unit, as illustrated in FIG. 1,
is typically on the order of at least about 15 inches wide.times.20
inches long.times.10 inches deep (about 38.1.times.50.8.times.25.4
cm). The large size and weight of these conventional units stems
predominately from the cooling required due to the physical size of
the cryoelectronic section, power required for the amplifiers, and
additional convective heat flow from the RF transitions, normally
coaxial cables with connectors, from ambient conditions into the
dewar assembly 120. The physical size, weight and total operating
power supplied to the unit is thus dominated by the cooler 140 and
dewar assembly 120. For the conventional unit, the cooling lift
required per channel is about 1 W when operated at 20.degree. C.,
thus the total operational power needed for the cooler 140 alone is
>125 W.
[0013] Examples of conventional units are the Superfilter.TM.
Systems available from Superconductor Technologies Inc., Santa
Barbara, Calif. (see www.suptech.com for more information), and the
ClearSite.TM. systems available from Conductus Inc., Sunnyvale,
Calif. USA (see www.conductus.com for more information).
[0014] The large size and weight of these conventional units
substantially limits the application of this technology. One such
application is a tower top application in which a receiver
front-end is mounted onto an antenna of a cellular or similar base
station, such as those disclosed in U.S. Pat. No. 6,104,934
(incorporated by reference for all purposes as if fully set forth
herein). The size and cooling requirements of the disclosed
receiver are such that the cooling unit must be placed somewhere
adjacent the antenna, and is not combinable with the electronics
into an integrated unit.
[0015] For miniaturization purposes, the components comprising the
greatest real estate needed are the cooler 140, cryoelectronic
components 130 and dewar assembly 120.
[0016] One way to reduce the real estate requirements of a
cryoelectronic front-end receivers is to employ lumped element
architecture based on conventional HTS filters. These filters can
be made to operate at frequencies below 5 GHz with a somewhat more
compact physical size; however, filter performance of these
conventional lumped element HTS filters is generally limited by
intermodulation products and insertion loss.
[0017] The use of devices containing HTS filters presents other
design problems. For example, the interconnects typically utilized
to connect the cryogenic portion of the device (usually a dewar
containing the HTS filter under vacuum) to other electronic
components are long coaxial cables. These long cables, because of
their length, exhibit low thermal transmission, which is highly
desirable in a cryogenic system where keeping components cold is
critical. However, these long cable lines also exhibit RF losses,
thus contributing to degradation in RF performance (i.e. an
increase in the signal-to-noise ratio). To compound problems even
further, the long cables also require the dewar of the cryogenic
portion of the device to be larger in volume, which requires a
design capable of maintaining the larger vacuum necessary over the
life of the unit, which is more difficult to achieve.
[0018] There has been a long felt need, as well as numerous
attempts by persons of ordinary skill in the art, to reduce the
size of filter elements constructed of HTS materials. U.S. Pat. No.
6,108,569, incorporated by reference herein for all purposes as if
fully set forth, discloses the use of self-resonant spiral
resonators to reduce the size of HTS material filters and
concurrently solves cross-talk and connection problems. In spite of
the great potential for miniaturization afforded by significant
recent technological advances, the problems of vacuum degradation,
high thermal transmission, and high dissipated power semiconductor
devices, have resulted in less than optimum performance and yielded
increased cooling costs.
[0019] Furthermore, conventional cryogenic front-end receivers
require substantial time to manually tune the filters comprising a
critical function of the unit. Since the resonating filters in a
conventional filter construction do not each vary in a lock-stepped
fashion, each pole of the filter must be individually turned and
the turning of each pole affects every other pole in the filter
array. The turning process can typically take days to perform.
[0020] Moreover, conventional cryogenic front-end receivers also
suffer from outgassing of modules that adhere to the device walls
during the manufacturing process. Typically, this problem is
overcome by simply heating the device slowly over an extended
period of time to outgas the gases, such as residual oxygen,
nitrogen, carbon dioxide, argon, water vapor. The process normally
takes days to complete, because the temperatures necessary to
outgas the device walls in a short time period would damage the
compressor motor comprising part of the cryogenic unit.
[0021] The prior art lacks a cryogenic front-end receiver of
reduced size capable of being employed adjacent too or integrated
with a receiver and/or transmitter.
[0022] The prior art also lacks a cryogenic front-end receiver with
interconnections between the dewar and the cryogenic coolers
exhibiting an extremely low thermal transmission to further
thermally isolate the dewar.
[0023] The prior art additionally lacks a cryogenic front-end
receiver having interconnections employing a thermal break material
and a self-tuning reduced length for reducing RF losses and
improving degradation in RF performance.
[0024] The prior art further lacks a cryogenic front-end receiver
having reduced power consumption capabilities.
[0025] The prior art lacks a cryogenic front-end receiver employing
reduced substrate size resonating filters made of HTS materials and
resonating at frequencies below 5 GHz.
[0026] The prior art lacks a method for outgassing a vacuum dewar
employing differential heating of the dewar assembly.
[0027] The prior art lacks a cryogenic front-end receiver capable
of being tuned by varying the internal operating temperature of the
front-end receiver.
SUMMARY OF THE INVENTION
[0028] The present invention has been made in view of the above
circumstances and has as an aspect a cryogenic front-end
receiver.
[0029] A further aspect of the present invention can be
characterized as a cryogenic device, the device including a
cryogenic electronic portion and a non-cryogenic electronic portion
further including a thermal break section.
[0030] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described, the present invention can be characterized, according to
one aspect, as a cryogenic front-end unit, the unit including a
cryogenic electronic unit, wherein the cryogenic unit includes a
input signal interface and output signal interface. A cryogenic
cooler is in thermal communication with the cryogenic electronic
unit. The cryogenic unit further includes an input signal
interconnect that is connected to the input signal interface and an
output signal interconnect that is connected to the output signal
interface.
[0031] Another aspect of the present invention can be characterized
as a cryogenic device including a cryogenic electronic portion, a
non-cryogenic electronic portion and an interconnect connecting the
cryogenic and non-cryogenic electronic portions, wherein the
interconnect comprises a thermal break between cryogenic and
non-cryogenic electronic portions.
[0032] A further aspect of the present invention can be
characterized as a cryogenic device including a cryogenic
electronic portion contained within a vacuum dewar assembly, the
cryogenic electronic portion having an input end and an output end,
and an ambient to cryogenic input connector having an ambient end
passing through the vacuum dewar assembly to a cryogenic end
connected to the input end of the cryogenic electronic portion. A
cryogenic to ambient output connector with a cryogenic end
connected to the output end of the cryogenic electronic portion,
passes through the vacuum dewar assembly to an ambient end. A
cryogenic source is connected to the vacuum dewar assembly so as to
be in intimate contact with the cryogenic electronic portion, which
has an input end and an output end. The cryogenic electronic
portion includes at least one of a high temperature superconductor
filter element and a cryogenic active semiconductor circuit (such
as a low-noise amplifier). The input end of the cryogenic
electronic portion is connected to the cryogenic end of the input
connector and the output end of the cryogenic electronic portion is
connected to the cryogenic end of the output connector. In the
event that an active semiconductor circuit is used, that active
semiconductor circuit should produce a total dissipated power into
the cryogenic electronic portion of less than about 850 mW. The
cryogenic device has a maximum cooler lift of less than about 3 W
at 80 K at an ambient temperature of 20.degree. C.
[0033] Stated another way, this aspect of the present invention
relates to a cryogenic device comprising:
[0034] (1) a cryogenic electronic portion contained within a vacuum
dewar assembly, the cryogenic electronic portion having an input
end and an output end;
[0035] (2) an ambient to cryogenic input connector having an
ambient end passing through the vacuum dewar assembly to a
cryogenic end connected to the input end of the cryogenic
electronic portion,
[0036] (3) a cryogenic to ambient output connector having a
cryogenic end connected to the output end of the cryogenic
electronic portion, passing through the vacuum dewar assembly to an
ambient end; and
[0037] (4) a cryogenic source connected to the vacuum dewar
assembly so as to be in intimate contact with the cryogenic
electronic portion,
[0038] wherein:
[0039] (i) the cryogenic electronic portion comprises at least one
of a high temperature superconductor filter element and a cryogenic
active semiconductor circuit,
[0040] (ii) an active semiconductor circuit, if present, produces a
total dissipated power into the cryogenic electronic portion of
less than about 850 mW, and
[0041] (iii) the cryogenic device has a maximum cooler lift of less
than about 3 W at 80 K at an ambient temperature of 20.degree.
C.
[0042] Another aspect of the present invention can be characterized
as a cryogenic receiver in which the cryogenic electronic portion
of the above-mentioned cryogenic device comprises a high
temperature superconductor filter element having an input end and
an output end, and an active semiconductor circuit having an input
end and an output end, wherein the input end of the active
semiconductor circuit is connected to the cryogenic end of the
input connector via the high temperature superconductor filter
element. The input end of the filter element is connected to the
cryogenic end of the input connector and the output end of the
filter element is connected to the input end of the active
semiconductor circuit.
[0043] Stated another way, this other aspect relates to a cryogenic
receiver in which the cryogenic electronic portion of the
above-mentioned cryogenic device comprises a high temperature
superconductor filter element having an input end and an output
end, and an active semiconductor circuit having an input end and an
output end, wherein:
[0044] the input end of the active semiconductor circuit is
connected to the cryogenic end of the input connector via the high
temperature superconductor filter element;
[0045] the input end of the filter element is connected to the
cryogenic end of the input connector; and
[0046] the output end of the filter element is connected to the
input end of the active semiconductor circuit.
[0047] A still further aspect of the present invention can also be
characterized as a cryogenic receiver including a cryogenic
electronic portion contained within a vacuum dewar assembly, the
cryogenic electronic portion having an input end and an output end.
An ambient to cryogenic input connector having an ambient end
passes through the vacuum dewar assembly to a cryogenic end
connected to the input end of the cryogenic electronic portion, and
a cryogenic to ambient output connector having a cryogenic end
connected to the output end of the cryogenic electronic portion
passes through the vacuum dewar assembly to an ambient end. The
cryogenic receiver further comprises a cryogenic source connected
to the vacuum dewar assembly so as to be in intimate contact with
the cryogenic electronic portion. The cryogenic electronic portion
additionally includes a high temperature superconductor filter
element having an input end and an output end, and an active
semiconductor circuit having an input end and an output end. The
input end of the filter element is connected to the cryogenic end
of the input connector and the output end of the filter element is
connected to the input end of the active semiconductor circuit. The
output end of the active semiconductor circuit is connected to the
cryogenic end of the output connector and the active semiconductor
circuit produces a total dissipated power into the cryogenic
electronic portion of less than about 850 mW. The cryogenic
receiver has a maximum cooler lift of less than about 3 W at 80 K
at an ambient temperature of 20.degree. C.
[0048] Stated another way, this still further aspect of the present
invention also relates to a cryogenic receiver comprising:
[0049] (1) a cryogenic electronic portion contained within a vacuum
dewar assembly, the cryogenic electronic portion having an input
end and an output end;
[0050] (2) an ambient to cryogenic input connector having an
ambient end passing through the vacuum dewar assembly to a
cryogenic end connected to the input end of the cryogenic
electronic portion,
[0051] (3) a cryogenic to ambient output connector having a
cryogenic end connected to the output end of the cryogenic
electronic portion, passing through the vacuum dewar assembly to an
ambient end; and
[0052] (4) a cryogenic source connected to the vacuum dewar
assembly so as to be in intimate contact with the cryogenic
electronic portion,
[0053] wherein:
[0054] (i) the cryogenic electronic portion comprises:
[0055] (a) a high temperature superconductor filter element having
an input end and an output end, and
[0056] (b) an active semiconductor circuit having an input end and
an output end,
[0057] (ii) the input end of the filter element is connected to the
cryogenic end of the input connector,
[0058] (iii) the output end of the filter element is connected to
the input end of the active semiconductor circuit,
[0059] (iv) the output end of the active semiconductor circuit is
connected to the cryogenic end of the output connector,
[0060] (v) the active semiconductor circuit produces a total
dissipated power into the cryogenic electronic portion of less than
about 850 mW, and
[0061] (vi) the cryogenic receiver has a maximum cooler lift of
less than about 3 W at 80 K at an ambient temperature of 20.degree.
C.
[0062] The reader should note that when one "component" is
connected to another "component," only a sequence is implied and,
as such, other components may be connected in between. For example,
input connector-filter element-active semiconductor-output
connector is a sequence that can be interrupted by other
components. It is generally accepted practice to keep the number of
components in the vacuum dewar assembly to a minimum (e.g., to
reduce cooling requirements), so it is desirable to have a direct
connection from the input connector to the filter element, the
filter element to the active semiconductor device, and the active
semiconductor device to the output connector, as discussed in
further detail below.
[0063] With the combination of the HTS filters (particularly those
based on self-resonating spiral resonators), low dissipated power
semiconductor devices (that operate effectively under the required
cryogenic conditions) and the interconnects as mentioned above,
much smaller cryogenic devices (such as low noise receivers) can be
constructed and cooled by smaller cryogenic coolers requiring less
than about 3 watts of power, more preferably less than about 2
watts, and still more preferably about 1 watt or less, to cool the
cryoelectronic section to 80 K at an ambient temperature of
20.degree. C. In other words, the present invention provides
miniature cryogenic devices delivering optimum performance at
minimal size and cooling cost.
[0064] An additional benefit to the miniaturization enabled by the
present invention is a significant reduction in the heat budget of
the operating unit, which has a direct correlation to improved
cryocooler efficiency, increased system operational life and
reliability, and reduced energy consumption and operating
costs.
[0065] The present invention also provides a method of tuning a
cryogenic receiver comprising a high temperature superconducting
filter element, said cryogenic receiver being programmed to operate
at a specified operating frequency at a specified temperature,
comprising the step of altering the specified operating temperature
to induce a shift in the operating frequency of the cryogenic
receiver.
[0066] These and other features and advantages of the present
invention will be more readily understood by those of ordinary
skill in the art from the following detailed description. It is to
be understood that both the foregoing general description and the
following detailed description are exemplary and explanatory only
and are not restrictive of the invention, as claimed. For example,
it is to be appreciated that certain features of the invention
which are, for clarity, described below in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any subcombination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and together with the description,
serve to explain the principles on of the invention.
[0068] FIG. 1 shows a perspective view of a conventional integrated
cryogenic receiver;
[0069] FIG. 2 shows a front tilt perspective view of an embodiment
of a cryogenic receiver in accordance with the present
invention;
[0070] FIG. 2A shows a top perspective view of an embodiment of a
cryogenic receiver in accordance with the present invention;
[0071] FIG. 3 is a diagram of a microstrip transmission line with a
thermal break that can be used as part of an ambient to cryogenic
(or vice versa) connector;
[0072] FIG. 4 is a diagram of a waveguide structure with a thermal
break that can also be used as part of an ambient to cryogenic (or
vice versa) connector;
[0073] FIG. 5A shows a front-tilted perspective view of a
hermetically sealed cryogenic receiver of an embodiment of the
present invention;
[0074] FIG. 5B shows front-tilted exploded perspective view of the
embodiment shown in FIG. 5A of the present invention;
[0075] FIG. 5C is an expanded front-tilted perspective view of the
embodiment shown in FIG. 5B of those elements above cut line AA of
the present invention;
[0076] FIG. 5D is an expanded front-tilted perspective view of the
embodiment shown in FIG. 5B of those elements above cut line BB of
the present invention;
[0077] FIG. 5E is an expanded front-tilted perspective view of the
embodiment shown in FIG. 5B of those elements below cut line BB of
the present invention;
[0078] FIG. 6A depicts a schematic circuit diagram of a cellular
base station and cryogenic receiver including a main receiver
antennae and a diversity receiver antennae input configuration of
an embodiment of the present invention;
[0079] FIG. 6B depicts a schematic circuit diagram of a cellular
base station and receiver including a main receiver antennae and a
diversity receiver antennae input configuration multiple receiver
inputs and a bypass circuit configuration of an alternate
embodiment of the present invention;
[0080] FIG. 6C depicts a schematic circuit of a cellular base
station and receiver including a main receiver antennae and a
diversity receiver antennae input including a bypass circuit and
filter configuration of an alternate embodiment of the present
invention;
[0081] FIG. 6D depicts a schematic circuit diagram of a cellular
base station and receiver including a main receiver antennae input
and a bypass circuit configuration of an alternate embodiment of
the present invention; and
[0082] FIG. 6E depicts a schematic circuit of a cellular base
station and receiver including a main receiver antennae input
cryogenic receiver with multiple diplexers and a bypass circuit
configuration of an alternate embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0083] Reference will now be made in detail to the present
embodiments of the present invention, and examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts (elements).
[0084] The present invention overcomes the deficiencies of the
prior art as stated above and provides technical advantages over
the prior art in the areas of receiver size, power requirement,
thermal isolation, integration with a receiver or transmitter and
interconnections of reduced length for reducing RF losses.
[0085] It should be noted that the word "ambient", as used herein,
refers to conditions present in the surrounding environment, that
is, external to the dewar assembly. Ambient can, for example, refer
to normal room conditions, elevated temperature conditions present
as a result of a warm day and/or heat generated in the operation of
the equipment, or low temperature conditions existing in outer
space. This is opposed to "cryogenic" which refers to conditions
within the dewar assembly, that is, which are purposefully cooled
(with a cryogenic source) to maintain a desired low temperature for
optimal operation of the cryogenic electronic portion.
[0086] An improvement in the current state of the art, in
accordance with the present invention, is shown in FIGS. 2 and 3.
Depicted is a cryogenic receiver in which the cryogenic electronic
portion is, for illustration purposes, a combination of an HTS
filter element 205 connected to an active semiconductor circuit
210, and contained in a vacuum dewar assembly 215. The vacuum dewar
assembly 215 comprises a body 220 and, as a base, a cold plate 225
in intimate contact or in close proximity to both the cryogenic
electronic portion and a cryogenic source. In this embodiment the
cryogenic source is a miniature cryocooler 230. The vacuum dewar
assembly 215 is a self-contained unit comprising a housing or
enclosure. Dewar 215 includes a cover 520, as shown in FIG. 5.
Generally speaking, the vacuum dewar assembly 215 and cryocooler
230 are in close proximity to one another. In an alternate
embodiment dewar 215 and cryocooler 230 are in close proximity with
each other or formed as an integral unit or assembly (affixed to
one another) as depicted in FIG. 2.
[0087] The vacuum dewar assembly 215 may also contain, for example,
a thermal/infrared heat shield 235 covering at least the HTS filter
element 205, to further reduce the cooling and power requirements
of the cryogenic device.
[0088] In another embodiment the size of the cryogenic device can
be further reduced by placing a superconducting plate (not
depicted) on the underside of thermal/infrared heat shield 235
facing at least the HTS filter element 205 and further in intimate
contact with cold plate 225. The application of the superconducting
plate in the present embodiment assists in providing reduced
surface area for the cryogenic device element and thus further
reduce the cooling and power requirements of the device.
[0089] The superconducting plate can comprise, for example, a disk
with a film of an HTS material on at least the side of the disk
facing the HTS filter element 205. The disk typically is not in
physical contact the HTS filter element 205, but can be as close to
HTS filter element 205 without contact as the construction of the
dewar assembly allows. In order to be in contact with cold plate
225 but not HTS filter element 205, the disk can contain one or
more spacer legs or edges. Generally, the disk covers as much of
the cryogenic electronic portion as the construction of the dewar
assembly allows.
[0090] The superconducting plate can also be used for tuning
purposes such as, for example, disclosed in U.S. application Ser.
No. 09/727,009 (filed Nov. 30, 2000) (corresponding to WO01/41251),
which is incorporated by reference for all purposes as if fully set
forth herein.
[0091] A method that can be used for tuning is to modify the
temperature at which the unit is programmed to operate. For
instance a unit operating at 79.5 K versus 80.0 K can, depending on
filter design, introduce a <200 KHz shift in the operating
frequency of the HTS filter element 205. This temperature
adjustment can be made by varying the set point temperature of the
temperature controller for the cryocooler 230. Another way of
adjusting this temperature is to modify the temperature voltage
curve of a temperature measurement silicon diode or Resistive
Temperature Device (RTD) in the controller or adding an additional
resistance in series with the RTD or silicon diode and leaving the
voltage curve fixed.
[0092] In an alternate embodiment the operating temperature of the
cryogenic unit can be varied such that the unit could operate at a
second center frequency for emergency or back-up purposes in narrow
band applications. For instance, if a unit is designed to operate
at 1950 Mhz center point frequency with a bandwidth of 2 Mhz, the
operational range would be 1949-1951 Mhz. By varying the operating
temperature, the unit can be made to operate at center point
frequency of 1949 Mhz with a bandwidth ranging from 1948-1950 Mhz.
The temperature can also be varied in smaller increments to fine
tune the cryogenic unit, wherein the unit is operating slightly off
center of its intended center point frequency due to variations in
the manufacturing process.
[0093] The cryogenic electronic portion is connected to input
sources and output components 260 and 265, as illustrated in FIG.
5A, through, respectively, input and output connectors 240 and 245,
which transition from cryogenic conditions within the vacuum dewar
assembly 215 to ambient conditions outside the vacuum dewar
assembly 215.
[0094] As indicated above, the total cooling power required by the
cryogenic electronic portion directly affects the size, weight and
total operating power of a cryocooler functioning as the cryogenic
source. The larger the total cooling power required, the larger the
size, weight and total operating power of the cooler. The total
cooling power required is a function of a number of factors
including, but not limited to, the infrared heating of the cold
surfaces, conductive heat flow from gas molecules from warm
surfaces to the cold surfaces, the power dissipated by the active
semiconductor circuit 210 into the vacuum dewar assembly 215, and
the conductive heat leak due to the connectors 240 and 245.
Infrared heating of the cold surfaces can be reduced by altering
the size of the cold surfaces and the temperature at which the cold
surfaces are held relative to ambient. Filter size and packaging
tend to dominate the size of the cold surfaces.
[0095] In addition to the features detailed above, the present
invention, as depicted in FIGS. 2 and 2a, employs a number of other
features to reduce the size and total cooling power required to
maintain the cryogenic electronic portion at an optimal operating
temperature.
[0096] As can be seen from FIGS. 2 and 2a, the connectors 240 and
245 are made integral to the vacuum dewar assembly 215 as opposed
to a separate module 110 as depicted in Prior Art FIG. 1. The
connectors 240 and 245 comprise jumpers 250 and 255 connected,
respectively, to input and output hermetic connectors 260 and 265.
The hermetic connectors 260 and 265 provide the electrical
transition out of the vacuum dewar assembly 215 and utilize, for
example, "O"-rings, soldered seals and/or direct glass to metal
seals to maintain the vacuum seal within the vacuum dewar assembly
215. Direct glass to metal seals generally provide a suspension
seal. The portion of hermetic connectors 260 and 265 outside of the
dewar assembly can, for example, be in the form of coaxial or other
well-known connectors, such as fiber-optic (in order to use a fiber
optic connection would require conversion of the RF signal to an
encoded light signal), twisted pair etc., depending on the type of
connection required.
[0097] Jumpers 250 and 255 transition from cryogenic temperatures
at the connections to the cryogenic components to ambient
temperatures at the connections to the hermetic connectors 260 and
265. The jumpers 250 and 255 can be of conventional construction,
depending on the end use, for example, a microstrip transmission
line for lower frequency signals or a waveguide for higher
frequency signals. In an alternate embodiment the interconnects
(i.e. jumpers 250 and 255) are formed on a thermal break material
to reduce thermal gain from the ambient. For example, jumpers 250
and 255 can be formed as a microstrip transmission line on a
substrate such as alumina, glass (fused silica, quartz, MACOR,
etc.), fiberglass epoxy, or aerogel whose thickness is >0.002
inches (>0.051 mm). The substrates utilized in the present
invention are constructed of very low thermal conductive materials
that function as effective thermal breaks, such as fused silica
(thermal conductivity (K) of about 1.5 W/m-K) or silica-based
aerogels (K values of from about 0.02 W/m-K (300 K, 1 atmosphere)
to 0.004 W/m-K (300 K, vacuum)). In an alternate embodiment higher
thermal conductivity substrates are contemplated that also include
a thermal break material of some type. Skilled artisans will
appreciate that numerous thermal breaks may be employed and not
depart from the teachings of the present invention.
[0098] An example of this embodiment is depicted in FIG. 3, wherein
an interconnect includes an inserted thermal break. Substrate
material 320 contains an insert 330 of a low thermal conductivity
material (such as aerogel) between the colder end 310 and warmer
end 340 of the conductive strip on the microstrip line. In a
similar context, a waveguide cavity can be constructed of a low
thermal conductive material such as aerogel that is metallized on
at least the interior surface, or can be constructed of a standard
material such as a metal with an inserted thermal break. An
embodiment of the inserted thermal break material is depicted in
FIG. 4, where substrate material 410 contains an insert 420 of a
low thermal conductive material (such as aerogel), metallized on at
least the interior surface 430, between the colder end 440 and
warmer end 450 of the waveguide cavity.
[0099] It should be noted that, while thermal breaks additionally
reduce thermal conductivity from the ambient, low thermal
conductivity materials should be first utilized to avoid as much
conductive heat gain in the cryogenic electronic portion as
possible. A combination of low thermal conductivity materials and
well as the application of a thermal breaks in the design generally
provides the best of both, but at a cost of increased size and thus
may not be practical in all applications. Because conductive heat
flow is inversely proportional to the length of the conductive
material, jumpers 250 and 255 (see FIG. 5D) can be lengthened,
although this may lead to increased signal losses and an increase
in the size of the vacuum dewar assembly. The trade off between RF
loss and lower thermal gain, however, can be optimized by the
person of ordinary skill in the art based on the materials and
dimensions of construction of the jumpers 250 and 255.
[0100] A detailed description of the cryogenic receiver will now be
made with references to FIGS. 5A-5E.
[0101] FIG. 5A depicts a front-tilted perspective view of the
hermetically sealed cryogenic receiver of the present invention and
FIG. 5B depicts a front tilted exploded perspective of FIG. 5A. The
assembly of the cryogenic receiver will now be made with references
to FIGS. 5A-5E, respectively.
[0102] The lid 520 of the vacuum dewar assembly 215 is capable of
being attached to the dewar body 220 by welding, soldering or
mechanical connection. As shown in FIG. 5B, screws 522 are inserted
through holes in lid 520 and engage body 220 via screw holes 523.
An "O-ring" seal 530 is placed in grove 222 and forms a seal when
lid 520 is engaged via screws 522 with body 520.
[0103] The O-ring seal 530 is capable of being made of, but is not
limited to, rubber, a synthetic material or metal as required to
maintain the vacuum conditions. In an alternate embodiment, the
attachment of the lid 520 is accomplished by soldering and O-ring
seal 530, typically made of metal. In a further embodiment of the
present invention, wherein some of the components are heat
sensitive, thereby rendering conventional welding or soldering
techniques difficult to utilize, a "cold" welding technique is
capable of being employed in which a malleable metal O-ring (such
as one constructed of indium) is placed between the lid 520 and
dewar body 220, and the seal is tuned by application of pressure to
lid 520 to compress the O-ring 530 into grove 22.
[0104] Getter 525, which absorbs impurities left behind once the
housing/body 220 has been evacuated via vacuum tube 266, are held
in place by fastener 526 with bolt 527. In this embodiment there
are four getters 525 as illustrated, but any number will do as long
as the getter has sufficient capacity to absorb the expected
impurities encumbered over the life of the cryogenic unit.
[0105] Cold plate 225 is housed within body 220 having internal
cavity area 555 formed within. Alignment tool 510 is utilized to
align cold plate 225 with the body 220 of the unit. Tool 510 is
removed once cold plate 225 is adequately secured within cavity
555. Filter 205 and amplifier 210 are placed on cold plate 225 or
in close proximity to cold plate 225. RF shield 235 is placed in
communication with cold plate 225 and shields filter 205 and
amplifier 210. Brackets 535, 539 and 541 are utilized to hold cold
plate 225, filter 205 and amplifier 210 (i.e. front-end receiver)
in their respective positions within cavity 555. All cryogenic and
non cryogenic surfaces inside the cavity 555 are preferably plated
with a highly reflective material such as, for example, gold,
platinum, silver or similar type metal (i.e., highly conductive
metal with low reactivity to the environment). Jumpers 250 and 255
are in communication with filter 205 and amplifier 210.
[0106] Various inputs and outputs are made accessible to the
receiver via port 260 (Rf.sub.in), 265(Rf.sub.out) and 270
(DC.sub.in). Temperature indication inside of the unit is provided
via port 564.
[0107] Cold finger 572 extends through central opening 554 of
cavity 555 and is in thermal communication with cold plate 225.
Cold finger 572 extends from the top 280 of dewar assembly 215
(i.e. heat sink region). O-ring 570 forms a seal with area 282 when
bottom plate 565 is secured via bolts or screws to bolt or screw
holes 290 formed in dewar top portion 280.
[0108] As an example of taking a number of heat budget factors into
consideration, by keeping the HTS filter element <40 cm.sup.2 in
size, the active semiconductor circuit <350 mW dissipated power,
and the thermal leak produced by the jumpers (a microstrip
transmission line on a 5 cm long, 0.005" (0.127 mm) thick, and 5 mm
wide fused silica substrate) to <100 mW, one can reduce the
cooling capacity required per channel to <600 mW at 80 K at
20.degree. C. ambient temperature.
[0109] As indicated previously, jumpers 250 and 255 are preferably
a microstrip transmission line formed on a fused silica or silica
aerogel substrate, which are very low thermal conducting substrates
and can effectively be used in a long life vacuum environment due
to their absence of outgassing materials which could degrade the
vacuum over time and increase the heat load to the cooler due to
thermal conduction by the outgassed materials. Additionally, an
added benefit to an aerogel substrate is the material is
essentially a large surface area silica material. Silica surfaces
tend to absorb water vapor, thus improving the quality of the
vacuum. Silica materials such as fused silica or silica aerogel are
optimum electrical and thermal interfaces and act as a "getter"
helping to maintain the required vacuum in the dewar and thus
improving vacuum reliability.
[0110] In an alternate embodiment, jumpers 250 and 255 comprise a
microstrip transmission line (such as a 1.5 .mu.m thick gold line)
deposited on one side of a fused silica substrate which is
typically 5 cm long, 2.5-5 mm wide and 0.005 inches (0.127 mm)
thick, with the other side of the substrate having a grounding
layer (e.g., a conductive metal such as gold) thereon.
[0111] Conventional waveguide cavities made entirely out of
conductive metals tend to produce too large a thermal leak to the
cryogenic electronic portion for applications in the frequency
range of less than approximately 2 Ghz. Thus, it is recommend (when
a waveguide is applicable) to construct the waveguide cavity from a
metal coated substrate having a low thermal conductivity (e.g.,
aerogel) or, at a minimum, to insert a "thermal break" of metal
coated aerogel material into the waveguide cavity structure to
reduce the conductive thermal transfer.
[0112] The HTS filter element may be one or more mini-filter(s)
capable of meeting the size limitations imposed by the
configuration of the vacuum dewar assembly. Preferred mini-filters
are disclosed in previously incorporated U.S. Pat. No. 6,108,569,
and are based on self-resonant spiral resonators of varying shapes,
including but not limited to rectangular, rectangular with rounded
corners, polygon, hairpin, oval and circular. The size of the
self-resonant spiral resonator is reduced by reducing the width of
the gap between adjacent lines and reducing the center open area in
the spiral resonator. The resonant frequency (f) of the
self-resonant spiral resonator can be changed by changing the
length of the spiral line (.lambda.) (wherein.
f.apprxeq..lambda./2), changing the gap width between the adjacent
lines of the spiral and by placing a conductive tuning pad at the
center of the spiral. The last method can be used as fine frequency
tuning. Frequency tuning can also be accomplished through the use
of an HTS plate positioned above the filter element, and operating
temperature variations, as discussed above.
[0113] The design of the HTS filter element further depends on a
number of factors such as, for example, the purpose of the filter
element (e.g., band pass or band reject), operating frequency,
sensitivity and other factors recognizable by those of ordinary
skill in the art. Based on these factors, one of ordinary skill in
the art can design an appropriate filter element using the guidance
provided in previously incorporated U.S. Pat. No. 6,108,569 and
standard design tools such as commercially available software
packages (for example, Sonnet EM Suite available from Sonnet
Software, Inc.).
[0114] In various embodiments, the superconducting materials of the
HTS filter element (and other components comprising superconducting
materials) have a transition temperature, T.sub.c, greater than
about 77 K. In addition, substrates for the HTS filter element
should have a dielectric material lattice matched to the HTS film
deposited thereon, with a loss tangent less than about 0.0001.
Specific preferred materials include (but are not limited to) the
following:
[0115] HTS materials--one or more of YBa.sub.2Cu.sub.3O.sub.7,
Tl.sub.2Ba.sub.2CaCu.sub.2O.sub.8,
[0116] TlBa.sub.2Ca.sub.2Cu.sub.3O.sub.9,
(TlPb)Sr.sub.2CaCu.sub.2O.sub.7 and
(TlPb)Sr.sub.2Ca.sub.2Cu.sub.3O.sub.9; and
[0117] substrate materials--one or more of LaAlO.sub.3, MgO,
LiNbO.sub.3, sapphire and quartz.
[0118] In addition to the substrate and HTS materials, various
buffer and orientation layers can be utilized where appropriate,
such as (for example) disclosed in U.S. Pat. Nos. 5,508,255 and
5,262,394, both of which are incorporated herein for all purposes
as if fully set forth.
[0119] The input and output couplings of the spiral resonator-based
mini-filter have two generally accepted configurations. One is a
parallel line configuration, which comprises a transmission line
with one end connected to the mini-filter's connector via a normal
metal contact pad on top of the line, the other end of the line
being extended to be close by and in parallel alignment with the
spiral line of the first resonator (for the input circuit) or the
last resonator (for the output circuit) to provide the input or
output couplings for the filter. The other is an inserted line
configuration, which comprises a transmission line with one end
connected to the mini-filter's connector via a normal metal contact
pad on top of the line, with the other end of the line being
extended to be inserted into the split spiral line of the first
resonator (for the input circuit) or the last resonator (for the
input circuit) to provide the input or output couplings for the
filter. Further details can be found by reference to previously
incorporated U.S. Pat. No. 6,108,569.
[0120] The inter-resonator couplings between adjacent spiral
resonators in the mini-filter are provided by the overlapping of
the electromagnetic fields at the edges of the adjacent resonators.
The coupling strength can be adjusted by changing the longitudinal
distance between adjacent spiral resonators, changing the
orientation of the spiral resonators and shifting the spiral
resonator's location along the transverse direction. The last way
can be used for fine adjustment of the coupling strength. Again,
further details can be found by reference to previously
incorporated U.S. Pat. No. 6,108,569.
[0121] The mini-filter is preferably in intimate contact with the
cold plate 225 of the vacuum dewar assembly 215 via a metallized
ground plane on the "back" side of the mini-filter substrate,
further details of which can be seen by reference to previously
incorporated U.S. Pat. No. 6,108,569. The mini-filter and active
semiconductor circuit can be affixed to the cold plate 225, for
example, by using conductive epoxy or solder between the metallized
ground plane and the cold plate 225, or by resistive welding of the
metallized ground plane to the cold plate 225, or simply by
mechanical means such as screws.
[0122] The active semiconductor circuit 210 may be connected to the
filter element 205 by any conventional means such as soldering,
wire bonding or parallel gap welding, but is typically connected by
a short metal wire which is attached by solder, thermal compression
bonding or resistive welding from contact pads (not shown) on the
active semiconductor circuit 210 to the contact pads not shown) on
the filter element 205.
[0123] The active semiconductor circuit 210 may, for example, be
one or a combination of amplifiers, mixers, analog-to-digital
converts and digital processors. Typically for a receiver, the
active semiconductor circuit 210 will comprise an amplifier such
as, but not limited to, an InP or GaAs HEMT, HBT, pHEMT, nHEMT,
III-V heterostructure or monolithic microwave integrated circuit
(MMIC) amplifier. Such amplifiers are well known in the art. An InP
or GaAs pHEMT or nHEMT amplifier is typically preferred.
Commercially available examples are available from a number of
sources such as, for example, Miteq Inc. (Hauppauge, N.Y. USA,
Model No. SAFS1-01500200-08-CR-S) and Microwave Technology Inc.
(Fremont, Calif. USA, Model No. SGO-7446, Part No. 01-50-660).
[0124] The cryogenic source of the cryogenic device provides
cooling to the cryogenic electronic components. The cryogenic
source can, if the device is deployed in outer space, be the
ambient outer space conditions, but the cryogenic source is
typically a miniature cryocooler unit 230 of the appropriate size
and power requirements. Such miniature cryocoolers are typically
Stirling cycle machines such as those described in U.S. Pat. No.
4,397,155, EP-A-0028144, WO90/12961 and WO90/13710 (all of which
are incorporated by reference as if fully set forth herein).
[0125] The above-described cryogenic devices can be utilized in a
numbers of fields, and particularly in the wireless communications
field in band-pass and band-reject filter applications. One such
area is in wireless communication base station receiver front-end
in ground-based and tower top applications. General details on such
uses can be found in the previously incorporated references. In
such uses, the cryogenic front-end receiver of the present
invention can be an integrated package similar in certain general
respects to conventional units (such as depicted in FIG. 1), in
that it comprises a cryogenic electronic unit and control circuitry
in a single enclosure, which can be further electrically connected
to other components of the base station either directly or
remotely. Because of the inventive features of the cryogenic
electronic unit described herein, however, the size, weight and
power requirements of a front-end receiver in accordance with the
present invention can be significantly reduced, in some cases an
order of magnitude or greater, while maintaining equivalent or even
better performance, as compared to such conventional units.
[0126] The significant reduction in size, weight and power
requirements makes the cryogenic devices in accordance with the
present invention ideal for integration into, for example, antenna
assemblies, satellite base stations, radar arrays and RF
receivers.
[0127] A specific example of such includes an integrated antenna
assembly, wherein the cryogenic device and at least one antenna of
a wireless base station are assembled as an integrated unit. In
contrast to systems depicted in previously incorporated U.S. Pat.
No. 6,104,934, wherein the cryogenic electronic portion of the unit
can be in close proximity to the antenna, the present inventions
allows an integrated unit with the antenna even further reducing
noise contamination to the system.
[0128] FIGS. 6A-6F represent several embodiments of a wireless
communication base station and self-tuning cryogenic front-end
receiver. FIG. 6A depicts a schematic diagram of a wireless base
station cryogenic unit configuration including diversity antennae
605 and main receiver 610. Diversity antenna 605 provides
additional gain of approximately 3 db over that of the signal
received via main receiver 610. Main receiver 610 receives and
transmits simultaneously, wherein diversity receiver only receives
signals. The corresponding signals are transmitted directly to
cryogenic unit 630 in the case of the diversity antennae 605 and to
diplexer 615 for the main receiver 610 before being forwarded to
the cryogenic unit 630.
[0129] Diplexer 615 is comprised of filters 620 and 625 for
separating the signal into its transmission signal component and
the received signal component. The received signal component is
then transmitted to the cryogenic unit 630. In the general case the
transmission signal is not processed through the cryogenic unit,
because of heating capacity constraints, but otherwise can be
processed by the cryogenic unit 630. In this embodiment cryogenic
unit 630 is comprised of HTS filters 635 and 645 with amplifiers
640 and 650 respectively. Generally, amplifiers are
low-noise-amplification (LNA) amplifiers. The received signal is
then forward to amplifiers 655 and 660 respectively and in the case
of the main receiver 610 electrical pathway, diplexed with the
transmission component of the signal by diplexer 665 and then is
transmitted to the remaining sections of the base station.
[0130] FIG. 6B depicts a second embodiment of the wireless base
station and cryogenic unit configuration of the present invention.
FIG. 6B differs from the embodiment depicted in FIG. 6A in that
cryogenic units 630 and 680 are dedicated to the main receiver 610
signal and the diversity antennae 605 signal, respectively. This
configuration provides for added reliability and also includes
bypass circuit 642 and 692, respectively to further insure that if
one or both cryogenic units 630 and 680 fail that the base station
will still receive and process the RF signals.
[0131] FIG. 6C depicts a third embodiment of the wireless base
station and cryogenic unit configuration of the present invention,
wherein the diversity antennae 605 signal is the only signal that
is processed by cryogenic unit 630. Additionally, bypass circuit
642, further includes a filter 644, thus providing additional
reliability and filtering along this path, not provided in either
of the embodiments depicted in FIGS. 6A and 6B.
[0132] FIG. 6D depicts a fourth embodiment of the wireless base
station and cryogenic unit configuration of the present invention.
FIG. 6D does not include the diversity antennae of the embodiments
depicted in FIGS. 6A-6C. This embodiment includes bypass 642
without filter 644, but functions in all other respects as the
previous embodiments.
[0133] FIG. 6E depicts a fifth embodiment of the wireless base
station and cryogenic unit configuration of the present invention.
FIG. 6E differs from the fourth embodiment in that it includes
diplexer 665 in the circuit before the signal is forward to the
remaining sections of the base station.
[0134] FIG. 6F depicts a sixth embodiment of the wireless base
station and cryogenic unit configuration of the present invention.
FIG. 6F depicts a configuration wherein only the diversity antennae
605 signal is processed by cryogenic unit 630. The embodiment
further includes bypass circuit 642 with bypass filter 644 and a
diplexer 665 before transmitting the processed signal to the
remaining sections of the base station.
[0135] The reader should note that the above embodiments are
exemplary and are not intended to limit the scope of the present
invention. The present invention can be applied in any environment
wherein RF signals (and particularly microwave) are received and
broadcast, such as but not limited to, radar arrays, satellite
installations (home or commercial) and wireless and cellular base
stations. In such uses, the cryogenic devices in accordance with
the present invention can provide one, two, three or even
significantly higher db gains in an output signal-to-noise ratio,
depending on the use and component configuration.
[0136] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present invention
and in construction of this invention without departing from the
scope or intent of the invention. Other embodiments of the
invention will be apparent to those skilled in the art from
consideration of the specification and practice of the invention
disclosed herein. It is intended that the specification and
examples be considered as exemplary only, with a true scope and
spirit of the invention being indicated by the following
claims.
[0137] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims.
* * * * *
References