The development and implementation of a C-band exciter for use with the Block IV Receiver-Exciter Subsystem at Deep Space Station 14 (DSS-14) has been completed. The exciter supplements the standard capabilities of the Block IV system by providing a drive signal for the C-band transmitter while generating coherent translation frequencies for C-band (5-GHz) to S-band (2.2- to 2.3-GHz) Doppler extraction, C-band to L-band (1.6-GHz) zero delay measurements, and a level calibrated L-band test signal. Exciter functions are described, and a general explanation and description of the C-band uplink controller is presented

Rowan, D. R.

English

NASA Technical Reports Server

N89-27901
TDA Progress Report 42-97 January-March 1989
The DSS-14 C-Band Exciter
D. R. Rowan
Radio Frequency and Microwave Subsystems Section
The development and implementation of a C-band exciter for use with the Block IV
Receiver-Exciter Subsystem at Deep Space Station 14 (DSS-14) has been completed.
The exciter supplements the standard capabilities of the Block IV system by providing
a drive signal for the C-band transmitter while generating coherent translation frequencies
for C-band (5-GHz) to S-band (2.2- to 2.3-GHz) Doppler extraction, C-band to L-band
(1.6-GHzJ zero delay measurements, and a level calibrated L-band test signal. Exciter
functions are described, and a general explanation and description of the C-band uplink
controller is presented.
I. Introduction
The C-band (5-GHz) exciter was developed to function
with the Block IV Receiver-Exciter Subsystem and L-band
(1.6-GHz) to S-band (2.2- to 2.3-GHz) upconverter to pro-
vide two-way C/L-band Doppler and ranging capabilities.
Additional requirements concerning ranging calibration and
antenna pointing were met with the development of a C-to
L-band portable zero delay device and a C-band downcon-
verter assembly.
The overall functionality of the C-band exciter as it inter-
faces with the Block IV equipment is discussed in Section II
and the detailed hardware designs are explained in subsequent
sections.
II. C-Band/Block IV Interfaces and
Functional Relationships
The C-band exciter was designed to make use of as much
of the Block IV capabilities and hardware as possible. Modi-
fications were performed to the various Block IV assemblies
to allow the C-band interfaces to be installed as shown in
Fig. 1. These interfaces allow the following Block IV compo-
nents to be used by the C-band exciter: S-band exciter refer-
ence synthesizer, range phase modulator, S-band exciter
multiplier chain, S-band Doppler extractor, and programmable
attenuator assembly.
The output of the Block IV exciter reference synthesizer,
located in the RCV-421 exciter rack, has been routed to the
RF drawer assembly (RCV-492) in the combined uplink con-
trol rack (TXR-191). During the Block IV mode of operation,
the reference signal is passed through a transfer relay and sent
back to the Block IV exciter to resume its normal path. During
the C-band mode of operation, the reference signal is sent to
a distribution amplifier in the RF drawer assembly, which
distributes the reference signal to the C-band uplink compo-
nents and sends the reference back to the Block IV exciter to
be multiplied up to S-band. These control relays are activated
by the combined C-band uplink controller and are indepen-
dent of the Block IV receiver-exciter controller.
The Block IV Doppler translator assembly has been modi-
fied to route the S-band Doppler reference signal to the C-band
292
https://ntrs.nasa.gov/search.jsp?R=19890018530 2020-03-20T01:52:21+00:00Z
exciter assembly. During Block IV mode, a relay in the C-band
exciter returns the signal to the Block IV Doppler translator,
where it continues on its normal path. During the C-band
mode, the C-band exciter provides a substitute S-band Doppler
reference that is coherently derived from the C-band exciter
drive signal. The resulting Doppler that is extracted by the
Block IV Subsystem is therefore C- to L-band Doppler.
The Block IV programmable attenuator assembly (RCV-
481) has been modified to provide input and output switch-
ing relays on the S-band attenuator. These relays are con-
trolled by the C-band uplink controller and allow the S-band
attenuator to be used to attenuate the L-band coherent test
signal from the C-band exciter. During the Block IV mode,
the relays are set to allow the normal S-band translator signal
from the Block IV Doppler translator to pass through the
programmable attenuator. During the C-band mode, the relays
pass the L-band test signal through the S-band attenuator
before the signal is sent to the Microwave Subsystem. It should
be noted that although the control relays are configured via
the C-band controller, the attenuation level of the S-band
attenuator is controlled via the Block IV receiver-exciter
controller and the desired attenuation level must be set through
the LMC console or a local terminal attached to the receiver-
exciter controller.
The S-band exciter assembly (RCV-441) has been modi-
fied to provide an S-band exciter drive output to the C-band
exciter. This signal, along with the exciter reference signal
from the RF drawer assembly (RCV-492), is used to synthe-
size the C-band exciter drive signal. Due to the shared configu-
ration between the Block IV and C-band equipment, the
S-band drive signal was arranged so that only one exciter
(either S-band or C-band) could be operated at a time. This
was accomplished by using an existing Block IV control relay
in the S-band exciter assembly (RCV-441K3) that functions to
turn the S-band exciter drive on and off. In the OFF position,
the relay normally terminates the S-band drive signal into a
50-ohm load. The load was removed and the output was
routed through an isolator to a port on the side of the S-band
exciter assembly. This output feeds the C-band exciter assem-
bly when the S-band exciter drive is turned off at the Block IV
controls. It should be noted that this is the only Block IV/
C-band interface relay that is not controlled by the C-band
controller. It then becomes an operational responsibility to
ensure that the S-band exciter drive is in the OFF state before
the C-band mode is entered.
III. C-Band Exciter Drive Generation
The C-band exciter uses the Block IV S-band exciter fre-
quency reference, which is 1/116 the desired C-band exciter
frequency (Fc). The frequency multiplication is accomplished
using hardware in both the Block IV and C-band exciter assem-
blies as shown in Fig. 2.
In the C-band mode, the exciter reference frequency (Fc/
116) is directed along two paths to the C-band exciter assem-
bly (RCV-130). The first path is through the RF drawer assem-
bly (RCV-492) in the C-band control rack (TXR-191). The
exciter reference is passed through a distribution amplifier
and sent to the C-band exciter assembly, located in the antenna.
The second path is through the S-band exciter multiplication
path, where the reference is multiplied by 48 (48 Fc/116).
The C-band exciter assembly then takes the reference fre-
quency from the RF drawer assembly, multiplies it by 68,
and mixes the results (68 Fc/ll6) with the output from the
S-band exciter (48 Fc/ll6), with the sum of the two fre-
quencies (Fc) being selected at the output. The C-band exciter
frequency is then passed through several stages of amplifica-
tion to achieve the desired output.
IV. C-Band Exciter Functions
A. Coherent L-Band Test Signal
The C-band exciter provides a coherent C- to L-band test
signal at a fixed level that is subsequently passed through the
RCV-481 programmable attenuator assembly, allowing level
control. The L-band test signal is generated by mixing the
C-band exciter frequency (Fc) with a coherently generated
conversion frequency (453 Fc/681) to create the desired
output (228 Fc/681).
The RCV-130A4 coherent translator module in the C-band
exciter provides the mixing and selection of the frequencies.
Two sources of C-band (Fc) signal are provided for conversion,
and selection is determined by the operator at the uplink
control rack (TXR-191). A sample of the exciter output drive
is provided by a coupler in the A3 exciter mixer module, and
a sample of the C-band transmitter output is provided by a
high-power coupler in the Microwave Subsystem. Either of
these sources may be selected to be converted to L-band.
The conversion frequency (453 Fc/681) is generated in the
C-band exciter using the exciter reference (Fc/116) as shown
in Fig. 2. The reference is first passed through the A6 fre-
quency shifter module, where it is multiplied by 4379/681.
This output is multiplied by the X12 frequency multiplier in
the A7 module to achieve the 453 Fc/681 required. This out-
put is sent to the A4 coherent translator module, where the
C- to L-band conversion occurs.
B. Zero Delay Reference Signal
To provide an external C- to L-band conversion frequency
to be used by the C- to L-band portable zero delay device
293
(C-PZDD), an additional output of the A7-X12 frequency
multiplier module is provided to a port on the C-band exciter
assembly. The conversion frequency (453 Fc/681 ) is used by
the C-PZDD to convert the output of the C-band transmitter
signal to L-band in the same manner as the coherent translator
in the C-band exciter. The C-PZDD is a calibrated device that
is used to determine the equipment delays in the C-band
uplink/L-band downlink for ranging calibrations.
C. C- to S-Band Doppler Reference Signal
During the Block IV mode of operation, the S-band Dop-
pler reference from the Block IV Doppler translator assembly
(RCV-431) is routed through the C-band exciter assembly
(RCV-130) as shown in Fig. 1. During the C-band mode of
operation, the Block IV Doppler reference signal is eliminated
and a coherent C- to S-band Doppler reference is generated by
the C-band exciter and sent to the Block IV Doppler trans-
lator assembly.
The L- to S-band upconverter assembly (RCV-103) is used
to translate incoming L-band receive frequencies to S-band
(Fig. 3); the S-band signal is sent to a Block IV receiver. With
the receiver locked to the L- to S-band signal, the local oscil-
lator from the receiver can then be used by the Block IV Dop-
pler translator assembly (RCV-431) to extract the C- to L-band
Doppler from the C- to S-band Doppler reference.
The C- to S-band Doppler reference is generated in the
C-band exciter using the exciter reference frequency (Fc/116)
as shown in Fig. 2. The exciter reference is split by the A6
frequency shifter module and sent to several outputs. An out-
put (Fc/116) is provided to the A8-X116 frequency multiplier,
which creates an equivalent C-band exciter frequency (Fc).
The C-band output is sent to the A9 Doppler reference genera-
tor, where it is mixed with a C- to L-band conversion fre-
quency (453 Fc/681) from the AT-X12 frequency multiplier.
The L-band output (228 Fc/681) is mixed with the output of
the All-Xal frequency multiplier (620 MHz) to create the
S-band Doppler reference signal.
V. Portable Zero Delay Device
To provide a method of measuring the ranging equipment
delays in the C- to L-band link, a calibrated zero delay device
was constructed. The device performs essentially the same task
as the C- to L-band test translator in the exciter by taking a
sample of the uplink C-band signal and coherently translating
the signal to L-band, where it is injected into the receive path.
Since the delays of the C-PZDD have been measured and are
known, its contribution to the overall delay of the link can be
eliminated, with the remaining delay being attributed to the
station equipment.
The C-PZDD is connected into the C-band exciter/Block IV
receiver-exciter as shown in Fig. 4. A sample of the transmit-
ter's C-band output (Fc) is taken off a high-power coupler
and mixed with the zero delay output (453 Fc/681) from the
C-band exciter. The difference of the two inputs (228 Fc/681 )
is selected by a filter and sent to a coupler that injects the
signal into the L-band receive path.
Vl. C-Band Converter Assembly
To help refine the pointing accuracy of the antenna during
C-band operations, a C-band converter assembly was provided
to allow the antenna pointing to be evaluated at C-band fre-
quencies. The converter accepts a C-band spectrum and down-
converts the signals to an IF centered around 200 MHz. This
200-MHz IF is sent to a square law detector, where the noise
power in the spectrum is measured. This allows the antenna
to be trained upon a known C-band noise source using the
square law detector to fine tune the pointing of the antenna
by maximizing the signal strength. The antenna position
coordinates can then be interpreted using the known location
of the celestial source.
VII. Controller
The C-band uplink controller (HP Vectra Computer) was
conceived as a stand-alone system providing monitor and con-
trol functions from a combined C-band uplink control rack
(TXR-191) located in the SPC-IO area. The controller was
designed to configure all the new C-band equipment as well as
provide status indications. The C-band controller manipulates
the exciter, microwave, and transmitter components of the
C-band uplink (Fig. 5), but cannot monitor or control any of
the subsystems interfacing with those assemblies due to the
lack of an LMC/CMC interface.
The subassemblies of the C-band uplink are designed to
interface with a commercial Hewlett-Packard data acquisi-
tion unit (DAU) that provides monitor and control of the
assemblies. A DAU is located in the antenna and relays infor-
mation to and from the controller in the SPC area via a fiber
optic system, An additional DAU in the control rack provides
monitor and control of the SPC-located equipment.
VIII. Physical Configurations
The C-band exciter assembly (RCV-130) is housed in a
single wall-mounted Hoffman enclosure that measures approxi-
mately 30 in. by 24 in. by 9 in. The enclosure contains the RF
modules, and associated monitor, control, and power supply
hardware as shown in Fig. 2. Interfaces to the box are made
294
via feedthrough connectors mounted through an interface
plate in the side of the box. Multi-pin connectors provide
monitor and control interfaces and N-type connectors provide
RF ports.
The RF drawer assembly (RCV-492) and the power supply
drawer assembly (RCV-493) are both mounted in the com-
bined uplink control rack (TXR-191). The RF connections to
the RF drawer assembly are accomplished through an inter-
face plate on the bottom of the TXR-191 rack assembly.
The C-band converter assembly (RCV-129) consists of a
single wall-mounted Hoffman enclosure that measures approxi-
mately 16 in. by 15 in. by 6 in. The enclosure contains the RF
downconverter module and power supply. The RF ports and
monitor connections are provided through an interface plate
on the side of the assembly.
The C-band portable zero delay device is housed in a
weather-tight portable box that contains the RF hardware
and a set of three cables for use during the calibration tests.
During the use of the device, the assembly is placed in the
proximity of the C-band exciter so that connections between
the exciter, microwave couplers, and the C-PZDD can be made
using the provided cables.
IX. Conclusions
The C-band exciter assemblies were installed at DSS-14
during late December 1988 and are presently undergoing
engineering tests. Due to the shared configuration of the
C-band uplink controller, the overall C-band uplink assemblies
will be tested together when the final acceptance tests are
performed. Several tracks of the Phobos spacecraft have
been accomplished and the system has met its functional
requirements.
295
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RANGE
MODULATION
RCV-421
EXCITER
RACK
I&5MHz
DOPPLER
EXTRACTION
RCV 411
RECEIVER
RACK
CONTROL ROOM ] ANTENNA
Fc
116
43,2 MHz REFERENCE
C-BAND
UPLINK
CONTROL
RACK
TXR-191 •
I ] S BANDI -" EXCITERRCV 441
43.2 MHz REFERENCE
43.2 MHz REFERENCE
DOPPLER 55MHz IF
LOCAL OSCILLATOR
48 Fc
116ANTENAijEXCTEEXCITER IN OUT (Fc)C--BANDEXCITERRCV-130
t ICBAND
DOPPLER / I DOPPLER
REFERENCE1 I REFERENCE
,N I I OUT
/ /228 F¢ +620 MHz
/ _ 6B,
-I DOPPLERITRANSLATOR I
RCV-431 J
.._ C-BAND
TRANSMITTE _ - _
L-BAND OUT
228 Fc/681
-BANDIATTENUATOR I
RCV-481 J
L BAND TEST
SIGNAL
(COHERENT)
228 Fc/681
55 MHz IF
LOCAL OSCILLATOR
I S BAND I
RECEIVER I-
RCV 461 I-
RCV 462 •
S-BAND
J BLOCK IV ASSEMBLIES
I_C BAND ASSEMBLIES
L,S-BANOI____liiilM:;iC:: iO:W i ::ili2PUPCONVE RTE _i::CO UP LE RS ;i_
(L-BAND + 620 MHz) L-BAND L-BAND SIGNAL tN
FET
Fig. 3. C-band upUnkand L-band downUnksignal path.
BLOCK IV
S-BAND
EXCITER
RANGING
CODE MODULATION
C-BAND
RANGING
ASSEMBLY
EXCITER OUT (Fc)
C-BAND
EXCITER
RCV 130
DEMODULATEO
RANGING CODE
BLOCKIV_ 11
S-BAND L/S-BAND
RECEIVER UPCONVERTER
(L-BAND + 620 MHz)
C-BAND
TRANSMITTER
C BAND SIGNAL OUT
C-BAND UPLINK
Fc
C BAND
-_ _ PORTABLE
ZERO DELAY
L-BAND OUTPUT
228_
681
L-BAND L-BAND SIGNAL IN
FET
Fig. 4. C-band portable zero delay ranging.
298
BUS EXTENDER I
C-BAN--;---- I
CONTROLLER
HP VECTRA I - 1
[ COMPUTER ] I
DATA ] I
ACQUISITION L,_
RF DRAWER
ASSEMBLY
RCV -492
POWER SUPPLY
ASSEMBLY
RCV-493
C-BAND
UPLINK CONTROL
RACK (TXR-191)
CONTROL ROOM I ANTENNA
BUS EXTENDER
DATA
ACQUISITION
UNIT
(DAU)
C-BAND
TRANSMITTER
RACK
TXR--190
Fig. 5. C-band controller block diagram.
C-BAND
EXCITER
RCV-130
C BAND
TRANSMITTER
ASSEMBLIES
C-BAND
CONVERTER
RCV-129
C-BAND
MICROWAVE
ASSEMBLIES
299


The DSS-14 C-band exciter

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