TEMPERATURE COEFFICIENTS OF GAIN AND PHASE FOR … · 2010. 9. 17. · TEMPERATURE COEFFICIENTS OF...
Transcript of TEMPERATURE COEFFICIENTS OF GAIN AND PHASE FOR … · 2010. 9. 17. · TEMPERATURE COEFFICIENTS OF...
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NATIONAL RADIO ASTRONOMY OBSERVATORY
CHARLOTTESVILLE, VIRGINIA
ELECTRONICS DIVISION INTERNAL REPORT No. 261
TEMPERATURE COEFFICIENTS OF GAIN AND PHASE
FOR VARIOUS MICROWAVE COMPONENTS
S. WEINREB AND R. HARRIS
JUNE 1986
NUMBER OF COPIES: 150
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TEMPERATURE COEFFICIENTS OF GAIN AND PHASEFOR VARIOUS MICROWAVE COMPONENTS
S. Weinreb and R. Harris
The gain and phase vs. frequency curves at temperatures of approximately 25C
and 55C were measured for two filters, four isolators, and five amplifiers at
center frequencies of 1.5 to 23.5 GHz. A Hewlett-Packard 8510 network analyzer
was used for the measurements. The devices were heated using a small temperature-
controlled hot plate clamped to an aluminum plate and the device under test. A
linear variation of gain and phase is assumed for the measurement temperature
range. The resulting temperature coefficients are summarized in Table I and full
results are presented in Figures 1-5.
It is informative to compare the phase coefficients expressed in ps
(10-12
seconds) per °C in the last column of Table I with other coefficients and
specifications. The magnitudes of the measured coefficients are of the order of
.05 ps/°C and four such components in a typical front-end would give a coefficient
of 0.2 ps/oC. A five-meter length of transmission line having effective length
change of 20 x 10-6 / 0 C (i.e., a "phase stable" cable) would give 0.5 ps/°C.
Thus, cables rather than RF components are critical to the phase-stability
specification.
The Very Large Array phase stability goal was 1°/GHz over a 1,000 second
period (i.e., between calibrator observations); this is 2.8 ps change in 1,000
seconds. RF component temperature control of + 2C over 1,000 seconds (very easy)
would give only ± 0.4 ps change.
The frequency standard for the Very Long Baseline array has a time stability
specification of 2 ps in 1,000 seconds and 20 ps in 10,000 seconds. Thus, RF
component temperature variations of + 2C in 1,000 seconds or + 20C in 10,000
seconds give peak phase variations only 20% of the rms phase fluctuation due to
the frequency standard.
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TABLE I. Summary of Results
FREQ. AG/AT Acp/AT AT/ATCOMPONENT GHZ dB/0C 0/0c ps/0C
Filter, six-pole, 570 MHz BW 1.5 < .003 + .06 + .11
Amplifier, 18 dB gain, Miteq 1.5 - .020 + .03 + .05
Filter, six-pole, 700 MHz BW 4.7 - .003 - .20 - .12
Isolator, C-band 4.7 - .001 _ .06 - .04
Amplifier, 20 dB gain 4.7 - .020 - . 13 - .07
Isolator, X-band 8.4 - .001 - .08 - .03
Amplifier, 17 dB, Miteq 8.4 - .016 - .16 - .05
Isolator, KU-band 14.9 < .001 - .30 - .06
Amplifier, 16 dB, Miteq 14.9 - .016 - .25 - .04
Isolator, K-band 23.5 - .003 - .15 - .02
Amplifier, 19 dB, NRAO 23.5 - .014 - .43 - .05
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Fig. 4. Test results for KU-band isolator and amplifier.
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