MIL-DTL-28837C
4.7.4.4 Conversion compression. The conversion compression shall be determined by measuring the RF power
required to increase the conversion loss by 1 dB.
Procedure. Using the test setup of figure 1 and the procedures of 4.7.4.1, determine a conversion loss at some
convenient LO and RF frequencies within the specified range, adjusting the available RF power to the level
specified for 1 dB compression maximum. Increase attenuation in ATTN R by nominally 10 dB and decrease
ATTN I by the same actual value. Re-measure conversion loss. Change of 1 dB or less shall be acceptable.
NOTE: Minimum value of ATTN R and ATTN I shall neither be less than 10 dB.
4.7.4.5 Conversion desensitization. The conversion desensitization shall be determined by measuring the RF
power required to increase the conversion loss by 1 dB.
Procedure. Using the test setup in figure 1 and the procedures in 4.7.4.1, determine a conversion loss at some
convenient LO and RF frequencies within the specified frequency range (see 3.1). Introduce a second RF
frequency and increase its power until the conversion loss increases by 1 dB. This second RF signal power
shall be as specified (see 3.1).
4.7.4.6 Intermodulation. The intermodulation products of the mixer shall be tested as specified in 4.7.4.6.1 or
4.7.4.6.1 Two-tone third-order intermodulation. The two-tone third-order intermodulation (LO-(2RF1-RF2)) and
(LO-(2RF2-RF1)) shall be measured using the test setup of figure 6. The following details shall apply:
a.
Measuring system.
(1)
The measuring system dynamic range shall exceed the allowable intermodulation by at least 10 dB.
(2)
The measuring system shall have flat amplitude response across the frequency range of the third-
order intermodulation frequencies.
(3)
Sufficient attenuation shall be provided to prevent overload of the spectrum analyzer.
(4)
The power combiner hybrid network shall provide isolation of 20 dB minimum.
b.
Procedures.
(1) Adjust ATTN RF1, ATTN RF2, and ATTN R to provide available power of RF1 and RF2 each equal to
(LO available power - 20 dB) at the R port.
(2) Adjust spectrum analyzer sensitivity and ATTN I for LO-RF1 and LO-RF2 to indicate 0 dB relative.
Measure relative level of third-order intermodulation.
(3) Increase ATTN I by 10 dB. If the levels of the four frequencies of step (2) each decrease 10 dB, the
determination of step 2 is valid.
4.7.4.6.2 Harmonic intermodulation. The harmonic intermodulation product shall be measured using the test setup
in figure 7. With the specified LO and RF powers (see 3.1) applied at some convenient LO and RF frequencies within
the specified range, the harmonics power level in reference to the IF output shall be measured.
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