MIL-STD-469B APPENDIX A
60.3.2 Requirements. The required spurious response characteristics of radar receivers should be as specified (see 5.5).
60.3.3 Application notes. The receiver input reference point should be selected at, or as close as possible to, the connection point of the transmission line to the system antenna (antenna terminals). Where it is not practical to establish the receiver input reference point at the system antenna, additional measurements should be obtained to describe the transmission line loss between the point which is used and the system antenna terminals.
60.3.3.1 The range of test signal frequencies are specified in 5.5. The test signal generator should be modulated with a pulse of the same width as the system pulse and triggered by the system trigger. For systems using waveguide transmission line, the signal generator output should be applied at the receiver input through appropriate waveguide transitions and adapters to ensure, as much as possible, dominant mode incidence to
the receiver. Adapters and transitions should be changed as necessary to correspond with the test signal frequency. Filters should be used to prevent unwanted signal generator outputs from entering the receiver. Attenuators should be inserted at the receiver input to provide a better match between the test signal source and the plane of reference.
60.3.4 Procedure. Typical block diagrams of the test setup for spurious response measurements should be as shown on figures 25 and 26.
60.3.4.1 The receiver should be tuned to F M and adjusted for normal operation in the selected mode. With the test signal generator set to the low end of the required frequency range, the test signal level should be adjusted at the receiver input such that the value exceeds the measured receiver sensitivity level by at least 10 dB plus the spurious response rejection value specified in table IX for the appropriate radar category. Starting at the low end of the required frequency range, the frequency of the test signal generator should be increased until a response is observed on the receiver output monitor. The receiver response and point for monitoring should be the same (see 60.2) as that used for measuring the overall selectivity. With the frequency of the test signal adjusted for a maximum response, the test signal level should be reduced to obtain the MPMVS response (see 60.2) (MDS for pulse radars). The test signal generator output level and frequency should be noted. After adjusting the test signal generator level to be value described for the start of the test, the test
signal frequency should be increased until another spurious response is located. The scan and measurement procedure should be repeated for all spurious responses up to the maximum test frequency as specified (see table VI) for the emission bandwidth test.
60.3.4.2 The spurious response test procedure should be repeated for each receiver tuned frequency specified and each mode and band of receiver operation.
60.3.5 Sample calculation. The results from the spurious response measurements typically consist of test signal generator level and frequency at each spurious frequency point plus associated information such as attenuation inserted and insertion losses of adapters transitions and cables. Sample data forms are shown (see figures 31 and 32).
60.3.5.1 A sample calculation to obtain the spurious response level follows: Measured data:
Receiver tuned frequency: 3650 MHz
Test pulse width: 5.0 microseconds
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