MIL-STD-469 Radar Engineering Interface Requirements, Electromagnetic Compatibility See Notice 1 For Replacement InformationThis standard establishes the engineering interface requirements to control the electromagnetic emission and susceptibility characteristics of all new military radar equipment and systems operating between 100 megahertz MHz, and 100 gigahertz GHz, to ensure EMC in all intended operational environments, and to conserve the frequency spectrum available to military radar systems.

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MIL-STD-469B APPENDIX A

For non-pulse radars, the tracking preselector can be replaced with a passive rejection filter, tuned to the radar

Fo, when measuring emission levels in the rolloff region.

40.4.4.9  For phased array systems, procedures should be repeated (see 40.4.4 through 40.4.4.8) with the system operating in its normal search mode.

40.4.5  Sampling calculations.  The emission spectrum measurement results consist of the emission spectrum photographs and the associated frequency and amplitude calibration data together with insertion loss, coupling factor, and other calibrations as needed to obtain the power spectral level, in dBm/kHz, at the input to the radar antenna. Sample emission spectrum data forms are shown on figures 11 through 13.  Data reduction is required to yield a direct comparison of the radar performance to the specification limits.

40.4.5.1  Sample calculations which obtain the power spectral level in dBm/kHz from the measured data should follow. Calculations are based on pulse radar having the measured characteristics, listed below, and a nearly rectangular RF pulse envelope. Other conditions are that there are no sub-pulses within the pulse, and that the pulses are not FM or otherwise encoded.

Measured data at transmitter F o:

Transmitter tuned frequency (F  ): 5000 MHz

Frequency separation, first spectrum nulls (from photo): 1.54 MHz

Radar PRF: 650 pps

Spectrum analyzer alpha factor,    20.0 dB (2 x 10  6  second pulsewidth) Measured signal sampler coupling factor (A  ): 50.0 dB

Attenuation inserted at analyzer input (A  ): 30.0 dB

Signal generator CW calibration level (P    ) at emission spectrum peak:    24.7 dBm

(A1  removed)

Attenuation, signal sampler to radar antenna (A  ): 0 dB.

40.4.5.2  The first step in the data reduction calculates the spectrum analyzer IF bandwidth B from the measurement with the 2 microsecond test pulsewidth described (see 40.4.3.2). An alpha factor of minus 20 dB

provides Bxt = 0.067 (see figure 9). Therefore, (B)(2 x 10

6) = 0.067 which gives B = 33.5 kHz.

40.4.5.3  The effective radar pulsewidth (t eff) is determined from the equation t eff  = 2/fN, where fN  is the

frequency between the upper and lower first null points of the emission spectrum. Where f

teff  = 2/(1.54 x 106) = 1.3 x 10  6  seconds.

N  = 1.545 MHz,

40.4.5.4  With the spectrum analyzer bandwidth and the effective radar pulsewidth known, the product is: Bxteff  = (33.5 x 103) (1.3 x 10  6) = 0.044.

Applying Bxteff  (see figure 10), the pulse versus CW sensitivity for the radar signal (alpha R) is     23.6 dB.

40.4.5.5  The peak level Pp  of the radar emission at the radar antenna input is given by:

Pp  = PCW  + A1  + As

A2        alpha R.

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