[] . Isolation in the transmission line is assured by the fact that the output IF frequency is different from either of the two input IF’s, and microwave isolation at the antenna element is assured by choosing N so that [] or [] Finally, note that the entire PCC + PRR consists of just five mixers and their associated filters and IF limiter amplifiers (not shown), plus one flip-flop (x 1/2). The phase-locked PCC and PRR circuits in Figures 6 and 7 use at least as many mixers and filters as Figure 9, but the latter does not need the phase-locked loop components (phase detector, VCO and loop filter). C. Pointing Errors in ARA’s a) Doppler Errors The principle of retrodirectivity requires that the phase delay between two points, A and B, be the same for a signal traveling from A to B as it is from B to A. But this symmetry fails when B moves relatively to [] is the phase delay observed at B at time, t, of a signal sent from A, and [](t) is the phase delay observed at A at the same time, t, of a signal sent from B, then because whereas If the radial component of the velocity of B relative to A is v, then
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