Detection Performance of Embedded QPSK onto LFM waveform Guard Bands for RF Convergence

In this work, we investigate the use of the guard bands of a linear frequency modulated (LFM) radar waveform for communications. For illustration, quaternary phase-shift keying (QPSK) is used. The effect of the LFM waveform on the symbol error rate (SER) is investigated. Conversely, the effect of injecting the QPSK RF carriers on the radar’s probability of detection (P
D
) is also investigated. To reduce the interference on each other, a spectral distance metric is introduced and its effect on SER and P
D
is evaluated. To mitigate the obvious effect or large radar power compared to communications, radar mainlobe notch filtering, parameter estimation and subtraction are used in the communications receiver. In terms of the radar’s P
D
, the effect of low-power communications due to the use of the guard bands turns out to be minimal.