Near-Clutter-Suppression in CW-Radar-Systems by Deterministic FSK-Modulation

PNPSK modulated CW-Radar-Systems may be affected by short range reflections. Due to the very high interference-power-level caused by unwanted reflections nonlinearities or other hazardous effects occur in the receiver front-end and the signal processing circuitry. Under such conditions even matched filter receivers may fail, or show at least degraded performance. Range resolution can be affected and ghost targets are possible. These near-clutter effects can be reduced by using a spatial filtering technique based on FSK-Modulation. A range window with triangular shape is produced. Its influence on the mean signal- and interference-power-level at the receiver input is calculated and discussed. An example for the realisation of a system is given. The presented principle is suitable for any kind of primary modulation.