CONCEPTS FOR DESIGN OF CW RADARS FOR AIRBORNE APPLICATIONS

In this paper it is discussed some concepts in signal design and processing intended to increase the potential capabilities of CW radar system with double modulation to cover certain applications. The signal is phase modulated by pseudo random sequence and frequency modulated -b04, sinewave. The first system is based on parallel range gates and group-of doppler filter banks which is suitable for airborne surveillance. It enables automatic detection of several targets simultaneously and measur-ing range with high resolution, velocity unambigiously and bearing. It also suppresses the leakage and reflections from close-in clutter which are the main problems facing classical CW radars. The second system discussed used the idea of filtering several harmonics of the FM spectrum in the receiver instead of filtering only the third harmonic, then the detected outputs are further combined. This approach enables, beside suppressing leakage, to reduce the losses of power in the receiver. It offers opportunity to increase the maximum range substantialy, nearly double the value, as compared to system using the 3rd harmonic only. This option can use smaller value of the FM frequency. The presented version is suitable for airborne fire control application. The system is evaluated showing advantagesin addition to the properties attained by the system using double modulation.