Analysis and SAW realization of a matched filter for contiguous step FM signal with BPC

Abstract

In the work reported here, we investigated the properties of a class of matched-filter signals, that is, contiguous step FM signals with the binary phase coding. These signals were analyzed and compared theoretically by the ambiguity functions for 3-bit, 5-bit, 70bit, and 10-bit, respectively. From the results, it can be seen that the ambiguity functions of the contiguous step FM signals with the alternate binary phase coding have the narrowest widths of the central peak at zero-doppler and also provide the greatest potential for resolving in time. And a matched-filter was constructed using surface-acousticwave device technique that resulted in the highly compact device. The 3-bit contiguous step FM signal with the alternate phase coding has been fabricated on HC-cut quartz for propagation in the X direction. 73.6MHz center frequency was used with subpulse time duration $\delta=0.272\mu{us}$, that is, frequency separation between the two adjacent bits $f_n - f_{n-1} =1/\delta$ =3.68 MHz. Measurement of the impulse response has been made. The results obtained closely follow theoretically predictions. Although some problems exist in the direct electrical coupling from input to output and partial non-reversal of phase, the feasibility of practical surface-acoustic-wave matched-filter for the contiguous step FM signal with the binary phase coding has been demonstrated.