Measurement of diversity-combining performance enhancement for fast FH

Repetition of a symbol of L different hops can be used to decrease the error rate of fast frequency hopped (FH) signals. An experimental measurement system that uses a SAW (surface acoustic wave) demodulator and a signal processing microchip is described. The performance of hard-decision majority-vote combining (HDMV) and normalized envelope detection (NED) combining was measured in the presence of severe (down to 0-dB effective signal-to-jamming ratio) noise and multitone jamming plus system noise. HDMV combining reduced the bit-error rate (BER) reasonably well for noise jamming but gave little reduction for large multitone jamming. NED combining produced substantial reduction in BER for both forms of jamming. Neither method exhibits the failure mechanism of error-correction coding at high input BERs. The measurement system demonstrates the ease of implementation of the two combining techniques in real time. It also demonstrates that changes in L over a wide range are easily implemented