Analysis of transients affecting the selection of hopping rate for FH/CPFSK systems

The authors consider certain aspects of the implementation of frequency-hopped continuous-phase frequency-shift-keying (FH/CPFSK) systems. The issues considered include the selection of a hopping rate, emissions control measures and hop transient effects, and synchronization requirements. The effect of synthesizer switching transients on the emitted signal spectrum and the receiver IF signal between hops is analyzed. It is shown that the intermediate frequency filter of the receiver will reject most of the transient harmonics due to synthesizer switching and mismatches between transmitter and receiver synthesizer switching times. Consequently, guard times at the beginning and end of a hop of approximately one data-symbol period each are required to avoid corruption of the data by the phase transient