TABLE OF CONTENTS The frequency-hopped differential phase-shift keying (FH-DPSK) system is a spread-spectrum method of communication that can provide mobile-radiotelephone services to a large number of urban customers. Each FH-DPSK signal is a sinusoidal, constant-envelope, continuous-phase signal divided into discrete time intervals-each of duration t 1-called "chips." Over a waveform interval of duration T = Lt 1, a specific sequence of L different tones or chips is assigned and no frequency assignment is repeated ( L is the number of different frequencies). The signal is periodic with period T. The frequency assignment takes the following form:
where 
is the frequency shift from the carrier f c assigned to the ith time chip of the kth waveform of the set, a k is the integer from the kth code of a code set, i = 1, ..., L, and f 1 is the fundamental frequency channel before hopping. Hence, there are L distinct signal waveforms, each with L time chips and each with a bandwidth of approximately L/ t 1.
A representative signal in the time-frequency plane is shown in Fig. 8.26. The "continuous-phase" property ensures that the waveform chip will form a continuous joint at the edges with other chips and therefore will contain an integer of cycles.
The figure of merit representing system and/or spectral efficiency can...
