Digital Frequency Synthesizer/Modulator for Continuous-Phase Modulations with Slow Frequency Hopping

This paper gives a description of a modulator for burst-by-burst carrier frequency hopping in time-division multiple-access (TDMA) systems. The architecture consists of a digital frequency synthesizer/modulator for continuousphase modulations (CPM’s) and a fast frequency settling RF synthesizer consisting of one phase-locked loop (PLL). The performance of the digital frequency synthesizer/CPM modulator has been analyzed theoretically and simulated by a computer program. The analyses show that the proposed digital frequency synthesizer/CPM modulator achieves 2.5-W lower power consumption and 18-dB lower spurious levels than the fast frequency hopping systems synthesizing digitally a full frequency band. In the computer simulations the effect of the digital frequency synthesizer/CPM modulator parameters on the power spectrum and the phase error is investigated.