High performance frequency hopping transmitters using two-point delta-sigma modulation

This paper describes a 2.4 GHz high performance frequency hopping (HP) transmitter using two-point delta-sigma modulation (TPDSM). Two bottleneck problems in the implementation have been studied. One is the inherent gain and delay mismatches between two modulation points. The other is the nonlinear performance of phase-locked loop (PLL). Both mismatch and nonlinear factors dominate the closed-loop modulation accuracy. Our simulation can predict the dependencies of modulation accuracy on both factors quite well. Comparison between simulation and measurement also shows good agreement. The implemented TPDSM-based FH GFSK transmitter can achieve 2.5 Mbps data rate and meanwhile 15 μs PLL stable time with only 2.2% rms FSK error under good design and operating conditions.