A fully integrated frequency synthesizer for a dual-mode GPS and Compass receiver

This paper presents a fully integrated frequency synthesizer for a dual-mode GPS and Compass receiver fabricated in a 0.13 m CMOS technology. The frequency synthesizer is implemented with an on-chip symmetric inductor and an on-chip loop filter. A capacitance multiplying approach is proposed in the on-chip loop filter design for area-saving consideration. Pulse-swallow topology with a multistage noise shaping † modulator is adopted in the frequency divider design. The synthesizer generates local oscillating signals at 1571.328 MHz and 1568.259 MHz with a 16.368 MHz reference clock by working in integer and fractional modes. Measurement results show that the phase noise of the synthesizer achieves –91.3 dBc/Hz and –117 dBc/Hz out of band at 100 kHz and 1MHz frequency offset, separately. The proposed frequency synthesizer consumes 8.6 mA from a 1.2 V power supply and occupies an area of 0.92 mm.