A Dual Band Fractional-N Frequency Synthesizer with a Self-Calibrated Charge Pump for WLAN Standards

摘要

This work presents a fully integrated fractional-N frequency synthesizer that covers the entire frequency bands specified in the IEEE 802.11 a/b/g. In this paper, the effects of charge pump (CP) gain mismatch on spectral purity of local oscillator signal is studied theoretically and a new high precision self-calibrated CP is presented for alleviating the nonidealities. The idea is implemented in a 0.18-mu m standard CMOS technology. According to post layout simulation, the proposed calibration circuit demonstrates an excellent matching in the CP currents in a wide voltage range. By using this technique, the average of close-in phase noise of the designed frequency synthesizer is suppressed by more than 12 dBc. The active whole chip die area is 0.475 mm(2) and the power dissipation from a 1.8-V DC supply is 17.3-20.6 mW.