A Dual-band Fractional-N Frequency Synthesizer for 2GHz and 5GHz

A new dual-band fractional-N frequency synthesizer is designed to support both 2GHz and 5GHz. The frequencies of two bands are synthesized by single PLL. It needs only a few additional circuits for dual band and has advantages in power and chip area. The synthesizer is composed of dual-band VCO, prescaler, 8/9 divider, PFD(phase-frequency detector), Charge Pump and LF(loop filter). 0.18um CMOS process with 1.8V supply voltage is used in design. SPICE and ADS simulation is performed using the layout extracted net-list. The proposed synthesizer is applicable to IEEE. std 802.11a/b.