this paper describes 3.3V silicon down conversion mixer with a current bleeding Gilbert multiplier and also compares the conventional current bleeding Gilbert mixer with an improved current bleeding circuit ,detail analysis are given about the two circuits using 0.35 um process. With a 1.675 GHz local oscillator (LO) and a 1.575 GHz RF input. The results show that the gain and IIP2of the improved mixer is higher than conventional Gilbert-type mixer, while the noise figure is better. Keywords-CMOS mixers second-order input intercept point (IIP2); current bleeding Gilbert cell third-order input intercept point(IIP3)

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In this paper, a wideband LC VCO with small Kvco fluctuation for RFID synthesizer application is designed using SMIC 0.18um standard CMOS process. The switched capacitor array and switched varactor array are used for wideband design. The VCO exhibited Kvco fluctuation of only 29%, which is about one third that of a conventional VCO. The simulation results show that the tuning frequency range is 64% from 0.76GHz to 1.48GHz ,VCO Gain is from 41MHz to 62MHz with power consumption of about 9 mW at 1.8 V supply. The measured phase noise is less than -90dBc/Hz at 100 kHz offset within the entire tuning range.