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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)

A novel composite-channel AlxGa1-xN/AlyGa1-yN/GaN high electron mobility transistor has designed and optimized. The influence of the two-dimensional electron gas and electric field on device structure parameter is obtained from the self-consistent solution based on the theory of semiconductor energy band and quantum well. The influence of the layer structure of the device on its performance is obtained from simulation using TCAD software. Combining the results of theoretical analysis and simulation, the optimized structure Al0.31Ga0.69N/Al0.04Ga0.96N/GaN HEMT is proposed. The simulation results show that the device with gate length of 1 μm and gate width of 100 μm has the maximum transconductance of 300 mS/mm and small fluctuation in the gate voltage of from -2 V to 1 V, which shows the excellent linearity of the device. The maximum current density of 1300 mA/mm, the cut-off frequency of 11.5 GHz and a maximum oscillation frequency of 32.5 GHz are obtained.

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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.