In this thesis we present an image rejection and gain control enhancement technique for receiver system of mobile communication in CMOS technology. In order to improve image rejection characteristic of an amplifier, the proposed technique uses notch filter composed of spiral inductor and capacitor. The elements of filter should have high quality factor in order to make sharp bandwidth. So, using the spiral inductor with higher quality factor than another inductor and MIM (metal-insulator-metal) capacitor that are serviced at Fabrication Company, the notch filter with narrow bandwidth is achieved. Furthermore, since attaching the filter at cascode topology reduces leakage due to parasitic capacitance, the noise figure at interest frequency can be enhanced. In addition to gain control function, the input linearity of system is enhanced. Since the low noise amplifier (LNA) with only amplification function locate at stage going before mixer in conventional system, large signal to input of receiver can be saturated at following stage.
Finally, the proposed image rejection and gain control is successfully applied to the 5.8GHz frequency LNA implemented in $0.18mum$ CMOS technology. However, since the quality factor of spiral inductor fabricated is lower than expected value, image rejection reduces as compared with simulation. And noise performance became higher 0.2dB than expected result. The presented LNA has the 16dB power gain, 11.5dB image rejection, 1.6dB noise figure and 7.2mW power consumption at 1.8V supply voltage.