A Study And Design Of Low Noise Amplifier And Bidirectional Mixer MMIC In K-band

As two key modules of receiver RF front-end, LNA and mixer affect the receiver system profoundly. Along with development of the monolithic microwave integrated circuit(MMIC) technology, the need of RF front-end of high performance expands increasingly. In this paper, based on MMIC technology, a K-band low noise amplifier is designed in 0.15 mm Ga As process with minimum noise and maximum power transmission achieved simultaneously. Also a bidirectional mixer MMIC is designed in 0.15 mm Ga As process. The main achievements of this work consist of following aspects.The basic theory of low noise amplifier is analyzed and discussed in this paper. For each specification, a LNA circuit is proposed based on source inductance feedback structure with improved biasing network and matching network which reduces noise figure and improves power transmission gain effectively. The layout of LNA is designed and simulated by EM simulator in ADS. At its working band of 21~24GHz, the NF of LNA is varying from 1.7d B to 1.97 d B, and power transmission gain is up to 23.5d B. The biasing network is designed with dual power supply. A shunt capacitance-microstrip structure is used for the drain of transistor to provide good isolation for DC supply and amplifier, while the gate is powered by a large resistor for area economization. In the design of matching network, minimum noise mathing is applied to input matching while conjugate matching is used in inter-stage mathing which provides not only minimum noise but also maximum power transmission. Meanwhile gain flatness of 0.7d B is achieved by adjusting the cut-off frequency of matching network of the third stage. In addition, stability in low frequency is achieved by using small resistance at the drain of transistors which is verified by simulation result of absolute stability in 0~30GHz.In this paper, a double-balanced mixer is designed with Ga As Schottky diodes which is bidirectional and realizes time-shared use for both receiving and transmitting. Diode-ring and Marchand baluns are employed for improving the conversion loss, port to port isolations and area saving. The results of EM simulation show that designed goals is meet. With LO power of 15 d Bm and IF frequency of 1.5GHz, for up-conversion and down-conversion the conversion loss is-8.5d B and-9d B, the linearity of P1 d B is 10 d Bm and 12.5d Bm, and isolations among three ports are below-24 d B.