A novel wide-range continuously-tuneable varactor-based matching network for low-noise amplifiers

Abstract

With the increasing demand of wideband or multi-standard wireless communications, low-noise amplifiers (LNAs) with wideband characteristics have become a crucial building block of typical receivers. In the design of LNAs, the major parameters such as gain, return loss and noise figure (NF) heavily rely on the input and output matching. In this paper, a novel tuneable matching network is proposed and a wide-range tuneable LNA operating within the range from 1.5 GHz to 2.3 GHz is constructed with this novel matching network. The capacity of this proposed matching structure to be continuously-tuneable is accomplished by utilising varactors of which the capacitance can be optionally controlled. Furthermore, the design theory of the proposed tuneable matching network is derived. A microstrip prototype of the LNA is simulated, fabricated and measured for verification. The LNA prototype maintains gain and return loss over 10 dB in the frequency range from 1.5 GHz to 2.3 GHz. Additionally, all operating-frequency NFs of the prototype are below 3 dB. The measured results show that the performance of the fabricated prototype is consistent with the simulation, which demonstrates the effectiveness of this proposed new design. IntroductionThe demand for multi-access, diverse applications for wireless communication has derived multiple wireless communication standards. Owing to the multiple wireless communication standards, the design of special transceivers ought to operate over wideband without other performance degradation. It is hard to detect the input signal due to the noisy and complex environment at the front end of a transceiver, where high sensitivity is essential. Moreover, the mode of wideband is susceptible to out-of-band interference. Therefore, tuneable performance covering a wide tuneable range is proposed to transform wideband into multiple narrow-frequency bands.The low-noise amplifier (LNA), a front-end building block, undertakes the task of amplifying the incoming weak wireless signal almost without introducing noise and distortion while determining the sensitivity of the receiver and dramatically influencing the noise performance of the whole system. A multi-standard LNA is required in order to provide a low noise figure (NF), high gain, unconditional stability and low power consumption. Generally, the design of LNAs requires compromise in order to balance these performance criteria. For instance,