Research Of Wideband CMOS Low Noise Amplifier For Multi-band And Multi-standard Receivers

The continuous development of economy and technology leads to a variety of wireless devices for different applications. If integrating different wireless standards on a single chip in CMOS technology, the terminals can be portable, multi-functional, energy-efficient and cheap, and that is pursued by consumers. To realize a flexible, compact and low power multi-band multi-standard receiver, the wideband low-noise amplifier (LNA) is a key module. Due to the large parasitic and low supply voltage in CMOS technology, the design of high-performance wideband CMOS LNA is difficult. This dissertation focuses on the bandwidth expansion, low noise and linearization technique for wideband CMOS LNA.MOSFET’s characteristic and working condition will considerably influence LNA’s performance. This dissertation thus illustrates the important physical effects of short-channel MOSFET, and then presents a simplified DC model for strong inversion region, which is suitable for the qualitative manual design of circuit. In addition, in order to afford guide for LNA design and optimization, MOSFET’s small signal model, noise model and weak-nonlinearity are also illustrated, together with the discussion of optimization method for some parasitic elements.Sufficient bandwidth is premise for LNA to cover most of the band and wireless standards, meanwhile well flatness of output can reduce signal distortion and relax the requirement for ADC’s dynamic range. An active feedback LNA which uses a relative small inductor effectively broaden the bandwidth is presented in this dissertation, and also the related analysis. That inductor can increase transistor’s effective trans-conductance and thus compensate the gain loss caused by load capacitance. Therefore a wider bandwidth can be obtained together with a flat gain. Finally, the LNA is verified through tape-out in65nm CMOS process. It achieves a relatively flat voltage gain of15.5±0.9dB across0.4-10.6GHz, and a bandwidth expansion ratio of1.43.The multi-path signals received simultaneously by wideband LNA will mutually become the in-band interference, so better linearity is required for wideband LNA to reduce signal distortion. This dissertation analyzes active feedback LNA’s nonlinearity, and presents a source follower composed of composite transistors pair, which can effectively improve the linearity of active feedback LNA. The simulation in0.18μm technology verifies this technique. Compared to traditional source follower, this technique can improve LNA’s IIP2and IIP310.7dBm and3.1dBm respectively.High-performance receiver prefers differential structure, which requires a single-to-differential balun. This dissertation compares common balun LNAs, and finally selects the common-gate common-source (CG-CS) structure for improving. In the common-source stage, a pMOSFET is adopted as post-distortion auxiliary transistor, which can neutralize the second and third nonlinear terms of primary NMOS transistor effectively, and then significantly improves CG-CS balun LNA’s IIP2and IIP3. In addition, a large resistor is connected between the source and bulk terminals of common-source transistor, which effectively inhibits the substrate noise of that transistor. The simulation in0.18μm process indicates with that resistor, the CG-CS balun LNA’s noise figure at1GHz will drop down to2.5dB from2.88dB.