A microwave mixer with an adaptive bias network

Abstract

The goal of this dissertation is the exploration of novel circuit designs for microwave mixers appropriate for the “next-generation” wireless systems that require extremely high linearity and efficiency operations. This particular research mission is critical to the next generation of wireless communication devices – both for mobile voice-oriented communications links as well as higher bandwidth fixed point-to-point links. The critical nature of this effort is due to the increasing simultaneous need for bandwidth-efficiency and low DC power consumptions, which are at almost complete odds with each other, and require some significant and creative approaches to realize improved performance. I extend the aforementioned linearization technique back to mixer design. As anticipated, the devised single ended active mixer features simple. Technique aims at reducing the third-order inter-modulation distortions (IMD3) in mixers with an adaptive bias network and provides merits of miniature, good power handling and spurious-free. A highly linear single ended active microwave mixer is proposed that adopts a new adaptive bias network. A down conversion mixer with 1.9GHz RF frequency and 0.1GHz IF frequency is realized and measured. The proposed design provides high conversion gain of 11-dB and improves linearity at the high output power level simultaneously. Two-tone tests reveal a maximum 31-dB reduction for IMD3 while a typical pre-distortion technique suppresses IMD3 by 17-dB. The mixer using a NPN silicon germanium RF transistor achieving -4 dBm output power at output 1 dB gain compression point (P-1dB). Moreover, +17 dBm third-order product input intercept power (IIP3) and +23 dBm third-order product output power (OIP3) under a 2-V bias voltage are achieved. Graceful degradations on modulation bandwidths and gain variations are also presented.