CMOS RF Mixer Research Articles

Ultra-Low Power CMOS RF Mixer for Wireless Sensor Networks Application: A Review

This paper reviews ultra-low power CMOS RF mixer for wireless sensor networks (WSN) application. The study elaborates several types of mixer, mixer’s performance parameters, the mixer’s topologies and also the design technique to improve the mixer performance. The previously published works are compared and the best topology for low power mixer is discussed.

Analysis and Design of Feedforward Linearity-Improved Mixer Using Inductive Source Degeneration

This paper presents a new linearity-improvement feedforward transconductance stage using inductive source-degeneration amplifiers. The proposed technique is applied to a CMOS RF mixer based on a folded-type topology. Feedforward compensation is achieved by cancelling the third-order transconductance terms between the inverter and auxiliary amplifiers. From a new theoretical analysis of the nonlinearities of the proposed circuit, the third-order intermodulation distortion is eliminated by controlling the values of the source-degeneration inductances. The proposed mixer achieves a third-order input intercept point of -5.24 dBm, which is an improvement of 6.3 dB compared with that of the conventional structure, and has the highest figure-of-merit among other linearity improved mixers that have been previously reported.

A New RF CMOS Gilbert Mixer With Improved Noise Figure and Linearity

The noise figure of an RF CMOS mixer is strongly affected by flicker noise. The noise figure can be improved using pMOS switch circuits, which insert current at the on/off crossing instants of the local oscillator switch stage because the circuits reduce the flicker noise injection. When it is applied to a conventional Gilbert mixer, the injection efficiency and linearity are degraded by the nonlinear parasitic capacitances of the pMOS switch circuits and the leakage through the parasitic path. We propose the pMOS switch circuits with an inductor, which tunes out the parasitic components at 2fo and closes out the leakage path. The mixer fabricated in 0.13-mum CMOS at 2.4-GHz center frequency has provided improved characteristics for linearity and noise figure.

CMOS RF mixer with digitally enhanced IIP2

A new method to enhance the IIP2 of a double-balanced Gilbert cell mixer through digital calibration is presented. The IIP2 calibration method consists of offset voltage cancellation in the switching pairs. The effectiveness of the method has been proven by calibrating a 0.18 mu m CMOS mixer at several combinations of worst-case mismatch conditions and corners. It has been found that the calibrated mixer can achieve its targeted IIP2 specification even at large process, temperature, and power supply variations.

Analysis and design of a low-voltage RF CMOS mixer

A CMOS low-voltage downconversion mixer is presented. With 1.69-GHz local oscillator signal input and 1.63-GHz RF signal input, measurement results show that the conversion gain is 6.631 dB, input-referred third-order intercept point is 1.51 dBm, single-sideband noise figure is 21.43 dB with a 1.8-V supply voltage. The mixer's noise and linearity analysis, layout technique to maximize RF performance and minimize noise performance are also presented in this paper.

A noise cancellation technique in active RF-CMOS mixers

Based on the physical understanding of noise mechanisms in active mixers, a noise cancellation technique to reduce the flicker noise contribution of the switches in a Gilbert-type mixer is presented. For the proof of concept, a prototype double-balanced mixer in 0.13 /spl mu/m CMOS is fabricated. The circuit achieves a flicker noise corner of almost an order of magnitude lower than that of a standard implementation, without any penalty in the linearity, gain, or power consumption.

CMOS RF amplifier and mixer circuits utilizing complementary Characteristics of parallel combined NMOS and PMOS devices

Design and chip fabrication results for complementary RF circuit topologies that utilize the complementary RF characteristics of both NMOS and PMOS field-effect-transistor devices combined in parallel way are reported, which can inherently provide single-ended differential signal-processing capability, requiring neither baluns, nor differential signal generating/combining circuits. The proposed complementary CMOS parallel push-pull (CCPP) amplifier gives an order of magnitude improvement in IP/sub 2/ than an NMOS common-source amplifier and single-balanced CCPP resistive mixer, which functions effectively as a double-balanced one, provides more than an order of magnitude better linearity in IP/sub 2/, and similar order of magnitude better local oscillator (LO)-IF and LO-RF isolations than NMOS counterparts.

A multitime circuit formulation for closely spaced frequencies

Verifying circuits with two or more closely-spaced driving frequencies is important in RF and wireless communications, for example, in the design of down-conversion mixers. Existing steady-state calculation methods, like harmonic balance, rely on Fourier series expansions to find the difference-frequency components typically of interest. Time-domain methods are, however, better suited for circuits with strong nonlinearities such as switching. Towards this end, we present a purely time-domain method for direct computation of difference tones in closely-spaced multitone problems. Our approach is based on multiple artificial time scales for decoupling the tones driving the circuit. Our method relies on a novel multitime reformulation that expresses circuit equations directly in terms of time-scales corresponding to difference tones. We apply the new technique to an RF-CMOS mixer to predict baseband bit-streams and down-conversion gain and distortion, in two orders of magnitude less CPU time than traditional time-stepping simulation. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.

Thermal noise in RF CMOS mixers

A noise model for CMOS single-balanced mixers is proposed by considering the noise currents in the MOSFETs, and it is shown that simple analytical equations can be derived for the spectral density of the output drain noise current in the case of thermal noise. The model agrees well with measurements made on the variation of the noise figure of the mixer with the bias current and local oscillator power. The theory is useful for simple and accurate modeling of the thermal noise in CMOS mixer design.