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A 0.18-μm CMOS wideband passive mixer fully integrated with baluns in IBM7HP process is reported. The mixer exhibits wideband operation, despite the intrinsic narrow-band magnitude balance of passive baluns. Very low DC offset, of less than 3 mV, is achieved without any DC cancellation circuits, due to high LO–RF isolation. At the RF frequency of 2.4 GHz, the combined IF differential outputs provide conversion loss (CL) of 7.5 dB, input 1 dB compression point (IP1dB) of 6.2 dBm, and input third-order intercept point (IIP3) of 15.5 dBm. This mixer exhibits broad-band RF impedance matching with reflection coefficient magnitude better than −9.6 dB through the RF frequency range from 1 to 12 GHz. The CL of 10.1–12.9 dB, IP1dB of 8.6–14.4 dBm, and IIP3 of 16–22.2 dBm are achieved at this frequency range for broad-band applications. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:23–27, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27226

One of the challenges in Doppler radar systems for physiological monitoring is a large DC offset in baseband outputs. Typically, AC coupling is used to eliminate this DC offset. Since the physiological signals of interest include frequency content near DC, it is not desirable to simply use AC coupling on the radar outputs. While AC coupling effectively removes DC offset, it also introduces a large time delay and distortion. This paper presents the first DC coupled IQ demodulator printed circuit board (PCB) design and measurements. The DC coupling is achieved by using a mixer with high LO to RF port isolation, resulting in a very low radar DC offset on the order of mV. The DC coupled signals from the PCB radar system were successfully detected with significant LNA gain without saturation. Compared to the AC coupled results, the DC coupled results show great advantages of less signal distortion and more accurate rate estimation.

A 2.4 GHz resistive ring mixer with on-chip baluns is fully integrated in 0.18µm IBM7HP process. This mixer exhibits broadband RF impedance matching with return loss better than −10 dB through the RF frequency range from 2 to 6 GHz. The conversion loss of 7.8 dB is achieved at the RF frequency 2.4 GHz. This mixer provides 6 dBm of the input P1dB, and 13.4 dBm of the input IP3 at the operating RF frequency. This mixer is the first reported double-balanced resistive mixer with integrated RF and LO baluns. This mixer has a very compact layout due to the absence of the matching circuits, and is suitable for homodyne and heterodyne transceiver architectures for wireless applications.

This paper describes a wide-band resistive ring mixer fully integrated in 0.25μm CMOS process. This mixer exhibits broadband RF impedance matching with return loss better than −10 dB from 2.2 to 8.3 GHz, and better than −15 dB from 3 to 6.2 GHz. The best conversion loss (CL) of 6.4 dB is achieved at 3.2 GHz. The input P1dB is better than 4 dBm, and the IIP3 is better than 11.4 dBm over the entire RF bandwidth of 2 – 9 GHz. Compared to other published CMOS wide-band resistive mixers, this mixer achieves the best linearity between 2 and 9 GHz. In addition, with a small gate bias a moderate CL is achieved at very low LO power levels.

A retrodirective array using self-oscillating mixers (SOMs) is presented. SOMs allow for easier implementation of larger two-dimensional arrays by eliminating the complex local-oscillator (LO) feed structure. A four-element linear retrodirective array using SOMs is demonstrated at a LO frequency of 8.87 GHz. Each element is successfully phased locked at the LO frequency while 33 dB of isolation between adjacent elements is measured at the RF frequency. The LO power generated by a single SOM element at the fundamental frequency is +3 dBm. Retrodirectivity is successfully observed for scattering angles of -30/spl deg/, 0/spl deg/, and +15/spl deg/.