A max 349 GHz 18.2mW/pixel CMOS inter-modulated regenerative receiver for tri-color mm-wave imaging

Abstract

This paper presents a mm-wave imaging CMOS regenerative receiver which is intermodulated by a second oscillator to provide multiple receive bands at 349, 201 and 53 GHz for false color imaging. The proposed receiver consumes 18.2mW per pixel and occupies 0.021mm 2 of silicon area. I. INTRODUTIONSub-mm-wave and mm-wave based imaging has recently gained interest for security screening and bio-imaging applications. As a response to this interest, the circuit community has proposed several approaches to implement mm-wave imaging systems in CMOS technology [1,2,3]. While these approaches meet the major challenges of noise, sensitivity and dynamic range, they are all narrowband approaches (single frequency) and suffer from narrowband imaging effects including edge ghosting, speckle, and a limited ability to discriminate between different materials in the scene [4]. For mm-wave imaging to become practical, high operating frequencies are also necessary as the operating frequency limits the attainable spatial or "cross" resolution (wavelength dependent).The major advantage offered by CMOS imaging over III-V approaches is the possibility of constructing full 2D imaging arrays. Currently, III-V's pixel performance remains dominant over reported CMOS imaging pixels at the cost of higher power and more area. To take full advantage of the opportunities CMOS technology presents, the pixel circuits employed must offer low pixel area and low power in order to make array integration possible. CMOS imaging receivers based on the principle of super-regeneration have appeared in which an oscillator's start up time is perturbed by an active imaging signal, and a resulting time difference is detected [5]. While this technique provides low area overhead and power performance compared with other techniques, it is still narrowband with an upper frequency limited by Fmax, (highest frequency with device gain available). II. INTERMOD. REGENERATIVE RECEIVERIn order to directly address these two limitations, we propose the inter-modulated regenerative receiver (IRR) architecture, with block diagram shown in Fig. 1. The proposed IRR can concurrently receive in multiple-bands to approximate a broadband image. In this architecture a regenerative receiver at 201 GHz is first constructed with a conventional quench signal. A lower frequency tone is then directly injected from an auxiliary oscillator (aux-osc) at 148 GHz. Unlike the regenerative oscillator (reg-osc), which is periodically quenched at 1 GHz, the aux-osc runs continuously. As the reg-osc is highly non-linear, the injection of the aux-tone creates inter-modulation between both frequencies within the regenerator and gives rise to additional receive bands. Fig. 1. Inter-modulated regenerative receiver (IRR) architecture showing aux-osc, reg-osc, envelope detector, and key frequencies.The first order inter-modulation components (53 and 349 GHz) are particularly interesting for imaging as they offer responsivities and noise equivalent powers (NEP) within an order of the fundamental. Also of...

Power detectors for integrated microwave/mm-wave imaging systems in mainstream silicon technologies

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“…To dramatically reduce the power consumption while still maintaining high responsivity, the authors have proposed a super-regenerative structure based detector [15,16,17], which leverages ultra-high quality factor of super-regenerative amplifiers for high responsivity. In essence, the super-regenerative detector merges a super-regenerative amplifier with an envelope detector, as shown in Fig.…”

“…So far, many different devices and circuit architectures have been disclosed to conduct power detection in the literature. To facilitate wide deployment, detectors compatible with mainstream processes are preferred to be naturally integrated into imaging systems with small form factors [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], which will be the focus of this paper. Among them, there are three major types of detectors.…”

“…Super-regenerative receivers demonstrate low power consumption and high frequency operations. Most recently, it has been found that the super-regenerative circuit architecture can offer extremely high gain for power detection and has been demonstrated successfully in ultra-low power applications [15][16][17][18][19][20][21].…”

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