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A wideband receiver employing single-stage harmonic-rejection mixers (HRM) is demonstrated. The HRM employs a 3-level PWM representation of a sinusoidal LO in combination with gain-ratios. The PWM LO signal is also used to perform gain control. The receiver gain with harmonic rejection is 26.4–30.1 dB using multi-phase PWM LO and 28–31.8 dB with single-phase PWM LO, for a gain range of 3.7 dB. The...
A full-duplex transceiver front-end architecture that employs inverse class-D switching power amplifiers is described. An LC phase-shift network is employed between the receiver port and the antenna port. By proper phasing of the switching devices, the transmitted signal can add constructively at the antenna port while canceling at the receiver port, thereby enabling full-duplex operation. The motivation...
A low-power Weaver image-reject receiver based on 3rd-order signal recursion is demonstrated. The design employs two downconverters and seeks to enhance the dynamic range and gain-bandwidth product per unit power dissipation metric by adopting recursive gain reuse at multiple frequencies. Utilizing an LO at frequency fLO, the downconverter recursively amplifies an RF signal at fRF at 3 distinct frequencies,...
A digital post-processing approach for reducing the anti-aliasing requirement in a frequency-folding channelizer architecture is described. The channelizer decomposes a broadband spectrum into multiple sub-bands. A signal of bandwidth N/2fLO is downconverted into N paths that are clocked using rectangular, non-overlapping pulse waveforms at a fundamental frequency of fLO with a duty-cycle of 1/N....
A bias-sharing two-stage harmonic rejection mixer that provides quadrature baseband outputs is demonstrated. The devices that bias the RF transconductors in a one-stage harmonic-rejection downconverter are configured to provide a second-stage of harmonic rejection for reducing the impact of gain coefficient errors, without requiring additional bias current. Clock retiming is used to desensitize the...
A feedback-based active interference cancellation technique for reducing interference in a broadband LNA is described. The interference is down-converted to baseband, low-pass filtered, then up-converted and subtracted from the input. Harmonic response in the active canceler is eliminated by using harmonic rejection mixers (HRMs). Furthermore, by configuring the HRMs to provide frequency translation...
Recent work in spectrum-channelizing receivers has demonstrated the ability to simultaneously detect and down-convert broadband inputs while using a single LO. This addresses a key design challenge in mixer-bank based spectrum channelizers, namely the requirement for multiple concurrently operating frequency-synthesizers. An approach that simultaneously addresses channelization and digitization is...
A direct downconversion receiver front-end that employs current-mode passive mixers is described. Bias-sharing is employed between the RF transconductor and a baseband tran-simpedance amplifier (TIA). Flicker noise of the RF transconductor is mitigated by chopping the RF signal, which is made possible by employing phase-domain orthogonality between RF and baseband signals. A noise shaping network...
A channelizing broadband receiver for a spectrum analysis application that employs a bank of two-stage harmonic rejection mixers (HRMs) is described. Each HRM internally synthesizes a distinct downconversion LO. In addition to minimizing LO harmonic response, the HRMs also include a quadrature phase matching technique for enhancing image rejection. The technique reduces the two-dimensional calibration...
Multi-frequency signal recursion allows for efficient reuse of transconductance in a radio receiver, which helps to reduce power dissipation. An I-Q receiver based on the recursive principle is demonstrated here. The design employs a self-biased load, with chopping at baseband in order to minimize low-frequency in-band flicker noise. The bias setting of the chopper devices is optimized to enhance...
A feedback-based active interference suppression technique employing harmonic rejection mixers (HRMs) for enhancing linearity in a broadband channelizer is proposed. In the approach, an interferer is down-converted to baseband, low-pass filtered and then up-converted, where it is subtracted from the input. Using previously reported HRMs capable of LO frequency synthesis in both the down-conversion...
An analog-to-digital converter (ADC) architecture is described which utilizes mixing instead of high frequency sampling, and folds the input in frequency around harmonics of the mixing local oscillator. The frequency-folded input is separated in the digital domain, which enables significant dynamic range benefits. The frequency of the mixing local oscillator can be significantly smaller than the signal...
A harmonic rejection mixer (HRM) with a programmable local oscillator (LO) frequency is presented. The design allows for the generation of multiple effective LO frequencies within a single HRM that are derived from a single primary clock frequency, without any modifications to the analog signal path. A 16-phase HRM with the proposed frequency synthesis technique is implemented in a 130-nm CMOS process...
A spectrum sensing technique based on cross-correlation that can be applied to cognitive radios for detection of weak signals is described. It is known that by cross-correlating the outputs of two signal paths, which have independent noise and correlated signals, the sensitivity of the detector can be enhanced. An analog approach to cross-correlation is employed, which avoids the requirement for high...
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