A sub-nanoliter, light-tolerant (780 µW/mm2), and power-adaptive forward-bulk optoelectronic microsystem for tetherless neural recording is presented. The CMOS bulk is used as a power harvester to utilize photogenerated carriers and a lower transistor threshold voltage for low power design (~0.3 µA at ~0.32 V). Increasing optical power boosts the system bandwidth to 14 kHz and the sampling frequency to 18.2 kHz, while maintaining the integrated input-referred noise (~10 µVRMS) stable, with an NEF of 2.34.

This paper presents a novel system architecture to suppress in-band artifacts (IBAs) generated from out-of-band (OOB) interferers, including reciprocal mixing by the local oscillator’s (LO) spurs and phase noise (PN), third-order intermodulation (IM3) artifacts, and harmonic down-conversion (HDC) artifacts. Theory and design procedure are explained, and measurement results from a prototype taped out in 45 nm RF SOI process are presented. The receiver was designed for the frequency range of 1.2 GHz–2.4 GHz and achieved a noise figure (NF) of 3.1 dB–6.2 dB, blocker −1 dB compression point (B1dB) of −10.3 dBm, and OOB third-order input-referred intercept point (IIP3) of 9.3 dBm on average, before artifact suppression. Measurements were performed on 16-quadrature amplitude modulated (16QAM) signals with modulated and unmodulated OOB interferers to show artifact suppression for various kinds of IBA. For each IBA, artifact suppression performance was assessed across frequency and interferer power. Interference tolerance improvement of up to 38 dB was achieved. Additionally, reconstruction of the artifacts for the cases of spur and HDC was demonstrated, showing simultaneous recovery of two signals, providing a form of carrier aggregation.

This paper presents a novel technique for suppression of in-band artifacts from out-of-band (OOB) interference in widely tunable RF receivers. The technique employs a multi-tap inductor-capacitor network (LCN) to generate diversity in gain and phase between taps across the targeted frequency range. Using this network to feed a bank of identical receivers sharing a single local oscillator (LO) allows multiple kinds of interferer artifact to be suppressed. Here we considered spur-induced and phase noise-induced artifacts. In each case, the resulting artifacts are linearly separable from signal when the outputs of the sub-receivers are recombined. AC and transient simulations were first performed to show feasibility of the proposed approach. A prototype was implemented in 45nm CMOS which confirmed the validity of the synthetic diversity (SD) approach for suppressing interferer artifacts, showing a maximum lowering in EVM and BER of 38% and 60% respectively.