More Like this

1. Widely-Tunable RF Receiver Employing Synthetic Diversity for Interference Mitigation

   https://doi.org/10.1109/ISCAS48785.2022.9937610  

   Sadeghi, Sanaz; Soni, Sweta; Molnar, Alyosha (November 2022, 2022 IEEE International Symposium on Circuits and Systems (ISCAS))

   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. 

   more » « less
2. Suppression of cortical electrostimulation artifacts using pre-whitening and null projection

   https://doi.org/10.1088/1741-2552/acf68b  

   Lim, Jeffrey; Wang, Po T; Bashford, Luke; Kellis, Spencer; Shaw, Susan J; Gong, Hui; Armacost, Michelle; Heydari, Payam; Do, An H; Andersen, Richard A; et al (September 2023, Journal of Neural Engineering)

   Abstract Objective.Invasive brain–computer interfaces (BCIs) have shown promise in restoring motor function to those paralyzed by neurological injuries. These systems also have the ability to restore sensation via cortical electrostimulation. Cortical stimulation produces strong artifacts that can obscure neural signals or saturate recording amplifiers. While front-end hardware techniques can alleviate this problem, residual artifacts generally persist and must be suppressed by back-end methods.Approach.We have developed a technique based on pre-whitening and null projection (PWNP) and tested its ability to suppress stimulation artifacts in electroencephalogram (EEG), electrocorticogram (ECoG) and microelectrode array (MEA) signals from five human subjects.Main results.In EEG signals contaminated by narrow-band stimulation artifacts, the PWNP method achieved average artifact suppression between 32 and 34 dB, as measured by an increase in signal-to-interference ratio. In ECoG and MEA signals contaminated by broadband stimulation artifacts, our method suppressed artifacts by 78%–80% and 85%, respectively, as measured by a reduction in interference index. When compared to independent component analysis, which is considered the state-of-the-art technique for artifact suppression, our method achieved superior results, while being significantly easier to implement.Significance.PWNP can potentially act as an efficient method of artifact suppression to enable simultaneous stimulation and recording in bi-directional BCIs to biomimetically restore motor function. 

   more » « less
3. Synthetic Diversity To Mitigate Out-of-Band Interference in Widely Tunable Wireless Receivers

   https://doi.org/10.1109/IEEECONF44664.2019.9048662  

   Molnar, Alyosha; Boynton, Zachariah; Soni, Sweta; Sadeghi, Sanaz (November 2019, Synthetic Diversity To Mitigate Out-of-Band Interference in Widely Tunable Wireless Receivers)

   null (Ed.)

   Here we present a combined RF hardware/DSP technique to synthesize effective channel diversity in single-antenna wireless systems. This allows digital suppression of out-of-band interference artifacts in widely tunable wireless receivers with one or more antennas, including artifacts from LO phase noise. A passive inductor-capacitor (LC) network provides gain and phase diversity between channels and across frequency. Since amplitude and phase of in-band artifacts are set by the amplitude and phase of the out-of-band interference that generates them, they can be suppressed in DSP without knowledge about the interferer itself. The feasibility of this approach is demonstrated mathematically, with numerical system simulations, and full circuit simulation. 

   more » « less
4. Software Radio Testbed for 5G and L-Band Radiometer Coexistence Research

   https://doi.org/10.1109/IGARSS52108.2023.10283002  

   Al-Qwider, Walaa; Alam, A M; Farhad, Md_Mehedi; Kurum, M; Gurbuz, A C; Marojevic, Vuk (October 2023, ieeeXplore)

   Passive remote sensing through microwave radiometry has been utilized in Earth observation by estimating several geophysical parameters. Because of the low noise floor associated with the instrument (i.e., radiometer), the received geophysical emission is sampled in a protected band dedicated to remote sensing. This protected L-band occupying 1400-1427 MHz is also exciting and ideal for science because of lower attenuation from the atmosphere. This reason has also made this microwave region ideal for next-generation (xG) wireless communication. 5G cellular systems support two frequency ranges FR1 (0.45 GHz–6 GHz) and FR2 (24.45 GHz-52.6 GHz). Although operating bands are prohibited from conducting any up-link or down-link operations in the protected portion of the L-band, out-of-band (OOB) emissions can still have a significant impact on passive sensors because of the high sensitivity requirements related to science. This study will demonstrate a unique physical testbed that has the capability to observe in-band and OOB emissions in a protected anechoic chamber. Flexibility on transmitted waveforms and the potential to analyze raw measurements (IQ samples) of radiometers will help in designing onboard radio frequency interference (RFI) processing along with the coexistence of communication and passive sensing technologies. 

   more » « less
5. Artifact propagation in subdural cortical electrostimulation: Characterization and modeling

   https://doi.org/10.3389/fnins.2022.1021097  

   Lim, Jeffrey; Wang, Po T.; Shaw, Susan J.; Gong, Hui; Armacost, Michelle; Liu, Charles Y.; Do, An H.; Heydari, Payam; Nenadic, Zoran (October 2022, Frontiers in Neuroscience)

   Cortical stimulationviaelectrocorticography (ECoG) may be an effective method for inducing artificial sensation in bi-directional brain-computer interfaces (BD-BCIs). However, strong electrical artifacts caused by electrostimulation may significantly degrade or obscure neural information. A detailed understanding of stimulation artifact propagation through relevant tissues may improve existing artifact suppression techniques or inspire the development of novel artifact mitigation strategies. Our work thus seeks to comprehensively characterize and model the propagation of artifacts in subdural ECoG stimulation. To this end, we collected and analyzed data from eloquent cortex mapping procedures of four subjects with epilepsy who were implanted with subdural ECoG electrodes. From this data, we observed that artifacts exhibited phase-locking and ratcheting characteristics in the time domain across all subjects. In the frequency domain, stimulation caused broadband power increases, as well as power bursts at the fundamental stimulation frequency and its super-harmonics. The spatial distribution of artifacts followed the potential distribution of an electric dipole with a median goodness-of-fit ofR²= 0.80 across all subjects and stimulation channels. Artifacts as large as ±1,100 μV appeared anywhere from 4.43 to 38.34 mm from the stimulation channel. These temporal, spectral and spatial characteristics can be utilized to improve existing artifact suppression techniques, inspire new strategies for artifact mitigation, and aid in the development of novel cortical stimulation protocols. Taken together, these findings deepen our understanding of cortical electrostimulation and provide critical design specifications for future BD-BCI systems. 

   more » « less