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Existing beamforming arrays suffer from the size and cost of the RF front-end and digital back-end components. In this paper, a novel hybrid beamforming configuration for wideband receivers is introduced. The design replaces phase shifters and local oscillators (LO) with cross mixing antenna elements to maximize diversity gain. In this paper, an analytical model of the cross mixing beamformer (CMB) is first presented. Simulations are carried out showing that a maximum diversity gain can be achieved with the CMB approach. Two prototypes were implemented using $2\times 1$ and $4\times 2$ element arrays and tested at 2.31 GHz. Measured results show that CMB achieves coherent signal combining and can preserve the phase delay information needed for hybrid beamforming setups.

In this article, we present a clothing-integrated wireless power transfer and harvesting system that uses a novel class of anchor-shaped antennas for wireless power transfer up to the 4-ft distance. Notably, the system allows wireless charging during daily life activities, such as sitting on a chair or while lying on a fabric surface. Owning to up to a 4-ft power transfer, a user may also walk around during the wireless charging. The proposed system features a novel anchor-shaped antenna, which is miniaturized than a loop antenna and extends the range of fringing fields. Furthermore, a textile-based rectifying circuit with RF-to-dc conversion efficiency of 77.23% at 22.5 dBm is proposed. The efficiency remains better than 60% for an input power from 2 dBm to 24 dBm. For garment integration, a system consisting of a rectifier and an antenna were prototyped by using embroidered conductive thread on denim fabric. To understand the effectiveness, wireless power transfer tests are conducted under mechanical deformations and misalignments. The resulting prototype was tested for power transfer of several mW power over an area of 4 ft $\times4$ ft and by using a 1-W transmitter. This textile power harvesting system can be used as an ergonomic charging platform to supply power to a wide range of wearable medical, Internet of Things, and portable devices.

Communications at mm-wave frequencies and above rely heavily on beamforming antenna arrays. Typically, hundreds, if not thousands, of independent antenna channels are used to achieve high SNR for throughput and increased capacity. Using a dedicated ADC per antenna receiver is preferable but it’s not practical for very large arrays due to unreasonable cost and complexity. Frequency division multiplexing (FDM) is a well-known technique for combining multiple signals into a single wideband channel. In a first of its kind measurements, this paper explores FDM for combining multiple antenna outputs at IF into a single wideband signal that can be sampled and digitized using a high-speed wideband ADC. The sampled signals are sub-band filtered and digitally down-converted to obtain individual antenna channels. A prototype receiver was realized with a uniform linear array consisting of 4 elements with 250 MHz bandwidth per channel at 28 GHz carrier frequency. Each of the receiver chains were frequency-multiplexed at an intermediate frequency of 1 GHz to avoid the requirement for multiple, precise local oscillators (LOs). Combined narrowband receiver outputs were sampled using a single ADC with digital front-end operating on a Xilinx ZCU-1285 RF SoC FPGA to synthesize 4 digital beams. The approach allows $M$ -fold increase in spatial degrees of freedom per ADC, for temporal oversampling by a factor of $M$ .

We present an actively tuned balun to enable simultaneous transmit and receive (STAR) antennas to achieve greater isolation. Specifically, for the first time, we propose placing a chip into the antenna feed to control the amplitude of the current density. Nearly perfect balance of the feed currents enables STAR antennas to maintain strong isolation despite unpredictable fabrication imperfections. Two identical prototypes were fabricated for comparison, one passive and the other with active tuning inserted. Measurements demonstrate a minimum isolation of 42 dB across a 250 MHz bandwidth, representing an 11 dB improvement over the passive case. This is the best reported transmit/receive isolation enhancement to date. Further, this novel tuning method is significant because it enables STAR antennas with low-cost substrates, such as FR-4, to achieve greater isolation than passive designs. Notably, the balun was tuned across 1.68–1.93 GHz, part of the Federal Communication Commission's AWS-3 spectrum auction. Measurements show good comparison with simulation.

To date, CubeSat radars and imagers have been limited to operations beyond S-band due to the challenges associated with the design of wideband, compact, low-frequency antennas. Concurrently, the frequencies at VHF/UHF bands can image through clouds and foliage, and are very attractive for ice, water and biomass sensing. There is thus a need to develop wideband antennas that can operate at VHF/UHF bands which are low cost, light-weight, and packable. In this paper, we present a CubeSat deployable Tightly Coupled Dipole Array (TCDA) that achieves VSWR

In this paper, an algorithm using electrical capacitance tomography has been proposed to image and continuously monitor individual phases of a multiphase flow components. Instead of directly reconstructing the permittivity of the imaging domain, the proposed method presents successful reconstruction of fractional area/volume of each phase of a multiphase flow using only single frequency measurements. The permittivity image can then be calculated from the reconstructed fraction parameters. For the fraction reconstruction, the conventional cost function is reformulated and solved employing the well-known Landweber method typically used in ECT. Several three and two phase flow scenarios, including gas-oil-water process, have been analyzed and successful fraction parameter reconstructions are demonstrated. Apart from yielding successful reconstruction of individual phases, the proposed method also increases the overall accuracy of permittivity recovery consistently for all the explored cases. Hence, the proposed fraction imaging algorithm can potentially serve as a tool to decompose individual phases of a multiphase flow along with increased image accuracy.

An extremely wideband (EWB) antenna array is presented that covers the UHF to $C$ -bands (0.13–6 GHz). The array has dual-linear polarization and is capable of wide-angle scanning. Notably, this array achieves a 46:1 contiguous impedance bandwidth at broadside with VSWR $12\times12$ array prototype was fabricated and tested to verify the bandwidth and gain performance of a finite array. The simulated radiation efficiency was demonstrated to be 72% on average across the band.

According to a recent report [1], the United States is expected to see a fourfold increase in mobile data traffic between 2016 and 2021. Notably, the report suggests that an investment of roughly USd130-150 billion could be required over the next seven years, given that the current infrastructure is not adequate to support the expected growth in wireless data. Further, current transceiver architectures [2] are bulky, inefficient, and expensive.

An ultra-wideband (UWB) array is presented for UHF-S band (0.19–2.3 GHz) communications with an emphasis on dual-linear polarisation and wide-angle scanning. The array achieves 12:1 impedance bandwidth for a voltage standing wave ratio (VSWR)

A novel deployable inverted-hat monopole (IHM) antenna is presented for satellite applications. This frequency scalable antenna was designed and verified in very high-frequency (VHF) band (40–160 MHz) for 9U CubeSats and ultrahigh-frequency (UHF) band (200–600 MHz) for 1U CubeSats. The VHF band ultrawideband (UWB) monopole antenna operates from 40 to 160 MHz on an infinite ground plane, with emphasis on constant 5 dBi gain in a deployed volume of 60 × 60 × 100 cm. On a finite ground plane, the antenna achieves a 3.2:1 bandwidth with VSWR

Simultaneous transmit and receive (STAR) is attractive because it doubles spectral efficiency and alleviates radio frequency spectrum congestion. As expected, a major challenge in STAR is the high power leakage from the transmitter to the receiver, which dramatically reduces a receiver's dynamic range and then leads to desensitization. Therefore, it is paramount to ensure high transmit/receive (Tx/Rx) isolation. In this letter, we present a wideband STAR antenna array operating across 1.6–3.28 GHz (1 octave bandwidth), with a large transmit-to-receive isolation of 35 dB across the entire bandwidth. This is the first wideband and low, profile (λ/16 at the lowest frequency) STAR array retaining strong isolation when scanning down to 30° from broadside. The array elements are four-arm spirals, where two arms are for transmit and the other two for receive. To ensure high Tx/Rx isolation, symmetry is maintained everywhere in the structure, spiral arms, baluns, and feeds. The element spacing is kept at λ/2 at the highest frequency to avoid grating lobes. A 5 × 5 array prototype was built and tested to validate the design. Measurements show an excellent agreement with simulations.

In this article, we demonstrate flexible and lightweight textile-integrated rectenna arrays for powering wearable electronic devices. We propose a method to exploit large clothing-areas to integrate arrays consisting of $2\times2$ and $2\times3$ rectenna elements. Each element comprises a patch antenna and a rectifier which are fabricated using embroidery of conductive thread on the textile substrates. The rectifier used single-diode circuit configuration and showed a radio frequency (RF)-to-dc conversion efficiency of 70% for an applied input RF-power of 8 dBm at its input port. We also present several tests to demonstrate the applicability of the rectenna array. Specifically, in boosted-Wi-Fi modality, a dc power of $600~\mu \text{W}$ was collected at 10 cm from the source and $80~\mu \text{W}$ was collected at 60 cm from the source. These demonstrations show the proposed system’s applicability for charging and powering low-power wearable electronic devices.

With the growth of wireless data traffic, additional spectrum is required to meet consumer demands. Consequently, innovative approaches are needed for efficient management of the available limited spectrum. To double the achievable spectral efficiency, a transceiver can be designed to receive and transmit signals simultaneously (STAR) across the same frequency band. However, due to the coupling of the high power transmitted signal into the collocated receiver, the receiver's performance is degraded. For successful STAR realization, the coupled high-power transmit (Tx) signal should be suppressed by 100-120 dB over the entire operational bandwidth. So far, most STAR implementations are narrowband, and not useful for ultra wideband (UWB) communications. In this paper, we present a review of novel approaches employed to achieve improved cancellation across wide bandwidths in RF and propagation domains. Both single and multi-antenna systems are considered. Measurements show an average cancellation of 50 dB using two stages of RF signal cancellation.

Electrical activity recordings are critical for evaluating and understanding brain function. We present a novel wireless, implantable, and battery-free device, namely the Wireless Neurosensing System (WiNS), and for the first time, we evaluate multichannel recording capabilities in vivo. For a preliminary evaluation, we performed a benchtop experiment with emulated sinusoidal signals of varying amplitude and frequency, representative of neuronal activity. We later performed and analyzed electrocortical recordings in rats of evoked somatosensory activity in response to three paradigms: hind/fore limb and whisker stimulation. Wired recordings were used for comparison and validation of WiNS. We found that through the channel multiplexing element of WiNS, it is possible to perform multichannel recordings with a maximum sampling rate of ∼10 kHz for a total of eight channels. This sampling rate is appropriate for monitoring the full range of neuronal signals of interest, from low-frequency population recordings of electrocorticography and local field potentials to high-frequency individual neuronal spike recordings. These in vivo experiments demonstrated that the evoked neuronal activity recorded with WiNS is comparable to that recorded with a wired system under identical circumstances. Analysis of critical parameters for interpreting the somatosensory evoked activity showed no statistically significant difference between the parameters obtained by a wired system versus those obtained using WiNS. Therefore, WiNS can match the performance of more invasive recording systems. WiNS is a groundbreaking technology with potential applications throughout neuroscience as it offers a simple alternative to address the pitfalls of battery-powered neuronal implants.

In this paper we propose a new class of anchor-shaped antenna referred to as corrugated-shank anchor-shaped suitable for angular misalignment resilience. This new topology to operate at 360 MHz differs from previously published anchor-shaped antenna [1] by introducing corrugations in the shank of the anchor for stronger magnetic fields. The results suggest a 10% of power transfer efficiency (PTE) improvement with respect to that of the generic anchor. This improvement is achieved when considering misalignments in the elevational direction. This design can be used as a guideline for future misalignment-free wireless charging modalities integrated into clothing.

A novel four-channel receiver architecture is proposed using an orthogonal coding scheme for low-cost and low complexity millimeter-wave (mm- Wave) digital beamforming. In this proposed architecture, multiple signals are encoded with othogonal Walsh-Hadamard (WH) codes and multiplexed into a single channel. The combined signal is fed into a single Analog-to-Digital converter (ADC) at the digital baseband, leading to significant reduction in size, weight, power and cost (SWaP-C). As a result, the hardware complexity of the receiver is reduced by more than 95 %. A key challenge addressed in this paper is the signal-to-noise ratio (SNR) degradation due to inter-channel interference. Interference is greatly dependent on the choice of the employed orthogonal WH codes. In this paper, we introduce methods to achieve greater than 30 dB inter-channel interference rejection across a bandwidth of 400 MHz. As such, the proposed reduced SWaP-C and interference mitigation can have a major impact in realizing innovations for the 28-GHz and beyond mmWave links.

Flexible electronics have proven their usefulness for applications where bendability, stretchability, wearability, portability, and lightness are needed. These include wearable health and fitness sensors as well as foldable and deployable antennas for space and aerospace utilization. A common approach for realizing flexible electronics is to employ plastic substrates and print circuits on them. However, an alternative and more adaptable approach consists in using textile substrates. The latter offers the same advantages as plastic and mylar substrates but is better suited for wearable applications considering how effortlessly textiles can be integrated into clothing. Since textile substrates have already demonstrated reliable performance up to 6 GHz, they are also suitable for radio frequency (RF) applications. Nevertheless, creating textile electronics with optimal RF characteristics presents its own challenges, ranging from conductivity characterization to durability. The fabrication process can have a major impact on the properties of the textile substrate and associated printed electronics, and this will be the focus of our work.

Advances in Electro-Optics (EO) in terms of materials and micro-and-nanofabrication processes have provided new capabilities for EO sensing devices. These new capabilities include increased sensitivity, tolerance to electromagnetic interference, and higher bandwidth performance. One such widely used device is the electro-optic modulator (EOM). EOM makes use of an incident RF signal to modulate an optical carrier. In a functional EOM, the modulation take place within the active optical area of the nonlinear EO device material. These nonlinear EO materials have an electro-optic effect properties. Examples of these materials are nonlinear polymers and lithium niobate (LN).

To meet the ever-increasing consumer needs, new wireless applications including IOT are being developed at a tremendous pace. However, only a very small percentage of spectrum is available to accommodate these applications. Specifically, wireless applications targeting sub-6 GHz frequency band require efficient hardware infrastructures and protocols to operate in the highly congested spectrum, to avoid signal fratricide. Consequently, there is a strong need to develop spectral efficient full duplex communication techniques [1] .

We describe a CubeSat constellation integrated with ultrawideband (UWB) multiple input and multiple output (MIMO) radars operating over the frequency range of 50–600 MHz for remote sensing of large ice sheets on the Earth, as well as distant planets and moons. It can be used for measurements of ice thickness and basal conditions of Antarctica and Greenland ice sheets, the mapping of lunar lava tubes, and sub-surface detection/characterization of volatiles on Mars. In this paper we provide a short discussion of the science requirements and conceptual design of a constellation of CubeSats with UWB MIMO radars for sounding ice and mapping of lava tubes.

In this paper, a battery-less and wireless smart bandage is proposed, where the RF and sensor circuit are wirelessly powered, and the sensor data is modulated and wirelessly collected. The sensor is designed with minimalistic electronics to interface to tri-electrode electrochemical sensors. The RF electronics, power telemetry and data-communication antennas are realized via conductive thread embroidery on fabric substrate. The wireless power transmitter operates at frequencies between 350 MHz to 573 MHz, while the return communication signal path is designed to be around 915 MHz. The bandage electronics feature a rectifier for RF-to-DC conversion of received RF power, used for driving a voltage-controlled oscillator (VCO) and electrochemical sensor. It is demonstrated that restored wound, emulated by a resistive load, yields a modulated frequency of 845 MHz, which is tunable based on value of resistive load and wirelessly collected by a remote receiver at 3 ft. away from the bandage. This modulated frequency corresponds to a tuning voltage of 0.1 V for the VCO. The VCO consumes a total DC power of less than 6 mW. This is the first time a battery-less wirelessly powered smart bandage is demonstrated and this result can be served as a foundation for remote sensing of chronic wounds in the near future.

Miniaturized 3D package integration with piezo-magnetostrictive telemetry is analyzed towards advanced wireless medical systems. The paper is composed of three aspects. The first is to analyze telemetry using a multiferroic or piezo-magnetostrictive power interface. Parametric analysis was performed to estimate the impact of material, geometry and input magnetic fields. The second aspect is the process integration of devices and telemetry interfaces in 3D embedded packages for smallest form-factors. The telemetric interface and sensor devices are packaged in a flexible substrate with 3D interconnections, leading to miniaturized solutions. The sensor-communication and the power source flex layers are separately fabricated and connected with via-fill layers that are flex-compatible. Flex integration allows the devices to be functional on curved surfaces. In the final part, coupled magnetostrictive and piezoelectric films were considered to power devices in neural recording, neurostimulation and biophotonic systems. Power analysis requirements and piezo-magnetostrictive solutions for these specific scenarios is shown to illustrate the geometric compatibility towards emerging needs.

Implantable systems are often employed to perform continuous high-resolution recordings of neural activity. These systems frequently require invasive procedures when implanting and maintaining effective operation. This causes major interruptions to daily life. Previous work demonstrated an in vitro minimum detectable signal of 15 μ V in amplitude and RF sensitivity down to –135 dBm. This suggests the possibility of detecting diminutive biopotentials in a wireless fully passive manner. Here, for the first time, we validate the wireless neurosensing system through a series of in vivo electrophysiological recordings including both spontaneous cardiac activity and sensory evoked neural activity, with amplitudes ranging from a few microvolts to millivolts and across a spectrum of frequencies. We also present design considerations and the development of probes for neurosensing to accomplish detectability of biopotentials in the tens of microvolts in rats. The developed probes show improved impedance matching with the neurosensing system. Specifically, the new probes showed an impedance several orders of magnitude lower than those commercially available, thereby significantly improving signal detection. Notably, the presented in vivo validation of this technology has great future clinical implications in neuroscience as it offers a wireless and unobtrusive device for neurological research, monitoring, and therapeutic purposes.

We present, for the first time, a novel dual-linear polarized tightly coupled dipole array with integrated balun operating across a 9:1 bandwidth, from 2 to 18 GHz. This dual-linear polarized array employs a tightly coupled dipole topology and scans down to 60° from boresight. The overall geometry consists of cross-located tightly coupled dipoles integrated with a folded Marchand balun that serves as an impedance transformer to achieve a wideband feeding network. Notably, the traditional dielectric superstrate is replaced with double layers of frequency selective surfaces to enable scanning down to 60° in both E-, H-, and diagonal (D)-planes across the entire band. The design achieves VSWR $\lambda _{low}$ /10). The design is validated through fabrication and testing of an $11 \times 11$ prototype. The measurements of this prototype are presented and are in good agreement with simulations.

In this paper, we present the design, fabrication, and measurement of an ultra-wideband phased array antenna, with continuous coverage of all six allocated fifth generation and industrial, scientific, medical bands in the millimeter-wave spectrum. Of importance is that the complete array is co-fabricated as a single printed circuit board using commercial processes, implying a significant reduction in cost over previous microfabrication-based designs. The design is demonstrated in simulation to operate across 24–72 GHz with VSWR $3\times 3$ array prototype, which shows close agreement to the simulated values.

We propose a novel multi-channel (eight channels) passive neuro-sensing system for wireless acquisition of brain signals as low as 20 $\mu V_{\text{pp}}$ . Compared to previous batteryless multi-channel neuropotential sensors, the proposed design exhibits 28 times better sensitivity, $\sim$ 2 times smaller footprint, and scalability to 100s or even 1000s of channels. The proposed system consists of an external interrogator and a neuro-recorder implanted inside the scalp. For operation, the interrogator first sends a 2.4 GHz carrier signal to “turn on” the implant and, second, an infrared control signal for channel selection. The latter activates the desired channel via a photo-activated multiplexer. For this channel, the carrier signal is mixed with the neural signal ( $f_{\text{neuro}}$ ) to generate a 4.8 $\text{GHz}\pm f_{\text{neuro}}$ modulated signal. The latter is then transmitted back to the interrogator. To verify the implant's operation inside biological tissues, $in$ $vitro$ measurements are presented using pig skin. Experimental results show that the proposed neuropotential recorder exhibits 20 $\mu V_{\text{pp}}$ sensitivity at all eight channels (viz. it can record any signal generated by the human brain). The system is also in compliance with the strictest Federal Communications Commission standards for patient safety. Notably, the proposed approach is scalable to a much higher number of channels. As such, the proposed system can be a game-changing capability for a wide range of applications.

Use of the millimeter wave spectrum is essential for the success of 5G and beyond communications. Modern millimeter wave arrays suffer from bandwidth limitations due to dielectric loadings. In this paper, the latter is compensated with a higher order Marchand balun in each element of a tightly coupled dipole antenna array (TCDA). The array operates from 53–100GHz at boresight with a VSWR < 2. When scanning 45° from broadside in the E and D-planes a VSWR < 3 is maintained, and the same holds for up to 30° in the H-plane. The array has an impressive cross-polarization purity of over 65dB across the bandwidth. Moreover, the array exhibits over 84% efficiency across the band. It is designed and fabricated on Tachyon ISO 100 and copper features are within commercial PCB limitations. Furthermore, the array is designed for flip-chip technologies and in a triangular lattice for 15% phase shifter count reduction.

Communication systems of the future will require hundreds of independent spatial channels achieved through dense antenna arrays connected to digital signal processing software defined radios. The cost and complexity of data converters are a significant concern with systems having hundreds of antennas. This paper explores frequency division multiplexing as an approach for augmenting the baseband signals of multiple antenna channels such that a single ADC can sample a multitude of antennas in an array. The approach is equally applicable to both massive MIMO and mm-wave digital wireless arrays. An example design based on Xilinx RF SoC for combining 4 antenna channels at 28 GHz into a single ADC is provided.

Sub-terahertz (sub-THz) systems are ideal for implants that require continuous high-resolution sensing and wireless communications for diagnostics. There is also a need for these systems to be small, cost-effective, and of bio-compatible material. Here, we present an antenna array that is capable of sub-THz operation (0.063-0.212THz) and is small in size with a $\mathbf{5\times 5}$ configuration $\mathbf{(2.85{mm}\times 2.85{mm})}$ , or a $\mathbf{3\times 3}$ array $\mathbf{(1.7mm\times 1.7mm)}$ . Furthermore, the antenna uses a low-cost polymer as substrate and superstrate. This ensures efficient high frequency operation and bio-compatible packaging while maintaining a profile of 0.38mm. The array has dual-linear polarization and achieves a 3.4:1 contiguous impedance bandwidth at broadside with a voltage standing wave ratio (VSWR) $\mathbf{ across the entire band under a 0.07mm epidermis layer. Similarly, the antenna achieves a 3.2:1 bandwidth with VSWR $\mathbf{ for a 0.015mm layer of stratum corneum. Full-wave simulation of the array demonstrates $\mathbf{>70 \%}$ efficiency across the entire band for both conditions. A 60dB polarization purity is also achieved.

A wireless neurosensing system (WiNS) adapted with a novel impedance matching network is presented and validated. This system is used in vivo to record for the first time spontaneous neural unit activity from the hippocampus of a Wistar rat. These extracellular spikes offer valuable information. However, they are challenging to observe, even more so with previously reported neurosensing systems due to impedance mismatches with the required neural probes. The notable result demonstrated here employed (a) recently proposed technique for passive impedance matching, and (b) newly explored impedance reducing electrochemical probe coating method. The proposed technology has revolutionary potential in neurological research, particularly in epilepsy studies.

In this paper, we demonstrate a fabric-integrated, near-zone wireless power transfer system, which uses a newly developed misalignment resilient antenna element for inductive power transfer in wearable applications. The antenna consists of an anchor-shaped geometry, which uses a combination of electric and magnetic field couplings in the near field to achieve high power transfer efficiency (PTE) of 85% even under lateral misalignment. Improvement in PTE for lateral and angular misalignment cases is demonstrated which facilitates the near-zone power transfer for practical usecases. For fabric integration, the proposed antenna and rectifier system were fabricated on a textile substrate by using conductive thread embroidery. We report the PTE of the developed antennas variation with different types of misalignment cases. For lateral misalignment, the proposed antenna exhibited an average PTE of 85% for lateral movements of 1 to 10 cm, Furthermore, the antennas exhibited an average PTE of 70 % for elevation and 60 % for azimuthal misalignment cases. These results are compared with circular loop resonator illustrating the improvements in the PTE. Using this antenna element, power harvesting system and its resilience to misalignment are also demonstrated.

Tighly Coupled Dipole Arrays (TCDA) are ultra wideband conformal antennas of low profile. Contiguous bandwidth greater than 10:1 have been reported that reach the Bode-Fano limit. In this paper, we present an active approach to further increase the bandwidth of TCDAs using tunable Frequency Selective Surfaces (FSS) and Artificial Electromagnetic Conductors (AMC). Preliminary results led to a dual-polarized Active TCDA (A-TCDA) that covers the entire UHF band (0.2-2.8GHz).

Biodegradable materials have amassed attention for frugal green electronics applications to better assist underserved communities. In this paper, we design a frugal radio frequency (RF) energy harvesting system as a low-cost power supply for low-power on-body sensors. The system involves a loaded dumbbell antenna integrated with a single diode rectifier. The dumbbell antenna is outfitted with loaded rings and a ground plane spaced A/4 away (viz. 2.45GHz). Indeed, both were fabricated using cardboard substrate and copper tape as a conductor. The measurements suggested that the rectenna exhibited an excellent RF performance as well as a good RF-to-DC conversion. That is, excellent S 11 of less than −20 dB and a realized gain of 9 dBi and $15\mu W \ \ \mathrm{for}\ \ 25\mu W/cm^{2}$ RF power density, which is the equivalent of a figure-of-merit (EFOM) of 11.7 dB. This design is very attractive due to the fact it can be used in rural area and the materials used to assemble the device can be later recycled for other purposes.

Further advances in satellite communication and imaging will rely on the implementation of sub-terahertz (sub-THz) systems using flip-chip technology. Recently, low-cost organic substrates have demonstrated stable electric properties over a very large bandwidth making them suitable for sub-THz antennas. In this paper, we present the first ultra-wideband sub-THz antenna array implemented on a low-cost organic multilayer printed circuit board substrate. The array has dual-linear polarization and achieves a 3:1 contiguous impedance bandwidth at broadside with $\text{VSWR} across the entire band. Full-wave simulation of the array demonstrates >80% efficiency across the entire band.

A unique system, namely the wireless neurosensing system (WiNS) is tested, for the first time, in a freely moving animal. WiNS was designed to sense neural signals in a battery-free manner, without using complex electronics, and by integrating the key components: (a) implant and external interrogator, (b) neural probes, and (c) demodulation circuit. In this paper, a set of in vivo experiments are carried out to demonstrate recovery of neural signals associated with transitions among states of awareness, and while alternating between resting and walking, i.e. in a freely moving rat. These first ever results were made possible by (a) newly developed low-impedance neural probes to closely match the impedance of WiNS and (b) realization of a new custom 3D printed cap. The collected signals provide concrete proof of this technology's pertinent role in neuroscience.

Wearable electronics must be both flexible and robust so that they can be form fitting and reliable. The first of these were fabricated with printed conductors on rubber, plastic, and other polymer substrates. More recently, conductive textiles have been preferred due to their 1) inherently flexible and lightweight physical properties, and 2) low-loss, low-dielectric electrical properties. However, a variety of challenges persist when implementing wearable textile electronics, with necessary trade-offs between conductivity, durability, and flexibility. Consequently, there is still a need to develop optimal metallization approaches. In this paper, six different textile-compatible metallization techniques are presented. These include adhering copper tape, silver paint, silver thread, silver-painted silver threads (SPST), copper mesh, and silver-painted copper mesh (SPCM) to a denim stack-up. Microstrip transmission line (TL) prototypes were fabricated with each method, and analyzed to determine which textile-compatible metallization technique had the best performance in comparison to a TL on standard printed circuit board (PCB). Measurements show that the denim TL with SPST conductors had the smallest losses versus the PCB standard, with only an average loss of 0.03 dB/cm from 0.5 to 3 GHz.

The need for high data rate communications has led to the exploration of the millimeter-wave (mm-wave) spectrum. But, significant losses at these frequencies imply high gain phased array antennas. Concurrently, low cost fabrication and beamforming across wide bandwidths is a foundational challenge. In this paper, we present a novel hybrid beamforming design using the concept of element-to-element mixing for the signal delay compensation. Notably, our novel architecture eliminates bulky phase shifters and local oscillators. Further, our system is combined with a baseband on-site coding technique for further hardware and cost reduction. Studies show that our design offers unparalleled flexibility in signal reception and promises 95% reduction in cost and power consumption.

We present an actively tuned balun to enable Simultaneous Transmit and Receive (STAR) antennas to achieve greater isolation. Specifically, for the first time, we propose placing an active chip into the balun feed to control the amplitude and phase of the current density. Nearly perfect balance of the feed currents enables STAR antennas to maintain strong isolation despite fabrication imperfections and unpredictable environmental reflections. Measurements demonstrate 42 dB isolation across a 250 MHz bandwidth, representing an 11 dB boost. This is the best reported transmit-receive isolation improvement to date. Notably, the balun was tuned across 1.68-1.93 GHz. A prototype was fabricated and measurements show good comparison with simulation.

Ultra-wideband (UWB) radios provide avenues for interference immunity using spread spectrum (SS) techniques. Doing so, provides a processing gain of 21 dB, allowing for successful retrieval of signals propagated below the noise floor. In addition, by applying advanced channel coding an additional coding gain of 9 dB can be achieved. In this paper, we are exploiting SS techniques with channel coding to maximize gain in wireless communication links. Bit error rate (BER) performance is presented for multiple channel coding approaches.

We propose a cost-efficient smart textile electronic (textronic) for wound healing assessment. This assessment is done by reflection of the modulated wound-data to the interrogator. The RF modulation of the data is done by a textile-based voltage-controlled oscillator (VCO) that takes the electric signal provided by electrochemical sensing of the uric acid found in the wound fluid. The assessment was done based on a threshold found to be 0.4 mM respect to which the severity or restoration of the damage wound is evaluated. The average sensitivity of this system is 44.67 MHz/mM and the maximum power consumption 0.38 mW. It uses low-cost materials and it is easy to manufacture and use by any patient or medical professional.

This paper presents a foldable Tightly Coupled Dipole Array (TCDA) implemented on a Miura-Ori pattern. This array achieves a wide broadside bandwidth of 5.4:1 (viz. 1.14 GHz – 6.16 GHz) with $\text{VSWR} . This paper is the first to show the foldability of a Miura patterned TCDA using standard printed circuit board (PCB) substrates and practical feeds. A simple differential pair of conventional $50-\Omega$ coax cables are included, with low profile snap-on connectors to enable foldability.