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A microfluidically reconfigured, frequency tunable meandered dipole antenna is presented. Frequency tunability is achieved through a selectively metallized plate within the microfluidic channel acting as a parasitic RF shorting switch. The microfluidic channel is fabricated on polydimethylsiloxane (PDMS) and bonded onto the antenna substrate using a 12 µm thin low loss benzo-cyclobutene (BCB) layer...
We present new processes for fabricating: (a) stretchable and flexible antennas on electrically-conductive fibers (E-fibers), and (b) E-fiber antennas with high geometrical accuracy. Optionally, these two processes can be concurrently employed to enable stretchability and flexibility for antennas that operate in extreme environments. Additionally, the proposed approach provides high geometrical accuracy...
Ultra-wideband (UWB) arrays are desirable for multi-functional apertures utilizing multiple beams, polarizations, and frequency bands to enable diverse communication and remote-sensing capabilities. The desired bandwidth, compactness, and scanning capability are often mutually conflicting. Here we present our current and previous work on developing arrays with 7∶1 (loss less) and 14∶1 (with R card)...
A new embroidery process with a geometrical accuracy of 0.1mm is presented for textile antennas and circuits. Previous embroidery processes employed thicker E-fibers leading to resolution not better than 0.3mm. By employing a novel class of much thinner E-fibers we improved geometrical accuracy by a factor of 3. Measurement and calculation results show that the proposed process achieves similar RF...
We present a wideband Tightly Coupled Dipole Array (TCDA) with integrated balun and novel parasitic superstrate capable of wide angle scanning. Although previous TCDAs have been shown to have good scanning performances, use of dielectric superstrates are required, implying additional costs and weight. In this paper, we replace the solid dielectric with parasitic periodic elements for wide angle and...
Ultra-wideband (UWB) systems combined with the advances in digital signal processing and data handling have drastically reduced the complexity of cognitive and software defined radios. Therefore, techniques such as monopulsing, multiple beams, among others, can be implemented for phased arrays and Multiple Input Multiple Output (MIMO) systems. A major drawback in MIMO systems is hardware redundancy...
We propose a bandwidth reconfigurable spatial filter using frequency selective surfaces (FSS) combined with phase-change materials (PCMs), vanadium dioxide (VO2) for advanced terahertz (THz) applications. The FSS filter is simulated using sapphire as substrate and employs circular loops FSS with VO2 rings in between. Simulations of this filter show bandwidth difference in the frequency range of 0...
A mechanism for tunable band rejection within an ultra-wide bandwidth, 0.6–4GHz (6.7∶1), of a tightly-coupled array (TCA) is presented. Specifically, a variable capacitor, placed in the folded Marchand balun, feeding the array, is used to create a tunable mismatch resonance. Both the center frequency and the bandwidth of the resonance can be controlled via the capacitor value and position, respectively...
We present a new class of well-tested and verified electronic textiles. These are comfortable to wear and of low-cost, but still provide RF performance similar to their copper counterparts. To form conducting textile devices, metal-coated polymer E-fibers are densely and precisely embroidered onto everyday garments. This is done using a programmable sewing machine for automated fabrication. The proposed...
Wireless biomedical telemetry between a fully-passive brain implant and an exterior interrogator is presented. A key aspect of the proposed implant is minimization of losses to wirelessly record neurological signals as low as 50 µVpp for the first time. To achieve this, we employed an implanted patch with a novel mixed architecture, and an interrogator spiral antenna. All components were integrated...
A new class of reconfigurable frequency selective structures (FSSs) is proposed to operate across a wide band of frequencies. Specifically, thick FSSs are proposed with several desirable properties, including sharp roll-offs for narrow rejections. Similar to multi-stage filters, this higher-order selectivity enables frequency and bandwidth control. However, practical application requires the ability...
Simultaneous transmit and receive systems (STAR) are proposed to double the spectral efficiency and enhance spectrum utilization in the traditional microwave band. A major problem is high power self-interference (SI) due to the proximity of the transmit and receive antennas. In this paper, we propose to significantly improve system-level performance using a novel high isolation RF front-end based...
This paper introduces a feeding concept aimed at simplifying the backend (phase shifters) of traditional phased arrays. As an alternative to traditional phased arrays, we employ a traveling wave array (TWA) using a single feedline whose propagation constant is controlled via a single, small mechanical movement without a need for phase shifters to enable scanning. Specifically, a dielectric plunger...
We present a novel antenna element design for arrays. The planar radiating element is dual-polarized, probe-fed, with simplified integrated feed layers and a radome layer for environmental protection. A particular characteristic of the proposed design is its low cost approach by employing FR4-only substrates throughout the printed circuit board stack. The radiating antenna element has an active VSWR<1...
We present a novel conformal, lightweight and load bearing spiral antenna on textiles for conformal applications. The antenna and its integrated planar balun were embroidered using a standard sewing machine with very thin (diameter=0.22mm) Liberator™ E-fibers. There fibers can achieve geometrical accuracy down to 0.3mm and even 0.1mm. This is a 3 fold geometrical accuracy improvement over previous...
Planar arrays that exploit strong intentional coupling between elements have allowed for very wide bandwidths in low-profile configurations. However, such designs also require complex impedance matching networks that must also be very compact. For many space applications, typically occurring at C-, X-, Ku-, and most recently at Ka-band, such designs require specialized and expensive fabrication techniques...
A high electron mobility transistor (HEMT) configuration is proposed using multiple mutually coupled 2DEG layers to detect plasma waves at room temperatures. We show a 6 dB improvements in the transmission spectra, as opposed to single 2DEG layer, using a 4 channel HEMT configuration. To conduct this analysis, we developed and present a full-wave numerical model for self-consistent solution of the...
The accuracy of a conformal sensor for biomedical imaging is assessed. This imaging sensor is used to extract the electric properties of deep human tissues It operates at 10 MHz and consists of 20 indiridual probes for detecting vicinity electric fields. Each probe can be excited independently while the others are in the receive mode. Received data are used to determine the coefficients of a linear...
We present a novel wearable monitoring system to image the dielectric properties of internal body tissues pixel-by-pixel, and effectively determine irregularities in real-time. The proposed system consists of a flexible wearable sensor and a dielectric constant extraction technique. A set of on-body electrodes is employed to obtain scattering parameters used to extract the electrical properties of...
To minimize self-interference in Simultaneous Transmit and Receive (STAR) communication systems, multi-tap analog cancelling filters are employed to emulate coupling between transmit and receive antennas. This paper presents the design and simulation of a fourth-order analog filter incorporating variable delays and coefficients to approximate antenna coupling. System simulations show that the developed...
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