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3D printing has enabled materials, geometries and functional properties to be combined in unique ways otherwise unattainable via traditional manufacturing techniques, yet its adoption as a mainstream manufacturing platform for functional objects is hindered by the physical challenges in printing multiple materials. Vat polymerization offers a polymer chemistry-based approach to generating smart objects, in which phase separation is used to control the spatial positioning of materials and thus at once, achieve desirable morphological and functional properties of final 3D printed objects. This study demonstrates how the spatial distribution of different material phases can be modulated by controlling the kinetics of gelation, cross-linking density and material diffusivity through the judicious selection of photoresin components. A continuum of morphologies, ranging from functional coatings, gradients and composites are generated, enabling the fabrication of 3D piezoresistive sensors, 5G antennas and antimicrobial objects and thus illustrating a promising way forward in the integration of dissimilar materials in 3D printing of smart or functional parts. 3D printing has enabled materials, geometries and functional properties to be combined in unique ways but printing multiple materials remains challenging. Here, the authors demonstrate how spatial distribution of different material phases can be modulated by controlling the kinetics of gelation, cross-linking density and material diffusivity in vat polymerization.

Phase shifters are essential components of phased array systems, which are crucial to radar and wireless communication systems. New-generation telecommunication and radar systems often require strict phase shifter performance metrics, such as phase resolution and bandwidth, to perform fine beam scanning, which helps increase pointing accuracy. Meanwhile, practical vector modulator phase shifters, which employ quadrature signal operation, typically have digital control below 7 bits. In this regard, a vector modulator phase shifter based on non-quadrature signal operation and covering the lower S-band and upper C-band is proposed and implemented in this work. The proof-of-concept printed circuit board (PCB) prototype exhibits more than 360° continuous phase shift with more than 50% fractional bandwidth. In addition, it achieves a median gain of 0.8 dB and a size of 0.9 λg2 with the inclusion of an output gain-block amplifier. The relatively wider bandwidth, smaller size, and fine resolution of the proposed phase shifter approach make it a potential candidate for new-generation ultrawideband communication and radar systems.

This paper presents PCB design solutions for implementing a radiative-field RF energy harvester with an ASK-PWM decoding communication scheme using available commercial components. The paper provides the design approach and tackles key challenges such as the impact of inductive parasitic effects at the output of the harvester, how to maintain the PCE at a constant value regardless of the time constant at the output of the communication path’s rectifier, and the difficulty of changing the aspect ratio of the discrete inverter used for PWM decoding. These challenges are addressed by using multiple capacitors connected in parallel at the output of the rectifier to reduce inductive parasitic effects, adding a series resistor in the communication path’s rectifier to isolate its loading from impacting the PCE, and utilizing a potentiometer in the inverter to realize PWM decoding on PCB. The system was manufactured using FR-4 substrate material with a size of 5 cm × 4 cm × 0.6 cm, harvesting energy at the ISM frequency of 924 MHz with a PCE of 42.12% at a bit rate of 15 Kbps. Moreover, the system consumes only 355 μW of power and maintains correct harvesting and decoding operation in the antenna separation range of 6–12 cm. This work aims to provide an alternative to IC realization by implementing the system entirely using commercial discrete components, reducing costs, adding flexibility, reducing development time, and allowing for simple debugging.

In this paper, a method to reduce mutual coupling between an E-plane and H-plane coupled microstrip patch antenna is presented. Two dual differentially fed square patches are designed in a 1 × 2 antenna array configuration. To minimize mutual coupling and its effects, coupled split-ring resonators (SRRs) are designed, characterized and positioned between the patches. Circular SRRs are designed and coupled to produce a band-stop response to suppress surface waves propagating within the dielectric substrate while enhancing isolation. Mutual coupling interactions and the suppression mechanism are discussed in relation to the patches and SRRs. The patch radiators are dual differentially fed to achieve polarization diversity. E- and H-planes decoupling is achieved between the two patches throughout their bandwidth while maintaining good antenna performance. A prototype of the antenna array and the SRR is fabricated and measured to validate the decoupling approach. With a separation distance of 0.49λ between the patches, the measured S-parameters show an impedance bandwidth of |S11|≤−10 dB, covering 9.27–9.46 GHz, and −38 dB and −35 dB mutual coupling for E- and H-planes, respectively, are observed throughout the antenna operating bandwidth.

After demonstrating, in previous works, the proof of concept of adaptive rectifiers with active load modulation to operate simultaneously for short/long range RF Wireless Power Transfer (WPT) while maintaining a high Power Conversion Efficiency (PCE), the authors introduced in this paper a power link budget of the proposed adaptive rectifier with a compromise between distance and efficiency. Then, to further exhibit its capabilities and enhance its performance, this paper first introduced a discussion about the parameters preventing the rectifier from operating over a wide range of input powers was performed. Furthermore, active load modulation was implemented and its co-simulation results presented. Finally, an adaptive rectifier was fabricated and its results successfully compared to measured data. It exhibits 40% of PCE over a wide dynamic input range of incident RF power levels from −6 to 25 dBm at the 900 MHz in the Industrial Scientific Medical band (ISM band), with a maximum PCE of 66% for an input power of 15 dBm. The proposed devices are therefore suitable for WPT applications to harvest energy from a controlled source.

We present a low-cost millimeter-wave frequency synthesizer with ultralow phase noise, implemented using system-on-package (SoP) techniques for high-data-rate wireless personal area network (WPAN) systems operating in the unlicensed 60 GHz ISM band (57–64 GHz). The phase noise specification of the proposed frequency synthesizer is derived for a worst case scenario of an 802.11.3c system, which uses a 64-QAM 512-carrier-OFDM modulation, and a data rate of 5.775 Gbps. Our design approach adopts commercial-of-the-shelf (COTS) components integrated in a low-cost alumina-based miniature hybrid microwave integrated circuit (MHMIC) package. The proposed design approach reduces not only the system cost and time-to-market, but also enhances the system performance in comparison with system-on-chip (SoC) designs. The synthesizer has measured phase noise of -111.5 dBc/Hz at 1 MHz offset and integrated phase noise of 2.8° (simulated: 2.5°) measured at 57.6 GHz with output power of +1 dBm.

X-parameters provide a powerful and eminently practical solution for interoperable measurement, modeling, and simulation of nonlinear microwave and RF components. Using X-parameters to do large-signal measurements has been brought into the spotlight. This paper introduces a new X-parameter application: measuring large-signal behaviour of pulse-compression nonlinear transmission lines (NLTLs). A specially configured Nonlinear Vector Network Analyzer (NVNA) was used to measure the X-parameters in the frequency-domain, and then the measured data was transformed into a nonlinear time-domain waveform. The results show both rise-time and fall-time reduction (double-edge compression) as expected and indicate that this newly developed X-parameter method implemented with an NVNA could correctly predict NLTLs' pulse-compression performance.