Design and Performance Analysis of Compact Printed Ridge Gap Waveguide Phase Shifters for Millimeter-Wave Systems.

This paper explores the usefulness of RF MEMS and reconfigurable antennas in the context of modern communication systems and other applications. Simulation studies on a fractal antennas with switches and phase shifters provide beam steering and beam scanning characteristics. A brief description of the design aspects of two MEMS based coplanar waveguide (CPW) phase shifters for microwave and millimeter wave antenna applications are also provided here. One phase shifter design consists of a unique bilateral interdigital structure on a silicon substrate deposited with a thin film of electrically tunable barium strontium titanate. The dielectric constant of the thin film, and hence the effective permittivity of the transmission line changes by the application of a bias voltage. The second device is a distributed microelectromechanical system (MEMS) phase shifter fabricated on a high resistivity silicon substrate using microstereolithography technique is presented here. The distributed MEMS phase shifter consists of a high-impedance CPW transmission line and several MEMS bridges of uniform height. By applying a voltage the height of these bridges can be adjusted. This results in a variation in the distributed capacitance of the segment of the transmission line, which manifests in the phase shift at the output terminal. The fabrication procedure described here shows significant promise for the use of microstereolithography techniques for RF MEMS devices.

A complementary split-ring resonator (CSRR)-loaded substrate-integrated waveguide (SIW) phase shifter and its application to a six-port junction is presented and demonstrated in this article. Different from the prior evanescent-mode analysis, this article concentrates on the TE10-mode analysis of CSRR-loaded SIW, and a slow-wave effect is observed. The CSRR offers a simple resolution to a slow-wave structure in SIW and can be verified by the CSRR equivalent-circuit model theory. Hence, an equal-length wideband 90° phase shifter (35%) can be realized by a proper design of the fast-slow-wave hybrid transmission line (TL). The phase velocity decrease caused by the slow-wave effect contributes to the length reduction of the phase shifter as well and makes it more compact. Furthermore, the widespread application of CSRR also helps generalize the slow-wave effect, and a more compact phase- shifter-based half-mode substrate-integrated waveguide (HMSIW) is obtained. To experimentally validate this concept, a dual-layer six-port- junction-based HMSIW is designed, simulated, and fabricated. The application of the slow-wave TL in a six-port design helps in the bandwidth enhancement and size reduction of the component, which makes it more applicable to demanding systems with complex requirements such as detecting and transceiver systems. The measured results are in accordance with the simulated data.

PurposeThis paper aims to design a radio frequency micro-electro-mechanical system (RF MEMS)-based phase shifter using chamfered coplanar waveguide (CPW) transmission line (t-line) with open-circuit interdigital metal–air–metal (ID MAM) capacitors.Design/methodology/approachThe proposed phase shifter achieves maximum differential phase shift with low loss at Ku band. The phase shifter is built with one switchable fixed-fixed beam (MEMS switch) on chamfered CPW t-line in series with two planar open-circuit ID MAM capacitors. An equivalent circuit model for the proposed phase shifter is derived, and its parameters are extracted using an electromagnetic (EM) solver.FindingsThe MEMS switch is actuated using an electrostatic method with the calculated residual stress of 44.26 MPa. The fabricated phase shifter exhibits low insertion loss, close to 0.14 dB at 17 GHz, with the maximum phase shift of 15.06°. The return loss is greater than 23 dB between 12 and 18 GHz.Originality/valueThis phase shifter presents a promising solution for low loss applications in the Ku band with a maximum phase shift. As the maximum phase shift of 15.06° is achieved for a unit cell with low insertion loss, the phase shifter is found to be feasible for modern electronically tunable phased arrays used for satellite communication and radar systems.

A novel T-shaped high-power waveguide phase shifter is investigated in this paper. The phase shifter consists of straight waveguides, four 90° H-bend waveguides, a stretching metal plate, and a metal spacer linked with the stretching metal plate. The entire structure for the phase shifter is symmetrical along both sides of the metal spacer. The phase-shifting principle for the phase shifter is to change the microwave transmission path by moving the stretching metal plate and then realize the linear phase adjustment. An optimal design approach of the phase shifter based on the boundary element method is described in detail. On this basis, a T-shaped waveguide phase shifter prototype with a center frequency of 9.3GHz is designed. Simulation results show that the phase shifters can achieve 0°-360° linear phase adjustment by altering the distance of the stretched metal plate to 24mm, and the efficiency of power transmission is more than 99.6%. In the meanwhile, experiments were conducted and the test results are in good agreement with simulation results. The return loss is more than 29 dB, and the insertion loss is less than 0.3 dB at 9.3GHz in the entire phase-shifting range.

With the improvement of mobile communication technologies and their broad applications, mobile communication will have more impact on our life. Such systems will support a variety of personal communication services with high-data rate and very low latency applications. To achieve such demands, many proposals associated with the development of 5G identify a set of requirements for which different technological directions are independently emerging. One direction is utilizing the millimeter-wave (mm-Wave) frequency bands where more spectrums are available. Millimeter-wave frequencies offer the advantage of physically smaller components that results in cost-effective RF transceivers and feasible large-scale integrated phased arrays. The smart RF transceivers of 5G along with the potential high-frequency innovative designs must satisfy the growing consumer and technology requirements. This implies utilizing the state-of-the-art guiding structures, especially printed ridge gap waveguide (PRGW), that have low loss and minimal dispersion compared with traditional PCB-based structures. The present chapter focuses on the necessary components for a beamforming antenna system which is implemented using PRGW technology. Millimeter wave antennas with different polarizations have been addressed. Power combining and dividing components have been also developed. These components have been used for integration in a complete beamforming antenna system working at an mm-Wave frequency band.

SummaryThis paper introduces the concept of spatial and media‐based modulated (SMBM) orthogonal frequency division multiplexing (OFDM) as a potential candidate for highly mobile next generation beyond 5G (B5G) wireless communications. The proposed SMBM‐OFDM technique utilizes not only the transmit antenna and channel state indices but also OFDM subcarriers to improve the system performance under high mobility. In addition, this study sheds light on challenging fast time‐varying channel estimation problem of MBM‐based systems by using the linear minimum mean square error (LMMSE) approach due to its optimality to investigate the achievable system performance with the aid of basis expansion modeling. The minimum lower bound on the channel estimation error (Bayesian Cramer–Rao bound) is derived theoretically and shown to be attainable by the considered LMMSE estimator. Moreover, symbol detection performance is provided for different modulation types and higher mobile velocities. Simulation results demonstrate that SMBM‐OFDM system under high mobility is able to provide around 12‐dB performance gains in terms of both channel estimation and symbol detection error compared to conventional spatial modulation (SM)‐OFDM systems without MBM. The presented framework is important due to addressing the high mobility support of SMBM‐OFDM systems for B5G wireless communications in terms of achievable channel estimation and data detection performance.

A novel phase shift unit for analogue beamforming is proposed. It is based on a defected microstrip structure (DMS). The DMS unit has a phase shift of 15° with insertion losses below 0.5 dB at 5.2 GHz. It is etched on a 50 Ohm conventional microstrip line and the length of which is only 0.07 wavelengths long. Due to the low insertion loss and compact size, the DMS units can be easily cascaded to realize a higher phase shift. As an example, a 1-bit phase shifter made by cascading 3 DMS units is designed. It has a phase shift of 45°±1.8° with the insertion losses still below 0.5 dB across the 5.2 GHz band (5.15 GHz to 5.35 GHz). The phase shifter design based on DMS is compact, low cost, and easy to be fabricated and integrated in microstrip systems. Therefore, it provides a low cost solution for analogue beamforming which usually employs a large number of phase shifters.

Previously, the design of our novel low-dispersion phase-shifter unit cell with two asynchronous MEMS switches was limited to 90°, so that four unit cells (90°, 90°, 90° and 45°) with a total of eight MEMS switches were required for a 3-bit phase shifter. This not only increased the size and loss of the phase shifter, but also decreased its yield and reliability. Recently, we hypothesized that by using two synchronized MEMS switches, the phase shift of a unit cell could be extended to 180° so that only three unit cells (180°, 90° and 45°) with a total of six MEMS switches would be required for a 3-bit phase shifter. This paper confirms the hypothesis with measured characteristics of a fabricated 180° phase-shifter unit cell. The measured characteristics compare well with both equivalent-circuit model prediction and three-dimensional finite-element electromagnetic simulation, provided the worse-than-expected loss from individual MEMS switches is taken into account. The results provide the proof of the design principle, so that with improved MEMS fabrication process such as thicker metallization, the switch loss can be reduced and low-dispersion phase shifters can be realized with compact size, low loss, low cost, and high reliability.

Fifth-generation millimeter-wave devices with multiple antennas require minimal mutual interference for better overall performance. This article presents a simple but novel technique to improve the isolation between closely packed slot antenna arrays. A printed ridge gap waveguide (PRGW) structure is used to realize a low loss millimeter-wave array's feeding mechanism. By optimally introducing a defective upper plate within the PRGW structure, the measured port isolation of the antenna elements is improved by 17 dB at 61.3 GHz. The antenna array is impedance matched to the feeding PRGW structure over a wide frequency range of 54–67 GHz. Moreover, the radiation patterns are consistent showing broadside radiation before and after introducing the defect in the PRGW structure. The fabricated prototype of the PRGW fed slot antenna array validated the predicted isolation and return-loss bandwidths of the proposed radiating system.

In this paper, a new class of wideband phase shifters on multimode resonator is proposed and developed. Compared with its conventional counterparts, these new phase shifters have a few advantageous features such as simple structure, intrinsic wideband characteristic, large phase-shift value, and easy adjustment in phase shift. The phase properties of multimode resonator are at first studied to derive the quantitative relationship between the phase slope and their respective resonant frequencies. On the one hand, a prescribed wideband phase shift can be achieved by adjusting the impedance ratio $R_{z}$ of the multimode resonator and the electrical length of the reference line. On the other hand, the wide operating band can be intrinsically obtained over a frequency range covered by multiple resonant frequencies in the multimode resonator. In this context, the transmission-line models of the proposed phase shifters are deduced and synthesized to design these phase shifters with a prescribed phase shift value and return loss within the operating band. Moreover, the synthesized model can be directly mapped into all the physical dimensions, thus allowing for a quick design process. Finally, two 180° wideband phase shifters are designed, fabricated, and tested to verify the proposed design method and predicted frequency responses.

A phased array antenna using ferroelectric coplanar waveguide (CPW) phase shifter active modules is presented based on a Ba0.6Sr0.4TiO3 (BST) thin film. The ferroelectric BST thin film was deposited on an MgO substrate by using pulsed laser deposition. The active module amplifies an RF signal with low noise and changes the phase of a received RF signal to control the main beam of the array antenna. It is composed of low noise amplifier (LNA), dc block, and ferroelectric CPW phase shifter. The prototype of 6×12 phased array patch antenna with the active modules using a ferroelectric phase shifter is proposed. The proposed array antenna continuously scanned its main beam in elevation plane to 32° from its broadside direction at 11.85 GHz by applying the continuous dc voltage to the ferroelectric phase shifter.

In this article, a 360° continuously tunable phase shifter (PS) is designed based on the proposed PS theory extended from the general tunable filter theory. The PS is composed of the reconfigurable multiple resonances and two external coupling networks (ECNs). The phase performances of the reconfigurable resonances are toggled among three states with different mode numbers to achieve consecutive 90° phase jumps. Dynamic and complex matching with positive imaginary parts is achieved between the reconfigurable resonances and ECNs, so as to obtain the smooth switch between phase-jumping states and the continuous fine phase shifting. In addition to the structural construction, a set of analytical formulas and guidelines for synthesizing the 270° PS is provided. Further, by loading two extra varactors on the microstrip line, the discrete phase jumps between the three states increase from 90° to 120° and the phase slope is more flexible, resulting in a complete 360° phase shift range (PSR) with low phase error. Finally, a tunable PS with reconfigurable three resonances is designed, fabricated, and measured. The proposed PS boasts a reduced total circuit size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.025\lambda _{g}^{2}$ </tex-math></inline-formula>, a fractional bandwidth (FBW) of 15%, and a continuous PSR of 360°.

It is very hard to realize a 6-bit resolution millimeter-wave phase shifter whether by passive structure or by active structure. A 52–57 GHz 6-bit phase shifter with hybrid of passive and active structures is proposed. The switched LC phase shifter is adopted for the passive structure because of its compact size, and the vector-sum phase shifter is chosen for the active structure in the 6-bit phase shifter. The proposed 6-bit phase shifter uses the passive structure to realize 5.625° and 11.25° phase shifts and uses the active structure to realize the $N \times 22.5^{\circ }$ phase shifts. Implemented in Taiwan Semiconductor Manufacturing Company 40-nm CMOS technology, the 6-bit phase shifter has a RMS error $\mu \text{m}\,\,\times 300\,\,\mu \text{m}$ and consumes about 13 mA from a 1.1-V supply.

This work presents a novel dual-polarized antenna array tailored for Internet of Things (IoT) applications, specifically designed to operate in the millimeter-wave (mm-wave) spectrum within the frequency range of 30–60 GHz. Leveraging printed ridge gap waveguide (PRGW) technology, the antenna ensures robust performance by eliminating parasitic radiation from the feed network, thus significantly enhancing the reliability and efficiency required by IoT communication systems, particularly for smart cities, autonomous vehicles, and high-speed sensor networks. The proposed antenna achieves superior radiation characteristics through a cross-shaped magneto-electric (ME) dipole backed by an artificial magnetic conductor (AMC) cavity and electromagnetic bandgap (EBG) structures. These features suppress surface waves, reduce edge diffraction, and minimize back-lobe emissions, enabling stable, high-quality IoT connectivity. The antenna demonstrates a wide impedance bandwidth of 24% centered at 30 GHz and exceptional isolation exceeding 40 dB, ensuring interference-free dual-polarized operation crucial for densely populated IoT environments. Fabrication and testing validate the design, consistently achieving a gain of approximately 13.88 dBi across the operational bandwidth. The antenna’s performance effectively addresses the critical requirements of emerging IoT systems, including ultra-high data throughput, reduced latency, and robust wireless connectivity, essential for real-time applications such as healthcare monitoring, vehicular communication, and smart infrastructure.

In this paper, a novel gap waveguide phase shifter utilizing tunable metal pins of the upper plate for phase shifting is proposed. This design is intended for precise phase control of high-frequency electromagnetic waves in the millimeter-wave band. The fundamental operating principle of the proposed phase shifter relies on altering the distribution of the metal pins to modify the propagation constant (β) along the transmission path, which results in stable and controllable phases in a wide bandwidth. To verify the scheme, a broadband 180-degree phase shifter is implemented and characterized, providing a complementary phase shift relative to the conventional transmission path. Promising simulation results across the 26–36 GHz frequency band validate its feasibility and superior performance. The designed phase shifter can be further used in specific millimeter-wave communication systems, multi-beam antenna arrays, and sophisticated RF front-ends.