1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications

Millimeter-Wave Concurrent Dual-Band BiCMOS RFIC Front-End Module for Communication and Sensing Systems

This dissertation presents new circuit architectures and techniques for improving several key performances of BiCMOS RFIC building blocks that are used in wireless communication and sensing systems operating at millimeter-wave frequencies. The developed circuits and front-end module can be employed in concurrent dual-band transceivers for communication and sensing systems such as phased array and RFID systems. New 0.18-μm CMOS dual-bandpass filtering single-pole double-throw (SPDT) and transmit/receive (T/R) switches have been developed, and they operate in two different frequency bands centered at around 40 and 60 GHz (Design 1) and 24 and 60 GHz (Designs 2, 3 and 4). Design 1 is a concurrent dual-bandpass filtering T/R switch consisting of three SPDT switches based on a 3rd order band-pass filter with shunt nMOS transistors as the switching function. Design 2 is a 24/60-GHz concurrent dual-bandpass T/R switch consisting of dual-band λ/4 LC networks and resonators with shunt nMOS transistors as the switching function. Design 3 is a dual-band SPDT and T/R switches, which are capable of band-pass filtering as well as separate and concurrent switching operations in single/dual-band and transmission/reception. These components can act as diplexers with switching functions. Design 4 is a wideband concurrent dual-band SPDT switch with integrated dual-bandpass filtering, which is configured to make it approximately equivalent to a dual-band resonator in the on-state operation. A fully integrated 24/60-GHz concurrent dual-band LNA utilizing a dual-band LC circuit has been proposed. The LNA is based on a two-stage cascode topology with inductive degeneration. The dual-band LC circuit has the quarter-wavelength characteristic at two different frequencies, and it shows the dual pass-band and single stop-band characteristics when it is connected to the ground in shunt. Due to the cancellation of the stop-band signal and low-pass response by the LC circuit connected to the cascode nodes of the 1st and 2nd stages in the LNA, the LNA presents high stop-band rejection and good gain balance at 24 and 60 GHz. A concurrent dual-band front-end module (FEM) consisting of a 24/60-GHz dual-band antenna, a five-port T/R switch, two LNAs and one PA has been proposed. The FEM can be employed in systems with dual-polarization, for instance, phased array and RFID reader systems

Simultaneous Transmit and Receive (Star) Antennas for Geo-Satellites and Shared-Antenna Platforms

This thesis presents the analysis, design, and experimental characterization of antenna systems considered for shipborne, airborne, and space platforms. These antennas are innovated to enable Simultaneous Transmit and Receive (STAR) at same time and polarization, either at the same, or duplex frequencies. In airborne and shipborne platforms, developed antenna architectures may enhance the capabilities of modern electronic warfare systems by enabling concurrent electronic attack and electronic support operations. In space, and more precisely at geostationary orbit, designed antennas aim to decrease the complexity of conventional phased array systems, thereby increasing their capabilities and attractiveness. All antennas researched are first designed as a standalone radiator, then as entity of a platform having multiple different antennas.An ultrawideband, lossless cavity-backed Vivaldi antenna array for flush-mounting applications is first investigated. Eigen-mode analysis is used to analyze antenna-cavity interaction and to show that the entire structure may resonate within the band of interest resulting in a significant degradation of antenna performance. A simple approach based on connecting the array’s edge elements in E-plane to the cavity walls is proposed to eliminate the deleterious impact of these cavity resonances. The designed antenna is a 3 × 4 array with 3 elements in E-plane and 4 elements in H-plane, fabricated using stacked all-metal printed circuit board technique. Scan performance of the proposed cavity-backed antenna is investigated in two principal planes and is shown to have similar performance compared to its free-standing counterpart. A simplified version of this single-polarized antenna, when used for broadside only applications is developed. This antenna, excited with a single coaxial feed is shown to have a smaller aperture than the 3 × 4 array. Isolations between two of these antennas when mounted on a compact shared-antenna platform are investigated through computation and experiments.To extend the capability of systems relying on these designed antennas, frequency reuse is enabled through dual-polarized functionality. A dual-polarized, flush mounted, Vivaldi antenna, directly integrated with an all-metal cavity is introduced as an alternative to coax-fed quad-ridge horns. An approach based on shaping the side walls of the cavity is used to eliminate the occurrence of resonances. The proposed dual-polarized resonant-free antenna has two orthogonal 2 × 1 arrays with two elements in the E-plane, one element in the H-plane. It is fed using two 2-way power dividers that can be easily designed to maintain low amplitude and phase imbalances. The antenna is fabricated as a single piece and experimentally shows a monotonic gain increase with low cross-polarization over 4:1 bandwidth.Phased array antennas operating at geostationary orbit are required to scan within Earth’s field of view, without any grating lobe appearance. For dual-polarized applications, this requirement has limited the widespread and attractiveness of these systems at frequencies such as X-band. The narrow 150 MHz guard range between transmit and receive bands, leads to impractical diplexers in conventional dual-polarized systems. This research introduces a dual-polarized subarray architecture for X-band phased array systems which enables high isolation between closely separated TX and RX bands. The proposed approach either eliminates the need for diplexers, or significantly decreases their required complexity

Radar Exploration of Venus: Goldstone Observatory Report Oct. - Dec. 1962

Radar exploration of Venus - radiometer, spectral and polarization studies, automatic frequency tracking, frequency-time mapping, and amplitude modulated rangin

Antennas and beam-steering arrays for polarization diversity and full-duplex applications

This thesis presents new designs for polarization diverse dielectric resonator antennas (DRAs) as well as antennas that can offer efficient full-duplex (FD) functionality. Basically, this research effort has been completed to meet the demands of modern tracking systems as well as in-band full-duplex communication systems. For these applications antenna polarization control, compatibility, co-location, and isolation are the important parameters to support these high-performance systems. The first part of the thesis covers the challenges of modern radio frequency (RF) environments where the proposed polarization reconfigurable antennas are introduced. At first, a multi-port DRA is outlined as a possible candidate for the global positioning system (GPS) and the Global Navigation Satellite System (GNSS). To further advance this original design, and in an effort to reduce the size whilst maintaining polarization control, an integrated circuit was also proposed and tested. Advancing from the research work of phase polarization control using DRAs, the second part of the thesis studies other new antennas which are suitable for FD communications. Those antennas offer high isolation which makes the signal recoverable for those FD systems. To advance the state-of-the-art, an H-shaped slot antenna arrangement with parasitic patches and dual-differential feeding was proposed. The antenna architecture was investigated with both external and integrated feed systems and both prototypes offer high isolation levels. The single-element was further integrated into a 1×4 antenna array which was shown to offer similar isolation levels and with the capability to beam steer. Further research included high isolation antennas for operation in the 5G mm-wave band. In particular, a new FD pattern reconfigurable antenna was proposed which can be used in dual-polarized radars and other FD systems. Depending on the input phase excitation, the beam pattern control can be established with sum or difference patterns or both. Also, the antenna concept was further extended into a novel FD antenna array. This array has a similar common and/or differential feeding which can provide sum or difference patterns in the far-field. Also, an external Butler matrix was used to investigate the beam-steering capabilities of the array. These antenna systems also have applications for dual-polarized radars, retro-directive arrays, and other beam-tracking scenarios which require high inter-port isolation.James Watt Scholarshi

Integrated Filters and Couplers for Next Generation Wireless Tranceivers

The main focus of this thesis is to investigate the critical nonlinear distortion issues affecting RF/Microwave components such as power amplifiers (PA) and develop new and improved solutions that will improve efficiency and linearity of next generation RF/Microwave mobile wireless communication systems. This research involves evaluating the nonlinear distortions in PA for different analog and digital signals which have been a major concern. The second harmonic injection technique is explored and used to effectively suppress nonlinear distortions. This method consists of simultaneously feeding back the second harmonics at the output of the power amplifier (PA) into the input of the PA. Simulated and measured results show improved linearity results. However, for increasing frequency bandwidth, the suppression abilities reduced which is a limitation for 4G LTE and 5G networks that require larger bandwidth (above 5 MHz). This thesis explores creative ways to deal with this major drawback. The injection technique was modified with the aid of a well-designed band-stop filter. The compact narrowband notch filter designed was able to suppress nonlinear distortions very effectively when used before the PA. The notch filter is also integrated in the injection technique for LTE carrier aggregation (CA) with multiple carriers and significant improvement in nonlinear distortion performance was observed. This thesis also considers maximizing efficiency alongside with improved linearity performance. To improve on the efficiency performance of the PA, the balanced PA configuration was investigated. However, another major challenge was that the couplers used in this configuration are very large in size at the desired operating frequency. In this thesis, this problem was solved by designing a compact branch line coupler. The novel coupler was simulated, fabricated and measured with performance comparable to its conventional equivalent and the coupler achieved substantial size reduction over others. The coupler is implemented in the balanced PA configuration giving improved input and output matching abilities. The proposed balanced PA is also implemented in 4G LTE and 5G wireless transmitters. This thesis provides simulation and measured results for all balanced PA cases with substantial efficiency and linearity improvements observed even for higher bandwidths (above 5 MHz). Additionally, the coupler is successfully integrated with rectifiers for improved energy harvesting performance and gave improved RF-dc conversion efficienc

Fully-Integrated Magnetic-Free Nonreciprocal Components by Breaking Lorentz Reciprocity: from Physics to Applications

Reciprocity is a fundamental physical precept that governs wave propagation in a wide variety of physical domains. The various reciprocity theorems state that the response of a system remains unchanged if the excitation source and the measuring point are interchanged within a medium, and are closely related to the concept of time reversal symmetry in physics. Lorentz reciprocity is a fundamental characteristic of linear, time-invariant electronic and photonic structures with symmetric permittivity and permeability tensors. However, breaking reciprocity enables the realization of nonreciprocal components, such as isolators and circulators, which are critical to electronic, optical and acoustic systems, as well as new functionalities and devices based on novel wave propagation modes. Nonreciprocal components have traditionally relied on magnetic materials such as ferrites that lose reciprocity under the application of an external magnetic field through the Faraday Effect. The need for a magnetic bias limits the applicability of such approaches in small-form-factor Complementary Metal–Oxide–Semiconductor (CMOS)-compatible integrated devices. One of the main features of CMOS technology is the availability of high-speed transistor switches which can be turned ON and OFF, modulating the conductance of the medium. In this dissertation, a novel approach to break Lorentz reciprocity is presented based on staggered commutation in Linear Periodically-Time-Varying (LPTV) circuits. We have demonstrated the world’s first CMOS passive magnetic-free nonreciprocal circulator through spatio-temporal conductivity modulation. Since conductivity in semiconductors can be modulated over a wide range (CMOS transistor ON/OFF conductance ratio at Radio Frequency (RF)/millimeter-wave frequencies is as high as 103-105), commutated LPTV networks break reciprocity within a deeply sub-wavelength form-factor with low loss and high linearity. The resulting nonreciprocal components find application in antenna interfaces of wireless communication systems, connecting the Transmitter (TX) and the Receiver (RX) to a shared antenna. This is particularly important for full-duplex wireless, where the TX and the RX operate simultaneously at the same frequency band and need to be highly isolated in order to maintain receiver sensitivity. Multiple fully-integrated full-duplex receivers are demonstrated in this dissertation that best show the synergy between the physical concept and application-based implementations by using circuit techniques to benefit the system-level performance, such as TX-side linearity enhancement and co-design and co-optimization of the antenna interface and the RX and utilization of the multi-phase structure of our antenna interfaces for analog beamforming in multi-antenna systems. Finally, this dissertation discusses some of the fundamental limits of space-time modulated nonreciprocal structures, as well as new directions to build nonreciprocal components which can ideally be infinitesimal in size. A novel family of inductor-less nonreciprocal components including circulators and isolators have been demonstrated that achieve a wide tuning range in an infinitesimal form-factor. This family of devices combine reciprocal and nonreciprocal modes of operation, through the transfer properties of fundamental and harmonics of the system and enable a wide variety of functionalities