OFDM-based wideband phased array radar architecture

This paper demonstrates the use of hybrid beam steering components for wideband electronic scanning. A unidirectional multifunction monolithic microwave integrated circuit (MMIC) core chip is combined with three numbers of single pole double throw (SPDT) switches to realize bi-directional TTD units for transmit and receive operation. The realized bi-directional TTD unit is characterized for its functionality at the four-element subarray for true-time delay beam steering. The 6-bit digitally controlled phase shifters and a 6-bit true-time delay (TTD) units are used in a hybrid configuration to realize an X-band wideband 16-element linear array. The element level phase delay (limited to a maximum 360º) and subarray level time delay in steps of 3.125 ps (maximum delay of 197ps) is applied for the array calibration and beam steering. The radiation pattern is measured at the center operating frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> , and the beam is steered at f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> + 0.5 GHz to validate squint-free beam scanning. The proposed configuration with a two-stage hybrid phase/time delay demonstrates the wideband beam steering and eliminates the beam squint for wide instantaneous signal bandwidth for high-resolution imaging active phased array radars.

To perform wide-angle scanning while maintaining a planar low profile, we propose a new kind of millimeter-wave (mm-Wave) planar phased array antenna using inclined beam elements to imitate a curved surface conformal (CSC) array, called a pseudo-CSC (PCSC) phased array antenna. We present the concept of our PCSC phased array and then design an elongated planar aperture antenna (EPAA) element, achieving stable high broadside gain and wide beam on the scanning plane within a wide bandwidth. Then, by introducing asymmetries to the EPAA element, the beam inclination of the EPAA element can be adjusted. Accordingly, we use EPAA elements with different beam inclinations to form a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times4$ </tex-math></inline-formula> -element 1-D wide-angle scanning PCSC phased array antenna. We design, fabricate, and measure a prototype of our proposal, with measured results showing that the proposed design has a 3 dB gain variation across a scanning range of more than ±62° (and as high as ±68°) within the 5G mm-Wave band (24.25–29.5 GHz), which is about ±10° better than its traditional counterpart.

A 1×4 phased array antenna in package is presented at 60 GHz frequency band. End-fire elements are double side dipoles which provide a near omni-directional beam in H-plane. In E-plane, the phased array facilitates ±45° beam steering which improves the spatial coverage. The achieved end-fire gain is 9.1 dBi and both impedance and gain bandwidths cover all WiGig channels. The wide bandwidth, high coverage, and high gain of the phased array make it a desirable candidate for multi-gigabit wireless communication.

Beam-steering antennas are the ideal solution for a variety of system applications, it is most commonly achieved through using phased arrays, where phase shifters are used to control the relative of the main-beam. In this paper, a low-cost directive beam-steering phased array (DBS-PA) antenna using switched line phase shifters is demonstrated. The proposed DBS-PA antenna has four micro-strip patch antennas, three power dividers and four phase shifters printed on the same Rogers RT-Durroid substrate with a dielectric constant of 2.2 with dimensions of 8 × 3.5 cm. The phased array antenna has a directivity of 15 dBi and the main beam direction can be switched between the angles of ±30 degrees with a 3dB beam-width of 25 degrees. All design and simulations have been carried out using Agilent AdS and Ansoft HFSS software tools. The frequency considered for the operation is 10 GHz.

Simulation and experimental measurement of digital multi-beamforming phased antenna array in the frequency range C

This paper presents a new approach to reduce mutual coupling effects in large phased array antennas currently under development for use in low frequency radio astronomy. A receive mode definition of coupling between two antennas is shown to serve as a good indicator of the severity of mutual coupling interactions in a phased array. Thus, an efficient way to reduce mutual coupling in the array is to design antenna elements for low receive coupling. It is demonstrated that wire inverted-V dipole antennas can be designed with significantly reduced receive coupling over a wide range of frequencies and wave directions by proper selection of the antenna element geometry and feed impedance. Corresponding improvements in the performance of a large aperiodic phased array are achieved by using the reduced coupling wire inverted-V dipole design. Both antenna coupling and phased array analyses are performed using numerical simulation. Full-scale, in situ receive coupling measurements are performed to validate the simulation results.

This paper presents a fully adaptive digital pre-distortion using a multi-dimensional nonlinear model that is implemented in hardware without the use of any digital multipliers and operates at very wide instantaneous bandwidths (>1 GHz instantaneous bandwidth). This multi-dimensional compensator effectively mitigates linear and nonlinear distortion in RF power amplifiers by modeling the state of the device by tracking multiple functions of the input, which can include: the present input signal value; delayed values of the input (for memory effects); derivatives of the input (including higher order derivatives); integration of the input (including higher order integrals); signal statistics (e.g., mean, variance); current power level (RMS or peak); and polynomial functions of the input. The processing is implemented with memory instead of digital multipliers for low-power applications. It is calibrated using simple arithmetic operations that can be completed with low processing requirements and very quickly to track parameters that rapidly change over time, temperature, and power level such as in frequency-hopping systems. The approach has been demonstrated in realtime hardware providing 15–30 dB improvement in distortion.

The need for small antennas with wide instantaneous bandwidth is well established in mobile Cognitive radio nodes or transceivers. The fundamental limit of small antennas is a problem which passive matching cannot solve. However, non-Foster matching provides a means of getting around this problem. In this paper, we show a negative impedance converter that provides a negative capacitor up to 1.5GHz and we show how it can be used to match a small chassis antenna. This improves the instantaneous bandwidth of the antenna beyond what is achievable with passive matching.

Our recently reported magnetic field synthesis procedure was utilized to construct a series of broad band, low loss linearly dispersive magnetoelastic microwave delay lines. High performance device opertion was obtained over the entire tested frequency range of .5 to 4. GHz. The delay lines consisted of a fractional centimeter long (100) YIG rod, immersed in a nonuniform d.c. magnetic field, generated by soft iron pole pieces whose shape was uniquely synthesized to provide the desired delay characteristics. Typical operating parameters at a fixed d.c. magnetic field bias are: second echo‐free instantaneous bandwidth 1000 MHz; frequency dispersion.5−1.5μsec/GHz; two way untuned insertion loss 32±2.5 db and input/output isolation 15–20 db.

The choice of element for constructing a phased antenna array (PAA) providing a relative frequency bandwidth up to 9% for the transmission or reception of wireless communication system information was carried out. There are three methods to suppress of side lobes and diffraction of PAA in the radiation far field. Superposition of excitation signals of a flat PAA for simultaneous emission of several independent beams in a radiation far field was used. Сalculation and optimization of progressive distribution of phase shifts in the excitation signal group in the horizontal and vertical directions in the plane of PAA for radiation (reception) of independent beams in spherical coordinates (azimuth and elevation) in space was performed. An experimental sample of a phased antenna array was developed using microstrip technology, which forms several beams in a radiation far field. An experimental measurement of the voltage standing wave ratio and relative frequency bandwidth of the sample developed by phased array microstrip and printing technology was carried out.

Large membrane “Furoshiki Satellite” applied to phased array antenna and its sounding rocket experiment

A space-fed X-band phased array antenna (PAA) is presented. The space-fed PAA uses physically autonomous individually addressable unit cells as the building blocks of an arbitrarily large array antenna. The X-band PAA unit cell consists of both a feed facing printed antenna element and a target facing printed antenna element. These elements are related by an RF phase shifter placed in the RF signal path between them which introduces relative phase delay and enables analog beam forming. Unit cell autonomy is realized by wirelessly transferring power and command signals required to operate a microcontroller (MCU) and the RF phase shifter at each unit cell. Each unit cell includes RF to DC conversion circuitry as well as an MCU designed to interpret a common control signal and command unit cell phase delay. The wireless phased array unit cell can be replicated in configurations of size and shape that are independent of RF, power, and array module control distribution networks. To demonstrate feasibility a four-element wireless PAA is constructed and antenna patterns for various control states are shown.

Summary form only given, as follows. A millimeter wave phased antenna array (PAA) has been proposed for use in plasma imaging reflectometric diagnostics and is currently under design and fabrication. To account for the rapid changes of the cutoff layer with plasma density variation, a true time delay (TTD) controlled phased antenna array (PAA) is being developed as an artificial lens with controllable focal length for launching the illumination beam of the microwave imaging reflectometry (MIR) system. The beam shaping concept illustrates that programming the PAA generates concave (focusing/beam narrow) or convex (defocusing/beam broaden) wavefronts by properly arranging the time delay (or phase shift), therefore, the PAA functions like a real optical lens. The focal properties can be easily changed by different time delay arrangement at high speed so that real time control is possible on time scales significantly faster than plasma changes. The operation frequencies for the first implementation of beam shaping antenna array are set as 45-55 GHz based on the NSTX MIR system requirements. The time delay unit utilizes a piezoelectric translator (PET)-driven perturber to vary the propagation velocity along low loss microstrip lines. Tapered slot antenna will be used in the system as array element. To overcome the system loss and scattering loss from the plasma, the beam shaping array system is designed with an output power of at least 50 mW, and with a desired variable 3-dB beam width extending from 15/spl deg/ to 25/spl deg/.

The need for larger arrays of millimeter and submillimeter wavelength detectors for Cosmic Microwave Background (CMB) experiments is driving a demand for focal planes which can field large numbers of detectors with both high sensitivity and wide bandwidth. Current CMB experiments have $\sim 10^{4}$ detectors, with next generation focal planes requiring $\sim 10^{5}$ or more. One challenge of expanding the array size is coupling the detectors to instrument optics with a method that is broadband, low loss, and scalable. Current state of the art methods of coupling incident radiation include phased array antenna-coupled detectors, corrugated feedhorn arrays, and hemispherical lenslet array-coupled planar antennas. Phased array antennas are fabricated using planar lithography techniques and therefore easily scalable, but are typically narrow band ($\sim 30\%$). Silicon platelet feedhorns are scalable and low loss, but typically achieve only an octave of bandwidth. Lenslets have been produced using silicon hemispheres stacked on silicon plates to approximate an elliptical lens. Low loss and broadband behavior is accomplished by individually molding anti-reflection layers made of materials with appropriate refractive indices and individually glued to arrays; however this approach does not easily scale to larger arrays. We are developing planar lenslet arrays using metamaterials fabricated with standard microlithograpy techniques on silicon wafers. Instead of using difficult to manufacture curved optical surfaces, the lenslets consist of stacks of silicon wafers which are each patterned with an array of sub-wavelength features to produce optical features which form a well defined beam at measurement wavelengths. These arrays are being developed using two approaches: GRadient INdex (GRIN) lenslets which are fabricated by etching holes on a sub-wavelength grid to produce a spatially varying effective index of refraction, and metal-mesh lenslets which are produced by depositing spatially varying metallic features which act as a series of Transmission Line (TL) lumped element features to control phase delay across the wafer. GRIN lenslets are fabricated by etching sub-wavelength holes on a periodic, sub-wavelength grid using standard microlithography techniques. The wafers can be stacked, allowing the spatial index to be altered along all dimensions, which allows for arbitrary anti-reflective coatings to be integrated in the lenslet design. Simulations in finite element modeling (FEM) software have been used to both evaluate the effective index of an individual element and simulate full lenslet structures. Dielectrically embedded mesh-lenses are based on existing mesh-filter technology. Differently from the mesh-filters, the grids are inhomogeneous and their geometry is designed in such a way to impart variable phase shifts across the surface. The local phase shifts reproduce those that would be introduced by a classical dielectric lens. In this work we are developing mesh-lenslets on silicon substrates. The metal grids are supported by silicon nitride (SiN) membranes and kept at specific distances in an air-gap configuration. Finite element analysis is used to quantify and optimize the performance of these devices. We report on progress in both lenslet design approaches. In each case we have developed a set of design equations which guide the design of the full lenslet structure. These structures are simulated using finite element modeling simulations. We report on measurements and efficacy of the design and simulation process and agreement with laboratory measurements of prototype lenslet arrays.

Antenna integration and miniaturisation techniques are crucial for maintaining the desired electrical and physical properties of antennas, while meeting the growing demands for reliable link performance and compact device designs for emerging wireless communications. This Special Issue presents recent advances in the theory, analysis, design, and application of antenna integration and miniaturisation. These techniques are enabling diverse novel designs and applications, propelling advancements in integrated circuits, and next-generation wireless communication systems rapidly. The papers in this Special Issue present the state-of-the-art contributions that address the challenges of design, fabrication, and performance enhancement for miniaturised and integrated antennas. This Special Issue includes six high-quality papers, each presenting unique innovations in the field of antenna integration and miniaturisation. Thus, the overall submissions are of high quality, which marks the success of this Special Issue. Ye et al. present a high-gain circularly polarised magneto-electric dipole antenna array with metallic radiating structures for millimetre-wave applications. This paper proposes a novel design of a magneto-electric dipole antenna array for millimetre-wave applications. The novel use of metallic radiating structures helps achieve high gain and circular polarisation, making the proposed design ideal for millimetre-wave communication systems. Truong et al. introduce a method for designing an electrically small printed square loop antenna for closely spaced transmitter-receiver (Tx/Rx) systems. This paper demonstrates a compact antenna design, featuring a simple series combination of two lumped inductors and two interdigitated capacitors, providing inherent impedance matching without the need of an additional matching network. This proposed compact design method is highly relevant for modern and emerging wireless communication systems where space is often limited and confined. Mao et al. propose a null-depth coordinated synthesis design approach for azimuthal null frequency scanning antennas (ANFSAs). A synthesis chart gauged by different null-depths is developed to determine the respective exciting amplitude and phase conditions for the principal and auxiliary radiators. This method provides a promising solution for achieving efficient frequency scanning with an in-band null-depth as high as −30 dB. Choi et al. offer miniaturised ultra-wideband circular polarised Koch fractal crossed dipole array. The design incorporates a Koch fractal structure and an extended metallic sidewall to stabilise the axial ratio (AR) across a wide bandwidth. This innovative approach has significant potential for phased array applications in ultra-wideband (UWB) circularly polarised environments. Xiong et al. present a novel millimetre-wave two-dimensional (2-D) wide-angle scanning phased array antenna based on decoupling surface. This paper proposes a millimetre-wave phased array antenna capable of wide-angle scanning based on decoupling surface (DS). This proposed design overcomes the challenges of mutual coupling between the antenna elements, enhancing the overall scanning range and efficiency of the antenna array. The proposed antenna exhibits promising capabilities for wide-angle beam-scanning implementation in scenarios such as automotive radar and satellite communication. Liang et al. contribute a high-efficiency wideband co-polarised metalens antenna. The paper demonstrates a multilayer metasurface structure comprising five layers of metal patches and four dielectric layers, forming a Fabry–Pérot resonator. This approach offers a compact solution for integrating metasurface technology with traditional antenna design, pushing the limits of antenna miniaturisation while maintaining its high efficiency. We would like to extend our sincere gratitude to the authors for their outstanding contributions, and to the reviewers for their insightful feedback, which significantly enhanced the quality of this Special Issue. Special thanks are also due to the editorial team at IET Microwaves, Antennas & Propagation for their invaluable support in managing this publication. Data available on request from the authors.