Photonic Components for RF Filtering and Wide-Band Antenna Nulling

This paper presents the development, fabrication, and measurement of a novel beam-forming system consisting of 16 subarray antennas, each containing four aperture-coupled patch antennas, and the application of this system in smart wireless communication systems. The beam patterns of each of the subarray antennas can be switched toward one of nine zones over a half space by adjusting the specific phase delay angles among the four antenna elements. Furthermore, when all subarrays are pointed at the same zone, slightly continuous beam steering in around 1° increments can be achieved by dynamically altering the progressive phase delay angle among the subarrays. Phase angle calibration was implemented by coupling each transmitter output and down converter into the in-phase/quadrature baseband to calculate the correction factor to the weight. In addition, to validate the proposed concepts and the fabricated 2-D phased array antenna system, this study measured the far-field radiation patterns of the aperture-coupled patch array integrated with feeding networks and a phase-calibration system to carefully verify its spatially switched-beam and beam-steering characteristics at a center frequency of 2.4 GHz which can cover the industrial, scientific, and medical band and some long-term evolution applications. In addition, measured results were compared with calculated results, and agreement between them was observed.

Phased array antenna systems, which support high pulse rates and high transmit power, are well suited for radar and large-scale surveillance. Sensors and communication systems can function as the eyes and ears for ballistic missile defense applications, providing early warning of attack, target detection and identification, target tracking, and countermeasure decision. In such applications, active array radar systems that contain solid-state transmitter sources and low-noise preamplifiers for transmission and reception are preferred over the conventional radar antennas, because the phased array radar offers the advantages of power management and efficiency, reliability, signal reception, beam steering target detection. The current phased array radar designs are very large, complex and expensive and less efficient because of high RF losses in the phase control circuits used for beam scan. Several thousands of phase shifters and drivers may be required for a single system thus making the system very complex and expensive. This paper describes the phased array radar system based on high power T/R modules, wide-band radiating planar antenna elements and very low loss wide-band phase control circuits (requiring reduced power levels) for beam scan. The phase shifter design is based on micro-strip feed lines perturbed by the proximity of voltage controlled piezoelectric transducer (PET). Measured results have shown an added insertion loss of less than 1 dB for a phase shift of 450 degrees from 2 to 20 GHz. The new wideband phased array radar design provides significant reduction in size cost and weight. Compared to the conventional phased array systems, the cost saving is more than 15 to 1.

A novel antenna element has been proposed for maritime satellite communication Broadband Global Area Network (BGAN) phased array antenna system. The proposed antenna element is composed of a square radiating patch, two vertical trapezoidal coupling strips and a T-junction power splitter feeding network. A dual orthogonal side coupled feeding technique has been adopted to realize a circularly polarized square patch antenna. Design concepts and procedures are introduced, followed by simulations and discussions. Good antenna characteristics are achieved in the entire BGAN working band, having input impedance match characteristics of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> <;-15dB, antenna gain higher than 7dBi, and the axial ratio lower than 4dB.

This paper describes a scalable polarization reconfigurable phased array antenna system. The system was realized by using a beamformer and designing a more efficient and flexible power supply and control system, which could be exceedingly helpful to achieve a more flexible ground station design and satellite communication test. As a result, more flexible beam scanning and higher gain could be achieved. The design was simulated by CST Microwave Studio. The complexity of the system was significantly reduced by using the modular design of the active phase control structure.

Equal path length design for a phased array antenna system

Spherical phased-array antenna has hemispherical scan coverage for transmission of satellite imagery data at high bit rates to the ground station. Different conditions have been assigned based on their effects on the overall performance of the communication link. Reliability analysis consequently becomes an important requirement of any system onboard a satellite. Although the phased array and some connected algorithms have been presented in the literatures; however, there is no extensive systematic and theoretical performance evaluation framework formulated. In this work, the authors present new method that efficiently and effectively analyses the statistical performance of phased-array antenna systems using spherical harmonics expansion approach. Specifically, the errors caused by limited antenna element number, measurement noise of antenna, imprecision in phased-array antenna elements positioning, and spatial aliasing are systematically and theoretically benchmarked via simulations. Spatial sampling mechanisms for the positioning of array antenna elements on a sphere are presented and evaluated. This study proposed design guide and analysis for spherical phased-array antenna systems, and antenna arrays that do not employ spherical harmonics explicitly.

This article presents a monolithically integrated reflective-type phase shifter (RTPS) utilizing silicon-on-insulator (SOI) radio frequency (RF) microelectromechanical systems (MEMS). The analog phase shifter employs a hybrid coupler and two identical reflective loads optimized to achieve a large phase shift range. The hybrid coupler is designed using two CPW-based couplers connected in a folded tandem configuration to achieve a compact size design. Various reflective load topologies are studied for optimum phase shift range and phase linearity over the bandwidth of interest. Measurement results demonstrate a continuous 120° tunable range from 26 to 30 GHz. The mmWave phase shifter exhibits a low insertion loss of 5.35 dB ± 0.6 dB at 28 GHz. The fabricated phase shifter has an overall device footprint of 4.0 mm × 2.6 mm. All the components of the phase shifter module are co-fabricated in the 20 μm device layer of a SOI wafer, which provides the flexibility of monolithic integration with other RF modules in phased array antenna systems. Contactless thermally actuated MEMS varactors are used in the reflective loads which do not suffer from the conventional contact-based reliability issues.

The further investigation of the true time delay unit based on discrete fiber Bragg gratings

In this paper, a design of compact W-band planar Quasi-Yagi antenna is presented. The proposed antenna is fed by 50 Ohm coplanar waveguide with a broad-band balun in order to convert from unbalanced grounded-coplanar waveguide (G-CPW) mode into balanced coplanar strip line (CPS) mode. This antenna is realized on a high dielectric constant substrate, GaAs-relative dielectric permittivity of 12.9, that's compatible with active devices and circuits. Using the truncated ground plane as a reflector, the proposed antenna has a broad relative bandwidth of 18.07% with its return loss better than -10 dB, front to back ratio is 15.6 dB and 6.08 dBi of gain at 94 GHz. This antenna can be widely applied in wireless communication systems, active phased array antenna or millimeter-wave imaging systems.

Sub-beam concept is very useful for size reduction of multiple beam phased array antenna (PAA) systems that are applied for high-throughput communication satellites. In this paper, the synthesis procedure for a PAA with multiple sub-beams in two dimensions of the coverage domain is proposed and analyzed. In the design procedure, the interleaved sub-arraying technique has been applied to eliminate the grating lobes. The extremely short angular distance between adjacent sub-beams is challenging. An innovative beam forming network is proposed, which can generate multiple orthogonal sub-beams while keeping the required angular distance between sub-beams. To demonstrate the effectiveness of the design technique, an example considering the requirements derived from conceptual design of a high-throughput communication payload is presented. The array is optimized using the genetic algorithm while taking into account the technical requirements of the antenna. The gain patterns exhibit a 0.4° angular distance between adjacent sub-beams. In addition, the number of sub-arrays and element spacing guarantee the orthogonality of the sub-beams. The calculated carrier to interference ratio in the synthesized array shows that it has acceptable values in each spot. The aperture size reduction in the synthesized array compared to a conventional multiple beam array is more than 36.7%.

The National Weather Radar Testbed was established in Norman, Oklahoma, in 2002 to evaluate, in part, the feasibility of eventually replacing mechanically scanned parabolic antennas with electronically scanned phased-array antennas on weather surveillance radars. If a phased-array antenna system is to replace the current antenna, among the important decisions that must be made are the design (flat faces, cylinder, etc.) that will be needed to cover 360° in azimuth and the choice of an acceptable beamwidth. Investigating the flat-face option, four faces seem to be a reasonable choice for providing adequate coverage. To help with the beamwidth decision-making process, the influence of beamwidth on the resolution of various-sized simulated vortices is investigated. It is found that the half-power beamwidth across the antenna should be no more than 1.0° (equating to a broadside beamwidth of 0.75°) in order to provide National Weather Service forecasters with at least the same quality of data resolution that is currently available for making tornado and severe storm warnings.

The possibility of dynamically controlling the speed of light can be extremely useful in all the optical applications where a variable delay is needed, such as bit and frame synchronization and optical storage. To this aim, coupled resonator slow-wave structures (SWSs) represent a promising approach to slow down the propagation of optical signals with as large bandwidths as required by optical communication systems. We show that by suitably setting the rings' resonances, SWSs can act efficiently as tunable delay lines, with the overall time delay being continuously adjustable from zero to a maximum value, typically limited by the effects of loss and dispersion. Every ring of the structure can be used as an optical gate and optical pulses can also be trapped and released by the SWS, so as to realize an optical memory or buffer. A time delay of 300 ps and a slowing ratio of 7.5 over a 3.3 GHz bandwidth are experimentally demonstrated in SWSs realized in silicon oxynitride technology

Presents a case study of the design of a computationally intensive system to do adaptive nulling of interfering signals for a phased-array radar with many antenna elements. The goal of the design was to increase the computational horsepower available for this problem by about three orders of magnitude under the tight constraints of size, weight and power which are typical of an orbiting satellite. By combining the CORDIC rotation algorithm, systolic array concepts, Givens transformations, and restructurable VLSI, we built a system as small as a package of cigarettes, but capable of the equivalent of almost three billion operations per second. Our work was motivated by the severe limitations of size, weight and power which apply to computation aboard a spacecraft, although the same factors impose costs which are worth reducing in other circumstances. For an array of N antennas, the cost of the adaptive nulling computation grows as N/sup 3/, so simply using more resources when N is large is not practical. The architecture developed, called MUSE (matrix update systolic experiment) determines the nulling weights for N=64 antenna elements in a sidelobe cancelling configuration. After explaining the antenna nulling system, we discuss another DSP computation that might benefit from similar architecture, technology, or algorithms: the solution of Toeplitz linear equations.

This paper presents a novel phased-array antenna system with multifrequency, full-duplex operation, and wide-beam scanning. The system consists of a wideband power divider, a low-loss and low-cost multiline phase shifter controlled by dual piezoelectric transducers (PETS), a four-channel multiplexer, microwave monolithic integrated circuit (MMIC) amplifiers, and a stripline-fed Vivaldi antenna array. The multiline PET phase shifter has a low perturbation loss of less than 2 dB and a total loss of less than 4 dB up to 40 GHz, with a maximum phase shift of 650/spl deg/. Using dual-aligned PETS for bidirectional phase shifting results in wide scan angles of 38.6/spl deg/, 37.6/spl deg/, 43/spl deg/, and 40/spl deg/ for the four channels at 10, 12, 19, and 21 GHz, respectively. The four-channel diplexer demonstrates low insertion loss with high isolation between channels. The new multifrequency phased-array system provides wide-beam scanning and full-duplex capability using a simple, low-cost architecture. The system can be used for applications in mobile satellite communications.

We have proposed and designed a photonic true-time delay (TTD) steered phased-array antenna system that can work at high RF frequency with high angular resolution. Several elementary techniques have been studied and developed, including an optical realization of the Blass matrix based on our substrate-guided wave fanout structure, switching operation of wideband MSM and PIN photodetectors, and heterodyne RF signal generation. A design for the system demonstration that has the bandwidth from 18 to 26GHz is reported.