Phased array

About: Phased array is a research topic. Over the lifetime, 19428 publications have been published within this topic receiving 229231 citations. The topic is also known as: Phased Array Radar, PAR.

Optoelectronic wide bandwidth photonic beamsteering phased array

Abstract: A transmit/receive circuit for each of the antenna elements of a radar phased array including an optical fiber true time delay circuit responsive to an electrical RF signal for providing an optical signal having a controlled time delay, an optical fiber for propagating the time delay controlled optical signal, an optical detector circuit responsive to the propagated time delay controlled optical signal for providing a time delay controlled electrical signal, transmit circuitry responsive to the time delay controlled electrical signal for providing to the associated antenna element a transmit signal based on the time delay controlled electrical signal, and receive circuitry responsive to the time delay controlled electrical signal and the signal received by the associated antenna element. A first RF switch selectively couples the time delay controlled electrical signal to the transmit circuit during transmit times, and to the receive circuit during receive times; and a second RF switch couples the associated antenna element to the transmit circuit during transmit times, and to the receive circuit during receive times. The receive circuit further includes analog-to-digital conversion circuitry whose sample timing is controlled so as to provide for time alignment of the received signal relative to the received signals of the other transmit/receive circuits of the phased array. Alternatively, such time alignment is provided pursuant to processing of the sampled receive signals from the transmit/receive circuits of the phased array.

Hybrid MIMO and Phased-Array Directional Modulation for Physical Layer Security in mmWave Wireless Communications

Abstract: Millimeter-wave (mmWave) wireless communication system allows a compact antenna array with a large number of colocated elements, which enables flexible array design and beampattern synthesis. However, security is also particularly important but challenging for the fifth-generation (5G) wireless communications, as the broadcasting nature allows any receivers to have a copy of the transmitted signals. In this paper, we propose a hybrid multiple-input multiple-output (MIMO) phased-array time-modulated directional modulation (DM) scheme for physical layer security in mmWave wireless communications. The hybrid MIMO phased-array enjoys the advantages of MIMO in spatial diversity without sacrificing the main advantage of phased-array in coherent directional gain. The essence is to divide the transmit array into multiple subarrays. Each subarray can be used to form a directional beam, while all subarrays are jointly combined to work as an MIMO for higher angular resolution capabilities. More importantly, a time-modulated DM scheme is applied for the phased-MIMO to achieve physical layer security for mmWave wireless communications, even without the knowledge of the eavesdropper’s position information. The feasibility of the proposed scheme is verified by numerical results.

Characterization of a Low-Frequency Radio Astronomy Prototype Array in Western Australia

Abstract: We report characterization results for an engineering prototype of a next-generation low-frequency radio astronomy array. This prototype, which we refer to as the Aperture Array Verification System 0.5 (AAVS0.5), is a sparse pseudorandom array of 16 log-periodic antennas designed for 70–450 MHz. It is colocated with the Murchison widefield array (MWA) at the Murchison radioastronomy observatory (MRO) near the Australian square kilometre array (SKA) core site. We characterize the AAVS0.5 using two methods: in situ radio interferometry with astronomical sources and an engineering approach based on detailed full-wave simulation. In situ measurement of the small prototype array is challenging due to the dominance of the Galactic noise and the relatively weaker calibration sources easily accessible in the southern sky. The MWA, with its 128 “tiles” and up to 3 km baselines, enabled in situ measurement via radio interferometry. We present array sensitivity and beam pattern characterization results and compare to detailed full-wave simulation. We discuss areas where differences between the two methods exist and offer possibilities for improvement. Our work demonstrates the value of the dual astronomy–simulation approach in upcoming SKA design work.

Planar Wide-Angle Scanning Phased Array With Pattern-Reconfigurable Windmill-Shaped Loop Elements

Abstract: A wide-angle scanning planar phased array with pattern-reconfigurable windmill-shaped loop elements has been designed. Each element has a four-port windmill-shaped structure over a high-impedance surface, and it can steer the main beam in four different space quadrants by exciting one port at a time. A 16-element planar (4 × 4) array is fabricated and measured to demonstrate the wide-angle scanning performance of the array. The results show that the fabricated array is able to scan its main beam up to 72° and supports a 3-dB scanning coverage up to 92° in each quadrant. In addition, input amplitudes and phases for the array are optimized with a hybrid particle swarm optimization algorithm to enhance the array scanning performance.

Intracavitary ultrasound phased arrays for noninvasive prostate surgery

Abstract: The feasibility of using intracavitary ultrasound phased arrays for thermal surgery of the prostate was investigated. A simulation study was performed which demonstrated the ability of phased arrays to generate necrosed tissue volumes over anatomically appropriate ranges (2-6 cm deep and >6 cm axially) and investigated the effects of varying frequency, sonication time, maximum temperature, and blood perfusion on the necrosed tissue volume. An advantage that phased arrays have over geometrically focused transducers is that they are able to electronically scan a single focus over a specified range very quickly. This study demonstrated that the necrosed tissue volume may be increased by more than a factor of 100 by using electronic scanning. Scan parameters that were investigated included foci spacing, scan width, perfusion, maximum temperature, and unequal weighting of the foci. An optimization was performed to select the foci weighting parameters such that a uniform thermal dose was achieved at the focal depth, providing a more uniformly heated target volume. Finally, the ability of linear ultrasound phased arrays to create necrosed tissue lesions was demonstrated experimentally in fresh beef liver using a single stationary focus and single focus scans generated by an aperiodic 0.83-MHz 57-element linear ultrasound phased array.