Fast Beamforming for Mobile Satellite Receiver Phased Arrays: Theory and Experiment

Abstract

The purpose of this paper is to present a robust and fast beamforming algorithm for the low-cost mobile phased array antennas. The proposed beamforming algorithm uses a sequentially perturbation gradient estimation method to update the control voltages of the phase shifters, with the objective of maximizing the received power by the array. This algorithm does not require either the knowledge of phase shifter characteristics or signal Direction-of-Arrival. Moreover, in this paper, the algorithm parameters are derived for the stationary and mobile platform configurations. For the stationary array, it is shown how the proper selection of the beamforming parameters limits the noise effects and increases the array output power. For the mobile array, a condition for the fast convergence is derived and the advantage of using nonuniform step size to update the control voltages is illustrated. When phase shifters suffer from the imbalanced insertion loss the proposed beamforming technique perturbs the phase-conjugate condition to increase the total received power. This algorithm has been implemented with the low-cost microwave components and applied to a Ku-band phased array antenna with 34 sub-arrays. The experimental results verify the broadband performance, and the fast convergence of the algorithm for different platform maneuvers.Index Terms-Adaptive array, beamforming, mobile phased array antenna, satellite communications, smart antenna.

Beamforming algorithm based on SPSA for mobile satellite receiver

“…Besides the SPSA beamforming algorithm's merit, the proposed method can track the target satellite quickly, accurately and steadily in the single-channel receiver. Computer simulations verify that the proposed algorithm is indeed robust and effective.Introduction: Recently, there has been a greatly increased user demand for satellite communication in vehicular stations such as cars, buses, trains and ships beyond a fixed station [1][2][3][4]. In the satellite communication on-the-move (SOTM) system at Ku-band, due to the small intervals of the adjacent geostationary satellites, the radiation pattern of the vehicle-mounted antenna is required to be narrowed and strictly aligned to the desired satellite, to prevent interference from other adjacent satellites and not to miss the target satellite during motion [3].…”

“…In the satellite communication on-the-move (SOTM) system at Ku-band, due to the small intervals of the adjacent geostationary satellites, the radiation pattern of the vehicle-mounted antenna is required to be narrowed and strictly aligned to the desired satellite, to prevent interference from other adjacent satellites and not to miss the target satellite during motion [3]. This Letter is focused on the tracking method to carry out the accurate alignment for SOTM.…”

“…In [3], a kind of hybrid tracking scheme composed of a mechanical stabilisation loop and an electronic beamforming loop for the vehiclemounted phased-array antenna is developed. The mechanical stabilisation loop orients the beam approximately to the target and then an electronic beamforming algorithm for the single-channel receiver is utilised to realise the accurate beam direction.…”

“…The mechanical stabilisation loop orients the beam approximately to the target and then an electronic beamforming algorithm for the single-channel receiver is utilised to realise the accurate beam direction. In [3], a DOA estimation method which perturbs all phase shifters sequentially to estimate the gradient of the received signal power is proposed, which is similar to the finite difference stochastic approximation (FDSA) algorithm in [4]. Nonetheless, the sequential perturbation is time-consuming and the algorithm may converge slowly with the increasing number of phase shifters according to [4].…”

“…1, which is similar to the antenna structure in [3]. The element spacing d ¼ 0.5l where l is the wavelength; the proposed algorithm parameters a ¼ 0.…”