A novel measurement method is proposed in order to measure the active electric fields of the individual antenna elements in a phased array antenna. Fast and accurate measurements can be realized by the proposed method because the electric fields of multiple elements can be obtained simultaneously and no phase measurements are required. Hence, it can be easily applied to the on-board diagnostics and re-calibration in the operating phased array antenna systems. In the first step with this method, the phases of multiple antenna elements are successively shifted with the specified phase intervals while the array power variations are measured. Next, the measured power variation is expanded into a Fourier series and the terms are rearranged to put them into the form of the rotating element electric field vector (REV) method. Finally, the REV solution is used to identify the electric fields of the individual elements. Additionally, a theoretical study is carried out on the accuracy of the proposed measurement method. Simple, closed-form equations have been successfully derived for the measurement errors and the calibration accuracy is theoretically estimated. The proposed measurement method is validated with experimental results and the measurement accuracy is compared with the theoretical prediction.

Fast Measurement Technique for Phased Array Calibration

In satellite phased-array antennas, mechanical distortions, which may be due to vibrations caused when launching the satellite into the orbit or thermal variations in the orbit, result in significant degradation of electrical performance. In this paper, two on-board calibration methods are proposed for such mechanical distortions: One compensates for the element phase differences resulting from mechanical distortions, and the other is used to set the best-fit phase distribution obtained from the measured phases. The latter method is effective even at a low signal-to-noise ratio (SNR). The proposed methods have been validated by experiments, through which the theoretically predicted calibration accuracy of the methods has been successfully reproduced.

On-Board Calibration Methods for Mechanical Distortions of Satellite Phased Array Antennas

A novel amplitude-only measurement method is proposed for phased array calibrations. The proposed method can determine a complex element field at every phase shift of a digital phase shifter in phased arrays. The method can be realized using higher order Fourier coefficients of one array-power response measured with the conventional rotating element electric field vector (REV) method. Simulations and experiments were carried out, including transmission errors from the phase shifters, which validated the proposed method. More accurate calibration and beam forming can be achieved by using the precise element fields at all phase shifts determined by the proposed method.

A Novel Amplitude-Only Measurement Method to Determine Element Fields in Phased Arrays

This study proposes a simple self-calibration system that involves applying the phase-match method (PMM) in the far-field calibration of a deployed active array. When the proposed self-calibration approach is employed, an antenna array system can be maintained at a ground-based station, and no expensive and complex test equipment is required. An EM-based simulation method was applied to validate the proposed method numerically. Finally, an eight-element microstrip array operating at 3.6 GHz was designed to study the proposed method experimentally. The measured results validated the effectiveness of the proposed method in calibrating deployed antenna array systems.

A Novel Method for Calibrating Deployed Active Antenna Arrays

An element excitation method which provides a simple and fast way of determining the excitation of antenna elements in an active phased array as a function of the amplitude and phase setting is presented. These element ions can be used to align the amplitude and phase settings of the antenna elements of an active phased array for a desired radiation pattern. The complex electric field has to be measured in only one observation point in the far field of the antenna as a function of the element's amplitude and phase settings. The method is described in detail and excellent experimental results are shown. >

J.G. van Hezewijk

Papers

Fast determination of the element excitation of active phased array antennas