Phased Array Antenna Calibration Based on Autocorrelation Algorithm

Abstract

The problem of calibrating phased array antennas in a noisy environment using an autocorrelation algorithm is investigated and a mathematical model of the autocorrelation calibration method is presented. The proposed calibration system is based on far-field scanning of the phased array antenna in an environment with internal noise and external interference. The proposed method is applied to a phased array antenna and compared with traditional rotating-element electric-field vector methods, which involve identifying the maximum and minimum vector-sum points (REVmax and REVmin, respectively). The proposed calibration system is verified for a phased array antenna at 3 GHz. Experimental verification of the mathematical model of the proposed method demonstrates that the autocorrelation method is more accurate than the rotating-element electric-field vector methods in determining the amplitude and phase shifts. The measured peak gain of the combined beam in the E-plane increased from 7.83 to 8.37 dB and 3.57 to 4.36 dB compared to the REVmax and REVmin methods, respectively, and the phase error improved from 47° to 55.48° and 19.43° to 29.16°, respectively. The proposed method can be considered an effective solution for large-scale phase calibration at both in-field and in-factory levels, even in the presence of external interference.

Keywords: amplitude error; autocorrelation algorithm; far-field probe; phase error; phased array antenna; radiation pattern.

Figure 1

A Schematic diagram of the PAA calibration method based on the autocorrelation algorithm.

Figure 2

The simulation environment of the calibration showing reference (orange), fixed (green), and calibrated (blue) antennas and interference source (red): 2D²/λ = far-field distance in meters; λ = wavelength of the radiating wave in meters.

Figure 3

The radiation patterns of the combined beam in the E-plane when using different calibration methods: autocorrelation method—red; REVmin method—green; REVmax method—blue.

Figure 4

The calibration system diagram for the REVmax, REVmin, and autocorrelation methods.

Figure 5

The (a) signal processing block, (b) receiving antenna, and (c) reference (transmitting) antenna.

Figure 6

The software graphical user interface for automatic calibration control.

Figure 7

A diagram of the calibration system that produced the radiation patterns after performing the amplitude and phase shifts of the received signals using the REVmax, REVmin, and autocorrelation methods.

Figure 8

The radiation patterns of the combined beam in the E-plane when using different calibration methods in the cases (a) $D=0.625\lambda$ and φ_tr. = 0°; (b) $D=1.25\lambda$ and φ_tr. = 0°; (c) $D=0.625\lambda$ and φ_tr. = 240°; and (d) $D=1.25\lambda$ and φ_tr. = 240°. Autocorrelation method—red; REVmin method—green; REVmax method—blue.