Code-Modulated Embedded Test and Calibration of Phased-Array Transceivers

Abstract

We present methods for built-in test and calibration of phased arrays using code-modulated embedded test (CoMET). Our approach employs Cartesian modulation of test signals within each element using existing phase shifters, combining of these signals into an aggregate code-multiplexed response, downconversion and creation of code-modulated element-toelement "interference products" using a built-in power detector, demodulation of correlations from the digitized interference response, and extraction of amplitude and phase per element using an equation solver. Rotated-axis methodology is discussed for accurate extraction of phase near the original 0/90/180/270 degree axes. Our techniques are demonstrated at board level for both receive and transmit modes using an eight-element 8-16 GHz phased array constructed using ADAR1000 chips from ADI. At 6 GHz, CoMET-extracted gain and phase are accurate to within 0.2 dB and 3 • compared to network-analyzer measurements. We then employ CoMET in a calibration loop to determinate optimum control settings at 6 GHz, outside the 8-16 GHz band for which the array was designed. We achieve seven-bit phase resolution with equalized gain. The root-mean squared gain and phase errors are improved from 0.8 dB and 8 • before calibration to 0.1 dB and 1.7 • after calibration.Index Terms-code-modulated embedded test, CoMET, codemodulated interferometry, phased array, built-in self-test, calibration, phase shifter.

Low-Complexity Online Calibration for Large-Scale Multi-Beam Antennas

“…To investigate the calibration performance of the proposed method, we derive closedform calibration accuracy expressions with respect to noise. As shown in Figure 4, two types of noise are involved [22]: n and x. The noise n in Equation ( 2) is the channel noise "before" correlation, The noise x k = c T k n in Equation ( 4) and Equation ( 9) is the noise "after" correlation.…”

“…/a k ) 2 − ln ( a 1 /a 1 ) 2 ( a k /a k ) 2 − ( a 1 /a 1 ) 2 . (A5)Substituting(22) into a k = | ω k | and separating the real part from the imaginary part, ( a k /a k ) 2 can be given by Equation (A6) is converted into the sum of squares of two non-zero mean Gaussian random variables. Then we convert Equation (A6) to the Gaussian distribution with variance 1 and obtain a random variable Y with non-central chi-square distribution as follows: χ 2 (2, 2a 2 k /σ 2 ).…”

Design of Ka-Band Phased Array Antenna with Calibration Function

“…Zhang et al [10] proposed an improved phased array calibration method based on the complex array signal measured by a single probe. Hong et al [11] proposed a method for inbuilt testing and calibration of phased arrays in free space using coded modulation embedded tests.…”