14.7 An Adaptive Analog Temperature-Healing Low-Power 17.7-to-19.2GHz RX Front-End with ±0.005dB/°C Gain Variation, <1.6dB NF Variation, and <2.2dB IP1dB Variation across -15 to 85°C for Phased-Array Receiver

Phased arrays have demonstrated great potential in 5/6G communication, radar and sensor applications [1– 4]. To achieve excellent performance, phased arrays require low-noise and high-linearity front-ends [5]. Most importantly, arrays demand uniform performance from all elements for optimum receiving G/T value and transmission effective isotropic radiated power (EIRP) [6]. Figure 14.7.1 exemplifies it with an array whose antenna element has 3dBi uniform gain on one side and no radiation on the other side. When all elements in an $8 \times 1$ linear array with a $\lambda/2$ space have identical characteristics, the array presents a 19dBi gain in the normal direction. Any temperature change in the array can be decomposed into an absolute temperature change superposed with a relative temperature variation. When the absolute temperature increases, the frontend gain decreases by as much as $-0.1dB/^{\circ}C$ [1]. When there is non-uniform solar radiation or heat generation inside the array, the relative temperature variation may present a gradient or a parabolic distribution. Taking a $64 \times1$ array as an example, when there is a gain/phase mismatch with an average value of $0.125dB/1.25^{\circ}$ between adjacent elements in a parabolic distribution locating at the center of the array, the formed beam presents a 1.4dBi main-lobe reduction in the normal direction and an 11.9dBi side-lobe degradation, shown in Fig. 14.7.1. It also shows an active array receiver front-end highlighting all the temperature-sensitive blocks. Calibration can adjust temperature-dependent performances [7]. However, periodic calibration inevitably takes time overhead and prevents array systems from full-time operations. Digital background calibration allows systems to operate uninterrupted, but may induce antenna boresight instability due to abrupt gain/phase change. In contrast, analog background calibration like adaptive healing design can resolve the above issues [8]. In this paper, we present an adaptive analog temperature healing receiver front-end with ± $0.005 dB/^{\circ}C$ gain variation from -15 to $85^{\circ}C$ environment temperature for a 17.7-to-19.2GHz phased array.