We present a wideband reflectarray antenna with electronic beam-steering capability. The beam-steerable reflectarray uses an electronically reconfigurable polarization-rotating unit cell (PRUC) that acts as a wideband 1 bit phase shifter. The unit cell consists of four metallic single-headed arrows placed above a ground plane. The four arrows are connected to the unit cell’s bottom surface, which contains two p-i-n diodes for switching and three lumped inductors for RF–DC isolation. Changing the bias states of the two antiparallel p-i-n diodes reconfigures the unit cell between two operating states that provide a +90° and −90° polarization rotation (PR). Simulation results for the unit cell show a wide frequency range of 8.5–11.5 GHz over which the reconfigurable unit cell provides dominant reflection coefficients of >−2 dB and relative phase shifts of 0° and 180° for the two operating states. The proposed unit cell was used to construct a 256-element, fully electronically reconfigurable reflectarray prototype with aperture dimensions of 192 mm $\times192$ mm to demonstrate the design concept. The digital control circuitry needed to individually control the unit cells was also designed and fabricated. Experimental characterization of the reconfigurable reflectarray demonstrated the 2-D beam scanning capability within the scan range of ±60° over a 30% bandwidth.

We review mechanically reconfigurable reflectarray (RA) and transmitarray (TA) antennas. We categorize the proposed approaches into three major groups followed by a hybrid category that is made up of a combination of the three major approaches. We discuss the examples in each category and compare their performance metrics including aperture efficiency, gain, bandwidth and scanning range and resolution. We also identify opportunities to build upon or extend these demonstrated approaches to realize further advances in antenna performance.

We present a low-profile, mechanically beam-steerable antenna that implements the Risley prism beam-steering concept using only a single flat prism. The proposed antenna achieves 2-D beam steering and consists of two parts: a holographic leaky-wave antenna and a phase-shifting surface (PSS) that acts as a flat prism. The lower holographic leaky-wave antenna acts as the feed for the prism and provides a phase-shifting gradient over its output aperture. When paired with the flat prism, the system can provide 2-D beam steering by mechanically rotating the two layers against each other. Unlike conventional Risley-prism-based beam-steerable antennas, the proposed approach results in a very low-profile antenna and does not need spatial illumination of a two-prism system with a separate feed antenna. The flat prism is implemented using a PSS consisting of low-pass, hexagonal-shaped, spatial phase shifters. A prototype antenna with an overall thickness of only $1.1\lambda _{0}$ at 10 GHz was designed, fabricated, and experimentally characterized. Measurement results agree well with theoretical predictions and both show wide-angle beam scanning ranging from 0° to 57° in the elevation plane and 0° to 360° in the azimuth plane. The proposed antenna system has an equivalent aperture diameter of $7.1\lambda _{0}$ and a measured peak gain of 22.3 dBc at 10 GHz corresponding to an aperture efficiency of 34.5%. The proposed concept is expected to be useful in designing low-profile, beam-steerable antennas in which the scanning speed can be traded off to reduce system complexity.

We present the design and proof-of-concept demonstration of a dual-band reflectarray antenna capable of generating two beams at $X$ - and $Ku$ -bands, whose directions of maximum radiation can be set independently of each other. The reflectarray uses dual-band polarization-rotating (PR) unit cells with 1 bit phase quantization. The proposed unit cell provides independent phase shifts at two frequency bands by controlling a cluster of two orthogonal dipoles to operate as either +90° or −90° reflective polarization rotators. Two dipole clusters are interleaved in a unit cell and used to achieve dual-band operation. Simulation results of a unit cell designed to operate at $X$ - and $Ku$ -bands demonstrate independently controlled, dual-band PR operation over 16.1% and 20% bandwidths for the lower and higher bands, respectively. The dual-band unit cells were used to construct three different static reflectarray prototypes demonstrating the different ways where such independent phase control at the two bands of a dual-band reflectarray antenna may be advantageous. The three static reflectarray prototypes were simulated, fabricated, and experimentally characterized. Simulation and measurement results of these prototypes agree well and demonstrate independent phase shift control at the $X$ - and $Ku$ -bands over a relatively wide field of view without exciting grating lobes.

We present the design and high-power experimental characterization of a wideband, high-power-capable, electronically reconfigurable phase shifter for high-power phased-array applications. The device studied in this work offers an electronically switchable, 1-bit phase shift using the concept of polarization rotation (PR). The PR-based phase shifter is designed to work in a custom-designed, double-ridge (DR) waveguide environment. Two p-i-n diodes are used to control the transmission phase of the signal by rotating the polarization of the incident wave by either $+90^\circ$ or $-90^\circ$ with respect to that of the incident wave, thereby creating a wideband, 1-bit phase shift between the two states. Simulation results demonstrated that this element can work over one octave bandwidth ranging from 6 to 12 GHz. A prototype of the device was fabricated and experimentally characterized at low and high power levels. The measurement results confirmed the simulations and demonstrated the wideband, high-power-density capability of the device. High-power continuous-wave (CW) experiments were conducted across the entire 6–12 GHz band and demonstrated that the unit-cell-averaged, CW power handling capability of the device exceeds 23.6 W/cm $^2$ . High-power pulsed power experiments conducted at 9.382 GHz demonstrated that the unit-cell-averaged, peak power handling capability of the device exceeds 347 W/cm $^2$ for short-duration pulses.

This study presents a beam‐steerable antenna system that uses two mechanically‐rotatable, phase‐shifting surfaces (PSSs) functioning like a pair of Risley prisms for beam scanning operation at X‐band. One of the PSSs also acts as a lens, performing beam collimation in addition to providing a phase shift gradient. Unit cells constituting the two PSSs were co‐designed to determine the distance between the two surfaces that results in high transmission coefficients and small phase errors under different beam‐scanning conditions. Both simulation and measurement results have verified that the distance of 2 mm provides the best performance regarding to peak gain. Prototypes of the PSSs having circular apertures with diameters of at 10 GHz were fabricated and illuminated by a feed antenna to characterise the beam scanning performance. The measurement results of the proposed antenna system demonstrate the capability to steer the main beam within a scanning range with a maximum gain variation of less than 3.6 dB by rotating the two PSSs with respect to each other. The fabricated prototype provides side lobe levels less than , polarisation purity higher than 20 dB, and small beam pointing errors of no more than in all examined beam scan scenarios.