# Mechanically Reconfigurable, Beam-Scanning Reflectarray and Transmitarray Antennas: A Review
## 5 Hybrid Mechanical Movement Approach  
A combination of mechanical movement techniques in element, array and feed levels can be used to scan the beam of RAs/TAs [71, 72, 73, 74, 75, 76]. Reference [71] reported a folded RA antenna, which is capable of scanning its beam in two dimensions. This folded RA switched between seven feed beams in the E-plane while mechanically tilting the backside reflector for H-plane beam scanning. The proposed folded RA demonstrated a beam scanning performance of 16\({}^{\circ}\) in the E-plane and 9\({}^{\circ}\) in the H-plane at 76.5 GHz. A folded RA was proposed in [73] and consisted of a focusing array with a polarization rotating structure, a feed antenna and polarizing grids. The feed antenna and the focusing-and-polarization-rotating array were integrated within a single structure. By tilting this integrated structure, the phase center of the aperture was displaced and the antenna beam was steered at a rate twice the tilting angle of the integrated structure. The structure can scan the beam over \(\pm\)10\({}^{\circ}\) from broadside without any significant degradation.  
Another approach for combining feed displacement and array rotation was proposed in [74] which realized 1D \(\pm\)70\({}^{\circ}\) beam scan coverage. The phase matching and mode superposition synthesis methods were combined to synthesize an ultra-wide RA scan range with excellent beam scanning performance. Specifically, the RA achieved a measured gain of 26.2 dBi at broadside at 12 GHz, corresponding to an aperture efficiency of 42.5%. The measured gain variations of 3.1 dB and 4.9 dB were reported for the scan ranges of \(\pm\)60\({}^{\circ}\) and \(\pm\)70\({}^{\circ}\), respectively, demonstrating the ultra-wide scan coverage capability of this method. The TA antenna reported in [75] was implemented for Ka-band satellite-on-the-move terminals. Figure 10 illustrates how the beam-steering in the elevation plane was obtained by in-plane translation of the feed beam, while full azimuth coverage was obtained by rotating the whole TA. The developed prototype has a measured gain of 27 dBi at 30 GHz with a scan loss of 3 dB for an elevation beam-scanning range between 18\({}^{\circ}\) and 53\({}^{\circ}\). Moreover, this antenna prototype has a weight of less than 500 grams and this configuration potentially requires very low DC power to move, which is an attractive feature for a user terminal. By using a similar mechanically reconfigurable mechanism, the same author also presented two offset dual-band transmit arrays in [76] possessing  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**References**} & \multirow{2}{*}{**Methodology**} & **Operating Frequency** & **3 dB Beam** & \multirow{2}{*}{**Aperture Efficiency**} \\  & & **Bandwidth (GHz)-1 dB Gain** & & **Scanning Range** & \\ \hline
[42] & Fully illuminated single & 11.6–12.7 (9.1 \%) & \(\pm\)55\({}^{\circ}\) & 43.1\% \\  & focal array-reflectarray & & & \\ \hline
[58] & Fully illuminated single focal & NA & \(\pm\)27\({}^{\circ}\) & 24.5\% \\  & array-transmitarray & & & \\ \hline
[49] & Fully illuminated & & & \\  & multifocal array-reflectarray & & & \\ \hline
[56] & Partially illuminated & NA & \(\pm\)30\({}^{\circ}\) & 4.7\% \\  & array-reflectarray & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparative analysis of reconfigurable RAs using feed movement.  
23-29 dBi gain at 20 GHz(Rx) and 30 GHz(Tx), with an elevation beam scanning range of 0-50\({}^{\circ}\) and with a scan loss of less than 3.6 dB and F/D < 1.