For the first time, a liquid crystal (LC) filled lens antenna is investigated for beam steering in this paper. The LC’s anisotropy is applied inside a semicircular shaped parallel plate waveguide to achieve a deflection of the propagating electromagnetic wave at the interface of lower and higher permittivity. Using an electrode network, the direction of the sector of higher permittivity can be adjusted, and therefore, the beam direction. Main advantage of this antenna concept is that neither phase shifters nor switching networks are needed, resulting in a very simple approach for beam steering Operating at V-band, from 50 to 75 GHz, the first demonstrator proves the antenna concept by reconfiguring the beam in pre-defined directions of −30°, 0° and +30° to simplifiy the electrode biasing network. Furthermore, it is feasible and being demonstrated to adjust the beam width and to generate multiple beams In the measurements, the antenna exhibits a measured input reflection below −10 dB over the complete frequeny range. For the unsteered radiation pattern, the side lobe level is between −8 to −12 dB, while these values degrade to −4.5 to −6 dB for the steered radiation pattern at ±30°. The measured gain is between 13 to 15 dBi.

This letter presents a highly miniaturized continuously tunable microstrip line phase shifter from 10 to 67 GHz. The design takes the advantage of the microstrip line topology by a ground plane with defected ground structures (DGSs). This leads to slow wave (SW) effect of the transmission line (TL), thus the TL can be physically compact, while maintaining its electric length. By applying tunable microwave liquid crystal (LC) with an anisotropic permittivity as dielectric, a delay line phase shifter is realized. The proposed microstrip LC phase shifter with DGS and a standard microstrip LC phase shifter as reference are both filled with 20-mm-thick high-performance LC GT3-23001. By comparison, the one with DGS exhibits a significant SW effect and an improved LC tuning efficiency which leads to a remarkable enhancement of figure of merit (FoM) and compactness than the reference. A second microstrip LC phase shifter utilizing DGS filled with 5-mm thick more advanced GT7-29001 LC shows outstanding FoM of 55°/dB, compactness of $201^{\circ }/{\lambda }_{0}$ , and response time of 210 ms.

This article presents the design of a Ka-band beam-switchable and beam-steerable endfire planar Yagi–Uda antenna array fed by a wideband Butler matrix, combining continuously tunable phase shifters based on a liquid crystal (LC) technology. The proposed array consists of four wideband 3 dB 90° branch-line couplers, two novel wideband via-less crossovers, LC-based 135° microstrip (MS) delay line phase shifters, and planar endfire Yagi–Uda antennas. The Butler matrix realizes beam switching, while LC phase shifters enable continuous beam steering inbetween the discrete beam positions. In this way, long delay line phase shifters are avoided for achieving 360°, reducing the phase shifter insertion losses (IL). Besides, such a hybrid beam steering method is expected to respond faster and more accurate. The array has two metallized layers, which can be easily fabricated by standard photolithography procedures. The fabricated array demonstrator is measured in terms of $S$ -parameters and far-field patterns. The measured return loss and isolation of the array are both ≥15 dB from 26 to 30 GHz. The beam is switchable among ±15° and ±45° in E-plane. By applying bias voltage up to 5 V to the LC phase shifters, the beam can be further continuously steered, covering almost −60° to +60° with acceptable sidelobe level. The maximum gain of the array is estimated to be 5.6 dBi. The radiation efficiency is 12%.

This paper presents recent development of tunable microwave liquid crystal (LC) components in the lower millimeter wave (mmW) regime up to the W-band. With the utilization of increasing frequency, conventional metallic waveguide structures prove to be impractical for LC-based components. In particular, the integration of the electric bias network is extremely challenging. Therefore, dielectric waveguides are a promising alternative to conventional waveguides, since electrodes can be easily integrated in the open structure of dielectric waveguides. The numerous subcategories of dielectric waveguides offer a high degree of freedom in designing smart millimeter wave components such as tunable phase shifters, filters and steerable antennas. Recent research resulted in many different realizations, which are analyzed in this paper. The first demonstrators of phased array antennas with integrated LC-based phase shifters are reviewed and compared. In addition, beam steering with a single antenna type is shown. Furthermore, the possibility to realize tunable filters using LC-filled dielectric waveguides is demonstrated.

This paper presents a highly miniaturized tuneable microstrip line phase shifter for 5 GHz to 67 GHz. The design takes advantage of the microstrip topology by substituting the ground plane by a metallic-nanowire-filled porous alumina membrane (NaM). This leads to a slow-wave (SW) effect of the transmission line; thus, the transmission line can be physically compact while maintaining its electric length. By applying a liquid crystal (LC) with its anisotropic permittivity as substrate between the transmission line and the NaM, a tuneable microstrip line phase shifter is realized. Three demonstrators are identically fabricated filled with different types of high-performance microwave LCs from three generations (GT3-23001, GT5-26001 and GT7-29001). The measurement results show good matching in a $50\ \Omega$ system with reflection less than −10 dB over a wide frequency range. These demonstrators are able to reach a maximum figure of merit (FoM) of 41 $^{\circ }$ /dB, 48 $^{\circ }$ /dB, and 70 $^{\circ }$ /dB for different LCs (GT3-23001, GT5-26001 and GT7-29001, respectively). In addition, experiments show that all three LCs should be biased with square wave voltage at approximately 1 kHz to achieve maximum tuneability and response speed. The achieved response times with GT3-23001, GT5-26001 and GT7-29001 are 116 ms, 613 ms, and 125 ms, respectively, which are much faster than other reported LC phase shifter implementations. Large-signal analysis shows that these implementations have high linearity with third-order interception (IP3) points of approximately 60 dBm and a power handling capability of 25 dBm.

This letter presents a planar endfire Yagi-Uda antenna phased array fed by a corporate network. The phase of each radiating element is controlled by a loaded line phase shifter based on liquid crystal technology. The phase shifters are meandered to minimize the dimension of the array and are measured to provide maximum differential phase shift of 400 ${^\circ }$ with a figure-of-merit of ${54}{{^\circ }\rm {dB}^{-1}}$ at 28.4 GHz. Each phase shifter is tuned individually by applying bias voltage through high impedance chromium line together with dc blocks. The array is designed for full-range scanning in E -plane with $>\!{360}{^\circ }$ phase shifters. Measurements show that it can be steered from −40 ${^\circ }$ to 40 ${^\circ }$ by applying dc bias in the range of 0–5 V and from −50 ${^\circ }$ to 60 ${^\circ }$ with degraded patterns. The maximum gain of the phased array antennas is measured to be 4.5 dBi. The array beam is able to be fast steered within approximately 1 s.