Fast and Miniaturized Phase Shifter With Excellent Figure of Merit Based on Liquid Crystal and Nanowire-Filled Membrane Technologies

Abstract

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 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 • /dB, 48 • /dB, and 70 • /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.

Dynamic Modeling of Liquid Crystal-Based Metasurfaces and Its Application to Reducing Reconfigurability Times

“…In [36], the static voltage dependence of LC is studied and accurately predicted but the dynamics are not tackled. In [9], the LC temporal behaviour is experimentally measured for different commercially available materials in 4µm thick cells, but a model is not provided. Moreover, in optics, the phase change that occurs from this tilt dynamics can be well modelled, and the optical intensity change can be well predicted, since for such a short wavelength the LC is simply a medium in which several π-times phase changes happen [31].…”

Fast Reconfigurable Phase Shifter Based on a Chiral Liquid Crystal Configuration

“…In particular, since the decaying time when the bias is turned off takes longer than the rising time, research has been mainly focused on reducing decaying time. Wang et al [23] show that a circuit with a cell gap of 100 µm has a response time of about 22 s; when the cell gap is reduced to 4 µm, the response time is rapidly reduced to 125 ms. Another research group proposes the encapsulated LC in a polymer network (polymer-dispersed LC) to reduce the dynamic response [14]. When the polymerdispersed LC is used, since the LC molecules receive a strong aligning force at the adjacent polymer interfaces, the response time can be shortened because the same effect as the thinned liquid crystal layer is used.…”

Design of phase shifters in nanowire membrane technology and VCOs in CMOS technology at millimeter-waves for future full frontend integration.

“…This novel phase shifter uses the MnM slowwave microstrip line, enabling area reduction and, because it is fabricated directly on the MnM substrate, ease of integration with the rest of the beam-steering frontend. [20] 1.3.2 CMOS VOLTAGE-CONTROLLED OSCILLATORS AT E-BAND An electronic oscillator can be simplified down to an inductor-capacitor resonant circuit fed back by an inverting amplifier. The resonator has a selfoscillating frequency, at which its equivalent impedance will be purely real and equal to its equivalent losses, caused by ohmic losses in the conductors, dielectric losses due to the periodic repolarization of electrical dipoles in the capacitor's dielectric, substrate losses due to eddy currents in the case of an integrated resonator, etc.…”

“…20) to ensure low E-field leaking into the Si, increasing losses due to eddy currents. However, a more practical relation would be:𝑆𝑆 + 𝑆𝐿 < 𝑡(21) helping further minimize the substrate losses.…”