Wideband evaluation of two types of slow‐wave microstrip lines

The design, characterization and comparison of two widely used approaches in realizing slow-wave effect on microstrip transmission lines, that is stub loaded and defected ground structure loaded microstrip lines are presented in a wide bandwidth (10–67 GHz) for the first time. Transparent substrate and dielectric material are chosen to ease the alignment of electrode and ground plane. Thin dielectric layer are applied to make the comparison prominent. The results indicate that defected ground structure loaded microstrip line has better RF performance in terms of compactness and insertion loss than stub loaded method within the whole band especially in thin film applications

Reconfigurable Millimeter-Wave Components Based on Liquid Crystal Technology for Smart Applications

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

Ridge Gap Waveguide Based Liquid Crystal Phase Shifter

In this paper, the gap waveguide technology is examined for packaging liquid crystal (LC) in tunable microwave devices. For this purpose, a line based passive phase shifter is designed and implemented in a ridge gap waveguide (RGW) topology and filled with LC serving as functional material. The inherent direct current (DC) decoupling property of gap waveguides is used to utilize the waveguide surroundings as biasing electrodes for tuning the LC. The bed of nails structure of the RGW exhibits an E-field suppression of 76 dB in simulation, forming a completely shielded device. The phase shifter shows a maximum figure of merit (FoM) of 70 °/dB from 20 GHz to 30 GHz with a differential phase shift of 387° at 25 GHz. The insertion loss ranges from 3.5 dB to 5.5 dB depending on the applied biasing voltage of 0 V to 60 V. © 2013 IEEE

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

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 Ω 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

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Liquid Crystal Dielectric Image Lines for Integrated Reconfigurable Millimeter-Wave Beamsteering Applications

This work investigates the capabilities and performance of liquid crystal based dielectric image lines as a basis for reconfigurable millimeter-wave components and their use for beam-steerable antennas. The components, which are operated at W-band (75 GHz to 110 GHz), are designed, manufactured and characterized. The dielectric image line topology is well suited to combine the advantages of fully dielectric waveguides with the integrated character of commercial devices. Especially, the integration of liquid crystal can be easily achieved, and does not require modifying the printed circuit board on which the dielectric image line is placed. As a basis for the components, suitable materials are analyzed first, before an adaptive measurement setup is introduced. Two modes of the dielectric image line are of particular interest in this dissertation: the fundamental Ey 11-mode and the orthogonally polarized higher-order Ex 11-mode. The first components are liquid crystal phase shifters of low permittivity (εr = 2.53). In the fundamental mode, a low profile, a maximum figure-of-merit of 136 °/dB, response times of 6 s to 9 s and linear performance in a temperature range from −10° to 80° are achieved. With the orthogonally polarized mode, a higher figure-of-merit of 188 °/dB is obtained at the cost of higher response times. Utilizing a special design, the electrodes can be employed directly on the dielectric. This results in fast switch-on response times in the range of milliseconds, which is the fastest time obtained with dielectric waveguides up to today. This high decrease in switch-on response time represents a 99% and 97% improvement when compared to a fully dielectric liquid crystal phase shifter and a classic electrode placement besides the dielectric image line, respectively. On the basis of the phase shifters, reconfigurable antennas are investigated in the dielectric image line topology. With broadband rod antennas, 1×4 array demonstrators are realized. By utilizing multimode-interference for the first time in the dielectric image line topology at millimeter-waves, compact power dividers are realized. Combining the array with the aforementioned phase shifters leads to the first liquid crystal dielectric image line rod antenna phased array. It shows gain of 17 dBi to 18 dBi and has a beam steering range of ±10°. As a less complex and more narrowband alternative, a liquid crystal leaky wave antenna is introduced, too. By allowing the bias electrodes to contribute to the radiation characteristics, a simple antenna is realized, with a gain of 15 dBi, capable of scanning 10° by applying only one bias voltage. Furthermore, novel additive manufacturing techniques are evaluated to allow automated fabrication of the investigated components. An innovative guiding mechanism, which enables the combination of liquid crystal with high permittivity materials (εr = 9), is introduced as a means of enabling smaller components

A Compact and Fast 1 × 4 Continuously Steerable Endfire Phased-Array Antenna Based on Liquid Crystal

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

Temperature Characterization of Liquid Crystal Dielectric Image Line Phase Shifter for Millimeter-Wave Applications

In this paper we investigate the temperature dependent behavior of a liquid crystal (LC) loaded tunable dielectric image guide (DIG) phase shifter at millimeter-wave frequencies from 80 GHz to 110 GHz for future high data rate communications. The adhesive, necessary for precise fabrication, is analyzed before temperature dependent behavior of the component is shown, using the nematic LC-mixture GT7-29001. The temperature characterization is conducted by changing the temperature of the LC DIG’s ground plane between −10°C and 80°C. The orientation of the LC molecules, and therefore the effective macroscopic relative permittivity of the DIG, is changed by inserting the temperature setup in a fixture with rotatable magnets. Temperature independent matching can be observed, while the insertion loss gradually increases with temperature for both highest and lowest permittivity of the LC. At 80°C the insertion loss is up to 1.3dB higher and at −10°C it is 0.6dB lower than the insertion loss present at 20°C. In addition, the achievable differential phase is reduced with increasing temperature. The impact of molecule alignment to this reduction is shown for the phase shifter and an estimated 85% of the anisotropy is still usable with an LC DIG phase shifter when increasing the temperature from 20°C to 80°C. Higher reduction of differential phase is present at higher frequencies as the electrical length of the phase shifter increases. A maximum difference in differential phase of 72° is present at 110 GHz, when increasing the temperature from 20°C to 80°C. Nevertheless, a well predictable, quasi-linear behavior can be observed at the covered temperature range, highlighting the potential of LC-based dielectric components at millimeter wave frequencies