This work presents a liquid crystal (LC) based phase shifter in a dielectric waveguide (DW) topology consisting of core and cladding for the W-band. For continuous tunability, a part of the core ...material is replaced by liquid crystal. Furthermore, suggestions of materials for designing such a DW, i.e. for core and cladding, are given in this paper. In comparison to other topologies, the advantage of this topology is that the necessary electric biasing can be realized easily, by placing electrodes directly on the cladding. With an electric biasing of ±550 V, a maximum differential phase shift of 430°, accompanied with insertion losses between 2.8 to 5.5 dB with standard WR10 connections, could be achieved. The maximum figure of merit is around 100 °/dB at 102 GHz.
The paper presents the first tunable GaN-based digital transmitter chain for 0.8-1.8 GHz range, suitable for MIMO systems in software-defined radio (SDR) installations. The demonstrator includes a ...4-stage digital GaN power amplifier (PA) MMIC and a continuously tunable bandpass output filter based on a barium strontium titanate (BST) thin-film varactor. The filter shows a fractional bandwidth of 7% as well as a minimum insertion loss and maximum input return loss of 0.6 dB and 13 dB, respectively. The module delivers a maximum output power of 3 W and efficiency stays above 40% over the whole tuning range, peaking at 89% for 1.2 GHz. This is to the author`s best knowledge the first reconfigurable digital Tx chain fully demonstrating the inherent advantages of the digital PA approach including broadband operation, compactness, efficiency and reconfigurability.
Two designs for compact continuously tunable phase shifters are presented employing integrated ferroelectric varactors based on screen-printed barium-strontium-titanate thick film. The circuits are ...based on left-handed transmission-line topologies that allow to realize very compact modules. The proposed designs have total lengths of 2.1 and 3.8 mm and provide a differential phase shift of more than 360° and a figure of merit of 51°/dB at 10 GHz. Furthermore, the phase shifters are in coplanar strip configuration, making them attractive for systems composed of balanced components.
This letter presents the design and the realization of a compact tunable filter integrated in ferroelectric ceramic substrate. The bandpass filter bases on an evanescent-mode dielectric cavity, which ...is loaded by a pair of tunable mushroom-type complementary split-ring resonators. Tunable impedance matching networks are additionally implemented to improve passband insertion loss across the tuning range. A prototype has been realized in a 12.5 mm × 9.5 mm × 0.8 mm planar module. Measurements confirm a frequency coverage from 2.95 to 3.57 GHz, a 3 dB fractional bandwidth below 5.4%, with an insertion loss between 3.3 dB and 2.6 dB.
This paper presents a resonant liquid crystal (LC) characterization at 60 GHz using a temperature controlled automated measurement setup. For the measurements the resonator is perturbed with LC ...inside a thin silica quartz tube. The LC orientation is accomplished by means of permanent rare earth magnets. Measurements are performed at 20°C. The investigated LC is the GT3-23001 mixture from Merck KGaA. The extracted values are compared with characterization results at 19 GHz. The extracted permittivities are ranging from 3.14 to 2.43 and the loss tangents from 0.0035 to 0.0191 for parallel and orthogonal orientation, respectively.
This paper presents an in-plane hollow waveguide crossover for W-band frequencies. This kind of crossover can be implemented e.g. into a Butler matrix, to simplify the fabrication process ...significantly. It is based on a partially dielectric filling of the waveguide, focussing the field in the center. The dielectric is placed in the center of a hollow waveguide crossing and has a star-shape. Inside the dielectric filled region, a higher order mode propagation is possible, which has no significant influence on the overall performance of the crossover. It shows an insertion loss between 0.8 dB to 1.0 dB in the frequency range of 101.5 GHz to 108.0 GHz, while the matching is better than -10 dB and even down to -20 dB between 105 GHz to 108 GHz. The isolated ports show transmission coefficients better than -20 dB over the whole frequency range and even down to -50 dB in the best performing frequency range.
In the field of oxide electronics, there has been tremendous progress in the recent years in atomic engineering of functional oxide thin films with controlled interfaces at the unit cell level. ...However, some relevant devices such as tunable ferroelectric microwave capacitors (varactors) based on BaxSr1−xTiO3 are stymied by the absence of suited compatible, very low resistive oxide electrode materials on the micrometer scale. Therefore, we start with the epitaxial growth of the exceptionally highly conducting isostructural perovskite SrMoO3 having a higher room-temperature conductivity than Pt. In high-frequency applications such as tunable filters and antennas, the desired electrode thickness is determined by the electromagnetic skin depth, which is of the order of several micrometers in the frequency range of a few gigahertz. Here, we report the pulsed laser deposition of a fully layer-by-layer grown epitaxial device stack, combining a several micrometers thick electrode of SrMoO3 with atomically engineered sharp interfaces to the substrate and to the subsequently grown functional dielectric layer. The difficult to achieve epitaxial thick film growth makes use of the extraordinary ability of perovskites to accommodate strain well beyond the critical thickness limit by adjusting their lattice constant with small shifts in the cation ratio, tuned by deposition parameters. We show that our approach, encompassing several orders of magnitude in film thickness scale whilst maintaining atomic layer control, enables the fabrication of metal-insulator-metal (MIM) varactors based on 50–100 nm thin BaxSr1−xTiO3 layers with high tunability above three at the Li-ion battery voltage level (3.7 V).
This work presents an interference based W-band single-pole double-throw (SPDT) in rectangular waveguide and liquid crystal technology. In radiometers, this kind of SPDT can be used e.g. for ...switching to the calibration load for power calibration. The SPDT is designed with an E-plane power divider, two different paths for the phase shifting regions, being separated by 30 mm to provide enough space for the used magnets for proof-of-concept, and a coupled line combiner, where the interference is taking place. Rexolite 1422 is serving as liquid crystal cavity. The matching is better than -12 dB between 88 GHz to 110 GHz, except a peak around 102 GHz. The insertion loss is less than 3 dB between 89 GHz to 105 GHz, while exhibiting an isolation of at least 9 dB in this frequency range. From 90 GHz to 100 GHz, isolation is even between 10 dB to 12 dB.
Two common and two new unit cells for artificial lines made of four reactive elements are studied concerning their sensitivity to capacitive changes and their applicability as capacitive sensors. It ...is shown that selection of the unit cell is very important and can highly influence the sensitivity. The shown principle is very powerful and can be scaled up to THz frequencies, only limited by available fabrication technology. A built planar differential microwave sensor based on artificial lines working at 2.3 GHz is presented. It features a simple output power evaluation instead of a classic but more complicated phase difference measurement. With power variation of up to 60 dB in dependence of small environmental dielectric changes it shows a very high sensitivity and dynamic range. Functional layer coatings can be applied easily due to its planarity and open wide application areas for biomedical sensing.
The efficiency is one of the most critical parameters in the design of RF power amplifiers. For classical power amplifier (PA) the efficiency drops dramatically in the back-off region. One ...possibility of enhancing the properties of the PA is the implementation of a load modulation as used in the Doherty topology. The idea of using an adaptive impedance matching network at the output of the transistor is presented and analyzed in this paper. The topology of the matching network enables the connection of the matching circuit directly to the transistor. The matching network has been designed using the minimum mean square error method and realized on a BST thick film substrate. The measured input impedance is in the range of several ohms for a load of 50Ohm as required for power amplifiers.
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