A Novel Simple Miniaturization Technique for Microstrip Couplers

This paper analyzes the new compact design of couplers based on the use of microstrip lowpass filters. The proposed design achieves significant reduction in coupler size while obtaining the same characteristics as of the conventional coupler. Prototype of the coupler with the central frequency of 1 GHz was produced on the substrate with dielectric permittivity of 4.4. The experimental results showed good agreement with numerical simulations. The size of the rat-race coupler was reduced by 83.7%. © 2019 IOP Publishing Ltd.Ministry of Education and Science of the Russian Federation, Minobrnauka: № 8.2538.2017/4.6Author are grateful for the simulation software NI-AWR Design Environment provided by the National Instruments Company. The research was executed by the grant of the Ministry of education and science of the Russian Federation (project № 8.2538.2017/4.6). The research was performed on equipment of the Urals Federal University common use center

Multi-Layer Ultra-Wideband Wilkinson Combiner for Arrays

This work investigates an ultra-wideband (UWB), compact, and multilayer Wilkinson power combiners for tightly coupled array (TCA) designs. The Wilkinson topology designs encompass UHF, L-, and S-bands. These combiners integrate into an experimental UWB TCA. The experimental UWB TCA divides into twenty-four columns, with each column containing eight unit cells, and each cell one-inch square. The Wilkinson power combiner contains eight input ports and one output port. Twenty-four combiners mount to the TCA’s back. The combiner condenses the two-dimensional array (8x24) to a one-dimensional or linear array (1x24). The proposed Wilkinson power combiner possesses a multilayer design reducing common mode current problems caused by vias. The Wilkinson combiner covers 500 MHz to 3.28 GHz and provides a 6.56:1 bandwidth. It achieves tight impedance matching through stripline coupling. The proposed design provides minimal phase error, equal power reception, and low power handling. The power combiner interfaces with an experimental UWB TCA antenna through SMP snap connectors. This paper examines signal combining efficiency to provide minimum path loss. This paper also examines interconnecting transmission lines traversing multiple laminate layers. This necessitates proper current handling because interconnects influence impedance, transmission, and isolation. Integrating a via picket fence improves port isolation and reduces propagating parallel plate modes. The proposed combiner design achieved the following important attributes at or better than the minimum required specifications. The measured combiner design successfully demonstrated -7.8dB minimum return loss for input and -18.1dB return loss for the outputs; 10.92dB ± 1.28dB insertion loss; -12.2db minimum isolation; ± 1.38° minimal phase error; ± 0.57dB power reception imbalance. The proposed UWB combiner design condensed the four-stage Wilkinson footprint to consume no more than 0.4in² (258mm²) surface area, weighed only 1.5oz (42.5g), and less than a half-inch thick

Investigation of advanced Butler matrices with integrated filter functions

This study presents a novel synthesis technique for Butler matrices that include filter transfer functions through a circuit based only on resonators. The Butler matrix is the fundamental building block to split and recombine the signals in Multi-port Power Amplifiers, where multiple inputs are delivered to a bank of amplifiers sharing them, and later recombined through an output network. However, to suppress spurious frequencies generated by the amplifiers or to provide near-band rejection in order not to interfere with other transmission/receiving bands, separate filtering is often required. Here, the traditional properties of the Butler matrix are included together with filtering selectivity into one single device based only on coupled resonators. An analytical synthesis procedure of the coupling matrix is presented here for the first time. The proposed solution has shown significant advantages in terms of size reduction compared to the traditional baseline consisting of a Butler matrix plus a bank of band-pass filters. Based on the technique proposed, three prototypes are designed and manufactured: a 180° hybrid coupler based on resonators and two versions of a 4x4 Butler matrix with filtering, built with additive manufacturing and with milling. Experimental measurements are in good agreement with simulations and theoretical expectations

Impedance Transformers

Non

Liquid Crystal Mixed Beam-Switching and Beam-Steering Network in Hybrid Metallic and Dielectric Waveguide Technology

Future communication systems at W-band are demanding highly directive antenna systems with beam-steering capability. For the hardware implementation of analogue beam-steering at millimetre waves, the microwave liquid crystal (LC) technology is ideally suited. It takes advantage of specifically synthesised LCs for microwaves in combination with appropriate device and biasing concepts, where the orientation of the LC, and therefore, its effective permittivity can be continuously tuned. It has low dielectric losses above 10GHz with a decreasing trend with increasing frequency. To exploit these unique characteristics, the focus of this scientific work is set for the first time on the investigation of an LC-based network with mixed discrete beam-switching and continuous beam-steering capability between the switching states for high-gain antennas at W-band. It consists of a Butler matrix combined with continuously tuneable phase shifters and a novel type of RF switch, an interference-based Single-Pole n-Throw (SPnT). The interference principle of the SPnT allows a continuously adjustable power splitting ratio, and hence, the generation of multiple beams. Different technologies are investigated for the realisation of this mixed network. Due to its high level of integrability and compact designs, the standard low temperature co-fired ceramic technology is examined, however, for a first proof-of-concept at Ka-band only. For W-band, two low-loss technologies are investigated: tuneable metallic and dielectric waveguides. While metallic waveguides are well suited for the realisation of low-loss non-tuneable feeding networks, dielectric waveguides are better suited for the realisation of tuneable LC components at (sub)millimetre waves, since no metallic boundaries are limiting the integration of an electrical biasing network. As non-tuneable core part, a Butler matrix with an average insertion loss of 3.5 dB at 102 GHz is realised, which is based on a novel multifunctional crossover design, allowing a miniaturised in-plane realisation of the overall mixed network. As key component for tuning of the mixed beam-switching and beam-steering network, a step-index dielectric waveguide phase shifter is presented. With a phase shifter figure-of-merit of 100 °/dB at 102 GHz, this fully electrically biased phase shifter is going far beyond the state-of-the-art for electrically tuneableW-band phase shifter. To stay on the same technology platform and to allow an in-plane realisation from the input port up to the radiating elements, the interference-based SPnTs are additionally investigated by a hybrid implementation of metallic and dielectric waveguides. It exhibits an insertion loss of 3dB, while providing an isolation of 27 dB. Hence, this hybrid metallic and dielectric waveguide technology reveals a high potential not only for the presented LC-based mixed beam-switching and beam-steering network, but also for LC-tuned continuous beam-steering networks at frequencies above 100 GHz, since low-loss metallic waveguide feeding networks can be generally combined with high-performance tuneable dielectric waveguides