Alex Wiens

Transmission lines loaded with pairs of magnetically coupled stepped impedance resonators (SIRs): Modeling and application to microwave sensors

This paper is focused on the analysis and modeling of transmission lines loaded with pairs of shunt-connected stepped impedance resonators (SIRs), and their application to differential sensors for dielectric characterization, and for diagnosis and quality control of material samples by comparison to a reference. It is demonstrated that by placing the SIR junctions in the same position of the line, the SIRs are magnetically coupled. Such coupling has significant influence on the sensitivity of the sensor, determined by the split in frequency caused by an asymmetric dielectric loading of the SIRs. The circuit model of the structure, including magnetic coupling between SIRs, is proposed and validated through electromagnetic simulations and measurements. Finally, the principle of sensing is experimentally validated by a proof-of-concept demonstrator.

Transmission Lines Loaded With Pairs of Stepped Impedance Resonators: Modeling and Application to Differential Permittivity Measurements

Differential techniques are widely used in communication and sensor systems, as these techniques have been shown to improve the performance. This paper shows how differential sensing of permittivity can be conducted in a simple way. For that purpose, a microstrip line loaded with a pair of stepped-impedance resonators is used in two different resonator connections: parallel and cascade. Each resonator is individually perturbed dielectrically so that: 1) when the two individual permittivities are identical, the structure exhibits a single resonance frequency and 2) when the permittivities are different, resonance frequency splitting occurs, giving rise to two resonances (all these resonances are seen in the form of transmission zeroes). The two sensing approaches are successfully validated through electromagnetic simulations and experiments. By virtue of a differential measurement, robustness against changing ambient factors that may produce sensor miscalibration is expected.

Beam Steering Phased Array Antenna With Fully Printed Phase Shifters Based on Low-Temperature Sintered BST-Composite Thick Films

This letter presents a novel approach to fully-printed phase shifters for electronically steering the beam of a phased array antenna at S-Band. The phased array consists of four microstrip patch antenna elements and phase shifters, as well as a four-to-one feeding network. As key components in the circuit, the phase shifters are provided with a microstrip loaded-line topology, equipping fully-printed metal-insulator-metal (MIM) varactors with low-temperature sintered BST composite thick films between the top and bottom silver electrodes. Furthermore, a simple biasing concept is implemented for controlling the phase shifter. The fully-printed, low-cost phase shifters achieved a phase shift of 274° and a FoM of 37.3°/dB at 3 GHz. The length of the phase shifters was 0.2λ, where their phase shift versus length resulted in a 14.4°/mm measurement, outperforming all previously reported phase shifters based on fully-printed low-temperature sintered BST thick film. The beam-scanning range of the four-antenna element array was ±30°.

Steerable Dielectric Resonator Phased-Array Antenna Based on Inkjet-Printed Tunable Phase Shifter With BST Metal-Insulator-Metal Varactors

This letter presents a steerable phased-array antenna at C/X-band. The phase shifters used in the design, are implementing inkjet-printed barium strontium titanate (BST) thick-films. This method enables low-voltage tuning and low fabrication cost. The phase shifter is tuned by integrated metal-insulator-metal varactors, whose electrodes are fabricated by photolithography and inkjet-printed dielectric layer. A tunability of 46% at 8 GHz is achieved by applying 50 V across a 1.2- μm-thick BST film. The 11-unit-cells loaded-line tunable phase shifter achieves a figure of merit above 40°/dB from 7 to 8.5 GHz. Dielectric resonator antenna, fabricated from bulk-glass ceramic, has been implemented as radiating element with a stacked architecture for wide bandwidth and high gain. A beam steering of ±30° has been measured with a 1 ×4-element phased array in the anechoic chamber.

Fully printed tunable phase shifter for L/S-band phased array application

In this paper, a novel fully printed method is presented for fabrication of phase shifter devices, aiming for phased array applications. This technology offers a simple and low cost way compared to other available technologies. The proposed phase shifter contains tunable ferroelectric varactors in metal-insulator-metal (MIM) configuration, which are fully printed on top of a carrier substrate. The printed phase shifter exhibits a figure of merit (FoM) of 70°/dB at 1.72GHz and shows a high potential for an implementation in fully printed phased array antennas.

Inkjet printed BST thick-films for x-band phase shifter and phased array applications

This paper presents a novel method of inkjet printed Barium-Strontium-Titanate (BST) material for low-cost RF application. To demonstrate its capability in phased array antenna application, a compact continuously tunable load line phase shifter in the frequency range from 8 GHz to 10 GHz is realized. The BST thick-film is printed at the areas which interdigital capacitors are later patterned. A phase shift of 175° and the figure of merit (FoM) of 20° /dB at 10GHz are achieved. The size of the planer circuit is 8mm × 6mm.

Load modulation for high power applications based on printed ceramics

This paper addresses the design and measurement of a low cost tunable impedance matching network (TMN) employing Barium-Strontium-Titanate (BST) for high frequency and high power applications. Based on requirements of a class AB mode high power amplifier, a pi-topology circuit was designed, photo-lithographically processed and measured. The work demonstrates a tunable matching network, transforming low impedance Zi=(4..13)-(3.5..13)j Ohm to a fixed 50 Ohm load, exhibiting insertion losses of not more than 0.9dB at 2.0 GHz. For initial testing, a tunable PA was designed by implementing the TMN at its output. First system measurements show an output power of 40.5dBm with a drain efficiency of 58% at 2.0 GHz.

Wideband tunable GaN HEMT module utilizing thin-film BST varactors for efficiency optimization

This work covers the design and measurement of a low cost tunable impedance matching network (TMN) for highly linear and high power RF applications at telecommunication frequencies. A single transistor cell, was wire-bonded to a TMN and the performance of the tunable amplifier module was evaluated from 1 GHz to 2.5 GHz. The TMN transforms the GaN HEMT output impedance to fixed 50 Ohm load. Tuning allows efficient operation of the transistor over the targeted frequency range. Peak drain efficiency of 66% and a peak output power of 37.5 dBm were measured. Two-tone measurements reveal an OIP3 around 47 dBm which is comparable to a bare GaN HEMT.

Tunable microwave component technologies for SatCom-platforms

Modern communication platforms require a huge amount of switched RF component banks especially made of different filters and antennas to cover all operating frequencies and bandwidth for the targeted services and application scenarios. In contrast, reconfigurable devices made of tunable components lead to a considerable reduction in complexity, size, weight, power consumption, and cost. This paper gives an overview of suitable technologies for tunable microwave components. Special attention is given to tunable components based on functional materials such as barium strontium titanate (BST) and liquid crystal (LC).

Temperature dependence of a tunable phase shifter based on inkjet printing technology

This work adresses the temperature dependence of tunable components based on inkjet printed low temperature sintered Barium-Strontium-Titanate (BST) thick-film layers. To evaluate the temperature dependence, metal-insulator-metal (MIM) parallel-plate capacitors were fabricated and characterized over a temperature range between -60°C and 100°C. A relative capacitance shift below 8.3% was measured in the unbiased state and 1.4% in the biased state. To evaluate the impact of this shift, a phase shifter was fabricated and characterized within the same temperature range. Around 4.5 GHz a maximum figure of merit of 46.7°/dB was measured, having a 92.7° phase shift by applying 50V tuning voltage. The relative phase shift due to temperature is below 4.7%, which shows promising results for a wide temperature operation range.