Daniel Kienemund

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.

Frequency extension of the fully printed phase shifter by paste composite optimization

This paper aims to propose new approaches based on fully screen printing technology for realization of tunable components with frequency extension based on BST paste composite optimization. The tunable phase shifters are fabricated to demonstrate the capabilities of these simple, flexible and low-cost methods. The proposed phase shifters contain tunable ferroelectric varactors in metal-insulator-metal (MIM) configuration, which are fully printed on top of an alumina carrier substrate with metallic and dielectric pastes, subsequently dried and cofired. The printed phase shifters work in different frequency ranges by using different ferroelectric composites. The BST pastes are optimized for low sintering temperature performance. Using BST composite with MgBO, the frequency range is extended to 7.6GHz.

Thick-film MIM BST varactors for GaN power amplifiers with discrete dynamic load modulation

Due to their extremely low static current consumption, varactors based on BST are perfect devices for realization of tunable and re-configurable components. This work presents fully screen-printed MIM thick-film BST varactors that are used to tune the load impedance for GaN HEMTs. The varactor tuning voltage is supplied in discrete steps using a high-speed GaN-based modulator. Modulated measurements with LTE and WCDMA signals show, for the first time, the functionality of a BST-based load modulation system and the power consumption of the load-modulation in dynamic operation. Using discrete dynamic load modulation, an average PAE of 27.3% was measured for the LTE signal with an ACLR below −45 dB.

Tunable Phase Shifter Based on Inkjet-Printed Ferroelectric MIM Varactors

Abstract This paper presents a new method for the fabrication of tunable multilayer ferroelectric components based on inkjet printing. Inkjet printing is a low-cost technology for selective film fabrication and has high potential for the preparation of tunable dielectric layers for radio frequency and microwave applications. With this technology, tunable metal-insulator-metal (MIM) capacitor is fabricated, that is composed of inkjet-printed Barium-Strontium-Titanate striplines and photo-lithographically structured gold electrodes. Compared to coplanar capacitors, such MIM varactors require significantly lower DC-voltage for tuning. By applying 20 V across a 1 μm-thick BST film, a tunability of 33% is achieved at 8 GHz and tunability of 60% by applying 50 V. To demonstrate the field of application of this MIM varactor, a tunable phase shifter is designed and fabricated at 8 GHz. A phase shift of 143° and a figure of merit (FoM) of 28°/dB are achieved by applying maximum 50 V tuning voltage.