The research on materials and systems for tunable microwave devices has gained attraction within the last years. The radio frequency characterization and the component design of tunable microwave components based on dielectric ceramics especially barium-strontium-titanate (BST) are presented in this second part, whereas the basic material properties are discussed in detail in the first part. After a short introduction to the processing technology used for the fabrication of tunable components based on a BST thick film, the relations between microwave properties and material properties as well as the microstructure are presented in detail. The design process for tunable microwave components based on BST thick films is described. Especially the considerations related to micro- and macrostructure and their connection are highlighted. The paper closes with two different application examples: a reconfigurable array antenna for satellite communication and varactors for high power applications.

Barium strontium titanate (BST) thin films are studied with respect to their application as tunable dielectric at microwave frequencies. BST thin films are deposited by means of radio-frequency magnetron sputtering on platinized Si substrates. The substrate to target distance during sputter deposition is varied and the effect on structure, topology, composition and electronic properties is monitored using X-ray diffraction, atomic force microscopy, Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy. These findings are related to the dielectric measurements, which are carried out at 1 MHz and in the microwave range up to 8 GHz using metal-insulator-metal structures with Pt electrodes. For further device evaluation, leakage current measurements are carried out. Changing the process parameter strongly affects the composition of the films. The results emphasize the possibility for enhancing the microwave properties by fine-tuning of the chosen process parameter.

The influence of Fe acceptor and Fe-F acceptor-donor co-doping, oil the dielectric response of screen-printed Ba0.6Sr0.4TiO3; thick-films oil alumina Substrates has been investigated. The Ba0.6Sr0.4TiO3 powders were synthesized by freeze-drying, of sols. Permittivity, dielectric loss, and tunability were investigated Lit kHz frequencies with a planar capacitor structure, and at GHz frequences up to 40 GHZ using coplanar waveguide structures. Pure acceptor doping by Fe was found to have a distinct influence on permittivity and dielectric loss-factor Lit kHz-frequencies and at GHz frequencies due to an internal bias field and pairs of associated defects. Co-doping with F significantly suppresses the influence of the internal bias field and defect-associates at low and microwave frequencies. The commutation quality factor at 10 GHz and E-eff=5.8V mu m(-1) was increased by co-doping the thick-films with Fe and F. Such doped Ba0.6Sr0.4TiO3 films show a high potential for tunable microwave applications.

Scaled varactors on a Barium-Strontium-Titanate (BST) thick-film are produced and characterized. The tunability of the scaled varactors is measured at up to 12.5 V/mum effective tuning field-strength in the planar varactors' air gap. To increase the effective tuning field-strength without breakdown and therefore to increase the tunability of the varactor the planar structure is covered with Parylene. As a result of the Parylene coating, a tuning field-strength of up to 29 V/mum can be applied to the varactors' gap which results in a capacitance tuning of 44.5 %. The humidity dependency of the quality factor of BST components based on porous thick-film can be eliminated. By sealing the porous surface, the quality factor of the varactors is significantly increased.

Low-cost planar high-Q ferroelectric-thick film varactors (Qap90) are realized and component architectures using resistive electrodes for dc bias are investigated. A basic model for planar capacitors with resistive electrodes in the gap is developed and verified by finite-difference time-domain simulations and measurements of interdigital capacitors with high-resistivity indium-tin-oxide bias electrodes in the gap. An optimized high-Q capacitor design based on a series connection of ferroelectric varactors with resistive bias decoupling is presented. The approach allows the increase of device linearity and the reduction of tuning voltages. Based on this technology, a continuously tunable high-power impedance-matching network for 1.875 GHz with tuning voltages below 60 V was developed, realized, and characterized by small- and large-signal measurements with up to 33-dBm input power. The device requires no external dc-block or RF decoupling and features separated RF and dc contacts. The output IP 3 of up to 47.8 dBm verifies the excellent device linearity

This letter demonstrates a scheme to characterize very precisely the field-dependent permittivity of nonlinear ferroelectric films using inhomogeneously tuned coplanar transmission lines. For the characterization, tunable coplanar waveguides on a screen-printed Ba0.6Sr0.4TiO3 (BST) thick film are realized and measured at radiofrequencies to determine the geometry-dependent tunability of the capacitance per unit length C'. To characterize the nonlinear tunability of the BST-thick film, these C'-values are compared with capacitance values simulated by the finite-difference time-domain method. Avoiding numerical instabilities of the iterative extraction procedure, the convergence of the extracted tunability is validated by three distinct geometries on the same BST substrate. The extracted tunability of the BST-thick film is 67% for an electric field-strength of 20V/mum. The precise knowledge of the field-dependent permittivity enables a distinct tunability optimization of frequency-agile radio frequency devices based on nonlinear ferroelectric films

A novel method based on a wideband equivalent circuit model is proposed to analyze the harmonic radiation of a tunable Planar Inverted-F Antenna (PIFA) tuned by a varactor. The nonlinear relationship between the input power, DC bias voltage and the dynamic RF voltage over the varactor are quantified for a single-band prototype. The radiation power is simulated at the first and second harmonic frequency. The verification is finally presented by measurement.

The present invention relates to dielectric ceramics produced therefrom thin and / or thick layers, and a method for producing the same and the use of the dielectrics and the thin and / or thick layers.

A tunable left handed (LH) transmission line used as continuously tunable phase shifter is presented. Using varactors based on barium-strontium-titanate (BST) thick films, a figure of merit FoM = 29deg /dB has been measured at 2.8 GHz. The bandwidth of the realized circuit using 3 unit cells reached 10%. The agreement of the presented result from simulation and measurement is good, the differences can be explained by tolerances of the used components. Additionally the simulations of a 180deg phase shifter based on the same components for the unit cell is presented. Simulated results of this phase shifter shows a bandwidth of 27% and a FoM max = 31.5deg /dB

The nonlinear behaviour of a phase shifter employing two different nematic liquid crystals (NLCs) as a tunable dielectric is investigated in this work. The NLCs used are the quasi-standard NLC 5CB and a highly anisotropic mixture MDA-03-2844. The third order intercept point IP3 was measured at 7.4 GHz. The utilized measurement setup allows the application of 40 dBm total power to the device under test (DUT) with an IP3 of the empty setup of at least 60 dBm. The output IP3 is at least 52 dBm for 5CB and 58 dBm for the mixture. The proposed phase shifter design therefore exhibits high linearity

This paper introduces switches based on tunable ferroelectric filters at microwave frequencies. A SPDT-switch design for the frequency range 2.4-2.5 GHz with switching contrasts of 40 dB and insertion losses below 0.5 dB is presented. Additionally, a first implementation of a 10 GHz bandpass-based SPST-switch was realized on a lossy ferroelectric-thick film of Ba0.6Sr0.4TiO3. The measured switching contrast amounts to 14.4 dB with a 1 dB-bandwidth of 5.4%.

In this paper a ridged waveguide phase shifter at W-band frequencies is presented. A taper matches the ridged waveguide phase shifter to the rectangular waveguide feed. Three different liquid crystals (LC) are used: a quasi-standard LC K15, a highly anisotropic mixture MDA-03-2844, and a dual-frequency switching LC MDA-05-1132, all synthesized by Merck KgaA. The return loss of the phase shifter device is always below -10dB in the whole W-band. The maximum achievable figure-of-merit of these materials is 78deg/dB at 108 GHz

A novel mixing principle based on the modulation of the transfer function of tunable filters has been implemented at 1.95 GHz. The varactor based filters used as single pole double throw (SPDT) switches offer switching contrasts of more than 30 dB. In combination with a phase shifter in one filter's output path and a power combiner, a switching-mode mixer has been realised.