Roland Dill

Field theory investigation of high-T/sub c/ superconducting coplanar waveguide transmission lines and resonators

An investigation is conducted of a coplanar waveguide structure using a partial wave synthesis taking into account the complex conductivity of the high T/sub c/ superconductor material according to the two-fluid model and the London theory. Micrometer transmission line dimensions are considered in the frequency range up to 100 GHz. The results obtained for superconductors are also compared with the results obtained for superconductors with real conductivity and the same geometry. The behavior of measured and published coplanar waveguide half wavelength resonators made of high-T/sub c/ superconducting thin films is also examined. >

FEM analysis of the reflection coefficient of SAWs in an infinite periodic array

A finite element tool for the analysis of infinite gratings of interdigital transducers in surface acoustic wave (SAW) devices has been developed. The computation of one period of the infinite structure together with the application of periodical boundary conditions makes the analysis of the total geometry possible. The eigenfrequencies of such a structure in the sagittal plane are calculated, and parameters (velocity, reflection) for the simulation programs of complete SAW devices are derived from them. The dependence of these parameters on the electrode shape has been analyzed and is presented.<<ETX>>

Design and analysis of single phase unidirectional transducers

Single-phase unidirectional transducers for SAW low-loss filters find increasing application in telecommunication systems like mobile telephone and cordless phone. These transducers employ a single metal layer fabrication which is important for low-cost and high-volume production. The matching of the filter is in general done with a simple two-element matching network on the input and the output of the filter. The design of the transducers employing withdrawal weighting and apodization is described. An extensive analysis of the transducer P-matrix elements including second-order effects like diffraction and finger resistance is presented. The measured filter performance is shown and compared to the analysis results.<<ETX>>

New resonator filter with high sidelobe suppression

A new resonator filter for IF applications which is superior to conventional approaches is reported. The design places acoustically coupled resonator cascades between two weighted single-phase unidirectional transducers (SPUDTs). This allows narrow bandwidth and small chip size, high sidelobe suppression, moderate group delay ripple and low loss at the same time. For full custom design sophisticated CAD tools are necessary. A filter was built at 225.0 MHz with a chip size smaller than 10 mm in a surface mounted device (SMD) package. The fractional bandwidth is 0.14%, sidelobes are suppressed more than 40 dB, the group delay ripple is smaller than 0.5 mu s, and the insertion loss is 4.5 dB.<<ETX>>

Design of generalized SPUDT filters

Single phase unidirectional transducer (SPUDTs) exhibit excellent frequency characteristics and are used in many surface acoustic wave (SAW) filters for IF filtering in mobile communication systems. They allow the design of narrow-band low-loss filters with smooth amplitude response. In the classical type of SPUDT filters the mechanical reflections are used to cancel the electrical regeneration. Thus the impulse response is close to the one calculated using the impulse model. In this limit has been overcome for the first time. Resonances in the transducers, or between the transducers, respectively, are used for improving the performance of a SPUDT filter for a given chip size. In this paper a general approach for the design of transducers including reflections will be outlined and the correlation to already well known SAW structures, e.g., inline resonator filters, will be figured out. A classification of the different types of generalized SPUDT based SAW filters will be given.

IF and RF filters for mobile telephone systems

IF and RF filters were developed for several mobile telephone systems using the well-known two-track filter technique. The filters have been designed for low insertion loss, high selectivity, and steep passband skirts and respond to the specific needs of the targeted system. Thus, IF filters, with insertion losses as low as 2 dB and RF filters with good overall characteristics have been obtained. The filters cover the frequency range from 110 MHz to 1.9 GHz. In addition, sophisticated design software leads to filters that can be easily matched. Examples of some filters at different center frequencies show good agreement between measurement and simulation.<<ETX>>

High-temperature superconducting resonator-stabilized coplanar hybrid-integrated oscillator at 6.5 GHz

A small-size coplanar oscillator has been designed and entirely fabricated on a 10-mm*10-mm/sup 2/ LaAlO/sub 3/ substrate in superconducting microwave integrated circuit (SMIC) technology. As an active element, a GaAs MESFET has been used. The oscillator is stabilized by a coplanar waveguide transmission line resonator patterned from a YBa/sub 2/Cu/sub 3/O/sub 7-x/ film onto the LaAlO/sub 3/ substrate. The oscillator, operating at 77 K, is characterized by a center frequency of 6.5 GHz and a power output of nearly 5 dBm. A single-sideband phase noise to carrier ratio of -90 dBc/Hz at 10-kHz offset has been attained. The attenuation of harmonics is better than 10 dBc.<<ETX>>

A 900 MHz ladder-type SAW filter duplexer

A low-cost hybrid-integrated SAW filter duplexer consisting of receiver top filter, transmitter final-stage filter and antenna terminal has been developed. The prototype design was oriented at the GSM system specifications in the 900 MHz-band. Three-stage ladder-type SAW filters have been designed to perform the duplexing function by the use of only one transmission line. The complete duplexer has an insertion loss of 1.2 dB in the Tx path (Tx) and 2.1 dB in the Rx path (Rx). The 3 dB-bandwidth is 40.1 MHz (Tx) and 47.4 MHz (Rx), respectively.

A novel SAW filter for IF-filtering in DECT systems

We have developed an improved SAW filter for IF-filtering in DECT systems. The filter is a two track reflector filter using EWC-SPUDTs as in- and output-IDTs and reflectors in the center of each track The propagation path of the SAW is folded in order to make better use of the total chip length. A similar configuration with identical reflectors in the tracks is known in literature, however, we used different reflectors in the tracks and this way we could improve the filter performance and especially the stop band attenuation considerably. The SPUDTs are withdrawal weighted, for the reflector design we used an electrode width weighting technique. The filter fits into a very small QCC10 package (9.1/spl times/7.1/spl times/1.8 mm/sup 3/) and has high performance so that it can be used in a DECT base-station, too. The substrate is LiTaO/sub 3/, X112.2Y, the center frequency is 110.59 MHz, the minimum IL is 8 dB typically, the 3-dB-bandwidth is 1.1 MHz and the stopband attenuation is better than 40 dB.

Property Calculations of a Superconducting Coplanar Waveguide Resonator

We present calculations of the properties of the first coplanar waveguide transmission line resonators patterned from high-Tc superconducting films at 8.8 and 6.5 GHz [1, 2]. Based on field calculations of the corresponding coplanar waveguides with infinite conductivity, performed by a partial wave synthesis (mode-matching method) [3], we obtain the superconductor losses subsequently using Londons theory. Due to the high conductivity of the superconductive material both the electric and magnetic fields within the superconductor may be assumed to be parallel to the surface planes. For the small conductor thickness the tangential electrical field on each surface plane depends on the tangential magnetic fields on both surface planes. This relation is modelled by the surface impedance matrix Zs. The substrate losses are treated in the field calculations and are also taken into account. The calculated overall Q values are compared with the measured values and it has to be pointed out, that the superconducting thin films are due to the available material datas of the YBaCuO superconductor and the used substrate materials of a very good quality, because they reach nearly their upper limit given by the known material datas.