Stefan Freisleben

Modified ladder-type 2.4GHz SAW filter with transmission zero

This paper describes the design of 2.4–2.5GHz bandpass ladder-type SAW filter and methods to improve its characteristics. The structure of the filter is based on modified π-type topology with external matching inductors. The piezoelectric crystal (LiTaO3) is placed on the low temperature co-fired ceramic (LTCC) substrate while all external elements are completely integrated into LTCC. Input sections of the filter with their characteristics were considered in detail what allowed to reduce the degradation of the filter characteristics due to increasing of its bandwidth. An effective way to create a transmission zero by introduction of magnetic coupling between input and output matching coils is presented in the paper.

A small size high performance SAW duplexer for W-CDMA band VIII applications

With the development of multimode and multiband mobile phones, the requirements on electrical components with respect to cost, size and electrical performance have further increased. The tightened space restrictions impose a design challenge especially for W-CDMA band VIII SAW duplexers, where electrical performance requirements are already very high due to the rather small duplex distance of 10 MHz and the high relative bandwidth of the pass bands. In this paper we present our new 2.0 × 1.6mm2 SAW duplexer for WCDMA band VIII applications. Despite of its small size and low height profile, the duplexer has a superior selectivity and sufficient power durability.

Compact low-loss 2.4GHz ISM-band SAW bandpass filter on the LTCC substrate

This paper describes a design of a surface acoustic wave (SAW) ladder-type bandpass filter (BPF) for 2.4–2.5GHz ISM-band, based on the low temperature co-fired ceramic (LTCC) substrate, which can be used in 802.11b/g wireless LAN and Bluetooth applications. It obtains an excellent state-of-the-art performance in the ultra small package. The proposed architecture is based on a combination of SAW and low temperature co-fired ceramic (LTCC) technologies, where the multilayer LTCC substrate is used for integration of matching and passband-driving elements and for obtaining additional transmission zeros. It is comprised of three series and two parallel SAW resonators, realized on the LiTaO3 piezoelectric substrate and connected accordingly to a ladder-type T-topology circuit design, and an additional resonator to obtain an attenuation at 2.57–2.62 GHz IMT-E (TDD) band. Two input/output matching inductors and three additional inductors, permitting to obtain a sufficient suppression level at 2.11–2.17 GHz UMTS (DL) band and harmonics, are completely integrated within ceramic. The described bandpass filter has ultra small dimensions of 1.1 × 1.4 × 0.9 mm, very low insertion losses of −1.5 dB max in the passband. This fully matched SAW bandpass filter has achieved excellent selectivity performance with the up-to-date smallest package size.