Development of planar filters and diplexers for wireless transceiver front ends

The central theme of this work is the design of compact microstrip bandpass filters and diplexers and the investigation of applications of these circuits in integrated transceiver RF front-end. The core of this thesis therefore presents the following stages of the work: - Analysis of coupled pseudo-interdigital resonators and lines; formulation of approximate transmission zero conditions and the investigation of coupling between these two resonators and related structures. - Development of compact, low loss and high selectivity microstrip pseudointerdigital bandpass filters. The design procedure of the filter consists of three simple steps, starting from the design of a parallel-coupled bandpass filter using the image parameter method applied to coupled microstrip lines. The development of compact microstrip diplexers composed of these filters uses the optimized common-transformer diplexing technique. An experimental verification of the developed filters and diplexers is made. - Investigation of the use of stepped impedance resonators (SIR) for the design of pseudo-interdigital bandpass filters with advanced characteristics. The design of compact dual-band filter using SIR. The investigation of possible improvement of the stopband of bandpass filters using bandstop generating structures. The application of SIR, defected ground structures (DGS), spur-lines, and opencircuited stubs in the design of compact bandpass filters with improved stopband. - The application of the proposed filters and diplexers in the design of integrated antenna filters and antenna diplexers. Improvement of performance of patch antennas, such as suppression of spurious harmonics of single-band antenna and improvement of bandwidth and selectivity of dual-band antenna, as a result of integration with filters. Separation of antennas’ bands and reduction of component count in integrated antenna diplexer

Microstrip three-port 4-channel multiplexers using dual-band bandpass filters for wireless applications

This paper presents a compact microstrip three-port 4-channel multiplexer using dual-band bandpass filters with good transmission and reflection characteristics on each channel. Proposed multiplexer configuration can be used for design of very compact multiplexer for broadband wireless applications using super compact microstrip pseudo-interdigital quasi-elliptical bandpass filters with or without stepped impedance resonators. The size of the proposed circuit is reduced. The improvement of the performance of multiplexer through introduction of additional transmission zeros is under investigation

Dual-band microstrip antenna filter for wireless communications

Integration of antenna and bandpass filter in one module is one of the ways to achieve miniaturisation and improved performance of microwave front ends. In dual or multiband systems the integration of multiband antennas with dual-band filter can be used for suppression of unwanted harmonics of antenna and improvement of reflection loss and selectivity of antenna. As most of modern systems use two or more frequency bands, for example WLAN standard IEEE 802.11 operating at 2.4-2.45 GHz and 5.15-5.85 GHz and WiMAX IEEE 802.16 standard operating at 2.3-2.7 GHz, 3.3-3.9 GHz and 5.15-5.85 GHz bands, the implementation of dual-band antenna integrated with band select filters becomes more practical solution then usage of diversity antenna. This approach, together with novel architecture of dual-band front end, was presented in [1]

An integrated antenna-filter with harmonic rejection

In this paper we present the possibility to integrate microstrip bandpass filter and patch antenna in order to suppress spurious harmonics of antenna. Compact microstrip pseudo-interdigital stepped impedance bandpass filter with improved stopband was designed. It was used to replace the microstrip line in inset microstrip-line fed patch antenna. As a result of integration full suppression of first two spurious harmonics of antenna was achieved

Compact microstrip pseudo-interdigital stepped impedance bandpass filters with improved stopband performance

In this paper we present design of a compact microstrip pseudo-interdigital stepped impedance bandpass filter with improved stopband performance. Stepped-impedance resonators are used to maximise the ratio between higher order and fundamental resonances. The improved stopband performance is realized using additional spur line and open-stub sections used for creation of transmission zeros. Total size of the filter is 30.1times7.2 mm. The stopband extension up to 5.7f0 has been achieved

Compact microstrip dual-band pseudo-interdigital stepped impedance bandpass filters for wireless applications

In this paper, the authors present a compact microstrip dual-band pseudo-interdigital bandpass filter structure with lambdag/4 stepped impedance resonators which can be used for development of dual-band filter with second passband centered at frequency from 2f0 to 3f0 .The proposed filter has advantages of simplicity and compactness

Microstrip antenna diplexers for wireless communications

In this paper we present a dual-band antenna integrated with diplexer. Compact microstrip diplexer was designed using pseudo-interdigital stepped impedance bandpass filters with improved stopband. Microstrip patch antenna designed to support dual-band operation at 2.5-2.6 GHz and 5.1-5.5 GHz frequency bands was integrated with diplexer. As a result of integration 20 dB separation of the channels has been achieved. The proposed system can be used in novel architectures for WiMAX RF front-end