This study presents new techniques for implementing continuous-time second-order band-pass filters with high-quality factors and asymmetric slopes. The techniques are centred around the realisation of two non-conventional transfer functions which include the non-integer-order Laplacian operator sα; 0<α<1. Four main possible circuit realisations; one based on a frequency-dependent negative resistor (FDNR), another based on an inductor and two based on multiple amplifier biquads (MABs) are given and verified using Spice and experimentally for both transfer functions. In addition, a field programmable analogue array (FPAA) realisation is tested and verified. Last but not least, a possible realisation using current conveyors is also given, tested and verified.

High-quality factor asymmetric-slope band-pass filters: A fractional-order capacitor approach

Miniaturized microstrip filters using quarter-wave or quasi-quarter-wave resonators with cross-coupling are presented. The quarter-wavelength resonators enable very compact positively or negatively cross-coupled filters to be realized. The combination of quarter-wave and quasi-quarter-wave resonators facilitates the cross-coupling with a proper coupling phase. A new explanation for the coupling phase between the main-coupling and cross-coupling paths is proposed. Different filters that use the proposed resonators are realized and may have either quasi-elliptical or flat group-delay responses. Measurement results correlate well with theoretical predictions.

https://ir.nctu.edu.tw:443/bitstream/11536/28178/1/000180296200014.pdf

Miniaturized microstrip cross-coupled filters using quarter-wave or quasi-quarter-wave resonators

A network prototype suitable for reconfigurable filters with imaginary-axis transmission zeros is presented. The prototype is synthesized using classical cascade synthesis. Reconfiguration of the transmission zeros is implemented entirely by tunable capacitors. The measured performance of a narrow-band reconfigurable bandpass filter realized in a planar combline using varactor diodes demonstrates the principle.

A reconfigurable bandpass filter for RF/microwave multifunctional systems

Substrate integrated waveguide (SIW) technology provides an effective solution for the low-cost and high-performance interconnect and packaging of microwave and millimeter wave systems. In this paper, Ka-band four-degree bandpass filters having asymmetric frequency response, which are required in the design of transmit and receive diplexers for high rejection between neighboring channels, are proposed and realized on an SIW platform. The filters are self-packaged due to the fact that a conductor-backed coplanar waveguide is used to directly excite the filters. Higher-order resonant mode is used to achieve the required negative coupling on the basis of a single-layer SIW. The proposed filters, having the same center frequency of 35 GHz and pass bandwidth of 1.3 GHz, are fabricated on a conventional Rogers RT/Duroid 6002 substrate with thickness of 0.508 mm by using a low-cost printed circuit board process. Measured results of those filters, which exhibit high single-sided selectivity and minimum in-band insertion loss of about 1.25 dB, agree well with simulated results.

Self-Packaged Millimeter-Wave Substrate Integrated Waveguide Filter With Asymmetric Frequency Response

A low-temperature cofired-ceramic (LTCC) multilayer-ceramic (MLC) duplexer is presented in this paper. The duplexer is designed for a DCS-1800 handset. It is constructed using a multilayer laminated bandpass filter and a multilayer laminated bandstop filter. These two filters are capable of easy tuning after duplexer manufacture. The computer-aided design flowchart is also presented. Additionally, the tuning method and loss improvements of the duplexer are discussed. Measured results show the performance of the LTCC-MLC duplexer is acceptable for DCS-1800 applications.

LTCC-MLC duplexer for DCS-1800

A method for increasing the skirt selectivity on one side of a bandpass filter is presented. One such application is the receive filter of a personal communication network (PCN) mobile terminal. An asymmetric synthesis method has been used, realizing finite transmission zeros as cross couplings. A novel microstrip structure has been devised to demonstrate the electrical design. Although the insertion loss measured was greater than that required for a practical system, the procedure is applicable to compact dielectric resonator structures with potentially lower loss capability. >

Asymmetric bandpass filter using a novel microstrip circuit

A ceramic bandpass filter with increased selectivity on the lower side of the passband is presented. One application is the receive filter of a mobile radio transceiver operating in the 1.8-GHz bands. Finite transmission zeros have been introduced by using a network with additional cross couplings. The circuit was constructed with four coaxial ceramic resonators capacitively coupled using a microstrip PCB. For a 75-MHz passband filter, a stopband attenuation of 37 dB was attained at 20-MHz offset from the passband. A midband insertion loss of 1.2 dB and bandedge loss of 3 dB were achieved. >

P.L. Field

Papers

Asymmetric bandpass filter using a novel microstrip circuit

Asymmetric bandpass filter using a ceramic structure