Lower Passband Edge Research Articles

Miniaturized trisection BPF design using size-reduced substrate integrated coaxial resonators

The contribution of this work is to propose miniaturized trisection bandpass filters (BPFs) using size-reduced substrate integrated coaxial resonators (SICRs). The applied SICRs are operated under a coaxial mode. The occupied circuit area of the SICR developed from its structurally similar one, the substrate integrated waveguide (SIW) cavity, is only 6.2% that of the latter, corresponding to a circuit-area reduction rate of 93.8%. The cross-coupling between the input and output resonators can be either a magnetic or electric coupling for locating the transmission zero near either the upper or lower passband edge, respectively. Sample trisection BPFs with magnetic/electric cross-couplings are built for experimental verification. Agreements between measured and simulated data are observed. These miniaturized trisection BPFs with a freely switchable transmission zero are endowed with the advantage of an excellent circuit-area efficiency in the category of SICR and SIW cavity trisection BPFs.

Compact and low insertion loss UWB on‐chip bandpass filter using coupled meandered line

AbstractFor ultra‐wideband (UWB) communication applications, a low‐loss compact filter is proposed based on coupled lines using the GaAs integrated passive devices (IPD) technology in this letter. The multistage coupling lines are used to realize the ultra‐wide passband with 100% fractional bandwidth. Two modified stubs loaded with shorted capacitors are introduced between coupled lines to produce a new transmission zero near the lower passband edge, resulting in better frequency selectivity performance. Moreover, stepped impedance resonator (SIR) structure is applied to the coupled lines to improve impedance matching performance within ultra‐wide passband. As demonstrated, the proposed filter is fabricated as a chip with a compact size of 1.8 × 1.7 mm2, that is, 0.257 × 0.242 λg2. The measured results show that the insertion loss of the filter is less than 1.5 dB from 6 to 18 GHz with the return loss better than 13.5 dB. All simulated and measured frequency responses of the proposed filter are found to match well with each other, which further demonstrates the claimed superior performances of the proposed filter.

Synthesis Design of Equal-Ripple and Quasi-Elliptic Wideband BPFs With Independently Reconfigurable Lower Passband Edge

This paper presents a new synthesis design of equal-ripple and quasi-elliptic wideband band-pass filters (WB BPFs) with independently reconfigurable lower passband edge. The synthesis design starts from a 5th-order LC circuit. By using optimum multipole concept, a T-shaped resonator for the design of Chebyshev BPF without redundant elements can be directly derived, which is formed by a pair of parallel-coupled lines and short-ended stub. To sharpen the selectivity and maintain equal-ripple response, a pair of transmission zeros are introduced through replacing the short-ended stub by its multi-section counterparts. Thus, two prototypes, whose equivalent LC circuits can be directly derived, are presented for the synthesis of equal-ripple and quasi-elliptic BPFs. To realize the desired reconfigurable response, a capacitor is used. By controlling the capacitance value, the lower passband edge can be independently tunable in continue manners while the upper one is fixed. For validation, two prototypes with fixed and reconfigurable band-width are fabricated and measured. As the measured and simulated results agree well with each other, a high-efficiency design of reconfigurable-bandwidth WB BPFs is validated.

Broadband Filtering Magnetoelectronic Dipole Antenna With Quasi-Elliptic Gain Response

A filtering magnetoelectronic dipole antenna (MEDA) with quasi-elliptic gain response and wide operating band is investigated. Different from the conventional MEDA, the antenna studied here is fed by fork-shaped microstrip line aperture-coupled excitation. The intrinsic radiation null of the MEDA at the lower passband edge is utilized, and a mathematical model is first put forward to demonstrate its working mechanism. Four driven stubs connected to the shorted walls of MEDA are used to excite the planar dipole arms. The parasitic inductor and the coupling capacitor introduced by driven stubs form an equivalent low-pass filter network, leading to a radiation null at higher frequency. Furthermore, a third radiation null is generated by introducing two quarter-wavelength U-shaped shorted stubs to improve the out-of-band suppression. Besides, due to the introduction of multiple coupling structure, including the fork-shaped microstrip line coupling slot and driven stubs, a wide operating band can be realized while maintaining a low profile of 0.15 wavelength. The experimental results show that an impedance bandwidth of 53.5% (2.95-5.1 GHz) is achieved and an out-of-band suppression level higher than 17.9 dB is obtained. What is more, an average gain of 8 dBi and good radiation patterns are realized over the whole operating band.

Wideband reconfigurable bandpass filter using coupled lines loaded with varactor loaded stubs

In this article, a novel reconfigurable bandpass filter with tunable passband edge and bandwidth is proposed. The bandpass filter enables the two band edges independently adjustable to meet the needs of different systems. The wide tuning range of the bandwidth is achieved by controlling the tuning mechanism to altering not only the coupling strength of the coupled lines but also the transmission zeroes positions of the resonator. The lower passband edge can shifts from 760 to 840 MHz with the upper passband edge keeping still and the upper edge of the passbands from 981 to 1107 MHz with the lower edge keeping still. The overall tuning range of 3 dB fractional bandwidth is from 15.5% to 36%. The upper stopband attenuation of the fabricated structure can reach to 40 dB within a wide frequency range.

COMPACT INLINE TRIPLET SIW FILTER WITH EMBEDDED SHORT-ENDED MICROSTRIP LINE

A compact triplet inline substrate integrated waveguide (SIW) bandpass filter is presented with sharp lower skirt and deep lower-stopband performance. The filter is composed of two SIW rectangular cavities and an embedded short-ended strip line on the top surface of two adjacent SIW cavities. A transmission zero can be generated by the cross coupling near the lower passband edge, which allows the filter implementation in inline with sharp lower skirt. Deep lower stopband performance is inherited from SIW. To validate the concept, a filter prototype with fractional bandwidth (FBW) of 4% at 5.75 GHz is designed, fabricated and measured. Good agreement can be obtained between the measured and simulated results.

Compact Varactor-Tuned Microstrip High-Pass Filter With a Quasi-Elliptic Function Response

This paper presents a novel circuit topology of a tunable high-pass filter with a quasi-elliptic function response. A detailed theoretical analysis for the performance operating mechanism is demonstrated. With the assistance of mutually inductive coupling introduced, a pair of tunable transmission zeros (TZs) is synthesized at the lower passband edges and significantly improves the filter selectivity. Experiments are carried out by using the liquid crystal polymer bonded multilayer printed circuit board technology to validate the design. It is found that the implemented filter achieves a wide continuous tuning range covering from 1030 to 2150 MHz with low insertion loss, and which indeed are limited by the Schottky diodes used. It is also illustrated that two measured TZs are properly controlled at each tuning stage, which not only offers a sharp cutoff frequency response with a rejection level greater than 22 dB, but also provides an approximately unchanged response shape. Good agreement between the measured and simulated results can finally be observed.

Miniaturized band‐pass filter for broadband applications

AbstractThis article reports a new compact design of band‐pass filter for broadband applications. It has a compact design with two bended short stubs of quarter‐wavelength and a connecting stub of half‐wavelength, which result in the design of a broadband filter. The filter is fabricated on silicon substrate using surface micromachining process. The fractional bandwidth of band‐pass filter reported is around 0.9–4 GHz. The rejection at upper and lower pass band edge is greater than 35 dB, and the insertion loss is 2.4 dB. The area of the novel filter is (λg/4)2 at the centre frequency of the bandpass, whereas the area of the filter realized using the nonbending stubs and connecting lines is 2(λg/4)2 for the same band pass characteristics. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1372–1375, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25177

A novel microstrip UWB bandpass filter with CPW resonators

AbstractA new and compact ultra‐wideband (UWB) bandpass filter (BPF) using hybrid microstrip/coplanar waveguide (CPW) structure is proposed. The presented filter has been designed, fabricated, and measured for UWB system. Measured results demonstrated the UWB properties from 3.1 to 8.9 GHz (−3 dB bandwidth), which is fractional bandwidth of 96% at the center frequency 6.0 GHz. The filter also exhibits a sharper slop response at the lower passband edge than that reported in the article (Thomson and Hong, IEEE Microwave Wireless Compon Lett 17 (2007) 184–186), and deeper and wider stop‐band rejection than that reported in the article (Thomson and Hong, IEEE Microwave Wireless Compon Lett 17 (2007) 184–186; Li et al., IEEE MTT‐S Int Dig 2005, 675‐678) at the higher passband edge. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 24–26, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23977