Parallel-coupled Line Section Research Articles

A Novel Ring Type Wideband Bandpass Filter: Proposal, Design, and Verification

In this brief, a novel ring type wideband bandpass filter with multi-reflection zeros (RZs) is presented. The proposed topology consists of two signal electrical paths between two output ports, where there are three <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> /4 parallel-coupled line sections to be cascaded in each path. By using the proposed approach, 7 equal-ripple performance with adjustable group delay can be realized in the passband. Considering further simplification in design, several parallel-coupled line sections can be substituted by TLs, thus attaining 5 simplified topologies with the same filtering response. Compared with the former works, the proposed work not only provides 8 RZs in the realized passband with equal-ripple and controllable group delay, but also achieves simple circuit and easy fabrication. For verification, one prototype circuit is in final fabricated, and the measured frequency response have well verified the proposed design approach.

A COUPLED-LINE BAND-STOP FILTER WITH THREE-SECTION TRANSMISSION-LINE STUBS AND WIDE UPPER PASS-BAND PERFORMANCE

A novel band-stop fllter with wide upper pass-band performance is proposed and discussed in this paper. This band- stop fllter includes two three-section transmission-line stubs and a parallel coupled-line section. Because three-section transmission-line stubs and coupled-line section are used, this fllter not only features good band-stop flltering property, but also has wide upper pass band. In order to verify this new fllter circuit structure and its corresponding design theory, three groups of numerical examples are demonstrated. Finally, two practical band-stop fllters using common microstrip technology are designed, simulated and measured. The simulated and measured results indicate that both the coupled-line section with weak coupling and two three-section stubs can improve the upper pass-band performance. Furthermore, the measured results of the second fabricated microstrip band-stop fllter (Filter B) show that the 20-dB insertion-loss band-stop bandwidth at 0.46GHz is 90MHz and the 1.2-dB transmission coe-cient upper pass band is from 0.66GHz to 2.52GHz. Thus, the highest pass-band frequency is extended to larger than flve times of the operating center frequency of stop band.

Sharp-rejection microstrip bandpass filters with multiple transmission zeros

A simple design of a sharp-rejection microstrip bandpass (BPF) filter is presented. By creating multiple transmission zeros in the lower and upper stopbands, sharp rejection characteristics are obtained. The basic filter unit consists of a single parallel coupled-line section and an open-ended stub. A lossless transmission line model approach is used to derive the design equations for frequency responses and transmission zero positions. The bandwidths are controllable by the zero locations that in turn are controlled by varying the impedances of the configuration. To validate theoretical predictions, two prototype BPFs operating at lower band 2.4 GHz of WLAN are fabricated in microstrip form.

K-인버터를 이용한 직접 결합 급전 구조를 갖는 대역 통과 필터

This paper proposed the novel method that can realize the parallel coupled line(PCL) band-pass filter with directly coupled feeding structure by means of transforming the first and last PCL sections of the conventional PCL band-pass filter into K-inverters, then substituting T-type equivalence for K-inverter. The proposed method supplies simple design formulae and can considerably reduce time and efforts needed to optimize filter performance when compared to reported methods using external Q or equivalent parameters. On the basis of the proposed method, the band-pass filter using directly coupled feeding structure and having 18% fractional bandwidth was designed and fabricated. The validity of proposed method was proven by the measured result.

Microstrip directional coupler with nearly ideal TEM coupler performance

A meandered parallel coupled-line structure is proposed to achieve high directivity within a wide bandwidth. By properly increasing the meandered parallel coupled-line sections, the high-directivity bandwidth becomes much wider. An example coupler is fabricated to verify the theory. More than 50 dB of isolation is achieved over a bandwidth of zero to twice centre frequency.