T-shaped Transmission Line Research Articles

A compact all-frequency absorptive dual-band bandpass filter with T-shaped transmission line absorption branches

Multi-band and all-band absorptive filters can greatly promote the miniaturization of radio frequency (RF) communication systems. However, the existing absorptive multi-band filters have problems such as large size, narrow passband, high insertion loss, and low RF signal absorption capacity. Herein, a new all-frequency absorptive dual-band bandpass filter (BPF) is proposed by combining an N-shaped microstrip coupler with T-shaped transmission line absorption branches. The N-shaped microstrip coupler can flexibly implement the dual-band bandpass filtering of RF radio frequency (RF) signals in a compact structure. The T-shaped transmission lines can effectively absorb the stopband signals reflected from the N-shaped coupler at full frequency. The theoretical and experimental results show that the 3-dB fractional bandwidths (FBWs) of the proposed BPF with a size of 0.41 λg × 0.20 λg are 60.5 % at 1.3 GHz and 13.3 % at 4.1 GHz, respectively, and the return losses in all frequency are greater than 10 dB, indicating that the filter has the characteristics of wide passband, small size, and all-frequency absorption of reflected bandstop signals. In short, the combination of N-shaped coupler and T-shaped transmission line provides a way to achieve an all-frequency absorptive dual-band BPF with a small size, wide passband and low return loss.

T-Shaped Transmission Line Fault Location Based on Phase-Angle Jump燙hecking

In order to effectively solve the dead-zone and low-precision of T-shaped transmission line fault location, a new T-shaped transmission line fault location algorithm based on phase-angle jump checking is proposed in this paper. Firstly, the 3-terminal synchronous fundamental positive sequence voltage and current phasors are extracted and substituted into the fault branch distance function to realize the selection of fault branch when the fault occurs; Secondly, use the condition of the fundamental positive sequence voltage phasor at the fault point is equal to calculate all roots (including real root and virtual roots); Finally, the phase-angle jump check function is used for checking calculation, and then the only real root can be determined as the actual fault distance, thereby achieving the purpose of high-precision fault location. MATLAB simulation results show that the proposed new algorithm is feasible and effective with high fault location accuracy and good versatility.

Design of a Triple-Mode Bandpass Filter Using a Closed Loop Resonator

In this study, a novel third-order bandpass filter, which is based on a rectangular closed loop resonator, is presented. By adding a series resonator to the conventional loop resonator, the resonator's even resonant mode is split into two modes, while the odd resonant mode is not affected. Therefore, by varying the values of the series resonator elements, the resonant frequencies of two even modes can be determined independent of the odd-mode resonant frequency. In the proposed triple-mode filter design, instead of using a lumped series resonator, a T-shaped transmission line is coupled to the resonator via a small gap. To verify the design method, a filter is designed at 2.4 GHz with a bandwidth of 100 MHz. The improved performances of the proposed triple-mode filter are compared with those of the conventional dual mode filter.

Miniaturised quadrature hybrid coupler using modified T‐shaped transmission line for wide‐range harmonic suppression

In this study, a novel modified T-shaped transmission line, comprised of a transmission line centre tapped with open stub and parallel open stubs is proposed to reduce the size and suppress the unwanted harmonics of branch line coupler (BLC), to a great extent. The low impedance open-stub limitation of traditional T-shaped unit is rectified by the proposed unit for extended harmonic suppression of BLC. Besides, the 35.35 and 50 Ω quarter wavelength transmission lines of the BLC are reduced to 39.6° and 37.8°, respectively. Lossless transmission line model analysis is used to derive the design equations and graphs. To validate the proposed approach, a prototype operating at 0.9 GHz is fabricated. The proposed BLC size is 74% smaller than the conventional one and exhibits a wide-range harmonic suppression of up to at least eighth harmonic.

A novel two section branch line coupler employing different transmission line techniques

In this paper, a 3dB wideband branch line coupler with reduced size and harmonic suppression is presented. New multiple asymmetric π-shaped, cross and T-shaped transmission line techniques are used to reduce the physical size of the coupler. At the operating frequency of f0=0.9GHz, the fabricated coupler achieves 15dB return loss bandwidth of 44.4% with a size reduction of 76.3%. The designed coupler has insertion loss better than 3.6dB with a magnitude balance of 0±1dB over the frequency band 0.67–1.05GHz. In addition to compact design, the unwanted harmonics are well suppressed up to 4f0 with a level better than 20dB by maintaining good agreement between the measured results and theoretical predictions.

Novel compact dual-narrow/wideband branch-line couplers using T-Shaped stepped-impedance-stub lines

This article presents a compact model to reduce the physical size and increase the frequency ratio between the second and first resonance frequencies of a dual-function stepped-impedance-stub (SIS) line, which was subsequently employed in the realization of dual-band branch-line couplers. The proposed model comprises of a loaded spiral T-shaped SIS that reduces the size of a conventional SIS line as well as improving its frequency ratio. The proposed model behaves exactly similar to the recently developed dual-band resonators with the advantage of size reduction of ∼35% as well as having a wide range of realizable frequency ratios between 1.4 and 3.7 compared to 1.7–2.7 and 1.8–2.3 for the conventional SIS and T-shaped transmission-lines, respectively. Dual-narrowband and wideband branch-line couplers were developed based on the spiral T-shaped SIS lines. The dual-wideband device's bandwidth was enhanced by 2.7% accompanied by a size reduction of 58.6% in comparison with the conventional dual-wideband couplers operating at the same frequencies. The theoretical results were verified by measurement. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.