Tunable dual‐mode dual‐band filter with constant bandwidth and high selectivity

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A tunable dual-band filtering power divider with constant bandwidth and high selectivity is proposed, which incorporates a wideband power divider with two tunable dualband filters. The filter provides a tunable dual-mode dualband filtering response, and realizes a 908 phase shift to replace the middle quarter wavelength transmission line. As the bias voltage increases, the lower band increases from 1.1 to 1.5 GHz with a constant bandwidth of 40 MHz, while the higher band remains at 2.17 GHz with a fixed bandwidth of 60 MHz. During the wide tuning range, the return loss and isolation are always >15 dB, with a high selectivity due to multiple transmission zeros. K E Y W O R D S constant bandwidth, dual-band, filtering power divider (PD), high selectivity, tunable

Section: E S I G N O F T U N a B L E D U A L -B A N D F I L T E Rmentioning

confidence: 99%

Tunable dual‐band filtering power divider with constant bandwidth and high selectivity

et al. 2017

Self Cite

“…[1][2][3] Furthermore, with the development of wireless communication systems, the tunable filters with constant bandwidth are more attractive. [4][5][6][7][8][9][10][11] Generating multiple transmission zeros (TZs) is a good solution to sharpen the skirt and enhance the out of band rejection, which can improve the isolation between two tunable channels. The traditional methods of generating TZs are cross-coupling and source-load (S-L) coupling.…”

Section: Introductionmentioning

confidence: 99%

“…The electrically tunable microstrip passband filters (BPFs) have received increasingly great attention due to their compact size, reduced weight, and low cost . Furthermore, with the development of wireless communication systems, the tunable filters with constant bandwidth are more attractive . Generating multiple transmission zeros (TZs) is a good solution to sharpen the skirt and enhance the out of band rejection, which can improve the isolation between two tunable channels.…”

Section: Introductionmentioning

confidence: 99%

“…Especially for tunable filter with constant bandwidth, more coupling coefficients need to satisfy ideal case in tunable frequency range, so it is difficult to realize them because the electromagnetic field distribution of resonator will change with the coupling effect among resonators. In References , high selectivity was realized by the S‐L coupling and utilizing the characteristic of dual‐mode resonator or additional resonance circuit in the I/O structure. 10 In Reference , two TZs can be generated by the microstrip quarter wavelength with unequal widths is located as the ideal quarter‐wavelength coupled line.…”

Section: Introductionmentioning

confidence: 99%

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Compact high‐selectivity tunable dual‐mode filter with constant bandwidth by adopting frequency‐dependent S‐L coupling

Zhu

Xue

Sun

et al. 2019

A compact high‐selectivity tunable dual‐mode microstrip bandpass filter (BPF) with constant bandwidth is proposed in this letter. Three self‐adaptive transmission zeros (TZs) are generated due to the frequency‐dependent source‐load (S‐L) coupling and intrinsic characteristic of dual‐mode resonator, which can sharpen the skirt and deepen the upper stopband. The passband performance can be mainly determined by the pole separation Δf of dual‐mode and external quality factor Qe. Finally, a tunable filter with tuning range from 1.15 to 1.65GHz, constant 3 dB absolute bandwidth (ABW3dB) of 120 ± 5 MHz is designed and fabricated. The measurement results show good agreement with simulated ones, which confirms the design feasibility.

“…A tunable single‐band and dual‐band microstrip filter using varactors can realize continuously tuning center frequency via bias voltage . Although the plane structure is easy to integrate with lumped elements, it suffers from low quality factor and small power handing.…”

Section: Introductionmentioning

confidence: 99%

Compact tunable cavity filter with high selectivity using double‐layer suspended stripline resonator

Song

Xia

et al. 2019

Self Cite

A compact tunable cavity filter based on double‐layer suspended stripline resonator (DSSLR) is proposed. The DSSLR consists of a thin substrate suspended in an air‐filled cavity, a stepped impedance resonator loaded with interdigital capacitor on the top layer of the substrate, and a parallel‐plate capacitor series with a varactor at the bottom layer. The multiple capacitors not only achieve compact size by large capacitive loading, but also broaden the tuning range with a small capacitance variation of varactor. The internal coupling of two DSLLRs increases with the height of the inductive stub while decreases with the distance between two resonators. A fifth‐order wideband tunable cavity filter using a common bias voltage is designed, fabricated, and measured, which has a tunable frequency range of 67 MHz, constant bandwidth of 64 ± 7 MHz, low return loss of 15 dB, and high suppression of more than 40 dB.