A two‐pole tunable bandpass filter (BPF) which allows for the operational agility of both center frequency and bandwidth is proposed in this article. The fundamental structure is based on half mode substrate integrated waveguide (HMSIW) with different dimensions. Two sets of varactors placed at various nodes separately are utilized for adjusting center frequency and bandwidth over a wide tuning range. By adding a source‐load coupling path, two transmission zeros are produced on both sides of the passband to improve filter selectivity significantly. A second‐order 1.52–2.76 GHz filter with 3 dB constant bandwidth tuning from 240 to 350 MHz is developed, analyzed, simulated, and fabricated. Good agreement is obtained between simulated and experimental results.
This paper presents a novel dual-band (DB) dual-polarized (DP) shared aperture antenna with high isolation by using a combination of microstrip dipoles and dielectric resonator antennas (DRAs) for S and C bands, respectively. In the S band, two sets of proximity coupled stacked microstrip dipoles which crossed at the center are employed to achieve dual-linear polarization (DLP) and obtain desired bandwidth (BW), isolation, and pure polarization. The rectangle DRA with hybrid feed is selected as the C band element for its advantages of small base area and high isolation, and a 2 × 2 array is presented with the “pair-wise” anti-phase feed technique to achieve a low cross-polarized level. Moreover, benefited from the back feed scheme, the proposed antenna has a symmetrical structure and has the potential of expanding into a larger aperture. The proposed antenna has been manufactured and measured, and the results agree well with simulations, which prove the validity of the proposed design.
A 2‐pole fully tunable bandpass filter (BPF) with only two varactors implemented is proposed in this paper. The ultra‐wide center frequency (CF) tuning range is built on short‐ended stepped‐impedance resonators (SIRs). Two varactors are placed at the symmetrical plane of the filter in series and shunt configurations, according to the odd‐even mode analysis the CF and bandwidth (BW) of the passband can be tuned independently without adding any redundant tuning elements. The CF of the proposed filter can be tuned from 0.61 to 2.39 GHz. The 3 dB BW tuning range is 150‐260 MHz at the lower side and 290‐520 MHz at the upper side of the entire passband tuning range. Good agreement is observed between simulated and measured results.
In this paper, a high gain broadband low profile microstrip antenna with the dual-layered substrate and four parasitic metal elements is presented. The proposed microstrip antenna is mainly composed of four parts: four circular parasitic metal patches with dual arced breaches, a rectangular metal patch sandwiched between substrates, a square ground plane, and two-square substrates. The circular parasitic elements are the main radiation structure and determine the characteristics of the proposed antenna are closely related to the parasitic elements. The proposed antenna has been fabricated for experimental measurement. The reflection coefficient, radiation pattern, radiation efficiency, and gain have been studied in detail. The simulated and measured impedance bandwidth is 27.0% (3.30–4.33 GHz), the maximum realized peak gain reaches up to 6.52 dBi at the frequency of 3.65 GHz. The radiation pattern has a single peak which is perpendicular to the surface of the substrate. The proposed antenna is suitable to be applied in the 5G mobile or WiMAX wireless communication. Dual antenna with a pair of parasitic elements has been investigated numerically to explain the principle of the proposed antenna.
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