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This paper presents the design of compact cross‐coupled microstrip trisection bandpass filters based on the hybrid structures of quarter‐wavelength (λ/4) and half‐wavelength (λ/2) resonators. The desired cross‐couplings for transmission zeros (TZs) are realized by parallel‐coupled transmission‐line sections (J‐inverter) or coupled via sections (K‐inverter) of λ/4 resonators. The main‐line couplings, on the other hand, are formed by mixed‐coupled λ/4 and λ/2 resonators. To validate the proposed hybrid configurations, two X‐band trisection filters with 6.5% and 6.2% fractional bandwidth were designed. The first filter generates a TZ below the passband, while the second one produces a TZ above the passband. Minimum insertion loss of 1.7 dB and 1.5 dB was observed for the two trisection filters, respectively, while the hybrid configurations caused significant size reduction in the overall filter size. Moreover, the first spurious response for the proposed filter topologies was pushed to 3fo, resulting in a wide stopband. [ABSTRACT FROM AUTHOR]

A practical implementation of a miniaturized crossover is presented using negative‐refractive‐index transmission‐line (NRI‐TL) metamaterial lines. NRI‐TL metamaterial theory has demonstrated that by loading a conventional transmission line with lumped LC elements, a large phase shift per‐unit‐length can be achieved. Employing this technique, the conventional microstrip transmission lines in a three‐section branch‐line coupler crossover are replaced with 90° NRI‐TL lines, and thus a compact NRI‐TL crossover with an area 47 times smaller than the area of its conventional counterpart is demonstrated. Measured results demonstrate that the proposed NRI‐TL metamaterial crossover exhibits a −10 dB |S11| bandwidth of 33% and a |3 dB| |S31| bandwidth of 26% around 1 GHz. [ABSTRACT FROM AUTHOR]

A novel wideband multilayer dual‐podal Vivaldi antenna with broadband characteristics from 5.5 to 20.82 GHz, is presented. Contrary to traditional Vivaldi antennas that are antipodal‐based, this design is realised by placing a pair of podal Vivaldi antennas with corrugated slots on the top and bottom of a substrate stack (consisting of two dielectric layers) using a Bondply. The pair is fed in‐phase with the help of a Strip‐Line (SL) transmission section that is terminated on a radial stub to couple capacitively to the antenna elements. With this technique of electrically coupling a podal Vivaldi pair, improved performance parameters are achieved, specifically: a measured maximum gain of 9.33 dBi, Half Power Beam Width of 126.5° in the H‐plane, and a maximum Front‐to‐Back (F/B) ratio of 14.36 dB with an overall antenna size of 29 × 21 × 1.63 mm. The in‐depth understanding of the working mechanism is supported by a detailed parametric analysis, current distribution, and a clear physical insight into the operating principles. Moreover, a 1 × 4 Vivaldi antenna array is also designed and analysed. A measured maximum gain of the 13 dBi at 15 GHz in the array is achieved along with the wide bandwidth of 6.3 GHz from 10.78 to 17.07 GHz. The array is fed through an SL corporate feed network that ensures in‐phase excitation of all four Vivaldi pairs. A Grounded Co‐planar Waveguide to SL transition is adopted for connecting the 2.92 mm Radio Frequency launcher on the top layer. The very compact geometry of the proposed structure enables its integration into the systems for remote sensing applications. [ABSTRACT FROM AUTHOR]

In this study, an ultra-wideband (UWB) monopole antenna with a dynamically reconfigurable notch band, along with the associated RF-triggered power management unit (PMU) that enables the dynamic reconfigurability, are presented. The UWB monopole antenna has a rectangular slot which hosts a J-shaped stub, electrically connected with the radiator using one PIN diode switch. When the diode is OFF, the monopole antenna has a UWB characteristic, while when it is turned ON a frequency notch is created at 5.6 GHz. The diode is fed from a PMU that consists of a rectenna and a DC-to-DC active booster. When the rectenna that consists of a patch antenna and a rectifier receives a -11 dBm or higher 5.6 GHz signal, it rectifies the RF signal into a sufficiently high DC voltage. The rectified DC voltage is applied to the cascaded DC-to-DC booster as enabling signal, and the booster provides at its output terminal sufficient DC power to actuate the PIN diode and thus dynamically reconfigure the UWB antenna. The dynamically reconfigurable notch band is created immediately in response to the reception of an external, -11 dBm RF signal at 5.6 GHz, and it disappears in real time immediately after the external RF signal is removed. [ABSTRACT FROM AUTHOR]

In this letter, a compact, wideband bandpass filter with 31% 3-dB bandwidth, with very sharp roll-off characteristics, low insertion loss of 0.45 dB, high return loss greater than 25 dB, and improved out-of-band performance, suitable for 2.4 GHz WLAN applications is presented. The developed prototype filter is based on a quadruple-mode square ring resonator, connected to two λg/2 short-circuited stubs. In order to improve the out-of-band performance and achieve a wider stopband response, two Γ-shaped band-stop sections are connected on the feeding lines without disturbing the geometric symmetry along the diagonal. Measurements of the fabricated prototype provide experimental verification of the theoretical and simulated behaviour of the proposed filter. [ABSTRACT FROM AUTHOR]