Compact Wideband Coplanar Stripline-to-Microstrip Line Transition Using a Bended Structure on a Two-Layered Substrate

A design of a compact coplanar strip (CPS)-to-microstrip line (MSL) transition using a bended structure on a two-layered substrate is presented. The proposed transition consists of a CPS taper and a bended CPS-to-MSL transition on a two-layered substrate. The CPS taper is formed on the lower substrate with low permittivity (εr = 3.38), and the bended CPS-to-MSL transition is formed on the upper substrate with high permittivity (εr= 10.2). The proposed transition is designed with analytical formulas obtained by applying EM-based conformal mapping without parametric tuning trials. The conductor shape of the bended CPS-to-MSL transition is adjusted to form an optimal Klopfenstein impedance taper. The proposed CPS-to-MSL transition optimally connects between a high impedance CPS line (~160 Ω) and a 50 Ω MSL, which typically results in a long transition length for ultra-wideband performance. The implemented transition bended in a sinusoid shape on the two-layered substrate provides good performance from 2 GHz to 17 GHz with the maximum 2 dB insertion loss per transition, and the horizontal length of the bended transition is reduced to 42.9% of the straight transition length. This bended transition is developed for use in mm-wave balanced antenna/detector feeds but can be applied to a variety of wideband balanced circuit modules, where compact circuit size is critical.

A Comprehensive Review of Different Feeding Techniques for Quasi Yagi Antenna

Yagi Uda antenna is a directional antenna but has limited bandwidth. To improve the bandwidth, various Quasi Yagi antennas can be designed by using different feeding techniques and different element shapes. In this paper, three different types of feeding techniques are reviewed i.e. microstrip-to-coplanar stripline transition (MS-to-CPS), coplanar waveguide feed (CPW) and Tapereded balun, which convert unbalance input to balance output. From the study it is found that MS- to- CPS transition provides higher bandwidth at the cost of low gain and lower frontto-back ratio. CPW is simple feed structure having compact size but lower gain. Tapered balun provides higher bandwidth but requires larger size.

Ultra-Wideband Trapezoidal Log-Periodic Antenna Integrated with an Elliptical Lens

The design and implementation of an ultra-wideband trapezoidal log-periodic antenna (LPA) integrated with an elliptical dielectric lens are presented. The proposed LPA is fed by an ultra-wideband microstrip-to-coplanar stripline transition structure. In order to improve the radiation patterns and to increase the antenna gain, an elliptical dielectric lens is mounted on the top of the LPA radiator. The design parameters of the elliptical lens integrated with the LPA were optimized through a parametric analysis. The proposed antenna shows an impedance bandwidth (S11 ≤ −10 dB) from 5.2 to 40 GHz, with a peak gain of 17.8 dB.

Coplanar Stripline-Fed Wideband Yagi Dipole Antenna with Filtering-Radiating Performance

In this article, a wideband filtering-radiating Yagi dipole antenna with the coplanar stripline (CPS) excitation form is investigated, designed, and fabricated. By introducing an open-circuited half-wavelength resonator between the CPS structure and dipole, the gain selectivity has been improved and the operating bandwidth is simultaneously enhanced. Then, the intrinsic filtering-radiating performance of Yagi antenna is studied. By implementing a reflector on initial structure, it is observed that two radiation nulls appear at both lower and upper gain passband edges, respectively. Moreover, in order to improve the selectivity in the upper stopband, a pair of U-shaped resonators are employed and coupled to CPS directly. As such, the antenna design is finally completed with expected characteristics. To verify the feasibility of the proposed scheme, a filtering Yagi antenna prototype with a wide bandwidth covering from 3.64 GHz to 4.38 GHz is designed, fabricated, and measured. Both simulated and measured results are found to be in good agreement, thus demonstrating that the presented antenna has the performances of high frequency selectivity and stable in-band gain.