Return loss

About: Return loss is a research topic. Over the lifetime, 11090 publications have been published within this topic receiving 97603 citations.

Design and Measurement of Self-Matched Dual-Frequency Coplanar Waveguide-Fed-Slot Antennas

Abstract: Two new designs of dual frequency coplanar waveguide (CPW)-fed double folded slot antennas are presented. An important advantage of these antennas is that they are self-matched to the feeding CPW without the need for external matching circuit. This reduces the antenna size and simplifies its design. To verify the designs, the return loss and radiation patterns are measured and compared to those obtained using available commercial software with good agreement

Dual-band sub-harmonic quadrature mixer using composite right/left-handed transmission lines

Abstract: A dual-band (DB) sub-harmonic quadrature mixer using composite right/left-handed (CRLH) transmission lines (TL) is presented. The CRLH-TLs are used to provide dual-bandwidth operation in the Wilkinson power dividers (WPDs), the ±45° delay line for in-phase/quadrature generation, and the sub-harmonically pumped mixers. Theory and implementation of the RF/LO DB-WPDs, the dual-passband dual-stopband (DPDS) shunt terminations, and the DB sub-harmonically pumped mixers (SHPMs) are presented. These DB microwave components for the DB quadrature mixer are detailed in individual sections with both simulated and measured performances. The DB-WPDs exhibit S21 and S31 larger than −3.95 dB, return losses larger than 12 dB, isolations larger than 16 dB, phase imbalance less than 2.15°, and gain imbalance less than 0.25 dB at each passband. The DPDS terminations demonstrate insertion loss larger than 16 dB at stopbands and less than 2.3 dB at passbands. The DB-SHPM shows 10 dB and 11.7 dB conversion loss in low- and high-frequency mixing schemes with good linearity. Local oscillator (LO) to radio frequency (RF) isolation larger than 30 dB is also measured in both frequency mixing schemes. The measured results of the DB quadrature mixer display output amplitude balance, orthogonal characteristic, and LO to RF isolation larger than 45 dB.

A Method for Determining Optimal EBG Reflection Phase for Low Profile Dipole Antennas

Abstract: An analytical method for determining the optimal reflection phase of an electromagnetic band gap (EBG) ground plane to match a low profile dipole antenna is introduced. Image theory is used to incorporate the near field coupling between a dipole antenna and the ground plane. The main contribution of this paper is to show that the optimal EBG reflection phase can be determined at discrete frequencies where a theoretically perfect return loss occurs. The optimal reflection phase is then obtained over a wider frequency band of interest and is related to the antenna's return loss for a given feed impedance and antenna height above the EBG. The resulting reflection phase can be used as a reference for designing an EBG ground plane that is well matched to the antenna without time consuming iterative full wave numerical simulations. Numerical modeling results are compared to the optimal return loss derived from the analytical method to validate the design process. It is also shown that, for certain antennas, vias are not always necessary in the construction of the EBG, which eases the manufacturing process. Finally, a dipole and EBG are constructed using the optimal design method and measurements are compared to the simulations.

Improvement of the on-body performance of a dual-band textile antenna using an EBG structure

Abstract: A new dual-band wearable textile antenna designed for body-centric communications is introduced. The antenna is fully characterized in free space and on the body model, with and without an electromagnetic band gap (EBG) substrate. The band gap array consists of 3 × 3 elements and is used to reduce the interaction with human tissues. With the EBG back reflector, the radiation into the body is reduced by more than 15 dB. Increases of 5.2 dB and 3 dB gain are noticed at 2.45 GHz and 5.5 GHz, respectively. The results are presented for the return loss, radiation pattern, efficiency, and specific absorption rate (SAR).

Development of a Broadband Coplanar Waveguide-to-Microstrip Transition With Vias

Abstract: A transition from coplanar waveguide (CPW)-to-microstrip with vias is often used in wafer-probe measurements. This paper shows how field and impedance matching are used to develop a wideband transition. This paper demonstrates how the presence and placement of the vias affect the bandwidth and alters the impedance of the transition. The measured results on a transition show that a wideband transition with return loss better than 10 dB and an insertion loss less than 1.5 dB up to 36.64 GHz is obtained. The measurements show excellent agreement with simulation. The work presented in this paper provides a better understanding about a CPW-to-microstrip transition with vias as well as design procedures and principles that can be utilized to facilitate the realization of a broadband CPW-to-microstrip transition with vias.