Return loss

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

Linearly polarized radial-line slot-array antennas with improved return-loss performance

Abstract: The standard linearly polarized radial-line slot-array (RLSA) antenna exhibits poor return loss as seen by its coaxial feed. This paper describes techniques that improve the poor return-loss performance of this antenna, by using two interchangeable methods: i) reflection-canceling slots on the front and back surface of the antenna, and ii) beam squinting. A series of 550 mm diameter linearly polarized Ku-band prototype antennas were constructed to experimentally investigate the efficiency of each of these methods. In order to cut experimental costs, initial radiation-pattern modeling was performed theoretically, and then prototypes were developed using inexpensive aluminum foil. Measurements of the developed prototypes indicated that both the reflection-canceling and beam-squinting methods provided a substantial improvement in return loss over the desired frequency band.

Modeling, Design and Characterization of a Very Wideband Slot Antenna With Reconfigurable Band Rejection

Abstract: An antenna exhibiting a very wide bandwidth with reconfigurable rejection within the band is presented. The proposed topology is versatile in terms of the number of available antenna states and location of the rejection frequencies, and also allows the operation of the antenna in an “all-pass” state. First, a physical interpretation of the rejection mechanism and its corresponding circuit model are presented and validated. The proposed antenna concept is then demonstrated on a 4-state slot bow-tie antenna operating from 1.5 to 5 GHz with various rejection frequencies. PIN diodes are used as switching elements, with particular care taken to minimize power consumption. Simulated and measured return loss, radiation patterns and gain of the fully operational antenna are presented. Finally, we characterize and discuss the overall efficiency-considered here as the most relevant parameter to characterize the antenna filtering performance-both theoretically and experimentally, thereby highlighting the benefit of the proposed topology.

Design of Compact 4 × 4 UWB-MIMO Antenna with WLAN Band Rejection

Abstract: A compact 4 × 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm × 60 mm), printed on a FR4_epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36–6.34 GHz while the values of all isolation coefficients are below −15 dB and the correlation coefficient of MIMO antenna is less than −28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context.

Isolation Improvement of MIMO Antenna Using a Novel Flower Shaped Metamaterial Absorber at 5.5 GHz WiMAX Band

Abstract: This brief demonstrates the use of metamaterial absorber (MA) to achieve high isolation between two patch antennas in a 2-element multiple-input–multiple-output (MIMO) system operating at 5.5 GHz resonant frequency useful for WiMAX application. The proposed flower shaped MA, designed on a $9\times 9$ mm2 FR-4 substrate with 1 mm thickness, exhibits near unity normalized impedance at 5.5 GHz with an absorptivity of 98.7%. A four element array of the MA is arranged in the form of a line in the middle of the two radiating patches in order to suppress the propagation of surface current between them at the operating frequency. Using the proposed flower shaped MA, an isolation of nearly 35 dB is achieved. The MIMO structure is studied in terms of return loss, isolation, overall gain, radiation pattern, envelope correlation coefficient (ECC), diversity gain (DG), total active reflection co-efficient (TARC), etc. The structure is finally fabricated and measured to show good agreement with the simulated results.

Design of a Single-Feed Dual-Band Dual-Polarized Printed Microstrip Antenna Using a Boolean Particle Swarm Optimization

Abstract: A novel dual-frequency dual-linear-polarization printed antenna element benefiting from a single-feed single-layer structure is introduced in this paper. The Boolean particle swarm optimization algorithm in conjunction with the method of moments (MoM) is employed to optimize the geometry of the antenna after considering three objectives: cross polarization, return loss, and boresight direction in both bands. A fuzzy-logic based ordered weighted averaging operator allows us to efficiently implement the multi-objective optimization technique. Prototypes of the optimized designs have been fabricated and tested. The measured results show excellent performance with more than 15 dB of return loss and 10 dB of cross polarization in both frequency bands of operation, i.e., 12 and 14 GHz. A gain of 4.8 dBi has been measured for both frequency bands.