Return loss

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

High-Directivity MEMS-Tunable Directional Couplers for 10–18-GHz Broadband Applications

Abstract: This paper reports on two novel concepts of area-efficient ultra-wideband microelectromechanical systems (MEMS) reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. Concept 1 is based on symmetrically changing the geometry of the ground coupling of each signal line, while Concept 2 is simultaneously varying both the ground coupling and the coupling between the two signal lines. This enables uniform and well predictable performance over a very large frequency range, in particular a constant coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity. For an implemented micromachined prototype 3-6-dB coupler based on Concept 1, the measured isolation is better than 16 dB, and the return loss and directivity are better than 10 dB over the entire bandwidth from 10 to 18 GHz. Concept 2 presents an even more significant improvement. For an implemented 10-20-dB prototype based on Concept 2, the measured isolation is better than 40 dB and the return loss is better than 15 dB over the entire bandwidth from 10 to 18 GHz for both states. The directivities for both states are better than 22 and 40 dB, respectively, over the whole frequency range. The measured data fits the simulation very well, except for higher through-port losses of the prototype devices. All devices have been implemented in a silicon-on-insulator RF MEMS fabrication process. Measured actuation voltages of the different actuators are lower than 35 V. Reliability tests were conducted up to 500 million cycles without device degradation.

Circularly Polarized Waveguide Antenna With Dual Pairs of Radiation Slots at Ka-Band

Abstract: In this letter, a circularly polarized (CP) waveguide antenna with dual pairs of slots is presented for Ka-band applications. Circular polarization is realized by combining two orthogonal linear polarizations, which are generated by two pairs of radiation slots on a cavity surface, respectively. Two approaches of radiation slots, i.e., edge slots and corner slots, are discussed. The corner slots approach is employed to design a CP waveguide antenna at Ka-band. The measured axial ratio (AR) is below 3 dB from 29.69 to 30.06 GHz, or 1.2% relative bandwidth, with a minimal value of 0.4 dB at 29.9 GHz. The measured antenna gain is 9.8 dBi at 30 GHz, and the return loss is below –13 dB within the 3 dB AR bandwidth. The all-metal structure of the proposed antenna is very appropriate for tough environment applications.

Microfluidically Reconfigurable Rectangular Waveguide Filter Using Liquid Metal Posts

Abstract: In this letter, the integration of microfluidically controlled liquid metal with WR42 rectangular waveguide to implement reconfigurable band-reject/band-pass filter is introduced. Here, microfluidic channels carrying liquid metal are used to realize off-centered adjustable partial/full-height circular posts at the dominant ${TE}_{10}$ mode. First, a liquid metal post is partially inserted into the waveguide to create a tunable transmission zero over a 2.9 GHz rejection tuning range (18.20 GHz to 21.10 GHz). Next, the band-reject element (partial-height post) is used in conjunction with another microfluidic metal post to design a reconfigurable 1-pole band-pass filter with a transmission zero in the stop-band. The filter is configured for two states. The measured insertion loss of the filter at $f_{0}$ is 2.3 dB and 2.8 dB while the return loss is better than 20 dB and 30 dB for State 1 and State 2 respectively.

CPW-fed ultra-wideband slot antenna with broadband dual circular polarization

Abstract: A novel coplanar waveguide (CPW) fed ultra-wideband slot antenna with broadband dual circular polarization is proposed, fabricated and measured. The antenna structure is simple and consists of two CPW-fed ports to achieve both right-hand circular polarization and left-hand circular polarization at the same frequency band with the overall size of 48 × 48 × 1 mm3. The design process of the proposed antenna is given and the circular polarization mechanism is analyzed from the surface current distribution. The variation of return loss, port isolation and axial ratio (AR) with antenna parameters is simulated. By optimizing the radiation patch and improving the ground plane, the ultra wide impedance bandwidth and broad axial ratio bandwidth are achieved. The measured impedance bandwidth is 153.1% (1.9–14.3 GHz) with return loss better than 10 dB, and the measured 3 dB axial ratio bandwidth is 102.6% (1.9–5.9 GHz). The gain and port isolation are better than 3 dB and 15 dB, respectively, within the AR band.

A Compact Wideband Antenna on Dielectric Material Substrate for K Band

Abstract: A wideband modified S shaped electrically small microstrip patch antenna on Aluminium tri-oxide ceramic substrate is designed and analyzed in this paper. The proposed microstrip line fed miniature patch antenna designed by using high frequency electromagnetic solver and the computed results are analyzed by using finite element method. It is observed from the obtained results that, 830 MHz bandwidth (Return loss <-10dB), 2dBi average gain, 97.33% of average efficiency are achieved in the operating frequency from 19.97 GHz to 20.80 GHz for K band satellite applications. Furthermore, the co-cross polarization of the radiation pattern and the current distribution for E-H field is analyzed. Ill. 6, bibl. 18, tabl. 1 (in English; abstracts in English and Lithuanian). DOI: http://dx.doi.org/10.5755/j01.eee.123.7.2378