Return loss

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

A New Ultra-wideband Microstrip-to-CPS Transition

Abstract: A novel ultra-wideband microstrip-to-CPS (coplanar stripline) transition has been developed. The transition is designed to provide the field and impedance matching between adjacent transmission lines. The proposed design is applicable to substrates with any dielectric constant. The transition provides the balun role as well as the impedance transformation. The fabricated transition in back-to-back configuration provides the insertion loss less than 1 dB per transition and the return loss better than 10 dB for frequencies from 5.39 GHz to over 40 GHz. In addition, a simulation study indicates that this transition can possess a 3 dB bandwidth of ~ 100 GHz.

A Compact Wideband Microstrip Crossover

Abstract: In this letter, a planar microstrip crossover junction is presented. The conductor-backed coplanar waveguide (CB-CPW) structure with vias is employed as the core part of the crossover design. The dimensions of the CB-CPW crossover itself are 11.3 × 11.3 mm2. Two kinds of the transitions between the microstrip line (MSL) and the CB-CPW structure are merged into a double side print circuit board. This presented crossover junction has a bandwidth from 10 up to 6000 MHz for 20 dB return loss, 1 dB insertion loss and -20 dB isolation. Compared with the other designs, this planar crossover features wide bandwidth and compact configuration.

A Planar Electronically Steerable Patch Array Using Tunable PRI/NRI Phase Shifters

Abstract: This paper presents a planar electronically steerable series-fed patch array for 2.4-GHz industrial, scientific, and medical band applications. The proposed steerable array uses 0deg tunable positive/negative-refractive-index (PRI/NRI) phase shifters to center its radiation about the broadside direction and allow scanning in both directions off the broadside. Using the PRI/NRI phase shifters also minimizes the squinting of the main beam across the operating bandwidth. The tunable PRI/NRI phase shifters employ 0.13-mum CMOS tunable active inductors, as well as varactors in order to extend their phase tuning range and maintain a low return loss across the entire phase tuning range. The feed network of the proposed array uses lambda/4 impedance transformers. This allows using identical interstage phase shifters, which share the same control voltages to tune all stages. Furthermore, using the impedance transformers in combination with the CMOS-based constant-impedance PRI/NRI phase shifters guarantees a low return loss for the antenna array across its entire scan angle range. The antenna array was fabricated, and is capable of continuously steering its main beam from -27deg to +22deg off the broadside direction with a gain of 8.4 dBi at 2.4 GHz. This is achieved by changing the varactors' control voltage from 3.5 to 15 V. Across the entire scan angle range, the array return loss is less than -10 dB across a bandwidth of 70 MHz, and the relative sidelobe level is always less than -10 dB. Furthermore, the proposed design achieves very low beam squinting of 1.3deg/100 MHz at broadside and a 1-dB compression point of 4.5 dBm.

Through-glass copper via using the glass reflow and seedless electroplating processes for wafer-level RF MEMS packaging

Abstract: We present a novel method for the fabrication of void-free copper-filled through-glass-vias (TGVs), and their application to the wafer-level radio frequency microelectromechanical systems (RF MEMS) packaging scheme. By using the glass reflow process with a patterned silicon mold, a vertical TGV with smooth sidewall and fine pitch could be achieved. Bottom-up void-free filling of the TGV is successfully demonstrated through the seedless copper electroplating process. In addition, the proposed process allows wafer-level packaging with glass cap encapsulation using the anodic bonding process, since the reflowed glass interposer is only formed in the device area surrounded with silicon substrate. A simple coplanar waveguide (CPW) line was employed as the packaged device to evaluate the electrical characteristics and thermo-mechanical reliability of the proposed packaging structure. The fabricated packaging structure showed a low insertion loss of 0.116 dB and a high return loss of 35.537 dB at 20 GHz, which were measured through the whole electrical path, including the CPW line, TGVs and contact pads. An insertion loss lower than 0.1 dB and a return loss higher than 30 dB could be achieved at frequencies of up to 15 GHz, and the resistance of the single copper via was measured to be 36 mΩ. Furthermore, the thermo-mechanical reliability of the proposed packaging structure was also verified through thermal shock and pressure cooker test.

Printed and Integrated CMOS Positive/Negative Refractive-Index Phase Shifters Using Tunable Active Inductors

Abstract: This paper presents a printed and an integrated bi-directional tunable positive/negative refractive-index phase shifter utilizing CMOS tunable active inductors (TAIs). The printed phase shifter is comprised of a microstrip transmission line (TL), loaded with series varactors and a shunt monolithic microwave integrated circuit (MMIC) synthesizing the TAI. Using the TAI extends the phase tuning range and results in a low return loss across the entire tuning range. The integrated circuit (IC) phase shifter replaces the TLs with suitable lumped L-C sections. This enables integrating the entire phase shifter on a single MMIC, resulting in a compact implementation. The TAI used for both phase shifters is based on a modified gyrator-C architecture, employing a variable resistance to independently control the inductance and quality factor. The TAI is fabricated in the 0.13-mum CMOS process and operates from a 1.5-V supply. The TAI chip is used to implement the TL phase shifter, which achieves a phase of -40deg to +34deg at 2.5 GHz with less than -19-dB return loss from a single stage occupying 10.8 mm times 10.4 mm. The IC phase shifter is fabricated in the same process and achieves a phase from -35deg to +59deg at 2.6 GHz with less than -19-dB return loss from a single stage occupying 550 mum times 1300 mum.