Showing papers on "Return loss published in 2010"

Design equations for tapered microstrip-to-Substrate Integrated Waveguide transitions

Abstract: This paper presents design equations for the microstrip-to-Substrate Integrated Waveguide (SIW) transition. The transition is decomposed in two distinct parts: the microstrip taper and the microstrip-to-SIW step. Analytical equations are used for the microstrip taper. As for the step, the microstrip is modeled by an equivalent transverse electromagnetic (TEM) waveguide. An equation relating the optimum microstrip width to the SIW width is derived using a curve fitting technique. It is shown that when the step is properly sized, it provides a return loss superior to 20 dB. Three design examples are presented using different substrate permittivity and frequency bands between 18 GHz and 75 GHz. An experimental verification is also presented. The presented technique allows to design transitions covering the complete single-mode SIW bandwidth.

Dual-Band Circularly Polarized $S$ -Shaped Slotted Patch Antenna With a Small Frequency-Ratio

Abstract: A dual-band single-feed circularly polarized, S-shaped slotted patch antenna with a small frequency-ratio is proposed for GPS applications. An S-shaped slot is cut at the centre of a square patch radiator for dual-band operation. A single microstrip feed-line is underneath the center of the coupling aperture ground-plane. The frequency-ratio of the antenna can be controlled by adjusting the S-shaped slot arm lengths. The measured 10-dB return loss bandwidths for the lower and upper-bands are 16% (1.103-1.297 GHz) and 12.5% (1.444-1.636 GHz), respectively. The measured 3-dB axial-ratio (AR) bandwidth is 6.9% (1.195-1.128 GHz) for the lower-band and 0.6% (1.568-1.577 GHz) for the upper-band. The measured gain is more than 5.0 dBic over both the bands. The measured frequency-ratio is 1.28. The overall antenna size is 0.46 ?o × 0.46?o × 0.086?o at 1.2 GHz.

Broadband Self-Compensating Phase Shifter Combining Delay Line and Equal-Length Unequal-Width Phaser

Abstract: In this paper, a broadband self-compensating phase shifter is presented and developed on the basis of substrate integrated waveguide (SIW) technology. Since the SIW is a dispersive guided-wave structure, the effective bandwidth of SIW phase shifter is usually narrow. Phase shifts generated by two different structures, namely delay line and equal-length unequal-width phase shifter, are discovered in this work to present interesting opposite tendencies versus frequency. Therefore, an appropriate combination of them will make the phase shift almost constant over a very wide band. Design equations and process are given following a mathematical analysis. To demonstrate the interesting and useful features of the proposed technique, a 90° and a 45° self-compensating phase shifters are designed as showcases with standard printed circuit board process. For the 90° version, the measured amplitude and phase imbalance between the two paths are within 0.2 dB and 2.5° , respectively, within the frequency band from 25.11 to 39.75 GHz, or around 49% bandwidth. The return loss is found to be better than 12 dB within the frequency band of interest. The 45° one has the similar excellent performance. The measurements demonstrate that this type of SIW phase shifter is superior to all of its counterparts.

A Direct-Write Printed Antenna on Paper-Based Organic Substrate for Flexible Displays and WLAN Applications

Abstract: This paper presents the design, fabrication and measurements of a direct-write printed low-cost and flexible inverted-F antenna on an ultra-low-cost paper-based organic substrate for wireless local area network (WLAN) and flexible display applications. Innovations include the study and utilization of paper as a high-frequency substrate for the first time in the gigahertz (GHz) range, the fabrication technology for the direct-write printing of the antenna as a flexible RF electronic device, and the investigation of antenna flexibility in conjunction with flexible displays. Although paper substrates exhibit relatively high dielectric losses (tanδ ~ 0.065 at 2.45 GHz), the maximum realized gain of the fabricated antenna is measured to be + 1.2 dBi giving a total efficiency ~ 82%. Simulated results of the antenna's return loss and radiation patterns agree well with the measurements, and can lead to a whole new class of flexible low-cost electronic devices of the future.

Dual-Band Impedance Transformer Using Two-Section Shunt Stubs

Abstract: This study presents a modified shunt-stub dual-band impedance transformer. The load impedances can be complex and unequal at two uncorrelated frequencies. The proposed transformer has two parts; each part is composed of a two-section transmission line. Similar to the single-stub matching network at a single frequency, a two-section transmission line is connected to the load and transforms the load impedances to normalized unit conductance at the two designated frequencies simultaneously. The resulting susceptances are then canceled out simultaneously by a two-section shunt stub at the two frequencies. The required nonlinear simultaneous equations are derived and solved to obtain the physical parameters of transmission lines. Rearranging the simultaneous equations to construct an objective function with only one unknown variable makes it easier to solve the equations. This approach avoids high-impedance transmission lines by choosing the characteristic impedance of each transmission line first. Return losses for various load impedances are simulated to validate the proposed structures. Good agreements between numerical and measured results validate the proposed structure.

A $Ka$ -Band High-Gain Circularly Polarized Microstrip Antenna Array

Abstract: In this letter, a four-element high-gain circularly polarized microstrip antenna array operating in the Ka -band is proposed. The sequentially rotated series-parallel stub technique is employed in constructing the feed network to allow symmetrical positioning of microstrip patch elements, resulting in good axial ratio of polarization. In addition, an L-shaped matching branch is used to offer good impedance matching and spatial flexibility for positioning patch elements. Both simulation and measurement results are presented. They agree with each other well and demonstrate much better 3-dB axial-ratio bandwidth and return loss than the single patch antenna.

Log periodic fractal koch antenna for UHF band applications

Abstract: In this paper, the design of Log Periodic Fractal Koch Antennas (LPFKA) is proposed for Ultra High Frequency (UHF) band applications. The procedure to design the LPFKA with three different numbers of iterations in order to reduce the antenna size is discussed. The Computer Simulation Technology (CST) software has been used to analyze the performances of the designed antennas such as return loss, radiation patterns, current distribution and gain. The antennas have been fabricated using FR4 laminate board with wet etching technique. Using fractal Koch technique, the size of the antenna can be reduced up to 27% when the series iteration is applied to the antennas without degrading the overall performances. Both simulated and measured results are compared, analyzed and presented in this paper.

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.

Microstrip-fed broadband circularly polarised monopole antenna

Abstract: A microstrip-fed broadband circularly polarised (CP) monopole antenna was studied A broad impedance bandwidth and wide axial ratio bandwidth (AR-BW) could be achieved simultaneously This antenna used a conventional monopole architecture, except for its deforming ground plane and asymmetric-feed approach The asymmetric-feed was used to provide an orthogonal component distinct from its original linear polarisation In addition, by embedding a slit and a stub on the ground plane, this antenna could generate CP wave radiation and achieve a broad impedance bandwidth According to the measurement results, the impedance bandwidth was 656 GHz for a 10 dB return loss, which covered a range of 232 888 GHz The AR-BW was 12 GHz for a 3 dB AR, which covered a range of 32 44 GHz

Phase-Shifter Design Using Phase-Slope Alignment With Grounded Shunt $\lambda/4$ Stubs

Abstract: This paper presents the theory and a design method for distributed digital phase shifters, where both the phase-error bandwidth and the return-loss bandwidth are considered simultaneously. The proposed topology of each phase bit consists of a transmission-line (TL) branch and a bandpass filter (BPF) branch. The BPF branch uses grounded shunt λ/4 stubs to achieve phase alignment with the insertion phase of the TL branch. By increasing the number of transmission poles of the BPF branch, the return-loss bandwidth can be increased. Analysis of the BPF topology with one, two, and three transmission poles is provided. The design parameters for 22.5° , 45° , 90° , and 180° are provided for bandwidths of 30%, 50%, 67%, and 100%. The relations between phase error, return loss, and maximum achievable phase shift are shown for the three topologies for design purposes. The methodology is also applicable to bandwidths larger than 100%. To validate the method, four separate L-band phase bits (1-2 GHz) are designed and measured. A complete 4-bit phase shifter with single-pole double-throw switches is then designed and measured. The measured rms phase error of the phase shifter is less than 3.6 °, while the return loss is larger than 15 dB from 1.06 to 1.95 GHz for all 16 phase states.

Ultra wideband power divider using tapered line

Abstract: A power divider with ultra-wideband (UWB) performance has been designed. The quarter-wave transformer in the conventional Wilkinson power divider is replaced by an exponentially tapered microstrip line. Since the tapered line provides a consistent impedance transformation across all frequencies, very low amplitude ripple of 0.2dB peak-to-peak in the transmission coe-cient and superior input return loss better than 15dB are achieved over an ultra-wide bandwidth. Two additional resistors are added along the tapered line to improve the output return loss and isolation. Simulation performed using CST Microwave Studio and measured results conflrm the good performance of the proposed circuit. The return loss and the isolation between the output ports are better than 15dB across the band 2{ 10.2GHz. Standard ofi-the-shelf resistance values can be selected by optimizing the physical locations to mount the resistors. Better performance can be achieved with more isolation resistors added. Hence, the number of isolation resistors to be used may be selected based on the desired bandwidth and level of isolation and return loss speciflcations.

A Wideband Common-Mode Suppression Filter for Bend Discontinuities in Differential Signaling Using Tightly Coupled Microstrips

Abstract: A new type of bend is proposed that reduces differential-to-common mode conversion occuring at the bend discontinuity in coupled microstrip lines for high-speed digital circuits. Simultaneously, great care has been taken to minimize the differential reflection coefficient and insertion loss, leading to an overall improved signal integrity. This is achieved by tapering the microstrip lines to tightly or very tightly coupled ones in the area of the bend. Full-wave simulations in the DC to 6 GHz frequency range show that over 9 dB and 14 dB suppression of conversion noise is achieved for tightly coupled and very tightly coupled bends, respectively. Also for these new structures, with a total length of 100 mm, the insertion loss remains below 0.6 dB. Measurements on prototype bends show very good agreement with full-wave simulations. Also time domain measurements demonstrate the significant reduction in conversion noise while keeping return loss low. Moreover, for design purposes, a dedicated circuit model which closely matches the full-wave characteristics of the proposed bends is presented.

Capacitive RF MEMS Switches Fabricated in Standard 0.35- $\mu{\hbox{m}}$ CMOS Technology

Abstract: The objective of this paper is to investigate the integration of capacitive type RF microelectromechanical systems (MEMS) switches in a standard CMOS technology. A maskless monolithic integration process dedicated to electrostatically actuated capacitive type RF MEMS switches is developed and optimized. The fabricated switches consist of composite metal-dielectric warped membranes. The warped-plate structure is used to increase the capacitance ratio of the switch. The switches are fabricated using the interconnect metal and dielectric layers available in a standard 0.35-μm CMOS process. Measurement results for the first switch show an insertion loss less than 0.98 dB, a return loss below 13 dB up to 20 GHz in the up-state, and a down-state isolation of 12.4-17.9 dB from 10 to 20 GHz. The capacitance ratio is enhanced up to 91:1 using the warped-plate structure. A second cascaded switch consisting of two shunt capacitive switches and a slow-wave high-impedance transmission line section is designed and fabricated for high-isolation applications. The measured insertion loss for this switch is less than 1.41 dB up to 20 GHz, the return loss is below 19 dB, and the isolation is 19-40 dB across the frequency band from 10 to 20 GHz. The proposed RF MEMS switches can be used in millimeter-wave CMOS RF front-ends where multiband functionality and reconfigurability is required.

Octave Bandwidth Compact Turnstile-Based Orthomode Transducer

Abstract: A 64% instantaneous bandwidth scalable turnstile-based orthomode transducer to be used in the so-called extended C-band satellite link is presented. The proposed structure overcomes the current practical bandwidth limitations by adding a single-step widening at the junction of the four output rectangular waveguides. This judicious modification, together with the use of reduced-height waveguides and E-plane bends and power combiners, enables to approach the theoretical structure bandwidth limit with a simple, scalable and compact design. The presented orthomode transducer architecture exhibits a return loss better than 25 dB, an isolation between rectangular ports better than 50 dB and a transmission loss less than 0.04 dB in the 3.6-7 GHz range, which represents state-of-the-art achievement in terms of bandwidth.

Wideband Bandpass Filter With Reconfigurable Bandwidth

Abstract: This letter proposes a novel building block for developing tunable wideband bandpass filters. The proposed circuit block mainly consists of short circuit coupled lines and short circuit stubs with pin diodes as tuning elements. This work aims to demonstrate reconfigurable bandwidth of this type of filter. Two filters are designed and fabricated; one can be switched between a fractional bandwidth (FBW) of 16.3% and 35% at a center frequency of 1.9 GHz, and the other can be switched from a FBW of 27.8% to 37.4% at a center frequency of 1.9 GHz. The insertion loss and return loss in the first filter range from 4.17 dB to 0.4 dB and 27.54 dB to 19.04 dB. The second filter exhibits an insertion loss ranging from 0.73 dB to 0.43 dB and a return loss range from 31.1 dB to 27.7 dB. The tested filters show good agreement with EM simulations.

Tunable SIW bandpass filters with PIN diodes

Abstract: This paper introduces a novel tunable SIW filter implemented using PIN diode switching elements The two-pole filter provides six states ranging from 155 GHz to 20 GHz (25% tuning) Fractional bandwidth ranges from 23% – 30% with insertion loss less than 54 dB and return loss greater than 14 dB over the entire tuning range Each SIW cavity is tuned by perturbing via posts connecting or disconnecting to/from the cavity's top metal layer In order to separate the biasing network from the SIW filter, a three-layer PCB is fabricated using Rogers RT/duroid substrates

Millimetre-wave broadband transition of substrate-integrated waveguide to rectangular waveguide

Abstract: Proposed is a new substrate-integrated waveguide to air-filled rectangular waveguide (WR-10) transition for use at millimetre-wave frequencies. The transition combines the features of low return loss and low insertion loss over the 42 GHz bandwidth and it can be manufactured without a high degree of complexity. A 75-115 GHz band prototype of the proposed broadband transition is designed and fabricated. Simulated and measured results of the prototyped back-to-back transition show good agreement.

Inductance-Loaded Y-Shaped Resonators and Their Applications to Filters

Abstract: Inductance-loaded Y-shaped resonator and its applications to ultra-wideband (UWB) bandpass filters have been presented in this paper. Based on the odd- and even-mode equivalent circuits, the resonant characteristics of the proposed microstrip resonator with various electrical length and admittance ratio values are investigated. The relationship between the external quality factor and the parameters of the coupling structure has been analyzed to give a design approach for the UWB filter. Two types of UWB bandpass filters are designed to demonstrate the practicality of the proposed resonator. To get tight coupling, the high-impedance parallel-coupled line has been used in the input/output of the first UWB bandpass filter. Both simulated and measured results show that the first UWB filter has a 10-dB return loss bandwidth of 5.6 GHz, a group delay variation of less than 0.3 ns, and a wide upper stopband with more than 20-dB attenuation up to 17.5 GHz. The multilayer technology is applied to the second UWB bandpass filter to provide tight coupling by using the broadside-coupled structures. The measured results show that the multilayer UWB filter exhibits excellent performance, including 1-dB insertion loss and 10-dB return loss bandwidths of 3.3-10.4 GHz with a minimum insertion loss of 0.45 dB at 6.85 GHz, as well as 3-dB insertion loss bandwidth and group delay variation < 0.22 ns over the entire UWB band.

True-Time-Delay Beamforming With a Rotman-Lens for Ultrawideband Antenna Systems

Abstract: An analytical design model for Rotman-lenses is presented, with an accurate treatment of the return loss of the ports and their phase centers. The detailed design equations allow a very fast prototyping prior to numerical simulations for the final adjustment. Based on the presented model a prototype has been built for the true-time-delay phasing of an antenna array for the ultrawideband frequency range from 3.1 GHz - 10.6 GHz. Measurement results of the prototype together with an antenna array for transient systems are presented in the time and frequency domain.

A Waveguide to Microstrip Inline Transition With Very Simple Modular Assembly

Abstract: A microstrip to empty rectangular waveguide transition is presented for systems requiring a simple modular assembly with good electrical performance. The structure is based on three building blocks, involving a microstrip line to dielectric-loaded rectangular waveguide, a transition between dielectric-loaded and empty rectangular waveguides with reduced height, and a final transformer to standard waveguide. These three building blocks (segmentation based on the design point of view) are combined in three simple parts which are assembled in a straightforward modular way, without soldering. These features are very important for signal feeders requiring a large number of transitions, as the X-band phased array antenna where the proposed structure has been integrated. The concepts involved in the design and manufacturing are illustrated with a prototype showing measured return loss of 10 dB and insertion loss of 1.1 dB in the band 8.5-9.5 GHz.

Design and fabrication of bandpass filters in glass interposer with through-package-vias (TPV)

Abstract: This paper presents the integration of WLAN (2.4 and 5GHz) bandpass filters in glass interposer using through-package vias. The filters include novel embedded passive components such as stitched capacitors with reduced shunt parasitics and via-based inductors that provide area reduction. The filters designed for 2.4 GHz showed an insertion loss of less than 2dB and better than 15dB return loss, while the 5GHz filters showed an insertion loss of less than 1dB with better than 20dB return loss. Stop-band rejection of over 35dB was observed at 2.2 GHz on the 2.4 GHz bandpass filters. The measured results showed good agreement with the simulated values and indicated that the performance on glass interposer closely matches the performance of the more expensive high resistivity silicon with similar properties.

Design Considerations for Octave-Band Phase Shifters Using Discrete Components

Abstract: A new method for octave-band phase-shifter design based on high-pass, low-pass, bandpass, and all-pass networks (APNs) using discrete components is presented. First, the general synthesis method is provided to find the optimum return loss and phase error of a high-pass/low-pass phase shifter. It is also shown that the conventional design method is a special case of the method presented here. The proposed method facilitates tradeoffs between the bandwidth, phase error, and return loss, which is not possible in the conventional method. Phase bits of 22.5°, 45 °, and 90 ° are designed using this method. For the phase bit of 180° , a new topology using a third-order bandpass network and an APN is proposed. The phase error is reduced from 25 ° to 7.4 ° and the return loss is improved from 5 to 22 dB over the whole octave band compared to the conventional method. For the cascaded 4-bit phase shifter, the return loss is improved from 5 to 19 dB and the rms phase error is reduced from 13.5 ° to 4.3 ° in theory. The experimental results of the 4-bit phase shifter show an rms phase error of 5.9° and a return loss of 13 dB from 530 to 1090 MHz. The maximum amplitude imbalance is 0.6 dB for all 16 phase states.

A Novel Tri-Band Branch-Line Coupler With Three Controllable Operating Frequencies

Abstract: A novel branch-line coupler with three controllable operating frequencies is presented for tri-band operation. The tri-band operation is achieved by attaching a matching circuit to each port of the conventional branch-line coupler. Closed-form design equations are derived. For verification, a microstrip 3 dB branch-line coupler operating at 0.9/2/2.45 GHz is designed, fabricated and measured. The measured results are in good agreement with the simulated results. When the return loss and isolation are better than 15 dB and 20 dB simultaneously, the measured bandwidths of three operating bands are all almost 40 MHz, while the amplitude imbalance is below 0.8 dB and the phase difference is within .

Compact Wideband Microstrip Bandpass Filter Using Quasi-Spiral Loaded Multiple-Mode Resonator

Abstract: In this letter, a new model for further reducing the size and increasing the bandwidth (BW) of a class of bandpass filter (BPF) utilizing multi-mode resonator is presented. A new technique based on spiral transmission line loading to achieve higher BW and further size reduction is analyzed for this class of BPF. A compact ultra wideband microstrip BPF is proposed by using this technique. The capability of tuning the transmission zeroes in the proposed model is also studied. Estimates for the frequencies of these transmission zeroes are directly presented. The overall BW of the proposed BPF is shown to be increased more than 12.6% and its size to be reduced more than 70% compared with the conventional ones. The proposed BPF provides a relatively wide 3 dB fractional bandwidth of 72.6% frequency response with two transmission zeros at the lower and upper stop-bands to provide a very sharp cutoff and low passband insertion-loss and good return-loss characteristics.

Broadband transition between rectangular waveguide and substrate integrated waveguide

Abstract: A novel broadband waveguide-to-substrate integrated waveguide transition is presented. The transition is realised by using a fin line probe inserted into a rectangular metal waveguide. A single back-to-back transition covering the KA band is designed, fabricated and tested. Measured results show that good agreement with simulation, an insertion loss less than 1.4 dB and a return loss better than 15 dB at 25 40 GHz are obtained for a back-to-back structure. This broadband transition between the rectangular waveguide and substrate integrated waveguide can be used widely in microwave and millimetre-wave circuits and systems.

Small Monopole Antenna With Checkered-Shaped Patch for UWB Application

Abstract: A monopole antenna, consisting of a square patch with square slots and a ground plane truncated with two mirror L-shaped notches is designed for ultrawideband (UWB) applications. The design employs a checkered-shaped semifractal patch with Lp × Wp squares. The proposed antenna operates in the 3.1-10.6-GHz band and has small overall dimensions of 12 × 18 × 1.6 mm3. The effect of the ground plane notch on the optimization of the return loss is discussed in detail.

Side-Coupled Shorted Microstrip Line for Compact Quasi-Elliptic Wideband Bandpass Filter Design

Abstract: This letter presents a novel structure composed of a shorted quarter-wavelength microstrip line side-coupled to two open-ended stubs. The proposed topology exhibits a quasi-elliptic wideband response with two transmission zeros enhancing the selectivity. To verify the design concept, one filter example has been designed, fabricated and measured. Good insertion/return losses, flat group delay, sharp transition, excellent DC-choked property, simple topology, and compact size are achieved as demonstrated in both simulation and experiment.

A 60–110 GHz Transmission-Line Integrated SPDT Switch in 90 nm CMOS Technology

Abstract: This letter demonstrates a fully integrated transmit/receive single-pole-double-throw switch in standard bulk 90 nm CMOS process. This switch is based on the transmission-line integrated approach that reduces the effect of parasitic capacitance of transistors in the desired band, and this approach can achieve good isolation and return loss with fewer stages of transistors and broad bandwidth. The switch provides an insertion loss of 3-4 dB and a return loss better than 10 dB in 60-110 GHz. The measured isolation is better than 25 dB. The measured 1 dB compression point of input power is 10.5 dBm at 75 GHz. To the best of our knowledge, this is the first CMOS switch operating beyond 100 GHz.

Micro-Coaxial Impedance Transformers

Abstract: This paper demonstrates two broadband air-filled micro-coaxial 4:1 (2-24 GHz) and 2.25:1 (2-22 GHz) impedance transformers. The 4:1 transformer converts 50 to 12.5 Ω and the 2.25:1 device transforms 50 to 22.22 Ω. The circuits are fabricated on silicon with PolyStrata technology, and are implemented with 650 μm × 400 μm air-filled micro-coaxial lines. Back-to-back circuits and single structures with geometrical tapers are designed for systematic characterization. Simulation and measurement results are in excellent agreement. The return loss for both transformers is better than 15 dB over the design bandwidth.

An Excellent Gain Flatness 3.0–7.0 GHz CMOS PA for UWB Applications

Abstract: This letter presents an excellent gain flatness CMOS power amplifier (PA) for UWB applications at 3.0-7.0 GHz in TSMC 0.18 μm CMOS technology. The UWB PA proposed here employs a current-reused technique to enhance the gain at the upper end of the desired band, a shunt and a series peaking inductors with a resistive feedback at the second stage to obtain the wider and flat gain, while shunt-shunt feedback helps to enhance the bandwidth and improve the output wideband matching. The measurement results indicated that the input return loss (S11) less than -6 dB, output return loss (S22) less than -7 dB, and excellent gain flatness approximately 14.5 ±0.5 dB over the frequency range of interest. The output 1 dB compression of 7 dBm, the output third-order intercept point (OIP3) of 18 dBm, and a phase linearity property (group delay) of ±178.5 ps across the whole band were obtained with a power consumption of 24 mW.