Showing papers on "Return loss published in 1998"

Microwave catheter design

Abstract: A microwave antenna system for transcatheter ablation of cardiac tissue is investigated. A numerical model based on the finite-difference time-domain method incorporating a Gaussian pulse excitation has been constructed and frequency domain electric and magnetic fields are obtained through Fourier transformation. Results are presented for a coaxial line fed monopole catheter which is modified by the successive inclusion of a Teflon sheath outer coating, a terminating disk at the tip of the antenna, a sleeve choke, and a high dielectric constant cylinder surrounding the monopole antenna. The effects of these design features are characterized in terms of specific absorption rate (SAR) and return loss (RL). Numerical calculations are confirmed by comparing with the RL measurement of a Teflon-coated monopole containing a disk and choke.

W-Band finite ground coplanar waveguide (FGGPW) to microstrip line transition

Abstract: fA uniplanar transition from finite ground coplanar waveguide (FGCPW) to microstrip line operating at W-Band has been developed. The design is uniplanar and does not require viaholes or wirebonds. The transition, centered at 94 GHz, results in 0.2 dB insertion loss with a bandwidth of 20%. The return loss is better than -17 dB from 85 GHz to 100 GHz. To our knowledge, this simple transition shows state-of-the-art performance, and can be very useful for CPW-probe to microstrip circuit measurements.

A dual polarized dual band microstrip antenna for wireless communications

Abstract: The demand for antennas for mobile wireless applications has increased dramatically over the last 10 years. Today we have a number of land and satellite based systems for wireless communications using a wide range of frequency bands. Not only do we see an increase in the number of subscribers in the different systems but also a demand for dual or multi band equipment capable of handling two or more frequency bands. Our paper describes a dual polarized, dual band antenna element suited for use in a base station antenna. The antenna element is an aperture coupled, stacked patch, maintaining the symmetry needed for dual polarization operation. The total height is less than 0.15 /spl lambda/ at the lowest frequency and the element provides broadside radiation. Whereas most previously presented dual band elements are linearly polarized microstrip antennas which utilize a number of narrow-band resonators, our design has all the broadband and dual-polarized characteristics of traditional aperture coupled patch antennas. The bandwidth for return loss>10 dB of the element covers both the 880-960 MHz GSM (Global System for Mobile Communication) band and the 1710-1880 MHz DCS (Digital Cellular System) frequency band. The measured isolation between the ports corresponding to the two orthogonal polarizations is greater than 32 dB in both bands.

Dielectric constant and loss tangent measurement using a stripline fixture

Abstract: A new approach to dielectric material characterization with a vector network analyzer is presented. As the characteristic impedance (Z/sub 0/) of a stripline transmission line can be accurately determined by measuring the two-port scattering parameters in the frequency range of interest, the dielectric constant of the insulation material that consists as part of the stripline configuration is then obtained by a relationship to the characteristic impedance. The dielectric loss (or loss tangent) can be determined by measuring the return loss and the insertion loss of the stripline. The validity of the technique is demonstrated for well-characterized dielectric materials such as Teflon-based and other composite laminates. The technique is then applied to integrated circuit (IC) molding compounds as-processed.

A wide-band multiport planar power-divider design using matched sectorial components in radial arrangement

Abstract: This paper proposes a new multiport planar power-divider design by radially combining the sectorial components and the input and output matching networks. This design can achieve good input match over a wide bandwidth without resorting to transformer sections of high-impedance lines, which are difficult to realize. This approach is applied to the design of 4-and 14-way center-fed power dividers in microstrip structures with good input match (voltage standing-wave ratio (VSWR) <1.5) over a bandwidth of 30% and 15%, respectively. The return loss of output ports and the isolation among them in the 14-way divider are less than -13 dB. A simple analysis method using the radial transmission-line theory to model the microstrip sectorial components is employed to characterize the power dividers. The calculated scattering parameters are found to be in good agreement with the measured data.

Radiation and scattering from ferrite-tuned cavity-backed slot antennas: theory and experiment

Abstract: A three-dimensional finite-element method hybridized with the spectral/spatial domain method of moments is presented for the analysis of ferrite-tuned cavity-backed slot antennas. The cavity, which is partially filled with magnetized ferrite layers, is flush mounted on an infinite ground plane with possible dielectric or magnetic overlay. The antenna operates primarily in the ultrahigh-frequency band. The finite-element method is used to solve for the electric-field distribution inside the cavity, whereas the spectral-domain approach is used to solve for the exterior region. An asymptotic extraction of the exponential behavior of the Green's function followed by a spatial evaluation of the resulting integral is used to improve computational speed. Radar cross section, input impedance, return loss, gain, and efficiency of ferrite-tuned cavity-backed slots (CBS) are calculated for various biasing conditions. Numerical results are compared with experimental data.

Circularly polarised microstrip antenna array using proximity coupled feed

Abstract: A 2/spl times/2 circularly polarised (CP) microstrip antenna array using a proximity coupled feed and sequential rotation is described. As compared with a previously presented single-element circularly polarised microstrip antenna with a cross-slot, the new array achieves a much wider impedance bandwidth of 11.18% and has an axial ratio bandwidth of 4.1%. The return loss, radiation patterns and axial ratio of the antenna array were measured and are presented.

Micromachined thermocouple microwave detector by commercial CMOS fabrication

Abstract: This paper reports on the design and testing of a thermocouple microwave detector fabricated through a commercial CMOS foundry with an additional maskless etching procedure. The detector measures true r.m.s. power of signals in the frequency range from 50 MHz to 20 GHz, and input power range from -30 to +10 dBm, the device has linearity better than /spl plusmn/0.4% for input power versus output voltage over the 40 dB dynamic range. Measurements of the return loss, obtained using an automatic network analyzer, show acceptable input return loss of less than -20 dB over the entire frequency range. The sensitivity of the detector was measured to be (1.007/spl plusmn/0.004) mV/mW.

Ku-band 16/spl times/16 planar array with aperture-coupled microstrip-patch elements

Abstract: The design and development of a Ku-band linearly polarized 16/spl times/16 microstrip-patch array is presented. The array is fed by a corporate network, using dog-bone shaped coupling apertures. Thin substrates and low-loss foam are used for antenna-bandwidth enhancement. The design of the radiating patches and feed network was aided by the commercial software package, Ensemble(R). Experimental results for the array, in terms of its return loss, radiation pattern, and gain, are presented.

Low insertion loss packaged and fibre connectorised MEMS reflective optical switch

Abstract: A new MEMS (micro electromechanical system) singlemode fibre optical switch is described that interposes a gold-coated silicon vane in a fibre gap to achieve 0.81 dB minimum insertion loss in the transmit state with 38-80 dB transmission isolation and a 2.15 dB return loss in the reflection state, all in the 1550 nm wavelength region. Control voltages were in the range 5-40 V and a switching time of 64 /spl mu/s was achieved.

Optimization of MM-wave distribution networks using silicon-based CPW

Abstract: This paper describes work relating to the optimization of silicon-based, coplanar waveguide (CPW) air-bridge and bend discontinuities. Experimental results shown here verify that the return loss is improved by introducing a step-compensation into the CPW center conductor. The technique is demonstrated in the design of an asymmetric coplanar-strip Wilkinson power divider at 45 GHz.

Novel V-groove-based interconnect technology

Abstract: A novel fiber optic interconnect technology based on injection molded V-grooves that uses the fiber’s inherent precision to provide a reliable, robust and consistent optical connection is described. This technology has been expanded and applied to optical transceivers that can now achieve the same port density as that of current copper-based systems. Both the interconnect and the optical transceivers are shown to have performance levels similar to current ferrule-based multimode technology. Testing was performed in an effort to accurately measure performance and qualify the connector design for field use. Test results for the interconnect met the performance requirements of Electronics Industry Association/Telecommunications Industry Association (EIA/TIA) 568, which represent test standards for local area networks. Results of insertion loss and return loss performance of the duplex ferrule-less connector design were measured when 400 unique links were tested using 62.5 mm multimode fiber. Mating durability performance tests were performed in which plugs were reconnected to the socket 500 times. A new generation of small form factor transceivers is discussed that were developed using the same V-groove technology. Optomechanical tests are reported that show the performance level of these new transceivers is comparable to existing ST transceiver technology.

Wide-band antenna element with integrated balun

Abstract: A wide-band antenna element with an integrated balun has been successfully developed. This element will be used in the OSMA demonstrator array. The measured and predicted bandwidth of an isolated balun is 4:1 for a return loss lower than -18 dB (VSWR 1.3:1). For an antenna element with integrated balun a VSWR of 2:1 is achieved over an octave bandwidth. A VSWR< 2.7:1 was measured over a frequency band of 4:1.

High-isolation polarization-independent optical quasi-circulator with a simple structure.

Abstract: A high-isolation polarization-independent optical quasi-circulator with a simple structure is proposed. A Porro prism is employed in this kind of device for what is believed to be the first time. Because a Porro prism is used, light beams pass back and forth through the main elements in the device. Thus the number of elements used in the device is decreased, and the device structure is simplified. A four-port quasi-circulator with monomode fibers was assembled and tested at the 1.55?µm wavelength. Its insertion loss, isolation, and return loss are ?1.63, ?60, and ?55.6 dB, respectively.

Direct synthesis of tubular bandpass filters with frequency-dependent inductors

Abstract: A method for direct synthesis of a tubular filter with thin-film frequency-dependent lumped element resonators is presented. The synthesis procedure is developed with frequency-dependent inductors to accommodate a large parameter aspect ratio in compact configurations. The explicit design equations are derived from required coupling coefficients among resonators, which provide a great flexibility in choosing design parameters. A design example of a 4th order bandpass filter using high-temperature superconductor (HTS) thin-film material is shown which has a 0.6% fractional bandwidth, a less than 0.2 dB insertion loss and a 20 dB return loss. Experimental data show a good agreement with simulation performance. The technique is especially useful for designing ultra-narrowband filters where the proper coupling is difficult to achieve.

Analysis and design of tapered finline arrays for spatial power combining

Abstract: In an effort to enhance the performance of a previously proposed waveguide-based spatial power combiner, an optimal tapered finline array was designed to improve the gain flatness and return loss of the power combiner. An optimal taper was designed based on the theory of small reflection and the design equations for Klopfenstein (1956) tapers. Due to its simplicity in developing computer codes, the spectral domain method was used to compute the propagation constants corresponding to a finline structure with various slot widths. The results of return loss measurements have shown good agreement with the simulation results, presenting a broadband frequency response and good return loss characteristics.

Scattering parameter analysis of light-induced periodic microwave structures

Abstract: Based on the scattering parameter concept, an exact analysis of the reflection and transfer properties of light-induced waveguide gratings applied to microwave or millimetre wave frequencies, with special regard to internal return loss and multiple reflections, is reported. After a short presentation of the foundations of periodically photoexcited semiconductor waveguide structures, the S-parameters of a multi-stage optoelectronic grating configuration under optical CW-excitation are calculated. Moreover, the influence of an impedance mismatch between waveguide grating and measuring system is outlined quantitatively in the form of a modified scattering matrix.

Plastic microwave multi-chip modules for wireless communication applications

Abstract: This paper describes a high density, microwave plastic multi-chip module (MCM) with vertical feed throughs providing RF/DC I/Os at the module backside allowing for a low thermal resistance solder attach to a printed circuit board. A return loss of better than -20 dB up to approximately 3.8 GHz was measured for the coplanar vertical interconnect from the plastic module to a printed circuit board. Functional T/R modules operating between 1.60 GHz and 2.0 GHz were also fabricated with this technology.

Method and circuit arrangement for reducing passband ripple of a bandpass filter

Abstract: The passband ripple of a filter arrangement, including an amplifier and a bandpass filter, is tuned to a desirable level at the expense of the output return loss of the filter arrangement. Thus, the output return loss is increased as a result of reducing the ripple. To reduce the output return loss to a desired level, a lossy network is coupled to the output of the filter. The output return loss is reduced by twice the insertion loss of the lossy network. The insertion loss of the lossy network can be compensated for by increasing the gain of the amplifier.

A Novel Microstrip to Coplanar Waveguide Transition for Flip-Chip Interconnection using Electromagnetic Coupling

Abstract: A novel compact microstrip to coplanar waveguide (CPW) transition is proposed for flip-chip interconnection. Broadband performance of the transition is simulated and agrees well with measured results. A good interconnection between microstrip line on a motherboard to CPW on a flip-chip is accomplished without any vias. For 10dB return loss, the microstrip-to-CPW transition and the microstrip-to-flip-chip interconnection present 170% and 140% bandwidth, respectively.

Compact latching type PANDA fiber switch

Abstract: A compact and low-polarization crosstalk 1/spl times/2 PANDA fiber switch has been developed by precisely aligning the principal axes between the facing fibers. It exhibits an insertion loss of 0.5 dB, a return loss of 42 dB, polarization crosstalk of -30 dB, and a driving power of 9 mW. High-switching reproducibility with a loss change of less than 0.1 dB and a crosstalk change of less than 2 dB were obtained during 10/sup 4/ switching operations.

Beam Switching Cylindrical Array Antenna System for Communication

Abstract: The beam switching cylindrical array, which is a unique system, has been designed and developed to cover 360° in azimuth plane by generating 16 beams with specified elevation coverage.In this design, the concept of fast aperture selection (4 x 4) in microseconds from the total cylindrical array has been realised successfully to meet the requirement of point-to-multipoint communication. The components of the array, viz., radiating elements, powder dividers, switches, etc., are designed in printed circuit type, and hence, objectives of lightweight and ease of reproducibility are achieved. The lightweight of the array makes it accessible for easy mounting at a specified height for achieving longer communication range. Finally, a low-loss radome is incorporated to protect the array from environmental conditions. The various parameters, viz., return loss, gain, and switched-beam radiation patterns were measured over a bandwidth of 300 MHz in L- band and typical measured results are presented in this paper.

FDTD optimization of beam forming network for multibeam antenna

Abstract: A 4/spl times/4 Butler matrix beam forming network for multibeam antennas was designed and optimised in terms of packing density, amplitude and phase accuracy and other properties. The finite-difference time-domain (FDTD) method with perfectly matched layer (PML) termination was used to optimise return loss, insertion loss and output phases of the network. The computed performance for the final design was compared with measurement.

Design of a 60 GHz subharmonic mixer MMIC

Abstract: The design of a subharmonically pumped (SHP), monolithic microwave integrated circuit (MMIC) mixer for future wireless communications applications is described. The mixer uses an anti-parallel diode pair to achieve frequency translation by mixing the RF signal with the second harmonic of the fundamental LO pump. The circuit was fabricated by Triquint Semiconductor Inc. using their GaAs MMIC PHEMT process. The overall chip size is 1.2 mm × 1.3 mm. Measured conversion loss is 13 dB with a 61 GHz RF input signal and RF port return loss is better than 10 dB over a 61.4 to 62.5 GHz frequency range. Simulation predicts a conversion loss of 13 dB over 59 to 61 GHz band and an RF port return loss of better than 10 dB over this range. The simulated 1-dB compression point occurs with an RF input power level of 5 dBm.

Characterization of Machining-Damage Layer for Optical Fiber Ends. Relation between Damaged Layer and Return Loss.

Abstract: 光通信部品の加工端面の高品質化を目的として, 重要である端面の反射減衰量と加工ダメージの関係を究明した.その結果, (1) 加工変質層の屈折率と厚さが, 反射減衰量の主要因であることを示し, 加工変質層をエリプソメータにより評価することにより反射減衰量の予測が可能であることがわかった.(2) 1μm以下のダイヤモンド砥粒で加工し, 微分干渉顕微鏡では, スクラッチのない光学的鏡面を示す端面でも, AFMでミクロに観察すると多数のスクラッチが観察された.まもた, その量と大きさはダイヤモンド砥粒径に依存することがわかった.(3) ダイヤモンド砥粒による加工では, 高屈折率層が表面下に形成されるが, その厚さは粒径が小さくなるに従い薄くなることを確認した.これは反射減衰量が大きくなることと対応している.またこの屈折率は, 加工による残留ひずみによる密度上昇から説明できることが明らかになった.(4)ダイヤモンド砥粒のように高い屈折率を持つのダメージ層を形成する場合でも, 砥粒径を小さくし層を薄くすることによって50dB程度の高反射減衰量を得ることができることがわかった.

Interrogator for semi-passive transponder tags

Abstract: An interrogator circuit 2 for use with semi-passive transponders 30 (which reflectively modulate transmitted signal 28) has a transistor 8 which self oscillates to radiate power 28 from patch antenna 4. The transistor simultaneously acts as a self oscillating mixer producing an output 40 representative of the modulated signal 32 received at antenna 4. Bias and matching networks 12, 14 including microstrip lines 16, 26 ensure that the FET 8 operates as a negative resistance. FET 8 is coupled to the antenna by a matching network 6 comprising microstrip line 10. In a small signal condition at start up the reflection gain of FET 8 is greater than the reflection coefficient of antenna 4 so that any signal at gate g will be reflected with increased magnitude. When the circuit 2 reaches a stable oscillatory condition, the reflection gain of FET 8 equals the return loss of antenna 4. The interrogator may modulate the transmitted signal 28 by modulating the FET drain-source current. The frequency of oscillation of the circuit is determined by the resonant frequency of the antenna. A fine tuning circuit 42 comprising an additional patch antenna element 50 enables accurate frequency setting by adjustment of bias voltage V bias .

Enhanced Design for Flip Chip Interconnects

Abstract: Multichip and flip chip technology has become increasingly popular in the past years. It employs a series of chips flipped and connected through metallic bumps. A study for improving the performance of flip chip interconnects is recently presented by Ghouz and El-Sharawy for frequencies up to 50 GHz. In that study, the idea of staggering the signal line interconnect with respect to the ground plane bumps to reduce reflection and insertion loss is introduced. In this paper concentration is put on re-shaping the discontinuity region in order to provide a better impedance match between the CPW-motherboard and the CPW-chip, and thus reducing reflection at the input terminals. Several approaches are tested to accomplish lower return loss, among them, the use of bumps of different thickness located at different positions, the use of tilted bumps or "ramps", and the use of dielectric loading on the bumps. The results indicate that the performance of these flip chips is greatly enhanced and extended to frequencie...

Fast and efficient mode-matching analysis of ridged circular waveguide polarizers

Abstract: A fast and efficient mode-matching technique is applied to the analysis and design of polarizer components in ridged circular waveguide technology. Two different structures (the septum polarizer and the longitudinal-ridge polarizer) are investigated with respect to the validity of approximating the rectangular-cross-section septa by conically shaped ridges in theory. Measurements of two different prototypes demonstrate, first, that the axial ratio response is not potentially critical to this approximation and, second, that some differences occur with respect to return loss and isolation performance, but that these difference have only been encountered beyond the 25 dB margin. A CPU time comparison with HFSS results in a ten-minutes-versus-three-hours advantage of the mode-matching technique.

Inductors allow low-voltage performance for IC mixers

Abstract: In this paper it is established how planar inductors on silicon and bond-wire inductors can be used to scale down the supply voltage to 1.5 V for Gilbert type RF mixers. A demonstration mixer which downconverts a signal from 900 MHz to an intermediate frequency of 50 MHz is implemented in a 0.8 /spl mu/m BiCMOS process offered by Austria Mikro Systeme International GmbH. The measurement results for the mixer as well the lumped element models for the used planar inductor and for the bondwire are presented. The measurements suggest that a pleasing return loss of about 9 dB is obtained for both the input and output ports of the mixer without using any external components for impedance matching.

High Temperature Superconducting Filters for Receiver Front-end of Mobile Telecommunication Base Station

Abstract: The performance of multi-pole microstrip filters with low insertion loss and sharp-skirt using YBa2Cu3O7-δ high temperature superconducting thin films is presented. The HTS films were deposited on both sides of substrates by a DC sputtering method. The surface resistance of the films was about 0.35mΩ (at 70k and l0GHz). A 9-pole bandpass filter was designed at 2.6GHz center frequency with bandwidth 34MHz. The filter was fabricated using 40mm X 25mm HTS films on a 0.5-mm thick MgO substrate. The insertion loss at 70 K was about 0.ldB with 0.ldB ripple and the minimum return loss was about 20 dB across the passband of the filter. In addition, a 15-pole bandpass filter whose center frequency and bandwidth were 1.53GHz and 60MHz respectively was fabricated using 50-mm diameter HTS film on 0.5-mm thick LaAlO3 substrate. The insertion loss at 70K was less than O.ldB and the rejection level was more than 70dB at the rejection band.