Showing papers on "Return loss published in 1996"

Compact all-fiber add-drop-multiplexer using fiber Bragg gratings

Abstract: A novel compact all-single-mode fiber add-drop-multiplexer for dense wavelength-division-multiplexing systems is demonstrated. The device consists of a polished fiber coupler with identical Bragg gratings within the interactive length. The multiplexer operation has been theoretically analyzed and calculated transmission and reflection spectra are given. A fabricated prototype device shows good performance, but suffers from a high-insertion loss of 7 dB, which is due to the long but imperfect coupling region and can be drastically reduced in principle. A return loss >30 dB, coupling efficiency=99%, and bandwidth at FWHM /spl Delta//spl lambda/=1.2 mn was measured.

A compact MMIC-compatible microstrip to waveguide transition

Abstract: A new type of microstrip to waveguide transition is presented, based on slot coupling and a dielectric quarter wave transformer. For a return loss of 20 dB, a relative bandwidth of 16% was achieved. The structure is compact, MMIC-compatible and can be made hermetic.

Array of circular-polarised cross dielectric resonator antennas

Abstract: A compact array of circular polarised cross-shaped dielectric resonator antennas (XDRAs) is presented. The array consists of 2/spl times/2 XDRAs elicited by microstrip-fed slot apertures in the X-band. By using sequential rotation to feed the XDRAs, the circular polarisation bandwidth is significantly increased from 5% for the individual XDRA to 16% in the array. The array also achieves a wide impedance bandwidth: a 10 dB return loss was maintained over a 25% bandwidth.

Conductor-loss limited stripline resonator and filters

Abstract: We report on stripline resonators on thin dielectric membranes that show dispersion-free, conductor-loss limited performance at 13.5 GHz, 27.3 GHz, and 39.6 GHz. The unloaded-Q (Q/sub u/) of the resonators increases as /spl radic/f with frequency and is measured to be 386 at 27 GHz. The measured results agree well with a new conformal mapping analysis. The stripline resonators are used in a micromachined state-of-the-art planar interdigitated bandpass filter at K-band frequencies. Excellent agreement has been achieved between the microwave model at 850 MHz and the 20 GHz filter. The micromachined filter exhibits a passband return loss better than -15 dB and a conductor-loss limited 1.7 dB port-to-port insertion loss (including input/output CPW line loss) at 20.3 GHz.

Return loss characteristics of optical fiber connectors

Abstract: This paper describes the return loss characteristics for four typical contact type connectors: perpendicular and oblique endface connectors employing either physical contact or contact via index matching material. The high index layer on the polished fiber endface and the index matching material, which are important connector parameters, are investigated by measuring the return loss from one perpendicular fiber endface coated with the material and by etching the fiber endface. It is useful to apply two materials with different refractive indices to derive the refractive index and thickness of high index layers on perpendicular fiber endfaces. The index matching material we use has a refractive index of 1.467 at 20/spl deg/C and a thermal coefficient of -2.9/spl times/10/sup -4///spl deg/C at 1.3 /spl mu/m. We performed return loss calculations and experiments of the four contact type connectors. The worst value at any temperature from -40 to 80/spl deg/C can be estimated, by measuring the return loss of these connectors at room temperature.

System and method for transmission system automatic impedance matching

Abstract: A system and method having automatic selection of impedance values for matching against unknown line impedances. The method stores an expected set of desired return loss measurements at given frequencies and matches the calculated set against the actual measured return losses to arrive at a close approximation of the line impedance. The system is then adjusted based upon this determined close approximation. The starting point for the stored set are standard models established for each network. In situations where the actual varies greatly from the predicted, a different model is selected and the expected scores for that model are used.

Primary Surge Protector for Broadband Coaxial System

Abstract: A surge protector is adapted for a broadband coaxial system in which electrical signals having a frequency range from DC to one gigahertz are transmitted. The surge protector has a pair of coaxial cable connectors, a surge protection device, and a fail-short mechanism. The fail-short mechanism has a first operating condition in which the center and outer conductors of the coaxial cable connectors are isolated from each other and a second operating condition in which the center and outer conductors of the coaxial cable connectors are conductively coupled to each other. The impedance of the fail-short mechanism allows the surge protector to have an insertion loss with a magnitude not greater than about -0.2 decibels and a return loss having a magnitude of at least about -20 decibels, and the fail-short mechanism is adapted to conduct a fail-short current having a magnitude of at least about 30 amperes for at least about 15 minutes when the fail-short mechanism is in its second operating condition.

Light modulator module and method for fabricating light modulator module

Abstract: A light modulator module includes a submount; a semiconductor laser and a semiconductor light modulator having a signal input terminal integrated on the submount, the semiconductor laser outputting laser light and the semiconductor light modulator modulating the laser light in response to a high-frequency signal input to the signal input terminal; a strip line for transmitting the high-frequency signal, the strip line having first and second terminals, the second terminal receiving the high-frequency signal; a terminating resistor terminating the strip line and having opposed first and second ends with the second end being grounded; a first wire connecting the signal input terminal of the semiconductor light modulator to the first terminal of the strip line; and a second wire connecting the first end of the terminating resistor to the signal input terminal of the semiconductor light modulator. In this structure, the inductances of the first and second wires are present between the signal supply and the terminating resistor. When the frequency of the signal is increased, current flowing in the terminating resistor decreases, compensating for an increase in current flowing through the light modulator, whereby the frequency dependence of the total current is reduced. Deviation of impedance from a prescribed value and return loss are reduced.

Accurate radiation and impedance characteristics of horn antennas-a moment-method model

Abstract: A moment-method-model for horn analysis is presented. The generalized reflection matrix of the aperture is determined using the spectral Galerkin method. The reflection matrix is then combined with the generalized scattering matrix of the horn to yield the input return loss and the aperture fields of the horn. It is shown that the model can predict the radiation characteristics more accurately than the models commonly used in practice.

Design and performance of an angled physical contact type multifiber connector

Abstract: An angled, physical contact type multifiber connector is developed on the basis of a structural design which enables direct fiber endface contact between multifiber arrays. The direct contact is achieved by utilizing the elastic nature of a ferrule material under compressive force. The fabricated connector provides a low insertion loss of 0.2 dB and a high return loss of 58.8 dB without index-matching. This connector is used in the successful development of push-on type and backpanel type 16-fiber connectors with a low insertion loss of 0.25 dB and a high return loss of 58.0 dB for future subscriber networks.

Improved CPW to slotline transitions

Abstract: The paper presents a new approach for designing an ultra broadband coplanar to slotline transition. The procedure is carried out in three steps: design, modeling and fabrication of two new broadband uniplanar CPW to slotline transitions, in the 1 GHz to 50 GHz frequency range. The advantages of these transitions are discussed. Both transitions are modeled using one approach which consists of building a model, based on physical considerations, that is compatible with usual CAD software (discontinuities effects are not taken into account except short/open circuits-end effects). This allows the design and optimization of very broadband transitions in uniplanar technology. The overall agreement between the measured and modeled insertion-loss and return-loss of two back-to-back transitions is good. A maximum relative bandwidth of 7.7:1 is achieved with 10 dB return loss, and the corresponding insertion loss is less than or equal to 2 dB.

High frequency measurement of multilayer ceramic capacitors

Abstract: The monolithic ceramic capacitor (MLC) is small and has good high frequency performance. It is used in various high frequency circuits for impedance matching, DC block, filter and bypass functions. For the best performance in these applications, low equivalent series resistance (ESR) and equivalent series inductance (ESL) is required. We have developed the testing method to compare the performance of different MLC designs to find out the effect on the ESR and ESL. In order to measure the high frequency performance accurately, we have developed a test fixture using the microstrip design. The fixture has a return loss of greater than 30 dB and the insertion loss is less than 0.5 dB. The MLC is mounted on the microstrip fixture and the return loss (RL) and the insertion loss (IL) is measured. A network analyzer is used to compensate for the fixture to obtain good data up to 15 GHz. Using this method, we compare two designs for microwave power applications and two designs for high speed digital applications. We have developed the ultra small capacitor that has good performance in high speed digital circuits.

A DC-to-100-GHz InP HEMT 1:2 distributor IC using distributed amplification

Abstract: The authors describe a 1:2 distributor IC for future very-high-speed optical communication systems. Wideband performance is obtained by applying a distributed amplification technique to a differential circuit. This IC uses a 0.1-/spl mu/m-gate-length InAlAs-InGaAs-InP HEMT and coplanar waveguide technology. It has a 3-dB bandwidth of 100 GHz with a low frequency gain of -2.5 dB. Up to 100 GHz, return loss and isolation are better than -10 dB and -20 dB, respectively. The authors believe the bandwidth is the widest ever reported for multi-RF-port wideband IC's.

Light return loss measurement system and method

Abstract: A light return loss measurement method and system with an optical time domain reflectometer (OTDR) which displays an output of an arithmetic circuit. The method and system permits measurement of the light return loss over an arbitrary interval of an optical fiber. The system's arithmetic circuit calculates light return loss across a measurement interval set in a display waveform data by dividing a predetermined light return loss and integrating the measured waveform by multiplying the set interval by a light interception correction constant. The integration performed is a quadrature of various sections of an optical fiber. The light return loss measurement method and system also permits easy calibration of the light return loss in the OTDR.

An optimised waveguide to microstrip transition at K band

Abstract: An improved transition from rectangular waveguide to microstrip is presented. This transition consists of a ridge waveguide transformer with the ending step extending over the microstrip and two side grooves which maintain the microstrip in its correct position, ensuring both a good electrical contact without soldering and an optimum measurement repeatability. In addition to step ridges, used for matching purposes, also the main guide is stepped in the wider side in order to obtain a single-mode operation in all sections of the transition. The transition is analysed by a full wave mode-matching method and optimised over the 17.7-19.7 GHz band. Measurements are performed in back-to-back configuration using a TRL calibration and the scattering matrix of a single transition is obtained using a de-embedding technique. Experimental results agree well with theory and measured return loss is better than 28 dB over the 16-20 GHz frequency band.

High frequency modeling for 10 Gbps DFB laser diode module packaging

Abstract: In packaging the laser diode several electrical requirements must be satisfied. The conventional packaging method which consists of transmission line, matching resistor and wire bonding interconnect showed good result for the modulation bandwidth requirement of greater than 10 GHz. However the return loss requirement was not content with less than -10 dB. To analyze the effects of package parasitics on return loss, we proposed a small signal circuit model of a laser diode module. From the small signal measurement data, we obtained the small signal circuit model of the laser diode for each bias current, which contains package parasitics and intrinsic laser diode characteristics. Considering both the intrinsic laser diode characteristics and total parasitic effects of the packaged module, the overall frequency response of the laser diode module was simulated and compared to the experimental results. The simulation results on the small signal modulation bandwidth and return loss showed a good agreement with measurements. However, the return loss does not meet the requirement for 10 Gbps laser diode module. Therefore, the wire bonding effect on the return loss was analyzed. The characteristics of wire bonding inductance which affect the return loss were simulated using an interconnect analysis program. As a result, shorter wire bonding length would be the best step to reduce the package induced inductance.

Micromachined thermocouple microwave detector in CMOS technology

Abstract: This paper presents the design and testing of a thermocouple microwave power detector fabricated through a commercial n-well 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 ranging from -30 dBm to +10 dBm. The device has linearity better than /spl plusmn/0.4% for output vs. input power over the 40 dB dynamic range. Measurements of the return loss, obtained using an automatic network analyzer, show an acceptable input return loss of less than -20 dB over the entire frequency range. The sensitivity of the detector was measured to be (1.328/spl plusmn/0.004) mV/mW.

Method and system for controlling echo return loss using a complementary variolosses in transmit path

Abstract: A telephone terminal having handsfree functionality is provided with an audio system which controls echo return loss while permitting virtual full-duplex operation. The system, which has a variolosser in both the transmit and receive path and an acoustic echo canceller, also has a complementary variolosser which introduces additional echo return loss only when required and as a function of the state of the system.

Characterization of microstrip patch antennas suspended by a dielectric superstrate with high permittivity

Abstract: The impedance and radiation characteristics of a coaxially-fed microstrip patch antenna suspended by a dielectric superstrate with high permittivity are extensively studied based on the spectral-domain moment method. As for the case of a dielectric superstrate (/spl epsiv//sub r/=10.5) with 7 types of thicknesses, the complicated variation of its characteristic such as the resonant frequency, the excitation efficiency of radiation fields and surface-wave fields, the input impedance and the radiation pattern, with intervals of the air-layer, are theoretically demonstrated, while some fundamental experiments on the resonant frequency and the return loss are performed to confirm the predicted results.

Single-mode multifiber connector design and performance

Abstract: A low-loss, low-reflection, and stable single-mode multifiber connector design method has been established. The 12 fiber single-mode dry connector exhibited an average connecting loss of 0.17 dB and over 55 dB return loss. The low loss connection is realized by eliminating the plug slipping offset caused by the lateral component of the plug mating force. To realize stable connector performance, the fiber "Direct contract" structure with the fiber protruded connector surface is designed and design parameter is specified. In addition, from the fiber eccentricity distribution function, the connector loss distribution has been estimated analytically.

A wideband waveguide transition design with modified dielectric transformer using edge-based tetrahedral finite-element analysis

Abstract: A waveguide transition analysis approach has been established to deal with arbitrary shaped three-dimensional (3-D) waveguide discontinuity problems, by hybridizing the edge-based tetrahedral finite-element method for the junction region and the analytic modal expansion technique for the waveguide region Several unique features have been imbedded in the analysis, including a variational formula for the scattering coefficients, a modified Delaunay triangulation for the mesh generation, and a frontal solution technique for the sparse matrix solution As a result, the analysis is verified to be accurate, versatile, and efficient through extensive comparisons with the theoretical and measurement data in the available literature The approach is then applied to design a rectangular to dielectric-filled circular waveguide transition with less than -20 dB return loss over a 40% bandwidth by using a suitable modified dielectric rod transformer

Arbitrarily-Shaped Slot-Coupled Microstrips and Their Applications in Microwave Integrated Circuits and Antennas

Abstract: The mixed-potential integral equation (MPIE) is solved by the method of moments in order to investigate arbitrarily-shaped slot-coupled microstrip discontinuity problems. A concise expression of the mutual coupling matrix element is utilized to assure numerical efficiency and accuracy. Comparison between this MPIE and other moment methods (such as MFIE and EFIE) is also carried out and discussed. In order to validate this modeling tool, a circularly polarized dual slot-coupled patch antenna and a single slot-coupled directional coupler arc investigated. Good agreement between numerical results and measurement is achieved. Two examples of dual slot-coupled patch antenna and annular ring slot antenna with microstrip line feed arc designed to provide desired circularly polarized radiation. In addition, a weak coupling slot-coupled directional coupler is designed by utilizing a pair of circular slots. Good performance for directivity, isolation, and return loss is obtained.

Performance of 1Vlicromechanical Tuning Elements in a 620 GHz Monolithic Integrated Circuit

Abstract: The submillimeter wave performance of micromechanical tuning elements called sliding planar backshorts (SPB's) is demonstrated in a quasi-optical monolithic integrated circuit. A substrate-lens is used to focus incident radiation onto a circuit consisting of a full-wave resonant slot antenna and a thin-film bismuth detector, joined by coplanar waveguide (CPW) transmission lines with integrated SPB's. The CPW lines act as tuning stubs with electrical lengths which can be varied by mechanically adjusting the position of the SPB's. Two SPB's are used, one to create a variable series reactance in between the antenna and detector, and the other to create a variable susceptance in parallel with the detector. Microwave measurements for a scale model of the SPB show it to have a return loss of as little as 0.02 dB, and less than 0.5 dB over a 30% bandwidth. Measurements at 620 GHz indicate that the micromechanical SPB's perform consistently with the model, and the two tuning elements are used to vary the response of the detector over a range of nearly 15 dB. The impedance matching capability provided by the SP13's allow a circuit of this type to accommodate a wide range of planar submillimeter wave antennas and devices without advance knowledge of their exact electrical characteristics. Such tuning elements can be useful for characterizing components in developmental circuits, and for optimizing the in-use performance of various submillimeter wave integrated circuits.

Optoelectronic tuning of microwave stub line

Abstract: The authors report a new optoelectronic technique for tuneable microwave matching. It is based on the illumination of a DC biased microstrip resonator on a silicon substrate. The matched frequency is tuned e.g. between 5 and 7 GHz, with a return loss over 45 dB, by varying the optical power and the DC bias.

A novel microstrip-fed multi-segment dielectric resonator antenna

Abstract: This paper investigates a novel multi-segment dielectric resonator antenna (DRA). The antenna consists of a thin segments of different permittivity material bonded to the underside of a rectangular dielectric resonator segment. The multi-segment DRA element is excited by a microstrip line. The permittivity and thickness of the segments are used to concentrate the fields of the micro-scrip line and enhance the coupling from the line to the dielectric resonator segment. Experimental results are presented on a two-segment DRA consisting of a thin segment of high permittivity bonded to a dielectric resonator segment of low permittivity. Without the high permittivity segment, coupling from the microstrip line to the DRA is quite weak, achieving a return loss of only 5 dB. With the high permittivity segment, a maximum return loss of 24 dB was achieved with a 10 dB return loss bandwidth of 17%.

Optimization of aperture coupled patch antenna element for mobile communication applications

Abstract: We discuss the optimization and design of a single-layer, single-patch antenna element for base station array antennas. Such an element should have a minimum of 10% bandwidth and preferably a return loss of 20 dB or more. The antennas used in base stations for mobile communications usually consists of linear arrays of radiating elements in order to achieve the desired pattern: narrow beamwidth in the vertical plane and a broad beam in the horizontal plane. Other aspects of the pattern are also important: constant beam peak angle over the frequency band (i.e. no beam squint), suppression of sidelobes above the main beam and null-fill below the main beam to ensure coverage close to the base station site. For the array to meet these requirements over the frequency bandwidth, it is important to maintain good control over the phase and amplitude distribution to the elements. Furthermore, due to the high power used and the increasing demand for low intermodulation levels, the use of power dividers which provide isolation between the output ports, such as the Wilkinson divider or the 90/spl deg/ hybrid, is very limited. Therefore, any impedance mismatch at the elements will disturb the power distribution of the array and degrade the pattern. The above considerations means that the usual patch antenna designs presented, where a VSWR<2 over the band, are inadequate for use in a base station antenna array. In fact, even if an input VSWR of 1.5 (14 dB return loss) is acceptable for the array, the elements should preferably be matched to a 20 dB return loss to ensure pattern stability.

A COMPACT MMIG~-COMl'ATIBI.~E MICROSTRIP TO WAVEGUIDE TRANSITION

Abstract: A new type of microstrip to waveguide transition is presented, based on slot coupling and a dielectric quarter wave transformer. For a return loss of 20 dB, a relative bandwidth of 16 % was achieved. The structure is compact, MMIC-compatible and can be made hermetic.

A 40db gain single chip pulse amplifier for particle detection

Abstract: A very high gain front end amplifier for detection of cosmic rays in nuclear physics has been realised with the 0.5 ?m GaAs MESFET technology of the Alenia foundry. Because of its higher gain than 40 dB in the 50 MHz - 1 GHz band it can be considered an example of successfull integration of a very high gain circuit into GaAs monolithic technology, demonstrating the effectiveness of GaAs for readout electronics of radiation detectors. Being an active matching amplifier for 50 ohm input-output environment, with more than 20 dB of return loss, it can be applied everytime a low impedance readout is mandatory, and it has been also tested in data communication systems with optical or cable links.

Otdr measuring optical return loss

Abstract: PURPOSE: To provide an OTDR for easily determining the optical return loss in an arbitrary section of an light ray path taking into account of optical return loss due to backscattered light irrespective of whether any optical connector is present or not CONSTITUTION: In an OTDR computing and displaying the attenuation of lighting reflection in a measurement section, the known optical return loss of an optical fiber for calibration work is set in an optical return loss inputting circuit 10 and, at the same time, the optical fiber for calibration is connected to the OTDR to measure the optical return loss The measured value is used to divide the known optical return loss set in the above circuit 10 by an arithmetic circuit 8 to obtain the correction for the received light gain Next, an optical fiber of the light to be measured 4 is connected to the OTDR and an arbitrary section is set by a marker point inputting circuit 9 The arithmetic circuit 8 integrates the data of measured waveform in the set section with distance to determine the optical return loss, which is multiplied by the correction for received light gain to display the optical return loss R of the optical fiber to be measured in the section set by the marker point inputting circuit 9

A high-pass/lowpass phase shifter with resistive matching networks

Abstract: This paper proposes a high-pass/lowpass phase shifter with improved reflection and phase-shift characteristics using resistive matching networks. The circuit configuration, reflection characteristics, phase-shift error-reduction methods, and the design results are described. The relationship between the reflection of the single-pole, double-throw (SPDT) switch and the phase-shift error is discussed in the high-pass/lowpass phase shifter using filters to switch the SPDT switch. The reflection of the SPDT switch caused by the parasitic resistance of the switching device is investigated, and an impedance matching method using the resistive matching networks is proposed to reduce reflection. The calculation results for an S-band phase shifter with the resistive matching networks show that the matching can be achieved even for switching devices with resistance and that the phase-shift error can be reduced. An S-band, 90° single-bit phase shifter has been designed and a low return loss of better than 19 dB and a phase-shift error of less than 4° are achieved, which confirms the usefulness of the resistive matching networks.