Showing papers on "Return loss published in 1990"

Fibre optic single mode rotary joint

Abstract: The invention is a rotary joint for singlemode optical fibers, having a fixed and a rotating part to permit the transmission of optical signals across a rotational interface (such as a winch or turret) with minimal insertion loss and, in particular, low reflections (good return loss). There is no need of conversion to electrical signals; the device is passive. It may be use an oil of refractive index matched to that of the glass fibers and to that of fiber tapers or lenses used to expand the beam emitted from one fiber and contract it for transmission into the other fiber. The device is bidirectional. By use foil, through precision techniques for building and mounting the optical and mechanical components, and by use of advanced bearings, both the insertion loss and unwanted reflections (return loss) can be minimized, thereby making it suitable for use with singlemode fiber. Insertion loss can be further reduced in conjunction with index-matching fluid by using optical elements (lenses, tapers, fibers) having angled or curved facets rather than perpendicular facets. Oil filling has the further advantage of pressure compensation allowing the device to operate at any ambient pressure. Lenses having curved surfaces can be accommodated by the use of fluid having a refractive index different from that of the lens material.

Microwave aided balloon angioplasty with lumen measurement

Abstract: A multipurpose catheter apparatus for microwave aided balloon angioplasty includes a balloon capable of being filled with a lossy dielectric liquid, and bearing a metallization pattern. The catheter includes an electromagnetic transmission line. Radio frequency energy applied to the proximal end of the electromagnetic transmission line is radiated by an antenna within the balloon. The metallization pattern causes a portion of the energy applied to the proximal end of the transmission line to be reflected, which affects a characteristic such as impedance, return loss or time of reflection. A measurement apparatus measures the characteristic, and the distention of the balloon is determined from the measured characteristic. A guide filament may extend through the transmission line.

Matching slot pair for a circularly-polarised slotted waveguide array

Abstract: A matching slot pair which radiates all the incident power in a circularly-polarised wave is proposed and analysed for use as a terminal in a leaky-wave slotted waveguide array. The position and size of the slots are numerically optimised to suppress reflection and to realise a desired polarisation in the tilted beam direction, which contributes to improving the antenna efficiency. It is verified experimentally that the return loss is below -15 dB over 0.1 GHz at the 4 GHz band and the 3 dB axial ratio bandwidth is about 5% in the tilted beam direction. >

A minaturized broad-band MMIC frequency doubler

Abstract: A miniaturized broadband balanced MMIC (monolithic microwave integrated circuit) frequency double, composed of a common-gate FET and a common-source FET directly connected to each drain electrode, has been proposed and demonstrated. The doubler is designed and fabricated as a miniaturized function module using a conventional two-gate FET configuration, active trapping, and active impedance matching. The doubler design has been performed through phase error estimation, gate width optimization, and gate-source voltage optimization. The phase error estimation in a nonlinear condition has eliminated phase error compensation circuits. The fabricated chip size is only 0.5 mm*0.5 mm, which is about 1/10 the area of previously reported doublers. A conversion loss of 8-10 dB, a fundamental frequency suppression better than 17 dB, and an input return loss better than 8 dB are obtained in the output frequency range from 6 to 16 GHz. The broadband doubler as a miniaturized MMIC function module can be applicable to small-size oscillator MMICs and multifunction MMICs. >

Low-reflectivity in-line variable attenuator utilizing optical fiber tapers

Abstract: A single-mode inline variable optical attenuator utilizing optical fiber tapers is discussed. Optical attenuation control is achieved through axial separation between two tapers with beveled endfaces aligned within a ceramic sleeve. Increased axial separation causes increased coupling loss between the two taper fundamental modes. Insertion loss of 75 dB with continuous 0.05 dB resolution, and reflection return loss of better than 58 dB have been realized. Theoretical studies indicate low polarization and wavelength dependence, and inherent insertion loss of >

A matching slot pair for a circularly-polarized slotted waveguide array

Abstract: The analysis and the design of the matching slot pair for a circularly polarized slotted waveguide array are described. The position and the size of the slots are numerically optimized to suppress reflection and to realize a desired polarization in the tilted beam direction, which contributes to the improvement of the antenna efficiency. A boundary value problem is analyzed for the matching slot pair taking the wall thickness of a waveguide into account in order to evaluate the phase of aperture fields accurately. The position and the size of the slots are determined on the basis of this analysis. The design is verified by measuring the reflection coefficient, the radiation patterns, and the axial ratio of a model slot pair. It was verified experimentally that the return loss is below -15 dB over 0.1 GHz at the 4-GHz band and the 3-dB axial ratio bandwidth is about 5% in the titled beam direction. >

Optical measurement system

Abstract: An optical measurement system is disclosed which enables rapid and repeatable measurement of insertion and return loss of each fiber in sequence of a multi-fiber connector 15 connected to an optical fiber ribbon 16 to be obtained without disturbing either the light source 17, 18 or detector components 19, 20 of the system The system comprises a multi-channel optical switch 1 for connection to a light source 17, 18; 1×2 bi-directional splitters 2 each of which is optically coupled between one of the channels of the multi-channel optical switch and one fiber of a master multi-fiber connector 3, of which the geometry is known, for mating with a multi-fiber connector to be tested and, for connection to at least one detector for monitoring and recording the power reflected at the interface between a pair of optical fibers interconnected by the mating of the master multi-fiber connector and the multi-fiber connector under test, and a splitter 11 to which each of the bi-directional splitters 2 is also optically coupled

Y branching silica waveguide 1*8 splitter module

Abstract: Silica waveguide Y branching 1×8 splitters were fabricated and found to be highly reliable after housing. The silica waveguide has a splitting excess loss of 0.57 dB. The packaged device has a housing excess loss of 0.89 dB. The measured return loss was over 50 dB above room temperature. The loss deviation under heat cycle testing was 0.46 dB in the temperature range −20 – +70°C.

Microwave frequency agile active filters for mic and mmic applications

Abstract: The purpose of this paper is to present newly developped microwave frequency agile active resonators which, in a planar structure, may be realized using MIC or MMIC technologies. Consisting of a modified Hair pin resonator feedback by an amplifier and a phase shifter, these resonators offer extremely low loss and high Q value resonators. The use of vamctors permits a tuning of the resonant frequency as well as the bandwidth. Using such resonator, a bandstop filter with a rejection of 45 dB and a lossless band pass filter with a return loss of 35 dB have been obtained at 3.1 GHz.

A wide-band prime-focus horn for low-noise receiver applications

Abstract: A horn suitable for a prime-focus antenna requiring low cross polarization, wide bandwidth, and low spillover is described. The design is particularly suited for low-noise applications such as high-quality satellite earth-station antennas and radio telescopes. The horn has a return loss substantially better than 20 dB, a cross polar sidelobe level better than -20 dB, a beamwidth variation of 40% and negligible phase center shift. >

Microwave frequency agile active filters for MIC and MMIC

Abstract: Microwave-frequency agile active resonators which, in a planar structure, can be realized using microwave integrated circuit (MIC) or monolithic MIC (MMIC) technologies are presented. Consisting of modified hairpin resonator feedback by an amplifier and a phase shifter, these resonators offer extremely-low-loss and high-Q-value resonators. The use of varactors permits a tuning of the resonant frequency as well as the bandwidth. Using such resonator, a bandstop filter with a rejection of 45 dB and a lossless bandpass filter with a return loss of 35 dB have been obtained at 3.1 GHz. >

A simple dual-band corrugated horn with low cross polarization

Abstract: A simplified design for dual-band corrugated conical horns with low cross-polarization characteristics is discussed. Measured results of the breadboard horn show that cross-polar levels of better than -34 dB and return loss of better than 28 dB have been realized over the designed frequency bands. It is shown that the performance of the single-depth corrugated horn can be optimized to give low cross-polarization fields over a 40% frequency bandwidth. Cross-polar levels on the order of -34 dB and return loss of better than 28 dB have been realized for the breadboard horn. The designed horn has potential application in direct-broadcast satellite antennas operating in the 12 and 17.5 GHz frequencies. >

DC to 40 GHz MMIC power sensor

Abstract: A GaAs MMIC (monolithic microwave IC) power sensor is presented that has excellent input return loss (>20 dB from DC to 40 GHz), and square law response ( >

High performance millimeter-wave microstrip circulator for deep space communications

Abstract: High-performance microstrip circulators in the Ka-band that utilizes new ferrite substrates and temperature stable magnets have been developed. A special resonator configuration was analyzed, modeled, and optimized. The circulators have isolation and return loss of greater than 17 dB, and an insertion loss of less than 0.6 dB. Test results indicated almost no performance variations over the temperature range of -30 to +60 degrees C. >

Coplanar-waveguide/microstrip probe coupler and applications to antennas

Abstract: A method to couple microwave power from a coplanar waveguide to a microstrip line on opposite sides of a ground plane is demonstrated. The coupler uses a metallic post which passes through an aperture on the ground plane connecting the strip conductor of the coplanar waveguide to the microstrip line. The measured insertion loss and return loss are about 1 dB and 10 dB, respectively, across the frequency range of 0.045-6.5 GHz. To demonstrate potential applications of the coupler as a feeding network for a microstrip patch array, measured radiation patterns of two rectangular patch antennas with a direct coplanar-waveguide/microstrip feed and with a proximity coupled coplanar-waveguide/microstrip feed are presented.

Direct current preventing circuit

Abstract: PURPOSE:To improve the out-band return loss by connecting a circuit consisting of a 1/4 wavelength line, a 1/4 open stub, and a resistance to the root of a parallel coupling line. CONSTITUTION:A circuit obtained by terminating a band rejection type filter circuit consisting of a 1/4 wavelength line 3 and a 1/4 wavelength open stub 4 in terms of a high frequency via a thin film resistance 5 and a capacitor 6 is connected to the root part of a 1/4 wavelength parallel coupling line 1 consisting of a microstrip. The tip part of the line 3 is opened within a band and gives no influence to a main line 2 within the band. However the tip part of the line 3 is terminated by the resistance 5 at a point out of a band especially at a lowfrequency band. Thus the reflected waves caused by the line 1 are absorbed. As a result, the out-band return loss is improved.

Passive 8-16 GHz MMIC image-reject mixer

Abstract: A passive 8-16 GHz MMIC image-reject mixer design is presented. The circuit, fabricated on a 4-mil GaAs substrate, is entirely passive and uses planar Schottky barrier diodes as the mixing elements. The topology is a phase-type configuration using two single-balanced mixers and in-phase and quadrature power dividers on-chip, with an off-chip IF quadrature combiner in the 0.1 ro 1.5 GHz band. This approach results in high process yields and excellent circuit uniformity. The design methodology and experimental results are described. A maximum conversion loss of 8 dB, greater than 20-dB image-rejection, and good return loss and port to port isolations were achieved using an 18-dBm LO (local oscillator) drive and an IF of 100 MHz. >

Waveguide-to-microstrip power splitter

Abstract: A novel coupling structure which permits both power combining and division is described. The structure divides power equally from a rectangular waveguide to two microstrip lines. The microstrips are T-shaped conductor patterns placed symmetrically in the waveguide. The splitter has a return loss of better than 20 dB from 3.3-4.6 GHz measured at the waveguide port. The power difference between the two microstrip output ports is less than 0.1 dB. The coupler is useful for power combining at microwave and millimeter-wave wavelengths with minimal power loss. >

Automation of an optical time domain reflectometer to measure loss and return loss

Abstract: An optical time domain reflectometer (OTDR) is automated to measure transmission loss and return loss of individual faults as well as the entire fiber span. Experimental and field trail results confirm that this technique enables fiber testing and fault locating to be carried out at one location with little or no human intervention. >

A V-Band Wafer Probe

Abstract: In this paper the design and development of a V-band (50-75 GHz) probe is presented. The V-band probe must have a waveguide input, since commercially available coaxial cable has overmoding present above 65 GHz. Design goals: ? Frequency coverage 50-75 GHz ? Insertion loss better than 4 dB ? Correctable performance: (|S11| - |S21| ? 5dB) ? Footprint GSG (ground-signal-ground) ? Pitch availability 50-250 microns ? Biasing ability An insertion loss of less than 4 dB at 75 GHz and correctable performance is desired. Correctable performance implies that there is adequate separation between insertion loss and return loss, allowing meaningful data to be obtained for deriving the error correction model. A difference of 5 dB has been found to give useable results, and is expressed as |S11 - |S21| ? 5dB. The coplanar probe lip will be a ground-signal-ground configuration, with pitch selection available from 50 to 250 microns. The signal line must be able to be biased with respect to the ground contacts for on-wafer deviced characterization. The input is to be a V-band rectangular waveguide with WR-15 flanges.

Waveguide coupling structure

Abstract: PURPOSE: To improve insulation performance and to make return loss satisfactory by supporting a conductive patch inside a waveguide so that it can be orthogonally crossing the axial line, and extending a wired waveguide through a waveguide wall until the position where the wired waveguide is connected to the patch. CONSTITUTION: A conductive patch 3 is supported inside a waveguide 1 so that it can be orthogonally crossing the axial line, and a wired waveguide 4 is extended through the wall of the waveguide 1 until a position at which the wired waveguide 4 is connected with the patch 3. Then, the wired waveguide 4 is extended to the position where it is made adjacent to the patch 3 and it is not brought into contact with it. The wired waveguide 4 is constituted of a strip-shaped part in the same plane with the patch 3, and it is desired that the width of the end part of the strip-shaped part which is made adjacent to the patch 3 is narrow. Thus, high isolation performance and satisfactory return loss can be simultaneously attained against orthogonal polarization.

Millimeter wave monolithic IC's using direct ion implantation in to GaAs LEC substrates

Abstract: Millimeter-wave monolithic ICs consisting of two-stage driver amplifiers and 4-bit phase shifters were fabricated by direct ion implantation into 3-inch diameter GaAs LEC (liquid encapsulated Czochralski) substrates. The monolithic two-stage amplifiers with 0.3-micron gate length, ion-implanted GaAs MESFETs achieve a gain of 9.0 to 10.1 dB from 40 to 48 GHz with a gain of 9.5 dB at 44 GHz. In the same frequency range, the input return loss varies from 9.8 to 11.5 dB and output return loss from 6.6 to 9.0 dB. The 4-bit phase shifters exhibit very accurate phase shift within 3 degrees for 0 to 247.5 states and 4-7 degrees for 270 to 337.5 states at 44 GHz. The insertion loss is 9.4 11.1 dB for all 16 states. The authors concentrate on the results of monolithic driver amplifiers and digital phase shifters at Q-band frequencies. >

A miniaturized, broadband MMIC frequency doubler

Abstract: A miniaturized, broadband balanced MMIC (monolithic microwave integrated circuit) frequency doubler, composed of a common-gate FET and a common-source FET directly connected to each drain electrode, is proposed and demonstrated. The doubler is designed and fabricated as a function module. The chip size is only 0.5 mm*0.5 mm, an area about one-tenth that of the previously reported doublers. A conversion loss of 8 dB, a fundamental frequency suppression better than 17 dB, and an input return loss better than 8 dB are obtained in the output frequency range of 6 GHz to 16 GHz. The broadband doubler as a miniaturized MMIC function module can be applicable to small-size oscillator MMICs and multifunction MMICs. >

Waveform distortion due to near-end reflections in direct detection lightwave systems using single-mode semiconductor lasers

Abstract: Deterministic rate equations describing the nonlinear modulation dynamics of single-mode semiconductor lasers are used to assess the performance implications of external optical feedback for multigigabit-per-second lightwave systems. The rapid increase in the eye closure penalty resulting in a return loss of about 20 dB, is consistent with published experimental data. >

Polarization converter having two converting devices therein

Abstract: Disclosed is a polarization converter (9) allowing one down converter to receive four types of polarizations of a horizontal polarization, a vertical polarization, a right-handed circular polarization and a left-handed circular polarization without deteriorating a pass loss characteristic and a return loss characteristic (VSWR characteristic) of an antenna apparatus as a whole The polarization converter (9) includes a circular waveguide (20) having dielectric plate (8) for converting a circular polarization to a linear polarization, a ferrite pole (10) for changing the direction of the electric field of the linear polarization and a coil (11), all of which are integrally provided therein As a result, the design is easily obtained which optimizes the return loss characteristic (VSWR characteristic) of the entire antenna apparatus, which allows one converter to receive said four types of polarizations without deteriorating the pass loss characteristic and the return loss characteristic (VSWR characteristic) of the entire antenna apparatus

Design of a circular waveguide-to-microstrip coupling probe for a submillimeter-wave application

Abstract: A design that uses a microstrip probe inserted into a circular waveguide and tuned with a noncontacting adjustable short circuit is described. Although the use of a circular (instead of rectangular,) waveguide is restrictive in bandwidth, the coupling probe designed for submillimeter-wave operation should yield a 10% bandwidth with >or=20 dB return loss. The use of a noncontacting short circuit allows the probe to be tuned without the need for electrical contact with the waveguide walls. >

Dual-spiral slot array antenna fed by triplate transmission line

Abstract: The fundamental radiation characteristics of a dual-spiral slot (DSS) fed by a triplate transmission line (microstrip) are presented. The triplate transmission line reduces the antenna thickness. The DSS radiates a circularly polarized wave over a wide range coverage around the Z-axis. An array using 32 DSSs attains a 5% bandwidth for a -14 dB return loss criterion. A DSS array antenna was constructed and tested in the 12 GHz band. >

Ringer detection circuit

Abstract: PURPOSE:To prevent mis-detection of induction in 60Hz and to avoid the reduction in the return loss by providing a nonlinear circuit provided with an impedance means causing a high impedance with respect to a voice signal and a low impedance with respect to a ringer signal. CONSTITUTION:A Tip line of an analog exchange is connected to a DC interrupt circuit 1 and a Ring line is connected to a nonlinear circuit 2. The DC interrupt circuit 1 interrupts a DC component superimposed on a ringer signal fed from the Tip line of the analog exchange, a low pass filter 3 receives an output from the DC interrupter 1 to attenuate the frequency component higher than the ringer frequency. On the other hand, the nonlinear circuit 2 increases the impedance with respect to the voice signal and decreases the impedance with respect to the ringer signal, then the voice characteristic is improved. An output 31 of the low pass filter 3 is rectified by a full wave rectifier 4 and a detection circuit 4 detects the presence of the ringer signal. Thus, mis-detection of 60Hz induction is prevented and the decrease in the return loss is prevented.

Electrical characterization of some materials in the X-band

Abstract: Three classes of materials, i.e. dielectric, semiconducting and conducting materials are considered, where some of their electrical properties are measured at microwave frequencies, i.e. in the X-band (8 to 12 GHz). These include the insertion loss, return loss, shielding effectiveness and the equivalent input impedance. Comparison between these different parameters is made using a set of curves as a function of frequency. The results obtained indicate virtually no unusual behaviour. A maximum shielding efficiency of about 34 dB is found for GaAs limit and lower values are found for the silicon, flexible carbon and dielectric materials. The equivalent input impedance was found to be roughly constant over the X-band for the dielectric and conducting materials while it exhibits a high dependence on frequency for semi-conducting material oscillating between inductive and capacitive.

A full-wave analysis of waveguide T-junction with an inductive post

Abstract: A T-junction with a thick inductive post has been designed for the power combiner/divider of a slotted waveguide array feed. This T-junction is matched by means of a single cylindrical post, placed across the waveguide, parallel to the narrow walls. The design parameters for matching are the position of the inductive post and its diameter. The reflection coefficient of the T-junction with the inductive post is analyzed and minimized, with the diameter of the post taken into account. The analysis is verified by measuring the return loss. The analysis is shown to predict accurately the measured return loss for different diameters of the post. On the basis of this analysis, the position and the diameter of the post are optimized; a return loss below -30 dB is realized over a 5% bandwidth. >