Microstrip Line Circuit Research Articles

A simple method for blocking parasitic modes in a waveguide-packaged microstrip-line circuit

A simple structure formed by two metal patches symmetrically deposited at the two sides of the center microstrip is proposed and analyzed for blocking the higher order modes in a waveguide-packaged microstrip-line circuit. The variations (with the patch width) of the effective dielectric constants and field distributions of the modes in the packaged microstrip line with infinitely long side patches were first investigated using the two-dimensional (2-D) finite-element method (FEM) and the method of lines. The results suggested that there exists a range of patch widths at which the field distributions of the higher order modes are totally different from those of the microstrip line without side patches. The scattering of the patches as a function of the patch length and width was then studied using the three-dimensional (3-D) FEM with edge elements. It has been found that by simply choosing appropriate patch sizes, the parasitic higher order mode can be reflected without sacrificing the normal propagation of the dominant mode.

Behaviour of Parallel Coupled Microstrip Band Pass Filter and Simple Microstripline due to Thin-Film Al2O3Overlay

The X-band behaviour of a seven-section parallel-coupled microstrip band pass filter and microstripline due to thin-film Al2O3overlay of different thickness is reported in this paper. This Al2O3film can give a homogeneous overlay structure. There is a substantial increase in the bandwidth due to the overlay, the pass band extending towards higher frequency side. In most of the cases, an increase in the pass band transmittance of a microstripline also increases due to a thin-film Al2O3overlay, especially for frequencies less than 9.0 GHz. At higher frequencies, random variations are observed. It is felt that thin-film overlays can be used to modify the microstripline circuit properties, thereby avoiding costly and time consuming elaborate design procedures.

Traveling wave electro-optic phase modulator using cross-linked nonlinear optical polymer

We report the fabrication and characterization of a high frequency traveling wave electro-optic phase modulator made from thermally cross-linked polyurethane-Disperse Red 19 polymers. The device has been fabricated using a three layer structure with an integrated 50 Ω microstrip line circuit. The straight channel optical waveguides were defined laterally by standard photolithography and oxygen reactive ion etching. The measured half-wave voltage was in good agreement with that extrapolated from the second harmonic generation measurements. Optical modulation was observed directly on a spectrum analyzer up to 18 GHz. Long-term evaluation over an extensive length of time found no observable loss of performance.

Effect of metallization process on the performance of passive microstripline circuits

The coupling and isolation of a 10-dB directional coupler, midband rejection of Δ/2 rejection filter, and transmission and reflection coefficients of microstriplines are studied in the X band (8–11 GHz). The circuits are delineated photolithographically on alumina substrates metallized by aluminum and copper using different metallization processes. The adhesion and dc resistivity are also compared. The microwave properties do not show appreciable differences due to the various metallizations, though dc ion plating + electroplating seems to be the best of the lot. It has also been found that aluminum under proper conditions of deposition proves to be as good a conductor for microwave purposes as copper, and in some cases better. It is felt that using ion plating initially to get a thickness of ∼2000 A and then electroplating to 4 μn thickness will be very cost effective, the film having the advantages of the good adhesive property of ion plating and less wastage of costly pure material. © 1992 John Wiley & Sons, Inc.

Transient response of a microstrip line circuit excited by an external electromagnetic source

The transient voltages and currents induced by an external electromagnetic field along a microstrip line interconnecting active and/or passive components are studied by using a distributed-source transmission-line model. The influence of the angle of incidence as well as that of the microstrip geometrical and electrical parameters on the line response is analyzed. The instantaneous voltage and power induced on the loads by various types of pulse excitations are computed. Numerical results are obtained both for dispersive and nondispersive lines. A line feeding a transistor microwave amplifier is also considered. The results show the effects of the multiple reflections of the field inside the dielectric substrate and of the signal at the ends of the line. Indications of how to reduce the coupling between the external field and the considered structure are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A full-band waveguide SIS receiver with integrated tuning for 75-110 GHz

The performance of a broadband SIS (superconductor-insulator-superconductor) receiver with no mechanical tuning elements was modeled and tested. The mixer mount had a broadband-waveguide-to-microstripline transition consisting of a four-step Chebyshev single-ridge transformer. The last step of the ridge connected the waveguide to a microstripline circuit. The on-chip circuit consisted of a microstripline that transmitted the RF and the local oscillator signals to the SIS mixer. Both the SIS element and the inductor had RF grounds provided by 90 degrees radial stubs. The inductor tuned out the junction capacitance to allow operation over the full frequency band. The SIS element can be a single junction or series array using Nb-AlO/sub x/-Nb trilayer tunnel junctions with areas as small as 0.5 mu m/sup 2/ and V/sub m/(2 mV)=39 mV. Preliminary results indicated a DSB receiver noise temperature of 65-80 K across the band measured at 4.4 K with an internal cryogenic RF hot/cold source and with T/sub if/=21 K. With another device, a mixer noise temperature of 35 K at 100 GHz was achieved, increasing to 45 K at 79.5 and 110 GHz. Coupled mixer gain of up to +3 dB and negative dynamic resistance on the first photon step were observed. The lowest noise temperature was obtained for an untuned single-junction mixer at 80 GHz: T/sub R/=41 K and T/sub M/=20 K were measured.

Analysis of coplanar lines utilizing the finite difference time‐domain technique

AbstractThe full‐wave analysis methods in the time domain including the finite‐difference time‐domain method are promising as general‐purpose analysis techniques for three‐dimensional structures. They have been applied extensively to microstrip line circuits; and, in this paper, they are extended to coplanar line circuits and the finite‐difference time‐domain method is applied to the analysis of coplanar lines considered important as the configuration element for uniplanar monolithic microwave integrated circuits (MMIC).The analysis results are presented for the transmission line parameters of the coplanar waveguides and coplanar strips, models for open ends and short‐circuited ends, characteristics of the T‐junction and the effect of the air bridges. Using these analyses, the possibility of applications is proven. In addition, the points to be noted and future subjects are studied so that the method can be extended as a tool for the CAD of the MMICs.

Performance Comparison of Thin and Thick Film Microstrip Rejection Filters

A performance comparison of microstripline circuits using thin and thick film techniques has been studied, in which a Microstrip rejection filter, in the X-band of microwaves, is used as test circuit. A thick film technique is capable of giving good adhesive films with comparable d.c. sheet resistivity, but other parameters such as open area (porosity), particle size, and edge definition are inferior to thin-film microstrip filters. Despite this drawback, the average value of transmission, transmission loss, reflection coefficient, resonant rejection frequency, and quality factor for thick-film filters indicate that screen printed Ag films are intermediate between thin-film1,2,9and etched-thick-film9microstrip filters in performance, making it a feasible method for microstrip circuits.

Crosstalk measurements of monolithic GaAs photoconductive detector arrays in the GHz region

The crosstalk levels among detectors in a monolithic GaAs photoconductive detector array were measured in the frequency range 250 MHz–1.3 GHz. When the array was mounted on a properly designed microstripline circuit, crosstalk levels below −44 dB were achieved at a detector spacing of 100 μm across the entire 1.3-GHz bandwidth. The provision of a ground plane fabricated monolithically with the array was found to be important. The observed −44 dB crosstalk level in the GHz frequency region confirms the feasibility of a completely integrated broadband optoelectronic switching matrix.

Coupled TEM Microstrip Impedance Transformer for S-Band TRAPATT Amplifiers

A coupled TEM microstrip line circuit suitable for use in S-band TRAPATT amplifiers has been investigated. An analytical model of the coupled-line structure has been developed which properly accounts for diode positioning on the line. This model has been used to calculate the fundamental and harmonic impedances at the device terminals for various stub terminations and device locations. Measurements made with a Hewlett-Packard network analyzer are in good agreement with the calculated results. The use of this circuit for the development of a fixed-tuned MIC circuit for the TRAPATT amplifier on Duroid Substrate is discussed. The complete circuit incorporates a bias line filter with this coupled microstrip line and appropiate harmonic tuning stubs at two of its ports. It is capable of providing at least 6-percent 1-dB bandwith with high efficiency and high peak power output over pulsewidths up to 50 mu s and up to 1-percent duty cycle.

860 MHz Low Noise Transistor Preamplifier for Satellite Communication Down Link

This paper describes the design and performance of a low noise 860 MHz transistor preamplifier developed for the down chain of earth stations capable of TASO grade I TV reception. Both lumped components and microstripline circuits have been tried as matching sections at the input and output ports of the transistor, to realize a goal of 25 db gain and noise figure <4·0 db over the frequency range 860±20 MHz. The two-stage amplifier has been designed using the S-parameters of the transistor, the first stage being biased for minimum noise figure and the second stage for maximum gain.The two-stage amplifier using lumped components gives a gain of 20±0·5 db and a noise figure around 3·6 db over the frequency range. The lumped component approach suffers from many distinct disadvantages at UHF and microwaves. Hence microstripline design was taken up. A two-stage amplifier using the same transistors and microstripline circuits was built on Rexolite, 1/32 in. thick, copper clad sheet. A gain of 27·5±0·25 db over t...

A Proposed Circuit Model for Microstripline TRAPATT Oscillators (Correspondence)

Described in this paper is a simple microstripline circuit suitable for supporting TRAPATT oscillations with the Fairchild FD-300 diode. The best result obtained was a pulsed output of 42 watts at 520 MHz with an efficiency of 9 percent. Also presented is a circuit model for predicting the frequency of operation. The resulting theory is shown to be in good agreement with the observed experimental data and provides a useful tool for designing low-frequency TRAPATT oscillators with small dimensions.

Frequency-stable microstripline X-band Gunn oscillator

Microstripline circuits were constructed which control the oscillating frequency of Gunn diodes prepared with various GaAs slices to within ±0.7 percent. An output of at least 17.3 mW is achievable using the circuits and fabrication techniques described.