A Discriminator-Stabilized Microstrip Oscillator (Short Papers)

A 5.2-GHz microstrip Gunn oscillator has been frequency stabilized by means of a novel microstrip discriminator and integrated feedback loop. A stabilization factor of 1000 was measured for the oscillator with art external Q of 50. The self-capture bandwidth of the discriminator circuit is large enough to eliminate the need for a search voltage to obtain initial frequency locking.     

A New Microstrip Dispersion Model (Short Papers)

A new unified analysis technique is presented for dispersion in microstrip at high frequencies. The technique exploits the fact that the dispersion in microstrips is due to coupling between a surface-wave mode and the LSE mode of an appropriate model of the microstrip. The analysis uses an effective dielectric constant (EDC) approach to evaluate the mode coupling in the LSE model. Unlike previously reported models, all the parameters of the model are exactly determined from the quasistatic parameters of the microstrip, which takes the fringing field into account. Approximate closed-form equations are derived for the prediction of microstrip dispersion. The results agree within 1.50 percent with the experimental and previously published data over a wide useful range of microstrip dimensions and substrate permittivities.     

A Magnetically Tunable Microstrip IMPATT Oscillator (Short Papers)

Magnetically tunable resonators have been constructed in microstrip on a ferrite substrate. A large tuning range is obtained with an external magnetic field applied in the direction of the RF propagation, 17 MHz/Oe for magnetic fields from 0 to 30 Oe. A variable frequency microstrip oscillator which uses this effect is described; measurements made on an X-band IMPATT oscillator illustrate a tuning range from 9.4 to 10.5 GHz with an output power of 330 mW /spl plusmn/ 0.5 dB.     

A Dominant Mode Analysis of Microstrip (Short Papers)

A computer-aided numerical analysis of the dominant mode propagating in microstrip transmission line is reported, and the theoretical results are corroborated by experimental measurements. A region of almost complete circular polarization is found to exist at the surface of the dielectric, although most of the energy is concentrated directly beneath the strip conductor where the fields possess almost complete linear polarization.     

Coaxial Impedance Inverter Design (Short Papers)

It is shown that the effects of discontinuity capacitances associated with the abrupt change in the center conductor diameter of a coaxial bandpass filter can readily be anticipated at the designing stage.     

Octave-Band Microstrip DC Blocks (Short Papers)

The design of octave-bandwidth microstrip interdigital dc blocks is presented. Data for a 7.75- to 16.3-GHz design are given and correlated with an approximate equivalent circuit based on even and odd mode propagation in coupled microstrip. Additional data are tabulated reflecting the ability to shift the frequency band of operation.     

Multilayer Microstrip Transmission Lines (Short Papers)

A method used to treat covered microstrip is extended to multilayer microstrip. Detailed results are obtained for the general three-layer problem. Series expansion and term-by-term integration are used to obtain a closed form expression for the Green's function. Matrix methods are then used to obtain the characteristic impedance. Data obtained agree closely with experiment.     

Dispersion of Parallel-Coupled Microstrip (Short Papers)

Dispersion predictions for the even and odd modes of parallel-coupled microstrip obtained by using the LSE-mode model for microstrip are found to be in good agreement with recently published measurements. Both the basic dispersion relationship and the empirical factor G appear to be the same as for single microstrip lines if the even- and odd-mode impedances used are those of the total parallel-coupled configuration rather than those of a single line of the coupled pair.     

The Microstrip Double-Ring Resonator (Short Papers)

The resonance frequencies and the fields of a microstrip double-ring resonator are discussed. It is shown that no pure even or odd mode can be excited on the resonator. Therefore it is concluded that the rnicrostrip double-ring resonator principally cannot be used to measure the phase velocities of the even and the odd modes on a coupled microstrip line.     

A Note on Green's Function for Microstrip (Short Papers)

The electrostatic Green's function for the open or covered microstrip line is obtained by an integral representation of the free space Green's function, the results of which may be applied to obtain approximately the characteristics of the lowest order "quasi-TEM" mode of microstrip.     

A Potential Theory Method for Covered Microstrip (Short Papers)

Matrix methods are used to analyze the properties of covered microstrip. The Green's function is calculated by a potential theory method assuming the TEM mode of propagation. Computed impedance values of covered microstrip agree closely with other experimental and theoretical data. The technique is a general one and can be used to treat multiple-layer and covered microstrip.     

A New Integrated Waveguide-Microstrip Transition (Short Papers)

A new waveguide-microstrip transition is described. This design provides wide-band performance (18-26 GHz) and very good reproducibility without the need for variable elements. The circuit is fully integrated on the substrate and the characteristics are much less sensitive to small variations in the dimensions than other known transitions. A narrow-band version has been made for the telecommunication band in particular (17.7-19.7 GHz) with a VSWR less than 1.1 and an attenuation less than 0.25 dB. The design can easily be scaled to other frequencies and is especially useful at frequencies above 10 GHz.     

Dielectric Loss in Microstrip Lines (Short Papers)

A new technique is presented for calculating dielectric loss in microstrip lines. Numerical results for several different substrates are included. These are compared with other available results and experimental data.     

Tapered Asymmetric Microstrip Magic Tee (Short Papers)

The design, development, and construction of a very compact decade-(1-10-GHz) bandwidth microstrip --8.34-dB coupler are described. Calculations are given for the voltage coupling coefficient and the low-frequency cutoff, and the method of determing the physical dimensions of the circuit is described. Also, the feasibility of a decade-bandwidth microstrip magic tee by cascading two -- 8.34-dB couplers is demonstrated by comparing the actual and theoretical results of a coupler.     

Loss Considerations for Microstrip Resonators (Short Papers)

The influence of radiation losses on the Q of microstrip resonators is shown for a variety of frequencies, characteristic impedances, substrate materials, and thicknesses. Radiation becomes a dominant factor at higher frequencies, especially for low-impedance lines and thick substrates with a low dielectric constant.     

Loss Calculations of Coupled Microstrip Lines (Short Papers)

Loss calculations have been performed to yield useful data relevant to the complementary odd and even modes propagating along a pair of identical coupled microstrip lines. The calculations are based on methods applied to the single-line case and indicate substantial differences in attenuation occurring between the odd and even modes for particular geometries.     

Very Large Impedance Steps in Microstrip (Short Papers)

Experimental determination of an equivalent circuit for very large impedance steps in microstrip is described. The equivalent circuit is shown to be valid in the frequency range from 1 to 2 GHz on 0.0635-cm-thick alumina substrate, although the experimental method used is applicable to any frequency range and any geometry.     

Conduction and Radiation Losses in Microstrip (Short Papers)

Losses in microstrip on fused-silica and alumina substrates have been experimentally evaluated for various values of stripwidth. Radiation losses in circuits, commonly used for measuring losses in microstrips, depend on the dimensions of the circuit and affect the total losses considerably. Radiation and conduction losses of open-ended line resonators have been separately determined. These measurements have also drawn attention to discrepancies between published theories and our experiments. The effect of surface roughness upon conduction losses has been measured.     

Mode Chart for Microstrip Ring Resonators (Short Papers)

A universal mode chart for the microstrip ring resonator, based on a radial waveguide model, is presented. The resonant frequency is related to the width of the ring conductor. Experimental results from 4 to 16 GHz are shown to be in good agreement with the theory.