Phase-Matched Waveguide Using the Artificial Anisotropic Structure and its Application to a Mode Converter (Short Papers)

Phase matching by the artificial anisotropic structure and its application to a mode converter are proposed for millimeter-wave dielectric circuitry. A phase-matched dielectric planar waveguide is designed and mode conversion characteristics are studied. An experimental result of the nonreciprocal mode converter are presented to show the usefulness of the structure.     

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.     

Metallic Frame Beam Waveguide (Short Papers)

Experimental tests performed on metallic frame beam waveguides are described. Two types of metallic structures have been considered. The first one constituted by thin annular frames has the same attenuation value as that of an iris beam waveguide (infinite slit) of the same aperture, but presents guiding properties which are polarization sensitive. The second type of a more complex structure is essentially a dielectric frame beam waveguide in which the dielectric of suitable refraction index is simulated by metallic parallel plate waveguide sections.     

Mixed Mode Filters (Short Papers)

Mixed mode bandpass filters are described which utilize alternating TE/sub 011//spl deg/ and TE/sub n11//spl deg/ circular waveguide cavity modes. This novel filter configuration exhibits both excellent unloaded Q and spurious mode response characteristics. The use of mixed resonant modes makes possible the design of microwave filters for both in-line side wall connected cylindrical resonators as well as folded planar filter configurations, whereby cross-coupling between selected resonators can be realized.     

Double-Amplification Mode Maser (Short Papers)

A chromium-doped rutile traveling-wave maser utilizing simultaneously two signal frequency transitions has been designed and a prototype section tested.     

An Expansion for the Fringing Capacitance (Short Papers)

The first twelve terms in an expansion of the "approximate fringing capacitance" in powers of exp (-pi s/b) are given explicity as functions of t/b. Comparison with exact values shows agreement within 0.06 percent for s/b /spl ges/ 0.2 and t/b /spl les/ 0.5. In the extreme case considered, s/b=0.1 and t/b= 0.5, the error is less than 2.3 percent.     

An Improved Solid-State Noise Source (Short Papers)

An improved solid-state noise source is discussed. By implementing such modifications as 1) heat sinking of a silicon avalanche noise diode, 2) proper dc RF decoupling, and 3) impedance matching, the stability of the National Bureau of Standards (NBS) solid-state noise source is improved significantly over that of typical commercial solid-state noise sources. These modifications, how they are implemented, and the resulting improvement in stability are described.     

Q-dependence of Gunn Oscillator FM Noise (Short Papers)

Measurements of FM noise and the external quality factor Q/sub ex/ of X-band Gunn oscillators are reported which show that both unconverted and intrinsic FM noise vary inversely as Q/sub ex/, if bias voltage, RF power, and frequency are kept constant.     

General Noise Analysis for Bias- and RF-Voltage-Dependent Transferred-Electron Devices (Short Papers)

The general AM and FM noise spectrum analysis of Sweet for transferred-electron devices is extended to include the variation of device admittance with both bias- and RF-voltage amplitudes. This is important because recent investigations by the author suggest that there are significant variations of device admittance with both parameters. Also the expressions for the AM and FM noise spectra are formulated in terms of the more basic quantities such as stored charge, modulation sensitivities, and incremental admittance.     

Reduction of the Attenuation Constant of Microstrip (Short Papers)

Modifications to a normal microstrip transmission line are proposed, with the aim of reducing the attenuation constant of the line. The results of a computer analysis of a structure containing multilayers of dielectric show that significant reductions in attenuation appear possible.     

Beam Waveguides with Minimized Dielectric Structures (Short Papers)

An experimental study of dielectric beam waveguides with minimized dielectric structure is presented. Such structures are derived from the square-frame beam waveguide described elsewhere. The experimental results show that even very much reduced structures maintain guiding properties. In particular, the helix structure results are competitive with the complete-frame beam waveguide.     

Pump Noise Transfer in Parametric Amplifiers (Short Papers)

Pump noise transfer in paramps is related to the sensitivity of amplifier gain to AM and FM pump modulation. Measurements performed on an S-band paramp with an 18.4-GHz pump are described. The significance of the results is made explicit by using them to calculate the increase in amplifier noise temperature associated with an IMPATT oscillator pump.     

Local-Oscillator Noise Cancellation in the Subharmonically Pumped Down-Converter (Short Papers)

The noise power at the IF output of a superheterodyne mixer which is caused by local-oscillator noise can be significantly reduced by using the recently developed subharmonically pumped down-converter. In many cases this reduction is so large that even noisy sources, such as IMPATT oscillators, can be used to pump low-noise mixers without causing significant degradation of noise figure.     

Circular Bends in Dielectric Frame Beam Waveguides (Short Papers)

An investigation is described on circular bends in beam waveguides constituted by dielectric frames. A uniform bending of the guide axis is obtained by tilting each frame by a small angle; however, due to the phase correction performed by the dielectric frame, the losses introduced by the bending can be made lower than those of an analogously bent iris waveguide. A numerical analysis is performed on the basis of the analogy between beam waveguides and open resonators which permits the assessment, in a number of cases, of the maximum permissible amount of tilting and the corresponding optimum frame dimensions in view of acceptable losses. The losses due to mode conversion are also evaluated when considering the connection between a straight and a curved section of the waveguide.     

A Reference Noise Standard for Millimeter Waves (Short Papers)

The WR15 thermal noise standard that is used as the national reference standard of noise power in the frequency range from 56 to 64 GHz is described in this short paper. The source forms a basis for both the noise-power comparison service and noise-figure service offered by the National Bureau of Standards in this frequency range.     

Avalanche Diode Noise Sources at Short Centimeter and Millimeter Wavelengths (Short Papers)

Semiconductor noise sources for microwave frequencies have been constructed using commercial avalanche diodes in waveguide mounts. For the diodes and waveguide configurations reported here the upper usable frequency is approximately 40 GHz. The measurements are in limited agreement with previous predictions. It is possible that a reduction in package and diode parasitic would improve this agreement, and raise appreciably the upper usable frequency of such noise sources.     

Finite-Boundary Corrections to the Coplanar Waveguide Analysis (Short Papers)

Conformal mapping calculations of impedance and effective dielectric constant are presented for coplanar waveguide (CPW) lines with finite-substrate thickness. These calculations and experimental data show a departure from the intinite dielectric approximation as the substrate thickness approaches the guide slot width. The quasi-TEM approximation is retained and calculations of static energy density within the substrate are given. This approximation agrees well with field calculations using a finite-element solution to Laplace's equation.     

The Circular Waveguide Step-Discontinuity Mode Transducer (Short Papers)

Power conversion coefficients and the launch phase of propagating modes excited by a symmetric step-discontinuity in circular waveguide are accurately predicted by a modal analysis of the discontinuity which includes only a few evanescent modes. The relative power in transmitted and reflected propagating modes is presented as a function of normalized frequency for two step-discontinuity ratios to indicate typical solution results.     

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.     

High-Order Mode Cutoff In Rectangular Striplines (Short Papers)

The higher order mode cutoff characteristics of rectangular stripline structures, with thin center conductors, are discussed. Data are given, using an alternative method of presentation, on the normalized cutoff of the first eleven higher order modes. Discussions are included on the physical reasons why cutoff is aftered for some modes, relative to that in rectangular waveguides, but not for others.