Inductive Strip Research Articles

Invited paper Wave reactance of thin planar strip gratings

ABSTRACT The application of strip gratings as diplexers of electromagnetic waves and also as tools for the construction of models for frequency-selective surfaces has given fresh impetus to deeper analysis of these devices. Rigorous methods of solution for strip gratings usually require considerable computational effort to evaluate the scattering parameters. There is a need for simpler, even if approximate, methods which would provide the solutions faster. This paper briefly describes the analysis of thin planar multielement strip gratings in TE and TM incident waves and mentions some methods that can be used in obtaining the solutions. The Fourier-Galerkin method is described and applied to a regular, as a particular case of a multielement, strip grating to obtain a matrix equation which is solved numerically. Then a number of approximate methods are employed to obtain explicit expressions for the normalized wave reactances of inductive strip gratings in incident TE and TM waves.

Design of Waveguide E-Plane Filters with All-Metal Inserts

Waveguide E-plane filters with all-metal inserts are designed by a procedure based on the reflection coefficients of axial inductive strips. The scattering matrix, representing the junction in a bifurcated waveguide, is calculated by a mode-matching method. The reflection coefficient for an inductive strip is then obtained by cascading two scattering matrices separated by a distance equal to the stripwidth. The design is valid up to moderate bandwidths, except for the narrowband design at the higher waveguide frequency range, where both the center frequency and the bandwidth are inaccurate. Possible sources of error are studied and a method minimizing the error is proposed.

Impedance Calculation of Three Narrow Resonant Strips on the Transverse Plane of a Rectangular Waveguide (Short Paper)

A theoretical analysis has been developed to calculate the impedance of two inductive strips and one capacitive strip located on the transverse plane of a rectangular waveguide. The current ratios among the strips were determined by a variational method and then used for impedance calculations. The results can be applied to the impedance calculations of a single capacitive strip, two inductive strips, or three inductive ships as special cases.

Novel method of compensating shunts for measuring kiloampere pulsed currents

A simple method of compensating an inductive strip shunt is to use another shunt in series with it, with equal inductance but lesser resistance. When the voltages induced in these shunts are subtracted in a compensating circuit, the compensated shunt acts like a pure resistance. A compensated shunt of thin tantalum foil, having an effective resistance of 200 mW, was made.

The development of the Rutherford laboratory MWPC positron camera

The development of a large aperture (30 cm × 30 cm) positron camera is described. It is based on the particular hybrid MWPC structure developed at the Rutherford Laboratory ∗ ∗ This apparatus is covered by British Patent number 26595/77. which consists of multiple MWPC detectors with laminated metal cathode foils which function simultaneously as converters for the 511 keV positron annihilation gamma rays and inductive readout strips. The solutions found for the many structural and electronic problems encountered in the design are described. Results are presented showing good imaging ability (spatial resolution of 6 mm fwhm) with high sensitivity (1000–2000 counts/μCi · min) with positron emitting test phantoms ( 22Na and 68Ga).

The Design of a Bandpass Filter with Inductive Strip -- Planar Circuit Mounted in Waveguide

The equivalent circuit of an inductive strip inserted in the middle of a waveguide parallel to the E plane is analyzed theoretically by evaluating the inductive reactance of the equivalent T network which was obtained by the Rayleigh-Ritz variational technique. A design theory for the bandpass filter of this type is derived from this equivalent circuit. The confirmation between the design theory and the experimental resuIts is also shown.

An investigation of the diffraction fields of plane inhomogeneities in a waveguide by means of metal-semiconductor film structures

1. A solution has been derived for the problem of the diffraction of H01-waves in a rectangular waveguide by a central inductive strip and a metal-semiconductor film structure. 2. It has been shown that the distortion introduced into the diffraction field of the inductive strip by a matched multilayer structure is negligible. 3. Because of the spreading of the thermal film, the temperature profile deviates from the distribution law of the induced currents in the absorptive film; with increasing values of the parameter k and the modulation frequency F, this deviation decreases. 4. It has been shown both theoretically and experimentally that it is possible to use the DML method with metal-semiconductor film structures for the investigation of diffraction fields in a waveguide.

Solution of Waveguide Discontinuities by Modal Analysis

A general method is presented for analysis of waveguide junctions and diaphragms by summing normal modes of propagation, giving solutions for the resulting scattered modes. Because interaction effects of dominant and higher-order modes between discontuities are allowed, finite-length obstructions can be studied. Solutions are found without any prior assumption about the total fields existing at the discontinuities and, as a result, the formulation is applicable to a wide range of problems. The technique proves to be simple and is ideally suited to computers, involving mainly the solution of sets of simultaneous linear equations. Thick and thin symmetrical bifurications of a rectangular guide are studied. Forward-scattered mode amplitudes and imput admittances are calculated, the computed admittance of the thin bifurication is compared with well-known results, and transverse field patterns on both sides of the junction are plotted, thus showing the accuracy of the match. The results of a finite-length bifurication by a thick vane are presented for a range of lengths, the parameters of the equivalent T network being given in each case. For very short lengths, the problem corresponds to an inductive strip across the guide.

Reactance of a symmetrical pair of strips in rectangular waveguide

An integral equation is found for the currents on a pair of symmetrical inductive strips in a rectangular waveguide, and is solved by known techniques to the quasistatic approximation. The integrals involved in the formula for the reactance presented to the waveguide are expressed in terms of elliptic integrals, and by a comparison of the result with the known result for a single inductive strip, the mutual inductance between a pair of strips in a waveguide is deduced.

The impedance of unsymmetrical strips in rectangular waveguides

The radiation from capacitive and inductive strips is calculated in terms of arbitrary currents flowing on the strip surfaces. By requiring the tangential component of the sum of an incident field and the radiated field to vanish at the surface of the strip, an integral equation for the currents is obtained. This integral equation is solved by a transformation of variables due to Schwinger. The integrals involved in the final solution are given in terms of standard elliptic integrals.The following generalizations of the well-known quasi-static formulae for symmetrically located strips are obtained:(a) Capacitive strip of width D, centre x0 from waveguide side; waveguide dimensions a × b (see Fig. 1).Susceptance B=4b/λg log Θ(β)/(1+s)Θ(0)where cn β = c/(1+s)c = cos(πx0/b) sin(½πD/b).s = sin(πx0/b) cos(½πD/b).The modulus of the elliptic functions is [4s/(1+s)2−c2]½(b) inductive strip of width D, centre Y0 from waveguide side; waveguide dimensions a × b (see Fig. 2).Reactance X= a/λg[−1+K cosec2 (πy0/a)/2E − K sin2 (½π D/a)]The modulus of the elliptic functions is[1 − sin2 (½π D/a) cosec2 (πy0/a)]½