Robert E. Neidert

Theory and numerical calculations for radially inhomogeneous circular ferrite circulators

This paper presents a new theory for the operation of microstrip and stripline circulators, specially set up to permit radial variation of all the magnetic parameters. A computer code, taking only a few seconds per calculated point on a modest computer, was developed from the theory, and calculated results are given. In the theory we develop a two-dimensional (2-D) recursive Greens function G suitable for determining the electric field E/sub x/ anywhere within a microstrip or stripline circulator. The recursive nature of G is a reflection of the inhomogeneous region being broken up into one inner disk containing a singularity and N annuli. G has the correct properties to allow matching to the external ports, thereby enabling s-parameters to be found for a three-port ferrite circulator. Because of the general nature of the problem construction, the ports may be located at arbitrary azimuthal angle /spl phi/ and possess arbitrary line widths. Inhomogeneities may occur in the applied magnetic field H/sub app/, magnetization 4/spl pi/M/sub s/, and demagnetization factor N/sub d/. All magnetic inhomogeneity effects can be put into the frequency dependent tensor elements of the anisotropic permeability tensor. Numerical results are presented for the simpler but immensely practical case of symmetrically disposed ports of equal widths taking into account these radial inhomogeneities. Studies of breaking up the area into 1, 2, and 5 annuli are undertaken to treat specific inhomogeneous problems. The computer code which evaluates the recursive Greens function is very efficient and has no convergence problems.

Losses in Y-junction stripline and microstrip ferrite circulators

A complete theory for calculating the dielectric, conductor, and magnetic losses of Y-junction stripline and microstrip ferrite circulators in terms of three-port S-parameters is described. Calculations using this theory are presented and compared with existing data for varied circulator parameters over a frequency range of 1-100 GHz. >

Millimeter-wave planar InP Schottky diodes and their small-signal equivalent circuit

Two planar indium phosphide Schottky diode designs have been fabricated and analyzed for millimeter-wave detector applications up to 150 GHz. Device structure and fabrication are discussed, and small-signal equivalent circuit models are presented. The following topics are included: the planar InP diode structure fabricated by megaelectron volt ion implantation. DC and RF measurements, circuit model values, and 94-GHz small-signal detector performance. The zero-bias detector sensitivity at 94 GHz was measured to be as high as 400 mV/mW, and the calculated tangential signal sensitivity was -56 dBm. >

Solid state monolithic variable phase shifter with operation into the millimeter wave wavelength regime

Information is provided on the theory and design, fabrication, and experimental results for a phase shifter designed to operate in the millimeter wavelength region. The device was fabricated in a manner that makes it compatible with present GaAs monolithic microwave circuit technology. Continuously variable phase shift is obtained by varying the bias voltage from −5.0 to +0.65 V on a Schottky microstrip line. Experimental phase shift and loss data are provided for two different width (w) Schottky lines, w=1.5 and 7.3 μm, for frequencies 2–18 GHz.

Wide-Band Gallium Arsenide Power MESFET Amplifiers

The performance, with emphasis on wide bandwidth, that can be expected of linear medium power GaAs microwave MESFET (metal semiconductor field-effect-transistor) amplifiers is discussed. It starts with measured scattering parameters of devices and proceeds through computer-optimized device modeling, to amplifier circuit designs and performance results. It shows computed and measured octave bandwidth performance and reveals that decade bandwidth is feasible. It discusses single-ended and balanced amplifier design approaches. Some practical designs with performance results are presented, with circuit topologies which are easily realizable in microstrip.

Inhomogeneous ferrite microstrip circulator: theory and numerical calculations using a recursive Green's function

A two dimensional recursive Greens function G is developed which is suitable for determining the electromagnetic fields anywhere within a microstrip (or stripline) ferrite circulator. The recursive nature of G is a reflection of the inhomogeneous region being broken up into one inner disk containing a singularity and N annuli. G has the correct properties to allow matching to the external ports, and to allow computing the 3-port s-parameters of a circulator. Because of the general nature of the problem construction, the ports may be located at arbitrary azimuthal angle ¿ and possess arbitrary line widths. Non-uniformities can occur in the applied magnetic field Happ, magnetization 4¿Ms, and demagnetizing factor Nd. All inhomogeneity effects can be put into the frequency dependent tensor elements of the anisotropic permeability tensor. Numerical results are presented for the simpler but immensely practical case of symmetrically disposed ports of equal widths taking into account these radial inhomogeneities. Studies of breaking up the area into various numbers of annuli are undertaken to display the approximation levels required to treat inhomogeneous problems. Convergence properties of the recursive Greens function are presented, and computation speed is shown.

Millimeter-wave InP lateral transferred-electron oscillators

A lateral InP transferred-electron device (TED) designed with a high-resistivity notch adjacent to the cathode contact is presented, and its application to millimeter-wave monolithic integrated circuits is demonstrated. At 29.9 GHz, a CW power output of 29.1 mW with a conversion efficiency of 6.7% has been obtained from cavity-tuned discrete devices. This result represents the highest power output and efficiency of a lateral TED in this frequency range. The lateral devices also had a CW power output of 0.4 mW at 98.5 GHz and 0.9 mW at 75.2 GHz. A 79.9-GHz monolithic oscillator incorporating the lateral TED is reported. Experimental and theoretical results which further the understanding of the lateral device operation are presented. >

Examination of millimetre-wave frequency-gain behaviour of GaAs MESFETs

ABSTRACT Analytical expressions are derived for stability factor, maximum stable gain, and maximum available gain for a submicron-gate-length GaAs MESFET. Explicit gain dependence on source inductance, gate transit time and gate-drain feedback capacitance, for example, enables assessment of millimetre-wave device performance possibilities and limitations.