The finite-difference-time-domain (FDTD) method is extended to include distributed electromagnetic systems with lumped elements (a hybrid system) and voltage and current sources. FDTD equations that include nonlinear elements like diodes and transistors are derived. Calculation of driving-point impedance is described. Comparison of FDTD calculated results with analytical results for several two-dimensional transmission-line configurations illustrates the accuracy of the method. FDTD results for a transistor model and a diode are compared with SPICE calculations. The extended FDTD method should prove useful in the design and analysis of complicated distributed systems with various active, passive, linear, and nonlinear lumped electrical components. >

Extending the two-dimensional FDTD method to hybrid electromagnetic systems with active and passive lumped elements

The basic theory of quasi-optical Gaussian beam propagation and beam transformation by simple optical elements is summarized, and coupling to and between Gaussian beams is briefly discussed Guidelines for Gaussian optics system design are reviewed, the most important being beam truncation and matching Passive components in the terahertz frequency range based on quasi-optical propagation, including polarization processors, filters, diplexers, and ferrite devices, are examined Some active quasi-optical devices, including multielement oscillators, frequency multipliers, and phase shifters, are described Some specific applications of quasi-optical systems are briefly described >

Quasi-optical techniques

This paper gives an overview of measurement techniques used in the THz region of the electromagnetic spectrum, from about 100 GHz to several THz Currently available components necessary for THz metrology, such as sources, detectors and passives, are briefly described A discussion of power measurements, vector network analysis and antenna measurements as well as the limitations of these measurements at THz frequencies is given The paper concludes with a summary of available components and instrumentation for THz metrology at the time of writing

THz Metrology and Instrumentation

Two devices, the multi-quantum-barrier varactor (MQBV) and the Schottky-quantum-barrier varactor (SQBV), have been developed and applied in quasi-optical arrays for millimeter-wave harmonic generation. Monolithic arrays utilizing these devices have been successfully fabricated with nearly 100% yield. An output power of 5 W (1.25 W) at 99 GHz has been achieved with an SQBV (MQBV) tripler array, in excellent agreement with large-signal simulation predictions after correcting for diffraction losses in the matching system. These results represent the state of the art in solid-state millimeter-wave sources. >

Monolithic quasi-optical frequency tripler array with 5-W output power at 99 GHz

This paper describes the design, fabrication, and experimental evaluation of W-band planar monolithic varactor frequency multipliers based on finite ground coplanar (FGC) lines. These lines are a low-loss low-dispersion alternative of a planar transmission line to more conventional microstrip of coplanar waveguide lines at millimeter-wave frequencies. The near transverse-electromagnetic nature of propagation of the FGC lines simplifies circuit design and layout. Two-diode W-band varactor multipliers with input Q's of two and three and FGC input and output have been realized. The multiplier with input Q=2 has an output power of 72 mW, an efficiency of 16.3% near 80 GHz, and a -3-dB bandwidth greater than 10 GHz, while the multiplier with Q=3 has an efficiency of 21.5% near 70 GHz and a 6-GHz bandwidth. This paper briefly describes the characteristics of the FGC lines, the design of the multipliers and their radiofrequency performance.

W-band finite ground coplanar monolithic multipliers

The authors have proposed that the increasing demand for contact watt-level coherent sources in the millimeter- and submillimeter-wave region can be satisfied by fabricating two-dimensional grids loaded with oscillators and multipliers for quasi-optical coherent spatial combining of the outputs of large numbers of low-power devices. This was first demonstrated through the successful fabrication of monolithic arrays with 2000 Schottky diodes. Watt-level power outputs were obtained in doubling to 66 GHz. In addition, a simple transmission-line model was verified with a quasi-optical reflectometer that measured the array impedance. This multiplier array work is being extended to novel tripler configurations using blocking barrier devices. The technique has also been extended to oscillator configurations where the grid structure is loaded with negative-resistance devices. This was first demonstrated using Gunn devices. More recently, a 25-element MESFET grid oscillating at 10 GHz exhibited power combining and self-locking. Currently, this approach is being extended to a 100-element monolithic array of Gunn diodes. This same approach should be applicable to planar vacuum electron devices such as the submillimeter-wave BWO (backward wave oscillator) and vacuum FET. >

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Array concepts for solid-state and vacuum microelectronics millimeter-wave generation

Monolithic Schottky diode grids have been fabricated on 2-cm/sup 2/ GaAs wafers in a proof-of-principle test of a quasioptical varactor millimeter-wave frequency multiplier array concept. An efficiency of 9.5% and output power of 0.5 W were achieved at 66 GHz when the diode grid was pumped with a pulsed source at 33 GHz. The diode-grid equivalent circuit model based on a transmission-line analysis of plane-wave illumination was verified experimentally over a frequency range of 33 GHz to 140 GHz. In parallel with the diode doubler array studies, the authors investigated the use of an MOS structure having an undoped epitaxial layer, which is grown on a heavily-doped substrate and isolated by a thin oxide layer and a GaAs barrier-intrinsic-N/sup +/ (BIN) diode structure. The thin MOS concept was tested for doubling efficiency (to 95 GHz) for a variety of dot radii as a function of pump power. In support of the monolithic BIN diode array studies, a quasioptical tripler design was developed and tested. Based on the results reported, the authors are confident in predicting watt-level continuous-wave power from a monolithic-diode-grid frequency tripler design using the BIN diode concept. >

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Watt-level millimeter-wave monolithic diode-grid frequency multipliers

Watt‐level cw solid‐state sources in the millimeter‐wave region are needed for plasma diagnostics. Monolithic metal‐grid arrays containing in excess of 1000 Schottky diodes have produced watt‐level output at 66 GHz in a doubler configuration, in excellent agreement with the large‐signal predictions of the frequency multiplication. Current efforts are concentrated on fabricating and developing arrays of a novel barrier‐intrinsic‐N+ (BIN) diode which promise increased performance in a tripler configuration. Initial tests will be made for a configuration where a tripling efficiency of 35% at an output frequency of 100 GHz is predicted. Eventual goals are monolithic BIN diode grids operating at 1 THz.

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A monolithic planar array containing thousands of GaAs barrier-intrinsic-n/sup +/ diodes have produced 1-W output power at 100 GHz in a tripler configuration. Tripling efficiency of 8.5% has been obtained from approximately 4-mW incident power on each diode, in excellent agreement with the predictions of large-signal nonlinear circuit analysis of frequency multiplication. The device performance is limited by the parameters of the fabricated diodes. Significant improvement is expected with realizable diode parameters and optimized pumping condition. >

/pdf/quasi-optical-watt-level-millimeter-wave-monolithic-solid-4pza1tjmbu.pdf

Quasi-optical watt-level millimeter-wave monolithic solid-state diode-grid frequency multipliers

The authors report the fabrication and millimeter-wave performance of a novel class of monolithic metal-semiconductor heterostructure devices, the barrier-intrinsic-n/sup +/ (BIN) diode-grid frequency multipliers, which are fabricated on III-V compound semiconductors. They also report the measurement of the DC and low-frequency electrical properties of the multiplier. A novel analytical model that accurately describes the structure is presented. Based on the theoretical and experimental studies presented here, the authors predict watt-level CW (continuous wave) output power at 90-180 GHz from a monolithic diode-grid multiplier design using the GaAs BIN concept. >

DC and millimeter-wave performance of watt-level barrier-intrinsic-n/sup +/ diode-grid frequency multiplier fabricated on III-V compound semiconductors

R.J. Hwu

Papers

Array concepts for solid-state and vacuum microelectronics millimeter-wave generation

Watt-level millimeter-wave monolithic diode-grid frequency multipliers

Watt-level millimeter-wave monolithic diode-grid frequency multipliers

Quasi-optical watt-level millimeter-wave monolithic solid-state diode-grid frequency multipliers

DC and millimeter-wave performance of watt-level barrier-intrinsic-n/sup +/ diode-grid frequency multiplier fabricated on III-V compound semiconductors