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Varactor Tuned Gunn oscillators and chip-level IMPATT diode power combiners have been fabricated at frequen cies as high as 12 GHz using lumped element circuits. Techniques for the design and fabrication of such circuits have been developed and their advantages investigated. The best lumped-element VCO tuned from 6 to 11.3 GHz with no evidence of spurious outputs. A six-mesa series-parallel array of GaAs IMPATT diode chips generated 22.5 watts CW with 20.5% efficiency at 8.65 GHz.

Results with series and series-parallel connections of CW 40-GHz IMPATT diodes on diamond are discussed. The effects of device and circuit losses on the efficiency are treated. Device loss associated with the stabilizing capacitors appears likely as the major factor limiting the combining efficiency. Maximum combining efficiency of 82 percent has been demonstrated for two diodes connected in series. The multichip geometries utilize Raytheon gallium arsenide CW double-drift diode chips and are essentially scaled versions of successful X-band geometries previously reported by the authors.

The effects of package parasitic on series interconnections of TRAPATT diode chips on diamond substrates have been studied via time domain computer simulations and experiments at frequencies from 2 to 9 GHz. Guidelines for the selection of package parasitic have been identified, and multichip series configurations, employing six chips mounted thermally in parallel on diamond, have been successfully demonstrated at 7.5 GHz with 35.5 watts output power.

X-band IMPATT diode chips have been efficiently combined in parallel, in series on diamond, stacked with diamond heat sinks and using lumped element circuit techniques with mode suppression. Combined device types include c.w. silicon p+-n-n+, c.w. GaAs Schottky lo-hi-lo, pulsed GaAs p+-hi-lo and pulsed GaAs double-drift. This paper will summarize tasks performed over a four year period and will attempt to place some of the results in perspective with respect to practical applications. Work at 35 GHz, begun in December 1978, will also be described.

The objective of the work described here was to develop a system-oriented closed-cycle cooled parametric amplifier using a commercially available cooler. The desired characteristics were: tuning range, 7.0 to 8.0 Gc; instantaneous bandwidth, 20 to 30 megacycles; effective noise temperature, about 70/spl deg/ Kelvin including the uncooled X-Band four port circulator. The compatibility for use, at a later date, of more complex multistage coolers to allow cooling of the circulator and parametric amplifier combination, was also an important consideration.

A joint services project to develop a microwave materials database is described. The major goal is to improve the availability of accurate data on the "high tech materials" needed for cost-effective production of microwave packages.

X band IMPATT diode chips have been efficiently combined in parallel, in series on diamond heat sinks, and in series-parallel on diamond heat sinks. This paper summarizes experimental and analytical work performed over a four-year period and places some of the results in perspective with respect to practical applications. Several device types have shown to be compatible with series geometries. Analysis has shown that some device types, when connected in series, form a combination which is neither open-circuit nor short-circuit stable, an intrinsically unstable condition. It has been shown further that capacitors of practical size can be placed in parallel with each chip of such an assembly to prevent the occurrence of the unstable condition. Thus unique problems reported earlier with some types of IMPATT's are understood and can be prevented. These experimental and analytical results appear to eliminate any hypothetical barrier to the routine series power combining of at least several types of IMPATT device chips.

The design and performance of broad-band TRAPATT amplifiers in X band are described along with a discussion of critical circuit parameters. Bandwidths of 10 percent and peak powers up to 38 W have been achieved using coaxial circuits with single and multichip diodes.

The results of experiments using TRAPATT diodes connected in series at 0.5, 2, and 8 GHz are described. These experiments demonstrate that successful series operation of TRAPATT's at frequencies up to at least 2 GHz can be achieved in a configuration suitable for long pulsewidth or CW operation. An 8-GHz operation of series stacked TRAPATT'S yielded high power outputs at the same efficiency achieved with single devices but no well heat sunk configuration was found that yielded good efficiency.

This correspondence presents a simple circuit which allows direct combining of the power obtainable from several avalanche diodes. The circuit does not require extremely close matching of dc or RF diode characteristics, and no particular isolating networks such as hybrid combiners are necessary. CW power output exceeding 4 watts at 7 GHz and 3 watts at 9 GHz has been demonstrated in a device employing five diodes. The number of diodes which can be combined using this technique is limited by geometric and heat sink considerations. Descriptions of typical single-diode and multiple-diode oscillators are given along with equivalent circuits. The circuits employ resistors or resistor networks to suppress low-frequency oscillations and undesired resonances which occur when several oscillators are coupled together. Negligible insertion loss is incurred at the design output frequency. Measured performance is given on similar single- and multiple-diode oscillators. Data include frequency, power, AM noise, FM noise, temperature, and loaded Q.

The design and performance of broad-band TRAPATT amplifiers in X-band are described along with a discussion of critical circuit parameters. Bandwidths of 10% and peak powers up to 38 watts have been achieved using coaxial circuits with single and multichip diodes.

The parametric amplifier described has met several conditions which, to the writers knowledge, have not been realized heretofore in an integrated amplifier assembly suitable for system application.

Experiments with four-mesa silicon p+-n-n+ IMPATT diodes have shown power saturation and reduced efficiency when connected and packaged in electrically asymmetrical configurations. The need for electrical symmetry is illustrated by experiments wherein seemingly trivial asymmetries caused severe saturation of the power output.

Gallium-arsenide Schottky low-high-low IMPATT-diode chips have been successfully combined in series. A maximum c.w. power output of 22.5 W has been repeatedly obtained in X-band by using six 4-W 0.2-mm-diameter mesa GaAs devices. After careful preselection of GaAs chips (yield ≃ 20%), the GaAs devices combined more readily than did silicon p+-n-n+ impatt chips.

TRAPATT diodes for X band c.w. operation have been made using both double-epitaxy and diffusion techniques. These p+nn+ devices are fabricated in ring configurations and mounted on type-IIA diamond heat spreaders. A c.w. TRAPATT performance of 3.3 W and 18.5% efficiency has been achieved at 8 GHz using these diodes.