This theoretical and experimental study was motivated by a specific need for a solid‐state microwave generator with an output efficiency exceeding 20% and focused on the properties of GaAs avalanche transit‐time devices. First, the dependence of the ionization rates and drift carrier velocities as a function of electric field and temperature is established. Then several methods of calculation, exact enough to take into account all the important efficiency‐limiting effects in the device, are discussed and used to derive theoretical figures for the efficiency of a GaAs IMPATT oscillator, special attention being given to the influence of the doping profile. Finally, the experimental study is described, including device realization and experimentally measured efficiencies, and a comparison between these and the calculated values is done. It is shown that the best calculated performances can reach 30% efficiency and that it is possible to obtain experimentally cw oscillation efficiencies exceeding 20% with GaA...

Theoretical and experimental study of GaAs IMPATT oscillator efficiency

The behavior of IMPATT oscillators with enhanced leakage current has been experimentally evaluated by irradiating operating diodes with transient ionizing radiation. Leakage current was induced in diffused junction GaAs and silicon X-band IMPATT diodes by irradiation with 100 nsec pulses of 10 MeV electrons. With increasing leakage current, the oscillator RF power decreases and the frequency of oscillation increases. A large signal circuit model of the IMPATT diode is developed which correlates well with experimental measurements.

IMPATT oscillators with enhanced leakage current

The performance of a variety of IMPATT diode oscillators has been measured under transient ionizing radiation conditions, and the results of a large signal model which agrees with experiment are presented. Five hundred milliwatt cw diode oscillators (silicon and gallium arsenide with various types of avalanching junctions) were exposed to 100 nanosecond pulses of 10 MeV electrons at dose rates between 2 × 108 and 8 × 109 rads/sec. With these oscillators, the RF power is reduced at increasing dose rates and is quenched entirely during the radiation pulse at a dose rate dependent upon the DC bias current (greater than 5 × 109 rads/sec for 500 mW oscillators in vacuum). With diodes open to air, oscillators in low Q cavities were quenched during the radiation pulse with a total dose of 500 rads. The results of a large signal theory including the effects of leakage current are presented that agree well with the RF power decrease during irradiation.

Transient Ionizing Radiation Effects on Baritt Diode Oscillators

Effective stabilization of an IMPATT oscillator in the millimeter-wave region carI be achieved through subharmonic injection locking to a weak parasitic oscfffatfng signaI. In subharmonic injection- Iockfng experiments more than 19 dB of locking gain at 1O-MH2 locking range was obtained at a subharmonic ratio 1:2 of the main osculating frequency. At the subfrarmonics 1:4 and 1:6, the locking gain was more than 12 and 13 dB at 10 MHs, respecti~ely. Using the parasitic oaciUating signaf, higher than 32-dB gain and Ml- MHz locking range at a subhmmordc ratio 1:2 of the parasitic oscillating frequency was oMained. This locking gain was 13 rfB higher than that for tbe mafrr oscillating signal. At the subbarnrordc ratio 1:4, the gain was more than 15 dff higher. As mraaured with the spectrum arrafyzer, the oacilIathsg sigoaf which was locked by the subharmonic injection signaf afmost coincided with the injection sigrraf. These data show that the subharmonic injection locking baa high gain as compared with that using the mairI oscillating signaf.

http://ieeexplore.ieee.org/iel6/22/25064/01129655.pdf

High Effective Subharmonic Injection Locking of a Millimeter-Wave

-Effective stabilization of an IMPATT oscillator in the millimeter-wave region can be achieved through subharmonic injection locking to a weak parasitic oscillating signaI. In subharmonic injection-Iocking experiments more than 19 dB of locking gain at 10-MHz locking range was obtained at a subharmonic ratio 1:2 of the main oscillating frequency. At the subharmonics 1:4 and 1:6, the locking gain was more than 12 and 13 dB at 10 MHz, respectively. Using the parasitic oscillating signal, higher than 32-dB gain and 10-MHz locking range at a subharmonic ratio 1:2 of the parasitic oscillating frequency was obtained. This locking gain was 13 dB higher than that for the main oscillating signal. At the subharmonic ratio 1:4, the gain was more than 15 dB higher. As measured with the spectrum analyzer, the oscillating signal which was locked by the subharmonic injection signal almost coincided with the injection signal. These data show that the subharmonic injection locking has high gain as compared with that using the main oscillating signal.

High Effective Subharmonic Injection Locking of a Millimeter-Wave IMPATT Oscillator

Equivalent circuits are introduced for nonlinear operation of the avalanche transit-time diode at a single frequency and at two harmonically related frequencies. Parameters are derived that characterize the nonlinear interaction between the diode and the associated microwave circuit. Particular attention is devoted to the oscillator, the frequency multiplier, and the frequency divider. For the oscillator, parametric interaction with a harmonic of the desired oscillation frequency is shown to give possibilities of enhancing the output power and of significantly improving the noise performance. An experimental two-frequency oscillator is described that has confirmed the theoretical predictions.

K. Mouthaan

Papers

Characterization of Nonlinear Interactions in Avalanche Transit-Time Oscillators, Frequency Multipliers, and Frequency Dividers