Output spectrum of IMPATT-diode oscillators

The width of the output spectrum of an IMPATT-diode oscillator, operating at low- and intermediate-output levels, is calculated. It depends on the power-density spectrum of the primary noise current, introduced by Hines, at the oscillation frequency. Low-frequency components of this noise current give rise to an additional modulation of the centre frequency of the output spectrum.     

High-power high-efficiency operation of read-type IMPATT-diode oscillators

C.W. operation of GaAs Schottky-barrier Read-type IMPATT-diode oscillators is reported. These devices exhibited efficiences from 20 to 24% with output powers of 2 ~ 3 W c.w. in the Ku-band. The best efficiency was 24%, with an output power of 1.8 W c.w., while the maximum output power was 3.2 W c.w., with an efficiency of 20.7% at frequencies near 14 GHz.     

F.m. noise of low-level-operating IMPATT-diode oscillators

An analytical relationship for the output-spectrum width of a low-level-operating IMPATT-diode oscillator is verified experimentally by measuring relevant diode and circuit quantities as well as the oscillator noise. Good agreement between theory and experiment is found if the spectrum width is assumed to be predominantly due to f.m. noise.     

A.M. noise of IMPATT-diode oscillators

Based on a general oscillator model, noise spectra are calculated by a quasistationary method. From this, the reduction of the a.m. noise caused by adjusting the locus of the load circuit orthogonal to the curve of the device impedance is indicated and verified by experiments. The noise reduction generally is 5?15 dB. Measurements of the a.m.-f.m.-noise-correlation coefficient confirm the results.     

Investigation of parasitic oscillations in IMPATT-diode oscillators by a simple locus chart

Using a simplified theory of parasitic oscillations in IMPATT-diode oscillators, a locus chart is constructed that facilitates the study of parasitic oscillations of the degenerate type. Results of experiments on a high-Q factor coaxial/waveguide circuit (Kurokawa circuit) are explained by this locus chart.     

Noise in Gunn oscillators

We estimate the ultimate noise of Gunn oscillators in the absence of 1/fnoise. The basic noise source considered is thermal or Johnson noise augmented by intervalley noise of carriers hopping between the high and low mobility bands. For example, for Qext= 10²and Pout=10^-1W we estimate δfrms≈ 1-2 Hz, and AM noise relative to the carrier of -156 dD, both measured in 1-kHz bandwidths.     

Noise considerations when determining phase of large-signal microwave measurements

Advances in microwave instrumentation now make it feasible to accurately measure not only the magnitude spectrum, but also the phase spectrum of wide-bandwidth signals. In a practical measurement, the spectrum is measured over a finite window of time. The phase spectrum is related to the position of this window, causing the spectrum to differ between measurements of an identical waveform. It is difficult to compare multiple measurements with different window positions or to incorporate them into a model. Several methods have been proposed for determining the phase spectrum such that multiple measurements can be effectively compared and utilized in models. The methods are reviewed in terms of the information required to determine the phase and compared in terms of their robustness in the presence of measurement noise.     

Noise measurements of microwave local oscillators

A method for measuring the spectral distribution of amplitude fluctuations and frequency fluctuations in microwave oscillators is described. The method provides for evaluation of (1) amplitude fluctuations in terms of signal to noise ratio; (2) frequency fluctuations in terms of two parameters: (a) rms deviation; (b) rms rate of change of deviation. In addition, the method permits estimation of the correlation between these two noise components. Some typical results of measurements are described, and certain implications of the effects of system parameters on interpretation of these results are considered. For a specific system, two measurements are shown to be sufficient to determine the effect of frequency noise on system performance.     

Noise in bipolar junction transistors at high injection levels

It is shown herein that the expression for the noise equivalent saturated diode current I_EQ at the output of the common-base configuration, input a.c. open circuited, at medium and high-injection levels is identical in form to that used at low-injection levels, but for different reasons. Until the present, this fact has not been theoretically demonstrated. Experimental results verify this theoretical prediction.     

Low-frequency stability margin in IMPATT-diode circuits

A new diagram is proposed, useful in evaluating at first sight the low-frequency stability performance of IMPATT-diode circuits. A definition for the low-frequency stability margin is given. The use of the diagram in computing the stability margin is shown. The usefulness of the diagram and of the definition is pointed out.     

BARITT-diode large-signal performance

p+-n-p+ BARITT diodes have produced maximum output powers of the order of 100 mW. A large-signal computer simulation is used to evaluate the device conductance as a function of the r.f. voltage amplitude, and hence the output power. It is concluded that, to. obtain optimum output power, (a) the n-region doping density should be increased and (b) the chip series resistance should be minimised.     

Transferred-electron oscillators at very high frequencies

The high-frequency characteristics of transferred-electron oscillators have been examined by computer simulation. Maximum frequencies in the range 100 to 200 GHz (for GaAs) and contact effects favouring current saturating cathodes are predicted.     

Noise performance of frequency- and phase-locked CW magnetrons operated as current-controlled oscillators

Low-power continuous wave "cooker" magnetrons driven from industrial-quality switch-mode power supplies have been frequency locked by driving them as current-controlled oscillators in a phase-lock loop (PLL). The noise performance of these frequency-locked oscillators is reported as a function of heater power. The injection of -30- to -40dB signals derived from the reference oscillator of the PLL into the magnetron's output waveguide while the anode current is controlled by the PLL is shown to phase lock the magnetron's output. Results for locking performance are presented.     

Balanced monolithic oscillators at K- and Ka-band

A technique for generating accurate antiphase signals is presented in this paper. Monolithic oscillators at 20 and 40 GHz are realized using this technique. These oscillators have dual outputs that are mutually locked in antiphase. The inherent amplitude and phase balances between the output signals are verified. This is achieved by direct measurement using injection-locking polar diagrams, as well as low-frequency measurements of the down-converted oscillator outputs. The operation of the balanced oscillator as a multidevice power-combining oscillator is also investigated. Improvements of phase noise reduction and frequency stabilization are demonstrated at the combined oscillator output. This new oscillator topology shows significant potential in balanced circuits like mixers, multipliers, and modulators where circuit performance relies on the precise generation of the balanced signals     

Inductive loading of the bias path in IMPATT-diode circuits

It is shown that the addition of a large series inductance in the bias path of an IMPATT-diode circuit improves its low-frequency stability margin.     

Resistive parametric mixing in GaAs oscillators at microwave frequencies

Resistive mixing in GaAs between a suitably biased microwave pump signal and a small signal at the first subharmonic of the pump is shown to result in an effective negative mobility at the signal frequency. The implications are discussed.     

Improved large-signal quasistatic MESFET model

Improvements to the quasistatic modelling procedure which has been established by Rauscher and Willing (1978, 1979) are discussed. Specifically, a more accurate method of modelling the channel conductance and a technique for establishing the correct DC bias conditions within the MESFET model are provided.<>     

Floating switch with large-signal capability

Electronic switches using field-effect devices are widely used, but suffer from a low ratio of signal-waveform amplitude to control-waveform amplitude. A switch configuration is described using two devices and overcoming this disadvantage.     

Performance of monolithic GaAs FET oscillators at J-band

Monolithic GaAs FET oscillators were demonstrated at J-band frequencies. Output power up to 160 mW with 23-percent efficiency at 12 GHz was achieved. With a discrete tuning varactor, a 300-µm gate-width FET monolithic oscillator was tuned from 16 to 20 GHz. The average output power was l0 mW.