This paper discusses the behavior of oscillators with multiple-resonant circuits. It discusses the condition for free-running stable oscillations, the injection locking phenomena, the stable locking range, the noise of free-running and injection-locked oscillators, and a condition for parasitic oscillations in detail, and presents a graphical interpretation of this study for clarity. Finally, this paper shows how broadbanding of oscillators can be achieved with a double-resonant circuit. This provides a systematic guide for the design of broadband frequency deviators and broadband injection-locked oscillators for numerous applications.

Some basic characteristics of broadband negative resistance oscillator circuits

The theory of cavity stabilization of a microwave oscillator is reviewed and the appropriate design equations presented. The theory is verified with data taken on three different types of microwave oscillators: 1) a 10-GHz reflex klystron (stabilization factor achieved-22; FM noise reduction-28 dB; typical FM noise level-0.008 Hz in a 1-Hz bandwidth); 2) a 9.7-GHz low-noise two-cavity klystron oscillator (stabilization factor achieved-10; FM noise reduction--21.7 dB; typical FM noise level-0.0007 Hz in a 1-Hz bandwidth); 3) a 10-GHZ avalanche transit time diode oscillator (stabilization factor estimated at 30; FM noise reduction-29.5 dB; typical FM noise level--0.5 Hz in a 1-Hz bandwidth). Stabilization of the avalanche transit time diode oscillator produced a significant reduction in AM noise for modulation frequencies larger than the bandwidth of the stabilizing cavity.

Microwave Oscillator Noise Reduction by a Transmission Stabilizing Cavity

Transmission-type injection-locked oscillators equipped with both signal-input and power-output ports are studied. A comparison with traditional reflection-type injection-locked oscillators, in which a signal is injected into the output port of the oscillator, is presented theoretically. It is shown that the Iocking range of transmission types always differs from the reflection type by a factor of G/sub s// G/sub p/ where G/sub s/ represents the maximum stable gain of the two-port oscillator and G/sub p/ represents the square root of the output power ratio of the two ports. Experiments on common-source injection-locked oscillators using GaAs FET chips are described and show that, with transmission types, a 1.8 times wider Iocking range can be obtained than with reflection types. Furthermore, investigation of FM noise for both types of injection revealed lower off-carrier FM noise for transmission types than reflection types, even though the Iocking gain of the transmission types was kept the same as that of reflection types. Thus overall features of transmission-type injection locking were found to be advantageous for FM signal amplification even though there is a minimal power loss at the signal input port.

Transmission-Type Injection Locking of GaAs Schottky-Barrier FET Oscillators

https://ieeexplore.ieee.org/iel6/22/25064/01129637.pdf

Injection Locking of GaAs Schottky-Barrier FET Oscillators

A 9.72 GHz avalanche transit time oscillator (ATTO) with FM noise of 100 Hz rms/100 Hz was synchronized by a 9.72 GHz stabilized klystron with FM noise of 0.01 Hz rms/100 Hz. The FM noise of the synchronized oscillator was reduced, but not as much as expected for modulation frequencies below 10 kHz. The AM noise was not changed by synchronization.

Measured FM noise reduction by injection phase locking

This paper presents experimental data taken to determine the frequency modulation characteristics of avalanche transit time oscillators. The active element is a diffused mesa diode with a shallow junction in epitaxiad n-n+ silicon; the details of the construction of the diode are presented and its typical characteristics are discussed. The basic oscillator consists of the diode mounted in the capacitive portion of a radial mode cavity machined of copper with the outlines of a DO-5 diode header. The frequency of oscillation is dependent upon the diode junction capacitance and is varied between 5 and 8 GHz for the diodes tested. Microwave power levels up to 100 mW have been observed with an efficiency exceeding 3 percent. The frequency drift over the temperature range from -70 to +100/spl deg/C is 2.5x10/sup -5/ parts/ /spl deg/C. The frequency modulation characteristics of these oscillators indicate their potential applications in miniature solid-state low-power communications systems.

K.E. Gsteiger

Papers

Frequency Modulation of Avalanche Transit Time Oscillators