GB1212872A - Frequency multiplier transistor oscillator - Google Patents

Abstract

1,212,872. Transistor oscillator-multiplier. NIPPON ELECTRIC CO. Ltd. 14 Dec., 1967 [15 Dec., 1966], No. 56880/67. Heading H3T. In a frequency multiplier transistor oscillator having a transistor 1 and its associated tuning circuit of relatively low Q generating a fundamental frequency, the fundamental frequency is multiplied by the non-linear junction capacitance between the base and collector of the transistor which serves as a variable capacitance diode, and the Nth harmonic of the fundamental frequency is derived from a Nth harmonic resonator 7 of relatively high Q such that the fundamental frequency is maintained about 1/N of the frequency of the Nth harmonic resonator 7. In the Colpitts oscillator shown the capacitors 2 and 3 and inductor 5 may not be required at high frequencies when the stray capacitances between the collector-emitter and emitter-base and inductance of the leads are sufficient. The oscillator may be a Hartley circuit, a collector tuned circuit or a base tuned circuit. The Nth harmonic resonator 7 may be a lumped constant element or a distributed constant element such as a cavity resonator or coaxial resonator. In an equivalent circuit of the oscillator (Fig. 2, not shown), the resonator 7 is shown as a series inductor (28) and capacitor (27). In a further equivalent circuit (Fig. 3, not shown), the resonator 7 is represented by a resistor (39) an inductor (38) and a capacitor (37) connected to the input side of the multiplying circuit. Phase changes in the oscillating current flowing back to the emitter of the transistor (31) due to a change of parameters of the transistor due to variation of the power supply are compensated for by the resistor (39), inductor (38) and capacitor (37) of the equivalent circuit of the resonator 7. The high effective Q of the Nth harmonic resonator 7 may be obtained by loose coupling between its input and output such that the oscillating frequency is stabilized (curve A, Fig. 4, not shown). Variation of the capacitor 4 alters the fundamental oscillating frequency of the transistor 1 (curve C, Fig. 5, not shown), and the action of the resonator 7 is effectively to pull the oscillating frequency to a stable value (curve D). The output frequency may be the second harmonic and when the resonator 7 has an effective Q of 1500 the temperature characteristic of the oscillating frequency is related to the temperature co-efficient of the material of the resonator. Specification 1,031,399 is referred to.