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16 is an equivalent circuit diagram of the seventh embodiment.įIG. 15 is a MMIC (Monolithic Microwave Integrated Circuit) chip pattern diagram of a microwave oscillator of a seventh embodiment.įIG. 14 is a graph showing a characteristic of the sixth embodiment.įIG. 13 is a circuit diagram of a microwave oscillator of a sixth embodiment.įIG. 12 is a graph showing a characteristic of the fifth embodiment.įIG. 11 is a circuit diagram of a microwave oscillator of a fifth embodiment.įIG. 10 is a diagram showing a characteristic of the fourth embodiment.įIG. 9 is a circuit diagram of a microwave oscillator of a fourth embodiment.įIG. 8 is a a diagram showing a characteristic of the third embodiment.įIG. 7 is a graph showing a characteristic of the third embodiment.įIG. 6 is a circuit diagram of a microwave oscillator of a third embodiment.įIG. 5 is a graph showing a characteristic of the second embodiment.įIG. 4 is a circuit diagram of a microwave oscillator of a second embodiment.įIG. 3 is a graph showing a characteristic curve of the first embodiment.įIG. 2 is a circuit diagram of a microwave oscillator of a first embodiment.įIG. 1 is the circuit diagram of the prior art microwave oscillator.įIG. The microwave oscillator in accordance with the present invention comprises:Ī microwave resonator connected to the gate of the FET,Īn inductive element connected by one end to the drain of the FET, and grounded by the other end thereof with respect to the microwave frequency, andĪn output terminal connected to the source of the FET. The present invention intends to provide an improved microwave oscillator which can stably oscillate even when any FET 1 other than usually used package FET 1 is used. Therefore, the stability of the oscillation is lowered. In the above-mentioned prior art circuit configuration, however, when the FET 1a is configurated in a shape of a chip, or when the whole circuit is configurated in a monolithic integrated circuit, there arises a problem such that the negative resistance to be presented at the gate 11a is decreased, due to a decrease or elimination of the stray capacity which has existed in case of the prior art package 1. The output of the oscillation signal is issued through the output terminal 10a. According to the above-mentioned circuit configuration, oscillation is produced by cooperation of a negative resistance produced at the gate 11a and a resonance circuit consisting of the strip line 4a, and the dielectric resonator 5a coupled to the strip line 4a. When a DC power source is supplied from the power terminal 3a, the potential of the gate 11a becomes lower than the potential of the source 13a, as a result of voltage drop caused by a current flowing through the self bias resistor 8a. In the conventional microwave oscillator of the above-mentioned configuration, the 1/4 wavelength open ended transmission line 19a grounds the drain 12a in microwave frequency. A dielectric resonator 5a is coupled to the strip line 4a. Drain 12a is connected to a power source terminal 3a and also to one end of openended transmission line 19a having a length of a quarter wavelength.
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The source 13a of FET 1a is connected to an output terminal 10a and also through a low pass filter 7a and a self bias resistor 8a to the ground. 1 is a circuit diagram of the conventional microwave oscillator of the above-mentioned application, wherein an FET 1a is connected by its gate 11a to one end of a strip line 4a, the other end thereof being terminated by a dummy resistor 6a. The present invention relates generally to a microwave oscillator and particularly to an improved microwave oscillator capable of stable oscillation even when a FET is used therein which is other than a package FET.Ī conventional microwave oscillator has been disclosed, for instance, in Japanese Published Unexamined Patent Application No.