Oscillator circuit

An oscillator circuit comprising:

• an oscillator transistor having respective first, second, and control terminals, said oscillator transistor being arranged to generate a microwave oscillating signal at the first terminal thereof;
• a surface integrated waveguide resonator connected to the second terminal of the oscillator transistor;
• an active bias circuit portion comprising a negative feedback arrangement between the first terminal of the oscillator transistor and the control terminal of the oscillator transistor, the active bias circuit portion being arranged to supply a bias current to the control terminal of the oscillator transistor, wherein said bias current is dependent on a voltage at the first terminal of the oscillator transistor multiplied by a negative gain;
• a second feedback transistor having respective first, second, and control terminals, said second feedback transistor being arranged such that:
• the first terminal of the second feedback transistor is connected to the supply voltage via a fifth resistor;
• the second terminal of the second feedback transistor is connected to the control terminal of a first feedback transistor;
• and
• the control terminal of the second feedback transistor is connected to the first terminal of the first feedback transistor via a third feedback path;
• optionally wherein the fifth resistor has a first terminal thereof connected to the first terminal of the second feedback transistor, and a second terminal thereof connected to the supply voltage and to the first terminal of the first resistor in a first feedback path.

An oscillator circuit comprising:

• an oscillator transistor having respective first, second, and control terminals, said oscillator transistor being arranged to generate a microwave oscillating signal at the first terminal thereof;
• a surface integrated waveguide resonator connected to the second terminal of the oscillator transistor;
• an active bias circuit portion comprising a negative feedback arrangement between the first terminal of the oscillator transistor and the control terminal of the oscillator transistor, the active bias circuit portion being arranged to supply a bias current to the control terminal of the oscillator transistor, wherein said bias current is dependent on a voltage at the first terminal of the oscillator transistor multiplied by a negative gain;
• first, second, and third microstrip lines, arranged such that:
• the first microstrip line has a first end thereof connected to the control terminal of the oscillator transistor, and a second end thereof is open-ended;
• the second microstrip line has a first end thereof connected to the first end of the first microstrip line and the control terminal of the oscillator transistor;
• and
• the third microstrip line has a first end thereof connected to a second end of the second microstrip line, and a second end thereof is open-ended;
• wherein the first end of the third microstrip line and second end of the second microstrip line are connected to the active bias circuit.

An oscillator circuit comprising:

• an oscillator transistor having respective first, second, and control terminals, said oscillator transistor being arranged to generate a microwave oscillating signal at the first terminal thereof;
• a surface integrated waveguide resonator connected to the second terminal of the oscillator transistor;
• and
• an active bias circuit portion comprising a negative feedback arrangement between the first terminal of the oscillator transistor and the control terminal of the oscillator transistor, the active bias circuit portion being arranged to supply a bias current to the control terminal of the oscillator transistor, wherein said bias current is dependent on a voltage at the first terminal of the oscillator transistor multiplied by a negative gain;
• fourth and fifth microstrip lines, arranged such that:
• the fourth microstrip line has a first end thereof connected to the first terminal of the oscillator transistor;
• and
• the fifth microstrip line has a first end thereof connected to a second end of the fourth microstrip line, and a second end thereof is open-ended.

An oscillator circuit comprising:

• an oscillator transistor having respective first, second, and control terminals, said oscillator transistor being arranged to generate a microwave oscillating signal at the first terminal thereof;
• a surface integrated waveguide resonator connected to the second terminal of the oscillator transistor;
• an active bias circuit portion comprising a negative feedback arrangement between the first terminal of the oscillator transistor and the control terminal of the oscillator transistor, the active bias circuit portion being arranged to supply a bias current to the control terminal of the oscillator transistor, wherein said bias current is dependent on a voltage at the first terminal of the oscillator transistor multiplied by a negative gain;
• a bandpass filter connected between the first terminal of the oscillator transistor and an output terminal of the oscillator circuit;
• optionally further comprising a sixth microstrip line having a first end thereof connected to an input of the bandpass filter and to the first terminal of the oscillator transistor, and a second end thereof is open ended;
• and/or
• optionally further comprising a seventh microstrip line having a first end thereof connected to an output of the bandpass filter and to an output terminal of the oscillator circuit, and a second end thereof is open ended.

An oscillator circuit comprising:

• an oscillator transistor having respective first, second, and control terminals, said oscillator transistor being arranged to generate a microwave oscillating signal at the first terminal thereof;
• a surface integrated waveguide resonator connected to the second terminal of the oscillator transistor;
• an active bias circuit portion comprising a negative feedback arrangement between the first terminal of the oscillator transistor and the control terminal of the oscillator transistor, the active bias circuit portion being arranged to supply a bias current to the control terminal of the oscillator transistor, wherein said bias current is dependent on a voltage at the first terminal of the oscillator transistor multiplied by a negative gain;
• a ninth microstrip line connected between the first terminal of the oscillator transistor and an output terminal of the oscillator circuit.