Local oscillator with reduced harmonic
AssigneeDelco Electronics Corporation
InventorStuart B. Sanders
Life of this patent
Estimating the term…
Abstract
An apparatus suitable for use as a local oscillator is disclosed, which includes (a) a tank circuit operatively associated with an FET to generate a fundamental frequency oscillating signal at an output of the FET and (b) a bi-directional clamp circuit coupled at a junction between the tank circuit and a gate of the FET to limit a swing of the gate of the FET, preventing the gate of the FET from entering either a saturation region or a cut-off region. The bi-directional clamp includes a first diode coupled to allow positive current to flow to the junction and a second diode coupled to allow positive current to flow away from the junction. The oscillator produces an output with a reduced level of radiation-prone harmonics.
Claims5
An apparatus comprising:
- a field effect transistor (FET) having a source, a gate, and a drain;
- tank circuit means coupled to the gate and drain of the FET for causing a fundamental frequency oscillating signal to be generated at the source of the FET;
- and
- a bi-directional clamp circuit having first and second diodes connected in parallel, each diode allowing current flow in a direction opposite to current flow in the other diode, the bi-directional clamp circuit coupled to the gate of the FET to limit a swing of a gate voltage of the FET, preventing the gate voltage of the FET from entering a saturation region and a cut-off region.
An apparatus comprising:
- (a) a tank circuit including, in parallel, an inductor, a capacitor and a tunable varactor, the inductor having a tap;
- (b) a field effect transistor (FET) having a source, a gate and a drain;
- (c) a filter circuit coupling the tap in the inductor to the drain of the FET, the filter circuit comprising, in parallel, a resistor and a capacitor;
- (d) a resistor coupling the gate of the FET to an output of the tank, a first end of the resistor connected to the output of the tank at a first node and a second end of the resistor connected to the gate of the FET at a second node;
- (e) a bi-directional clamp circuit having first and second diodes connected in parallel, each diode allowing current flow in a direction opposite to current flow in the other diode, the bidirectional clamp coupled between the first node and ground;
- and
- (f) a circuit output coupled to the FET source, at which is output an oscillator output signal having a low level of radiation-prone harmonics.
Dependencies are inferred from the claim text.