Low noise oscillators and tracking filters
AssigneeNorthern Telecom Limited
InventorAnthony K. D. Brown
Life of this patent
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Abstract
A gyrator based resonator comprises first and second differential amplifiers cross coupled to form a quadrature phase voltage controlled oscillator. The differential amplifier circuits include matched transistor pairs and associated transconductance adjusting components to control the resonant frequency of the resonator. Transconductance delay and admittance loss elements are also provided and these elements serve to control the loop gain of the resonator. A loop gain greater than unity results in the resonator oscillating while a loop gain less than unity produces a bandpass filter. A resonator having gain less than unity may be slaved to a similar resonator having gain adjusted to be greater than unity thus creating a low noise oscillator and tracking filter.
Claims23
A gyrator based resonator comprising:
- first and second differential amplifiers each having:
- a current source for supplying a substantially constant bias source:
- a current dividing circuit for controllably dividing the substantially constant bias source between first and second current paths;
- a pair of matched load impedances;
- a first pair of matched transistors connected as a differential pair between the matched load impedances and the first current path;
- a second pair of matched transistors connected as a differential pair between the matched load impedances and the second current path, with differential inputs of the second differential pair connected to corresponding differential inputs of the first differential pair and;
- a third pair of transistors associated with one of said first or second pairs of matched transistors to control the transconductance delay thereof.
A gyrator based resonator comprising;
- a pair of interconnected transconductance elements, transconductance delay means associated with said transconductance elements to control the transconductance delay. of said resonator and adjustable loss admittance means.
Dependencies are inferred from the claim text.