Tuning circuit having electronically trimmed VCO
AssigneeTexas Instruments Incorporated
InventorsBiagio Bisanti, Francesco Coppola, Pascal Guignon
Life of this patent
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Abstract
A voltage controlled oscillator (38) includes an LC tank (20) and a capacitor bank (21). LC tank (20) includes an inductor (12) and a varactor (14). The capacitive output of the varactor is controlled by a control voltage ν. To electronically tune the voltage controlled oscillator, a set of capacitors (24) in the capacitor bank (21) are enabled by a digital control signal based on a frequency comparison with a desired frequency. Once the capacitor bank is set, the frequency can be locked at the desired frequency by the phase lock loop.
Claims22
A tuning circuit, comprising:
- a phase frequency detector having a first input, a second input, and an output;
- a filter coupling said output of said phase detector to an input of a voltage controlled oscillator (VCO) said voltage controlled oscillator comprising:
- an inductive element coupled to said input of said voltage controlled oscillator;
- a variable capacitive element coupled to said inductive element;
- and
- a bank of switched capacitors coupled to said inductive element and said variable capacitive element;
- and
- a frequency divider coupling said second input of said phase frequency detector to an output of said voltage controlled oscillator (VCO).
A tuning circuit, comprising:
- a phase frequency detector having a first input, a second input, and an output;
- a filter coupling said output of said phase detector to an input of a voltage controlled oscillator (VCO), said voltage controlled oscillator comprising:
- an inductive element coupled to said input of said voltage controlled oscillator;
- a variable capacitive element coupled to said inductive element;
- and
- a bank of switched capacitors coupled to said inductive element and said variable capacitive element;
- a frequency divider coupling said second input of said phase frequency detector to an output of said voltage controlled oscillator;
- and
- control circuitry for enabling a set of said switched capacitors responsive to a desired frequency, wherein said control circuitry comprises frequency comparison circuitry for comparing an output frequency of the voltage controlled oscillator with a reference frequency.
A tuning circuit, comprising:
- a phase frequency detector having a first input, a second input, and an output;
- a filter coupling said output of said phase detector to an input of a voltage controlled oscillator (VCO);
- a frequency divider coupling said second input of said phase frequency detector to an output of said voltage controlled oscillator (VCO);
- logic circuitry coupled to said voltage controlled oscillator (VCO);
- and
- a second frequency divider coupling said output of said voltage controlled oscillator (VCO) to a frequency detector, said frequency detector being further coupled to said logic circuitry.
A tuning circuit, comprising:
- a phase frequency detector having a first input, a second input, and an output;
- a filter coupling said output of said phase detector to an input of a voltage controlled oscillator (VCO);
- a frequency divider coupling said second input of said phase frequency detector to an output of said voltage controlled oscillator (VCO);
- a second frequency divider coupled to said output of said voltage controlled oscillator (VCO);
- and
- a switch coupling a voltage source to said input of said voltage controlled oscillator (VCO).
Dependencies are inferred from the claim text.