Filter circuitry for voltage controlled oscillator
AssigneeNational Semiconductor Corporation
InventorMark Alan Jones
Life of this patent
Estimating the term…
Abstract
The controlling circuit element of a voltage controlled oscillator (VCO) for use in a phase lock loop (PLL) is a varactor connected between the terminals used to convey the power supply voltage and the frequency control voltage. The loop filter, implemented in a shunt configuration at the input of the VCO, is also connected between the power supply and frequency control voltage terminals. As a result, any variations in the power supply voltage appear at both terminals of the varactor due to the voltage coupling effect of the loop filter between the shared power supply and frequency control voltage terminals.
Claims18
An apparatus including a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- a power supply terminal that conveys a power supply voltage having a magnitude and polarity relative to a reference potential;
- a control terminal that conveys a control voltage for varactor circuitry, wherein, relative to said reference potential, said control voltage has a polarity equal to said power supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude;
- and
- shunt filter circuitry, connected to and between said power supply and control terminals, that filters said control voltage.
An apparatus including, a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- a power supply terminal that conveys a power supply voltage having a magnitude and polaritve relative to a reference potential;
- a control terminal that conveys a control voltage for varactor circuitry;
- wherein, relative to said reference potential, said control voltage has a polarity equal to said poster supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude;
- and
- shunt filter circuitry, connected between said power supply and control terminals, that filters said control voltage, wherein said shunt filter circuitry comprises a low pass filter circuit.
An apparatus including a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- a power supply terminal that conveys a power supply voltage having a
- magnitude and polarity relative to a reference potential;
- a control terminal that conveys a control voltage for varactor circuitry, wherein, relative to said reference potential, said control voltage has a polarity equal to said power supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude;
- shunt filter circuitry, connected between said power supply and control terminals, that filters said control voltage;
- and
- charge pump circuitry, connected to said control terminal, that in cooperation with said shunt filter circuitry generates said control voltage.
An apparatus including a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- a power supply terminal that conveys a power supply voltage having a magnitude and polarity relative to a reference potential;
- a control terminal that conveys a control voltage for varactor circuitry, wherein, relative to said reference potential, said control voltage has a polarity equal to said power supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude;
- shunt filter circuitry, connected to and between said power supply and control terminals, that filters said control voltage;
- a reference terminal that establishes said reference potential;
- and
- voltage controlled oscillator circuitry, connected between said power supply, reference and control terminals, that in response to said control voltage generates a voltage controlled oscillation signal, wherein said voltage controlled oscillator circuitry comprises
- bias circuitry, connected between said power supply and reference terminals, that in response to said power supply voltage, generates a bias signal, and
- resonant circuitry, connected between selected ones of said power supply terminal, reference terminal, control terminal and bias circuitry, that in response to said bias signal and said control voltage generates said voltage controlled oscillation signal.
An apparatus including a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- a power supply terminal that conveys a power supply voltage having a magnitude and polarity relative to a reference potential;
- a control terminal that conveys a control voltage for varactor circuitry, wherein, relative to said reference potential, said control voltage has a polarity equal to said power supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude;
- shunt filter circuitry, connected between said power, supply and control terminals, that filters said control voltage;
- a reference terminal that establishes said reference potential;
- voltage controlled oscillator circuitry, connected between said power supply, reference and control terminals, that in response to said control voltage generates a voltage controlled oscillation signal;
- and
- charge pump circuitry, connected to said control terminal, that in cooperation with said shunt filter circuitry generates said control voltage.
An apparatus including a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- power supply means for conveying a power supply voltage having a magnitude and polarity relative to a reference potential;
- control means for conveying a control voltage for varactor circuitry, wherein, relative to said reference potential, said control voltage has a polarity equal to said power supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude;
- and
- shunt filter means, for filtering said control voltage between said power supply and control terminals.
An apparatus including a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- power supply means for conveying a power supply voltage having a magnitude and polarity relative to a reference potential;
- control means for conveying a control voltage for varactor circuitry, wherein, relative to said reference potential, said control voltage has a polarity equal to said power supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude;
- shunt filter means, for filtering said control voltage between said power supply and control terminals;
- and
- charge pump means for generating said control voltage in cooperation with said shunt filter means.
An apparatus including a filter circuit for filtering a control voltage used to control varactor circuitry in a voltage controlled oscillator, comprising:
- power supply means for conveying a power supply voltage having a magnitude and polarity relative to a reference potential;
- control means for conveying a control voltage for varactor circuitry, wherein, relative to said reference potential, said control voltage has a polarity equal to said power supply voltage polarity and a magnitude less than or equal to said power supply voltage magnitude:
- shunt filter means, for filtering said control voltage between said power supply and control terminals;
- reference means for establishing said reference potential;
- voltage controlled oscillator means for responding to said control voltage by generating a voltage controlled oscillation signal;
- and
- charge pump means for generating said control voltage in cooperation with said shunt filter means.
Dependencies are inferred from the claim text.