Slow switch for bandwidth change in phase-locked loop

Claim 2

A phase-locked loop for recovering a periodic signal from a received signal in the presence of noise and other undesired signal components comprising in combination: a phase detector having an input for receiving said received signal; a variable frequency oscillator for providing a variable frequency signal to an input of said phase detector, the frequency of said variable frequency signal being determined by a control signal; a narrow loop filter for cutting off signals having a frequency above a first value connecting the output of said phase detector to the input of said variable frequency oscillator at all times; a wide loop filter for cutTing off signals having a frequency above a second value, with said second value being substantially greater than said first value, said wide loop filter connected to receive the output of said phase detector; variable impedance means connected between the output of said narrow loop filter and the output of said wide loop filter; and control means for increasing or decreasing the impedance of said variable impedance means at a controlled rate so as to smoothly shift emphasis of control of the variable frequency oscillator from the wide loop filter to the narrow loop filter for accurate and smooth phase locking.

Claim 3

The phase-locked loop of claim 1 wherein said control means is comprised of: a current source connected to said variable impedance for changing the impedance of said variable impedance as a function of current; and a charging circuit connected in circuit with said current source, said charging circuit being activated when the phase-locked loop is within the acquisition range of said narrow loop filter for causing the current flow in said current source to increase smoothly.

Claim 4

The phase-locked loop of claim 2 wherein said variable impedance means is a field effect transistor the gate of which is connected in circuit to said current source, the drain of which is connected in circuit to the output of said wide loop filter, the source of which is connected in circuit to the output of said narrow loop filter and the resistance of which is a function of the voltage applied to said gate.

Claim 5

The phase-locked loop of claim 3 also including a pair of diodes for connecting the drain and the source, respectively, of said field effect transistor to said current source.

Claim 6

A phase-locked loop for recovering a periodic signal from a received signal in the presence of noise and other undesired signal components comprising in combination: a phase detector having an input for receiving said received signal; a variable frequency oscillator for providing a variable frequency signal to an input of said phase detector, the frequency of said variable frequency signal being determined by a control signal; a narrow loop filter for cutting off signals having a frequency above a first value connected to receive the output of said phase detector; a first amplifier connecting the output of said narrow loop filter to the input of said variable frequency oscillator at all times; a wide loop filter for cutting off signals having a frequency above a second value, with said second value being substantially greater than said first value, said wide loop filter connected to receive the output of said phase detector; a second amplifier connected to receive the output of said wide loop filter; a variable impedance means connected between the output of said second amplifier and the output of said narrow loop filter; and a control means for increasing or decreasing the impedance of said variable impedance means at a controlled rate so as to smoothly shift emphasis of control of the variable frequency oscillator from the wide loop filter to the narrow loop filter for accurate and smooth phase locking.

Claim 7

A phase-locked loop for recovering a periodic signal from a received signal in the presence of noise and other undesired signal components comprising in combination: a phase detector having an input for receiving said received signal; a variable frequency oscillator for providing a variable frequency signal to an input of said phase detector, the frequency of said variable frequency signal being determined by a control signal; a narrow loop filter for cutting off signals having a frequency above a first value connected to receive the output of said phase detector; a first amplifier connecting the output of said narrow loop filter to the input of said variable frequency oscillator at all times; a wide loop filter for cutting off signals having a frequency above a second value, with said second value being substantially greater than said first value, said wide loop filter connected to receive the output of said phase detector; a second amplifier connected to receive the output of said wide loop filter; a variable impedance means connected between the output of said second amplifier and the output of said narrow loop filter; and a control means for increasing or decreasing the impedance of said variable impedance means at a controlled rate so as to smoothly shift emphasis of control of the variable frequency oscillator from the wide loop filter to the narrow loop filter for accurate and smooth phase locking.

Claim 8

A phase-locked loop for recovering a periodic signal from a received signal in the presence of noise and other undesired signal components comprising in combination: a phase detector having an input for receiving said received signal; a variable frequency oscillator for providing a variable frequency signal to an input of said phase detector, the frequency of said variable frequency signal being determined by a control signal; a narrow loop filter for cutting off signals having a frequency above a first valve connected to receive the output of said phase detector; a wide loop filter for cutting off signals having a frequency above a second value, with said second value being substantially greater than said first value, said wide loop filter connected to receive the output of said phase detector; a fiRst amplifier connecting the output of said narrow loop filter to the input of said variable frequency oscillator at all times; a second amplifier connected to receive the output of said wide loop filter; a current source; a charging circuit connected in circuit with said current source, said charging circuit being activated when the phase-locked loop is within acquisition range of said narrow loop filter for causing the current flow in said current source to increase; and a field effect transistor the gate of which is connected in circuit to said current source, the drain of which is connected to the output of said second amplifier, the source of which is connected to the output of the narrow loop filter, and the resistance of which is a function of the voltage applied to said gate.

Claim 9

A phase-locked loop for recovering a periodic signal from a received signal in the presence of noise and other undesired signal components comprising in combination: a phase detector having an input for receiving said received signal; a variable frequency oscillator for providing a variable frequency signal to an input of said phase detector, the frequency of said variable frequency signal being determined by a control signal; a narrow loop filter for cutting off signals having a frequency above a first valve connected to receive the output of said phase detector; a wide loop filter for cutting off signals having a frequency above a second value, with said second value being substantially greater than said first value, said wide loop filter connected to receive the output of said phase detector; a fiRst amplifier connecting the output of said narrow loop filter to the input of said variable frequency oscillator at all times; a second amplifier connected to receive the output of said wide loop filter; a current source; a charging circuit connected in circuit with said current source, said charging circuit being activated when the phase-locked loop is within acquisition range of said narrow loop filter for causing the current flow in said current source to increase; and a field effect transistor the gate of which is connected in circuit to said current source, the drain of which is connected to the output of said second amplifier, the source of which is connected to the output of the narrow loop filter, and the resistance of which is a function of the voltage applied to said gate.

Claim 10

The phase-locked loop of claim 6 also including a pair of diodes for connecting the drain and source, respectively, of said field effect transistor to said current source.

Claim 11

Apparatus for recovering a desired signal component from a received signal containing undesired signal components, comprising: a phase detector having a first input for receiving said signal; a variable frequency oscillator for providing a second input signal to said phase detector, the frequency of said second input signal being determined by a control signal applied to a control input of said oscillator; a first filter means having a first frequency response coupling the ouput of said phase detector to said control input of said oscillator at all times; a second filter means having a second frequency response and also connected to receive the output of said phase detector; variable impedance means coupled between the outputs of said first and second filter means; and means for varying the value of said impedance means to effectively shift emphasis of control of said oscillator from one of said filter means to the other.

Claim 12

Apparatus for recovering a desired signal component from a received signal containing undesired signal components, comprising: a phase detector having a first input for receiving said signal; a variable frequency oscillator for providing a second input signal to said phase detector, the frequency of said second input signal being determined by a control signal applied to a control input of said oscillator; a first filter means having a first frequency response coupling the ouput of said phase detector to said control input of said oscillator at all times; a second filter means having a second frequency response and also connected to receive the output of said phase detector; variable impedance means coupled between the outputs of said first and second filter means; and means for varying the value of said impedance means to effectively shift emphasis of control of said oscillator from one of said filter means to the other.