Noise suppression processor for a carrier tracking loop

Claim 3

An apparatus, as in claim 2, in which the means for processing limits values of the amplified loop error signal which are greater than or equal to 1.2A to a predetermined maximum value of 1.2A and limits values of the amplified loop error signal which are less than or equal to -1.2A to a predetermined minimum value of -1.2A.

Claim 6

An apparatus, as in claim 3, in which the means for processing comprises: a first multiplier responsive to the loop error signal E 0 (t) for producing an output signal equal to E 0 2 (t); a second multiplier response to the loop error signal E 0 (t) and the output signal of the first multiplier for producing an output signal equal to E 0 3 (t); an amplifier responsive to the output signal of the second multiplier for producing an output signal equal to E 0 3 (t)/η; a summer responsive to the loop error signal E 0 (t) and the output signal of the amplifier for producing an output signal to E 0 (t)+E 0 3 (t)/η; and a limiter responsive to the output signal of the summer of producing the processed loop error signal, the processed loop error signal being equal to 1.2A for values of the output signal of the summer which are greater than or equal to 1.2A, equal to the output signal of the summer for values of the output signal of the summer greater than -1.2A and less than 1.2A, and equal to -1.2A for values of the output signal of the summer which are less than or equal to -1.2A.

Claim 7

An apparatus, as in claim 3, in which the means for processing comprises a digital processor which implements the transfer function according to stored program.

Claim 8

A carrier tracking loop for use in a receiver which measures range changes from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) by 1+E 0 2 (t)/η to produce an amplified loop error signal given by E 0 (t)+E 0 3 (t)/η, where: n=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; and a loop filter responsive to the processed loop error signal for producing a control signal.

Claim 9

A carrier tracking loop for use in a receiver which measures range changes from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) by 1+E 0 2 (t)/η to produce an amplified loop error signal given by E 0 (t)+E 0 3 (t)/η, where: n=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; and a loop filter responsive to the processed loop error signal for producing a control signal.

Claim 10

A carrier tracking loop, as in claim 6, in which the means for processing limits values of the amplified loop error signal which are greater than or equal to 1.2A to a predetermined maximum value of 1.2A and limits values of the amplified loop error signal which are less than or equal to -1.2A to a predetermined minimum value of -1.2A.

Claim 11

A carrier tracking loop for use in a receiver which measures range changes from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) according to the transfer function N[E 0 (t)] given by: ##EQU5## where: η=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; and a loop filter responsive to the processed loop error signal for producing a control signal.

Claim 12

A carrier tracking loop for use in a receiver which measures range changes from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) according to the transfer function N[E 0 (t)] given by: ##EQU5## where: η=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; and a loop filter responsive to the processed loop error signal for producing a control signal.

Claim 13

A carrier tracking loop, as in claim 8, in which the means for processing comprises: a first multiplier responsive to the loop error signal E 0 (t) for producing an output signal equal to E 0 2 (t); a second multiplier response to the loop error signal E 0 (t) and the output signal of the first multiplier for producing an output signal equal to E 0 3 (t); an amplifier responsive to the output signal of the second multiplier for producing an output signal equal to E 0 3 (t)/η; a summer responsive to the loop error signal E 0 (t) and the output signal of the amplifier for producing an output signal to E 0 (t)+E 0 3 (t)/η; and a limiter responsive to the output signal of the summer of producing the processed loop error signal, the processed loop error signal being equal to 1.2A for values of the output signal of the summer which are greater than or equal to 1.2A, equal to the output signal of the summer for values of the output signal of the summer greater than -1.2A and 1.2A, and equal to -1.2A for values of the output signal of the summer which are less than or equal to -1.2A.

Claim 14

A carrier tracking loop, as in claim 8, in which the means for processing comprises a digital processor which implements the transfer function according a stored program.

Claim 15

A carrier tracking loop, as is claim 6, further comprising an oscillator responsive to the control signal for producing the second signal, the first signal being received from the remote transmitter.

Claim 16

A receiver for measuring range changes from a remote transmitter, comprising: a means for receiving a signal from a remote transmitter; a carrier tracking loop for tracking the phase of the received signal, the carrier tracking loop comprising a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals, a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) by 1+E 0 2 (t)/η, where: n=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise, and a loop filter responsive to the processed loop error signal for producing a control signal; and a means responsive to the control signal for determining range changes from the remote transmitter.

Claim 17

A receiver for measuring range changes from a remote transmitter, comprising: a means for receiving a signal from a remote transmitter; a carrier tracking loop for tracking the phase of the received signal, the carrier tracking loop comprising a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals, a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) by 1+E 0 2 (t)/η, where: n=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise, and a loop filter responsive to the processed loop error signal for producing a control signal; and a means responsive to the control signal for determining range changes from the remote transmitter.

Claim 18

A receiver, as in claim 12, in which the means for processing limits values of the amplified loop error signal which are greater than or equal to 1.2A to a predetermined maximum value of 1.2A and limits values of the amplified loop error signal which are less than or equal to -1.2A to a predetermined minimum value of -1.2A.

Claim 19

A carrier tracking loop for use in a receiver which measures range changes from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; a loop filter responsive to the processed loop error signal for producing a control signal; a first band pass filter responsive to a third signal received from the remote transmitter for producing an output signal; a means for squaring the output signal of the first bandpass filter; a second band pass filter responsive to the squared output signal for producing the first signal; and an oscillator responsive to the control signal for producing the second signal.

Claim 20

A carrier tracking loop for use in a receiver which measures range changes from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; a loop filter responsive to the processed loop error signal for producing a control signal; a first band pass filter responsive to a third signal received from the remote transmitter for producing an output signal; a means for squaring the output signal of the first bandpass filter; a second band pass filter responsive to the squared output signal for producing the first signal; and an oscillator responsive to the control signal for producing the second signal.

Claim 21

A carrier tracking loop for use in a receiver which measures range change from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; a loop filter responsive to the processed loop error signal for producing a control signal; an in-phase detector responsive to a third signal received from the remote transmitter and a fourth signal for producing an output signal; a filter responsive to the output signal from the in-phase detector for producing the first signal; a quadrature phase detector responsive to the third signal received from the remote receiver and a fifth signal for producing an output signal; a filter responsive to the output signal of the quadrature phase detector for producing the second signal; an oscillator responsive to the control signal for producing the fourth signal; and a phase shifter responsive to the fourth signal for producing the fifth signal.

Claim 22

A carrier tracking loop for use in a receiver which measures range change from a remote transmitter, comprising: a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals; a means for processing the loop error signal by nonlinearly amplifying the loop error signal and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise; a loop filter responsive to the processed loop error signal for producing a control signal; an in-phase detector responsive to a third signal received from the remote transmitter and a fourth signal for producing an output signal; a filter responsive to the output signal from the in-phase detector for producing the first signal; a quadrature phase detector responsive to the third signal received from the remote receiver and a fifth signal for producing an output signal; a filter responsive to the output signal of the quadrature phase detector for producing the second signal; an oscillator responsive to the control signal for producing the fourth signal; and a phase shifter responsive to the fourth signal for producing the fifth signal.

Claim 23

A receiver for measuring range changes from a remote transmitter, comprising: a means for receiving a signal from a remote transmitter; a carrier tracking loop for tracking the phase of the received signal, the carrier tracking loop comprising a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals, a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) according to the transfer function N[E 0 (t)] given by: ##EQU6## where: η=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise, and a loop filter responsive to the processed loop error signal for producing a control signal; and a means responsive to the control signal for determining range changes from the remote transmitter.

Claim 24

A receiver for measuring range changes from a remote transmitter, comprising: a means for receiving a signal from a remote transmitter; a carrier tracking loop for tracking the phase of the received signal, the carrier tracking loop comprising a phase detector responsive to first and second signals for producing a loop error signal related to the phase difference between the first and second signals, a means for processing the loop error signal by nonlinearly amplifying the loop error signal E 0 (t) according to the transfer function N[E 0 (t)] given by: ##EQU6## where: η=A 2 /π, and A=maximum noiseless amplitude of error signal E 0 (t), and limiting the amplified loop error signal to predetermined maximum and minimum values to maintain the carrier tracking loop in lock in the presence of noise, and a loop filter responsive to the processed loop error signal for producing a control signal; and a means responsive to the control signal for determining range changes from the remote transmitter.

Claim 25

A carrier tracking loop, as in claim 8, further comprising an oscillator responsive to the control signal for producing the second signal, the first signal being received from the remote transmitter.