Mplitude phase locked loop with non linear filter responsive to error signal a

Claim 2

In a phase locked loop system wherein the frequency of the signal produced by a controlled oscillator is compared in a phase detector with a reference signal to produce a control voltage for said oscillator, said control voltage having a direct voltage component depending on the displacement between the signal produced by said oscillator and the reference signal, a transmission path for said control voltage from said detector to said oscillator including network means for increasing the gain of said path for said direct voltage component without proportionally increasing the response of said path to substantially higher frequency alternating components when the absolute amplitude of said control voltage component is less than a given value.

Claim 3

The system of claim 1 wherein said network means comprises a reactive phase-lag filter network and means for shunting said filter network with a shunting resistance when said absolute amplitude exceeds said given value.

Claim 4

The system of claim 2 wherein said phase-lag filter includes the series combination of a first resistance and a capacitance and wherein said means for shunting connects said shunting resistance across said capacitance and at least part of said first resistance.

Claim 5

The system according to claim 3 wherein the components of said filter and said shunting resistance are proportioned to increase the frequency difference between the corner frequencies of the filter characteristic when said absolute amplitude is less than said given value and to decrease said difference when said absolute amplitude is greater than said given value.

Claim 6

The system of claim 2 wherein said means for shunting includes a first back biased diode poled to connect said shunting resistance in shunt with said filter network when the amplitude of said control voltage exceeds said bias in one sense and a second back biased diode poled to connect said shunting resistance in shunt with said filter network when the amplitude of said control voltage exceeds said bias in the other sense.

Claim 7

In a transmission system for bipolar pulses having a substantially continuous power spectrum, means for recovering timing information from baseband pulses which comprises a full wave rectifier to which said pulses are appLied, means for filtering said pulses as rectified with a bandpass characteristic centered upon the expected timing frequency of said pulses, an oscillator included in a phase locked loop, means for applying said filter output as the reference signal to said loop, said loop having a nonlinear characteristic that increases the direct current gain of said loop when the displacement between said oscillator and said reference signal is small without proportionally increasing the response of said loop to substantially higher frequency alternating currents.

Claim 8

In a transmission system for bipolar pulses having a substantially continuous power spectrum, means for recovering timing information from baseband pulses which comprises a full wave rectifier to which said pulses are appLied, means for filtering said pulses as rectified with a bandpass characteristic centered upon the expected timing frequency of said pulses, an oscillator included in a phase locked loop, means for applying said filter output as the reference signal to said loop, said loop having a nonlinear characteristic that increases the direct current gain of said loop when the displacement between said oscillator and said reference signal is small without proportionally increasing the response of said loop to substantially higher frequency alternating currents.