Receiver for pulse modulated signals

Claim 2

An improved radio receiver for receiving pulse modulated carrier signals comprising at least one radio frequency amplifier, a detector stage, and at least one audio stage, a peak detector circuit connected to receive signals from said radio frequency amplifier and operable to detect signal peaks and to set a control signal level determined by the amplitudes of said peaks, said peak detector being connected in a control loop to automatically control the gain of said radio frequency amplifier in accordance with said control signal level to prevent overloading of the receiver to thereby prevent signal distortion and clipping, a normalizing circuit connected between said detector stage and said audio stage, said normalizing circuit comprising a variable scale factor circuit means connected to receive signals from said detector stage; said normalizing circuit also including a normalizing amplifier connected to supply signals to said audio stage, means serially connecting said normalizing amplifier to receive signals from said variable scale factor circuit means, and means connected from the output of said normalizing amplifier to control said variable scale factor circuit means, said scale factor circuit means being operable in response to the direct current level component of the output of said normalizing amplifier to vary the scale factor to maintain said direct current level component substantially constant.

Claim 3

A receiver as claimed in claim 1 wherein said peak detector circuit operates to respond with a fast rise and a slow decay in recognizing successive input signal peak values and in storing decayed voltage indications of those peak values, the instantaneous value of said decayed voltage indications comprising said control signal level.

Claim 4

A receiver as claimed in claim 1 wherein said variable scale factor circuit comprises a controlled variable attenuator.

Claim 5

A receiver as claimed in claim 3 wherein said attenuator comprises the combination of a photoconductor and a filament lamp device positioned and arranged to illuminate said photoconductor and to vary the conductivity thereof in accordance with said illumination.

Claim 6

A receiver as claimed in claim 3 wherein said scale factor circuit means includes a control amplifier operable to compare the DC level of the output of said normalizing ampLifier with a standard voltage and operable to control said variable attenuator based on the difference voltage determined in said comparison.

Claim 7

A receiver as claimed in claim 1 wherein said means serially connecting said normalizing amplifier to receive signals from said variable scale factor circuit means comprises a low pass filter operable to pass the desired audio signal frequencies.

Claim 8

A receiver as claimed in claim 6 wherein said low pass filter comprises an active Butterworth filter.

Claim 9

A peak detecting and normalizing circuit unit adapted to be added to a radio receiver for improving the operation of the receiver in receiving pulse modulating carrier signals and comprising a peak detector circuit arranged to be connected to receive signals from a radio frequency amplifier of the receiver and operable to detect signal peaks and to set a control signal level determined by the amplitudes of said peaks, said peak detector being arranged to be connected in a control loop to automatically control the gain of at least one radio frequency amplifier of the receiver in accordance with said control signal level to prevent overloading of the receiver to thereby prevent signal distortion and clipping, a normalizing circuit arranged to be connected between a detector stage and an audio stage of the receiver, said normalizing circuit comprising a variable scale factor circuit means connected to receive signals from the receiver detector stage, said normalizing circuit also including a normalizing amplifier arranged to be connected to supply signals to the audio stage, means serially connecting said normalizing amplifier to receive signals from said variable scale factor circuit means, and means connected from the output of said normalizing amplifier to control said variable scale factor circuit means, said scale factor circuit means being operable in response to the direct current level component of the output of said normalizing amplifier to vary the scale factor to maintain said direct current level component substantially constant.

Claim 10

A peak detecting and normalizing circuit unit adapted to be added to a radio receiver for improving the operation of the receiver in receiving pulse modulating carrier signals and comprising a peak detector circuit arranged to be connected to receive signals from a radio frequency amplifier of the receiver and operable to detect signal peaks and to set a control signal level determined by the amplitudes of said peaks, said peak detector being arranged to be connected in a control loop to automatically control the gain of at least one radio frequency amplifier of the receiver in accordance with said control signal level to prevent overloading of the receiver to thereby prevent signal distortion and clipping, a normalizing circuit arranged to be connected between a detector stage and an audio stage of the receiver, said normalizing circuit comprising a variable scale factor circuit means connected to receive signals from the receiver detector stage, said normalizing circuit also including a normalizing amplifier arranged to be connected to supply signals to the audio stage, means serially connecting said normalizing amplifier to receive signals from said variable scale factor circuit means, and means connected from the output of said normalizing amplifier to control said variable scale factor circuit means, said scale factor circuit means being operable in response to the direct current level component of the output of said normalizing amplifier to vary the scale factor to maintain said direct current level component substantially constant.

Claim 11

A unit as claimed in claim 8 wherein switching means are provided for connecting said peak detector circuit to control the gain of the radio frequency amplifier and for connecting the normalizing amplifier to the audio stage of the receiver, said switching means being operable alternatively to disconnect said peak detector circuit and said normalizing amplifier and to establish connections directly from the receiver detector stage to the audio amplifier and to an automatic gain control circuit of the receiver.

Claim 12

Circuits as claimed in claim 9 wherein said circuits are especially adapted for use with an ILS radio receiver, and wherein there is provided a microwave receiver system connected and arranged to receive microwave pulse modulated ILS signals and operable to translate the microwave frequency signals to the normal ILS frequencies, and switching means operable to switch the translated microwave signals into the first radio frequency amplifier of the receiver.

Claim 13

An improved radio receiver for receiving pulse modulated carrier signals comprising a peak detector circuit connected to operate exclusively in response to carrier signal peaks to automatically limit the gain of at least one radio frequency amplifier of said receiver to prevent overloading and distortion thereof despite a high ratio of peak carrier amplitude to average carrier amplitude, a normalizing circuit connected to derive from the carrier signal a direct current voltage level corresponding to the carrier signal level together with the audio output voltages, said normalizing circuit being operable to control the gain of the receiver so as to maintain said direct current voltage level substantially constant.

Claim 14

An improved radio receiver for receiving pulse modulated carrier signals comprising a peak detector circuit connected to operate exclusively in response to carrier signal peaks to automatically limit the gain of at least one radio frequency amplifier of said receiver to prevent overloading and distortion thereof despite a high ratio of peak carrier amplitude to average carrier amplitude, a normalizing circuit connected to derive from the carrier signal a direct current voltage level corresponding to the carrier signal level together with the audio output voltages, said normalizing circuit being operable to control the gain of the receiver so as to maintain said direct current voltage level substantially constant.