Radio receiver with wide dynamic range

Claim 2

A radio receiving system having low threshold sensitivity and wide dynamic range comprising, in combination, first and second signal processing channels each including at least an amplifier stage adapted to automatic gain control, said first channel having a lower threshold sensitivity than said second channel and a dynamic range to provide linear gain for signals of a magnitude up to approximately the threshold sensitivity of said second channel, said second channel having an independent dynamic range to provide linear gain for signals over a range of magnitudes in excess of the threshold sensitivity of said second channel, means connecting the input of each of said channels to a common source of modulated signAls, a circuit connected to the output of each channel for combining the signals processed thereby, a demodulator connected to said combining circuit, and an automatic gain control circuit connected to the output of said demodulator arranged to apply separate automatic gain control signals to the amplifier in respective ones of said channels, said last-mentioned circuit being operative in response to input signals of amplitudes within the dynamic range of said first channel to apply a bias signal to the amplifier in said first channel, and operative in response to input signals of amplitude exceeding the threshold sensitivity of said second channel to apply to the amplifier in said first channel a bias signal of a magnitude to reduce the gain of said first channel to substantially zero and to apply to the amplifier in said second channel a bias signal of a magnitude proportional to the amplitude of the input signal throughout the dynamic range of said second channel, whereby an input signal of magnitude in excess of the dynamic range of said first channel is processed exclusively by said second channel.

Claim 3

A radio receiving system having low threshold sensitivity and wide dynamic range comprising, in combination, first and second signal processing channels each including at least an amplifier stage adapted to automatic gain control, said first channel having a lower threshold sensitivity than said second channel and a dynamic range to provide linear gain for signals of a magnitude up to approximately the threshold sensitivity of said second channel, said second channel having an independent dynamic range to provide linear gain for signals over a range of magnitudes in excess of the threshold sensitivity of said second channel, means connecting the input of each of said channels to a common source of modulated signAls, a circuit connected to the output of each channel for combining the signals processed thereby, a demodulator connected to said combining circuit, and an automatic gain control circuit connected to the output of said demodulator arranged to apply separate automatic gain control signals to the amplifier in respective ones of said channels, said lastmentioned circuit being operative in response to input signals of amplitudes within the dynamic range of said first channel to apply a bias signal to the amplifier in said first channel, and operative in response to input signals of amplitude exceeding the threshold sensitivity of said second channel to apply to the amplifier in said first channel a bias signal of a magnitude to reduce the gain of said first channel to substantially zero and to apply to the amplifier in said second channel a bias signal of a magnitude proportional to the amplitude of the input signal throughout the dynamic range of said second channel, whereby an input signal of magnitude in excess of the dynamic range of said first channel is processed exclusively by said second channel.

Claim 4

A radio receiving system having low threshold sensitivity and wide dynamic range comprising, in combination, first and second signal processing channels each including at least an amplifier stage adapted to automatic gain control, said first channel having a lower threshold sensitivity than said second channel and a dynamic range to provide linear gain for signals of a magnitude up to approximately the threshold sensitivity of said second channel, said second channel having an independent dynamic range to provide linear gain for signals over a range of magnitudes in excess of the threshold sensitivity of said second channel, means connecting the input of each of said channels to a common source of modulated signAls, a circuit connected to the output of each channel for combining the signals processed thereby, a demodulator connected to said combining circuit, and an automatic gain control circuit connected to the output of said demodulator arranged to apply separate automatic gain control signals to the amplifier in respective ones of said channels, said lastmentioned circuit being operative in response to input signals of amplitudes within the dynamic range of said first channel to apply a bias signal to the amplifier in said first channel, and operative in response to input signals of amplitude exceeding the threshold sensitivity of said second channel to apply to the amplifier in said first channel a bias signal of a magnitude to reduce the gain of said first channel to substantially zero and to apply to the amplifier in said second channel a bias signal of a magnitude proportional to the amplitude of the input signal throughout the dynamic range of said second channel, whereby an input signal of magnitude in excess of the dynamic range of said first channel is processed exclusively by said second channel.

Claim 5

A radio frequency signal receiving system comprising, in combination, first and second signal processing channels each including at least a detector and a video amplifier stage adapted to automatic gain control, said first channel having a lower threshold sensitivity than said second channel and a dynamic range to provide linear gain for signals of a magnitude up to approximately the threshold sensitivity of said second channel, said second channel having an independent dynamic range to provide substantially linear gain for signals of a magnitude in excess of the threshold sensitivity of said second channel, means connecting the input of each of said channels to a common source of modulated signals, a circuit connected to the output of said channels for combining the signals processed thereby, a demodulator connected to said combining circuit, and an automatic gain control circuit connected to the output of said demodulator and arranged to apply separate automatic gain control signals to the video amplifier in said respective channels in accordance with the amplitude of an input signal, said automatic gain control circuit being operative in response to a signal from said demodulator having an amplitude proportional to an input signal level within the dynamic range of said first channel to apply a gain control voltage to the amplifier in said first channel only, and operative in response to input signals exceeding the threshold sensitivity of said second channel to apply to said first channel a gain control voltage of a magnitude to reduce the gain of said first channel to substantially zero and to apply to the amplifier in said second channel a gain control voltage of magnitude proportional to the amplitude of the input signals, thereby automatically providing a smooth cross-over from one channel to the other as the amplitude of the input signal varies between the dynamic ranges of the channels and extending the effective dynamic range of said system to the sum of the dynamic ranges of said first and second channels.

Claim 6

A radio frequency signal receiving system comprising, in combination, first and second signal processing channels each including at least a detector and a video amplifier stage adapted to automatic gain control, said first channel having a lower threshold sensitivity than said second channel and a dynamic range to provide linear gain for signals of a magnitude up to approximately the threshold sensitivity of said second channel, said second channel having an independent dynamic range to provide substantially linear gain for signals of a magnitude in excess of the threshold sensitivity of said second channel, means connecting the input of each of said channels to a common source of modulated signals, a circuit connected to the output of said channels for combining the signals processed thereby, a demodulator connected to said combining circuit, and an automatic gain control circuit connected to the output of said demodulator and arranged to apply separate automatic gain control signals to the video amplifier in said respective channels in accordance with the amplitude of an input signal, said automatic gain control circuit being operative in response to a signal from said demodulator having an amplitude proportional to an input signal level within the dynamic range of said first channel to apply a gain control voltage to the amplifier in said first channel only, and operative in response to input signals exceeding the threshold sensitivity of said second channel to apply to said first channel a gain control voltage of a magnitude to reduce the gain of said first channel to substantially zero and to apply to the amplifier in said second channel a gain control voltage of magnitude proportional to the amplitude of the input signals, thereby automatically providing a smooth cross-over from one channel to the other as the amplitude of the input signal varies between the dynamic ranges of the channels and extending the effective dynamic range of said system to the sum of the dynamic ranges of said first and second channels.

Claim 7

A radio frequency signal receiving system comprising, in combination, first and second signal processing channels each including at least a detector and a video amplifier stage adapted to automatic gain control, said first channel having a lower threshold sensitivity than said second channel and a dynamic range to provide linear gain for signals of a magnitude up to approximately the threshold sensitivity of said second channel, said second channel having a dynamic range to provide linear gain for signals of a magnitude in excess of its threshold level, means for applying an input signal in parallel to the inputs of said first and second channels, a circuit connected to the output of said channels for combining the signals processed thereby, a demodulator connected to said combining circuit, and an automatic gain control circuit connected to the outpUt of said demodulator and arranged automatically to select in accordance with the magnitude of said input signal the channel in which the input signal is processed, said automatic gain control circuit being operative in response to an input signal level within the dynamic range of said first channel to apply a gain control voltage only to the video amplifier in said first channel, and operative in response to an input signal level exceeding the threshold sensitivity of said second channel to apply to said first channel a gain control voltage of a magnitude sufficient to reduce the gain of said first channel to substantially zero and to apply to said second channel a gain control voltage of a magnitude proportional to the amplitude of the input signal, thereby to provide a smooth cross-over from said first channel to the second channel as the magnitude of the input signal varies from a value within the dynamic range of said first channel to a value which exceeds the threshold sensitivity of said second channel and to extend the dynamic range of the receiving system to the sum of the dynamic ranges of said first and second channels.

Claim 8

A radio frequency signal receiving system comprising, in combination, first and second signal processing channels each including at least a detector and a video amplifier stage adapted to automatic gain control, said first channel having a lower threshold sensitivity than said second channel and a dynamic range to provide linear gain for signals of a magnitude up to approximately the threshold sensitivity of said second channel, said second channel having a dynamic range to provide linear gain for signals of a magnitude in excess of its threshold level, means for applying an input signal in parallel to the inputs of said first and second channels, a circuit connected to the output of said channels for combining the signals processed thereby, a demodulator connected to said combining circuit, and an automatic gain control circuit connected to the outpUt of said demodulator and arranged automatically to select in accordance with the magnitude of said input signal the channel in which the input signal is processed, said automatic gain control circuit being operative in response to an input signal level within the dynamic range of said first channel to apply a gain control voltage only to the video amplifier in said first channel, and operative in response to an input signal level exceeding the threshold sensitivity of said second channel to apply to said first channel a gain control voltage of a magnitude sufficient to reduce the gain of said first channel to substantially zero and to apply to said second channel a gain control voltage of a magnitude proportional to the amplitude of the input signal, thereby to provide a smooth cross-over from said first channel to the second channel as the magnitude of the input signal varies from a value within the dynamic range of said first channel to a value which exceeds the threshold sensitivity of said second channel and to extend the dynamic range of the receiving system to the sum of the dynamic ranges of said first and second channels.