Apparatus for receiving and processing frequency modulated electromagnetic signals

In a system for generating stereophonically related, first and second audio signals from a broadcast, frequency modulated, radio frequency signal:

• signal processing means for receiving first and second audio signals generated from said frequency modulated signal and for at least partially blending said audio signals into a monophonic audio signal, means providing a continuously variable analog control signal for controlling the aforesaid blending of said first and second audio signals, means providing an enabling control signal, and means automatically operable absent the receipt of a signal from the enabling control signal source when the frequency modulated signal does not include multipath distortions which exceed a threshold value or if the strength of the frequency modulated signal rises to a level above a threshold value for defeating the signal blending operation of said signal processing means, whereby said signal processing means generates only stereophonically related audio signals if said frequency modulated signal does not include multipath distortions which exceed said selected value and the strength of the frequency modulated signal is above the threshold value thereof.

In a system for generating stereophonically related, first and second audio signals from a frequency modulated, radio frequency signal:

• signal processing means for receiving first and second audio signals generated from said frequency modulated signal and for at least partially blending said audio signals into a monophonic audio signal if the frequency modulated signal includes multipath distortions which exceed a threshold value or if the strength of the frequency modulated signal falls to a level below said threshold value, said system also including means which is manually operable to defeat the audio signal blending operation of said signal processing means, whereby the output from said system consists entirely of the stereophonically related first and second audio signals irrespective of the quality of the signal received by said signal processing means, and means responsive to an incoming signal which contains stereo information and is not broadcast, frequency modulated signal for actuating the means for defeating the stereo signal blending operation of the signal processing means.

In a system for receiving a broadcast frequency modulated radio frequency signal and for generating first and second, stereophonically related audio signals from said broadcast, frequency modulated signal:

• means including a pair of complementary operational amplifiers for generating positive going and negative going control signals in response to a decrease in the level of said broadcast signal to a level below a threshold value and signal processing means receiving said first and second audio signals and automatically responsive to the application of said positive going and negative going control signals thereto to at least partially blend said stereophonically related audio signals into a monophonic audio signal.

In a system for receiving a frequency modulated radio frequency signal and for generating first and second, stereophonically related audio signals from said frequency modulated signal:

• means for detecting multipath distortions of said frequency modulated signal which exceed a threshold level and for generating an enabling control signal in response to the detection of such multipath distortions of the frequency modulated signal, means for generating a control signal in response to a decrease in the level of the radio frequency signal to a level below a threshold level, and signal processing means receiving said first and second audio signals and responsive to the application of the enabling signal thereto to blend said audio signals into a monophonic audio signal to an extent determined by the strength of said control signal, said system further comprising a circuit which keeps said signal processing means turned on for at least a minimum preselected, multisecond period of time to blend said first and second audio signals into a monophonic audio signal as aforesaid.

In a system for generating stereophonically related, first and second audio signals from a frequency modulated, radio frequency signal:

• signal processing means for receiving first and second audio signals generated from said frequency modulated signal and for at least partially blending said audio signals into an at least partially monophonic audio signal if the frequency modulated signal includes multipath distortions which exceed a threshold value or if the strength of the frequency modulated signal falls to a level below said threshold value, said signal processing means also including circuit elements so related to said signal blending means that those components of the first and second audio signals having frequencies below a selected frequency are blended only to an extent which decreases as the frequencies of those components fall below a selected frequency, whereby said signal processing means can output an audio signal containing a blend of monophonic components of higher frequency and stereophonic components of lower frequency.