Compatible single sideband system for AM stereo

Claim 2

A transmitter for providing a compatible AM stereo signal of the form [1+(L+R)∠φ] cos (ω c t+D) where D is [(L-R)∠θ]/{1+[(L+R)/2]∠φ, where φ and θ differ by 90° and L and R are distinct program signals, the transmitter comprising in combination: first adder means for combining additively the L and R program signals; second adder means for combining subtractively the L and R program signals; phase shifter means coupled to shift the phase of at least one of the first and second adder means output signals to provide a 90° phase difference between said output signals; third adder means for adding a DC component to the phase-shifted output of the first adder means; divider means coupled to divide the phase-shifted output signal from the second adder means by the output signal of the third adder means; a source of carrier frequency signals; phase modulating means for modulating the carrier frequency signal with the divider output signal; and amplitude modulating means for modulating the carrier frequency signal with the phase-shifted output signal from the first adder means.

Claim 3

A transmitter in accordance with claim 1 wherein φ is -π/4 radians (-45°) and θ is π/4 radians (45°) and the phase shifter means shifts the phase of the output signal of the first adder means by -π/4 radians (-45°) and shifts the phase of the output signal of the second adder means by π/4 radians (45°).

Claim 4

A receiver for receiving a compatible AM stereo signal of the form [1+(L+R)∠φ] cos (ω c t+D) where D is [(L-R)∠θ]/{1+[(L+R)/2]∠φ} where φ and θ differ by 90° and L and R are distinct program signals, the receiver comprising in combination: input means for receiving said signal; first detector means for providing a signal proportional in amplitude to the amplitude modulation on the received signal; second detector means for providing a signal proportional in amplitude to the phase modulation on the received signal; filter means coupled to the first detector means for reducing the amplitude of the audio portion of the output signal thereof to substantially one-half with respect to a band of frequencies lower than audio frequencies and including DC; multiplier means coupled to multiply the output signals of the filter means and the second detector means; first phase shifter means for restoring the original phase of the L+R signal; second phase shifter means for restoring the original phase of the L-R signal; and matrixing means coupled to the outputs of the first and second phase shifter means for providing separate L and R output signals.

Claim 5

A receiver for receiving a compatible AM stereo signal of the form [1+(L+R)∠φ] cos (ω c t+D) where D is [(L-R)∠θ]/{1+[(L+R)/2]∠φ} where φ and θ differ by 90° and L and R are distinct program signals, the receiver comprising in combination: input means for receiving said signal; first detector means for providing a signal proportional in amplitude to the amplitude modulation on the received signal; second detector means for providing a signal proportional in amplitude to the phase modulation on the received signal; filter means coupled to the first detector means for reducing the amplitude of the audio portion of the output signal thereof to substantially one-half with respect to a band of frequencies lower than audio frequencies and including DC; multiplier means coupled to multiply the output signals of the filter means and the second detector means; first phase shifter means for restoring the original phase of the L+R signal; second phase shifter means for restoring the original phase of the L-R signal; and matrixing means coupled to the outputs of the first and second phase shifter means for providing separate L and R output signals.

Claim 6

A receiver in accordance with claim 3 wherein φ is -π/4 radians (-45°) and θ is π/4 radians (45°) and wherein the first phase shifter is a 45° phase shifter and the second phase shifter is a -45° phase shifter.

Claim 7

A receiver for receiving a compatible AM stereo signal of the form [1+(L+R)∠φ] cos (ω c t+D) where D is [(L-R)∠θ]/{1+[(L+R)/2]∠φ} where φ and θ differ by 90° and L and R are distinct program signals, the receiver comprising in combination: input means for receiving said signal; first detector means for providing a signal proportional in amplitude to the amplitude modulation on the received signal at the angle φ; second detector means for providing a signal substantially proportional in amplitude to (L-R)∠θ; first phase shifter means for shifting the phase of the output signal from the first detector means by -φ; second phase shifter means for shifting the phase of the output signal from the second detector means by -θ; and matrixing means coupled to the outputs of the first and second phase shifter means for providing signals substantially proportional to L and R.

Claim 8

A receiver for receiving a compatible AM stereo signal of the form [1+(L+R)∠φ] cos (ω c t+D) where D is [(L-R)∠θ]/{1+[(L+R)/2]∠φ} where φ and θ differ by 90° and L and R are distinct program signals, the receiver comprising in combination: input means for receiving said signal; first detector means for providing a signal proportional in amplitude to the amplitude modulation on the received signal at the angle φ; second detector means for providing a signal substantially proportional in amplitude to (L-R)∠θ; first phase shifter means for shifting the phase of the output signal from the first detector means by -φ; second phase shifter means for shifting the phase of the output signal from the second detector means by -θ; and matrixing means coupled to the outputs of the first and second phase shifter means for providing signals substantially proportional to L and R.

Claim 9

A receiver in accordance with claim 5 wherein φ is -45° and θ is 45°.

Claim 10

A transmitter for transmitting a compatible single sideband signal of the form [1+M∠φ] cos (ω c t+D') where M is a program signal, where D' is (M∠θ)/[1+(M/2)∠φ], and where φ and θ have 90° phase difference therebetween, the transmitter comprising in combination: a program signal source; first phase shifter means for shifting the phase of the program signal by the angle φ; second phase shifter means for shifting the phase of the program signal by the angle θ; adder means for adding a D.C. component to the output signal of the first phase shifter means; divider means for dividing the output signal of the second phase shifter means by the output signal of the adder means; a high frequency signal source for providing a carrier signal; phase modulator means for phase modulating the carrier signal with the output signal of the divider means; and high level modulator means for amplitude modulating the output signal of the phase modulator means by the output signal of the first phase shifter means.

Claim 11

A transmitter for transmitting a compatible single sideband signal of the form [1+M∠φ] cos (ω c t+D') where M is a program signal, where D' is (M∠θ)/[1+(M/2)∠φ], and where φ and θ have 90° phase difference therebetween, the transmitter comprising in combination: a program signal source; first phase shifter means for shifting the phase of the program signal by the angle φ; second phase shifter means for shifting the phase of the program signal by the angle θ; adder means for adding a D.C. component to the output signal of the first phase shifter means; divider means for dividing the output signal of the second phase shifter means by the output signal of the adder means; a high frequency signal source for providing a carrier signal; phase modulator means for phase modulating the carrier signal with the output signal of the divider means; and high level modulator means for amplitude modulating the output signal of the phase modulator means by the output signal of the first phase shifter means.

Claim 12

A transmitter in accordance with claim 7 wherein φ is -π/4 radians (-45°) and θ is π/4 radians (45°).