Method and apparatus for pilot signal cancellation in an FM multiplex demodulator
AssigneePioneer Electronic Corporation
InventorSeijiro Fujie
Life of this patent
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Abstract
Unwanted pilot signal components in the "L" and "R" outputs of a stereophonic FM multiplex demodulator are cancelled by inverting the 19KHz pilot signal, separately multiplying or gating it with the opposite phase 38KHz subcarrier signals, and adding the multiplier or gate outputs to the "L" and "R" demodulator outputs. The multiplication produces signals equal in amplitude but opposite in phase to the contaminating pilot signal components, whereby the latter are effectively cancelled by the addition function.
Claims3
In an FM multiplex demodulator including means for providing left (L) and right (R) channel output signals from a composite input signal in response to opposite phase switching signals derived from a pilot signal, means for removing unwanted pilot signal components from the L and R output signals, comprising:
- a. means for inverting the pilot signal,
- b. means for individually multiplying the inverted pilot signal by each of the opposite phase switching signals to produce signals equal in amplitude but opposite in phase to the unwanted pilot signal components, and
- c. means for individually adding the multiplication signals to the respective L and R output signals, whereby the unwanted pilot signal components are effectively cancelled.
In an FM multiplex demodulator wherein left (L) and right (R) channel output signals are derived from a composite input signal in response to opposite phase switching signals derived from a pilot signal, a method for removing unwanted pilot signal components from the L and R output signals, comprising the steps of:
- a. inverting the pilot signal,
- b. individually multiplying the inverted pilot signal by each of the opposite phase switching signals to produce signals equal in amplitude but opposite in phase to the unwanted pilot signal components, and
- c. individually adding the multiplication signals to the respective L and R output signals, whereby the unwanted pilot signal components are effectively cancelled.
Dependencies are inferred from the claim text.