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US 3,936,751 AGranted
SWD FM detector and IF filter
AssigneeTexas Instruments Incorporated
InventorsJerry D. Holmes, Benjamin L. Lowe, Samuel D. Moore
Life of this patent
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Abstract
An SWD structure is employed in an FM receiver for signal demodulation and band limiting. An FM signal is applied to the input of an SWD patterned for bandwidth limitation. Two SWD output channels characterized by predetermined differential delays of the modulated input signal are amplitude limited and mixed to produce an audio modulation component.
Claims13
In a radio receiver, the combination comprising:
- a. an SWD structure providing two channels each with an input section and an output section, said channels having different spacing between their input and output sections respectively such that predetermined different delays are imposed on modulated signals passing through said channels,
- b. a mixer,
- c. means to apply a modulated input signal to said input sections of said SWD structure, and
- d. means to receive output signals from each of said output sections and to apply said output signals from said two channels to said mixer to produce at the output of said mixer an audio output signal representing the modulation of said input signal.
1 more element
In an IF section of an FM receiver, the combination comprising:
- a. an SWD having an input section and two output sections defining two separate channels of different lengths and characterized by predetermined different delays of an input signal of the IF frequency passing through said channels,
- b. a mixer,
- c. means to apply an FM signal to said input section, and
- d. means to receive signals from each of said two output sections and apply said signals to said mixer to produce at the output of said mixer an audio output signal representing the modulation of said input signal.
1 more element
The method of demodulating an input signal which comprises:
- a. generating an acoustic wave corresponding to said input signal,
- b. detecting said wave after a delay .DELTA. and producing a first filtered electrical signal corresponding to said wave detected after said delay,
- c. detecting said wave after a delay .DELTA. + T and producing a second filtered electrical signal corresponding to said wave detected after said last delay,
- d. mixing said first and second electrical signals, and
- e. filtering the signal resulting from mixing to pass modulation frequencies.
2 more elements
Dependencies are inferred from the claim text.