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US 6,587,729 B2Granted
Apparatus for audibly communicating speech using the radio frequency hearing effect
AssigneeThe United States of America as represented by the Secretary of the Air Force
InventorsJames P. O'Loughlin, Diana L. Loree
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Abstract
A modulation process with a fully suppressed carrier and input preprocessor filtering to produce an encoded output; for amplitude modulation (AM) and audio speech preprocessor filtering, intelligible subjective sound is produced when the encoded signal is demodulated using the RF Hearing Effect. Suitable forms of carrier suppressed modulation include single sideband (SSB) and carrier suppressed amplitude modulation (CSAM), with both sidebands present.
Claims11
An apparatus for communicating an audio signal a(t), comprising:
- an audio predistortion filter having a filter function As(f) for producing a first output signal a(t)As(t) from the audio signal a(t);
- means for adding a bias A to the first output signal, to produce a second output signal a(t)As(f)+A;
- a square root processor for producing a third output signal (a(t)As(f)+A)½ responsive to the second output signal;
- and
- a modulator for producing a double sideband output signal responsive to the third output signal, having a carrier frequency of ωc, and being mathematically described by (a(t)As(f)+A)½ sin(ωct);
- and
- transmitting the double sideband output signal to a demodulator, whereby the audio signal a(t) is recovered from the double sideband output signal.
4 more elements
Dependencies are inferred from the claim text.