Method and apparatus for converting RF signals to baseband
First Claim
1. A method of converting a radio frequency signal to a baseband signal, said radio frequency signal comprising a plurality of impulses, comprising the steps of:
- a. changing each of said plurality of impulses into rectified pulses by mixing with said radio frequency signal a detect signal, said detect signal comprising precisely timed detecting transitions, such that said detecting transitions occur substantially coincident with a zero-crossing of each of said impulses; and
b. obtaining a baseband signal by integrating one or more rectified pulses.
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Abstract
The present invention relates to the conversion of signals from RF to baseband using transition functions, or edge functions. These functions typically transition from positive to negative, or from negative to positive, synchronously with the transition of the received pulse signal, effecting detection essentially by synchronously rectifying a signal cycle of the received pulse, producing a net signal at baseband that can be further processed to detect modulation according to the modulation format. It is further disclosed how to configure these systems for optimal reception with a filter optimized for a given detect signal function. Generalizations of the matched filter embodiment lead to further embodiments employing alternative detection functions. Also disclosed is a two-stage version which applies a decode signal to the rectified signal. This step can be performed by a single correlator or by a plurality of correlators in parallel. Coding methods are disclosed to employ two-stage systems for enhanced channelization, and interference rejection.
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Citations
18 Claims
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1. A method of converting a radio frequency signal to a baseband signal, said radio frequency signal comprising a plurality of impulses, comprising the steps of:
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a. changing each of said plurality of impulses into rectified pulses by mixing with said radio frequency signal a detect signal, said detect signal comprising precisely timed detecting transitions, such that said detecting transitions occur substantially coincident with a zero-crossing of each of said impulses; and
b. obtaining a baseband signal by integrating one or more rectified pulses. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for converting a radio frequency signal to a baseband signal, said radio frequency signal comprising a plurality of impulses, comprising:
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a. an antenna;
b. a detect signal generator, an output of said detect signal generator being a detect signal comprised of a plurality of transitions, said detect signal generator comprising;
i. a code source;
ii. a timing generator coupled to said code source; and
iii. a transition signal generator responsive to said timing generator;
c. a first multiplier responsive to said antenna and to said detect signal generator, said first multiplier having a rectified output; and
d. a means for integrating said rectified output responsive to said first multiplier. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification