US PATENT SUBCLASS 375 / 200
SPREAD SPECTRUM

Current as of: June, 1999
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375 /   HD   PULSE OR DIGITAL COMMUNICATIONS

200SPREAD SPECTRUM {7}
201  DF  .~> Hybrid forms
202  DF  .~> Frequency hopping
203  DF  .~> Time hopping
204  DF  .~> Pulsed FM or chirp
206  DF  .~> Direct sequence
207  DF  .~> Matched filter
208  DF  .~> Pseudo-noise correlation {2}

DEFINITION

Classification: 375/200

SPREAD SPECTRUM:

(under the class definition) Subject matter utilizing a data modulated signal which has its energy spread over a transmitted bandwidth which is much greater than the bandwidth or rate of information being sent.

(1) Note. Three general types of modulation are in the spread spectrum variety: (A) Modulation of a carrier by a data modulation signal whose bit rate is much higher than the maximum possible repetition rate of the pulses or discrete steps. Such systems are called "direct sequence" modulated systems; (B) Carrier frequency shifting in discrete increments in a pattern dictated by a code sequence. These are called "frequency hoppers." The transmitter jumps from frequency to frequency within some predetermined set; the order of frequency usage is determined by a code sequence; and (C) Pulse-FM or "chirp" modulation in which a carrier is swept over a wideband during a given pulse interval.

(2) Note. Wideband FM is not classified here but is classified in subclass 88 and Class 455, subclasses 42+.

(3) Note. Closely akin to the frequency hoppers are "time hopping" and "time-frequency hopping" systems whose chief distinguishing feature is that their time of transmission (usually of low duty cycle and short duration) is governed by a code sequence. In time-frequency hoppers it follows that the code sequence determines both the transmitted frequency and the time of transmission.

SEE OR SEARCH THIS CLASS, SUBCLASS:

254, and 285, for noise or distortion reduction which may include patents with subject matter similar to the above.

SEE OR SEARCH CLASS

370, Multiplex Communications, 93, for multiplexing with spread spectrum techniques.