[54] SPREAD SPECTRUM PULSE POSITION MODULATION SYSTEM
[75] Inventor: Masaru Nakamura, Yokohama, Japan
[73] Assignee: Ricoh Company, Ltd., Tokyo, Japan
[21] Appl. No.: 08/862,647
[22] Filed: May 23, 1997
[30] Foreign Application Priority Data
May 24, 1996 [JP] Japan 8-151917
[51] Int. CI. H04B 1 69
[52] U.S. CI 375/200; 375/207; 375/208;
375/239; 370/213; 332/112
[58] Field of Search 375/200, 207,
375/208, 239, 343; 370/213; 332/112
[56] References Cited
U.S. PATENT DOCUMENTS
4,206,316 6/1980 Bumsweig et al 375/239
5,157,686 10/1992 Omura et al 375/200
5,216,693 6/1993 Nakamura .
5,303,258 4/1994 Nakamura .
5,438,589 8/1995 Nakamura .
5,469,469 11/1995 Haines 375/201
5,596,601 1/1997 Bar-David 375/207
5,712,871 1/1998 Chang 375/239
FOREIGN PATENT DOCUMENTS
8-79133 3/1996 Japan .
OTHER PUBLICATIONS
"Spread Spectrum Pulse Position Modulation", By Isao Okazaki and Takaaki Hasegawa, IEICE Trans. Commun., vol. E76-B. No. 8 Aug. 1993, pp. 929-940.
Primary Examiner—Temesghen Ghebretinsae
Attorney, Agent, or Firm—Obion, Spivak, McClelland,
Maier & Neustadt, PC.
[57] ABSTRACT
A spread spectrum pulse position modulation/demodulation system which receives an input signal including frames and which includes first and second pulse position modulators. The first pulse position modulator modulates each frame by inserting a first pseudo noise code into a selected slot of each frame according to the input signal to generate a first spread spectrum pulse position modulating signal. The second pulse position modulator modulates each frame by inserting a second pseudo noise code into a selected slot of each frame according to the input signal to generate a second spread spectrum pulse position modulating signal. An adder adds together the first and second spread spectrum pulse position modulating signals to generate a third spread spectrum pulse position modulating signal. This third spread spectrum pulse position modulating signal may be transmitted by a radio transmitter, and then received by a radio receiver. The received third spread spectrum pulse position modulating signal can then be input into a demodulator for demodulating this third spread spectrum pulse position modulating signal. The demodulator includes at least one matched filter to output a first pulse signal corresponding to the first spread spectrum pulse position modulating signal and to output a second pulse signal corresponding to the second spread spectrum pulse position modulating signal.
21 Claims, 16 Drawing Sheets
