Spread spectrum communication device and communication system

Details Spread spectrum communication device and communication system Spread spectrum communication device and communication system

2000-04-26

2004-02-24

Fan, Chieh M. (Department: 2634)

Pulse or digital communications

Spread spectrum

Direct sequence

C375S151000

Reexamination Certificate

active

06697418

ABSTRACT:

TECHNICAL FIELD
The present invention relates to surface acoustic wave devices and communication devices.
BACKGROUND ART
In conventional spread spectrum communication devices using the direct spreading method, a Barker code was used as a pseudo noise code as described in 1985 ULTRASONICS SYMPOSIUM proceedings, pp. 145-148, for example. It is known that this code does not depend on the arrangement of an information code sequence and this code has an auto-correlation side lobe of 1.
The Barker code has been found with the code length of 13 or less. The Barker code has not been found with a code length exceeding it. In the case where a processing gain of a code length of at least 14 was required, therefore, a code other than the Barker code, such as the longest code sequence was used. In these code sequences, however, a large side lobe rise is caused when the sign of the information code is inverted. In general, therefore, the error rate is increased.
An object of the present invention is to solve the above described problem and provide a novel structure of a spread spectrum communication device which uses a code sequence having a code length of at least
14
, which does not depend on the arrangement of the information code, and which suppresses the side lobe rise of correlation signals.
SUMMARY OF INVENTION
The above described object can be achieved by employing a code sequence used by the present invention, i.e., a code shown in TABLES 1 through 9 as the pseudo noise code for spreading the power density spectrum of an input signal.
It has been confirmed by calculation conducted by the present inventors that the code shown in TABLES 1 through 9 has an auto-correlation coefficient side lobe of 3 or less. If this code is used, therefore, there is obtained a novel spread spectrum communication device and communication system which has a processing gain having an auto-correlation coefficient side lobe of at least 14, which does not depend on the arrangement of the information code, which suppresses the side lobe rise of the correlation signal, and which makes the error rate small. In addition, a surface acoustic wave device utilizing this characteristic is obtained.
The present invention relates to a novel code having a processing gain with a code length of at least 14 and an auto-correlation side lobe of 3 or less. The code length is determined in some cases by using harmonics of the crystal (oscillation frequency in the case where a frequency multiplier is used). In other cases, the code length is generated independently of the clock frequency of the baseband digital circuit.
It is now assumed that the code length is determined by using harmonics of the crystal. If harmonics are generated by distorting the oscillation waveform of the clock frequency in order to make harmonic components large, for example, only odd-number components included in harmonic components are typically generated. If its odd-number components are used as the clock of pseudo noise code generator, therefore, a value obtained by dividing the clock of the pseudo noise code generator by the clock frequency of the baseband digital circuit, i.e., the code length is obtained. To be concrete, an odd-numbered code length such as 15, 17, 19, . . . is obtained.
In the case where the obtained odd-numbered code length is applied to a spread spectrum communication device, two code lengths are combined and used in some cases. To be concrete, it is a result of multiplication of odd-numbered code lengths. A value of at least 14 such as 15, 21, 25, 27, . . . is used as the code length.
In the case where the code length is generated independently of the clock frequency of the baseband digital circuit, it doesn't matter at all whether the code length is even-numbered or odd-numbered and consequently values of at least 14, i.e., values 14, 15, 16, 17, . . . are obtained.
In either case, a pseudo noise code formed by a large number of combinations in respective code lengths is present. Out of them, the present inventors found a novel code which is 3 or less in auto-correlation side lobe and which is effective as the pseudo noise code used for spreading the power density spectrum of an input signal. The present inventors also found a novel pseudo noise generator capable of executing spreading (or de-spreading) of the power density spectrum of an input signal by using those codes.
The following TABLES 1 through 9 show the pseudo noise code concerning the present invention.
TABLE 1
(n = 14)
max. corr.
max. corr.
number
bj
(forward)
(back)
dc level
202
00000011001010
2
6
−6
332
00000101001100
2
6
−6
404
00000110010100
2
8
−6
405
00000110010101
2
6
−4
410
00000110011010
2
10
−4
470
00000111010110
2
10
−2
665
00001010011001
2
10
−4
691
00001010110011
2
10
−2
811
00001100101011
2
10
−2
821
00001100110101
2
10
−2
1883
00011101011011
2
10
2
2375
00100101000111
2
10
−2
2656
00101001100000
2
8
−6
2767
00101011001111
2
10
2
3232
00110010100000
2
6
−6
3247
00110010101111
2
10
2
3322
00110011111010
2
10
2
4021
00111110110101
2
10
4
4622
01001000001110
2
10
−4
5145
01010000011001
2
6
−4
5251
01010010000011
2
10
−4
5312
01010011000000
2
6
−6
5313
01010011000001
2
8
−4
5327
01010011001111
2
10
2
5535
01010110011111
2
6
4
5728
01011001100000
2
10
−4
5758
01011001111110
2
10
4
6092
01011111001100
2
10
2
6118
01011111100110
2
10
4
6575
01100110101111
2
10
4
6645
01100111110101
2
6
4
6650
01100111111010
2
10
4
6880
01101011100000
2
10
−2
7186
01110000010010
2
10
−4
7989
01111100110101
2
8
4
8090
01111110011010
2
10
4
8293
10000001100101
2
10
−4
8394
10000011001010
2
8
−4
9197
10001111101101
2
10
4
9503
10010100011111
2
10
2
9733
10011000000101
2
10
−4
9738
10011000001010
2
6
−4
9808
10011001010000
2
10
−4
10265
10100000011001
2
10
−4
10291
10100000110011
2
10
−2
10625
10100110000001
2
10
−4
10655
10100110011111
2
10
4
10848
10101001100000
2
6
−4
11056
10101100110000
2
10
−2
11070
10101100111110
2
8
4
11071
10101100111111
2
6
6
11132
10101101111100
2
10
4
11238
10101111100110
2
6
4
11761
10110111110001
2
10
4
12362
11000001001010
2
10
−4
13061
11001100000101
2
10
−2
13136
11001101010000
2
10
−2
13151
11001101011111
2
6
6
13616
11010100110000
2
10
−2
13727
11010110011111
2
8
6
14008
11011010111000
2
10
2
14500
11100010100100
2
10
−2
15562
11110011001010
2
10
2
15572
11110011010100
2
10
2
15692
11110101001100
2
10
2
15718
11110101100110
2
10
4
15913
11111000101001
2
10
2
15973
11111001100101
2
10
4
15978
11111001101010
2
6
4
15979
11111001101011
2
8
6
16051
11111010110011
2
6
6
16181
11111100110101
2
6
6
TABLE 2
(n = 15)
max. corr.
max. corr.
number
bj
(forward)
(back)
dc level
202
000000011001010
3
7
−7
332
000000101001100
3
7
−7
345
000000101011001
3
7
−5
394
000000110001010
3
7
−7
404
000000110010100
3
9
−7
405
000000110010101
3
7
−5
410
000000110011010
3
11
−5
618
000001001101010
3
7
−5
652
000001010001100
3
11
−7
664
000001010011000
3
11
−7
665
000001010011001
3
11
−5
678
000001010100110
3
7
−5
691
000001010110011
3
7
−3
710
000001011000110
3
11
−5
718
000001011001110
3
7
−3
808
000001100101000
3
11
−7
809
000001100101001
3
11
−5
810
000001100101010
3
7
−5
811
000001100101011
3
9
−3
821
000001100110101
3
7
−3
922
000001110011010
3
11
−3
1140
000010001110100
3
11
−5
1221
000010011000101
3
11
−5
1299
000010100010011
3
11
−5
1305
000010100011001
3
11
−5
1356
000010101001100
3
11
−5
1380
000010101100100
3
11
−5
1610
000011001001010
3
11
−5
1620
000011001010100
3
11
−5
1642
000011001101010
3
11
−3
1672
000011010001000
3
11
−7
2152
000100001101000
3
11
−7
2224
000100010110000
3
11
−7
2228
000100010110100
3
11
−5
2281
000100011101001
3
11
−3
2579
000101000010011
3
11
−5
2587
000101000011011
3
11
−3
2656
00

Affiliated with

Also associated with

Rating

Spread spectrum communication device and communication system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Spread spectrum communication device and communication system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spread spectrum communication device and communication system will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3348225