Pulse or digital communications – Repeaters – Testing
Reexamination Certificate
1998-09-29
2001-10-09
Chin, Stephen (Department: 2734)
Pulse or digital communications
Repeaters
Testing
C375S150000, C375S152000
Reexamination Certificate
active
06301294
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a spread spectrum communication device, and particularly relates to a spread spectrum communication device which demodulates a received analog spread spectrum signal by the direct spectrum spreading scheme by performing both the analog signal processing operations and the digital signal processing operations.
BACKGROUND OF THE INVENTION
Conventionally, there has been proposed a spread spectrum communication device which demodulates a received analog spread spectrum signal by the direct spectrum spreading scheme by performing both the analog signal processing operations and the digital signal processing operations.
Regarding such a spread spectrum communication device, for example, the Japanese Publication for Laid-Open Patent Application No. 115387/1995 (Tokukaihei 7-115387) discloses the following technique. An A/D converter for receiving an analog spread spectrum signal and converting the received analog signal to a digital signal is provided at the first stage of a base band processing unit so that digital signal processing operations are performed at the stages there behind in the base band processing unit.
Further, regarding a spread spectrum communication device, the Japanese Publication for Laid-Open Patent Application No. 83486/1997 (Tokukaihei 9-83486) discloses the following technique. An integrating unit for conducting an integrating operation with respect to an analog input signal with weights given thereto according to a PN code and outputting an integrated result as an analog output signal is provided. By doing so, the analog output signal is intermittently held, and peaks of the analog signal thus held are detected so that timings of the detected peaks are determined, and only at these timings thus determined, peak values of the inputted analog signal are digitized by an A/D converter.
With the technique disclosed by Tokukaihei 9-83486, an operational speed of the A/D converter can be suppressed to minimum, thereby resulting in that power consumption can be reduced.
However, with the technique disclosed by Tokukaihei 7-115387, since a sampling operation has to be carried out many times at a high speed for synchronization acquisition, there has arisen a drawback in that a circuit size thereof is large and power consumption thereof is great.
Besides, with the technique disclosed by Tokukaihei 9-83486, power consumption of the base band processing unit can be suppressed by lowering the operational speed of the A/D converter, but this makes the circuit for detecting peaks of an analog signal complicated. Thus, values obtained by peak detection with respect to the analog output signal are subject to A/D conversion, and therefore, there is a drawback in that precision in peak value detection is poor in spite of complicated peak detection. Therefore, there has arisen a problem that an analog spread spectrum signal is hardly demodulated with high precision.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a spread spectrum communication device characterized in that a circuit size of a base band processing unit thereof is small and power consumption of the base band processing unit is suppressed, and that precision in reception of a received signal is improved.
To achieve the aforementioned object, a spread spectrum communication device of the present invention has a base band processing unit which includes a synchronization acquiring section for acquiring synchronization from a received analog spread spectrum signal, and a data demodulating section for demodulating the received analog spread spectrum signal based on the result of the operation of the synchronization acquiring section. The synchronization acquiring section has at least a matched filter for detecting peak positions of the received analog spread spectrum signal, and the matched filter performs an analog processing operation.
Generally, in the case where all the operations in the base band processing unit are digital processing operations, most of power consumed therein is consumed by the matched filter. Therefore, by causing the matched filter to perform its processing operation in analog, power consumption in the base band processing unit can be drastically reduced.
Therefore, with the aforementioned arrangement wherein at least the processing operation by the matched filter is an analog processing operation, power consumption in the base band processing unit can be drastically decreased.
Besides, in the case where the matched filter is designed so as to carry out an analog processing operation, the circuit size thereof can be made smaller as compared with the circuit size in the case where the processing operation of the matched filter is a digital processing operation.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5465396 (1995-11-01), Hunsinger et al.
patent: 5467367 (1995-11-01), Izumi et al.
patent: 5703503 (1997-12-01), Miyamoto et al.
patent: 07115387A (1995-05-01), None
patent: 09083486A (1997-03-01), None
patent: 10-145326 (1998-05-01), None
Jari Iinatti, Pentti Leppanen, Use of a Matched Filter for Synchronization of a DS Receiver in AWGN Channel and Continuous Tone Jamming, 1991 IEEE pp. 716-719.
Hara Keita
Iizuka Kunihiko
Al-Beshrawi Tony
Chin Stephen
Sharp Kabushiki Kaisha
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