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| Weather alert system |
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| Environmental monitoring device |
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Receiver for receiving a spectrum dispersion signal
| Details |
Inventors: Sudo, Shigeyuki; Hasegawa, Osamu; Eguchi, Toshiya;
Assignee: Hitachi, Ltd. (Tokyo, JP)
Primary Examiner: Le; Amanda T.
Assistant Examiner:
Attorney, Agent or Firm: Antonelli, Terry, Stout & Kraus, LLP
A receiver for the CDMA system, in order to reduce a power consumption during a suspension period of intermittent receiving operation, monitors a suspension period t1 by means of a low-power timer 51 so that a VC-TCXO 1, a reference signal group generation unit 2 and a receiving unit 3 are turned off and a modem unit 4 is set to a sleep state. Upon resumption of receiving operation, a high-accuracy timer 44 is supplied with a start (d) to require counting of time t3 and a part of a received signal is stored. A PN code phase of stored data is calculated in a PN code phase calculator 46 during a period t3 to obtain an indication value i for a phase deviation. State vectors for short code and long code and further a reception time t4 are calculated on the basis of the indication value i to be set. When the high-accuracy timer 44 counts t3 and produces 0V(d), demodulation operation by a rake demodulation unit 40, a demultiplexing unit 41 and a descrambler unit 42 is started in accordance with the setting and is continued during the reception time t4. |
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DETAILED DESCRIPTION The subject to be solved by the present invention is to suspend despreading code generating means and a high-accuracy oscillator circuit (for example, VC-TCXO) which is a reference of timer means, both of which cannot be suspended in the prior art during the suspension period of the intermittent receiving operation.
Thus, the average power consumption of the receiver for the terminal used in the mobile communication system of the CDMA system is more reduced.
In order to achieve the above object, a receiver for receiving a spread spectrum signal and including means for generating a code for despreading, comprises first timer means started when a receiving state is changed to a suspension state, second timer means started when receiving operation is resumed from the suspension state and for counting a length of time A, storage means for storing a received signal of a predetermined length in the form of digital data, code phase calculation means for calculating a phase of spreading code relative to the received signal stored in the storage means, state vector calculation means for calculating a state vector of the code generating means corresponding to a code phase after an elapse of time corresponding to the length of time A on the basis of the calculated phase of spreading code, and intermittent receiving control means for controlling to start counting of the second timer means when the storage means starts storage operation and to cause the code generating means to start operation thereof on the basis of the calculated result of the state vector calculation means when the second timer means is overflowed.
Further, the receiver comprises reception time calculation means for calculating a length of reception time B containing a slot period of a paging channel to be received from the time that the second timer means is overflowed and to which a predetermined receiving processing time is added, on the basis of the calculated code phase, and third timer means to which any length of time to be counted can be set
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Communications 
