Demodulator for CDMA spread spectrum communication using multiple pn codes

• US 5,812,546 A
• Filed: 02/19/1997
• Issued: 09/22/1998
• Est. Priority Date: 02/19/1996
• Status: Expired due to Fees

• Current Assignee: Hitachi Kokusai Electric Incorporated (Hitachi, Ltd.), YOZAN, Inc.
• Original Assignee: Kokusai Electric Co., Ltd., YOZAN, Inc.
• Inventors: Yamamoto, Makoto, Takatori, Sunao, Urabe, Kenzo, Zhou, Xuping, Shou, Guoliang, Zhou, Changming
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): VANDERPUYE, KENNETH N
• Application Number:
  US08/802,635
• Time in Patent Office: 580 Days
• Field of Search: 375/200, 375/206, 375/207, 375/208, 375/210, 375/343, 370/206, 370/335, 370/342, 327/91, 327/93, 327/95, 327/96, 364/724.11, 329/308
• US Class Current: 370/342
• CPC Class Codes: H04B 1/7093 Matched filter type

Abstract

The demodulator has a plurality of matched filters in parallel. Each matched filter has a different binary PN code, a plurality of sample holders, a plurality of multipliers, an adder, and a controller. The sample holders has a common input, a switch, a first capacitor, a first inverse amplifier with an output and an input connected to the common input through the switch and the capacitor, and a first feedback capacitor for feeding the output of the first inverse amplifier back to the input. Each multiplier has a first and second sub-multiplexers, one of sub-multiplexer selecting corresponding sample holder output and another sub-multiplexer selecting a reference voltage.

Claims

1. A demodulator for a spread spectrum communication having a plurality of matched filters in parallel, each of said matched filters comprising:

a different binary PN code,

a plurality of sample holders having a common input, each including, a switch, a first capacitor, a first inverse amplifier having an output, and an input connected to the common input through the switch and the capacitor, and a first feedback capacitor for feeding the output of the first inverse amplifier back to the input thereof;

a plurality of multipliers, each having a first and second sub-multiplexers, one of sub-multiplexer selecting corresponding sample holder output and another sub-multiplexer selecting a reference voltage;

an adder having a plurality of second capacitors, a second inverse amplifier including an output, and an input connected to each of the first sub-multiplexers through each of the second capacitors, a second feedback capacitor for feeding the output of the second inverse amplifier back to the input thereof, a plurality of third capacitors, a third inverse amplifier having an output, and an input connected to each of the second sub-multiplexers and second inverse amplifier through each of the third capacitors, and a third feedback capacitor for feeding the output of the third inverse amplifier back to the input thereof;

a controller which closes one of the switches of the sample holders while opening the other switches, and switches over the first and second sub-multiplexers with a predetermined combination in response to the binary PN code for a multiplication of the binary PN code.

2. The demodulator according to claim 1 for an M-array type spread spectrum communication, wherein:

each signal corresponds to one of the PN codes; and

when one of the matched filters generates a peak, the signal related to the PN code of the peak generating matched filter is determined to be received.

3. The demodulator according to claim 1, for a parallel type spread spectrum communication, wherein:

each signal corresponds to one of the PN codes;

when a plurality of the matched filters generate peaks, the signals corresponding to the PN codes of the peak generating matched filters are determined to be received; and

outputs of the peak detecting matched filters are used as a set of a received signal.

4. The demodulator according to claim 1, for a parallel combination type spread spectrum communication, wherein:

signal sequences corresponding to a combination of the PN codes are defined in advance; and

when the matched filter generates a peak, the signal sequence corresponding to the combination of the PN codes of the peak detecting matched filters is determined to be received.

5. The demodulator according to claims 2, wherein:

each of the first, second and third inverse amplifiers have odd number of MOS inverters; and

each of the sample holders is used for the plurality of matched filters in common.

6. The demodulator according to claims 3, wherein:

each of the first, second and third inverse amplifiers have odd number of MOS inverters; and

each of the sample holders is used for the plurality of matched filters in common.

7. The demodulator according to claims 4, wherein:

each of the first, second and third inverse amplifiers have odd number of MOS inverters; and

each of the sample holders is used for the plurality of matched filters in common.

8. A demodulator according to claim 1, for a base station which communicates with a plurality of user stations by DS-CDMA spectrum spread communication, wherein each of the PN codes corresponds to each user station, and the matched filters acquire a correlation of a received signal with respective PN code assigned as a tap coefficient, further comprising:

signal extractors, each of which extracts a signal with high level as a dominant signal, from an output of respective matched filter;

respreading circuits, each of which respreads spectrum of the dominant signal obtained by respective dominant signal extractor with the respective user'"'"'s spectrum spreading code;

a delay that delays the received signal by a predetermined period;

first adders, each of which subtracts outputs of the respreading circuits other than a specific user'"'"'s respread signal, from the output of the delay;

second matched filters, each of which despreads the spectrum of an output of the respective first adder, with the spectrum spreading codes assigned to the specific user; and

decision circuits, each of which determines respective user signal from each of the second matched filters.

9. The multi-user demodulator according to claim 8, wherein:

each of the signal extractors extracts the signal with high level by a threshold operation using a product of the maximum output of the respective first matched filter by a predetermined ratio as a threshold.

10. A spread spectrum communication station having a demodulator which comprises a plurality of matched filters in parallel, an antenna which feeds a received signal to the demodulator, and a network switch which switches the signal to and from a network wherein each of said matched filters comprising:

a different binary PN code,

a plurality of sample holders having a common input, each including, a switch, a first capacitor, a first inverse amplifier having an output, and an input connected to the common input through the switch and the capacitor, and a first feedback capacitor for feeding the output of the first inverse amplifier back to the input thereof;

a plurality of multipliers, each having a first and second sub-multiplexers, one of sub-multiplexer selecting corresponding sample holder output and another sub-multiplexer selecting a reference voltage;

an adder having a plurality of second capacitors, a second inverse amplifier including an output, and an input connected to the first sub-multiplexers through the second capacitors, a second feedback capacitor for feeding the output of the second inverse amplifier back to the input thereof, a plurality of third capacitors, a third inverse amplifier having an output, and an input connected to the second sub-multiplexers and second inverse amplifier through the third capacitors, and a third feedback capacitor for feeding the output of the third inverse amplifier back to the input thereof;

a controller which closes one switch of the sample holders while opening the other switches, and switches over the first and second sub-multiplexers with a predetermined combination in response to the PN code of the multiplexer.

11. A spread spectrum communication station according to claim 10 wherein:

the demodulator is for an M-array type spread spectrum communication;

each signal corresponds to one of the PN codes; and

when one of the matched filters generates a peak, the signal related to the PN code of the peak generating matched filter is determined to be received.

12. A spread spectrum communication station according to claim 10 wherein;

the demodulator is for a parallel type spread spectrum communication;

each signal corresponds to one of the PN codes;

when a plurality of the matched filters generate peaks, the signals corresponding to the PN codes of the peak generating matched filters are determined to be received; and

outputs of the peak detecting matched filters are used as a set of a received signal.

13. A spread spectrum communication station according to claim 10, wherein:

the demodulator is for a parallel combination type spread spectrum communication; and

signal sequences corresponding to a combination of the PN codes are defined in advance; and

when the matched filter generates a peak, the signal sequence corresponding to the combination of the PN codes of the peak detecting matched filters is determined to be received.

14. The spread spectrum communication station according to claim 11, wherein:

each of the first, second and third inverse amplifiers have odd number of MOS inverters; and

each of the sample holders is used for the plurality of matched filters in common.

15. The spread spectrum communication station according to claim 12, wherein:

each of the first, second and third inverse amplifiers have odd number of MOS inverters; and

each of the sample holders is used for the plurality of matched filters in common.

16. The spread spectrum communication station according to claim 13, wherein:

each of the first, second and third inverse amplifiers have odd number of MOS inverters; and

each of the sample holders is used for the plurality of matched filters in common.

17. A spread spectrum communication station according to claim 10 which communicates with a plurality of user stations by DS-CDMA communication, wherein each of the PN codes corresponds to each user station, and the matched filters acquires a correlation of a received signal with respective PN code assigned as a tap coefficient, further comprising:

signal extractors, each of which extracts a signal with high level as a dominant signal, from an output of respective matched filter;

respreading circuits, each of which respreads spectrum of the dominant signal obtained by respective dominant signal extractor with the respective user'"'"'s spectrum spreading code;

a delay that delays the received signal by a predetermined period;

first adders, each of which subtracts outputs of the respreading circuits other than a specific user'"'"'s respread signal, from the output of the delay;

second matched filters, each of which despreads the spectrum of an output of the respective first adder, with the spectrum spreading codes assigned to the specific user; and

decision circuits, each of which determines respective user signal from each of the second matched filters.

18. A spread spectrum communication station according to claim 17, wherein:

each of the signal extractors extracts the signal with high level by a threshold operation using a product of the maximum output of the respective first matched filter by a predetermined ratio as a threshold.