JP2001094470A - Cdma demodulation circuit and cdma communication unit provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably identify a spread code included in a received signal by permitting errors in the initial timing of the spread code used for inverse spread processing. SOLUTION: A spread code generating circuit 40 generates three spread codes P1, P2, P3 whose phases are shifted by one chip each in a spread code identification mode, a main inverse spread circuit 41 and two auxiliary inverse spread circuits 42, 43 individually apply inverse spread processing to a received signal RS by using these spread codes P1, P2, P3. A 1st selection circuit 44 selects an inverse spread signal with the largest signal power among inverse spread signals SR1, SR2, SR3 outputted respectively from the three inverse spread circuits 41, 42, 43 and the identification is discriminated based on the inverse spread signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a code division multiple access (CDMA) as a radio access system.
The present invention relates to a CDMA communication device used in a mobile communication system adopting a Multiple Access (Multiple Access) system and a CDMA demodulation circuit thereof.

[0002]

2. Description of the Related Art In recent years, a mobile communication system employing a CDMA system has attracted attention. The CDMA mobile communication system uses a spread spectrum communication system, and performs communication as follows, for example.

[0003] That is, a communication device on the transmitting side firstly primary-modulates digitized voice data and image data by a digital modulation method such as a PSK modulation method. next,
The modulated data is spread into a wide-band transmission signal by spread spectrum using a spreading code, and the spread transmission signal is converted into a radio frequency signal and transmitted. On the other hand, the communication device on the receiving side first performs spectrum despreading on the received radio frequency signal using the same spreading code as that used in the communication device on the transmitting side.
Then, PSK (Phas
e Shift Keying) The received data is reproduced by performing primary demodulation using a digital demodulation method such as a demodulation method.

The CDMA system (1) uses a spread spectrum technique to easily maintain a high communication quality with respect to a change in the communication environment such as fading. (2) By using the RAKE reception method, a soft handover is possible, and a stable handover without instantaneous interruption of communication can be realized. (3) High frequency use efficiency can be realized by sharing one radio frequency by many users. Etc., a frequency division multiple access system (FDMA: Frequency)
Division Multiple Access) and time division multiple access (T
It has an advantage that DMA (Time Division Multiple Access) does not have.

In the CDMA communication apparatus used in this type of system, when the power is turned on, when the communication apparatus returns from the outside of the communication area, or when the apparatus moves between cells, the communication apparatus of the communication partner uses the communication apparatus before starting communication. It is necessary to identify the spreading code used. The identification of the spreading code is based on
Despreading is sequentially performed using a plurality of spreading code candidates stored in advance, and it is checked whether significant information can be extracted by this.

However, in the CDMA communication device, if the phase difference between the spread code included in the received signal and the spread code used for despreading is shifted by one chip or more, a correct despread output cannot be obtained. Therefore, in order to correctly estimate the spreading code used by the transmitting side, it is necessary to control the phase of the spreading code used by the receiving side for despreading to match the phase of the spreading code included in the received signal. . As means for obtaining a spreading code candidate having a correct phase, in addition to a despreading circuit for extracting information, two despreading circuits that perform despreading with spreading codes whose phases are shifted in the leading direction and the lagging direction, respectively. A circuit that prepares and extracts timing control information from the outputs of these two despreading circuits to control the phase of a spreading code candidate is known.

This spread code phase synchronization circuit starts despreading at a phase slightly deviated from a normal phase, obtains error information from a despreading circuit for extracting a timing control signal, and uses this error information as a basis. , The phase of the spreading code candidate is variably controlled little by little, and finally the correct despreading timing is set and maintained. At this time, the time required for controlling to the correct timing is generally very long in consideration of communication under low S / N.

If the number of spreading code candidates is small and the time available for identifying spreading codes can be made sufficiently long, the phase of the spreading code candidates is controlled to the correct timing in the spreading code phase synchronization circuit. Just wait until it is done. However, if the number of spreading code candidates is large or the time available for identification of the spreading code is short,
Before the timing control by the spread code phase synchronization circuit is completed, the spread code used for identification must be extracted.

Here, the signal amplitude after despreading when the phase of the spreading code candidate is shifted is smaller than the signal amplitude when despreading using the spreading code candidate having the correct phase. For this reason, although the types of the spreading codes match, it is determined that significant despreading cannot be performed, and the identification of the spreading code may fail.

[0010]

As described above, in the conventional CDMA communication apparatus, when the initial timing of the spreading code candidate used for identifying the spreading code used by the communication apparatus on the transmitting side is shifted, the reverse occurs. An error may occur in the spread output and identification of the spread code may fail.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to identify a spread code included in a received signal by allowing an error in an initial timing of a spread code used for despreading. And a CDMA communication apparatus including the CDMA demodulation circuit.

[0012]

In order to achieve the above object, a CDMA demodulation circuit according to the present invention generates a previously prepared spreading code candidate at an arbitrary initial timing, and generates a first spreading code candidate. The spread code candidate generating means for generating a plurality of second spread code candidates each having a predetermined phase difference in the leading direction and the delay direction, and the received CDMA radio signal is generated by the spreading code candidate generating means. First despreading means for despreading and outputting the received signal by a first spreading code candidate;
The plurality of second codes generated by the spreading code candidate generating means
A plurality of second despreading means for despreading and outputting the respective spread code candidates, and comparing the levels of the respective despread signals output from the first and second despreading means with each other. Based on the comparison result of the means and this comparison means,
First selecting means for selecting a despread signal having the most appropriate level from among the despread signals output from the first and second despreading means; and a spreading means used for the CDMA radio signal. When the code is identified, the despread signal selected by the first selection means is selected and subjected to identification determination processing, and the despread signal output from the first despread means is selected during information communication. And a second selecting means for performing information reproduction processing.

Therefore, according to the present invention, the received C
The DMA radio signal includes not only a first spreading code candidate having a normal phase, but also a plurality of second spreading code candidates whose phases are shifted by a predetermined amount in the leading and lagging directions with respect to the first spreading code candidate. Are despread, and a signal most suitable for identification determination is selected from these despread outputs. For this reason, even if the initial timing of the first spreading code candidate deviates from the normal phase, identification can be performed using the signal despread by the second despreading means instead. That is, even if there is an error in the initial timing of the spreading code candidate used for the despreading, this is allowed, and the identification of the spreading code can be performed reliably.

Further, the present invention further comprises a phase control means in addition to the above configuration, and the phase control means uses the received CDMA signals based on the levels of the despread signals output from the plurality of second despreading means. In order to reduce the phase difference between the spreading code used for the radio signal and the first spreading code candidate, the phase of the first spreading code candidate is variably controlled.

By doing so, the deviation amount of the initial timing of the spreading code candidate deviates from the assumed range, whereby an appropriate despread output can be obtained from both the first and second despreading means. Even in such a case, the phase of the spreading code candidate is variably controlled based on the despreading output level of the second despreading means, and the timing shift amount of the spreading code candidate is corrected to the above assumed range. For this reason, it becomes possible to obtain an appropriate despread output from any of the first and second despreading means, and it is possible to identify a spreading code based on the despread output.

Further, according to the present invention, a spread code generating means includes:
A plurality of first codes whose phases are shifted by a predetermined first phase amount in the leading and lagging directions with respect to the first spreading code candidate, respectively, A function of generating a plurality of second codes shifted in phase in the delay direction by a second phase amount smaller than the first phase difference, and when identifying a spread code, the first code is used. The second spreading code is given to the second despreading means as a second spreading code candidate.
It is also characterized in that the spread code candidate is given to the second despreading means.

In this way, when a spreading code is identified, a spreading code candidate having a large phase difference is supplied to the first and second despreading means. The error is enlarged and identification becomes easier. On the other hand, at the time of information reception, a spreading code candidate having a small phase difference is supplied to the first and second despreading means, so that the phase control error of the first spreading code candidate is reduced,
Thereby, reception quality can be improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 shows a CDMA according to the present invention.
FIG. 2 is a circuit block diagram illustrating a first embodiment of the communication device.

In FIG. 1, a transmitted voice signal of a speaker output from a microphone 10a is converted to a digital signal by an analog-to-digital converter (AD) 11a, and then is converted to a voice coded-decoded ( Voice coder −decoder
, Hereinafter referred to as Vocoder) 12. The vocoder 12 encodes the input digital audio signal at a coding rate of, for example, 64 kbps.

The control circuit 13 adds a control signal and the like to the coded digital audio signal output from the vocoder 12, and thereby creates transmission data. The transmission data is encoded by a convolutional encoder 15 after an error detection code and an error correction code are added by a data generation circuit 14. Then, the encoded transmission data is subjected to an interleaving process in an interleaving circuit 16. The transmission data output from the interleave circuit 16 is primary-modulated by a modulation circuit (not shown) and then spectrum-spread by a spectrum spreader 17 by a spreading code corresponding to a channel specified by the control circuit 13 to be converted into a wideband signal. Is done. As the primary modulation method, for example, a QPSK method is used.

This spread spectrum transmission signal is:
After unnecessary frequency components are removed by the digital filter 18, a digital-analog converter (DA) 19
Is converted into an analog transmission signal. Then, the analog transmission signal is up-converted to a predetermined radio frequency by the analog front end 20, controlled to a predetermined transmission power level, and then transmitted from the antenna 21 to a base station (not shown).

On the other hand, the spread spectrum radio signal received by the antenna 21 is amplified by the low noise amplifier in the analog front end 20, and then down-converted into a signal of an intermediate frequency or a baseband frequency. The received signal output from the analog front end 20 is converted into an analog-digital converter (A
-D) After being converted into a digital signal at a predetermined sampling period in 22, the digital signal is input to the RAKE receiver 25.

The RAKE receiver 25 has n (n = 1, 2, 2)
3,...) Finger circuits 31 to 3n and a symbol combiner 30. Each of the finger circuits 31 to 3n has a function as a CDMA demodulation circuit, and generates a spreading code corresponding to the wireless communication channel specified by the control circuit 13. Then, by performing spectrum despreading processing on the reception signal of a desired path having a high reception level using the spreading code, the reception signals of a maximum of n paths are separated from the multipath radio signal and reproduced. The symbol synthesizer 30 includes the finger circuits 31 to 3
n, and selectively synthesizes the symbols after synchronizing the timing with the despread signal output from n and outputs the resultant.

The demodulated symbols output from the RAKE receiver 25 are input together with timing information to a primary demodulation circuit (not shown), where they are primarily demodulated, and then input to a deinterleave circuit 26. Then, the deinterleave circuit 26 performs a deinterleave process. The demodulated symbols after the deinterleaving are Viterbi-decoded in the Viterbi decoder 27, and the demodulated symbols after the Viterbi decoding are error-correction-decoded by the error correction circuit 28 to become reception data, which are input to the control circuit 13. .

In the control circuit 13, the input received data is separated into audio data and control data. The voice data is decoded by the vocoder 12 and then converted into an analog signal by a digital-to-analog converter (DA) 11b, and then output from the speaker 10b.

The keypad / display 29 is
It is provided for a user to input and set dial data, control data, and the like, and to display various information related to the operation state of the communication device. This keypad /
The operation of the display 29 is controlled by the control circuit 13.

The finger circuits 31 to 3n
Is configured as follows. FIG. 2 is a circuit block diagram showing the configuration.

That is, each of the finger circuits 31 to 3n includes:
Spreading code generation circuit 40 and main despreading circuit 4 for extracting information
1 and two auxiliary despreading circuits 42 and 43 for assisting identification.
And first and second selection circuits 44 and 45, a power detection circuit 46, and a comparison circuit 47.

The spreading code generation circuit 40 selects one of the spreading code candidates according to the spreading code type PC specified by the control circuit 13, and transmits the selected spreading code to the initial code specified by the control circuit 13. It occurs in synchronization with the timing TI. The spreading code generated at this time is composed of a normal phase spreading code P1, and spreading codes P2 and P3 whose phases are shifted by one chip in the lagging direction and the leading direction, respectively, with respect to the normal phase spreading code P1.

The main despreading circuit 41 for extracting information multiplies the received signal RS by the spreading code P1 of normal phase generated from the spreading code generating circuit 40, accumulates the multiplied output for one symbol time, and despreads. Output as signal SR1.

Two auxiliary despreading circuits 42 for assisting identification are provided.
43 multiplies the received signal RS by the spread code P2 of the lag phase and the spread code P3 of the lead phase generated from the spread code generation circuit 40, accumulates the multiplied output for one symbol time, and demultiplexes the despread signal SR2. , SR3.

The main despreading circuit 41 and each of the auxiliary despreading circuits 42 and 43 are used to generate one symbol of the despread signal SR.
Each time 1, SR2 and SR3 are output, the accumulated value is cleared to 0.

The power detecting means 46 is connected to each of the despreading circuits 4
Despread signals SR1, SR output from 1, 42, 43
2, a value corresponding to the signal power of SR3 is calculated, and the calculated value is output to the comparison circuit 47. As a calculation method of the value according to the signal power, for example, each despread signal SR1, SR2, SR3
, And the despread signals SR1, SR
2 and 3 that smoothes SR3 with an appropriate time constant are used.

The comparing circuit 47 compares the power values of the respective despread signals SR1, SR2, SR3 outputted from the upper electromotive force detecting circuit 46 with each other, and outputs a selection control signal LC indicating the signal having the largest power value. 1 to the selection circuit 44.

The first selection circuit 44 selects one of the despread signals SR1, SR2, SR3 output from the despread circuits 41, 42, 43 based on the selection control signal LC.
The signal having the largest signal power value is selected and output to the second selection circuit 45 as the selected despread signal SR0.

The second selection circuit 45 receives the selected despread signal SR0 output from the first selection circuit 44 and the selected despread signal SR0 from the main despread circuit 41 in response to the mode switching signal MS supplied from the control circuit 13. The output despread signal SR1 is alternatively selected and output. Specifically, in the spread code identification mode, the selected despread signal SR0 output from the first selection circuit 44 is selected and output to the subsequent circuit as a despread signal SR for identification determination. On the other hand, in the information communication mode after the end of the spread code identification, the despread signal SR1 output from the main despread circuit 41 is output.
And despread it for the despread signal S for the received data reproduction process.
It is output to the subsequent circuit as R.

Next, the operation of the CDMA demodulation circuit configured as described above will be described. When the power is turned on, the control circuit 13 performs an initial setting of each section of the apparatus, first sets a spreading code identification mode to identify a spreading code used by the base station, and starts control.

That is, first, to the second selection circuit 45, a mode switching signal MS for designating a spreading code identification mode.
give. In addition, one spreading code candidate is selected from among a plurality of spreading code candidates prepared in advance, and the type PC of the selected spreading code candidate is designated to the spreading code generation circuit 40, and the generation timing of the spreading code is determined. An initial timing TI is provided to specify an initial value.

Then, from the spreading code generation circuit 40,
A normal phase spreading code P1 related to the spreading code candidate of the designated type PC, and spreading codes P2 and P3 whose phases are shifted by one chip in the lag direction and the leading direction, respectively, with respect to the normal phase spreading code P1. Are generated, and these spreading codes P1, P2, and P3 are supplied to a main despreading circuit 41 and auxiliary despreading circuits 42 and 43, respectively.

Main despreading circuit 41 and auxiliary despreading circuit 4
2 and 43, the received signal RS and the spread codes P1, P2, and P3 supplied from the spread code generation circuit 40, respectively.
Are multiplied, and despread signals SR1, SR2, SR3 obtained by accumulating the multiplied outputs for one symbol time are output and input to the power detection circuit 46. The power detection circuit 46 calculates the signal power values of the despread signals SR1, SR2, SR3, respectively, and the comparison circuit 47 detects the largest signal power value based on the calculation results. Then, a selection control signal LC for selecting the despread signal having the maximum signal power is supplied from the comparison circuit 47 to the first selection circuit 44. Therefore, the first selection circuit 44 selectively outputs the despread signal SR0 having the maximum signal power.

At this time, the mode selection signal MS indicating the spreading code identification mode is supplied from the control circuit 13 to the second selection circuit 45. Therefore, the second selection circuit 4
In 5, the despread signal SR0 selected and output from the first selection circuit 44 is selectively output.

That is, when the spreading code identification mode is set, the despread signals SR1 and SR output from the main despreading circuit 41 and the two auxiliary despreading circuits 42 and 43 are output.
2 and SR3, the despread signal having the largest signal power value selected by the first selection circuit 44 is selected, and identification determination is performed based on the despread signal SR.

Therefore, if the initial timing of the spreading code P1 supplied to the main despreading circuit 41 does not include a phase error, for example, as shown in FIG. A spread signal SR1 is obtained. On the other hand, for example, as shown in FIG. 3B, the phase of the spread code in the received signal RS is shifted by one chip, and as a result, the despread signal SR1 having the maximum power cannot be obtained from the main despread circuit 41. However, one of the auxiliary despreading circuits 42 and 43 (the auxiliary despreading circuit 43 in the example of FIG. 3B) shows that the phase of the spreading code P3 matches the phase of the spreading code of the received signal RS. A large despread signal having a large signal power is obtained. For this reason, correct spreading code identification can be performed using the despread signal output from the auxiliary despreading circuit 43.

A despread signal indicating that the phases match from each of the main despreading circuit 41 and the two auxiliary despreading circuits 42 and 43, that is, a despread signal having a signal power value equal to or higher than a threshold value. If not obtained, the control circuit 13 selects the next spreading code candidate and specifies its type PC to the spreading code generation circuit 40 together with the initial timing TI. For this reason, the CDMA demodulation circuit performs the same despread signal selection operation as that described above for the next selected spread code candidate.

On the other hand, when the identification of the spreading code used by the base station is completed, the control circuit 13 enters the information communication mode, and outputs a mode switching signal MS for designating the information communication mode. A spreading code generation circuit 4
For 0, the type PC of the identified spreading code is given together with the initial timing TI.

Accordingly, the spread code generation circuit 40 generates the identified spread code, whereby the main despreading circuit 41 performs despreading processing of the received signal RS by the spread code. Since the mode switching signal MS specifies the information communication mode, the despreading circuit 4
1 is output from the second selection circuit 4
5 and is supplied to a subsequent circuit for reproduction of received data.

In the information communication mode immediately after the end of the identification, the broadcast information transmitted by the base station is received.
The broadcast information includes various parameters of the base station, and when these parameters are stored, the CDMA communication device enters a standby mode after transmitting and receiving control information as needed.

As described above, in the first embodiment, in the spread code identification mode, the three spread codes P1, P
2, P3, and these spreading codes P1, P2, P
3, the despreading of the received signal RS is performed in the main despreading circuit 41 and the two auxiliary despreading circuits 42 and 43, respectively. Then, these three despreading circuits 41, 42, 43
Out of the despread signals SR1, SR2, and SR3 output by the first selecting circuit 44, and the identification determination is performed based on the despread signal. I have.

Therefore, the initial timing of the spreading code P1 supplied to the main despreading circuit 41 is shifted by one chip with respect to the phase of the spreading code in the received signal RS. Even if the despread signal is not obtained, the despread signal having a large signal power indicating that the phase of the spread code P2 or P3 matches the spread code phase of the received signal RS from one of the auxiliary despread circuits 42 and 43. A signal is obtained. Therefore, correct spreading code identification can be performed using the despread signals SR2 and SR3 output from the auxiliary despreading circuits 42 and 43.

(Second Embodiment) CD according to the present invention
The second embodiment of the MA demodulation circuit includes a spreading code generation circuit having a phase variable control function in addition to the functions described in the first embodiment, and sets the initial timing of the spreading code supplied to each despreading circuit. When there is a phase error, the phase of the spreading code is variably controlled to reduce the phase error.

FIG. 4 shows a CD according to the second embodiment.
FIG. 3 is a circuit block diagram illustrating a configuration of an MA demodulation circuit. 2, the same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description is omitted.

The CDMA demodulation circuit of this embodiment includes a spread code generation circuit 50 having a phase variable control function, and two delay circuits 51, which delay the phase of the spread code output from the spread code generation circuit 50, 52 are provided.

The spreading code generation circuit 50 selects one of the spreading code candidates according to the spreading code type PC specified by the control circuit 13, and the control circuit 13 specifies the selected candidate spreading code P 3. It occurs in synchronization with the initial timing TI. Further, the difference between the signal power detection values of the auxiliary despreading circuits 42 and 43 output from the power detection circuit 46 is obtained, and the generation phase of the spreading code P3 is variably controlled so that the difference approaches zero.

The first delay circuit groups 51 and 52 are for applying a one-chip phase difference to the spreading codes P3, P1 and P2 supplied from the spreading code generating circuit 50 to the despreading circuits 43, 41 and 42, respectively. The spread code generation circuit 50
Are sequentially delayed one chip at a time to generate spreading codes P1 and P2, and supply these spreading codes P1 and P2 to despreading circuits 41 and 42.

With such a configuration, when the power is turned on and the type PC of the spreading code candidate is specified by the control circuit 13 and the initial timing TI is specified, the spreading code generation circuit 40 specifies The spreading code of the specified type PC is generated one chip ahead of the designated initial timing, and this spreading code P3 is supplied to the auxiliary despreading circuit 43 as it is. The spreading code P3 is sequentially delayed one chip at a time by delay circuits 51 and 52, and
1, P2, and supplied to the main despreading circuit 41 and the auxiliary despreading circuit 42, respectively.

Main despreading circuit 41 and auxiliary despreading circuit 4
2 and 43, the received signal RS and the spread codes P1, P2, and P3 supplied from the spread code generation circuit 40, respectively.
Are multiplied, and despread signals SR1, SR2, SR3 obtained by accumulating the multiplied outputs for one symbol time are output and input to the power detection circuit 46. The power detection circuit 46 calculates the signal power values of the despread signals SR1, SR2, SR3, respectively, and the comparison circuit 47 detects the largest signal power value based on the calculation results. A selection control signal L for selecting the despread signal having the maximum signal power
C is supplied from the comparison circuit 47 to the first selection circuit 44. As a result, the first selection circuit 44 selects and outputs the despread signal SR0 having the maximum signal power. The despread signal SR0 is supplied to the spread code identification determination processing via the second selection circuit 45.

However, suppose that the spreading code generator 5
It is assumed that the initial phase of the spread code P3 generated from 0 includes an error of less than one chip with respect to the spread code phase of the received signal. Then, the difference between the signal power values of the despread signals SR1, SR2, and SR3 detected by the power detection circuit 46 decreases, and as a result, the detection accuracy of the maximum signal power by the comparison circuit 47 decreases.

However, in the present embodiment, of the signal power values calculated by the power detection circuit 46, the despread signal S
The signal power values of R2 and SR3 are input to spreading code generation circuit 50. The spreading code generation circuit 50 obtains the difference between the signal power values of the input despread signals SR2 and SR3, and variably controls the generation phase of the spreading code P3 so that the difference approaches zero. Therefore, the initial phase error of the spread code is corrected, whereby the signal power of one of the despread signals SR1, SR2, and SR3 is significantly larger than that of the other, and as a result, the comparison circuit 47 Thus, the despread signal having the maximum signal power can be detected with high accuracy.

As described above, according to the second embodiment, of the signal power values calculated by the power detection circuit 46,
The signal power values of the despread signals SR2 and SR3 are input to the spreading code generation circuit 50, and the despread signal SR
2, the generation phase of the spreading code P3 is variably controlled based on the difference between the signal power values of SR3. Therefore, even if the initial phase of the spread code P3 generated from the spread code generator 50 includes an error of less than one chip with respect to the spread code phase of the received signal RS, the initial phase error of the spread code P3 is corrected. Is done. Therefore, each despread signal SR1, SR2, S
The signal power of one of the despread signals of R3 is significantly larger than the others, and the comparison circuit 47 can accurately detect the despread signal of the maximum signal power and use it for identification determination.

In the second embodiment, the initial timing control of the spreading code is performed by using the despread outputs SR2 and SR3 of the auxiliary despreading circuits 42 and 43. That is, the auxiliary despreading circuits 42 and 43 are commonly used for outputting the despread signals SR2 and SR3 used for identification and for outputting the despread signals SR2 and SR3 necessary for controlling the initial timing of the spreading code. ing. Therefore, the circuit configuration can be simplified and miniaturized as compared with a case where a despreading circuit is separately provided for each application.

(Third Embodiment) CD according to the present invention
In the third embodiment of the MA demodulation circuit, in addition to the function described in the second embodiment, a phase difference switching means for the spreading code is provided.
The phase difference between the spreading codes P1, P2, and P3 supplied to the spreading codes 2, 43 is set to be large in the spreading code identification mode and small in the information communication mode.

FIG. 5 shows a CD according to the third embodiment.
FIG. 3 is a circuit block diagram illustrating a configuration of an MA demodulation circuit. 4, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description is omitted.

From the spreading code generation circuit 50 to each despreading circuit 4
A first delay circuit group 51, 52, second delay circuit groups 53, 54, and delay amount selection circuits 56, 57 are provided on the spreading code supply path to 1, 42, 43.

The first delay circuit groups 51 and 52 are for applying a one-chip phase difference to the spreading codes P3, P1 and P2 supplied from the spreading code generation circuit 50 to the despreading circuits 43, 41 and 42, respectively. The spread code generation circuit 50
Are sequentially delayed one chip at a time to generate spreading codes P1 and P2, and supply these spreading codes P1 and P2 to despreading circuits 41 and 42.

The second delay circuit groups 53 and 54 apply a 1/2 chip phase difference to the spreading codes P3, P1 and P2 supplied from the spreading code generating circuit 50 to the respective despreading circuits 43, 41 and 42. The phase of the spread code P3 output from the spread code generation circuit 50 is sequentially delayed by 1/2 chip to generate spread codes P1 and P2, and these spread codes P1 and P2 are despread by a despreading circuit 41, 42.

The selection circuits 55 and 56 switch between the first delay circuit groups 51 and 52 and the second delay circuit groups 53 and 54 according to the mode switching signal MS generated from the control circuit 13. In the spreading code identification mode, the first delay circuit groups 51 and 52 are selected and despreading circuits 41 and 42 are selected.
To the second delay circuit group 5 in the information communication mode.
3, 54 are selected and connected to the despreading circuits 41, 42.

With such a configuration, first, in the spreading code identification mode, the first and second selection circuits 55 and 56
Of the delay circuit groups 51 and 52 are selected, whereby the despreading circuits 41, 42 and 43 have spread codes P1 and P having a one-chip phase difference as shown in FIG.
2, P3 are supplied. Therefore, in this case, the spreading code generation circuit 50 uses the difference between the signal powers of the despread signals SR2 and SR3 detected by the power detection circuit 46 as ±
It is possible to correct the phase error within the range of one chip.

That is, even if the initial timing of the spreading codes P1, P2, and P3 has a phase error of ± 1 chip,
By correcting this, identification can be performed correctly. FIG. 6A shows the relationship between the spread code delay amount and the phase error in this case.

On the other hand, when the identification of the spreading code is completed and the information communication mode is set, the selection circuits 55 and 56 cause
Of the delay circuit groups 53 and 54 are selected, whereby each of the despreading circuits 41, 42 and 43 has 1 as shown in FIG.
/ 2 chip spreading code P1, P2, given a phase difference
P3 is supplied. Therefore, in this case, the spread code generation circuit 50 can correct the phase error within the range of ± 1/2 chip based on the signal power of the despread signals SR2 and SR3 detected by the power detection circuit 46. Becomes

That is, in this case, the range in which the initial phase error of the spreading code can be corrected is narrowed to ± 1/2 chip.
Phase correction accuracy can be increased. FIG. 6B shows the relationship between the delay amount of the spreading code and the phase error in this case.

Therefore, according to the third embodiment, during the spread code identification process, the initial phase errors of the spread codes P1, P2, and P3 are corrected within a relatively wide lock range of ± 1 chip. Despread outputs SR1, SR2, SR3 of main despreading circuit 41 and auxiliary despreading circuits 42, 43
The identification and determination can be performed by selecting the despread output of the identification target from among.

On the other hand, during information communication, the spread code P
1, P2, and P3 are within the narrow lock range of ± １ ／ chip, but are corrected with high accuracy, and the respective despread outputs SR1 and SR1 of the main despreading circuit 41 and the auxiliary despreading circuits 42 and 43 are corrected. An identification determination can be made by selecting the despread output of the identification target from SR2 and SR3.

The present invention is not limited to the above embodiments. For example, as a method of calculating the signal power in the power detection circuit 46, a method of calculating the square value of the despread output for each symbol period or a method of calculating the square value of the despread output obtained for one symbol period at an appropriate time A filter smoothed by a constant filter can be used. In addition, both of these processing functions are provided, and in the spreading code identification mode, the square value of the despread output is output as it is without smoothing, and in the information communication, the square value of the despread output is smoothed and output. You may comprise.

Further, in each of the above embodiments, a wireless voice communication terminal such as a portable telephone device has been described as an example of a CDMA communication device. However, the present invention is not limited to a voice communication terminal, but a multimedia capable of transmitting images and computer data together. The present invention is applicable to a communication device. Further, the present invention is applicable not only to a wireless terminal but also to a wired terminal device.

Further, in the above embodiment, the CDMA demodulation circuit having the function of the present invention is connected to all the finger circuits 31 to 31.
3n is described as an example, but may be provided only in some of the finger circuits 31 to 3n. In addition, the type of the CDMA communication device, the circuit configuration of the CDMA demodulation circuit, and the like can be variously modified without departing from the scope of the present invention.

[0076]

As described in detail above, in the present invention, the first
In the despreading means, the received CDMA radio signal is despread by a first spreading code candidate generated at an arbitrary initial timing, and a plurality of second despreading means respectively execute the first spreading code candidate. A plurality of second phases whose phases are shifted by a predetermined amount in the leading and lagging directions, respectively.
The received CDMA wireless signal is despread by the spreading code candidate. When identifying the spreading code used for the CDMA radio signal, a despread signal having the most appropriate level among the despread signals output from the first and second despreading means is identified. This is selected and provided for identification determination processing, while at the time of information communication, the despread signal output from the first despreading means is directly selected and provided for information reproduction processing.

Therefore, according to the present invention, a CDMA demodulation circuit and a demodulation circuit capable of reliably identifying a spreading code included in a received signal by allowing an error in the initial timing of a spreading code used for despreading, and this demodulation circuit CDM with
A communication device can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an example of a CDMA communication device according to the present invention.

FIG. 2 is a circuit block diagram showing a first embodiment of a CDMA demodulation circuit provided in the CDMA communication device shown in FIG.

FIG. 3 is a timing chart used for explaining the operation of the CDMA demodulation circuit shown in FIG. 2;

FIG. 4 is a circuit block diagram showing a second embodiment of a CDMA demodulation circuit provided in the CDMA communication device shown in FIG.

FIG. 5 is a circuit block diagram showing a third embodiment of a CDMA demodulation circuit provided in the CDMA communication device shown in FIG.

FIG. 6 is a signal waveform diagram used to describe a timing control operation of the CDMA demodulation circuit shown in FIG.

FIG. 7 is a timing chart used for describing the operation of the CDMA demodulation circuit shown in FIG. 5;

[Explanation of symbols]

 11a, 22 ... Analog-digital converter (AD) 11b, 19 ... Digital-analog converter (DA) 12 ... Speech coding / decoding (vocoder) 13 ... Control circuit 14 ... Data generation circuit 15 ... Convolutional encoder 16 ... Interleave circuit 17 ... Spread spectrum device 18 ... Digital filter 20 ... Analog front end 21 ... Antenna 25 ... RAKE receiver 26 ... Deinterleave circuit 27 ... Viterbi decoder 28 ... Error correction circuit 29 ... keypad / display 30 ... symbol synthesizer 31-3n ... finger circuit 40,50 ... spreading code generator 41,42,43 ... despreading circuit 44 ... first selection circuit 45 ... second selection circuit 46 ... power Detection circuit 47 ... Comparison circuit 51, 52, 53, 54 ... Delay circuit 55, 56 ... Delay amount selection circuit

Claims (4)

[Claims] 1. A CDMA communication device for receiving a CDMA radio signal coming from a communication partner, identifying a spreading code used in the CDMA radio signal, and performing information communication with the communication partner. CDMA (Code Divis
In a demodulation circuit, a plurality of spread code candidates prepared in advance are generated at an arbitrary initial timing, and a plurality of phase shifts are performed on the first spread code candidate by a predetermined amount in the leading and lagging directions, respectively. A spreading code candidate generating means for generating a second spreading code candidate, and a first spreading and receiving means for despreading the received CDMA radio signal by using a first spreading code candidate generated by the spreading code candidate generating means. Despreading means; and a plurality of second despreading means for despreading the received CDMA radio signal with a plurality of second spreading code candidates generated by the spreading code candidate generating means, respectively, Comparing means for comparing the levels of the respective despread signals output from the first and second despreading means with each other; based on the comparison result of the comparing means, A first selecting means for selecting a despread signal whose level is most appropriate for identification from among the despread signals output from the respective despreading means, and a first selecting means for identifying the spreading code. A second selecting means for selecting the despread signal selected by the selecting means and providing the same for identification determination processing, and for information communication, selecting the despread signal output from the first despreading means and providing the same for information reproducing processing; A CDMA demodulation circuit comprising: 2. The spread code used for the received CDMA radio signal and the first spread code based on the level of the despread signal output from the plurality of second despreading means. In order to reduce the phase difference with the candidate, the first
2. The CDMA demodulation circuit according to claim 1, further comprising phase control means for variably controlling the phase of said spread code candidate. 3. The spread code generating means includes: a plurality of first codes each having a predetermined first phase difference in a leading direction and a lagging direction with respect to a first spreading code candidate;
A function of generating a first spreading code candidate and a plurality of second codes each having a second phase difference smaller than the first phase difference in a leading direction and a lagging direction, respectively; In this case, the first code is selected as a second spreading code candidate and given to the second despreading means. On the other hand, at the time of information communication, the second code is selected as a second spreading code candidate. 3. The CDMA demodulation circuit according to claim 2, wherein said CDMA demodulation circuit provides the signal to said second despreading means. 4. A CDMA system for receiving a CDMA radio signal coming from a communication partner and demodulating the received CDMA radio signal with a RAKE receiver having a plurality of finger circuits.
(Code Division Multiple Access) In a communication device, a previously prepared spreading code candidate is generated at an arbitrary initial timing, and a phase is shifted by a predetermined amount in the leading direction and in the lagging direction with respect to the first spreading code candidate. Spreading code candidate generating means for generating a plurality of second spreading code candidates, and the received CDMA radio signal is despread by the first spreading code candidate generated by the spreading code candidate generating means and output. First despreading means, and a plurality of second despreading means for despreading the received CDMA radio signal with a plurality of second spreading code candidates generated by the spreading code candidate generating means and outputting the despreaded CDMA radio signals. And comparing means for comparing the levels of the despread signals output from the first and second despreading means with each other; based on the comparison result of the comparing means, And first selecting means for selecting a despread signal whose level is most appropriate for identification from the despread signals output from the second and second despreading means, and a spreading code used for the CDMA radio signal. In the case of identifying, the despread signal selected by the first selection means is selected and subjected to an identification determination process, and the despread signal output from the first despread means is selected during information communication. C provided with second selecting means for performing information reproduction processing.
A CDMA communication device comprising a DMA demodulation circuit, wherein the CDMA demodulation circuit is provided in at least one of the plurality of finger circuits.