JPH09214466A - Spectrum spread communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the deviation of an orthogonal axis and the phase/frequency deviation of a reproduced carried by diffusing/modulating an in-phase channel and an orthogonal channel through the use of different spread codes. SOLUTION: Transmission data #1 (data for in-phase channel) is spread/ modulated by a first spread code PN1 outputted from a code generator 14 in a first spread modulator 11 and is inputted to an orthogonal modulator 13. Transmission data #Q (data for orthogonal channel) is spread/modulated by a second diffusion code PN2 outputted from the code generator 14 in a second diffusion modulator 12 and it is inputted to the orthogonal modulator 13. Since spread modulation is executed by using the spread codes peculiar to the channels, the other channel signal is suppressed by the ratio of a mutual correlation value for a self correlation peak, the influence of the other channel signal for a demodulation signal is reduced and an error rate characteristic improves. Furthermore, a permission range for the deviation of the orthogonal axis and the phase/frequency deviation of the reproduced carrier for realizing the desired error rate is enlarged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication device and method, and more particularly to a quadrature modulated spread spectrum communication device and method.

[0002]

2. Description of the Related Art A spread spectrum communication system uses a spread code sequence such as a pseudo noise code (PN code) from a normally transmitted digital signal to generate a signal having an extremely wider bandwidth than the original data. It is converted into an RF (radio frequency) signal and transmitted.

Japanese Patent Application No. 5-344920 discloses a quadrature modulated spread spectrum communication device. Japanese Patent Application No. 5-344920
In the No. 1, a system multiplexed by a plurality of spreading codes is described. FIG. 8 shows a general transmitter and FIG. 9 shows a receiver in the case of not multiplexing. In FIG. 8, the transmission data is converted into parallel data of two channels of an in-phase channel (Ich) and a quadrature channel (Qch), spread-modulated by the same spreading code PN1 output from the code generator 84, respectively, It is quadrature-modulated, converted to a desired frequency, and transmitted.

In FIG. 9, on the receiving side, the carrier reproduced by the carrier reproducing circuit 91 is used to separate the received signal into Ich and Qch, and the same spreading code PN as that on the transmitting side is used.
Spreading demodulation is performed by correlating with 1, and then data demodulation is performed.

In Japanese Patent Application No. 5-344920, as shown in FIG. 10, both Ich and Qch are multiplexed by the same plurality of spreading codes, orthogonally modulated and transmitted.

[0006]

However, in the above conventional example, the in-phase channel (Ich) and the quadrature channel (Qch) are used.
Since and are spread-modulated using the same spreading code, they are vulnerable to the deviation of the orthogonal axis and the phase / frequency deviation of the reproduced carrier, as in normal QPSK, and require highly accurate orthogonality and the reproduced carrier. However, it is difficult to reduce the size of the device, and expensive parts are required. Also,
In order to improve the phase / frequency accuracy of the reproduced carrier, the time required for carrier reproduction increases, and in packet communication in particular, there is a problem that the overhead increases and the throughput decreases.

[0007]

According to the present invention, the in-phase channel (Ich) and the quadrature channel (Qch) are spread-modulated by using different spreading codes. Furthermore, it is desirable that the spreading codes used in the respective channels have a small cross-correlation, and that the cross-correlation be 0, that is, orthogonal.

With this configuration, the signal of the in-phase channel and the signal of the quadrature channel are not completely separated due to the shift of the quadrature axis or the phase / frequency shift of the reproduced carrier, and the signal of the other channel is mixed in one channel. Also, since the spread demodulation is performed using the spread code unique to the channel, the other channel signal is suppressed by the ratio of the cross-correlation value to the autocorrelation peak, the influence of the other channel signal on the demodulated signal is reduced, and the error rate characteristic is reduced. improves. In addition, the allowable range for the deviation of the orthogonal axes and the phase / frequency deviation of the reproduced carrier to achieve the desired error rate is widened, and the axis deviation correction circuit is no longer necessary, and the phase / frequency correction circuit is unnecessary or can be simplified. Therefore, the device can be downsized. Furthermore, an expensive highly stable oscillator, a highly accurate quadrature modulator, or the like can be replaced with an inexpensive and less accurate component, and the cost can be reduced.

Further, demodulation can be performed without waiting until the phase / frequency of the reproduction carrier is locked with high accuracy.
Overhead can be shortened and throughput can be increased.

[0010]

1 is a schematic configuration diagram of a first transmission section of a spread spectrum communication apparatus embodying the present invention. In FIG. 1, reference numerals 11 and 12 denote spread modulators that spread-modulate transmission data with spread codes. Reference numeral 13 denotes a quadrature modulator that multiplies two input signals by mutually orthogonal carrier waves and synthesizes them. 13 is usually a local oscillator, 90
It consists of a phase shifter, mixer, and combiner. A code generator 14 generates a spread code.

In the figure, transmission data #I (data for in-phase channel) is coded by the first spread modulator 11 in the code generator 1.
Spreading modulation is performed by the first spreading code PN1 output from No. 4 and input to the quadrature modulator 13. Further, the transmission data #Q (orthogonal channel data) is the second spread modulator 1
Second spread code PN output from the code generator 14 at 2
Spread modulation is performed by 2 and input to the quadrature modulator 13. In the quadrature modulator 13, the input signal from the first spread modulator 11 and the input signal from the second spread modulator 12 are modulated by mutually orthogonal carrier waves, and both are combined and output. The signal output from 13 is subjected to processing such as amplification, filtering, and frequency conversion as necessary, and transmitted.

FIG. 2 is a schematic configuration diagram of the first receiving section of the spread spectrum communication apparatus embodying the present invention. In FIG. 2, reference numeral 21 is a carrier reproduction circuit for reproducing a carrier from a received signal. As the carrier reproduction circuit 21, there is a carrier extraction circuit using a Costas loop or a quadrupler. Reference numerals 22 and 24 are baseband conversion circuits for converting a signal of a desired frequency into a baseband signal, and 23 is a reference numeral 90.
Degree phase shifter, 25 and 26 are correlators for performing a correlation operation between a desired spread code and an input signal, and 27 and 28 are correlator 2 respectively.
It is a judging device for judging the data based on the outputs from Nos. Reference numeral 29 is a synchronizing circuit for synchronizing clocks and codes between the received signal and the spread code output from the code generator 30. A code generator 30 generates a spread code.

In FIG. 2, the received signal r (t) is subjected to processing such as amplification, filtering, frequency conversion, etc., if necessary, and then branched, and a part of the received signal is input to the carrier regeneration circuit 21, The carrier is extracted and output. A part of the received signal is input to the synchronizing circuit 29, and the received signal and the spread code generated by the code generator 30 are clock-synchronized and code-synchronized. As a synchronizing circuit, a sliding correlator, a delay locked loop, and Japanese Patent Application No. 6-3327
15 and a circuit using a surface acoustic wave element as described in Japanese Patent Application No. 63-287101. Further, a part of the received signal is further branched into two, one of which is input to the first baseband conversion circuit 22 together with the carrier output from the carrier reproduction circuit 21, and the baseband signal rI (t) of the in-phase component is extracted. . On the other hand, the carrier output from the carrier reproduction circuit 21 is input to the second baseband conversion circuit 24 together with the signal obtained by 90-degree phase shifting by the 90-degree phase shifter 23, and the baseband signal rQ (t) of the orthogonal component is extracted. Be done. The baseband signal rI (t) of the in-phase component is subjected to correlation calculation with the first spread code PN1 output from the code generator 30 in the first correlator 25, and the correlation result is sent to the decision unit 27. Data demodulation. The baseband signal rQ (t) of the quadrature component is subjected to correlation calculation with the second spread code PN2 output from the code generator 30 in the second correlator 26,
The decision unit 28 demodulates the data based on the correlation result.

Here, as an example, first and second spreading codes
PN1 and PN2 are replaced by PN1: [1, 1, 1, 1, -1, 1, -1, 1, 1, -1, -1, 1, -1, -1, -1, -1] PN2: [ -1, 1, -1, 1, 1, 1, 1, 1, -1, -1, 1, 1, 1, -1, 1, -1], the first and second spreading codes PN1 , PN2 have cross-correlation characteristics as shown in FIG. 6, and when both codes are transmitted in synchronization, the cross-correlation value is 0, that is, orthogonal codes.

Therefore, even if the carrier reproduced by the carrier reproducing circuit 21 is out of phase with the received signal, the first correlator 25 spread-modulates it on the transmitting side by the second spreading code PN2. With respect to the components, the correlation output becomes 0, and only the components spread-modulated by the first spreading code PN1 on the transmission side are extracted. Similarly, in the second correlator 26, the correlation output of the component spread-modulated by the first spreading code PN1 on the transmitting side becomes 0, and the second component on the transmitting side receives the second
Only the component spread-modulated by the spreading code PN2 of is extracted.

In the present embodiment, the carrier reproducing circuit 21
Is recovering the carrier from the received signal, but the correlator 2
It may be configured to feed back from the outputs of 5 and 26.

FIG. 3 is a block diagram of a second receiving section of the spread spectrum communication apparatus embodying the present invention. The transmitting unit is the same as in FIG. 3, the same parts as those in FIG. 2 are designated by the same reference numerals. This receiving unit does not reproduce the carrier, but converts it into a quasi-baseband signal by the output of the oscillator 31 having a frequency substantially equal to the intermediate frequency obtained by frequency-converting the transmission frequency or the received signal, and demodulates.

In FIG. 3, the output signal from the oscillator 31 is substantially equal in frequency to the received signal but not in phase, so the outputs r _I and r _Q from the baseband converters 22 and 24 are the same.
Is r _I = t _I cos α + t _Q sin α r _Q =-t _I sin α + t _Q cos α. Here, t _I and t _Q are the in-phase component and the quadrature component of the transmission signal, and α is the phase difference between the output of the oscillator 31 and the reception signal.

The outputs r _I and r _Q from the baseband converters 22 and 24 are respectively used as correlators 25-1 and 25-2 for spreading code PN1.
It is input to 5-2 and is correlated with the spread code PN1 synchronized with the received signal. Then, since the spreading code PN1 and the spreading code PN2 have little orthogonality or cross-correlation, the correlators 25-1 and 25-
From the output from 2, the quadrature component of the transmission signal is suppressed, and the correlation values cos α and sin α of the in-phase component are extracted.
Therefore, by inputting these to the determiner 27, the transmission-side in-phase component is demodulated. Similarly, the outputs r _I and r _Q from the baseband converters 22 and 24 are input to the spreading code PN2 correlators 26-1 and 26-2, respectively, and are correlated with the spreading code PN2 synchronized with the received signal. . Then, since the spreading code PN1 and the spreading code PN2 have a small orthogonal or cross-correlation, the in-phase component of the transmission signal is suppressed from the outputs from the correlators 26-1 and 26-2, and the correlation value of the orthogonal component cos
α and sin α are extracted. Therefore, by inputting these to the determiner 28, the transmitting side orthogonal component is demodulated.

Next, an embodiment in which the present invention is multiplexed with a plurality of orthogonal codes for both the in-phase component and the quadrature component will be described. 4 and 5 are schematic configuration diagrams of the third transmitting unit and the receiving unit, respectively.

In FIG. 4, n out of n + m parallel data
The data # I1 to #In are spread modulators 41-1 to 4-1, respectively.
1-n, spread modulation is performed by PN _{1 to} PN _n out of _{n + m} spread codes PN _{1 to} PN n + m output from the code generator 46, and added by the first adder 43. It The remaining m pieces of data # Q1 to #Qm are spread modulators 42-1 to 42-m, respectively, and m pieces of spread codes PN _{n + 1} output from the code generator 46.
~ PNn _{+ m is} spread-modulated and added by the second adder 44. Output of first adder 43 and second adder 44
The output of is input to the quadrature modulator 45, is modulated by the carriers orthogonal to each other, and is then synthesized. Quadrature modulator 45
The signal output from is subjected to processing such as amplification, filtering, and frequency conversion as necessary, and is transmitted.

In FIG. 5, the received signal r (t) is subjected to processing such as amplification, filtering and frequency conversion as necessary, and then branched, and a part of the received signal is input to the carrier regeneration circuit 51, The carrier is extracted and output. A part of the received signal is input to the synchronizing circuit 49, and the received signal and the spread code generated by the code generator 59 are clock-synchronized and code-synchronized. Since the synchronizing circuit 49 has been described in the first embodiment, its explanation is omitted here. Further, a part of the received signal is further branched into two, one of which is input to the first baseband conversion circuit 52 together with the carrier output from the carrier reproduction circuit 51, and the baseband signal r _I (t) of the in-phase component is extracted. Be done. On the other hand, the carrier output from the carrier reproduction circuit 51 is input to the second baseband conversion circuit 54 together with the signal obtained by 90-degree phase shifting by the 90-degree phase shifter 53, and the baseband signal r _Q (t) of the orthogonal component is input. Taken out. The baseband signal r _I (t) of the in-phase component is further branched into n, and n correlators 55-1 to
55-n performs correlation calculation with _n spread codes PN _{1 to} PN n of _{n + m} spread codes PN _{1 to} PN n + m output from the code generator 59, and the correlation Judge 57-1 based on the result
Data demodulation is performed at ~ 57-n. The baseband signal r _Q (t) of the orthogonal component has m spreading codes P out of the spreading codes output from the code generator 59 in the m correlators 56-1 to 56-m.
Correlation calculation with N _{n + 1 to} PN _{n + m} is performed, and data is demodulated by the decision devices 58-1 to 58-m from the correlation result.

In this embodiment, the n + m spreading codes are
It is desirable to be orthogonal, but a code set having a very small non-zero cross-correlation value may be used. Further, spreading codes PN _{1 to} PN _n for in-phase channels are orthogonal to each other, or
Small cross-correlation value, orthogonal channel spreading code PN _{n + 1 to} P
If N _{n + m} is orthogonal or the cross-correlation value is small, the spreading codes for in-phase channels PN _{1 to} PN _n and the spreading code for orthogonal channels
The cross-correlation values of PN _{n + 1 to} PN _{n + m} may be relatively large. Further, m = n may be used.

Further, in the embodiment, n + m pieces of parallel data are transmitted, but by providing a serial-parallel converter on the transmitting side and a parallel-serial converter on the receiving side, high-speed data transmission becomes possible. .

Next, the case where the carrier is not reproduced in the receiving section will be described. The transmitting unit is the same as in FIG. Figure 7
Is a fourth spread spectrum communication device embodying the present invention.
3 is a block diagram of a receiving unit of FIG. 7, the same parts as those in FIG. 5 are designated by the same reference numerals. This receiver is
An oscillator 71 having a frequency substantially equal to an intermediate frequency obtained by frequency-converting a transmission frequency or a reception signal without performing carrier reproduction.
The output is converted into a quasi-baseband signal and demodulated.

In FIG. 7, the output signal from the oscillator 71 is substantially equal in frequency to the received signal but not in phase, so that the outputs r _I and r _Q from the baseband converters 52 and 54 are the same.
Is r _I = t _I cos α + t _Q sin α rQ =-t _I sin α + t _Q cos α. Here, t _I and t _Q are the in-phase component and the quadrature component of the transmission signal, and α is the phase difference between the output of the oscillator 71 and the reception signal.

The outputs r _I and r _Q from the baseband converters 52 and 54 are respectively used as a correlator 55-1 for spreading code PN1.
Spread code input to 1, 55-1-2 and synchronized with the received signal
Correlate with PN1. Then, spreading code PN ₁ and spreading code PN ₂
~ PN _{n + m} has little orthogonality or cross-correlation, so the output from the correlators 55-1-1 and 55-1-2 suppresses the quadrature component of the transmitted signal, and further spreads the other in-phase components.
The components spread-modulated by PN _{2 to} PN _n are suppressed, and cos α of the correlation value of the components spread-modulated by spreading code PN ₁ and
sin α is taken out. Therefore, these are determined by the determiner 5
By inputting to 7-1, transmission data # I1 is demodulated. Similarly, other parallel data is also demodulated.

Although the synchronizing circuit operates with the signal before being converted into the baseband band, it may be configured to operate with the signal in the baseband band.

Further, instead of associating transmission data with one spreading code for one bit, the present invention can also be used in a so-called parallel combination system in which a spreading code set is associated with a plurality of data. .

[0030]

As described above, according to the present invention,
The in-phase channel (Ich) and the quadrature channel (Qch) are configured to be spread-modulated using different spreading codes, and the spreading codes used in each channel are code with small cross-correlation so that other The influence of the channel signal is reduced and the error rate characteristic is improved. In addition, the shift of the orthogonal axis and the phase of the reproduction carrier to achieve the desired error rate
The permissible range for the frequency shift is widened, the axis shift correction circuit is not required, and the phase / frequency correction circuit is not required or can be simplified, so that the device can be downsized. Furthermore, an expensive highly stable oscillator, a highly accurate quadrature modulator, or the like can be replaced with an inexpensive and less accurate component, and the cost can be reduced.

Further, demodulation can be performed without waiting until the phase / frequency of the reproduced carrier is locked with high accuracy,
Overhead can be shortened and throughput can be increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first transmission section of a spread spectrum communication apparatus of the present invention.

FIG. 2 is a block diagram showing a first receiving section of the spread spectrum communication apparatus of the present invention.

FIG. 3 is a block diagram showing a second receiving section of the spread spectrum communication apparatus of the present invention.

FIG. 4 is a block diagram showing a third transmitting section of the spread spectrum communication apparatus of the present invention.

FIG. 5 is a block diagram showing a third receiving section of the spread spectrum communication apparatus of the present invention.

FIG. 6 is a diagram showing an example of cross-correlation characteristics.

FIG. 7 is a block diagram showing a receiving section of the spread spectrum communication apparatus of the present invention.

FIG. 8 is a block diagram showing a transmitter of a conventional spread spectrum communication device.

FIG. 9 is a block diagram showing a receiving unit of a conventional spread spectrum communication device.

FIG. 10 is a block diagram showing a transmitter of a conventional spread spectrum communication device.

[Explanation of symbols]

 11, 12 Spreading modulator 13 Quadrature modulator 21 Carrier regeneration circuit 22, 24 Baseband converter 23 90 degree phase shifter 25, 26 Correlator 27, 28 Judgmenter 29 Synchronization circuit 30 Code generator

Claims (14)

[Claims] 1. N spread modulators that perform spread modulation with each of N spread codes (N is an integer of 2 or more), and n1 (0 <n1 <N) outputs of the N spread modulators. ), And a first modulator that modulates the first carrier wave, and outputs (Nn
1) A second modulator that modulates a second carrier wave having a phase different from that of the first carrier wave by the number of outputs, and a combiner that combines the first modulator output and the second modulator output A spread spectrum communication device comprising: 2. A first spread-modulating with a first spreading code.
Spread modulator, a second spread modulator that performs spread modulation with a second spread code, a first modulator that modulates a first carrier wave with the first spread modulator output, and a second spread modulator Second modulator that modulates a second carrier having a phase different from that of the first carrier by the output of the spread modulator, and a combiner that combines the first modulator output and the second modulator output. A spread spectrum communication device comprising: 3. The spread spectrum communication apparatus according to claim 2, wherein a cross-correlation between the first spread code and the second spread code is small. 4. The spread spectrum communication device according to claim 2, wherein the first spreading code and the second spreading code are orthogonal codes. 5. N spread modulators that perform spread modulation with each of N spread codes (N is an integer of 4 or more), and n1 (1 <n1 <N of the N spread modulator outputs). -1)
Of the N spread modulator outputs other than the above n1 (Nn
1) a second adder for adding the outputs, a first modulator for modulating the first carrier wave by the first adder output, and a first modulator for the second adder output Spread spectrum communication characterized by comprising: a second modulator for modulating a second carrier having a phase different from that of the carrier wave; and a combiner for combining the output of the first modulator and the output of the second modulator. apparatus. 6. The spread spectrum communication device according to claim 1, wherein the N spread codes are codes having a small cross-correlation with each other. 7. The spread spectrum communication device according to claim 1, wherein the N spread codes are codes orthogonal to each other. 8. The method according to claim 1, wherein n1 of the N spreading codes are codes orthogonal to each other and the remaining (N-n1) are codes orthogonal to each other. Item 5. The spread spectrum communication device according to Item 5. 9. The spread spectrum communication device according to claim 1, wherein the first carrier and the second carrier are carriers that are substantially orthogonal to each other. 10. A correlator for correlating each of the N spread codes with a received signal, and a determiner for determining data from an output of the correlator are further provided. A spread spectrum communication device according to any one of the above. 11. A spread spectrum communication method in which two substantially orthogonal channels having different carrier phases (an in-phase channel and a quadrature channel) are combined and transmitted, wherein the two channels are spread spectrum modulated by different spread codes. Spread spectrum communication method characterized by. 12. The spread spectrum communication method according to claim 11, wherein the spreading code used in one of the two channels is a code having a small cross-correlation with the spreading code used in the other channel. . 13. The spread spectrum communication method according to claim 11, wherein the spreading code used in one of the two channels is a code orthogonal to the spreading code used in the other channel. 14. A spread spectrum communication method for multiplexing and communicating signals spread-spectrum modulated by N (N> 1) orthogonal spread codes, wherein n1 (0 <n1 < N) is the first set of data, and the remaining (N-n1) pieces is the second set of data, the first set of data is spread-modulated with n1 spreading codes, and the second set of data is the above N pieces. Of the orthogonal spreading codes of (N-n1) that are not used for spreading modulation of the data of the first set are spread-modulated, and the signals of the first set of data and the second set are spread-modulated. A spread spectrum communication method characterized in that signals obtained by spread-modulating data are modulated by carriers that are substantially orthogonal to each other, and then combined and transmitted.