JPH06104864A - Direct spread spectrum communication equipment - Google Patents

Abstract

PURPOSE:To obtain the DS-SS (direct spread spectrum) communication equipment in which inter-channel interference is less. CONSTITUTION:A transmitter 1 is provided with an FIR (finite impulse response) filter 16 frequency-converting a spectrum of a spread signal at a base band and a D/A converter means 17 converting an output of the FIR filter 16 into an analog signal, and a receiver 2 is provided with an A/D converter means 27 converting a mixer output into a digital signal and a Kalman filter 28 to which a constant used for the FIR filter is set and receiving a signal from the A/D converter means 27. Furthermore, the filter coefficient of the FIR filter 16 is set identical for transmitters of a same group and a filter coefficient of the FIR filter 16 of a desired group is set for the filter coefficient of the Kalman filter 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct spread spectrum communication apparatus (hereinafter referred to as DS-SS communication apparatus) which spreads and spreads an information signal by using a pseudo noise (hereinafter referred to as PN) signal to perform spread modulation. ) Is related to.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional DS-SS communication device. In the figure, ₁₁ to 1 _n are transmitters in the DS-SS communication device, and 2 is a DS-SS communication device.
It is a receiver in the SS communication device.

In each of the transmitters 1 ₁ to 1 _n , 1
1 is the information signal d _i (t) (i = 1, 2, ..., N)
Spread using the N signal to obtain the spread signal S _i (t) (i = 1,
2, ..., N), and a PN generator (pseudo noise generator) 12 for generating a PN signal to be supplied to the multiplier 11. Reference numeral 13 is a mixer that RF-modulates a carrier wave with the spread signal S _i (t) output from the multiplication means 11, and 14 is a carrier wave generation means that generates a carrier wave to be supplied to the mixer 13. 15 is a mixer 13
It is an antenna that radiates an RF-modulated signal in space.

In the receiver 2, 21 is an antenna for receiving a signal radiated into space from the antenna 15 of each transmitter 1, and 22 is a signal received by this antenna in the transmitters 1 ₁ to 1 _n . Mixer for frequency conversion using a carrier wave of the same frequency as that generated by the carrier wave generation means 14 of
Reference numeral 23 is a carrier wave generating means for generating a carrier wave to be supplied to the mixer 22. 24 is a mixer 22 using a PN signal
Is a multiplication means for despreading the output signal S (t) of
Is a PN that generates a PN signal to be supplied to the multiplication means 24.
It is a generation means (pseudo noise generation device). Reference numeral 26 is an integrating means for integrating the output signal of the multiplying means 24 for the time of one cycle of the PN signal.

Next, the operation will be described. First, the operation of the transmitters 1 ₁ to 1 _n will be described. Taking the transmitter 1 ₁ as an example, the information signal d ₁ (t) is spread by the PN signal generated by the PN generating means 12 and the multiplying means 11 into a spread signal S ₁ (t). This spread signal S
₁ (t) is RF-modulated in the mixer 13 by the carrier wave generated by the carrier wave generation means 14 and sent out from the antenna 15 to the space. Also, the PN of each transmitter 1 ₁ to 1 _n
The generating means 12 generate different PN signals, and the carrier wave generating means 14 all generate carrier waves of the same frequency.

Next, the operation of the receiver 2 will be described. Now
Taking the case of demodulating the information signal d ₁ (t) of the transmitter 1 ₁ as an example, the signal received by the antenna 21 is frequency-converted by the mixer 22 by the carrier wave generated by the carrier wave generator 23 and multiplied. Sent to the means 24. Here, the output signal S (t) of the mixer is the sum of the spread signals S _i (t) in each of the transmitters 1 ₁ to 1 _n , and can be expressed by the following equation. The underline in the formula indicates that it is an estimated value.

[0007]

[Equation 1]

On the other hand, from the PN generating means 25, the transmitter that the receiver 2 desires to demodulate (transmitter 1 _{1 in} this case).
The same PN signal as the PN generating means 12 in the multiplying means 24
And the multiplication means 24 outputs the signal S from the mixer 22.
(T) is multiplied by the PN signal to perform despreading. The despread signal is sent to the integrating means 26 and integrated for the time corresponding to one cycle of the PN signal, and the information signal d of the transmitter 1 _1
1 (t) is demodulated.

Documents describing techniques related to such a conventional DS-SS communication device are, for example, Japanese Patent Laid-Open Nos. 61-174841 and 61-1748.
42, JP 61-198834, JP 61-198837, and JP 61-198838.
JP-A-62-285533, JP-A-3-
There are 80642 and JP-A-3-236644.

[0010]

Since the conventional DS-SS communication apparatus is constructed as described above, the channel identification depends only on the level difference between the autocorrelation value and the cross-correlation value of the PN signal. However, since the cross-correlation value of the PN signal never becomes 0, there is a problem that inter-channel interference is large compared to the spread spectrum rate.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a DS-SS communication device with reduced inter-channel interference.

[0012]

According to a first aspect of the present invention, a DS-SS communication device includes a finite impulse response filter (hereinafter, referred to as FIR filter) that causes a transmitter to frequency-convert a spectrum of a spread signal in a base band. And this F
A digital / analog conversion means (hereinafter referred to as D / A conversion means) for converting the output of the IR filter into an analog signal is provided, and the receiver is subjected to frequency conversion to convert the output of the mixer into an analog / digital conversion. Means (hereinafter referred to as A / D conversion means) and a Kalman filter to which a constant used in the FIR filter is set and a signal from the A / D conversion means is input are provided.

The DS-according to the invention of claim 2
In the SS communication device, the filter coefficients of the FIR filters of the transmitters divided into groups are set to be the same in the same group.

The DS-according to the invention of claim 3
The SS communication apparatus uses a Kalman filter in which only the filter coefficient set in the FIR filter of the group to which the receiver desiring demodulation belongs is set.

The DS-according to the invention of claim 4
The SS communication device uses a Kalman filter in which the filter coefficients set in the FIR filters of all groups are set.

Further, the DS-according to the invention of claim 5
The SS communication device has the filter coefficient set in the FIR filter of the group to which the transmitter that the receiver desires to demodulate and the filter coefficient set in the FIR filter of the group to which the transmitter with large interference power belongs. It uses the set Kalman filter.

[0017]

The FIR filter according to the first aspect of the present invention makes it possible to reduce inter-channel interference by converting the spectrum of the spread signal so that the Kalman filter used in the receiver can separate the signals.

Further, the FI in the invention according to claim 2
In the R filter, the throughput of the Kalman filter is reduced by setting the same filter coefficient in the transmitters in the same group.

Further, in the Kalman filter according to the third aspect of the present invention, only the filter coefficient set in the FIR filter of the predetermined group is set as the filter coefficient to reduce the circuit scale and simplify the Kalman filter calculation. To do.

Further, the Kalman filter according to the invention described in claim 4 improves the signal estimation accuracy by setting the filter coefficient set in the FIR filters of all groups as the filter coefficient.

Further, the Kalman filter according to the invention of claim 5 has, as its filter coefficient, the filter coefficient set in the FIR filter of the predetermined group and the filter coefficient set in the FIR filter of the group having a large interference power. By setting the signal estimation accuracy to some extent, the circuit scale can be reduced and the Kalman filter calculation can be simplified.

[0022]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. In FIG. 1, 1 ₁ to 1 _n are transmitters, 2 are receivers, 11 and 24 are multiplication means, 12 and 25 are PN generation means, 13 and 22 are mixers, 14 and 23 are carrier wave generation means, and 15 and 21. Is an antenna, and 26 is an integrating means, which is the same as or equivalent to those of the conventional one denoted by the same reference numeral in FIG.

In the transmitters 1 ₁ to 1 _n , 16
Is an FIR filter for frequency-converting the spectrum of the spread signal S _i (t) output from the multiplying means 11 in the baseband, and 17 is a D for converting the output of the FIR filter 16 into an analog signal and inputting it to the mixer 13. / A conversion means (digital / analog conversion means). further,
In the receiver 2, 27 is an A / D conversion means (analog / digital conversion means) for converting the observed signal y (t) obtained by frequency-converting the reception signal in the mixer 22 into a digital signal, and 28 is The constants used in the FIR filters 16 of the transmitters 1 ₁ to 1 _n are set, the digitized signal is processed by the A / D conversion means 27 to generate the sum of transmitter outputs, and the multiplication means 24 is provided. It is a Kalman filter to input.

Next, the operation will be described. First, the operation of the transmitters 1 ₁ to 1 _n will be described. Taking the transmitter 1 ₁ as an example, the information signal d ₁ (t) ε {1, −1} is multiplied by the PN signal ε {1, −1} generated by the PN generation means 12 and the multiplication means 11. It is multiplied and spread to become a spread signal S ₁ (t). The symbol ε is used as a mathematical symbol indicating that the left side is included in the right side. For example, aεA indicates that a is included in A. This spread signal S ₁
The (t) is processed by the FIR filter 16. The FIR filter 16 divides the transmitters 1 ₁ to 1 _n into several groups A to _N in advance, and assigns the FIR filters 16 having the same filter coefficient to the transmitters belonging to the same group. Now, transmitter 1 ₁ belongs to group A,
The FIR filters 16 of group A all have the same filter coefficient. The maximum number of group divisions is n when there are n transmitters. In this case, each transmitter ₁ 1 to 1
All different FIR filters 16 will be assigned to _n . After that, the signal is converted into analog by the processing of the D / A conversion means 17 and sent to the mixer 13, RF-converted by the mixer 13 and sent from the antenna 15.

Next, the operation of the receiver 2 will be described. Now, taking the case of demodulating the information signal d ₁ (t) of the transmitter 1 ₁ as an example, the signal received by the antenna 21 is frequency-converted by the mixer 22 and becomes the observation signal y (t). After that, it is digitized by the A / D conversion means 27 and input to the Kalman filter 28 for processing. From the Kalman filter 28, the transmitters 1 ₁ , 1 belonging to the group A are
The sum u _A (t) of the outputs of ₂ is output.

[0026]

[Equation 2]

This signal u _A (t) is multiplied by the PN signal << {1, -1} generated by the PN generating means 25 in the multiplying means 2
4 is despread, and further, in the integrating means 26, P
The information signal d ₁ (t) of the transmitter 1 ₁ is estimated by integrating for one cycle of the N signal.

Next, the FIR filter will be described in detail. The transmitter 1 _1, 1 FIR filter 16 used in the _second group A in FIG. 1, the order is k, the filter coefficients are assumed to be given by the following equation.

[0029]

[Equation 3]

In this case, the spectral characteristics realized by each FIR filter 16 are as shown in FIG.
In the figure, f indicates a frequency, T indicates one cycle time of the PN chip clock, and A to N attached to each curve correspond to each of the groups A to N. Where each FIR
The conditions required for the filter 16 are that there is no change in the power before and after the signal passes and that the Kalman filter 28 can perform the signal estimation operation.
It is required that the peak portions of the spectral characteristics of the R filter 16 have different frequencies. The filter coefficient h _i ^(.) That satisfies these conditions must be obtained by trial and error.

In the receiver 2 used in FIG. 1, only the filter coefficients of the FIR filter 16 of group 1 are known, and the FIR filters 16 of groups B to N are known.
Assuming there is no foresight information about the filter coefficients of
The generation mechanism for the observed signal y (t) can be expressed using the following equation. In the equation, <> indicates that it is a vector quantity.

[0032]

[Equation 4]

However, each variable can be expressed by the following equation.

[0034]

[Equation 5]

The vector quantity (x) in the equation (9)
(T) represents a k-th order state variable vector inside the FIR filter 16 of the transmitter 1 _i . Also, the formula (1
The symbol ≤ in 1) is used as a mathematical symbol indicating that the left side is not included in the right side.
A indicates that i is not included in A.

F _A in the above equations (6) to (8),
By setting G _A and H _A as F, G, and H in the Kalman filter shown in FIG. 3, <X _A > (t) can be estimated. Note that K (t) in FIG. 3 indicates the Kalman gain. Also, from equations (4) and (5), the vector <X _A >
When the first component of (t) is X _{A, 1} (t), the following equation holds, and therefore the output sum of the transmitters 1 ₁ and 1 ₂ belonging to the group A can be estimated.

X _{A, 1} (t) = u _A (t−1) ‥‥‥‥‥‥‥‥‥‥‥‥ (12)

As described above, since the signal generation information other than the group A is not used in the estimation in the first embodiment, the signal estimation ability is lower than that of the method in the second embodiment described below. The circuit scale is small,
Moreover, the computer speed used for the Kalman filter calculation is not so required. The Kalman filter 28 is set to P
A series of filter calculations must be completed within one N chip clock period.

Example 2. In the first embodiment described above, only the filter coefficient set in the FIR filter 16 of the predetermined group is set as the filter coefficient of the Kalman filter 28, but the filter coefficient set in the FIR filter 16 of all groups is set. It may be set. In that case, the configuration of the DS-SS communication device is
The operation is the same as that shown in the block diagram of FIG. 1, but the operation of the Kalman filter 28 is different. That is, in the second embodiment, each FIR filter 16 of the groups A to N is
The case where all the filter coefficients of are known is handled. In this case, the generation mechanism of the observation signal y (t) can be written by the following equation.

[0040]

[Equation 6]

Here, the meanings of the variables in the equations (13) and (14) are as follows.

[0042]

[Equation 7]

The following matrix in the above equation (13), [G _A , G _B , ..., G _N ] and [H _A , H _B ,
.., H _N ] are newly designated as F, G, and H in FIG.
By setting the Kalman filter 28 shown in FIG. 1, it becomes possible to estimate the total sum u _A (t) of the transmitter outputs.

[0044]

[Equation 8]

Although the circuit scale in this case is larger than that in the first embodiment, the estimation accuracy is improved by using the information about the filter coefficients of the FIR filters 16 of all the groups for signal estimation.

Example 3. In each of the above embodiments, only the filter coefficient set in the FIR filter 16 of the predetermined group as the filter coefficient of the Kalman filter 28,
Alternatively, the case where the filter coefficients set in the FIR filters 16 of all groups are set has been described, but the filter coefficients set in the FIR filters 16 of a predetermined group and the FIR filters 16 of a group having a large interference power are set.
You may make it set the filter coefficient set to. In this way, only for the predetermined group to which the transmitter desiring demodulation belongs and the group with large interference power,
By performing the estimation by the Kalman filter 28,
Although the signal estimation capability is slightly reduced as compared with the case of the second embodiment, the circuit scale can be reduced and effective signal estimation can be performed. In this case also, the configuration of the DS-SS communication device is
It is the same as that shown in the block diagram of FIG.

[0047]

As described above, according to the invention described in claim 1, the FI for converting the spectrum of the spread signal so that the signal can be separated by the Kalman filter used in the receiver.
Since the configuration is such that the R filter is added, there is an effect that a DS-SS communication device capable of reducing interference between channels can be obtained.

Further, according to the invention described in claim 2, since the transmitters are divided into groups and the filter coefficients of the FIR filters in the same group are set to be the same, the throughput of the Kalman filter can be reduced. effective.

According to the third aspect of the invention, since only the filter coefficient of the FIR filter of the predetermined group is set as the filter coefficient of the Kalman filter, the circuit scale can be reduced and the Kalman filter operation can be performed. Can be simplified.

According to the fourth aspect of the invention, the FIs of all groups are used as the filter coefficients of the Kalman filter.
Since the filter coefficient of the R filter is set, the signal estimation accuracy can be improved.

According to the fifth aspect of the invention, the filter coefficient of the FIR filter of the predetermined group and the filter coefficient of the FIR filter of the large interference power are set as the filter coefficient of the Kalman filter. Therefore, it is possible to reduce the circuit size and simplify the Kalman filter calculation while maintaining a certain level of signal estimation capability, and it is possible to perform effective signal estimation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a spectrum of an FIR filter in the above embodiment.

FIG. 3 is a block diagram showing a Kalman filter in the above embodiment.

FIG. 4 is a block diagram showing a conventional DS-SS communication device.

[Explanation of symbols]

1 ₁ to 1 _N transmitter 2 receiver 11 multiplication means 12 PN generation means (pseudo noise generation means) 13 mixer 14 carrier wave generation means 16 FIR filter (finite impulse response filter) 17 D / A conversion means (digital / analog conversion means) ) 22 mixer 23 carrier wave generation means 24 multiplication means 25 PN generation means (pseudo noise generation means) 26 integration means 27 A / D conversion means (analog / digital conversion means) 28 Kalman filter

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

[0034]

[Equation 5]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction content]

The vector quantity (x) in the equation (9)
(T) represents a k-th order state variable vector inside the FIR filter 16 of the transmitter 1 _i . Also, the formula (1
The symbol < in 1) is used as a mathematical symbol indicating that the left side is not included in the right side. For example, i <
A indicates that i is not included in A.

Claims (5)

[Claims] 1. A pseudo noise generating means for generating a pseudo noise signal, a multiplying means for spreading an information signal using the pseudo noise signal generated by the pseudo noise generating means, and a spreading means for spreading the information signal. A finite impulse response filter for frequency-converting the spectrum of a spread signal in a base band, a digital / analog conversion means for converting the output of the finite impulse response filter into an analog signal, a carrier wave generating means for generating a carrier wave, and the digital / analog A transmitter having a mixer for RF modulating the carrier wave at the output of the converting means; a carrier wave generating means for generating a carrier wave having the same frequency as the carrier wave generating means of the transmitter; and a signal received from the transmitter. , A mixer for frequency conversion using the carrier wave from the carrier wave generation means, and a digital signal for the output of the mixer. Analog-digital conversion means for converting into a signal, a constant used in the finite impulse response filter is set, a Kalman filter to which the output of the analog-digital conversion means is given, pseudo noise generating means for generating a pseudo noise signal, Multiplying means for despreading the output of the Kalman filter using the pseudo noise signal generated by the pseudo noise generating means; and integrating means for integrating the output of the multiplying means for a period of one cycle of the pseudo noise signal. A direct spread spectrum communication device including a receiver including the. 2. A pseudo noise generating means for generating a pseudo noise signal, a multiplying means for spreading an information signal using the pseudo noise signal generated by the pseudo noise generating means, and a spreading means for spreading the information signal. A finite impulse response filter for frequency-converting the spectrum of a spread signal in a base band, a digital / analog conversion means for converting the output of the finite impulse response filter into an analog signal, a carrier wave generating means for generating a carrier wave, and the digital / analog A transmitter having a mixer for RF modulating the carrier wave at the output of the converting means; a carrier wave generating means for generating a carrier wave having the same frequency as the carrier wave generating means of the transmitter; and a signal received from the transmitter. , A mixer for frequency conversion using the carrier wave from the carrier wave generation means, and a digital signal for the output of the mixer. Analog-digital conversion means for converting into a signal, a constant used in the finite impulse response filter is set, a Kalman filter to which the output of the analog-digital conversion means is given, pseudo noise generating means for generating a pseudo noise signal, Multiplying means for despreading the output of the Kalman filter using the pseudo noise signal generated by the pseudo noise generating means; and integrating means for integrating the output of the multiplying means for a period of one cycle of the pseudo noise signal. In a direct spread spectrum communication apparatus including a receiver including, a plurality of the transmitters are prepared and grouped into a plurality of groups, and a filter coefficient of a finite impulse response filter of the transmitter is within the same group. Then, the direct spread spectrum communication device characterized in that they are set to be the same. 3. The Kalman filter used is one in which only the filter coefficient set in the finite impulse response filter of the group to which the receiver desiring demodulation belongs is set as the Kalman filter. Item 3. A direct spread spectrum communication device according to item 2. 4. The direct spread spectrum communication apparatus according to claim 2, wherein as the Kalman filter, one in which filter coefficients set in the finite impulse response filters of all groups are set is used. 5. As the Kalman filter, the filter coefficient set in the finite impulse response filter of the group to which the receiver that the receiver desires to demodulate and the finite of the group to which the transmitter with large interference power belongs 3. The direct spread spectrum communication apparatus according to claim 2, wherein an impulse response filter having a filter coefficient set therein is used.