JP2000022593A - Spread spectrum transmission and reception system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spread spectrum transmission/reception system capable of eliminating the need of a PN synchronization circuit on a reception side and excellently transmitting and receiving data even for low band disturbance. SOLUTION: In this spread spectrum transmission/reception system, a transmission unit is provided with a data generation means (101), a PN signal generation means (102), a multiplier (103), a delay means (104), a low band reinforcing means (105), an adder (106) and a transmission means (107) and a reception unit is provided with a reception means (201), a delay means (202), a low band attenuation means (203), a multiplier (204) and a data reproduction means (205). Then, PN signals to which delay and low band reinforcing processings are executed are added to spread signals by the product of data and the PN signals and sent out. On the reception side, signals in which they are delayed by the same time and the signals to which low band attenuation processing is executed are multiplied and inverse spread processing is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum system used for data transmission in a power line carrier system, wireless communication, wireless control system, and the like.

[0002]

2. Description of the Related Art Conventionally, as such a spread spectrum system, a PN signal (102) used for spread spectrum modulation on a transmission side is shown in FIG.
Apart from 1), a method in which a reference PN signal (2021) is newly generated on the receiving side and despreading processing of a spread spectrum signal is performed using the reference PN signal (2021) has become mainstream.

In such a conventional system, a PN synchronization circuit (300) is used to ensure synchronization between a PN signal (1021) and a reference PN signal (2021). An acquisition circuit (301) acquires a synchronization point based on the autocorrelation characteristic of the PN signal (1021), and then maintains a synchronization relationship by a synchronization maintaining circuit (302) using a delay lock loop or the like. , Complicated processing is being performed.

FIG. 2 is a block diagram showing the principle of a second conventional example. In a transmission unit (1), a PN signal (1
021) by the delay means (104) is used as a reference PN signal (2021).
03), which is superimposed on the spread spectrum signal obtained at the output of the receiving unit (2) and transmitted.
01) is divided into two paths, and one of the paths is divided into delay means (20) for receiving a delay time equal to that of the delay means (104).
After being delayed by 2) and the other directly by the multiplier (2
04), the spread spectrum signal delayed by the same amount is despread by the reference PN signal (2021) included in the direct signal (2022).

[0005] In this process, the data signal is expressed as d (t), PN
When a signal is represented by p (t), a PN delay time is represented by τ, a disturbance signal mixed in the transmission path is represented by G (t), and a despread signal is represented by c (t), which is expressed by the following equation 1. It can be seen from the first term that data can be extracted. (Because p (t−τ) * p (t−τ) = 1) c (t) = {d (t) * p (t) + p (t−τ) + G (t)} * Δd ( t−τ) * p (t−τ) + p (t−2 * τ) + G (t−τ) ∴ c (t) = d (t−τ) * p (t−τ) * P (t− τ) + p (t−τ) * p (t−2 * τ) + d (t) * p (t) * p (t−2 * τ) + d (t) * d (t−τ) * p (t ) * P (t−τ) + G (t) * p (t−2 * τ) + G (t−τ) * p (t−τ) + G (t) * d (t−τ) * p (t− τ) + G (t−τ) * d (t) * p (t) + G (t) * G (t−τ) (1)

[0006]

SUMMARY OF THE INVENTION In data transmission,
In recent years, spread spectrum systems are rapidly gaining traction, but their application is concentrated on high-end fields such as multimedia transmission systems and mobile phone systems that require high-speed and advanced CDMA. It is a reality. However, on the other hand, there is an increasing demand for data transmission systems in general-purpose fields that are relatively low-end, such as those in various wireless control systems, wireless transmission of voice and security information, and power line transmission systems. At present, there is a strong demand for an inexpensive and versatile spread spectrum system.

[0007] On the other hand, FIG.
In the conventional system shown in (1), as described above, the use of a complicated PN synchronization circuit is an essential condition, and the convolver and the like incorporated therein must be unique to the system. Had become something.

On the other hand, in the conventional example shown in FIG. 2, in the signal after the despreading processing, as shown in Equation 1, in addition to the data term of the first term, the second and subsequent terms are all noise terms. Included. Of these, the second, third and fifth terms are P
It is an N component or a spread spectrum component of a data signal or a disturbance signal. Although it has relatively little harm, it is particularly the last term that a low frequency component sufficiently lower than 1 / τ is substantially square-detected. , DC components and noise components mixed in the data band. The fourth and sixth terms, though diffused, do the same, albeit slightly.

As described above, in the conventional example shown in FIG. 2, there is a problem that the transmission quality is impaired by these noise components. In particular, due to its low cost and easiness, the baseband processing type which is frequently used in the general field is used. In the system, since most of the disturbance components are low-frequency components near the data band, this problem has been a fatal drawback.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a very simple structure, is inexpensive, versatile, and has a baseband without using a complicated PN synchronization circuit. It is an object of the present invention to provide a spread spectrum transmission / reception system capable of obtaining good transmission quality even in a processing type.

[0011]

In order to solve the above-mentioned problem, according to the first aspect of the present invention, the transmitting unit comprises a data generating means (101), a PN code generating means (102), (103) and delay means (104) having a delay time that is an integral multiple of the chip time of the PN code.
And a low frequency band enhancing means (105) for enhancing a low frequency region including a basic spectrum bandwidth of data; an adder (106); and a transmitting means (107), and a data generating means (101). And the output of the PN code generating means (102) are added to a multiplier (103) to extract a spread spectrum signal from the output. Further, the spread spectrum signal and the PN code generating means (1) are further added.
02) through a delay means (104) and a low-frequency enhancement means (105), and a signal obtained by adding the output signal to an adder (106).
7), the receiving unit comprising: a receiving means (201) for receiving a signal transmitted from the transmitting unit; and a delay means (202) having a delay time equal to the delay means (104). ), A low-frequency attenuating means (203) having a characteristic opposite to that of the low-frequency enhancing means (105), a multiplier (204), and a data reproducing means (205). The output is branched into two, one of which is passed through a delay means (202) and the other is passed through a low-frequency attenuating means (203), and both are added to a multiplier (204), and the output is added to the output. A despread signal is extracted, and a data reproducing unit (205) extracts an intended data signal from the despread signal.

According to the second aspect of the present invention, the transmitting unit includes the data generating means (101), the PN code generating means (102), the multiplier (103), and an integral multiple of the chip time of the PN code. Delay means (10
4), a low frequency band enhancing means (105) for enhancing a low frequency region including a basic spectrum bandwidth of data, an adder (106), and a transmitting means (107), and
The output of the data generating means (101) and the output of the PN code generating means (102) are added to a multiplier (103) so as to extract a spread spectrum signal from the output thereof. PN code generation means (1
02) and a signal obtained by passing a part of the output through the delay means (104) to the adder (106), and the output signal is passed through the low-frequency enhancement means (105) to be sent out by the transmission means ( 107), the receiving unit comprising: a receiving means (201) for receiving a signal transmitted from the transmitting unit; and a delay means (20) having a delay time equal to the delay means (104).
2) a low-frequency attenuating means (203) having characteristics opposite to those of the low-frequency enhancing means (105); a multiplier (204); and a data reproducing means (205), and a receiving means (8).
After passing through the low-frequency attenuating means (203), the signal is branched into two, one of which is passed through the delay means (202), and the other is left as it is, and both of them are multiplier (204).
In addition to the above, a despread signal is extracted from the output, and a target data signal is extracted from the despread signal by the data reproducing means (205).

According to the third aspect of the present invention, the transmitting unit includes a data generating means (101), a PN code generating means (102), a multiplier (103), and a delay of an integral multiple of a chip time of the PN code. Extension means with time (104)
, An adder (106), and a sending means (107). The output of the data generating means (101) and the output of the PN code generating means (102) are added to the multiplier (103). A spread spectrum signal is extracted from the output, and the spread spectrum signal is added to a signal obtained by passing a part of the output of the PN code generation means (102) through the delay means (104). In addition to the transmitter (106), the output signal is transmitted by the transmitting means (107), and the receiving unit receives the signal transmitted from the transmitting unit (20).
1), a delay means (202) having a delay time equal to the delay means (104), a low-frequency attenuator (203) for attenuating a low frequency region including the basic spectrum bandwidth of data, and a multiplier ( 204) and a data reproducing means (205). The output of the receiving means (8) is divided into two, one of which is passed through a delay means (202), and the other is provided with a low-frequency attenuation means ( 203), the two are added to a multiplier (204), a despread signal is extracted from the output thereof, and a target data signal is extracted from the despread signal by a data reproducing means (205). Low-frequency attenuation means (203)
Has two attenuation frequencies f1 and f2 (f
1 <f2), and the attenuation amount =
0 dB and m in the frequency domain of f1 ≦ f ≦ f2.
It is characterized by having a second slope characteristic and further having such a characteristic that the attenuation becomes constant again in the frequency region of f <f1.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a block diagram showing the principle of an embodiment of the spread spectrum transmitting / receiving system according to the present invention. In the transmission unit (1), the data signal (data bit time: Tb) generated by the data generation means (101) is converted into a PN signal (chip time: Tc, code length) generated by the PN code generator (102). :
N), the data signal bandwidth (1 / Tb) is spread to the PN signal bandwidth (1 / Tc) by the spread spectrum modulation in the multiplier (103).

As the PN code, an M-sequence code, a Gold code, and the like are generally used. Here, the following description will be made taking an example in which the M-sequence code is used.

Part of the PN signal is a delay means (10) having a delay time that is an integral multiple of the chip time (n * Tc).
After being delayed by 4), the low-frequency enhancement including the data signal bandwidth (1 / Tb) is enhanced by the low-frequency enhancement means (105). FIG. 6 shows the low-frequency enhancement means (1).
05) and the characteristics of a low-frequency attenuating means (202) to be described later. FIG. 5A shows a data signal bandwidth (401) and a spread spectrum signal bandwidth (4).
FIG. 2C shows an example of the low-frequency enhancement characteristic (404) and the low-frequency attenuation characteristic (403). In this example, the low-frequency enhancement characteristics (404)
Has two corner frequencies f1 and f2, and f2 ≧ (1 / T
b) is set. The range of f1 ≦ f ≦ f2 is −m *
An mth-order slope having a characteristic of 6 dB / oct is used, and the value of f1 is determined by f2, m and the required low-frequency enhancement amount.

The amount of low-frequency enhancement here is the amount of suppression of harmful low-frequency noise, as will be described later. Therefore, it is desirable that the amount can be set as large as the system allows.

However, in general data transmission systems, high-frequency enhancement / attenuation (so-called pre-emphasis / de-emphasis) is used, but low-frequency enhancement / attenuation is used.
No attenuation is used. This is because the low-frequency enhancement of the area including the data signal bandwidth directly leads to an increase in the transmission level. Therefore, 40 dB
In order to obtain the low-frequency enhancement amount, the transmission level becomes 100 times.

On the other hand, in the present invention, by using the low-frequency enhancement means (105) which positively utilizes the properties of the PN code, the transmission level is not largely affected, and
It is possible to obtain a sufficiently large low-frequency enhancement amount. That is, since the spectrum component of the PN signal having the relationship of Tc = Tb / N does not have a low-frequency component less than (1 / Tb), if f2 is set near (1 / Tb), While securing a sufficiently large low-frequency enhancement amount, the increase in the transmission level can be suppressed to a small amount.

This situation will be described in more detail with reference to simulation analysis examples shown in FIGS. In addition,
The specifications here are as follows. Tb = 1.275 mSec N = 255 Tc = 5 uSec (Tb / N) f2 = 1569 Hz (2 / Tb) f1 = 156.9 Hz m = 2 From f2 and f1, m, low frequency enhancement amount = 40 dB FIG. Is the PN generated by the [8,6,4,3,2,1] feedback of the 8-stage shift register based on the above specifications.
One cycle (one code length) of the signal is shown. FIG. 12B shows a PN signal after the low-frequency enhancement processing is performed based on the above specifications, and corresponds to a reference PN signal (2021). . FIG. 11C shows a state in which the receiving side has been subjected to the low-frequency attenuation processing to return to the flat characteristic, and the reference signal (202)
2) It corresponds to the final reference PN signal included in 2).
(Actually, since the reference signal (2022) includes a spread spectrum signal, a disturbance signal, and the like at the same time, such a waveform does not appear.) Further, FIG. FIG. 4B is an enlarged view of the spectrum distribution of the PN signal shown in FIG.

As is apparent from FIG. 9, the spectrum distribution of the PN signal is treated as a substantially continuous spectrum having a main lobe bandwidth of (1 / Tc). This is a set of line spectra based on the spectrum, and it can be seen that there is no component less than (1 / Tb).

Therefore, according to the low-frequency enhancement processing based on the above-mentioned specifications, a low-frequency enhancement amount of 40 dB can be obtained.
As shown in FIG. 8B, the influence on the transmission level is suppressed to a small amount. The undulation components appearing in the figure are obtained by slightly amplifying the spectrum components of (1 / Tb) and (2 / Tb).

The PN signal enhanced in the low frequency band in this manner is converted into a reference PN signal (20) used for despreading on the receiving side.
As 21), the signal is superimposed on the above-mentioned spread spectrum signal (adder (106)) and transmitted by the transmitting means (107). Also in this case, the superimposition processing is enabled by the autocorrelation characteristic of the PN signal (code). That is, as shown in FIG. 7, the auto-correlation characteristic of the PN code shows that a sharp auto-correlation peak appears at intervals of the code length N, and if there is a phase difference of one chip or more, the auto-correlation = 0.
Have the property of becoming. Therefore, the reference PN signal delayed by n * Tc has no apparent correlation with the PN component included in the spread spectrum signal, and can coexist independently in one signal without interfering with each other. .

On the other hand, in the receiving unit (2), after the signal transmitted from the transmitting unit (1) is received by the receiving means (201), the output signal is divided into two paths. ), The reference PN signal is returned to the flat characteristic by the low-frequency attenuating means (203) having a characteristic as exemplified in the low-frequency attenuation characteristic (403), and at the same time, the low-frequency region such as a disturbance signal is attenuated. , The final reference signal (202
2) is gained. On the other hand, the phase of the spectrum-spread data signal component is passed through a delay means (202) having a delay time equal to that of the transmission means (104), and the phase of the reference PN signal in the reference signal (2022) is changed. After despreading the two by the multiplier (204), the data signal is finally extracted by the data reproducing means.

The despread signal obtained through this series of processes is represented by LB (t) for low-frequency enhancement and LA for low-frequency attenuation.
Expression (2) can be expressed by Expression 2 as Expression (t). c (t) = {LA (t) * d (t) * p (t) + p (t−τ) + LA (t) * G (t)} * Δd (t−τ) * p (t−τ) ) + LB (t) * p (t−2 * τ) + G (t−τ)｝ c (t) = d (t−τ) * p (t−τ) * P (t−τ) + LB (t ) * P (t−τ) * p (t−2 * τ) + d (t) * p (t) * p (t−2 * τ) + LA (t) * d (t) * d (t−τ ) * P (t) * p (t−τ) + G (t) * p (t−2 * τ) + G (t−τ) * p (t−τ) + LA (t) * τG (t) * d (t−τ) * p (t−τ) + G (t−τ) * d (t) * p (t)｝ + LA (t) * G (t) * G (t−τ) .... (Equation 2)

Looking at Equation 2, the data component of the first term is expressed by Equation 1.
It can be seen that the low-frequency attenuation characteristic LA (t) acts on the most harmful final term and the next most harmful fourth and sixth terms.

That is, according to the present invention, a low-frequency noise suppressing effect, which has been conventionally difficult, can be obtained by using the low-frequency enhancing means (105) and the low-frequency attenuating means (203) utilizing the properties of the PN code. At the same time, the low-frequency enhancement means (105) and the low-frequency attenuation means (20)
By setting the position 3) as shown in FIG. 3, the low-frequency noise suppressing effect can be made more effective.

Although the low-frequency enhancement characteristic LB (t) is applied to the second term, due to the nature of the PN code, P
Since the products of the N signals are different PN signals of the same series, they do not have a spectrum component of 1 / Tb or less as described above, and there is little adverse effect due to low-frequency enhancement.

While the series of operations and effects have been described above, the effects will be more specifically described using operation waveform examples obtained by simulation analysis.
It has been confirmed that the simulation analysis method used here matches well with the actual measurement result.

FIG. 10 is a block diagram for simulation analysis based on the principle block diagram of FIG. Here, the transfer function of the sending means (107) and the receiving means (201) =
1 and the data reproducing means (205) outputs a second-order ButterWort of cut-off frequency fc = 1 / (2 * Tb).
h-type LPF (2051) and binarized comparator (20
52). Other specifications are as follows. Data bit time: Tb = 1.275 mSec PN Chip time: Tc = 5 uSec PN Code length: N = 255 PN Delay time: Td = Tc (n = 1) Processing gain (spreading factor): PG = N Low band enhancement Attenuation characteristics: f2 = 1569 Hz (2 / Tb) f1 = 156.9 Hz m = 2 Enhancement / attenuation = 40 dB

First, FIG. 11 shows an example of a simulation analysis of a basic operation without a disturbance signal (501). In the figure, (a) to (k) correspond to the symbols given to the respective sections between the stages in the configuration diagram shown in FIG.

(A) is a data signal, and (b) is a PN signal, both of which are binary signals of [1, -1].

(C) is an output signal of the multiplier (103), that is, a spread spectrum signal, which is nothing but a signal obtained by phase-modulating (PSK) a PN signal with a data signal.

(D) is an output signal of the low-frequency enhancement means (105), which is a reference PN signal (2021). This is the same as FIG.

(E) is the output signal of the adder (106), and as described above, the spread spectrum signal (c) and the reference PN signal (d) coexist without interference. As a result, the signal form is [1, 0,-
1]. This signal (e) is transmitted by the sending means (1
07).

(F) is an input signal of the receiving unit (2). Since there is no disturbance signal (501) here, (e)
It is a signal equivalent to.

(G) is an output signal of the low-frequency attenuating means (203), and the reference PN signal component is returned to a flat characteristic.
It can be seen that the undulations seen in (e) to (f) have disappeared. However, it seems that the waveform distortion seems to remain at first glance due to a low-frequency noise suppression effect that components other than the reference PN signal included in the signal are simply subjected to low-frequency attenuation.

(H) is an output signal of the delay means (202).

(I) is an output signal of the multiplier (204), which is a signal subjected to despreading processing by the operation of (g) * (h). This despread signal waveform (i) includes the components shown in Expression 2, and it can be seen that the data signal is reproduced in the low frequency components. Further, since various noise components included at the same time are PN components or diffusion components, the data signal components and the noise components are separated by a filtering process with a boundary of (1/2 * Tb) which is the fundamental frequency of Tb. can do.

(J) is an output signal of the LPF (2051), which is a data signal component from which a noise component has been removed.

(K) is a binary comparator (2052)
It can be seen that the data signal is correctly reproduced although there is a time delay due to the LPF (2051).

Next, the effect of the present invention on low-frequency disturbance will be described.
A description will be given based on a similar simulation analysis example. Here, the bit rate 520b is used as the disturbance signal (501).
It is assumed that low-frequency disturbance data of ps is added at twice the amplitude of the data signal.

In FIG. 12 showing the analysis results, (a)
(E) is the same as FIG. 11, but the receiving unit (2)
Input signal (f) contains the above-mentioned low-frequency disturbance data. On the other hand, in the output signal (g) of the low-frequency attenuation means (203), the reference PN signal is returned to the flat characteristic, and the low-frequency disturbance data is also effectively suppressed. By suppressing the low-frequency disturbance in the reference signal (2022) in this manner, the delayed signal (f), which is the despread signal, is effectively despread, and the data component is reproduced, and The out-of-band disturbance is diffused and its squared component is suppressed. (See despread signal (i).) As a result, it can be seen that good reproduced data can be obtained as shown in FIG. 7 (k), despite such extreme low-frequency disturbance.

On the other hand, FIG. 13 shows an example in which the same simulation analysis as in FIG. 12 is performed on the conventional example shown in FIG. 2 for comparison. Here, the amplitude of the low-frequency disturbance data is １ ／ of the case of FIG.

In the figure, the influence of the square component of the low-frequency disturbance component appears strongly in the despread signal (i).
As shown in FIG. 9 (k), the reproduced data has been fatally damaged.

On the other hand, in FIG. 12, although the amplitude of the low-frequency disturbance is double, good reproduced data is obtained, and the effect of the low-frequency disturbance can be remarkably reduced by the present invention. Understand.

FIG. 14 shows the case of FIG.
This is a simulation analysis example in the case where Gaussian noise whose effective value is equal to the data signal amplitude is added to the low-band disturbance data as the disturbance signal (501).

When such a wide-band disturbance is added to the low-frequency disturbance, the low-frequency component of the square component thereof is added to the low-frequency disturbance, as can be seen from FIG. As described above, it can be seen that good data transmission can be performed even under such severe conditions.

As described above, according to the first aspect of the present invention, it can be understood that the above-mentioned problems can be solved with a very simple configuration.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a block diagram showing the principle of the embodiment. The low-frequency boosting means (105) is provided after the adder (106), and the low-frequency attenuation means (203) is provided before the two-system branch point. It is configured to be located.

According to this configuration, the reference PN signal (20
Not only 21), but also the spread spectrum signal itself is subjected to low-frequency enhancement, but the spectrum component of (1 / Tb) or less also decreases in the spread spectrum signal. By using (105), the amount of increase in the transmission level can be suppressed lower than the amount of low-frequency enhancement obtained.

The despread signal obtained by this configuration is expressed by the following equation (3). c (t) = {d (t) * p (t) + P (t-τ) + LA (t) * G (t)} *｝ d (t−τ) * p (t−τ) + P (t− 2 * τ) + LA (t) * G (t−τ)｝ c (t) = d (t−τ) * P (t−τ) * p (t−τ) + p (t−τ) * p (T−2 * τ) + d (t) * p (t) * p (t−2 * τ) + d (t) * d (t−τ) * p (t) * p (t−τ) + LA ( t) * {G (t) * p (t−2 * τ) + G (t−τ) * p (t−τ)} + LA (t) * ΔG (t) * d (t−τ) * p (T−τ) + G (t−τ) * d (t) * p (t)｝ + LA (t) * LA (t) * G (t) * G (t−τ) Equation 3) According to Equation 3, although the low-frequency attenuation characteristic is not applied to the fourth term, the low-frequency attenuation characteristic is doubly applied to the most harmful final term, thus suppressing low-frequency disturbance. It can be seen that have a sufficient effect.

This situation will be described again based on a simulation analysis example.

FIG. 15 is a configuration diagram for a simulation analysis based on FIG. 4, and FIG. 16 shows an example of the analysis result. The specifications are the same as those in FIG. However, the amplitude of the disturbance signal (501) was １ ／ of that in FIG.

FIG. 16 (m) shows a signal after the addition signal (e) is boosted in the low frequency band. In this example, the increase in the transmission level is suppressed to slightly less than 8 dB compared to the low frequency boosting amount of 40 dB. You can see

FIG. 10G shows the signal after the low-frequency attenuation processing. The low-frequency enhancement is returned to the flat characteristic, and the low-frequency component of the low-frequency disturbance data is suppressed. As a result, in the signal after despreading shown in FIG. 3I, it is understood that the influence of low-frequency disturbance data is largely removed, and the data component is efficiently reproduced. On the other hand, in this signal, as shown in Equation 3, a DC component due to the fourth term and a DC component due to squaring of the residual high frequency component from the double low frequency attenuation processing applied to the final term are obtained. Since it is contained in a small amount,
It can be seen that in the data reproducing means having an extremely simple configuration used here, the data signal is reproduced as shown in FIG. 9 (k), although the duty ratio has a slight effect.

As described above, a remarkable improvement effect is obtained as compared with the analysis result of the conventional example shown in FIG.
It can be understood that the present invention described in (1) is an effective means for solving the above-mentioned conventional problems.

Next, an embodiment of the present invention will be described. FIG. 5 is a block diagram showing the principle.
The low-frequency attenuation means (203) is provided at the position shown in the figure on the receiving unit (2) side without performing low-frequency enhancement on the transmitting unit (1) side, and only low-frequency attenuation is performed. It is.

However, the low-frequency attenuation means (20
The characteristic of 3) is characterized in that, as shown in FIG. 6B, the attenuation is limited to a certain value in a frequency range lower than f1.

The despread signal in such a configuration is expressed by the following equation (4) when expressed by a mathematical expression following the previous example. c (t) = LA (t) * d (t- [tau]) * p (t- [tau]) * p (t- [tau]) + LA (t) * p (t- [tau]) * p (t-2 * [tau]) + LA (t) * d (t) * p (t) * p (t−2 * τ) + LA (t) * d (t) * d (t−τ) * p (t) * p (t−τ ) + LA (t) * G (t) * p (t−2 * τ) + G (t−τ) * p (t−τ) + LA (t) * ｛G (t) * d (t−τ) * p (t−τ) + G (t−τ) * d (t) * p (t)｝ + LA (t) * G (t) * G (t−τ) (expression) 4) As can be seen from the above, here, the low-frequency attenuation characteristic LA (t) is applied to all items, and while suppressing the low-frequency noise, the data signal component of the first term is also attenuated. As described above, since the low-frequency attenuation characteristic is limited by a certain amount, the data signal component Is not lost.

This situation will be described based on a simulation analysis example following the previous example. FIG. 17 is a configuration diagram thereof, and FIG. 18 is an analysis result thereof.
And the disturbance signal (501) is equivalent to the case of FIG.

FIG. 18 (g) shows a reference signal (2022) that has been subjected to low-frequency attenuation processing. At the same time as the low-frequency component of the disturbance data is suppressed, all other components are similarly subjected to low-frequency attenuation. ing.

However, the reference PN signal contained in this signal is substantially not affected by this low-frequency attenuation due to the nature of the PN code, so that the despreading process can be performed without any trouble.

On the other hand, (i) shows the signal after despreading, and it can be seen that the disturbance data is spread and its low frequency components are suppressed. Also, as shown in Equation 4, since the data signal component of the same signal waveform is also attenuated, it is buried in other noise components and is not so noticeable, but is not lost but binarized. It can be seen that the data is reproduced as shown in FIG.

As described above, the present invention according to claim 3 is also an effective means for solving the above-mentioned conventional problems.

[0067]

Next, an embodiment of the present invention will be described. FIG. 19 is a configuration diagram of a general-purpose data transmission / reception device using the spread spectrum transmission / reception system according to the present invention. As shown in the figure, this embodiment is based on the present invention described in claim 1, and by replacing the data source (801) and the processing unit (802) according to the application, it can be applied to a wide range of application fields at low cost. In addition, this is a general-purpose data transmitting / receiving device that can easily provide the advantage of spread spectrum.
The fields of application referred to here are, for example, voice transmission systems such as wireless intercoms, wireless security systems using various sensors as data sources, keyless entry systems for automobiles, home wireless control systems in HBS and multimedia home rings, various Data transmission and reception in a wide variety of fields such as an industrial wireless control system, wireless data transmission around a personal computer, and the like are targets. The demand for these data transmission / reception systems in the so-called general-purpose field tends to expand further in the future, but there has been no way to achieve the benefits of spread spectrum until now.

As described above, the present invention meets this demand, and the embodiments will be described in detail below.

In the transmission unit (1) of FIG.
The PU (701) receives the data bit time Tb and PN
At the same time as generating a clock signal corresponding to the chip time Tc, it plays the role of a data generating means (101). Here, an original data from the data source (801) is received, and a data signal of an asynchronous transmission type is generated. In this embodiment, the processing gain is set to PG = 255,
It is assumed that Tb = 1.275 mSec and Tc = 5 uSec.

The PN generating means (102) generates an M-sequence code having a code length N = 255 by driving the LFSR by the 8-stage shift register with the Tc clock. Also,
At this stage, since both the data signal and the PN signal are binary signals, the multiplier (103) performs a multiplication process using XOR, and the delay means (104) uses a D flip-flop to perform the PN signal. Is delayed by 1 Tc.

The low-frequency attenuating means (105) is composed of an analog element, and its characteristic is f1 in FIGS. 6 (c) and (404).
= 156.9 Hz, f2 = 1569 Hz, and M = 1, a low-frequency enhancement amount of 20 dB is obtained. As already explained, since an analog component is generated at this stage,
The adder (106) performs analog addition.

The transmission means (107) uses a radio transmission module to perform transmission by radio waves. In this embodiment, an inexpensive AM module is used, but an FM module may be used.

On the other hand, in the receiving unit (2), an AM receiving module is used as the receiving means (201), and the signal transmitted from the transmitting means (107) is received and demodulated.

The low-frequency attenuation means (203) performs low-frequency attenuation processing with the same specifications as the low-frequency enhancement means (105).
(C) A low-band attenuation of 20 dB is obtained in the form of (403).

The delay means (202) has 1Tc = 5
Using an analog delay unit having a delay amount of uSec, the analog multiplier (204) performs the despreading process.

The data reproducing means (205) outputs the LPF (2
05) and a comparator (2052), and the LPF has a cutoff frequency fc = 1 / (2 * Tb) of 2
The following is a Butterworth type LPF.

With the above configuration, the comparator (20
The original data information is restored by the CPU (702) from the start-stop synchronization type data signal reproduced at the output of (52) and passed to the processing unit (802), and the intended processing is performed.

As described above, in this embodiment, the spreading process and the despreading process are performed in the baseband region. By adopting such a configuration, versatility is increased, for example, in addition to being inexpensive, conversion to baseband transmission such as a power line carrier method can be easily performed. Also,
In such a configuration of the baseband processing type, a near interference wave, an image interference wave, an intermodulation interference wave, or the like appears as low-frequency disturbance at the output of the receiving means (201). By adopting, these effects are greatly reduced while having a simple configuration, and good transmission quality is obtained.

Hereinafter, a description will be given based on actually measured evaluation data in this embodiment. Here, in order to more directly evaluate the performance as a spread spectrum system, the transmission means (107) and the reception means (201) are replaced with line driver models, and an evaluation example performed under a configuration corresponding to FIG. This will be described with reference to FIG. In this evaluation, in order to simplify the evaluation, the data signal to be transmitted is represented by Tb =
1.275 mSec simple [1,0] repetition data was used.

First, the operation waveforms of the respective parts were actually measured.
A result which agrees well with the prediction operation by the simulations shown in FIGS. 11 and 14 has been confirmed, and it is confirmed that this embodiment satisfies the intended purpose.

FIG. 20 shows measured waveforms in an actual operation when there is no disturbance signal. FIG. 2A shows an example of observing the data signal (upper) in the transmission unit (1) and the output signal of the adder (106) (lower), and the effect of the low frequency band enhancement of 20 dB appears. It can be seen that the transmission level is hardly affected.

FIG. 11B shows the output signal (upper) of the multiplier (204) and the LPF in the receiving unit (2).
This is an example in which the output signal of (2051) is observed, and it can be clearly seen that the data component is reproduced by the despreading process. Finally, the comparator (20) in the lower stage of FIG.
As shown by the output signal of 52), the data signal is correctly reproduced.

Next, an evaluation result when a disturbance signal is added in the middle of the transmission path will be described. The following two types of disturbance signals were used. Disturbance signal 1 (G1): random white noise. (Amplitude variable) Disturbance signal 2 (G2): bit time Tbn = 1.92 m
Sec low-frequency disturbance data. (The same amplitude as the data) FIG. 20 (d) shows the output (upper) of the multiplier (204) and the comparator (2052) when G1 and G2 having the amplitude corresponding to S / N = 0 dBrms are simultaneously added.
It is an example of the actually measured waveform which observed the output (lower). In the figure, low-frequency disturbance data is effectively suppressed in the despread signal waveform, and as a result, the data reproducing means (20
It can be seen that 5) makes it possible to reproduce data under such severe conditions, although it is a very simple combination of an LPF and a comparator.

In the reproduced data shown in FIG. 10, the jitter component appears as a slight disturbance in the duty ratio. Since the jitter component is a major factor in determining the bit error rate (BER), the BER characteristic will be described below. The result of evaluating the transmission quality will be described.

FIG. 21 is an example of actual measurement of BER characteristics in this embodiment. FIG. 9A is an example of BER measurement when only white noise (G1) is applied as a disturbance signal, and BER = 10 at an effective value S / N = 0 dBrms.
A performance of about -3 has been obtained. This value is expensive
This is comparable to the actual example (not shown) of the baseband transmission system according to the conventional configuration.

Further, the BE shown in FIGS.
The R characteristic is a unique evaluation method in this evaluation, and in order to make it closer to the disturbance in the baseband processing type system, not only the white noise (G1) but also the low-frequency disturbance data (G2) is simultaneously added, and the horizontal axis is used. Is plotted using the S / N value by G1. However, B in FIG.
The ER characteristic is a measured BER example in a case where the low-frequency enhancement means (105) and the low-frequency attenuation means (203) are removed and the configuration of the conventional example in FIG. 2 is used for comparison.

The conventional configuration suffers a fatal transmission failure due to the mixing of low-frequency disturbance data, as shown in FIG. 4C, whereas the present embodiment has a fatal transmission failure as shown in FIG. As shown in FIG. 7, BER characteristics that are not much different from those in FIG. 11A are obtained, and it is found that by implementing the present invention, an extremely large effect can be obtained with a simple configuration.

As an application of the present embodiment, it goes without saying that the transmission quality is further improved by using both high-frequency pre-emphasis and de-emphasis and by devising the structure of the data reproducing means.

Also, in the present invention, data confidentiality, which is one of the other effects of the spread spectrum system, can be realized by using the PN delay amount as an identification key. It means that application is possible.

[0090]

As described above, according to the spread spectrum system according to the present invention, the data signal of the data signal is extremely simple and inexpensive without using expensive special parts and complicated PN synchronization circuit. Good data transmission / reception is possible even when a low-frequency disturbance signal that interferes with the basic bandwidth is added, and it has the effect of building a highly versatile system. This has an extremely large effect of enabling the introduction of a spread spectrum system into a computer.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram showing a first conventional example.

FIG. 2 is a principle configuration diagram showing a second conventional example.

FIG. 3 is a principle configuration diagram of a spread spectrum transmitting / receiving system according to the present invention described in claim 1;

FIG. 4 is a principle configuration diagram of a spread spectrum transmitting / receiving system according to the present invention described in claim 2;

FIG. 5 is a principle configuration diagram of a spread spectrum transmitting / receiving system according to the present invention described in claim 3;

FIG. 6 is a conceptual diagram showing characteristics of a low-frequency enhancement means (105) and a low-frequency attenuation means (203).

FIG. 7 is a diagram showing an autocorrelation characteristic of a PN code.

FIG. 8 is a diagram illustrating an example of a PN signal and an example of a reference PN signal after low-frequency enhancement.

FIG. 9 is a diagram showing a spectrum distribution of a PN signal.

FIG. 10 is a configuration diagram for a simulation analysis according to the present invention described in claim 1;

FIG. 11 is a diagram illustrating an example of a simulation analysis.

FIG. 12 is a diagram illustrating an example of a simulation analysis.

FIG. 13 is a diagram illustrating an example of a simulation analysis.

FIG. 14 is a diagram showing a simulation analysis example.

FIG. 15 is a configuration diagram for a simulation analysis according to the present invention described in claim 2;

FIG. 16 is a diagram showing a simulation analysis example.

FIG. 17 is a configuration diagram for a simulation analysis according to the third embodiment of the present invention.

FIG. 18 is a diagram illustrating an example of a simulation analysis.

FIG. 19 is a configuration diagram of an embodiment.

FIG. 20 is a diagram illustrating an example of an actually measured waveform in the example.

FIG. 21 is a diagram showing an example of actual measurement of BER characteristics in the embodiment.

DESCRIPTION OF SYMBOLS 1 Transmitting unit 2 Receiving unit 101 Data generating means 102 PN signal generating means 103 Multiplier 104 Delaying means 105 Low band enhancing means 106 Adder 107 Sending means 201 Receiving means 202 Delaying means 203 Low band attenuating means 204 Multiplication Device 205 data reproducing means

Claims (3)

[Claims] 1. A transmitting unit for processing and transmitting data in a form suitable for transmission, and a receiving unit for receiving a signal transmitted from the transmitting unit and extracting the data by a predetermined demodulation process. A data transmission / reception system, wherein the transmission unit includes a data generation unit (101), a PN code generation unit (102), a multiplier (103), and a delay time that is an integral multiple of a chip time of the PN code. Delay means (104), low-frequency enhancement means (105) for enhancing a low-frequency region including the basic spectrum bandwidth of data, an adder (106), and transmission means (107), and Data generation means (101)
And the output of the PN code generation means (102) are added to a multiplier (103) to extract a spread spectrum signal from the output. Further, the spread spectrum signal and the PN code generation means (102) are output. ) And a signal obtained by passing a part of the output through the delay means (104) and the low-frequency enhancement means (105) to an adder (106), and the output signal is transmitted by the transmission means (107). The receiving unit includes: a receiving unit (201) for receiving a signal transmitted from the transmitting unit; and a delay unit (20) having a delay time equal to the delay unit (104).
2) a low-frequency attenuating means (203) having characteristics opposite to those of the low-frequency enhancing means (105); a multiplier (204); and a data reproducing means (205), and a receiving means (8).
Is divided into two, one of which is delayed by a delay means (202)
And the other side to low-frequency attenuation means (203)
, Through which both are added to a multiplier (204), a despread signal is extracted from the output thereof, and a target data signal is extracted from the despread signal by data reproducing means (205). A spread spectrum transmission / reception system, characterized in that: 2. A transmission unit configured to process data and transmit the data in a form suitable for transmission, and a reception unit that receives a signal transmitted from the transmission unit and extracts the data by a predetermined demodulation process. An information communication system according to claim 1, wherein said transmitting unit comprises: a data generating means (101);
N code generating means (102), multiplier (103), P code
Delay means (104) having a delay time that is an integral multiple of the chip time of the N code, and low-frequency enhancement means (105) for enhancing a low-frequency region including a basic spectrum bandwidth of data;
, An adder (106), and a sending means (107). The output of the data generating means (101) and the output of the PN code generating means (102) are added to the multiplier (103). An adder is configured to extract a spread spectrum signal from the output, and further adds the spread spectrum signal and a signal obtained by passing a part of the output of the PN code generating means (102) through the delay means (104) to an adder. In addition to (106), the output signal is transmitted through low-frequency enhancement means (105) and transmitted by transmission means (107). The reception unit transmits the signal transmitted from the transmission unit. Receiving means (201) for receiving the delay signal, and a delay means (20) having a delay time equal to the delay means (104).
2) a low-frequency attenuating means (203) having characteristics opposite to those of the low-frequency enhancing means (105); a multiplier (204); and a data reproducing means (205), and a receiving means (8).
After passing through the low-frequency attenuating means (203), the signal is branched into two, one of which is passed through the delay means (202), and the other is left as it is, and both of them are multiplier (204).
A spread-spectrum transmission / reception system characterized in that a despread signal is extracted from the output thereof, and a target data signal is extracted from the despread signal by the data reproducing means (205). 3. A transmitting unit for processing and transmitting data in a form suitable for transmission, and a receiving unit for receiving a signal transmitted from the transmitting unit and extracting the data by a predetermined demodulation process. An information communication system according to claim 1, wherein said transmitting unit comprises: a data generating means (101);
N code generating means (102), multiplier (103), P code
A delay unit (104) having a delay time that is an integral multiple of the chip time of the N code; an adder (106);
7), and outputs the output of the data generating means (101) and the output of the PN code generating means (102) to the multiplier (1).
03), in order to extract a spread spectrum signal from the output thereof,
A signal obtained by passing a part of the output of the PN code generating means (102) through the delay means (104) is added to the adder (106), and the output signal is sent out to the sending means (107).
The receiving unit comprises: a receiving unit (201) for receiving a signal transmitted from the transmitting unit; and a delay unit (20) having a delay time equal to the delay unit (104).
2) a low-frequency attenuating means (203) for attenuating a low-frequency region including a basic spectrum bandwidth of data; a multiplier (204); and a data reproducing means (205).
Further, the output of the receiving means (8) is branched into two, one of which is made to pass through the delay means (202), the other is made to pass through the low-frequency attenuating means (203), and both are made to the multiplier (204) ), A despread signal is extracted from the output, and a target data signal is extracted from the despread signal by the data reproducing means (205). The attenuation characteristic has two corner frequencies f1 and f2 (f1 <f2). In the frequency range of f> f2, the attenuation is constant at 0 dB, and f1 ≦ f ≦
In the frequency chain region of f2, it has an m-th order slope characteristic, and furthermore, f <f
A spread-spectrum transmission / reception system having characteristics such that the attenuation becomes constant again in the frequency domain of 1.