JPH069347B2 - Spread spectrum communication system - Google Patents

Description

The present invention relates to a spread spectrum communication system, and in particular, in despreading on the receiving (demodulating) side, a circuit configuration in which it is relatively easy to generate a fake noise code. The spread spectrum communication system realized in.

[Technical background]

Spread spectrum (SS) communication method was developed in Europe about 50 years ago, and its basic idea is 1950.
Established in the decade. In the 1960s, a pseudo-noise code generation circuit was created with 100 transistors, but the early technology was immature, and the development of active elements and manufacturing technology that compose them was long awaited. In recent years, due to the development of high-density IC technology and the cost reduction of ICs, it has become possible to manufacture small-sized and low-priced devices, and such a communication system is regaining attention. The spread spectrum communication system is a system in which a carrier is first-modulated by an information signal and secondarily modulated by a broadband noise-like spread code to spread it in a very wide band. Generally, there are a direct spread (DS) system, a frequency hopping (FH) system, a hybrid system, etc. depending on the difference in the secondary modulation system, and the present invention system is related to the former DS system.

Such spread spectrum communication has the following excellent features.

The confidentiality is very high.

Strong against external interference, noise, and intentional interference.

Can coexist with conventional systems.

There is no need for a control station or control channel such as an MCA station.

Can be managed by address code.

Since the power density is low in the direct diffusion method, it seems that there is no radio wave (we can transmit with weak power).

The number of stations can be increased by allowing a slight decrease in call quality.

It is possible to multiplex in the same frequency band by changing the pseudo noise code signal.

These features have been re-recognized, and now they are being applied not only in the telecommunications field but also in other fields, and are beginning to be applied to consumer equipment.

[Conventional technology]

The basic principle of spread spectrum communication will be described with reference to FIGS. 8 and 9. FIG. 8 is a basic configuration diagram of a communication device which realizes a conventional spread spectrum communication system by the DS system, and FIG. 9 is a spectrum diagram in each component. As shown in FIG. 8, the signal (F ₁ ) as shown in FIG. 9 (a), which is primary-modulated by the primary modulation circuit 41 on the transmission side (station A), is output from the spread code generation circuit 39. The spread code signal (F _SS ; see FIG. 2B) is used by the spread modulation circuit 46
The signal is then modulated and amplified, and then output as a transmission signal (F _1S ) from the antenna A ₁ . The type of primary modulation is not particularly limited, and frequency modulation (FM) or PSK (Phase Shift Keyin)
g) or the like (which is described as performing modulation by PSK in the present specification), the secondary modulation (spread modulation) is generally PS by a pseudo noise code (Pseudo Noise: PN code).
K-modulate. This PN code should be as random noise as possible and should have a constant period for the receiver to retrieve the code.

Next, the configuration and functions of the receiving side will be described. On the receiving side (station B), the despreading circuit 47 outputs the F _1S signal obtained from the antenna A ₂ by the predetermined filter and the high frequency amplifier.
In, despreading is performed by the spreading code from the spreading code generation circuit 49. The spread code generation circuit 49 is synchronized with the spread code generation circuit 39 of the A station, and the PN code is the same (F _SS ). By the way, the radio waves coming into the antenna A ₂ are not limited to F _1S, but as shown in FIG. 9 (c), radio waves from other SS stations (F _2S , F _3S , ...) Radio wave (Fn) exists. Therefore, by performing despreading in the despreading circuit 47, the desired radio wave F _1S as shown in FIG. 7D is returned to the spectrum as shown in FIG. 2A and a filter (preferably a narrow band reactor) is used. Most of the components other than F _1S are removed at 45 (see (e) in the figure), and the demodulation circuit 48 demodulates the original information signal and outputs it. The figure
As can be seen from (e), in the output signal of the filter 45, in addition to F _1S , Fn of the interference wave and a part of the SS wave of multiple stations remain. The ratio of this residual power to the power of the target signal is called the DN ratio (signal power to interference power ratio), and in order to obtain a large DN ratio, it is advantageous that the spreading band is as wide as possible. It is about 100 to 1000 times the frequency band of the information signal.

The basic principle of spread spectrum communication has been described above.
Next, a specific operation in each modulation / demodulation will be theoretically explained. In the spread spectrum signal S (t) {F _{1S in} FIG. 8} in spread spectrum communication, information data is d (t) [+ 1 or -1] and spreading code F _SS is P (t) [+ 1 or-. 1], carrier wave cosω
Let ct be expressed by the following equation.

S (t) = d (t) P (t) cos ωct ………… (1) (where ωc = 2πfc) This spread spectrum signal S (t) is the spread spectrum signal received at reception (demodulation). A spread code clock signal is generated from the signal, and a spread code P (t) synchronized with the spread code in the spread spectrum signal at the time of transmission (actually with some delay) D (t) cosωct by multiplying the incoming spread spectrum signal S (t) {also called correlation or despreading}
Is converted to a two-phase PSK signal. Furthermore, the reproduced carrier c
osωct The information data d (t) is demodulated by performing synchronous detection on the multiplication with d (t) (cosωct) ² = d (t) (1 + cosωct) / 2.

[Problems to be Solved by the Invention]

In such a spread spectrum communication system, the despreading on the receiving side is the most important, but it is not easy to generate the spreading code necessary to do this. At present, the AFC control loop,
A despreading method using a delay locked loop and a multiplier, and a despreading method using a locked loop and a multiplier using a matched filter are generally used. The despreading by these configurations has a complicated circuit configuration, and there are problems in terms of adjustment and cost, and it is necessary to solve these problems when deploying to consumer equipment.

[Means for Solving the Problems]

According to the communication system of the present invention, a means for generating a first two-phase PSK signal by inputting an information signal and a first carrier wave and multiplying the information signal and the second carrier wave are input to the modulation side. And a means for obtaining a second two-phase PSK signal, a means for inputting a clock signal and generating a spread code signal based on this, a first two
Means for obtaining a first spread signal by inputting a phase PSK signal and a spread code signal and spreading by multiplication, and a second two-phase PS
Means for inputting the K signal and the spread code signal to perform spread by multiplication to obtain a second spread signal; means for generating a control signal in synchronization with the spread code signal based on the clock signal; and a control signal The second demodulation signal is input and means for obtaining a multiplication output signal by multiplication, and means for adding the multiplication output signal and the first spread signal to generate a spectrum spread signal and outputting the spread spectrum signal are provided. Means for inputting a spread spectrum signal and separating the spread spectrum signal into a first spread signal and a multiplication output signal having different spectrum components according to the first and second carriers, and multiplying the separated first spread signal Means for separating a control signal by inputting and processing the output signal and a spread code signal on the modulation side for reproducing a clock signal and a reset signal based on the control signal A demodulated two-phase PSK signal is obtained by inputting the means for generating the spread code signal synchronized with the input signal, the generated spread code signal, and the first spread signal separately detected, and performing despreading by multiplying both signals. Means and means for demodulating and outputting an information signal equivalent to that at the time of modulation by synchronously detecting the demodulated two-phase PSK signal,
The above problems are solved.

〔Example〕

Since the spread spectrum communication system of the present invention performs communication with the above-described configuration, a clock recovery circuit, a synchronization pull-in circuit composed of a loop, a synchronization holding circuit, etc., which have been indispensable in the past in despreading, are unnecessary. In the following, an example of an apparatus that can realize the method of the present invention will be described and described with reference to the drawings.

FIG. 1 is a block configuration diagram of an embodiment of a spread spectrum communication apparatus which realizes a spread spectrum communication system of the present invention, in which FIG. 1 (A) is a modulation section (transmission side) 1 and FIG. It is a part (reception side) 2. In this figure, a part of the configuration of the antenna and the like is omitted.

The modulator 1 includes an LPF (low pass filter) 15, five multipliers 3 to 7, an arithmetic circuit (adder) 28, and a spread code generation circuit (P
NG) 26, frequency divider 14, monostable multivibrator (hereinafter also simply referred to as “mono-multi”) 19, BPF (bandpass filter) 21, etc., and these are connected as shown in FIG. 1 (A). Are configured. In addition, the demodulation unit 2 has two BPs.
F22, 23; LPF 16, delay circuit (DL) 29, adder 30, subtractor 31, control signal detection circuit (hereinafter also referred to as "C (t) detection unit") 33, N multiplication circuit 34, monomulti 35, diffusion Code generation circuit 27, carrier wave regenerator 3
6, and two multipliers 8, 9 and the like, which are shown in FIG.
(B) Connected as shown. The delay circuit 29, the adder 30, and the subtractor 31 form a comb-shaped filter 32 having two types of characteristics, and the frequency characteristics thereof are shown in FIGS. 2 (A) and 2 (B), respectively. And as a subtraction characteristic. Specific functions and operations will be described below with reference to the spectrum diagrams of FIGS. 3 and 4.

When transmitting first, in the modulator 1, the input terminal In
_{From 1 the} information signal d (t) (in this case, data) is LPF
It is supplied to the multipliers 3 and 4 via 15. On the other hand, the carrier signal cos ωc ₁ t is supplied from the input terminal nIn _n2 to the multiplier 3 to perform multiplication with the information signal d (t), and
(A) Primary modulation signal d (t) cosωc ₁ t (here, two-phase P
SK modulated signal) is generated and output to the multiplier 5. Similarly, the carrier signal cos ω _c2 from the input terminal In _n3
t is supplied to the multiplier 4 to perform multiplication with the information signal d (t), and the two-phase PSK modulation signal d (t) co as shown in (b) of FIG. 3 (B).
The sω _c2 t signal is generated and output to the multiplier 6. Further, the clock signal Sc (t) is fed from the input terminal _Inn4 to the frequency divider 14
And the spread code generating circuit 26, and the spread code generating circuit 26 generates the spread code signal P (t) based on the clock signal Sc (t). As a spread code, a pseudo noise code is often used, so it is a "pseudo noise code".
Sometimes called.

In this embodiment, the M-sequence code is used as an example, and the frequency divider 14 and the monomulti 19 are provided for resetting within the M-sequence code cycle. The spreading code generation operation will be described with reference to the timing chart of FIG. First, the frequency divider 14 inputs the clock signal Sc (t), frequency-divides it to generate a control signal C (t) as shown in FIG. 5 (C), and supplies it to the monomulti 19. The mono-multi 19 differentiates the control signal C (t) to generate a pulse as shown in FIG. 9 (A) at the rising timing thereof, and supplies this to the spreading code generation circuit 26 as a reset signal. The spread code generating circuit 26 inputs the reset signal and the clock signal Sc (t) and generates a spread code signal P (t) as shown in FIG.

The spread code signal P (t) thus generated is supplied to the multipliers 5 and 6, where the above-mentioned two-phase PSK signal d (t), respectively.
Spread spectrum is performed by multiplication with cos ω _c1 t and d (t) cos ω _c2 t, and spread spectrum signal P (t) d (t) cos
ω _c1 t and P (t) d (t) cos ω _c2 t are output to the adder 28 and the multiplier 7, respectively. Since the control signal C (t) is supplied from the frequency divider 14 to the multiplier 7, both signals are multiplied here, and the output signal P (t) d (t) C is obtained.
(t) cosω _c2 t (hereinafter also referred to as “S ₂ (t)”) is supplied to the adder 28, and here the spread spectrum signal P (t) d (t) cosω _c1 t (hereinafter “S ₂ (t)”). S ₁ (t) ”), and P (t) d (t) {cosω _c1 t + C (t) cosω
_c2 t} (hereinafter also referred to as “S _M (t)”), and the BPF
In FIG. 21, only the main lobe of the spread spectrum signal as shown in FIG. 4 is passed and transmitted, and a signal having a spectrum as shown in FIG. 3 (C) is output from the output terminal Out ₁ .

Here, the principle of spread spectrum will be described. As for the interval between the angular frequencies ω _c1 and ω _c2 in FIG. 3 (A), the 1-bit time length of the clock signal Sc (t) is T _0, and the spread code signal P (t) from the spread code generating circuit 26 is When the number of bits in one frame is F, the interval is given by (2F × T ₀ ) ⁻¹ . In the frequency spectrum of the spread spectrum signal shown in FIG. 3 (C), sidebands + Sa ₁ and + Sa ₂
And the frequency interval between + Sb ₁ and + Sb ₂ is (F ×
The spacing is given by T ₀ ^-1 and the sideband + Sa ₁
~ + Sa _n, and -Sa ₁ ~-Sa _n, sideband _{+ Sb 1 ~ + Sb n,} -Sb 1
~ -Sb _n are alternately arranged at equal intervals. In addition,
The solid line (c) in FIG. 4 (between (a) and (b) in the figure) shows the methylobe of the spread spectrum signal. One frame of the spread code signal P (t) is an example of t ₁ and t _{2 in} FIG.
14 bits / frame between t ₂ and t ₃ .

Next, referring also to FIG. 1 (B) and FIG. 3, the demodulation unit 2
The function of will be described. The third that came into the input terminal In ₅
The spread spectrum signal S _M (t) as shown in FIG.
The frequency components other than the spread spectrum signal are removed at and are simultaneously supplied to the positive input terminals of the delay circuit 29, the adder 30, and the subtractor 31. Since the output of the delay circuit 29 is supplied to the negative input terminals of the adder 30 and the subtractor 31, the delay circuit 29, the adder 30 and the subtractor 31 add the addition characteristic and the subtraction characteristic ( Comb-tooth filters 32 having the respective configurations shown in FIGS. 2A and 2B are formed. Now, assuming that the delay time in the delay circuit 29 is T (= 1 / lower), in the case of addition, as shown in FIG. 2 (A), 1 / T, 2 / T, 3 / T, ..., N / The gain doubles at the frequency of T (N is a natural number), and the output becomes 0 at each intermediate frequency, and a steep dip can be made. In the case of subtraction, conversely, as shown in FIG. 7B, 1 / T, 2 / T, 3 /
At the frequencies of T, ..., N / T, there is a valley (gain is 0), and at each intermediate frequency, the gain is doubled. Therefore,
By setting the delay time to T = F × T _0, and matching the frequency of the crests or troughs of the comb-teeth filter 32 to the sideband frequency of the spread spectrum signal, the first spread signal in the spread spectrum signal S _M (t) S ₁ (t) {P (t) d (t) cosω _c1 t}
And the second spread signal S ₂ (t) {P (t) d (t) ccosω _c2 t} can be separately detected. As a result, the output signal of the adder 30 becomes S ₁ (t) (see FIG. 3D), and the output signal of the subtractor 31 becomes S ₂ (t) (see FIG. 3E).
Although a specific separating operation of the comb-teeth filter 32 will be described later, the expression of the delay of the spread spectrum signal S _M (t) by the delay circuit 29 is omitted here for convenience of explanation.

The addition output signal S ₁ (t) from the adder 30 and the subtraction output signal S ₂ (t) from the subtractor 31 are supplied to the C (t) detection unit 33,
Here, the control signal C (t) is separated and detected. C
(t) The specific circuit configuration of the detection unit 33 is, for example, as shown in FIG. 6, two carrier wave regenerators 37 and 38; three multipliers 10 to 12, BPF 24, PLL (phase locked loop) 42, and Two LPFs 17 and 18 are provided, and these are connected as shown in FIG. Input terminal In ₆
From which the addition output signal S ₁ (t) is supplied to the multiplier 10 and the carrier wave regenerator 37, and the subtraction output signal S ₁ (t) from the input terminal In _7.
2 (t) is supplied to the multiplier 11 and the carrier wave regenerator 38. These carrier wave regenerators 37 and 38 are, as shown in FIG. 7, specifically, the multiplier 13, the BPF 25, and the PLL.
43 and 1/2 divider 44 are provided, and these are connected as shown in FIG. That is, this is a doubled carrier recovery circuit. Here, the addition output signal S ₁ (t) in the multiplier 13 (the carrier recovery device 38 is the subtraction output S ₂ (t) first, but in principle, Are the same, so the description is omitted}
Get on. The signals S ₁ (t) and S ₂ (t) are modulated in two phases of 0 ° and 180 ° as in the case of the two-phase PSK signal. Therefore, if the multiplier 13 doubles the frequency, It is converted into a continuous double-frequency carrier path. That is, since S ₁ (t) is approximately P (t) cosω _c1 t, the binary signal P (t) is converted into a direct current by the square operation, and the carrier wave cosω _c1 t is cosω.
2 _c1 t. The output of the multiplier 13 is used as the BPF of the next stage.
After the unnecessary frequency component is removed at 22, it is supplied to the phase locked loop (PLL) 43. The PLL 43 is composed of a multiplier (or a phase comparator), an LPF (or a loop filter), a VCO, etc., in which unnecessary noise components in the input signal are removed and a carrier wave having a doubled frequency with a constant amplitude is provided. Is obtained. This carrier wave is subjected to signal processing by the 1/2 frequency divider 44, and the reproduced carrier wave cosω _c1 t is output.

Similarly in the carrier wave regenerator 38, the reproduced carrier wave cos
omega _c2 t is obtained, each carrier cos .omega _c1 t and cos .omega _c2 t is supplied to each multiplier 10 and the multiplier 11, the addition output signal S ₁ (t) and the subtraction output signal S ₂ (t) and the respective multiplier After being
Unnecessary frequency components are removed by the LPFs 17 and 18 at the next stage, and P (t) d (t) and P (t) d (t) C (t) are demodulated, respectively. The control signal C (t) is obtained by supplying both of these demodulated signals to the multiplier 12 and multiplying them. Further, the BPF 24 and the PLL 42 remove unnecessary noise components to output a high-quality control signal C (t) from the output terminal Out ₂ . That is, as described above
The C (t) detector 33 separates and detects the control signal C (t).

The control signal C (t) is supplied to the N multiplication circuit 34 and the monomulti 35 in the next stage. The N multiplication circuit 34 multiplies the control signal C (t) by N (N = 14 in the example of FIG. 5).
Then, a clock signal equivalent to the clock signal Sc (t) on the transmission side (modulation unit 1) is created. On the other hand, Mono Multi 3
In 5, a reset signal equivalent to the reset signal on the transmission side is generated and supplied to the spread code generation circuit 27 together with the clock signal Sc (t). The spread code generation circuit 27 has the same configuration as the spread code generation circuit 26 on the transmission side (and the conventional circuits 39 and 49 shown in FIG. 8). Therefore, by inputting the clock signal and the reset signal, the spread code generation circuit 27 A signal equivalent to the spread code signal P (t) can be obtained. This spread code signal P (t) is added to the addition output signal P (t) d.
By supplying (t) cosω _c1 t together to the multiplier 8,
By performing despreading by multiplication and further removing unnecessary frequency components by the BPF 23, the two-phase PSK signal d (t) co
sω _c1 t is demodulated. The carrier regenerator 36 uses this demodulation 2
The phase PSK signal d (t) cosω _c1 t is input and the carrier cosω _c1 t is regenerated by the same principle as the carrier regenerator 37 and supplied to the multiplier 9. The multiplier 9 demodulates the two-phase PSK signal d (t)
cos .omega _c1 t was subjected to synchronous detection by multiplying by entering with a carrier cos .omega _c1 t, by removing unnecessary frequency components by LPF 16, to obtain only the information signal d is demodulated (t) from the output terminal Out ₂ It can be done.

Here, the separation detection operation of the spread spectrum signal S _M (t) (the operating principle of the comb-teeth filter 32 and the like) will be described. The spread spectrum signal S _M (tT) output from the delay circuit 29 of FIG. 1 (B) is S _M (tT) = P (tT) d (tT) × {cosω _c1 (t−T) + C (t −T) cos ω _c2 (t
-T)} ... (2). Here, as a precondition, the period of P (t) is equal to the delay time T, cosω _c1 t is in-phase at the period of P (t), a continuous wave that repeats at the same level, and cosω _c2 t is of P (t). reverse phase period, if continuous wave repeated at the same level, S _M (tT) _{is, S M (tT) = P} (t) d (tT) {cosω c1 t-C (tT) cosω c2 t} ... ……… (3). Therefore, the addition output S _M (t) + S _M (tT) {= S
₁ (t)} is S ₁ (t) = S _M (t) + S _M (tT) = {d (t) −d (tT)} P (t) C (t) cosω _c2 t + {d ( t) + d (tT)} P (t) cosω _c1 t (4) On the other hand, the subtraction output S ₂ (t) is S ₂ (t) = S _M (t) −S _M (tT) = {d (t) + d (tT)} P (t) C (t) cosω _c2 t + {d (t) -d (tT)} P (t) cosω _c1 t (5) Here, if the delay time T is sufficiently shorter than the 1-bit time length in the information data d (t), equation (5) and
{D (t) -d (tT)} in the equation (6) has a very small value, and S ₁ (t) and S ₂ (t) can be approximated as follows.

S ₁ (t) ≈ {d (t) + d (tT)} P (t) cosω _c1 t …… (6) S ₂ (t) ≈ {d (t) + d (tT)} × P (t ) C (t) cos ω _c2 t (7) Next, the detection operation of the control signal C (t) in the C (t) detection unit 33 will be specifically described with reference to FIG.
The carrier wave regenerator 37 receives the addition output signal S from the input terminal In _6.
1 (t) is input to generate a reproduced carrier wave cosω _c1 t, which is supplied to the multiplier 10, where it is multiplied by S ₁ (t) to obtain P (t) (1 + cos2ω _c1 t) Output {d (t) + d (tT)} / 2. The high frequency component of this output signal is removed by the LPF 17 to become {d (t) + d (tT)} P (t) / 2 and the multiplier 12
Is output to. Similarly, the carrier regenerator 38 has an input terminal In
Input the subtraction output signal S ₂ (t) from ₇ and reproduce carrier wave cos
ω _c2 t is generated and supplied to the multiplier 11, where it is multiplied by S ₂ (t) to obtain P (t) C (t) (1 + cos2 ω _c2 t) {d (t) +
It outputs d (tT) / 2. This output signal is LPF18
The high frequency component is removed at P (t) C (t) {d (t) +
The result is d (tT)} / 2 and is output to the multiplier 12. Therefore, in the multiplier 12, both signals are multiplied. Becomes By the way, except for the control signal C (t), the DC voltage is almost the same.
Only C (t) is output. The PLL 42 in the next stage is used for the purpose of further effectively reducing the noise component in the input signal and obtaining a control signal having a constant amplitude (binary signal of 1 or 0). Therefore, the binarized control signal C (t) is output to the output terminal Out ₃ .

Next, the operation principle of the N multiplication circuit 34, the monomulti 35, and the spread code generation circuit 27 will be described. The N multiplication circuit 34 inputs the control signal C (t) from the C (t) detector 33 and multiplies it by N to generate the clock signal Sc.
(t) is generated and supplied to the spread code generation circuit 27.
This N multiplication operation is in comparison with the N division of the frequency divider 14 of the modulator 1. On the other hand, the monomulti 35 receives the control signal C (t), generates a reset signal as shown in FIG. 5 (A), and outputs it to the spread code generation circuit 27. Therefore, the spreading code generating circuit 27 operates on the transmitting side (modulation unit 1).
The operation is exactly the same as that of the spread code generating circuit 26. As a result, the output signal of the spread code generating circuit 27 becomes the generated spread code P (t).

Next, the despreading operation will be specifically described according to the configuration of FIG. The multiplier 8 uses the generated spread code P
(t) and the addition signal S ₁ (t) are input, and despreading is performed by multiplication of both signals. This Signal is demodulated, and components such as direct current are removed by the BPF 23 at the next stage, so that the demodulated two-phase PSK signal {d (t) + d
(tT)} cosω _c1 t is obtained.

Finally, the demodulation operation of the information data d (t) will be described.
The operation of the carrier wave regenerator 36 is basically the same as that of the carrier wave regenerators 37 and 38. Therefore, demodulation 2 phase from BPF23
PSK signal {d (t) + d (tT)} cosω _c1 t
Play cosω _c1 t. The reproduced carrier wave cos ω _c1 t is
The demodulated two-phase PSK signal {d (t) + d (tT)} cos is applied to the multiplier 9.
Coincident detection is performed by supplying and multiplying together with ω _c1 t, and the information data d (t) is demodulated by removing unnecessary noise components in the signal by the LPF 16 at the next stage, and output from the output terminal Out _2. Is done.

〔effect〕

Since the spread spectrum communication system of the present invention performs communication using the above configuration, it has the following excellent features.

The despreading by the AFC control loop, the delay locked loop and the multiplier, which are indispensable constituent elements in the conventional method, is specifically a clock recovery circuit, a spread code generation circuit, a sync pull-in circuit and a sync hold circuit composed of a loop. However, most of the circuits other than the spreading code generation circuit are unnecessary, the cost can be reduced by simplifying the circuit configuration, and the application to consumer equipment is facilitated.

Since some circuits that require advanced technology, such as the sync pull-in circuit and sync hold circuit, are no longer required, there is the drawback that the sync pull-in time in the conventional method takes time,
Freed from problems such as possible loss of synchronization,
This can contribute to stabilizing the operation of the spread spectrum communication system.

[Brief description of drawings]

1 (A) and 1 (B) are block configuration diagrams of a modulator and a demodulator, respectively, of an embodiment for realizing the spread spectrum communication system of the present invention, and FIGS. 2 (A) and 2 (B) are comb-shaped filters. Frequency characteristic diagram of
FIGS. 3 (A) to (E) are frequency spectrum diagrams for explaining the operation of each component shown in FIG. 1, FIG. 4 is a spread spectrum signal waveform diagram, and FIG. 5 is an operation explanation of the main part of the circuit of FIG. Timing chart, FIG. 6 is a circuit block diagram of the control signal detection circuit, FIG. 7 is a circuit block diagram of the carrier regenerator,
FIG. 8 is a basic block configuration diagram of a communication device which realizes a conventional spread spectrum communication system, and FIG. 9 is a spectrum diagram in each component of the block diagram shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Modulation part, 2 ... Demodulation part, 3-13 ... Multiplier, 14 ... Frequency divider, 15-18 ... LPF (low pass wave filter), 19, 35
... Monostable multivibrator, 21 to 25 ... BPF (band pass filter), 26,27 ... Spread code generation circuit, 28,3
0 ... Arithmetic circuit (adder), 29 ... Delay circuit, 31 ... Subtractor, 32 ... Comb-shaped filter, 33 ... Control signal detection circuit, 34 ... N multiplication circuit, 36-38 ... Carrier wave regenerator, 42, 43 ... PLL, 44 ... 1/2 divider, In _{1 to} In
₇ ... Input terminal, Out _{1 to} Out ₂ ... Output terminal.

Claims (1)

[Claims] 1. A modulation side is provided with means for inputting an information signal and a first carrier wave to generate a first two-phase PSK signal by multiplication, and for inputting the information signal and a second carrier wave. Second two phases
Means for obtaining a PSK signal, means for inputting a clock signal and generating a spread code signal based on this, the first two-phase PS
Means for obtaining a first spread signal by inputting the K signal and the spread code signal and performing spread by multiplication; and the second two-phase
Means for inputting the PSK signal and the spread code signal and spreading by multiplication to obtain a second spread signal; means for generating a control signal in synchronization with the spread code signal based on the clock signal; Means for inputting the control signal and the second spread signal to obtain a multiplication output signal by multiplication, and means for adding the multiplication output signal and the first spread signal to generate and output a spread spectrum signal And the demodulation side receives the spread spectrum signal,
And means for separating the first spread signal and the multiplication output signal having different spectrum components corresponding to the second carrier wave, and signal processing by inputting the separated first spread signal and multiplication output signal. Means for separating the control signal by the means, means for regenerating a clock signal and a reset signal based on the control signal, and means for generating a spread code signal synchronized with the spread code signal on the modulation side, and the generated A means for obtaining a demodulated two-phase PSK signal by inputting a spread code signal and the first spread signal that has been separated and detected and performing despreading by multiplying both signals, and synchronously detecting the demodulated two-phase PSK signal. Thus, the spread spectrum communication system is characterized in that it is provided with means for demodulating and outputting an information signal equivalent to that at the time of modulation.