JPH0746154A - Spread spectrum modulator and/or demodulator - Google Patents

Abstract

PURPOSE:To improve the synchronization holding operation or the like in SS demodulation. CONSTITUTION:An SS modulator 11 is provided with a spread code generator (PNG), a delay means 4 which delays the spread code from the PNG by P time tau, a spread modulation means X1 which subjects information to spread modulation by the delay spread code, a first, carrier modulation means X2 which modulates the spread modulation output by a first carrier signal, a second carrier modulation means X3 which modulates the spread code by a second carrier signal, and an adder SIGMA1 which adds first and second carrier modulation signals to output a composite spread spectrum modulation wave signal, and an SS demodulator 20 is provided with a VCA 23 which performs the gain control of the inputted composite SS modulation wave signal, a comb line filter 24 which separates the output signal from the VCA 23 into first and second carrier modulation signals, a DLL 26 which takes the second carrier modulation signal as the input to hold the synchronism and generates a control signal to the VCA 23, and an inverse spread demodulation means X4 which subjects the first carrier modulation signal to inverse spread demodulation by the spread code from a PNG in the DLL 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum modulation and / or demodulation device, and in particular, in spread spectrum demodulation, stable synchronization can be maintained even under weak input and S / N.
Of the spread spectrum modulation and / or demodulation device capable of performing good despread demodulation.

[0002]

[Technical background] Spread spectrum (hereinafter referred to as "SS")
While the commercialization of communication systems has been recently promoted in various fields, not only the pursuit of improving the technical level in each application field, but also the research to further improve the basic performance of SS system is continued. ing. Among them, the pursuit of maximizing the SS synchronization holding capability is a theme that cannot be overlooked, and is also the object of the present invention. This research and development is SS
This is a highly anticipated theme because it can surely improve the basic performance of the method.

[0003]

2. Description of the Related Art A DLL (Delay Lock Loop) type synchronization holding device provided on the demodulation side in the SS (communication) system is
This device is basically necessary for SS demodulation, and its synchronization holding performance is C / N (carrier power and carrier power) in the despreading demodulation frequency bandwidth (arm filter transmission bandwidth) found by the information rate of the input SS signal. It is almost determined by the noise power ratio).

That is, the error component of the loop is detected from the despreading output (correlation detection output) from the correlator included in the DLL-type synchronization holding device through the arm filter that transmits only the required information band, so that the information rate The higher the value, the wider the information pass band of the arm filter, resulting in C / N
Therefore, the SS synchronization holding performance is deteriorated. That is, the SS synchronization holding performance depends on the information speed. As described above, the synchronization holding performance in the SS system is determined by the process gain Gp of the SS system in principle. Gp
Is calculated by the following equation from the frequency bandwidth BW of the SS signal and the information rate Ri. Gp = BW / Ri …………………… (1)

[0005]

Since the sync holding performance of the sync holding device in the conventional SS demodulator does not exceed the process gain Gp of the SS system, the lower the level of the input SS signal, the lower the C / N ratio. As the correlation noise level due to the noise N including the downlink and interference waves approaches the despreading output level, it becomes difficult to maintain the synchronization holding operation, out of synchronization occurs, and SS demodulation stops. Even within the synchronization maintaining range, there is a limit in basic performance such that the S / N of the demodulated signal in SS demodulation is deteriorated due to the increase in the jitter of the spread code due to the correlation noise. Therefore, the appearance of a device capable of improving the SS synchronization maintenance as compared with the conventional one is desired.

[0006]

In order to solve the above-mentioned problems, the present invention firstly requires that an SS modulator receives a clock signal and generates a first spread code, and a spread code generator (3).
The delay means (4) for delaying the spread code by τ time to obtain the second spread code, the spread modulator (multiplier X1) for spread-modulating the information signal with the second spread code, and the spread modulator First carrier modulation means (multiplier X2) for modulating the spread modulation output with the first carrier signal, and second carrier modulation means (multiplier X3) for modulating the first spread code with the second carrier signal. And addition means (adder Σ1) for adding the first and second carrier modulation signals respectively obtained by the first and second carrier modulation means and outputting a composite spread spectrum modulated wave signal. There is.

On the other hand, the SS demodulator receives the composite spread spectrum modulated wave signal from the spread spectrum modulator and adjusts the gain to a level within a predetermined range by an automatic gain control circuit (23).
A comb-tooth filter (24) for separating the output signal from the automatic gain control circuit into the first carrier modulation signal and the second carrier modulation signal, and the separated second carrier modulation signal. A first carrier modulation signal is generated by using a synchronization holding circuit (26) which performs synchronization holding and generates and supplies a control signal to the automatic gain control circuit, and a demodulation spreading code obtained by the synchronization holding circuit. It comprises at least a despread demodulation means (multiplier X4) for despread demodulation.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the SS modulation and / or demodulation device of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an SS modulator 10 according to the present invention,
In the figure, 3 is a spread code generator, 4 is a delay circuit, and X1 to X3.
Is a multiplier (correlator), Σ1 is an adder, ψ1 is a BPF (bandpass filter), and A1 is a transmission antenna.

In the SS modulator 10 having the above structure,
The information d (t) is supplied to the spreading modulation multiplier X1 from an information source (not shown) via the information input terminal In1. On the other hand, the clock signal C (t) is supplied from the clock generator (not shown) to the spread code generator 3 via the input terminal In2, where the spread code P (t) is generated to generate the multiplier X3 and the delay circuit 4. Is being supplied to. The delay time τ of the delay circuit 4 is
It is selected from the chip rate of the spread code and is determined within the spread code length (spread code period) L. From the delay circuit 4, P
The spreading code (t-τ) is output and supplied to the multiplier X1 where the information d (t) is spread-modulated and d (t) P (t-τ)
The spread modulation signal is output to the multiplier X2.

Further, the first carrier signal cosω ₁ t from a carrier signal generator (not shown) is input from the input terminal In3.
Is supplied to the multiplier (mixer) X2, the multiplier X
SS modulated wave signal S ₁ which is a mixing output signal from 2
(t) becomes S ₁ (t) = P (t−τ) d (t) cosω ₁ t …………………… (2). That is, this is a two-phase PSK (Phase
shift keying) modulation.

That is, the multiplier X3 receives the second carrier signal from the carrier signal generator (not shown) from the input terminal In4.
The cos ω ₂ t is supplied and multiplied with the spreading code P (t). Therefore, the code-modulated wave signal S ₂ (t), which is the multiplication output signal, becomes S ₂ (t) = P (t) cosω ₂ t …………………… (3), and is added to the adder Σ 1. The SS modulated wave signal S ₁ (t) is supplied and added together. As a result, the addition output signal becomes the composite SS modulated wave signal S (t) as expressed by the following equation.

S (t) = P (t−τ) d (t) cosω ₁ t + P (t) cosω ₂ t (4) It should be noted that each carrier frequency in both carrier signals cosω ₁ t and cosω ₂ t f ₁ and f ₂ (ω ₁ = 2πf ₁ , ω ₂ =
2πf ₂ ) is the difference between the clock fundamental frequency C of the spread code
_The frequency is determined by dividing _F by the spreading code length L. That is, f ₂ −f ₁ = C _F / (2L) …………………… (5). As a result, the frequency spectrum of the composite SS modulated wave signal S (t) becomes as shown in FIG. 4, and the composite SS modulated wave signal S (t) is transmitted from the transmission antenna A1 via the BPF (bandpass filter) ψ1. Is output. In addition, in FIG.
(II) shows the main lobe, and FIG. (I) shows the main part in an enlarged manner. Also, in Fig. 1 (I), −Sc _n,
Sc _n is the spectrum of the code-modulated wave signal S ₂ (t), −Sd _n, Sd
_n is the spectrum of the SS modulated wave signal S ₁ (t) (both n
Is an integer).

Next, an embodiment of the SS demodulator according to the present invention will be described with reference to FIG. 2 is S
FIG. 2 is a block diagram of the S demodulator 20, in which A2 is a receiving antenna, ψ2 and ψ3 are BPFs, 23 is a voltage control amplifier (VCA), 24 is a comb-tooth filter (CF), and 26 is D.
LL (delay lock loop) type synchronization hold circuit, 5 time delay circuit (delay amount = τ), 28 response time constant circuit, X4 multiplier (correlator), 30 primary demodulation such as two-phase PSK demodulation It is a primary demodulation circuit for performing.

The delay circuit 5 uses a spreading code for despreading demodulation,
It is a circuit for matching the temporal timing with the spreading code for spreading modulation on the side of the modulator. An ordinary SS communication device includes both the SS demodulation device 20 and the SS modulation device 10 shown in FIG. 1, and therefore the spreading code generator 3 in FIG. 1 and the spreading code generator 51 described later are included. , And the antennas A1 and A2 are used in common.

FIG. 3 shows a DLL type synchronous holding circuit (hereinafter referred to as "DL
It is abbreviated as L ″) 26. In the figure, X5 and X6 are multipliers, ψ4 and ψ5 are BPFs (arm filters), Σ2 is an adder, Σ6 is a subtractor, and 46 and 4
7 is an envelope detection circuit, 49 is a loop filter (LF),
Reference numeral 50 is a VCO (voltage controlled oscillator), and 51 is a spread code generator.

FIG. 5 shows the comb-tooth filter 2 in FIG.
4 is a circuit (block) diagram showing an example of a specific configuration of 4, in which 6 is a delay circuit for delaying one cycle time (code length) of the spread code τ _P , Σ 3 is an adder, and Σ 7 is It is a subtractor.

In the SS demodulation device 20 having such a configuration,
The composite SS modulated wave signal received from the receiving antenna A2 is transmitted through the BPF ψ2 to the VCA which is an automatic gain control circuit.
The voltage is supplied to the (voltage control amplifier) 23, where the amplitude of the composite SS modulated wave signal is controlled to be substantially constant. The gain-controlled composite SS modulated wave signal S (t) is output to the comb filter 2
4 to separate the signals.

Here, the specific operation of the comb filter 24 will be described with reference to FIGS. 5 and 6. Figure 6
Is the filtering characteristic of the circuit of FIG. In addition,
The composite SS modulated wave signal from the VCA 23 is applied to the input terminal In6, but the input signal will be described as sinωt for convenience.

The input signal sinωt is supplied to the adder Σ3 and the subtractor Σ7 (positive input terminal) and is delayed by τ _{P in the} delay circuit 6 to become sin ω (t−τ _P ). It is supplied to the adder Σ3 and the subtractor Σ7 (negative input terminal). Therefore, the output of the adder Σ3 is | cos (ωτ _P / 2) |
And the waveform becomes as shown in FIG. On the other hand, the subtractor Σ7
The subtraction force at is | sin (ωτ _P / 2) |
It becomes the waveform of (C).

When the composite SS modulated wave signal S (t) is supplied to the comb-tooth filter 24 having such a transfer characteristic, the delay circuit 6
Output (B) is S (t−τ _P ) = P (t−τ−τ _P ) d (t−τ _P ) cosω ₁ (t−τ _P ) + P (t−τ _P ) cosω ₂ (t −τ _P ) ………………………… (6). Here, since the delay time of τ _P is one cycle time of the spread code, the carrier signal cosω ₂ t becomes in opposite phase at τ _P , and the delayed composite SS modulated wave signal S (t−τ _P ) becomes S (t −τ _P ) = P (t−τ) d (t−τ _P ) cosω ₁ t−P (t) cosω ₂ t ... (7)

Therefore, the output signal S (t) + S of the adder Σ3
(t−τ _P ) is S (t) + S (t−τ _P ) = 2P (t−τ) {d (t) + d (t−τ _P )} cosω ₁ t (8), Subtraction signal S (t) -S (t- from subtractor Σ7
τ _P ) is S (t) −S (t−τ _P ) = 2P (t) cosω ₂ t− {d (t) -d (t−τ _P )} P (t−τ) cosω ₁ t ... ... (9). Here, if {d (t) -d (t-τ _P )} << 1,
S (t) -S (t- τ P) is equal to approximately the 2P (t) cosω ₂ t.

In this way, the composite SS modulated wave signal S (t) is output from the comb tooth filter 24 as the SS modulated wave signal S ₁
(t) and the code-modulated wave signal S ₂ (t) are separated and output. Note that the information component {d (t) + d (t-
τ _P )} appears to be slightly deformed compared to the original information d (t), but if the delay time τ _P is selected shorter than the 1-bit time of the information, the original information d (t) Can be approximated.

By the way, the comb-tooth filter is not limited to the configuration shown in FIG. 5, but if the selectivity characteristic of the filter is to be sharpened, it is constructed as shown in the circuit (block) diagram of FIG. In FIG. 7, reference numeral 7 is a delay circuit having a delay time τ _P , K is an attenuator, and Σ4 and Σ5 are both adders. The filtering characteristic when the coefficient k of the attenuator K is 0.9 is shown in FIG. When the cyclic comb-tooth filter 24 'having such a configuration is used to detect the code-modulated wave signal S ₂ (t), noise components and interference components mixed in the band are detected as shown in FIG.
It becomes possible to remove considerably compared with the characteristic of. In FIG. 8, (a) is a logarithmic scale and (b) is a linear scale on the vertical axis. The code-modulated wave signal S ₂ (t) separated in this way is supplied to the DLL (delay lock loop) 26 in FIG.

Next, concrete signal processing in the DLL 26 will be described with reference to FIG. The code modulated wave signal S ₂ (t) is input from the comb filter 24 to the input terminal In 4
Is supplied to the correlation multipliers X5 and X6. On the other hand, P
From NG (spreading code generator) 51, multiplier X5 has Δ / 2
The spread code P (t-τ ₀ + Δ / 2) advanced in time is multiplied by the multiplier X6.
Are supplied with spread codes P (t−τ ₀ −Δ / 2) delayed by Δ / 2 time (where τ ₀ is an estimated amount of delay time with respect to the spread code P (t) on the transmitting side. }. Multipliers X5 and X
The correlation (multiplication) outputs of 6 are respectively Rp (τ ₀ −Δ / 2) cosω ₂
t and Rp (τ ₀ + Δ / 2) cosω ₂ t, respectively, and the BPF
It is supplied to ψ4 and ψ5.

Since the correlation output signals supplied to the BPFs ψ4 and ψ5 have only carrier signal components and no information components, a bandpass filter having a narrow bandpass characteristic can be used as the BPFs ψ4 and ψ5. The correlation output components transmitted through these BPFs φ4 and φ5 are supplied to envelope detection circuits 46 and 47, respectively, and the correlation output, that is, the envelope of the carrier signal is detected.
Further, the outputs of both envelopes are supplied to the positive and negative input terminals of the subtractor Σ6 and converted into an error signal (difference signal) E (τ).

Therefore, this error signal E (τ) is (τ ₀ −
It becomes a component of the difference between Δ / 2) and (τ ₀ + Δ / 2), and V is passed through a loop filter (LF) 49 that removes a noise component.
It is supplied to a CO (voltage controlled oscillator) 50 and controls its oscillation frequency (changes according to the level). Then, the oscillation output of this VCO 50 is transmitted to a PNG (spread code generator).
Reference numeral 51 is input as a clock signal to generate three kinds of spread codes P (t−τ ₀ ), P (t−τ ₀ −Δ / 2) and P (t−τ ₀ + Δ / 2). The second and third spreading codes are respectively multiplied by a multiplier X.
Output to 5 and X6.

That is, the above LF49, VCO50, PN
G51, multipliers X5, X6; BPF ψ4, ψ5; envelope detection circuits 46, 47 and subtractor Σ6 form a delay locked loop which is a loop of negative feedback circuit, and its autocorrelation is shown in FIG. The function characteristics are shown.

The spread code P (t-τ from the PNG 51 is also used.
₀ ) is output to the delay circuit 5 of FIG. 2, where it is delayed by τ to become P (t−τ ₀ −τ), which is then applied to the despreading demodulator multiplier X 4 and the comb filter. SS from 24
It is supplied with the modulated wave signal S ₁ (t). Therefore, the despread output S _D (t) from the multiplier X4 is S _D (t) = Rp (τ ₀ ) {d (t) + d (t−τ _P )} cosω ₂ t. (10), and after unnecessary frequency band components are removed by BPF ψ3, it is supplied to the primary (two-phase PSK) demodulation circuit 30, demodulated here, and demodulated information {d (t) -d (from the output terminal Out1. t
−τ ₀ )} is output.

Next, the operation of generating the automatic gain control signal for supplying the control signal to the VCA (voltage control amplifier) 23 will be described with reference to FIG. 2, FIG. 3 and FIG. First, the output of the VCA 23 is separated by the CF 24 as described above and supplied to the multipliers X5 and X6 via the subtractor .SIGMA.7 of FIG. 5 and the input terminal In4 of FIG. In both multipliers X5 and X6, the two kinds of spread codes (a) from the PNG51, as described above,
In (b), the correlations are respectively obtained, and further, desired frequency components are selectively transmitted by the BPFs φ4 and φ5, and the envelope detection circuits 46,
It is supplied to 47 to detect the envelope of the carrier signal.

The above circuit operation is the same as the process of generating the error signal E (τ), but the detected outputs of the envelope detection circuits 46 and 47 are added by the adder Σ 2 this time, and the envelope added signal is added. This is output to the response time constant circuit 28 via the output terminal Out2, where an appropriate response time constant is given and supplied to the VCA 23 for automatic gain control. The envelope detection output naturally increases when the reception level is strong, and decreases when the reception level is weak. Such high and low reception levels
The VCA 23, the comb filter 24, the DLL 26, and the response time constant circuit 28 are controlled by an automatic gain control loop.
The output of is controlled to be almost constant. Therefore, DL
Not only the operation of L26 is stabilized, but the amplitude of the despread output becomes almost constant, and the two-phase PSK signal can be demodulated stably.

As is apparent from the above description, in the conventional apparatus, the information-modulated SS signal is supplied to the DLL 26 for synchronization acquisition & holding. this is,
This is because only the SS-modulated wave signal in which the information signal is spread-modulated (that is, the spread code subjected to information modulation) is output on the transmitting side. On the other hand, in the device of the present invention, a code-modulated wave signal S ₂ (t) obtained by modulating a spread code which is not information-modulated by the second carrier is generated by the first carrier (2nd order).
It is output after being combined (frequency division multiplexed) with the SS modulated wave signal S ₁ (t) that has been phase PSK modulated.

Then, the composite SS modulated wave signal S (t)
Is separated by the comb-tooth filter 24 on the receiving side, and the code-modulated wave signal S ₂ (t) is supplied to the DLL 26. As a result, the noise component is also suppressed in the comb-tooth filter 24, and the stability of the DLL operation is significantly improved. Furthermore, FIG.
You can also use a sharp filter like the one shown in
In that case, a further noise suppression effect can be obtained.

This is because, in principle, the synchronization holding performance in the SS system is the process gain Gp in the code modulated wave signal.
, The process gain Gp is BW / Ri as shown in the equation (1), and this information rate Ri becomes almost zero in the device of the present invention, so Gp becomes very large. The ability to suppress noise is also improved. Therefore, even if the synchronization cannot be maintained at the time of weak input, the DLL 26 in the device of the present invention can stably maintain the synchronization. Moreover, since the spreading code for despreading also has less jitter than the conventional example, the noise level of despreading output also decreases.

Moreover, since the frequency bands of the SS modulated wave signal S ₁ (t) and the code modulated wave signal S ₂ (t) do not overlap as shown in FIG. 4, the frequency band of the noise component is also the comb filter 24. Will be separated to some extent. Further, since the spreading code used for the SS modulated wave signal S ₁ (t) has a time shift of τ time from the spreading code used for the code modulated wave signal S ₂ (t), noise is generated in the despreading operation. The correlation is random, so that the noise suppression effect is improved also in this respect.

Since the code-modulated wave signal S ₂ (t) supplied to the DLL 26 does not contain an information signal component, the BPF used in the output stage of the multipliers X5 and X6 for correlation.
A narrow band characteristic can be used for (arm filter),
This significantly improves the C / N of the filter output. Further, since the control signal for the VCA 23 uses the envelope detection output from the DLL 26 in which the noise is significantly suppressed, the problem that the gain control malfunctions due to the noise mixed in during the transmission is significantly improved.

[0036]

Since the SS modulation and / or demodulation device of the present invention is constructed as described above, it has various excellent features as follows. Since the spread signal supplied to the DLL is a code modulated wave signal, it does not include an information signal component. Therefore, a BPF having a narrow band characteristic can be used in the latter stage of the correlation multiplier, and the C / N of the filter output is significantly improved. Since the comb-teeth filter is used in the preceding stage of the DLL, the noise component is suppressed also here, the stability of the synchronization holding in the DLL is significantly improved, and the weak input that makes the synchronization holding difficult in the conventional example. Even in time, it is possible to stably maintain synchronization. Therefore, the jitter included in the spreading code for despreading is also reduced as compared with the conventional example, and low-noise despreading output can be obtained.

The control signal for the automatic gain control circuit uses the envelope detection output in which the noise is greatly suppressed by the BPF having the narrow band characteristic, so that the noise may be mixed into the gain control so that the gain control may malfunction. This problem is also greatly improved. Since the frequency bands of the SS modulated wave signal S ₁ (t) and the code modulated wave signal S ₂ (t) are slightly shifted, the noise frequency is separated to some extent, and the spread code for the SS modulated wave signal is code modulated. Since it is shifted by τ time from the spreading code for the wave signal, the noise correlation becomes random in the despreading operation, and the noise suppression effect is enhanced. Since the comb-teeth filter used in the input stage of the DLL detects a code-modulated wave signal having no information component, a comb-teeth filter having a sharp characteristic as shown in FIG. 8 can be used. Noise suppression effect can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an SS modulator of the present invention.

FIG. 2 is a block configuration diagram showing an embodiment of an SS demodulation device of the present invention.

FIG. 3 is a specific block diagram of a DLL that constitutes the SS demodulation device of the present invention.

FIG. 4 is a composite SS output from the SS modulator of the present invention.
The spectrum figure of a modulated wave signal.

FIG. 5 is a specific circuit diagram showing an example of a comb filter that constitutes the SS demodulator of the present invention.

6 is a filtering characteristic diagram for explaining the operation of the comb-teeth filter of FIG.

FIG. 7 is a specific circuit diagram showing another example of the comb-teeth filter that constitutes the SS demodulator of the present invention.

8 is a filtering characteristic diagram for explaining the operation of the comb tooth filter of FIG.

FIG. 9 is an autocorrelation characteristic diagram for explaining synchronization holding operation in the SS demodulation device of the present invention.

[Explanation of symbols]

 3,51 PNG (spreading code generator) 4-7 Delay circuit 10 SS modulator 20 SS demodulator 23 VCA (voltage control amplifier) 24,24 'Comb filter (CF) 26 DLL (delay lock loop) type synchronization hold Circuit 28 Response time constant circuit 30 Primary demodulation circuit 46, 47 Envelope detection circuit 49 Loop filter (LF) 50 VCO (voltage controlled oscillator) ψ1 to ψ5 BPF (bandpass filter) K attenuator X1 to X6 multiplier (correlation) Σ1 to Σ5 adder Σ6, Σ7 subtractor

Claims (4)

[Claims] 1. A spread code generator for inputting a clock signal to generate a first spread code, delay means for delaying the first spread code by .tau. Time to obtain a second spread code, and the delay means. Spreading modulation means for spreading and modulating an information signal with a spreading code of 2;
First carrier modulation means for carrier-modulating the spread modulation output output by the spread modulation means with a first carrier signal, and second carrier modulation for carrier-modulating the first spread code with a second carrier signal. Means and the first carrier modulation signal obtained by the first carrier modulation means and the second carrier modulation signal obtained by the second carrier modulation means are added to form a composite spread spectrum modulated wave signal. A spread spectrum modulator comprising an adding means for outputting. 2. A spread spectrum demodulator for inputting and demodulating a composite spread spectrum modulated wave signal from the spread spectrum modulator according to claim 1, wherein the composite spread spectrum modulated wave signal is gained to a level within a predetermined range. An automatic gain control circuit for adjusting, a comb-teeth filter for separating an output signal from the automatic gain control circuit into the first carrier modulation signal and the second carrier modulation signal, and the separated second carrier modulation signal. A synchronization holding circuit for inputting a signal to hold the synchronization and generating and supplying a control signal to the automatic gain control circuit, and a demodulation spread code obtained by the synchronization holding circuit Spread spectrum demodulation device comprising at least despread demodulation means for performing despread demodulation on the carrier modulated signal. 3. A synchronization holding circuit in a spread spectrum demodulating apparatus according to claim 2, wherein a spread code generator for generating a third spread code, a fourth spread code and a fifth spread code for despreading, and the second spread code generator.
Of the carrier modulation signal of (1), and the first and second correlation multipliers that carry out correlation detection by the third and fourth spreading codes, and are output from the first and second correlation multipliers, respectively. First and second bandpass filters for selectively transmitting specific frequency components of the first and second correlated output signals, and envelopes of the output signals of the first and second bandpass filters, respectively. First and second envelope detection circuits for line detection, a subtractor for subtracting the obtained envelope detection outputs, a loop filter for converting the output of the subtractor into an error signal, and the obtained error signal Voltage control oscillator for generating a signal having a frequency corresponding to the voltage of 3 and supplying it to the spread code generator as a clock signal, and both envelope detection outputs are added to form a control signal to the automatic gain control circuit. And a spread spectrum demodulation device including an adder. 4. A spread spectrum modulation / demodulation device comprising the spread spectrum modulation device according to claim 1 and the spread spectrum demodulation device according to claim 2 or 3.