JPH048028A - Spread spectrum communication system - Google Patents

Abstract

PURPOSE:To eliminate the need for a PN pattern generating section and a synchronous circuit at a reception side by modulating a PN pattern together with a data subjected to spread spectrum at a transmission side and sending the modulated signal. CONSTITUTION:When a modulation section 2 modulates a data subjected to spread spectrum by a PN pattern at a spread spectrum section 1 at the transmission side, the relevant PN pattern is modulated simultaneously and the result is sent. The demodulation section 3 of the reception side receiving the data demodulates the relevant PN pattern and the data subjected to spread spectrum from the reception data and the transmission data from the transmission side is obtained by allowing an inverse spread spectrum section 4 to apply inverse spread spectrum processing to the data subjected to spread spectrum processing by using the PN pattern. Thus, the inverse spread spectrum is realized at the reception side without needing the PN pattern generating section and the synchronous circuit.

Description

[Detailed Description of the Invention] [Summary] Reducing the circuit scale on the receiving side with respect to the spread spectrum communication method in which transmitting data is spread in a spread spectrum unit according to a PN pattern on the transmitting side, modulated in a modulating unit, and transmitted to the receiving side. With the purpose of is demodulated, and the data that has been spectrum-spread by the demodulated PN pattern is subjected to despreading in a despreading section to obtain the transmission data.

(Industrial Application Field) The present invention relates to a spread spectrum communication system, and more particularly to a direct spread spectrum communication system in which a modulator first spreads the signal using a PN pattern and then modulates the signal, which is then modulated and transmitted to the receiving side.

As one of the data communication methods, the data and P to be sent are
Direct spread spectrum method (Spread 5pectru+s System) that aims to improve confidentiality and avoid interception by multiplying the N (Pseudo No. 1se) code sequence and intentionally widening the band for transmission.
has attracted attention in recent years.

[Conventional technology]

A well-known conventional example of such a spread spectrum communication system is shown in FIG.
1, a PN pattern generation section 52 that supplies a PN pattern to a spread spectrum section 51, and a modulation section 53 that modulates a carrier wave using spread spectrum data and transmits the modulated signal. The spectrum despreading section 54 receiving the spectrum and the spectrum despreading section 5
4, a PN pattern generating section 55 that provides a PN pattern to 4;
a receiver 56 connected to the spectrum despreading section 54;
The synchronization circuit 57 is connected to the receiver 56 and provides a synchronization signal to the PN pattern generation section 55.

In a spread spectrum communication system having such a configuration, transmission data is spread by a spectrum spreader 51 using a PN pattern from a PN pattern generator 52, further modulated by a modulator 53, and then transmitted.

The spectrum despreading section 54 on the receiving side receives this,
Received data is despread using a PN pattern from a PN pattern generating section 55 provided on the receiving side, demodulated by a receiver 56 to obtain received data, and a synchronization circuit 57 generates a PN pattern based on the spectrally despread data. The generator 55 is synchronously controlled.

[Problem to be solved by the invention]

In such a conventional example, when despreading on the receiving side, it is necessary to generate a PN pattern that is synchronized with the PN pattern on the transmitting side.
5 and a synchronous circuit 57, the problem is that the circuit scale becomes large.

Therefore, an object of the present invention is to reduce the circuit size on the receiving side in a spread spectrum communication system in which transmitting data is spread in a spread spectrum section according to a PN pattern on the transmitting side, modulated in a modulating section, and transmitted to the receiving side. do.

[Means and operations for solving the problems] In order to solve the above problems, the spread spectrum communication system according to the present invention is provided with a spread spectrum communication system in which the spread spectrum unit 1 performs PN on the transmitting side, as shown in principle in FIG. When the modulating section 2 modulates the data spread spectrum by the pattern, the PN pattern is also modulated and transmitted at the same time.

On the receiving side that receives this data, the demodulator 3 demodulates the PN pattern and the spread spectrum data from the received data, and the demodulated PN pattern is transmitted to the despreader 4.
Transmission data on the transmitting side can be obtained by performing inverse spectrum spreading on the spread spectrum data.

As a result, spectrum despreading can be realized on the receiving side without requiring a PN pattern generator or a synchronization circuit.

C Embodiment] FIG. 2 shows an embodiment on the transmission side of the spread spectrum communication system according to the present invention.
The modulator 2 is composed of a FOR (exclusive OR) gate 11 for spreading according to a PN pattern from
For example, a BPSK modulation 821 that modulates the carrier wave with the spread spectrum data of the FOR gate 11, and a π/2 phase shifter 2.
The modulator 2 is composed of a BPSK modulator 22 that modulates a carrier wave phase-shifted by π/2 in 3 and a PN pattern, and a hybrid circuit 24 that combines the modulation outputs of the modulators 21 and 22. P on one channel of modulation
This means that N patterns are carried.

FIG. 3 shows an embodiment of the receiving side of the spread spectrum communication system according to the present invention. In this embodiment, the demodulator 3 includes a bandpass filter 30 that extracts only the received signal in a predetermined frequency band. , a carrier wave regeneration circuit 31 that regenerates a carrier wave from the output of the filter 30, a demodulator 32 that demodulates the output of the filter 30 using the regenerated carrier wave, and a phase shifter 34 that shifts the regenerated carrier wave by π/2. A demodulator 33 demodulates the output of the filter 30 using phased signals, and the spectrum despreading section 4 includes a low-pass filter 41.42 that cuts high frequency components of the output of the demodulator 32.33, and Filter 41
．． mixer 4 which despreads the output of one of the outputs of 42 with the output of the other;
It is composed of 3.

Next, the operation of the transmitting/receiving system having such a configuration will be explained.

In spread spectrum communication, the input to the receiving device includes a very large noise component in addition to the signal component, but noise will not be considered in the following explanation.

First, on the sending side, the sending data is transmitted using the PN pattern.
After spreading the spectrum with the OR gate 11, the modulator 21
The QPSK modulated data is transmitted to the receiving side by performing BPSK modulation in the modulator 22 using a PN pattern, and configuring the hybrid circuit 24.

The signal received by the receiving side! (t) is the following formula 0
Formula % A(t): Signal to be transmitted P(t): PN pattern ω: Carrier frequency x 2π where A(t)P(t)sin ωt is the signal component, P
(t) cosot is a PN pattern component.

Here, if the carrier signal regenerated by the carrier regeneration circuit 31 is B sinωt, then the output χI of the demodulator 32, 33
(t) and 2(t) are respectively L(t)=I
(t) x Bs1n ω, ...■
χ, (t) = T (t) x Bcos (L) t
−■ becomes. However, it is assumed that the carrier waves are completely synchronized (frequency ω) on the transmitting side and the receiving side.

Therefore, by substituting the formula ■ into the formulas ■ and ■, X+(t)=A
(t)P(t)sin ωt XBs1n ωt+ P
(t) cos act X Bs1n ωt= A(t
) P (t) B X l/2 (coso-cos2
ω) 10 P (t)B X π/2(sin2 (
11+5 ink)=A(t)P(t)B Xπ/2(1
-CO82 (11) 10P(t)B Xπ/2(sin2
*))Xz(t)=A(t)P(t)sin act
XBcos ωt+ P(t)cos ωt X Bc
os ωt= A ft) P (t) B X 1/
2(sin2<L) +5inO)+P(t)
B X 1/2 (coso-cos2 (Ll)-A
(t)P(t)B Xπ/2(sin2ω)+P(t
) B xi/2 (1-cos2 cc+).

When these signals X + (t) and X z (t) are passed through filters 41 and 42 to cut the 2ω component, x,' (t)-1/2 Aft)P(t)BX,
'(t)=1/2 P(t)B.

Therefore, the output Y (t) via the mixer 43 is y(
t)-x+' (t) -xz' (t)-1/4 A
(t)P(t)"B".

Among these, p (t) is a PN pattern, and P (t)''
is an autocorrelation function, and when the PN pattern that spreads the spectrum of the transmitted data and the PN pattern that is modulated in addition to this pass through the same transmission path, the maximum correlation value is obtained, and despreading is performed. (t) contains the signal component A(
It can be seen that (a constant multiple of t) appears.

That is, if the transmission path is different, the autocorrelation value will be P (11・
P(t-τ) (τ is the transmission path delay and O in the case of the same transmission path
), and since y (g has a smaller value), despreading will not be achieved in this case.

〔Effect of the invention〕

As explained above, according to the spread spectrum communication system according to the present invention, the transmitting side modulates and transmits the PN pattern along with the spectrum spread data, and the receiving side modulates and transmits the PN pattern and the spectrum spread data from the received data. Since the configuration is configured to demodulate the data and inverse spectrum spread the spread spectrum data using the demodulated PN pattern to obtain the transmission data, there is no need for a PN pattern generator and a synchronization circuit on the receiving side. A small circuit scale can be realized.

3... demodulation section, 4...Spectrum despreading section.

In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a spread spectrum communication system in which transmission data is spread in a spectrum spreader (1) according to a PN pattern on the transmitter side, modulated in a modulator (2), and transmitted to the receiver side, from the transmitter side, the spectrum is transmitted. The modulator (2) modulates and transmits the PN pattern along with the spread data, and on the receiving side, the demodulator (3) demodulates the PN pattern and the spread spectrum data from the received data, and the demodulator A spread spectrum communication system characterized in that the spread spectrum data is spread spectrum-inversely in a despreading section (4) to obtain the transmission data according to the PN pattern.