JPH09116460A - Transmitter and receiver for spread spectrum communication and spread spectrum communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of data transmission and to receive data very approximating transmitted data. SOLUTION: The signal obtained by modulating a carrier wave 2 by an information signal in a primary modulator 1 is supplied to a secondary modulator 3. The spread signal from a spreading code generator 4 is supplied to the secondary modulator 3, and the signal from the primary modulator is modulated to the spread signal in the secondary modulator 3 by this spread signal, and this modulated spread signal is inputted to a spread duplexing part 5 and is duplexed and is transmitted from an antenna 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication transmitter and receiver, and a spread spectrum communication device, which employ a double spread method.

[0002]

2. Description of the Related Art Spread spectrum communication is a medium speed wireless LA.
In wireless data communication such as N, it is used for modulation when transmitting data from a transmitting side to a receiving side, and is currently most often used in a modulation system such as a medium speed wireless LAN.
This communication system has been applied to cellular phones (car phones) and PCNs (cell phones) in the United States and other countries, together with the remarkable progress of hardware technology.

The current spread spectrum communication technology is
When transmitting the data, the transmission is performed by spreading the data into a wider bandwidth shown in FIG. 4 (b) than the required bandwidth of the transmission desired band signal shown in FIG. 4 (a), and performing reverse mapping on the receiving side. To obtain the desired signal.

[0004]

From the beginning, the spread spectrum communication system is said to be strong against strong confidentiality, interference and interference. Certainly, the spread spectrum communication system, as the name suggests, is a technology that restores the desired signal by mapping the signal to a band that is much wider than the bandwidth required to transmit information. Is rich.
However, after receiving the desired signal as shown in FIG. 5A, it is converted into the despread signal shown in FIG. 5B and the demodulated signal shown in FIG. 5C is obtained through a filter or the like. However, the interference wave shown by the shaded area in FIG. 5A is received overlapping the desired signal, and after being converted into a despread signal as shown in FIG. 5B, the demodulated signal shown in FIG. , The signal does not necessarily match the signal at the time of primary modulation. This is because the interference wave (noise) is not completely removed, but the BER (Bit Error Rat) of the data.
Considering from e), it becomes a problem at the time of wireless data communication.

The present invention has been made in view of the above circumstances, and is highly confidential and disturbing, improves the reliability of data transmission, and receives data very close to the transmitted data. An object of the present invention is to provide a transmitter and a receiver for spread spectrum communication and a spread spectrum communication device that can be used.

[0006]

According to the present invention, in order to solve the above problems, the transmitter of the first invention modulates a carrier wave with an information signal by a primary modulator. The signal modulated here is a spread signal from the spread code generator and is modulated by the secondary modulator. The spread signal is equally divided so that the total power spectrum density is divided into two equal densities, and is doubled by the spread doubler and radiated from the antenna.

In the receiver of the second invention, the spread signal received by the first and second receiving antennas and divided into two parts is divided into first and second RF filters. Feed to mixer 2. A despreading signal is applied to these mixers from the despreading code generator, and then supplied to the first and second bandpass filters. These bandpass filters have 2
If there is a noise signal in one of the equally divided spread signals, that signal is not selected. The selected signal is synchronized with the transmission signal and the synchronized output signal is given to the despreading code generator. The selected signal is also provided to the demodulator and demodulated.

According to a third aspect of the invention, after the spread signal divided into two equal parts from the transmitter of the first aspect of the invention is received by the receiver of the second aspect of the invention and a mixed output of the despread signal and the received signal is obtained, It is a spread spectrum communication device that prevents a spread signal having a noise signal from being selected when there is a noise signal in one of the spread signals bisected by a bandpass filter.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram of the main part on the transmitter side according to an embodiment of the present invention. In FIG.
Is a primary modulator, which modulates a carrier wave 2 with an information signal and supplies a signal to a secondary modulator 3. The spread signal from the spread code generator 4 is supplied to the secondary modulator 3,
With this spread signal, the signal from the primary modulator 1 is modulated by the secondary modulator 3 into a spread signal, and the spread signal is equally divided so that the total power spectrum density becomes equal to two. The spread signal is input to the spread / duplicate unit 5, where the spread signal is doubled and radiated from the antenna 6.

FIG. 2 is a block diagram of the main part on the receiver side according to the embodiment of the present invention. In FIG.
Reference numeral 1B is an antenna dedicated to spread signal A and spread signal B. Received signals received by these antennas 11A and 11B are transmitted to the first and second mixers 13A and 13B via the first and second RF filters 12A and 12B. Is entered. The despread signal from the spreading code generator 14 is supplied to these mixers 13A and 13B, and these mixers 13A and 13B are supplied.
The received signal is then mixed with the despread signal. First Mixer-1
The output of 3A is the first bandpass filter (BPF) 15A.
In addition, the output of the second mixer 13B is input to the second bandpass filter (BPF) 15B, respectively, and only the one received signal of the spread signals A and B is selected by the first and second BPFs 15A and 15B. . First and second BPF15
The signal selected by A and 15B is demodulated by the demodulator 16 to obtain an information signal. The signals of the first and second BPFs 15A and 15B are supplied to the synchronizing circuit 17, and the output of this synchronizing circuit 17 is supplied to the spread code generator 14. The received spread signal is synchronized with the despread signal from the spread code generator 14.

The synchronization circuit 17 is provided for the following reason. A signal subjected to the spread spectrum method becomes a wideband signal which is difficult to receive by a general receiver. Even for a receiver that should originally receive the signal, it is very difficult to properly demodulate the target signal. If the third party who does not know the spread code sequence has difficulty in intercepting the signal, the main reason why the spectrum signal is difficult for the original receiver to receive is that the power spectrum density of the signal is extremely low. That is, since the S / N ratio at the receiver input end is extremely low, proper reception timing cannot be detected from the reception signal by the usual method. If the S / N ratio is not actually high to some extent, it is difficult to receive with few errors even if the synchronization is successfully established. As a result, in the spread spectrum system, a high speed and wide band signal is received with a low power spectrum density such that it is buried in noise, so that a synchronizing circuit is required.

Next, the operation of the above embodiment will be described. FIG.
In the transmitter shown in FIG. 3, the output side of the primary modulator 1 is shown in FIG.
A narrow band signal of spectrum E as shown in (a) is obtained. This signal is spread-modulated by the spread signal in the secondary modulator 3, and then the spread modulation is duplicated into a spread signal as shown in FIG. 3 (b). After that, the spread signal is shown in FIG.
As shown in (c), the transmission signal is divided into two equal parts (total electric power is divided into two equal parts) based on the center frequency and transmitted from the antenna 6.

The transmitted signal is received by the receiver shown in FIG. At this time, when an interference wave (noise indicated by diagonal lines in the figure) arrives at the reception signal as shown in FIG. 3D, the reception signal and the interference wave pass through the first RF filter 12A and then pass through the first RF filter 12A.
When mixed with the spread signal in the mixer-13A, FIG.
The signal has a waveform as shown in. This signal is the first BPF
In FIG. 3 (f), the one without the interference wave is selected in 15A, and the spectrum E is adjusted by the demodulator 16 so that it becomes the same as the original information signal.
Is doubled. The signal at this time is shown in FIG. Although the above description is for the case of the spread A of the duplicated spreads A and B, the same operation is performed in the spread B, and the spread A
Even if it becomes impossible to receive, the process of reception is performed by the spread B.

[0014]

As described above, according to the present invention,
In addition to being highly confidential and disturbing, there are advantages that the reliability of data transmission is improved and that data that is extremely close to the transmitted data can be received.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a transmission side according to an embodiment of the present invention.

FIG. 2 is a block configuration diagram of a receiving side according to the embodiment of the present invention.

FIG. 3 is a waveform explanatory diagram for describing the operation of the embodiment of the present invention.

FIG. 4 is an explanatory diagram of waveforms for describing spectrum communication technology.

FIG. 5 is an explanatory diagram of waveforms when an interference wave acts on a received signal.

[Explanation of symbols]

 1 ... Primary modulator 2 ... Carrier wave 3 ... Secondary modulator 4, 14 ... Spreading code generator 5 ... Spreading duplication unit 12A, 12B ... RF filter 13A, 13B ... Mixer 15A, 15B ... BPF 16 ... Demodulator 17 ... Synchronous circuit

Claims (3)

[Claims] 1. A primary modulator which modulates a carrier wave with an information signal, and a secondary modulator which is supplied with a signal modulated by this primary modulator and modulates this signal with a spread signal from a spread code generator. And a spread doubler that doubles the spread signal modulated by the secondary modulator so that the total power spectral density is divided into two equal densities and radiates from the antenna. Spread spectrum communication transmitter. 2. A first and a second receiving antenna for receiving a spread signal which is duplicated and bisected, and a first which receives a signal received by these antennas and obtains a necessary signal. A second RF filter, a despreading code generator for generating a despreading signal mixed with signals output from these filters, and a signal obtained by mixing the filter output signal and the despreading signal, respectively. 1st, 2nd
A band-pass filter, a synchronizing circuit which is supplied with output signals from these band-pass filters, synchronizes the output signal with the transmission signal, and gives the synchronized output signal to a despreading code generator, A receiver for spread spectrum communication, comprising: a demodulator that obtains a demodulated signal from an output signal of a second bandpass filter. 3. A primary modulator that modulates a carrier wave with an information signal, a secondary modulator that is supplied with a signal modulated by this primary modulator, and that modulates this signal with a spread signal from a spread code generator, A transmitter having a spread doubler that doubles the spread signal modulated by the secondary modulator so that the total power spectrum density is divided into two equal densities and radiates from the antenna; First and second receiving antennas for receiving the radiated spread signal, first and second RF filters to which the signals received by these antennas are supplied to obtain a necessary signal, and signals output from these filters Despreading code generators for generating mixed despreading signals, first and second bandpass filters for respectively passing signals obtained by mixing the filter output signal and despreading signal, and these bandpass filters From the output signals of the first and second band pass filters, to which the output signal from the digital signal is supplied, and which synchronizes the output signal with the transmission signal and gives the synchronized output signal to the despreading code generator. A spread spectrum communication device, comprising: a receiver having a demodulator for obtaining a demodulated signal.