JPS58197934A - Spread spectrum transmitter and receiver - Google Patents

Abstract

PURPOSE:To realize a code multiplex, by giving a delay to a pseudo noise code, which modulates two carriers, by means of a transmitter, and correcting the delay by means of a receiver to change the amount of delay. CONSTITUTION:At a transmitter, a pseudo noise (PN) code, which modulates the carrier of frequency f2, is delayed by n bits by delay elements 21 and 22 and supplied to a balanced modulator 4. On the other hand, the carrier of frequency f1 is modulated 3 by a signal added 1 by the PN code and transmission data, and the two carriers are coupled by a directional coupler 7 to be sent from a transmission antenna 8. At a receiver, spread spectrum (SS) modulation waves of the central frequencies f1 and f2 are picked up by BPFs 10 and 11 and converted to IF signals by frequency mixers 25 and 26. At this stage, the IF signal modulated by the PN code, which is not delayed by the transmitter, is inputted to delay elements 23 and 24 to give them the same delay as those of elements 21 and 22 so that the PN codes in the two IF signals are attained to the same phase. These signals are correlated by a balanced modulator 12 to modulate 13 them.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spread spectrum transmitter/receiver, and more particularly to a configuration that enables code multiplexing in a spread spectrum transmitter/receiver that transmits a reference pseudo-noise code.

Spread spectrum (hereinafter abbreviated as SS) technology is a communication method that transmits and receives by spreading the carrier wave spectrum over a wider frequency band than the spectrum of the transmitted data signal.
Conventional communications differ in that pseudo-noise codes (hereinafter abbreviated as PN codes) are used to amplify the spectrum on the transmitting side and perform reverse amplification (or correlation) on the receiving side. This is a different point. S.S.
Characteristics of the communication signal system include the ability to perform selective calling and multiple access due to the strong autocorrelation of the PN code, the ability to avoid interception due to signal secrecy, and resistance to interference. . - In order to use the PN code, a wide frequency range is required, and the PN code must be synchronized (the timing of the PN code is matched between the transmitter and the receiver). In particular, since the structure of the PN code synchronization I''i receiver is complicated, various measures have been taken to eliminate this drawback, and the standard PN code transmission method (% & 5ons, ) is one of these methods. This method will be explained using drawings.

FIG. 1 shows an SS transmitter (Figure 1-a) and an SS receiver (Figure 1-b) using a conventional standard PN code transmission system. In FIG. 1, l is a signal adder.

2 rJ: PN code generator, 3.4ri balanced modulator, 5゜6 is a carrier wave generator, the frequencies are respectively f, ,
f. 7 is a directional coupler, 8 is a transmitting antenna, 9
is a receiving antenna, 10.11 is a bandpass filter, and their center frequencies are f, , f, respectively.

12 is a balanced modulator, and 13 is a two-phase phase demodulator.

The adder 1 performs an exclusive OR operation on the transmission data signal 8 (t) and the PN code, thereby subjecting the carrier wave of frequency f to two-phase phase modulation. On the other hand, the carrier wave of frequency f is subjected to binary phase modulation using only the PN code.The two modulated waves are combined by the directional coupler 7 and sent out from the transmitting antenna 8. In the receiver, from the received 1g signal, the center frequencies f, &- and f are determined by the bandpass filter 10.11.
, and input it to the balanced modulator 12, each modulated wave is modulated by the same PN code at
``The PN code is canceled and the frequency f is output, and the frequency of the difference between the input modulated waves of f, (f!y=f1-f,)
An intermediate frequency signal equal to the transmitted data S (0, and thus a modified signal is output. When this is demodulated by the normal θ22-phase demodulator 13, the received data S' (t)
is obtained.

As described above, the standard PN code transmission method does not require the receiver to reproduce the PN code, so the configuration is very simple. However, in the conventional standard PN code transmission system, even if a large number of 18 transmitters are used and the PN codes of each transmitter are different, all can be received by one receiver. In other words, in an SS transceiver using the standard PN code transmission system, as long as the transmission frequency a is fixed to two components, f, and f, the meaning of using the code is to simply widen the spectrum in the radio wave propagation space. Although it has the feature of being resistant to interference by single spectrum waves, it has a serious drawback in that code multiplexing, which is another feature of SS, cannot be performed.

An object of the present invention is to provide 18 88 transceivers using a standard PN code transmission system capable of code multiplexing.

In order to perform code multiplexing in the standard PN code transmission method,
It is sufficient to use different PN codes for modulating the two carrier waves. However, if completely different codes are used, it becomes necessary to match the codes before correlation is taken on the receiver side, which becomes complicated. Therefore, the sharp autocorrelation of the PN code is used. In other words, a PN code shows a correlation with the same code that matches exactly down to the bit position, but shows only a small correlation with a code that is shifted by even one bit. Therefore, if one of the PNs that modulates the two carrier waves is bit-shifted relative to the other in the transmitter, the correlation will not be obtained unless the receiver corrects the bit shift amount of the PN code.
Unable to demodulate S. By using this, it is possible to multiplex the PN code with the cipher code.

The present invention will be explained below by way of examples. FIG. 2 and FIG. 3 are books showing the configuration of an embodiment of a transmitter and receiver board of a swiveled spectrum transmitter/receiver according to the present invention, respectively. In FIG. 2, 1 to 8 are the same components as in FIG. 1-a, and 21 and 22 are delay elements. Further, in FIG. 3, 9 to 13 indicate the same components as in FIG. 1-b, 23 and 24 are delay elements, 25 and 26 are frequency mixers, and 27 is a local oscillator.

In the transmitter shown in FIG. 2, a PN code that modulates a carrier wave with a frequency f is transmitted by delay elements 21 and 22 (n pips).
After being delayed (n is any natural number), it is applied to the balanced modulator 4. On the other hand, it is modulated with a signal obtained by exclusive ORing the carrier FiPN code of frequency fl and the transmission data, and the two carrier waves are combined by the directional coupler 7 and sent out from the transmission antenna 8.

Next, in the receiver, as shown in FIG.
The SS modulated waves of , are extracted and input to frequency mixers 25 and 26. When a signal of frequency fM from the local oscillator 27 is manually input to the frequency mixer 25.26, the modulated waves of frequencies f and f are respectively expressed as fl Fl - fl r,...
The frequency is converted into an intermediate frequency signal of fl Fl-et al-f. Here, as shown in FIG. 1-b, even if the two intermediate frequency signals are directly input to the balanced modulator 12, no correlation is established and SS despreading is not performed. The reason for this is 2.
This is because the PN code included in the two intermediate frequency signals is bittenfted. Therefore, the frequency f! is modulated by the PN code in which no delay element is inserted in the transmitter.
? input the intermediate frequency signals of , to the delay elements 23 and 24,
If the same amount of delay as the delay elements 21 and 22 inserted in the transmitter is given, the PN codes included in the two intermediate frequency signals will be codes of the same phase. If these are manually input to the equilibrium variable 111612 and correlated, SS despreading is performed and SSa tuning becomes possible. The intermediate frequency is added to the S8 demodulated signal.
Since the signal with the frequency equal to the frequency of the difference between 'I + 'I Fl is modulated by the transmission data S (t), by demodulating it with the normal two-phase phase demodulator 13, the reception data 8 ' (t ) is obtained.

As mentioned above, P
If you add a delay to the N code and correct the delay at the receiver,
It can be seen that code multiplexing can be performed by changing the amount of delay. The delay of the PN code at the transmitter is at the frequency '1 m
It may be applied to either of the PN codes that modulate the carrier wave of 'l.If the receiver side delays the undelayed one by the same amount, the effect will be the same.

In addition, in this embodiment, a configuration in which a frequency converter is used in the receiver has been explained, but if the delay elements 23 and 24 can be used in the RF band (for example, a surface acoustic wave delay element), frequency conversion can be performed. It can be configured without any need.

Furthermore, when applying the present invention to a large number of transceivers,
The number of delay elements applied to each transmitter may be changed for each transmitter.

Furthermore, if one receiver can change the number of delay elements, or if two waves taken from points with different numbers of delay elements are input to different correlators, code-multiplexed SS transmission can be achieved. It is possible to separate and receive waves in a time-division manner or simultaneously.

As described above, according to the present invention, code multiplexing can be performed simply by using a delay element in an SS transceiver using a standard PN code transmission system. Furthermore, with this method, code-multiplexed SS transmission waves can be separated and received by simply changing the number of delay elements in the receiver. Furthermore, since a delay element is only added as a component to a conventional transceiver, the advantage of the SS transceiver using the standard PN code transmission method, which is the simplicity of the structure, is not lost.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of a conventional standard PN code transmission system, with FIG. 1-a showing an SS transmitter and FIG. 1-b showing an SS receiver. FIG. 2 is a diagram showing an embodiment of the SS transmitter according to the present invention,
FIG. 3 is a diagram showing an embodiment of the SS receiver according to the present invention. 1... Signal adder, 2... PN code generator, 3, 4
゜12...Balanced modulator, 5.6...Carrier wave generator,
7... Directional coupler, 8... Transmission antenna, 9...
・Receiving antenna, 10.11...Band pass filter,
13...Two-phase phase demodulator, 21-24...Delay element, 25° 1st (l-α) (Noli VJ z Figure 3)

Claims (1)

[Claims] 1. Using two or more carrier waves in a transmitter, at least one s1# transmission wave is frequency spread modulated by a signal obtained by adding a pseudo noise code and a transmission data signal, and the first carrier wave is A second carrier wave having a different frequency from the 6sl and receiving a second carrier wave;
After being separated by a bandpass filter, the first and second modulated carriers are de-amplified by a correlator to eliminate the pseudo-noise code, and a frequency equal to the frequency difference between the first & second carriers. The intermediate frequency variation tJ41'F with
In a spread spectrum transmitter/receiver that transmits a reference pseudo-noise code and is configured to extract the I signal and demodulate the intermediate frequency modulated signal to obtain the transmission data signal, the transmitter modulates the first carrier wave. A signal obtained by adding a pseudo-noise code and a transmission data signal, or the pseudo-noise code that modulates the second carrier wave is delayed by at least one pinto code of the pseudo-noise code, and then spread-modulated and received. Of the two carrier waves received by the transmitter, the carrier modulated by the signal that has not been delayed by the transmitter is delayed by the same amount of delay as was delayed by the transmitter, and then the two carrier waves are correlated. A spread spectrum transmitter/receiver featuring: