JPH03220830A - Spread frequency communication equipment - Google Patents

Abstract

PURPOSE:To widen a spread band without increasing a clock speed of a pseudo noise signal by applying frequency spread using a local oscillation signal of a multi-line spectrum of equal intensity and equal interval to a transmitter side and a receiver side in addition to conventional direct spread. CONSTITUTION:A transmitter 1 of a frequency spread communication equipment using the direct spread system applies product calculation between a digital information signal (a) to be sent and a PN code (b) being a pseudo noise signal from a PN code generator 5 and outputs a spread signal (c). Moreover, a mixer circuit 6 applies product calculation between the spread signal (c) and a local oscillation signal (d) of a multi- line spectrum of equal intensity and equal interval from a multi-frequency oscillator 7 and outputs a broad band transmission signal (e) subject to spread modulation to a transmission line 3. The receiver 2 is provided with a multi-frequency oscillator 8 having a same characteristic as the multi-frequency oscillator 7 and generating a local oscillation signal (f) of a multi-line spectrum, a mixer circuit 9, a mixer circuit 12 and a PN code generator 11 having the same characteristic as the PN code generator 5 and generating a PN code (i) and applies inverse spread processing with the product calculation among the reception signal, the local oscillation signal 5 and the PN code (i).

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a direct sequence frequency spread communication device used in fields such as wireless communication and wired multiplex communication.

2. Description of the Related Art In recent years, the spread spectrum communication system (SS system), which has characteristics such as being resistant to noise and having excellent confidentiality and can be accessed multiple times using code division multiplexing, has attracted attention, and various documents, publications, etc. have been published regarding its principles, practical application, etc. It is introduced by.

Here, as the SS method, the direct sequence method and the frequency hopping method are mainly studied. The direct diffusion method is shown in, for example, Japanese Patent Application Laid-Open No. 63-267033,
The signal is directly modulated and spread by a pseudo-noise signal. For example, the frequency hopping method is described in Japanese Patent Application Laid-open No. 64-48.
This method is disclosed in Japanese Patent No. 545, and performs frequency spreading by switching the carrier frequency of a signal at short time intervals.

Problems to be Solved by the Invention In the SS system, the processing gain after despreading is determined by how wide a frequency band the information signal is spread. Therefore, in order to increase the gain, it is necessary to increase the spreading factor, but in the direct spreading method, the spreading bandwidth is determined by the clock speed of the spreading code (pseudo-noise signal), so the code generator (pseudo-noise signal generator) The operating speed of the device limits the upper limit of the diffusion rate. Furthermore, as the clock speed increases, the range of the synchronization signal becomes narrower, making synchronization difficult and causing problems due to delay time.

Incidentally, in the frequency hopping method, a large number of carriers are used to widen the band, but multiple carriers are not used at the same time, but one carrier at a time is used.

Means for solving the problem In a frequency spread communication device using the direct spread method, the pseudo noise signal generator and the mixer circuit have equal strength.

A transmitter equipped with a local signal oscillator and a mixer circuit that generates a local signal with an equally spaced multiline spectrum performs spread modulation by multiplying the information signal, pseudo-noise signal, and local signal, and the transmitter side and A receiver equipped with a mixer circuit as well as a pseudo-noise signal generator and a local oscillator signal with the same characteristics was configured to perform despreading by multiplying the received signal, the local oscillator signal, and the pseudo-noise signal.

A local signal oscillator that emits a local signal with a multi-line spectrum of equal strength and equal spacing is installed on the transmitter and receiver sides, and a local signal with a multi-line spectrum is used in addition to normal direct diffusion. Since the frequency is spread, the spread band can be widened without increasing the clock speed of the pseudo-noise signal.

Therefore, in the case of the same power density, the total transmission power can be significantly increased, and in particular, in the case of wireless communication, the transmission distance can be extended.

Example An embodiment of the present invention will be described based on the drawings.

The communication device of this embodiment has a transmitter 1 and a receiver 2 coupled through a transmission path 3, but the main difference from that of a normal direct-sequence method is that a multi-line spectrum of equal intensity and equal intervals is used. An oscillator for generating a local oscillation signal is provided in each of the transmitter 1 and the receiver 2, so that the local oscillator signal with a multiline spectrum can be used together.

First, the transmitter 1 is provided with a first mixer circuit 4 whose one input is the digital information signal a to be transmitted. Also, P
An N code generator (pseudo-noise signal generator) 5 is provided and connected to the other input of the first mixer circuit 4. Therefore, the first mixer circuit 4 multiplies the information signal a and the PN code and outputs the result as a spread signal C (see FIG. 2(a)). A second mixer circuit 6 is provided which receives this spread signal C as one input. Furthermore, the second
As shown in Figure (b), a multi-frequency oscillator 7 is provided as a local oscillator oscillator that emits a local oscillator signal d having a multiline spectrum of equal intensity and equal intervals, and is connected to the other input of the second mixer circuit 6. It is connected.

Therefore, the second mixer circuit 6 performs a product operation of the spread signal C and the local signal d, and outputs it to the transmission line 3 as a spread-modulated wideband transmission signal e (see FIG. 2(c)). .

In this example, a five-frequency local oscillator is used as the multi-frequency oscillator 7, but generally an n-frequency oscillator may be used. As a result, if the power density is the same, it is possible to transmit n times more power than that of a single frequency. In addition, in this example, the spectral interval of the local signal d generated by the multi-frequency oscillator 7 is matched to the width of the main lobe of the spread signal C, but since there is no particular restriction on this spectral interval, the interval may be made narrower. The spectrum may be flattened by overlapping the spread signals C.

Conversely, mutual interference may be reduced by widening the spectral interval to form discrete spectra and allowing existing broadcast waves or the like to come between each spectrum.

Such a transmission signal e is sent to the receiver 2 through a transmission line 3 using radio waves, coaxial cables, spatial light, optical fibers, etc.

On the receiver 2 side, there is a local oscillator oscillator that emits a local oscillator signal f with a multiline spectrum as shown in FIG. A multi-frequency oscillator 8 is provided as a multi-frequency oscillator. Also,
A first mixer circuit 9 is provided which inputs the transmission signal (=reception signal) e and the local oscillation signal f, and the first mixer circuit 9 receives the transmission signal e and the local oscillation signal r.
A product operation is performed. As a result, a spectral difference frequency signal g as shown in FIG. 2(e) is obtained. In this example, the signal reaches its maximum at a frequency that matches the spectral interval of the multi-frequency oscillator 8, and is 2(
n-1) It is possible to receive a signal that is twice as strong. The difference frequency signal g is passed through the first filter 10 (the broken line F1 in FIG. (See figure (f)). Note that, instead of extracting the strongest lobe, lobes in the baseband or high frequency band may be extracted and used for demodulation.

Furthermore, the receiver 2 is also provided with a PN code generator 11 that generates a PN code (=pseudo noise signal) i having a spectrum as shown in FIG. 2(f). here,
The center frequency of the PNN code is made to match the spectral interval of the multifrequency oscillator 8.

Further, a second mixer circuit 12 is provided which receives the filter-passed signal and the PNN code as inputs, and performs a product operation on the filter-passed signal and the PNN code.

In other words, despreading is performed by multiplying the filtered signal while synchronizing it with the PN code.
The resulting spectrum becomes a despread signal j as shown in FIG. 2(g). Here, the despread signal j is the difference frequency component J
(−) as well as the sum frequency component j(+), the despread signal j is passed through the second filter 13 (broken line F2 in FIG. 2(g)).
(showing this filter characteristic), only the difference frequency component j(-) is extracted as a demodulated signal (Figure 2 (h)
)reference).

In this way, according to the SS communication device of this embodiment, since the frequency is spread by using the direct sequence method in combination with the local oscillator signal of the multiline spectrum, a wide spread band can be obtained without increasing the clock speed of the PN code. It becomes possible to For this reason, there is no need to use expensive devices such as extremely high-speed PN code generators and mixers that are required in the conventional method, so the configuration can be made at low cost, and each device does not need to be used at such high speed. Therefore, there is no need to particularly consider device delay time, etc.

It should be noted that the present invention basically only needs to perform product calculation processing of each signal on the transmitter 1 and receiver 2 sides, respectively, and the product calculation processing is limited to the order according to the configuration shown in FIG. figure,
The order may be changed as appropriate. For example, the receiver 2 may first perform a product operation on the local oscillator signal f and the PNN code, and then perform a product operation on the transmitted signal e. In this case, the first filter 10
It doesn't have to be there.

Also, the spectrum on the PNN code on the receiver 2 side is
It may be made to match the spectrum of the PN code on the side. In this case, the first filter 10 needs to have a filter characteristic that allows only the lobe one level lower than the filter characteristic F1 shown in FIG. 2(e) to pass through.

By the way, a local signal oscillator corresponding to the multi-frequency oscillators 7 and 8 can be constructed as shown in FIG. 3 or FIG. 4. The local oscillator 14 shown in FIG. 3 is constructed using a crystal oscillator 15, which is widely used in various digital circuits, as an oscillation source. In this case, since the oscillation output (digital clock) of the crystal oscillator 15 contains many harmonic components, its spectrum is flattened by passing it through the compensation filter 16, so that it becomes a multi-frequency output with equal frequency intervals. I have to. Compensation filter 1
6, a high-pass filter is basically used. Further, in the case of wireless communication, after passing through the compensation filter 16, it is necessary to perform a product calculation in the mixer circuit 18 using another frequency signal from the single frequency oscillator 17 to perform frequency conversion. However, in the case of wired communication, this is not particularly necessary.

Furthermore, the present invention is not limited to the crystal oscillator 15, and can be similarly applied to oscillators containing many harmonic components. In any case, by using a crystal oscillator 15 that has an oscillation output that originally contains many harmonic components, the desired local signal oscillator can be obtained by simply passing it through a filter, making it easy to manufacture and inexpensive. Become something.

The local oscillator 19 shown in FIG. 4 uses an ordinary single frequency oscillator 20 as an oscillation source.
The oscillation output of the mixer circuit 21 is input to one side of the mixer circuit 21, and the output of the mixer circuit 21 (amplified by the amplifier 22) is fed back to the other input of the mixer circuit 21, thereby generating harmonics. It is. As a result, it becomes a multi-frequency oscillator similar to the crystal oscillator 15 in FIG.
6. Single frequency oscillator 17 and mixer circuit 1 if necessary
8 may be added. According to this example, the mixer circuit 21 is added to the single frequency oscillator 20 as a normal local oscillator.
, an amplifier 22 and a compensation filter 16, the mixer circuit 21 can be configured by simply adding an amplifier 22 and a compensation filter 16.
It can be easily and easily manufactured by forming it with .

Effects of the Invention As described above, the present invention provides a local signal oscillator that generates a local signal with a multi-line spectrum of equal intensity and equal intervals on each of the transmitter side and the receiver side, in addition to ordinary direct spreading. Since frequency spreading is performed using a local signal with a multiline spectrum, the spreading band can be expanded without increasing the clock speed of the pseudo-noise signal. Transmission power can be significantly increased, making it possible to extend transmission distances, especially in the case of wireless communications, without the need for expensive devices such as extremely high-speed pseudo-noise signal generators. Therefore, it can be constructed at low cost without particularly considering the delay time of the device.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a block diagram, FIG. 2 is a frequency characteristic diagram showing signal waveforms of each part, and FIGS. 3 and 4 are configuration examples of a local signal generator. FIG. DESCRIPTION OF SYMBOLS 1... Transmitter, 2... Receiver, 4... Mixer circuit, 5... Pseudo noise signal generator, 6... Mixer circuit,
7, 8...Local signal oscillator, 9...Mixer circuit, 1
1... Pseudo noise signal generator, 12... Mixer circuit,
14.19...Local signal oscillator

Claims (1)

[Claims] A frequency spread communication device using a direct-sequence method includes a pseudo-noise signal generator, a mixer circuit, and a local oscillator signal oscillator and mixer circuit that emit a local oscillator signal with a multi-line spectrum of equal strength and equal intervals, and which generates an information signal and a mixer circuit. A transmitter that performs spread modulation by multiplying a pseudo-noise signal and a local oscillator signal is provided, and a mixer circuit is provided along with a pseudo-noise signal generator and a local oscillator with the same characteristics as the transmitter side to combine the received signal and the local oscillator signal. 1. A frequency spread communication device comprising a receiver that performs despreading by multiplying a signal and a pseudo noise signal.