JPH02100546A - Spectrum diffusion communication system - Google Patents

Abstract

PURPOSE:To suppress the frequency deviation or phase deviation between a transmission frequency and a reception frequency by changing a carrier in a continuous period including continuous or partial polygonal point and adjusting the generation periods of the function generator of a transmission part and that of a reception part to be almost similar. CONSTITUTION:Since the change period deviation or phase deviation of the transmission frequency and the reception frequency can be synchronized by performing feed back by an output voltage which has inverted an FM demodulation output at the up and down time of a triangle wave if an information output is set to be FM modulation since respective generation periods of the function generator 39 of the reception part and the function generator 33 of the transmission part are initially adjusted to be similar. In other words, both frequency changes of transmission and reception in a detection signal from an FM demodulation part 43 are synchronized by slightly moving the frequency of a triangle wave generator 39 by an inversion signal generated in the voltage control type triangle wave generator 39.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a spread spectrum communication system.

[Prior art] As a conventional spread spectrum communication system, for example,
A direct diffusion method (DS method) as shown in Figs.
Alternatively, there is a frequency popping method (FH method) as shown in FIGS. 12 to 14.

First, to explain the DS system, the transmitting section has an information modulating section 1, a spreading modulating section 2, a PN generator 3, and a power amplifying section 4 as shown in FIG. As shown in FIG.
It has a synchronous circuit 8 and a PN generator 9.

The transmitter performs phase modulation of a signal wave normally modulated such as AM or FM modulation using a pseudo-noise sequence (PN sequence) or a GOLD code, thereby generating a signal band larger than that of normal modulation and transmitting the signal wave.

Here, the information signal is shown in (A) of FIG. 11, and the FM signal is shown in (8) of FIG.
Modulated wave (information modulated wave), PN sequence in (C), (D>
show the direct diffusion waves, respectively.

On the other hand, the receiving section receives the signal by demodulating the received wave after returning it to the original normal modulated wave using the same code sequence as the transmitting section.

Next, to explain the F 1-1 method, the transmitter
As shown in the figure, an information modulation section 10, a frequency conversion section 11,
The receiving section includes a power amplification section 12, an oscillator 13, a selection circuit 14, and a selection code generator 15, and as shown in FIG. circuit 19, selection code generator 20. It has a selection circuit 21 and an oscillator 22.

The transmitter generates and transmits a large signal band by changing the carrier wave of the normal modulated wave by switching each output of the oscillator 13 using a PN sequence or a read mode Solomon code.

Here, in FIG. 14, (A>) shows an information signal, (B) shows an information modulated wave, (C) shows a PN code, and (D> shows a sending waveform.

The receiving section receives the demodulated signal by switching the reception center frequency using the same code sequence as the transmitting section.

In these DS and FH methods, if the communication band during normal modulation is B and the communication band after spreading is W, it is expected that the S/N ratio will be improved by Gp = W/B compared to normal communication. .

[Problem to be solved by the invention] However, in the case of the DS method among such conventional spread spectrum communication methods, the transition speed of the PN sequence (
Since the spread band is determined by the chip speed (chip speed), a high-speed logic circuit is required, making it difficult to synchronize the reception.Furthermore, when a signal stronger than the target signal is input, the wideband amplification section There was a problem in that synchronization and demodulation became impossible due to saturation.

On the other hand, in the case of the Fl-1 method, there are problems similar to those of the DS method, and in addition, the switching time during frequency switching cannot be ignored, and switching shock occurs, so information demodulation in the receiving section is difficult. The problem with this system was that unnecessary noise was introduced at each frequency switching timing.

The present invention was made in view of these conventional problems, and allows reception synchronization to be easily performed without requiring a high-speed logic circuit, and also prevents the saturation of the amplifier in the reception section. It is an object of the present invention to provide a spread spectrum communication system that prevents unnecessary noise from being mixed in.

[Means for Solving the Problems] In order to achieve the above object, the present invention changes the carrier wave continuously or in a continuous period including some breakpoints, thereby creating a spectrum that is sufficiently wider than the frequency band of the transmitted information. After spreading the communication band and radiating it into the air, the radiated radio waves are received by an antenna, and then amplified by a narrowband amplifier that changes the center tuning frequency in a similar continuous cycle or a continuous cycle that includes some breakpoints. An intermediate frequency signal is obtained by converting the frequency in a similar continuous period or in a continuous period including a partial break point.

[Operation] In the present invention, in order to adjust the generation cycles of the function generator of the transmitting section and the function generator of the receiving section so that they are almost the same, occurrence of a frequency shift or a phase shift between the transmitting frequency and the receiving frequency is avoided. synchronization can be easily performed without the need for high-speed logic circuits.

In addition, because a tuned narrowband amplifier is used instead of the wideband amplifier in the conventional receiver, saturation does not occur even if a signal stronger than the target signal is input, making synchronization and demodulation impossible. There is no.

Furthermore, the 11 transmission waves of the information modulated wave are not switched using discrete codes, but the carrier wave is changed continuously or in a continuous cycle that includes some breakpoints, which prevents unnecessary noise from being mixed in when switching frequencies. can do.

[Example" Embodiments of the present invention will be described below based on the drawings.

FIG. 1 and FIG. 2 are diagrams showing one embodiment of the present invention.

First, the transmitting section shown in FIG. 1 will be explained. In FIG. 1, 31 is an information modulating section, and the information modulating section 31 frequency-modulates information such as an audio signal, a measured value signal, or a serialized digital signal. It performs normal modulation such as phase modulation and AM modulation, and outputs the modulated signal to the frequency conversion section 32. 33 is a function generator, and the function generator 33 generates a continuous linear or non-linear periodic wave including a partial break point, such as a triangular wave, a sawtooth wave, or a sine wave, with a fixed period and imaging width. is generated and output to the V-F converter 34.

The V-F converter 34 converts the frequency of the signal generated by the function generator 33 and outputs it to the frequency converter 32 . The frequency conversion section 32 performs frequency conversion based on the input of the modulated output from the information modulation section 31 and the frequency conversion output from the V-F converter 34, and outputs the result to the power amplification section 35. The power amplification section 35 amplifies the power of the output from the frequency conversion section 32 and radiates electromagnetic waves via the antenna 36.

Here, if the modulation frequency of the information modulation section 31 is fl and the output of the V-F converter 34 is T2, then from the frequency conversion section 32, fl + f2, fl - T2, fl +2f
2, fl-2f2, and other signals are generated. in this case,
Since the output of the function generator 33 changes smoothly, an electronic tuning circuit (
A circuit in which the tuning frequency is changed by an external voltage using a coil and a barrier pull capacitance diode (see Figure 7)
By using , it is possible to select only the desired spread wave of fl + f2 or T2 - fl, and it is possible to suppress unnecessary spread waves.

Next, the receiving section will be explained based on FIG.

In FIG. 2, reference numeral 37 denotes a tuned narrowband amplifying section into which the transmitted signal from the transmitting section is input via the antenna 38. The tuned narrowband amplifying section 37 amplifies the received signal, but its tuning frequency is a function of It is determined by the generator 39, and its band is approximately equal to the information modulation band of the transmitter. Function generator 3
9 generates the same waveform as that of the function generator 33 of the transmitting section, but its period is made variable by the synchronization circuit 40.

The waveform generated by the function generator 39 is output to the tunable narrowband amplifier section 37 and the -F converter 41, respectively.

The V-F converter 41 generates a signal in the same range as that of the V-F converter 34 in the transmitter, or offset by the intermediate frequency after frequency conversion, and outputs it to the frequency converter 42 .

The frequency conversion section 42 converts the frequency by inputting the output of the V-F converter 41 and the output of the tuned narrowband amplification section 37 and outputs the frequency to the information demodulation section 43 . The information demodulation section 43 demodulates the output from the frequency conversion section 42 and outputs the demodulated signal.

Next, each output waveform of the transmitting section and the receiving section will be explained based on FIG.

In FIG. 3, (A) shows the case of a trigonometric function generated by the function generator 33 of the transmitter, and T1 is its period;
1 and 2 indicate voltage values, respectively.

(B) shows the output waveform of the V-1:converter 34 of the transmitting section, where when the trigonometric function is Vl, the frequency is fa, and when the trigonometric function is v2, the frequency is fb. (C) shows the modulated output of the information modulating section 31, and the frequency is fd.

Therefore, the transmission output obtained by converting the frequency of the output of the -F converter 34 and the output of the information modulation section 31 is shown by (D). In this case, when the trigonometric function is ■1, fa
d, when V2, it becomes fb+fd.

Note that this transmission output becomes the reception output of the reception section.

Next, (E) shows an example of a trigonometric function generated by three function generators in the receiving section, and its period is ±Δt by the synchronization circuit 40.
It is said to be variable. (F) shows the output waveform of the V-F converter 41 in the receiving section, and when the trigonometric function is vl, f
a +fd -fc, V2 sharpening fb +fd-f
c. (G) shows the input waveform of the information demodulating section 43 of the receiving section, and its frequency is the aforementioned fc.

Now, the output of the V-F converter 34 of the transmitter (see (B)) and the V-F converter 41 of the receiver
If the outputs (see (F)) are exactly the same, the modulation output fd on the transmitting side and the demodulation input fc on the receiving side will be the same, and the information modulated wave can be reproduced.

In addition, the V-F converter 34 of the transmitter and the V-F converter 34 of the receiver
Even if the frequency generated by the F converter 41 is always biased by fe, the receiving side receives fc + fe or fc-fe.
The demodulation signal is input only, and after demodulation, the same information as the transmitted information can be reproduced.

Incidentally, a phase shift or a frequency shift between the frequency displacements of the V-F converter 34 of the transmitting section and the V-F converter 41 of the receiving section may occur. For example, as shown in FIG. 4, the period of the transmission frequency may be smaller than the period of the reception frequency, or as shown in FIG. 5, the period of the transmission frequency may be larger than the number of reception periods.

Such a change cycle shift or phase shift between the transmitting frequency and the receiving frequency is caused by the fact that the respective generation cycles of the function generator 39 of the receiving section and the function generator 33 of the transmitting section are initially adjusted to be almost the same. When the output is FM modulated, the FM demodulated output can be synchronized by being fed back using an inverted output voltage at the rising and falling times of the triangular wave. A synchronization circuit for this synchronization is shown in FIG. In FIG. 6, for example, if the frequency change rate is set to a higher frequency than the frequency band of the original information, the output of the high-pass filter (HPF) 44 will be output from the FM demodulator 43 regardless of the transmitted information. The FM demodulation output of is detected.

A triangular wave generator 3 that passes this detection signal through a low-pass filter (LPF) 45 after inversion or forward rotation using an inverted signal generated by a voltage-controlled triangular wave generator 39.
By nudging the frequency of 9, both transmit and receive frequency changes can be synchronized.

As shown in FIG. 7, the V-F converter 34, 41 uses a phase-locked loop oscillator consisting of a coil 46 and a barrier-pull capacitance diode 47. A converter can be realized, and a circuit as shown in FIG. 7 can also be used as an electronic tuning circuit of the narrow band amplification section 37 of the receiving section.

Further, in this embodiment, the case of spectrum spreading using a triangular wave has been explained, but the spectrum is not limited to this, and it is also possible to spread the spectrum using, for example, a sine wave or a sawtooth wave, and these waveforms are continuous most of the time. Therefore, the tuning frequency of the narrowband amplifying section 37 of the receiving section changes smoothly,
Furthermore, since the signal input to the information demodulator 43 also changes smoothly, there are few sudden changes in the signal, and communication with a high S/N ratio is possible.

In addition to the configuration of the transmitting section shown in FIG. 1, as shown in FIG. 8, the output of the function generator 33 and the information signal are added,
The output frequency of the V-F converter 34 may be changed depending on the added output. In this case, the configuration of the transmitter can be simplified.

"Effects of the Invention" As explained above, since the generation cycles of the function generators in the transmitting section and the receiving section are initially adjusted to be almost the same, there is no need for high-speed logic circuits, and it is easy to use. Synchronization can be performed.

Furthermore, since a tunable narrowband amplification section is used in the receiving section, saturation does not occur, and synchronization and demodulation will not become impossible. Furthermore, since the carrier wave is changed continuously or in a continuous cycle including some breakpoints, it is possible to suppress the generation of unnecessary noise during frequency switching.

[Brief explanation of drawings]

FIG. 1 is a diagram of a transmitting section showing an embodiment of the present invention. FIG. 2 is a configuration diagram of a receiving section, FIG. 6 is a diagram showing a synchronization circuit, FIG. 7 is a diagram showing a tuning circuit, FIG. 8 is another configuration diagram of the transmitting section, and FIG. 9 is a diagram showing the conventional configuration. Figure 1 shows the configuration of the receiver, Figure 1 shows the output waveform of the transmitter, Figure 2 shows the configuration of other conventional transmitters, 3 The figure is a configuration diagram of the receiving section, and Figure 4 is an output waveform diagram of the transmitting section.In the figure, 31: Information modulation section, 32.42: Frequency conversion section, 33.39: Function generator, 34, 41: V -F=+Nharter 35=Power amplification section, 36.38: Antenna, 37: Tunable narrowband amplification section, 40: Synchronous circuit, 43: Information demodulation section, 44: I (PF, 45 2 LPF, 46 2 coils) , 47: Barrier pull capacitance diode.

Claims (1)

[Claims] By changing the carrier wave continuously or in a continuous cycle that includes some breaking points, the communication band is spread over a spectrum sufficiently wider than the frequency band of the transmitted information and radiated into the air.After receiving the radiated radio waves with an antenna, Converting the frequency by amplifying with a narrowband amplifier that changes the center tuning frequency in a similar continuous period or in a continuous period including a partial break point A spread spectrum communication system characterized by obtaining an intermediate frequency signal using