JP2006211635A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system in which a transmission/reception distance is more extended by actualizing high-sensitivity reception when information communication is performed between a mobile station and a fixed station or between mobile stations. <P>SOLUTION: Two waves of different frequencies are transmitted from a radio station 1. When the two waves are received in a radio station 2, each of the two waves is subjected to frequency shift by a frequency shift means 202, and one or both waves are modulated and looped back. In the radio station 1, a new wave resulting from canceling frequency components added in frequency shift is generated using the looped-back two waves and the two waves transmitted to the radio station 2, and a component of a frequency difference or a frequency sum of the waves looped back at such a time is extracted and demodulated using an extremely narrow band filter 108. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless communication system for low-speed digital signals and narrowband analog voice signals between a mobile station and a fixed station or between mobile stations in the field of mobile communication.

  In the field of mobile communications, low-speed digital signals and narrow-band analog voice signals should be used for transmission of important information even though there is a very small amount of information such as confirmation of survival and judgment information of YES-NO. Is possible.

  Non-Patent Document 1 below describes a configuration example of a general wireless receiver, and the performance of the wireless receiver is determined by the amplification factor of the receiver and the internal noise indicating how much radio waves can be received. Sensitivity, selectivity indicating the ability to select only radio waves of the desired frequency from radio waves of various frequencies that enter the receiving antenna, and the ability to faithfully reproduce the signal sent from the transmitting side It describes the fidelity and stability indicating the ability to obtain a constant output over a long period of time without touching the receiver when a signal of constant amplitude and frequency is applied to the receiver.

  Regarding the performance of the above wireless receiver, Non-Patent Document 1 states that if the bandwidth of the intermediate frequency is narrowed in order to improve the selectivity, the stability of the receiver decreases. It is stated that it is not good to widen the bandwidth more than necessary, and that if the passband width of the intermediate frequency stage is excessively widened, the proximity frequency selectivity becomes insufficient and the noise increases.

As described above, how to properly detect and set the passband width and the center frequency of the signal received in wireless communication has been a conventional problem. Two waves with different frequencies are transmitted from the device to the transmitting device, the wave modulated using the waves of those frequencies is folded back from the transmitting device, and detection is performed using the waves transmitted to the transmitting device at the receiving device. The technology to do is not found in the past.
Akihiro Masaru “Radio Engineering A”, published by Tokyo Denki University Press, March 20, 1992, 1st edition, 1 print, p. 82-85

  Conventionally, in the field of mobile communication, for example, in the transmission of information such as low-speed digital signals and narrowband analog voice signals, the frequency band of the transmitted signal is narrow. However, if the band of the received filter is narrowed, the center frequency of the filter Since the center frequency of the received carrier is shifted, the transmitted signal goes out of the reception frequency band, and the received waveform is distorted due to the effect of phase rotation and attenuation characteristics caused by the filter, or an appropriate S / N. There is a problem in that it cannot be received at a ratio (ratio of signal to noise).

  SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of conventional communication systems and to provide a system that performs communication between a mobile station and a fixed station or between mobile stations with high sensitivity and extends the distance between transmission and reception. According to the present invention, high-sensitivity reception with a narrow reception band of about several Hz is realized, and communication at a sufficiently long distance is possible even when the transmission power is small.

  In order to solve the above-mentioned problem, the present invention transmits two waves having different frequencies and receives two waves at the opposite station, respectively, shifts the frequency and modulates one or both of them to return and return. The two waves that have been transmitted and the two waves transmitted to the other station are used to generate a new wave that is offset so that it is not affected by the frequency uncertainty component added at the time of the frequency shift at the other station. High-sensitivity reception is realized by extracting and demodulating the frequency difference or frequency sum component of the returned waves using a filter with a very narrow band.

FIG. 1 is a diagram for explaining the outline of the present invention. In the present invention, the first oscillating means 101 of the radio station 1, oscillates a first wave of frequency f _1, the second oscillating means 102 frequency f ₂ second of (f ₂ ≠ f ₁₎ Waves are oscillated, and each wave is transmitted from the transmission means 103 to the radio station 2.

The receiving means 201 of the radio station 2 receives the first wave and the second wave. The frequency shift means 202 shifts the frequency of each wave by a predetermined frequency shift wave. By the frequency shift processing by the frequency shift means 202, a third wave having the frequency f ₃ is generated from the first wave, and a _fourth wave having the frequency f ₄ (f ₄ ≠ f ₃ ) is generated from the second wave. Generated.

  Either the third wave, the fourth wave, or both are modulated based on transmission information from the radio station 2 to the radio station 1. FIG. 1 shows an example in which the third wave is modulated by the modulation means 203.

The transmission unit 204 transmits the third wave modulated by the modulation unit 203 and the fourth wave generated by the frequency shift unit 202 to the radio station 1. The frequency shift means 202 shifts the frequencies of the frequencies f ₁ and f _{2 because} the wave transmitted from the radio station 2 to the radio station 1 by the transmission means 203 is received by the reception means 201 of the radio station 2 and wireless. This is so as not to be confused with the waves from station 1.

  When the receiving means 104 of the radio station 1 receives the modulated third wave and the unmodulated fourth wave, the frequency shift means 105 uses the frequency shift means 202 from the third wave and the fourth wave. A fifth wave is generated by canceling the frequency component added by the above step, a sixth wave is generated from the first wave and the second wave, and the fifth wave and the sixth wave are output.

  Here, since the frequency of the sixth wave matches the frequency of the fifth wave, a synchronized clock signal is obtained from the clock signal generating means 107 based on the sixth wave, and this clock When the signal is used to operate the filter 108, the center frequency of the filter can be exactly matched to the center frequency of the fifth wave.

  The demodulation means 106 obtains information transmitted from the wireless station 2 by demodulating using the generated fifth wave and sixth wave. In the demodulating means 106, the sixth wave is used for synchronous detection, but it is possible to demodulate only with the fifth wave. However, when digital modulation is performed by the modulation means 203 of the radio station 2, the demodulation means 106 can receive signals with the highest signal quality by performing synchronous detection.

  According to the present invention, as the filter for extracting the fifth wave, the center frequency of the fifth wave can be completely matched with the center frequency of the filter. A filter can be used. Therefore, a signal with a sufficient S / N ratio can be obtained, and highly sensitive reception is possible.

  Furthermore, in the present invention, since the sixth wave corresponds to the unmodulated carrier of the fifth wave that is modulated, when digital modulation is used, synchronous detection can be easily performed. Even when compared by the detection method, reception with good signal quality is possible.

  As an application of the present invention, when an analog audio signal is sent, the audio signal recorded by the storage means (not shown in FIG. 1) is reproduced at a lower speed, the frequency band is narrowed, and the radio station 2 If the modulation means 203 transmits it as a narrowband analog audio signal, it can be demodulated by the demodulation means 106 of the radio station 1, recorded again in another storage means (not shown), and reproduced as a normal audio signal. , S / N transmission is possible, and as a transmittable wireless section, communication can be performed over a longer distance.

[First Embodiment]
The first embodiment of the present invention is a radio communication system between a first radio station and a second radio station, and the first radio station and the second radio station are respectively described below. Is provided.

The first radio station is:
First oscillating means for oscillating a first wave;
A second oscillating means for oscillating a second wave;
First transmission means for transmitting a first wave;
Second transmitting means for transmitting a second wave,
The first wave and the second wave are transmitted to the second radio station.

The second radio station is
First receiving means for receiving the transmitted first wave;
Second receiving means for receiving the transmitted second wave;
A third oscillation means for oscillating a frequency shift wave;
First frequency shift means for inputting a first wave and a frequency shift wave received by the first reception means, shifting the frequency of the first wave and outputting a third wave;
Second frequency shift means for inputting a second wave received by the second receiving means and a wave for frequency shift, shifting the frequency of the second wave, and outputting a fourth wave;
A third transmission means for transmitting a third wave;
A fourth transmission means for transmitting a fourth wave;
Modulation means for modulating either one or both of the third wave and the fourth wave,
The modulated wave of the third wave or the fourth wave and the other unmodulated wave or both modulated waves are transmitted to the first radio station.

Furthermore, the first radio station
Third receiving means for receiving a third wave transmitted from the second radio station;
Fourth receiving means for receiving a fourth wave transmitted from the second radio station;
Third frequency shift means for inputting the received third wave and fourth wave and outputting a fifth wave in which the frequency component added by the second frequency shift means of the second radio station is canceled; ,
Fourth frequency shift means for outputting a sixth wave having a frequency and phase of a difference (or sum) between the first wave and the second wave;
Clock signal generating means for generating a clock signal synchronized with the sixth wave;
A filter that operates on the clock signal, is included in the third frequency shift means, and extracts a fifth wave;
Demodulating means for demodulating the extracted fifth wave,
Received information from the second radio station is obtained from the demodulated result.

[Second Embodiment]
The second embodiment of the present invention is a wireless communication system between a first wireless station and a second wireless station, and the first wireless station and the second wireless station are respectively means described below. Is provided.

The first radio station is:
First oscillating means for oscillating a first wave;
Fourth oscillating means for oscillating a seventh wave having a frequency (or sum frequency) of the difference between the first wave and the second wave;
Fifth frequency shifting means for inputting the first wave and the seventh wave to obtain the second wave;
First transmission means for transmitting a first wave;
Second transmitting means for transmitting a second wave,
The first wave and the second wave are transmitted to the second radio station.

The second radio station is
First receiving means for receiving a transmitted first wave; second receiving means for receiving a transmitted second wave;
A third oscillation means for oscillating a frequency shift wave;
First frequency shift means for inputting a first wave and a frequency shift wave received by the first reception means, shifting the frequency of the first wave and outputting a third wave;
Second frequency shift means for inputting a second wave received by the second receiving means and a wave for frequency shift, shifting the frequency of the second wave, and outputting a fourth wave;
A third transmission means for transmitting a third wave;
A fourth transmission means for transmitting a fourth wave;
Modulation means for modulating either one or both of the third wave and the fourth wave,
The modulated wave of the third wave or the fourth wave and the other unmodulated wave or both modulated waves are transmitted to the first radio station.

Furthermore, the first radio station
Third receiving means for receiving a third wave transmitted from the second radio station;
Fourth receiving means for receiving a fourth wave transmitted from the second radio station;
Third frequency shift means for inputting the received third wave and fourth wave and outputting a fifth wave in which the frequency component added by the second frequency shift means of the second radio station is canceled; ,
Clock signal generating means for generating a clock signal synchronized with the seventh wave;
A filter that operates on the clock signal, is included in the third frequency shift means, and extracts a fifth wave;
Demodulating means for demodulating the extracted fifth wave,
Received information from the second radio station is obtained from the demodulated result.

[Third Embodiment]
The third embodiment of the present invention uses a digital modulation system as the modulation means in the first embodiment or the second embodiment, and the demodulation means uses the sixth wave, Synchronous detection is performed for the fifth wave.

  As a digital modulation method, for example, BPSK (Binary Phase Shift Keying: binary phase modulation), QPSK (Quadrature Phase Shift Keying: quaternary phase modulation), π / 4 shift QPSK, or the like is used. In the present invention, not only these modulation schemes but also various other modulation schemes can be used.

[Fourth Embodiment]
According to a fourth embodiment of the present invention, in the first embodiment or the second embodiment, the second radio station further includes a first storage unit that stores an analog audio signal, An analog audio signal is temporarily stored using the first storage means, taken out as a narrowband analog audio signal at a low speed, and then analog-modulated by the modulation means. The first radio station further A second storage means for storing an analog audio signal, and the second storage means is used to temporarily store the narrowband analog audio signal demodulated by the demodulating means, so that the original analog audio is stored. Convert to signal speed.

[Fifth Embodiment]
The fifth embodiment of the present invention is the same as the first to fourth embodiments described above.
A first common transmission unit that uses the first transmission unit and the second transmission unit of the first wireless station in common is provided, and the first common wave and the second wave are combined to form a first common Transmit by transmission means.

[Sixth Embodiment]
The sixth embodiment of the present invention is the same as the first to fifth embodiments described above.
First common receiving means for commonly using the first receiving means and the second receiving means of the second wireless station is provided, and the first wave and the second wave transmitted from the first wireless station are provided. Are received by the first common receiving means, and their outputs are used separately.

[Seventh Embodiment]
The seventh embodiment of the present invention is the same as the first to sixth embodiments described above.
A second common transmission unit that uses the third transmission unit and the fourth transmission unit of the second radio station in common is provided, and the third wave and the fourth wave are combined to form a second common Transmit by transmission means.

[Eighth Embodiment]
The eighth embodiment of the present invention is the same as the first to seventh embodiments,
A second common receiving means that uses the third receiving means and the fourth receiving means of the first wireless station in common is provided, and the third wave and the fourth wave transmitted from the second wireless station are provided. Are received by the second common receiving means, and their outputs are used separately.

[Ninth Embodiment]
The ninth embodiment of the present invention is the same as the first to eighth embodiments,
Instead of providing the first frequency shift means and the second frequency shift means in the second radio station, a common frequency shift means is provided so that the first wave transmitted from the first radio station and the second frequency shift means A signal in a state where the waves are combined is input to the common frequency shift means, and the frequency is shifted by the common frequency shift means, so that the third wave and the fourth wave respectively shifted in frequency of the first wave and the second wave. A signal containing the wave of.

  Hereinafter, embodiments of the present invention for performing wireless communication between the wireless station 1 and the wireless station 2 will be described with reference to the drawings. Here, in order to simplify the explanation, delay times of amplifiers, filters, etc. are ignored.

FIG. 2 is a diagram illustrating the first embodiment of the present invention, in which digital information is transmitted from the second radio station to the first radio station. The radio station 1 includes an oscillator 3 that oscillates a wave having a frequency f ₁ and an oscillator 4 that oscillates a wave having a frequency f ₂ . The output of the oscillator 3 is transmitted from the first transmitter including the amplifier 5 and the antenna 6, and the output of the oscillator 4 is transmitted from the second transmitter including the amplifier 7 and the antenna 8. The

Assuming that the wave transmitted from the antenna 6 is X ₁ (t) and the wave transmitted from the antenna 8 is X ₂ (t) and ω ₁ = 2πf ₁ and ω ₂ = 2πf ₂ , the transmitted waves are respectively , Is expressed as: In this description, the amplitude is not essential, so the description is omitted.

X ₁ (t) = cos (ω ₁ t + θ ₁ ) (1)
X ₂ (t) = cos (ω ₂ t + θ ₂ ) (2)
The radio station 2 receives the waves X ₁ (t) and X ₂ (t) with a propagation time τ delay.

A wave transmitted from the antenna 6 is received by a first receiver including an antenna 9, a receiving amplifier 10, and a bandpass filter 11.
Y ₁ (t) = X ₁ (t−τ)
= Cos {ω ₁ (t−τ) + θ ₁ } (3)
Is output.

On the other hand, the wave transmitted from the antenna 8 is received by the second receiver including the antenna 12, the receiving amplifier 13, and the band pass filter 14.
Y ₂ (t) = X ₂ (t−τ)
= Cos {ω ₂ (t−τ) + θ ₂ } (4)
Is output.

In the first embodiment of the present invention, a constant frequency shift wave (frequency Δf, phase Δθ) arbitrarily determined by the oscillator 15 is oscillated, and the received waves Y ₁ (t) and Y ₂ (t) are respectively received. Is shifted in frequency and phase by frequency shift means 16 and 19. Here, in order to simplify the description, a case where f ₁ > f ₂ >Δf> 0 will be described first.

The frequency shift means 16 comprises a mixer 17 and a high-pass filter 18, and shifts the frequency and phase of Y ₁ (t) in the adding direction (MIX-UP: the same applies hereinafter). That is, as an output of the frequency shift means 16,
Z ₁ (t) = cos {ω ₁ (t−τ) + θ ₁ + (Δωt + Δθ)} (5)
Get. Here, Δω = 2πΔf.

The frequency shift means 19 includes a mixer 20 and a high-pass filter 21 and shifts the frequency and phase of Y ₂ (t) in the adding direction. That is, as an output of the frequency shift means 19,
Z ₂ (t) = cos {ω ₂ (t−τ) + θ ₂ + (Δωt + Δθ)} (6)
Get.

The wave Z ₁ (t) shifted in frequency and phase is further modulated by digital information in the digital modulator 22, and then transmitted by a third transmitter comprising an amplifier 23 and an antenna 24, while Z ₂ (T) is directly transmitted by the fourth transmitter including the amplifier 25 and the antenna 26.

  The wave transmitted from the antenna 26 remains the same as Equation (6) in terms of frequency and phase. However, since the wave transmitted from the antenna 24 is digitally modulated, it is expressed by the following equation.

Z ₁ ′ (t) = cos {ω ₁ (t−τ) + θ ₁ + (Δωt + Δθ) + φ (t)}
... (7)
Here, φ (t) is a phase component changed by digital information due to digital modulation.

The radio station 1 receives the waves Z ₁ ′ (t) and Z ₂ (t) with a propagation time τ delay.

A wave transmitted from the antenna 24 is received by a third receiver including the antenna 27, the reception amplifier 28, and the band pass filter 29.
R ₁ (t) = Z ₁ ′ (t−τ)
= Cos {ω ₁ (t−2τ) + θ ₁ + Δω (t−τ) + Δθ + φ (t−τ)}
(8)
Is output.

On the other hand, the wave transmitted from the antenna 26 is received by the fourth receiver including the antenna 30, the receiving amplifier 31, and the band pass filter 32,
R ₂ (t) = Z ₂ (t−τ)
= Cos {ω ₂ (t−2τ) + θ ₂ + Δω (t−τ) + Δθ} (9)
Is output.

In the radio station 1, four waves X ₁ (t), X ₂ (t), R ₁ (t), and R ₂ (t) are input to the multi-frequency shift means 33, and the radio station is used by using the result. 2 demodulates the digital transmission information sent from 2.

  In the case of the first embodiment shown in FIG. 2, the multi-frequency shift means 33 includes two frequency shift means 34 and 35.

The frequency shift means 34 comprises a mixer 36 and a band pass filter 37, and shifts the frequency and phase of the received waves R ₁ (t) and R ₂ (t) in the subtracting direction (MIX-DOWN: the same applies hereinafter). . As a result, the output of the frequency shift means 34 is
R (t) = cos {(ω ₁ −ω ₂ ) (t−2τ) + (θ ₁ −θ ₂ ) + φ (t−τ)} (10)
It becomes.

The frequency shift means 35 comprises a mixer 38 and a low-pass filter 39, inputs _two waves X ₁ (t) and X ₂ (t) oscillated in the radio station 1, and subtracts the frequency and phase. Shift to the next direction to get the next wave.

X (t) = cos {(ω ₁ −ω ₂ ) t + (θ ₁ −θ ₂ )} (11)
Comparing equation (10) and equation (11), the center frequency is the same, and only the phase difference is different from the value of 2 (ω ₁ −ω ₂ ) τ + φ (t−τ). That is, it can be understood that Expression (10) is obtained by performing phase modulation of φ (t−τ) on the carrier represented by Expression (11).

In the first embodiment of the present invention, a clock signal synchronized with X (t) is generated by the clock signal generator 41, and the band pass filter 37 is operated using this clock signal. In this case, since the center frequencies of X (t) and R (t) are exactly the same, the clock signal is also completely synchronized with R (t) in terms of frequency. A filter whose center frequency completely matches “f ₁ −f ₂ ”, such as a filter, can be used. Therefore, in order to extract R (t) represented by the expression (10), it is possible to use a bandpass filter having a sufficiently small bandwidth as the frequency bandwidth. As a result, it is possible to receive information with a very high S / N ratio for sufficiently slow and low-speed information transmission.

  The digital demodulator 40 is a demodulator that performs synchronous detection on R (t) represented by Expression (10) with reference to X (t) represented by Expression (11). Since R (t) has the same center frequency as X (t), synchronous detection is possible. Because of the synchronous detection and high S / N, the digital demodulator 40 can demodulate and output the digital information sent from the radio station 2 with high quality even with the same reception power.

  In the first embodiment of the present invention shown in FIG. 2, the polarity of the frequency shift means 16, 19, 34, 35 that is shifted with respect to the frequency and phase is the frequency shift means 16, 19 in the direction of addition (MIX-UP). Although the means 34 and 35 are shifted in the subtracting direction (MIX-DOWN), a plurality of combinations other than the above are possible for the polarity shifted by each frequency shift means.

Table 1 shows an example of the relationship between the frequency of R (t) (that is, the frequency of X (t)) and the polarity of each frequency shift means in the case of f ₁ > f ₂ >Δf> 0. “Addition” means shifting in a direction in which the absolute value of the frequency increases (MIX-UP), and subtraction means shifting in a direction in which the absolute value of the frequency decreases (MIX-DOWN).

ｆ₁ ＞Δｆ＞ｆ₂ ＞０の場合について，Ｒ（ｔ）の周波数（すなわちＸ（ｔ）の周波数）とそれぞれの周波数シフト手段の極性の関係例を表２に示す。

Table 2 shows an example of the relationship between the frequency of R (t) (that is, the frequency of X (t)) and the polarity of each frequency shift means for the case of f ₁ >Δf> f ₂ > 0.

Δｆ＞ｆ₁ ＞ｆ₂ ＞０の場合について，Ｒ（ｔ）の周波数（すなわちＸ（ｔ）の周波数）とそれぞれの周波数シフト手段の極性の関係例を表３に示す。

Table 3 shows an example of the relationship between the frequency of R (t) (that is, the frequency of X (t)) and the polarity of each frequency shift means when Δf> f ₁ > f ₂ > 0.

FIG. 3 is a diagram showing a second embodiment of the present invention. The difference in Figure 2 and Figure 3, the occurrence mechanism of the wave X (t) comprising a wave as a reference for the measurement of the frequency f ₂ is different.

  In addition, a plurality of transmission means for each radio station use a common transmission means, and a plurality of reception means also have a simple configuration using a common reception means.

  Further, in the second embodiment, the transmitted information is an analog audio signal waveform stored in the storage unit 51 of the wireless station 2, and the received information is output after being stored in the storage unit 59 in the wireless station 1. The

In FIG. 3, a wave X (t) serving as a measurement reference is oscillated by an oscillator 42. X (t) input to the clock signal generator 41 at this time is the same as in the first embodiment of the present invention.
X (t) = cos {(ω ₁ −ω ₂ ) t + (θ ₁ −θ ₂ )} (12)
It is represented by

In the second embodiment of the present invention, the wave X (t) represented by the equation (12) and the wave of frequency f ₁ , that is,
X ₁ (t) = cos (ω ₁ t + θ ₁ ) (13)
Is input to the frequency shift means 43 including the mixer 44 and the low-pass filter 45, and the wave of frequency f ₂ X ₂ (t) = cos (ω ₂ t + θ ₂ ) (14)
Have gained.

  In the second embodiment of FIG. 3, the amplifier 5, the antenna 6, the amplifier 7, and the antenna 8 corresponding to the first transmitter and the second transmitter of FIG. , And a first common transmission means comprising an amplifier 47 and an antenna 48, and an antenna 9, a reception amplifier 10, a band-pass filter 11 and an antenna corresponding to the first receiver and the second receiver in FIG. 12, the receiving amplifier 13 and the band pass filter 14 are constituted by a first common receiving means comprising the antenna 49, the receiving amplifier 50, and the band pass filters 11 and 14 of FIG. In the first embodiment described above, a configuration using the common transmission means and the common reception means as used in the second embodiment can also be adopted.

The wave X ₁ (t) transmitted from the antenna 48 is delayed from the bandpass filter 11 by the propagation time τ and is output as a waveform Y ₁ (t) represented by the following equation.

Y ₁ (t) = X ₁ (t−τ)
= Cos {ω ₁ (t−τ) + θ ₁ } (15)
On the other hand, the wave X ₂ (t) transmitted from the same antenna 48 is delayed by time τ from the band pass filter 14 and output as Y ₂ (t) shown in the following equation.

Y ₂ (t) = X ₂ (t−τ)
= Cos {ω ₂ (t−τ) + θ ₂ } (16)
Similarly to the first embodiment, the oscillator 15 oscillates the frequency shift wave (frequency Δf, phase Δθ), and the received waves Y ₁ (t) and Y ₂ (t) are respectively transferred to the frequency shift means 16 and 19. To shift the frequency and phase. Again, for simplicity of explanation, the case of f ₁ > f ₂ >Δf> 0 will be described first.

Similarly to the first embodiment, the frequency shift means 16 shifts the frequency and phase of Y ₁ (t) in the adding direction (MIX-UP: hereinafter the same),
Z ₁ (t) = cos {ω ₁ (t−τ) + θ ₁ + (Δωt + Δθ)} (17)
Get. Here, Δω = 2πΔf.

Similarly to the first embodiment, the frequency shift means 19 shifts the frequency and phase of Y ₂ (t) in the adding direction,
Z ₂ (t) = cos {ω ₂ (t−τ) + θ ₂ + (Δωt + Δθ)} (18)
Get.

  The analog audio signal of the radio station 2 is stored in the storage means 51, converted into a slower narrowband analog audio signal, and then input to the analog modulator 52.

The wave Z ₁ (t) shifted in frequency and phase is expressed by the following equation because it is modulated by the narrowband analog audio signal output from the storage means 51 by the analog modulator 52.

Z ₁ ′ (t) = cos {ω ₁ (t−τ) + θ ₁ + (Δωt + Δθ) + ψ (t)}
... (19)
Here, ψ (t) is a phase component that is modulated and changed by the narrowband analog audio signal. Waveforms Z ₁ ′ (t) and Z ₂ (t) are input to adder 53 and transmitted to radio station 1.

  In the second embodiment shown in FIG. 3, the amplifier 23, the antenna 24, the amplifier 25, and the antenna 26 corresponding to the third transmitter and the fourth transmitter of FIG. 55, the second common transmission means, and the antenna 27, the reception amplifier 28, the band-pass filter 29 and the antenna 30, corresponding to the third receiver and the fourth receiver in FIG. The band pass filter 32 is constituted by a second common receiving means comprising an antenna 56, a receiving amplifier 57, and band pass filters 29 and 32.

In the first embodiment of the present invention, the frequency f ₁ respectively when f ₂ are very far, although an example using a dedicated amplifier for each frequency, in the second embodiment, another frequency f ₁ and f _{When 2} is close, the amplifier can be used in common and it is economical.

The radio station 1 receives the waves Z ₁ ′ (t) and Z ₂ (t) with a propagation time τ delay.

From the bandpass filter 29,
R ₁ (t) = Z ₁ ′ (t−τ)
= Cos {ω ₁ (t−2τ) + θ ₁ + Δω (t−τ) + Δθ + ψ (t−τ)}
... (20)
Is output.

On the other hand, from the band pass filter 32,
R ₂ (t) = Z ₂ (t−τ)
= Cos {ω ₂ (t−2τ) + θ ₂ + Δω (t−τ) + Δθ} (21)
Is output.

In the radio station 1, four waves X ₁ (t), X ₂ (t), R ₁ (t), and R ₂ (t) are input to the multi-frequency shift means 33, and the radio station is used by using the result. 2 demodulates the narrowband analog audio signal sent from 2.

The multi-frequency shift means 33 comprises two frequency shift means 34 and 43. The frequency shift means 34 comprises a mixer 36 and a band pass filter 37, and shifts the frequency and phase of the received waves R ₁ (t) and R ₂ (t) in the subtracting direction (MIX-DOWN: the same applies hereinafter). . As a result, the output of the frequency shift means 34 cancels out the components of the frequency Δf (= Δω / 2π) and the phase Δθ added during the frequency shift,
R (t) = cos {(ω ₁ −ω ₂ ) (t−2τ) + (θ ₁ −θ ₂ ) + ψ (t−τ)}
... (22)
It becomes.

  The R (t) represented by the equation (22) is demodulated using the analog demodulator 58 to obtain a narrowband analog audio signal. The narrowband analog audio signal is once stored in the storage means 59, and is read out at a normal speed to be output as a normal speed analog audio signal.

  FIG. 4 shows an implementation example of the band pass filter 37 used in FIGS. 2 to 3 of the present invention. This filter corresponds to the filter 108 in FIG. In addition, FIG. 5 shows an example of operation waveforms of each part in FIG.

In FIG. 4, a case where a sine wave component of period T is input as the filter input waveform IN (t) as shown in FIG. This period is used as the period of the center frequency of the signal to be extracted when used in the band pass filter 37 of FIG.
T = 1 / (f ₁ −f ₂ ) (23)
There is a relationship.

  In the example shown in FIG. 4, an N pass filter is used as the band pass filter. This filter includes a resistor 60 (resistance value R), capacitors 62 to 71 (capacity values are all C) that are switched by a clock signal CLK and performing charging and discharging operations, and connections to the respective capacitors. It comprises an electronic switch 61 for switching, and a low-pass filter 72 that suppresses components whose waveform changes rapidly.

In the present invention, the input waveform IN (t) has a center frequency “f ₁ −f ₂ ”, and the clock signal is generated in synchronization with the wave X (t) having the same frequency. That is, since the clock signal CLK is synchronized with the input waveform IN (t), an integral multiple of the period of the clock signal CLK can be exactly matched with the period T. 4 and 5, this integer value n is set to n = 10.

  Each capacitor can be charged / discharged only while it is connected to the resistor 60 by the electronic switch 61. This connection is switched every T / 10, and the time during which each capacitor is connected to the resistor is T / 10 during the period T.

  Focusing on one capacitor, charging / discharging is performed with a time constant CR for a period of T / 10 with an accurate period T. This means that the input waveform survives exactly the waveform of the period T, and the other waveforms are attenuated.

  In FIG. 5, the waveform S (t) between the resistor 60 and the electronic switch 61 shows a waveform that is charged / discharged for T / 10 every period T. Since each capacitor is switched with an electronic switch, it looks like a staircase. By passing the waveform S (t) through the low-pass filter 72, a smooth waveform R (t) is obtained.

  In the band pass filter 37 used in the present invention, since the frequency of the clock signal CLK is accurately expressed by the relationship of “1 / integer” of the center frequency of the input waveform IN (t), the time constant CR is very large. Even so, the signal waveform represented by the equation (22) can be extracted. This means that the band-pass filter 37 has a center frequency that is exactly the same as the input sine wave, so that the frequency band can be made very small and the S / N ratio can be made very high. .

  For example, assuming that there is a receiver whose reception frequency bandwidth is about 3 kHz and the distance from the transmitter can be received only up to about 10 m, assuming that the reception band of the band pass filter 37 is 30 Hz, the S / N is improved by 20 dB. Therefore, the receivable distance is expected to extend to several tens to hundreds of meters.

  The band-pass filter 37 is not limited to the N-pass filter, and if the center frequency of the clock signal matches the center frequency of the input waveform IN (t), a sufficiently narrow band can be obtained using another digital filter. Is possible.

  FIG. 6 shows a configuration example of the storage means 51 or 59 used in the present invention. When an analog waveform is input as an input signal, it is converted into a digital signal by the A / D converter 73 and further stored in the memory 74 at the speed of the input clock signal.

  The contents stored in the memory 74 are read out at the speed of the output clock signal, returned to the analog signal by the D / A converter 75, and further, the quantization noise is removed by the filter 76 and output.

  When a normal audio signal is converted to a narrowband analog audio signal as in the storage means 51, a slower output clock signal is used as compared with the input clock signal, and a narrowband as in the storage means 59 is used. When returning an analog audio signal to a normal analog audio signal, an output clock signal that is faster than an input clock signal is used.

In the second embodiment described above, as shown in FIG. 3, the two received waves Y ₁ (t) and Y ₂ (t) are separated by the band pass filters 11 and 14, and the frequency is shifted by the frequency shift means 16 and 19, respectively. There is a shift.

On the other hand, the received two waves Y ₁ (t) and Y ₂ (t) are not separated but shifted in frequency as they are synthesized, and then required by an appropriate filter. Even if a wave is extracted, the present invention can be similarly realized.

  In this case, if the two received waves are shifted in the same direction, the frequency shift means 16 and 19 can be simplified.

FIG. 7 is a diagram showing a third embodiment of the present invention. In FIG. 7, the configuration of the radio station 1 is the same as that of the second embodiment shown in FIG. In the wireless station 2, instead of using the band-pass filters 11 and 14 for passing the waves Y ₁ (t) and Y ₂ (t) received from the wireless station 1, the Y ₁ (t) and Y ₂ (t) A band pass filter 80 that passes two waves is used. A wave received from the radio station 1 is input to the band pass filter 80, and its output is input to the frequency shift means 81. The frequency shift means 81 shifts the frequencies in the same direction together in a state where the two waves Y ₁ (t) and Y ₂ (t) are synthesized. The signal is modulated by the analog modulator 52 and transmitted to the radio station 1 via the amplifier 54 and the antenna 55.

It is a figure explaining the outline | summary of this invention. It is a figure which shows Example 1 of this invention. It is a figure which shows Example 2 of this invention. It is a figure which shows the implementation example of a band pass filter. It is a figure which shows the example of an operation waveform of each part of FIG. It is a figure which shows the structural example of a memory | storage means. It is a figure which shows Example 3 of this invention.

Explanation of symbols

1, 2 Radio station 3, 4, 15, 42 Oscillator 5, 7, 23, 25, 47, 54 Amplifier 6, 8, 9, 12, 24, 26, 27, 30, 48, 49, 55, 56 Antenna 10 , 13, 28, 31, 50, 57 Receiving amplifier 11, 14, 29, 32, 37, 80 Band pass filter 16, 19, 34, 35, 43, 81, 105, 202 Frequency shift means 17, 20, 36, 38, 44, 82 Mixer 18, 21, 83 High-pass filter 22 Digital modulator 33 Multi-frequency shift means 39, 45, 72 Low-pass filter 40 Digital demodulator 41 Clock signal generator 52 Analog modulator 58 Analog demodulator 51, 59 Memory means 60 Resistance 61 Electronic switch 62, 63, 64, 65, 71 Capacitor 73 A / D converter 74 Memory 5 D / A converter 76,108 filter 101 first oscillating means 102 second oscillation means 103 and 204 transmitting means 104 and 201 receiving unit 106 demodulating means 107 clock signal generating means 203 modulating means

Claims (4)

A wireless communication system between a first wireless station and a second wireless station,
The first radio station is:
Comprising one or more transmission means for transmitting a first wave and a second wave having different frequencies as radio waves,
The second radio station is
One or more receiving means for receiving the first wave and the second wave;
An oscillating means for oscillating a frequency shift wave;
First frequency shift means for inputting a received first wave and the frequency shift wave and outputting a third wave obtained by shifting the frequency of the first wave;
Second frequency shift means for inputting the received second wave and the frequency shift wave and outputting a fourth wave obtained by shifting the frequency of the second wave;
Comprising one or more transmission means for transmitting the third wave and the fourth wave;
Furthermore, the first radio station is
One or more receiving means for receiving the third wave and the fourth wave;
Third frequency shift means for inputting the received third wave and the fourth wave and outputting a fifth wave having a difference or sum frequency of the third wave and the fourth wave When,
Signal output means for generating or oscillating a sixth wave having a frequency that is the difference or sum of the first wave and the second wave;
The third frequency shift means operates with a clock signal synchronized with the sixth wave, and extracts the fifth wave from a wave having a difference or sum frequency of the third wave and the fourth wave. With a filter to extract,
Furthermore, the second radio station includes modulation means for modulating either one or both of the third wave and the fourth wave based on transmission information,
Further, the first wireless station includes a demodulating means for demodulating the extracted fifth wave. A wireless communication system between a first wireless station and a second wireless station,
The first radio station is:
Comprising one or more transmission means for transmitting a first wave and a second wave having different frequencies as radio waves,
The second radio station is
One or more receiving means for receiving the first wave and the second wave;
An oscillating means for oscillating a frequency shift wave;
A first frequency for outputting a third wave and a fourth wave by shifting the frequency in a state where the received first wave and second wave are synthesized using the frequency shifting wave. Shifting means;
Comprising one or more transmission means for transmitting the third wave and the fourth wave;
Furthermore, the first radio station is
One or more receiving means for receiving the third wave and the fourth wave;
Second frequency shifting means for inputting the received third wave and the fourth wave and outputting a fifth wave having a frequency that is the difference or sum of the third wave and the fourth wave. When,
Signal output means for generating or oscillating a sixth wave having a frequency that is the difference or sum of the first wave and the second wave;
The second frequency shift means operates with a clock signal synchronized with the sixth wave, and extracts the fifth wave from a wave having a difference or sum frequency of the third wave and the fourth wave. With a filter to extract,
Furthermore, the second radio station includes modulation means for modulating either one or both of the third wave and the fourth wave based on transmission information,
Further, the first wireless station includes a demodulating means for demodulating the extracted fifth wave. In the wireless communication system according to claim 1 or 2,
The modulation means performs digital modulation,
The radio communication system, wherein the demodulation means uses the sixth wave to perform synchronous detection on the fifth wave. In the wireless communication system according to claim 1 or 2,
The transmission information is an analog audio signal,
The second wireless station further includes first storage means for storing an analog audio signal, and temporarily stores the analog audio signal using the first storage means, so that the original analog audio is stored. After taking out as a narrowband analog audio signal at a lower speed than the signal speed, analog modulation by the modulation means,
The first wireless station further includes second storage means for storing an analog voice signal, and temporarily stores the narrowband analog voice signal demodulated by the demodulation means using the second storage means. A wireless communication system characterized by converting the speed as the original analog audio signal.

Images