JP5657513B2 - Wireless communication system - Google Patents

Description

  The present invention relates to wireless communication technology.

  2. Description of the Related Art In recent years, short-range wireless communication that communicates with weak signals (radio waves and electromagnetic waves) that play a network in a ubiquitous society has attracted attention. The short-range wireless includes a wireless LAN (Local Area Network) having a communication distance of about 100 m, a wireless PAN (Personal Area Network) covering about 10 m to 20 m, and the like. In addition, there is an electric field communication in which communication is performed by inducing an electric field in a transmission medium such as a human body and detecting the induced electric field for the purpose of communication when a person comes close to contact with a communication partner.

Takeo Okamura, “Basic Knowledge of Weak Radio and Low-Power Radio”, Transistor Technology, CQ Publisher, November 2007, p.106 "Weakly used wireless devices", Circuit Design Co., Ltd. [online], [Searched on November 7, 2011], Internet <URL: http://www.circuitdesign.jp/jp/technical/technical_pdf /bijaku.pdf.PDF> Hidenori Oguni, 4 others, “Production of Digital Diversity Receiver Using DSP”, 4th DSPS Educator Conference, August 29, 2002 "Basics of wireless transmission (error rate in fading channels, diversity reception)", [online], Niigata University, Digital Wireless Transmission Engineering 2011 Lecture Materials, [November 7, 2011 Search], Internet <URL: http://telecom0.eng.niigata-u.ac.jp/index.php?plugin=attach&refer=Lecture%2FWCom&openfile=04-wireless-2.pdf>

  Among the above wireless communication systems, in the wireless communication system corresponding to a wireless station (weak wireless) that emits extremely weak radio waves or a low-power wireless station that has an antenna power of 10 mW or less, the signal strength is weak, so the influence of environmental noise It is easy to receive. FIG. 16 shows a conventional wireless communication system. Here, a signal including information to be communicated is transmitted from the antenna 101 of the wireless communication terminal 100 using the wireless communication terminal 100 as a transmitting terminal and the wireless communication terminal 200 as a receiving terminal, and the antenna 201 of the wireless communication terminal 200 is transmitted. Consider the case of receiving by. As shown in FIG. 16, when the noise source that is the source of environmental noise is closer to the wireless communication terminal 200 than the wireless communication terminal 100, the environmental noise is larger than the signal transmitted from the wireless communication terminal 100 and communication is performed. Be disturbed.

  Examples of the noise source include electronic devices such as an electronic display and a signboard, and other wireless communication devices that use the same frequency band as the wireless communication between the wireless communication terminals 100 and 200. The magnitude of environmental noise changes depending on the density and operating conditions of these devices. In the area where the people who become users gather, noise source devices are densely packed, so the environmental noise increases, and the service that uses communication in that area is affected.

  The present invention has been made in view of the above, and an object thereof is to provide a communication system that enables stable communication even in a noisy environment.

Wireless communication system according to the present invention is a wireless communication system for performing short-range wireless communication between the wireless transmission apparatus and the wireless reception apparatus, said wireless transmission apparatus, a first 1, first and second antennas, modulating means for modulating a carrier based on the to be transmitted information, the first buffer in which the modulating means receives the modulation signal modulated, and sent without inverting the phase of the modulation signal from the first first antenna And a second buffer that receives the modulated signal modulated by the modulating means, inverts the phase of the modulated signal and transmits the signal from the first antenna, and before modulating the carrier wave based on the information to be transmitted. carrier a predetermined time period which is not modulated, has a preamble transmission unit for transmitting, the radio receiving apparatus, the second 1, and a second second antenna, a reception signal received by the second first antenna first Unity gain In a first amplifier for amplifying an output of the reception signal received by the second second antenna and a second amplifier for amplifying at a second gain, said first output signal and the second amplifier of the amplifier The amplitude of the first differential amplifier that outputs the difference between the signals and the first differential amplification output signal that is output by the first differential amplifier during the predetermined period is detected, and the fluctuation of the amplitude is minimized. the first such that a first control means for controlling one or both or a second gain, the second 3, the antenna of the second 4, the received signal received by the second third antenna A third amplifier that amplifies the received signal received by the second antenna with a fourth gain, an output signal of the third amplifier, and the third amplifier. a second differential amplifier for outputting the difference between the output signal of the fourth amplifier, the predetermined period To detect the amplitude of the second differential amplifier output signal the second differential amplifier outputs, the third as variations of the amplitude is minimum, either or both of the fourth gain A second control means for controlling the selection, a selection means for selecting a differential amplification output signal having a smaller minimum amplitude variation among the first and second differential amplification output signals, and the selection demodulating means for demodulating said differential amplifier output signal means is selected, the possess, the radio receiving apparatus, and characterized by separating the noise amplitude noise source occurs varies temporally from the received signal To do.

In the wireless communication system, the radio receiving apparatus, and the second 1, second 2, second 3, determining means for determining the polarity of the noise received by any two of the second 4 antennas, Transmitting means for transmitting the determination result of the determination means, wherein the wireless transmission device receives the determination result, and when the determination result indicates that the noise has the same polarity, the first When the first and second buffers are set so that the second buffer transmits the modulated signal whose phase of the modulated signal is inverted, and the determination result indicates that the polarity of the noise indicates a different polarity Sets the first and second buffers so that the first and second buffers transmit the modulated signal having the same phase of the modulated signal, or the modulated signal is transmitted from either one of the buffers. Having setting means to Features.

In the wireless communication system, said determining means, said two antennas removed DC component by multiplying the noise received in each case the potential of the DC component is greater than a first threshold said noise Are determined to be the same polarity, and when the potential of the DC component is lower than the second threshold value, the noise polarity is determined to be different.

In the wireless communication system, the determination unit takes a difference between the noise received by each of the two antennas, compares the magnitude of the amplitude size and the noise amplitude of the difference, the amplitude of the difference When the magnitude is smaller than the amplitude of the noise, the polarity of the noise is determined as the same polarity, and when the magnitude of the difference is larger than the magnitude of the noise, the polarity of the noise is different. The polarity is determined.

In the wireless communication system has a second 1, second 2, second 3, local oscillation means for oscillating a signal of a frequency different from the carrier frequency of the received signal at a second 4 antennas, the second Signals received by the first, second 2, second 3, second and fourth antennas are down-converted.

In the wireless communication system, the second 1, second 2, second 3, analog converts the signal received by the second fourth antenna into a digital signal - characterized by having a digital conversion unit.

  According to the present invention, it is possible to provide a communication system that enables stable communication even in a noisy environment.

It is a functional block diagram which shows the structure of the radio | wireless communications system in 1st Embodiment. It is a figure explaining the principle of isolation | separation of a modulation signal and noise. It is a figure which shows the radio | wireless communications system of a 1st comparative example. It is a figure explaining the principle of isolation | separation of the modulation signal and noise in the radio | wireless communications system of FIG. It is a figure which shows the area | region which satisfy | fills the conditions which can isolate | separate noise. It is a figure which shows the area | region which satisfy | fills another conditions which can isolate | separate noise. It is a functional block diagram which shows the structure of a signal separation part. It is a functional block diagram which shows the structure of a 2 input signal separation part. It is a functional block diagram which shows the structure of another 2 input signal separation part. It is a functional block diagram which shows the structure of another 2 input signal separation part. It is a functional block diagram which shows the structure of the radio | wireless communications system in 2nd Embodiment. It is a functional block diagram which shows the structure of a noise polarity determination part. It is a figure explaining the polarity determination of noise. It is a functional block diagram which shows the structure of another noise polarity determination part. It is a functional block diagram which shows the structure of another noise polarity determination part. It is a figure which shows the conventional radio | wireless communications system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a functional block diagram illustrating a configuration of a wireless communication system according to the first embodiment. The wireless communication system shown in FIG. 1 includes wireless communication terminals 1 and 2. Each of the wireless communication terminals 1 and 2 includes a module having a function of transmitting / receiving, but for simplification, in FIG. 1, only the transmission module is provided in the wireless communication terminal 1 and only the reception module is provided in the wireless communication terminal 2. It is described.

  The wireless communication terminal 1 includes two antennas 11 and 12, a terminal processing unit 13, a modulation unit 14, a non-inverting buffer 15, and an inverting buffer 16. The terminal processing unit 13 inputs a data signal based on information to be transmitted to the modulation unit 14. The modulation unit 14 inputs a modulated signal obtained by modulating a carrier wave having a predetermined frequency with the input data signal to the non-inverting buffer 15 and the inverting buffer 16. The non-inverting buffer 15 outputs a non-inverting modulation signal that does not invert the phase of the modulation signal to the antenna 11 and transmits the non-inverting modulation signal from the antenna 11. The inverting buffer 16 outputs an inverted modulation signal obtained by inverting the phase of the modulation signal to the antenna 12 and transmits the inverted modulation signal from the antenna 12.

  The wireless communication terminal 2 includes four antennas 21, 22, 23, 24, a signal separation unit 25, a demodulation unit 26, and a terminal processing unit 27. Reception signals received by the antennas 21, 22, 23, and 24 are input to the signal separation unit 25. The signal separation unit 25 separates the noise radiated from the surrounding noise sources and received by the antennas 21, 22, 23, and 24 from the reception signals received by the antennas 21, 22, 23, and 24, respectively. A modulated signal obtained by synthesizing the transmitted non-inverted modulated signal and inverted modulated signal is input to the demodulator 26. The demodulator 26 demodulates the modulated signal to obtain a data signal and inputs the data signal to the terminal processor 27. The terminal processing unit 27 performs processing based on the input data signal.

  Next, the operation of separating the modulation signal and noise by the signal separation unit will be described using the model of FIG.

2 indicates the antennas 11, 12, 21, 22, 23, and 24 that transmit and receive modulated signals and noise sources that emit noise. The modulated signals x ₁ and −x ₁ transmitted from the antennas 11 and 12 of the wireless communication terminal 1 and the noise x ₂ radiated from the noise source are attenuated before reaching the antennas 21, 22, 23, and 24. The attenuation rate between the antenna 11 and the antenna 21 is b ₁₁ , the attenuation rate between the antenna 12 and the antenna 21 is b ₁₂ , the attenuation rate between the antenna 11 and the antenna 22 is b ₂₁ , and the attenuation rate between the antenna 12 and the antenna 22 is b ₂₂ , the attenuation rate between the antenna 11 and the antenna 23 is b ₃₁ , the attenuation rate between the antenna 12 and the antenna 23 is b ₃₂ , the attenuation rate between the antenna 11 and the antenna 24 is b ₄₁ , and the attenuation rate between the antenna 12 and the antenna 24. Is b ₄₂ , the attenuation rate between the noise source and the antenna 21 is a ₁₂ , and the attenuation rate between the noise source and the antenna 22 is a ₂₂ . The attenuation rate between the noise source and the antenna 23 is a ₃₂ , and the attenuation rate between the noise source and the antenna 24 is a ₄₂ . Received signals e ₁ , e ₂ , e ₃ , and e ₄ received by the antennas 21, 22, 23, and 24 are expressed by the following equations.

The first term on the right side of each of the equations (1) to (4) is a modulation signal component, and the second term is a noise component. If the difference between the received signals is obtained by weighting e ₁ to e ₄ so as to cancel the noise component, only the modulated signal component remains and the signal-to-noise ratio is improved. Six combinations for eliminating noise components using any _two received signals of received signals e ₁ , e ₂ , e ₃ and e ₄ are shown below.

In the signal separation unit 25, using any two of the formulas (5) to (10), the coefficient of each formula is obtained so that the second term on the right side of the formula to be used is zero, and either one of the formulas is used. The signal separation output obtained by weighting the received signals and taking the difference between the received signals by the equation is input to the demodulator 26. For example, when Expression (7) and Expression (8) are used, the signal separation unit 25 obtains the difference between the received signals e ₁ and e ₄ received by the antennas 21 and 24 in the second term on the right side of Expression (7). and (a ₁₂ -c ₁₄ a ₄₂₎ coefficients c ₁₄ which is zero, took the difference between the received signals e _2, e ₃ received by the antenna 22 and 23 wherein the second term of the right side of (8) (a ₂₂ The coefficient c _{23 at} which −c ₂₃ a ₃₂ ) becomes zero is obtained, and one of the differences is input to the demodulator 26 as a signal separation output. Of the difference between the received signals e ₁ and e _{4 and} the difference between the received signals e ₂ and e ₃ , the difference in which the coefficients c ₁₄ and c ₂₃ are obtained first or the coefficients c ₁₄ and c ₂₃ are obtained. The one with the smallest minimum amplitude variation is selected and input to the demodulator 26.

<When transmitting with one antenna and receiving with two antennas>
Here, the case of transmitting with one antenna and receiving with two antennas of the first comparative example will be described. In the first comparative example, the noise component can be canceled to improve the signal-to-noise ratio, but the modulated signal component may also be canceled depending on the position of the noise source.

FIG. 3 is a diagram illustrating a wireless communication system according to a first comparative example, which includes a wireless communication terminal 100 including one antenna 101, two antennas 201 and 202, a signal separation unit 210, and a demodulation unit 220. The wireless communication terminal 200 is used. Wireless communication terminal 100 transmits the modulated signal x ₁ from the antenna 101, the noise source emits noise x _2. The wireless communication terminal 200 receives the modulated signal x ₁ and the noise x ₂ through the two antennas 201 and 202. The signal separation unit 210 separates the modulation signal x ₁ and the noise x ₂ , and the demodulation unit 220 demodulates the modulation signal x ₁ . The noise source is described as an element that disturbs communication, and is not related to the operation of the communication system. FIG. 4 shows a model of the communication system of FIG.

The attenuation rate between the antenna 101 and the antenna 201 is a ₁₁ , the attenuation rate between the antenna 101 and the antenna 202 is a ₂₁ , the attenuation rate between the noise source and the antenna 201 is a ₁₂ , and the attenuation rate between the noise source and the antenna 202 is a ₂₂ Reception signals e ₁ and e ₂ received by the antennas 201 and 202 are expressed by the following equations.

Also in this case, the first term on the right side of each of the equations (11) and (12) is the term of the modulation signal component, and the second term is the term of the noise component. If the difference between e ₁ and e ₂ is obtained by weighting e ₁ or e ₂ so as to cancel the noise component, only the modulated signal component remains and the signal-to-noise ratio is improved. An equation in which e ₂ is weighted by a coefficient c ₁₂ and subtracted from e ₁ is shown below.

When separating the noise x ₂ , the coefficient c ₁₂ is determined so that (a ₁₂ −c ₁₂ a ₂₂ ) in the second term on the right side of the equation (13) becomes zero. At this time, a ₁₂ / a ₂₂ = If a ₁₁ / a ₂₁ , the first term on the right side is also zero. That is, the modulation signal component is also canceled. Since the attenuation rate a _ij (i = 1, 2, j = 1, 2) is normally positive, there is a possibility that the first term becomes zero when the second term is zero.

<When transmitting with two antennas and receiving with two antennas>
Next, the case of transmitting with two antennas and receiving with two antennas of the second comparative example will be described. In the second comparative example, the noise component can be canceled without canceling the modulation signal component wherever the noise source is, but the positional relationship of the antenna is limited.

Here, it is assumed that the wireless communication terminal 2 shown in FIG. 1 uses only the antennas 21 and 22 to remove noise components from the received signal. When only the antennas 21 and 22 are used, the reception signals e ₁ and e ₂ are received by the antennas 21 and 22, respectively. Therefore, the expression (5) that cancels the noise component using the reception signals e ₁ and e ₂ is used. . When using equation (5), only one of (b ₁₁ -b ₁₂ ) or (b ₂₁ -b ₂₂ ) is negative, that is, the product of (b ₁₁ -b ₁₂ ) and (b ₂₁ -b ₂₂ ). Is negative, the signal-to-noise ratio can be improved regardless of the attenuation factors a ₁₂ and a ₂₂ .

A condition in which only one of (b ₁₁ -b ₁₂ ) or (b ₂₁ -b ₂₂ ) is negative, that is, a condition in which the product of (b ₁₁ -b ₁₂ ) and (b ₂₁ -b ₂₂ ) is negative. Consider. For simplicity, it is assumed that the attenuation factor is inversely proportional to the distance between the antennas. It is known that the electric field or magnetic field radiated from the antenna attenuates in inverse proportion to the distance from the antenna (power is inversely proportional to the square of the distance). As for the antenna directivity, it is assumed that an omnidirectional antenna is used.

As shown in FIG. 2, the distance between the antenna 11 and the antenna 12 of the wireless communication terminal 1 is l _q , and the distance between the antenna 21 and the antenna 22 of the wireless communication terminal 2 is l _e . A line perpendicular to the straight line E12 connecting the antenna 21 and the antenna 22 is drawn from the center of the line segment connecting the antenna 11 and the antenna 12, and an intersection of the vertical line and the straight line E12 is defined as B1. The length of the vertical line is d _r1 , the distance between the antenna 21 and the intersection point B1 is l _e1 , and the distance between the antenna 22 and the intersection point B1 is l _e2 . If the distance is d _s11 , the distance between the antenna 12 and the antenna 21 is d _s12 , the distance between the antenna 11 and the antenna 22 is d _s21 , and the distance between the antenna 12 and the antenna 22 is d _s22 , the distance d _sij between each antenna. (I = 1, 2, j = 1, 2) is expressed by the following equation.

  Here, θ is an angle formed by the straight line E12 and the straight line connecting the antenna 11 and the antenna 12.

Based on the assumption that the attenuation rate is inversely proportional to the distance between the antennas, the attenuation rate b _ij (i = 1, 2, j = 1, 2) is expressed by the following equation using a constant k.

(B ₁₁ -b ₁₂ ) and (b ₂₁ -b ₂₂ ) are expressed by the following equations.

Since the constant k is included in both formula (19) and formula (20), it is not related to the condition in which the product of (b ₁₁ −b ₁₂ ) and (b ₂₁ −b ₂₂ ) is negative. Since d _s11 , d _s12 , d _s21 , and d _s22 are positive real numbers, the condition that the product of (d ² _s12 -d ² _s11 ) and (d ² _s22 -d ² _s21 ) is negative ( b ₁₁ -b ₁₂ ) and (b ₂₁ -b ₂₂ ) are negative conditions.

From formulas (14) to (17), (d ² _s12 -d ² _s11 ) and (d ² _s22 -d ² _s21 ) are expressed by the following formulas.

The product of (d ² _s12 -d ² _s11 ) and (d ² _s22 -d ² _s21 ) from the formula (21) and the formula (22) is expressed by the following formula.

The condition that the right side of Expression (23) is negative is as follows.

Since θ> tan ⁻¹ (l _e1 / d _r ) and θ <−tan ⁻¹ (l _e2 / d _r ) from the equation (24), under the condition of the equation (24), (b ₁₁ −b ₁₂ ) And θ where the product of (b ₂₁ -b ₂₂ ) is negative does not exist. On the other hand, since θ <tan ⁻¹ (l _e1 / d _r ) and θ> −tan ⁻¹ (l _e2 / d _r ) from the equation (25), −tan ⁻¹ (l _e2 / d _r ) <θ <Tan ⁻¹ (l _e1 / d _r ). From the above results, it can be seen that there is a condition in which the product of (b ₁₁ -b ₁₂ ) and (b ₂₁ -b ₂₂ ) is negative. The noise to noise ratio is improved. In other words, when the wireless communication terminal 2 has two antennas, in order to improve the signal-to-noise ratio regardless of the noise source, the wireless communication terminal 1 and the straight line connecting the two antennas of the wireless communication terminal 2 There are restrictions on the angle formed by the straight line connecting the two antennas.

<When transmitting with 2 antennas and receiving with 4 antennas>
Finally, in the case of transmitting with two antennas and receiving with four antennas of the present embodiment, it will be described that the restrictions on the positional relationship of the antennas are relaxed.

Here, the noise components of the received signals e ₁ and e ₄ received by the antennas 21 and 24 and the received signals e ₂ and e ₃ respectively received by the antennas 22 and 23 by the wireless communication terminal 2 shown in FIG. Consider the case of removing. That is, Equation (7) for canceling the noise component using the received signals e ₁ and e ₄ and Equation (8) for canceling the noise component using the received signals e ₂ and e ₃ are used. When using formula (7) and formula (8), either the product of (b ₁₁ -b ₁₂ ) and (b ₄₁ -b ₄₂ ) or the product of (b ₂₁ -b ₂₂ ) and (b ₃₁ -b ₃₂ ) If becomes negative, the signal-to-noise ratio can be improved regardless of the attenuation factors a ₁₂ , a ₂₂ , a ₃₂ , and a ₄₂ .

Similarly to the case of transmitting with two antennas and receiving with two antennas, l _q , l _e1 , l _e2 and d _r1 are defined based on the positional relationship between the antennas 11 and 12 and the antennas 21 and 22. Further, a line perpendicular to the straight line E34 connecting the antenna 23 and the antenna 24 is drawn from the center of the line segment connecting the antenna 11 and the antenna 12, and the intersection of the vertical line and the straight line E34 is defined as B2. The length of the vertical line is d _r2 , the distance between the antenna 23 and the intersection B2 is l _e1 , and the distance between the antenna 24 and the intersection B2 is l _e2 . The distance is d _s11 , the distance between antenna 12 and antenna 21 is d _s12 , the distance between antenna 11 and antenna 22 is d _s21 , the distance between antenna 12 and antenna 22 is d _s22 , and the distance between antenna 11 and antenna 23 is When d _s31 , the distance between the antenna 12 and the antenna 23 is d _s32 , the distance between the antenna 11 and the antenna 24 is d _s41 , and the distance between the antenna 12 and the antenna 24 is d _s42 , the distance d _sij (i = 1, 2, 3, 4, j = 1, 2) is expressed by the following equation.

Using equation (18) and the same damping factor and the distance _{relationship, (b 11 -b 12),} (b 21 -b 22), (b 31 -b 32), (b 41 -b 42) are It is expressed by the following formula.

Since the constant k is included in all of the equations (30) to (33), the product of (b ₁₁ −b ₁₂ ) and (b ₄₁ −b ₄₂ ), (b ₂₁ −b ₂₂ ) and (b ₃₁ − Regardless of the condition under which the product of b ₃₂ ) is negative. Since d _s11 , d _s12 , d _s21 , d _s22 , d _s31 , d _s32 , d _s41 , and d _s42 are positive real numbers, (d ² _s12 −d ² _s11 ) and (d ² _s42 −d It becomes the condition which the product is negative conditions the product of ² _s41) is negative and _{(b 11 -b 12) (b} 41 -b 42), (d 2 s22 -d 2 s21) and (d ² _s32 - The condition that the product of d ² _s31 ) is negative is the condition that the product of (b ₁₁ −b ₁₂ ) and (b ₄₁ −b ₄₂ ) is negative.

From formulas (26) to (29), (d ² _s12 -d ² _s11 ), (d ² _s22 -d ² _s21 ), (d ² _s32 -d ² _s31 ), and (d ² _s42 -d ² _s41 ) are as follows: It is expressed by the following formula.

The product of (d ² _s12 -d ² _s11 ) and (d ² _s42 -d ² _s41 ) from the formula (34) and the formula (37) is expressed by the following formula.

The condition that the right side of Expression (38) is negative is as follows.

From equation (39), tan θ> l _e1 / d _r1 and tan θ> l _e2 / d _r2 , and from equation (40), tan θ <l _e1 / d _r1 and tan θ <l _e2 / d _r2 . An area of tan θ that satisfies these conditions is shown in FIG.

In addition, the product of (d ² _s22 -d ² _s21 ) and (d ² _s32 -d ² _s31 ) from the formula (35) and the formula (36) is expressed by the following formula.

The condition that the right side of Expression (41) is negative is as follows.

From equation (42), tan θ <−l _e2 / d _r1 and tan θ <−l _e1 / d _r2 , and from equation (43), tan θ> −l _e2 / d _r1 and tan θ> −l _e1 / d _r2 . A region of tan θ that satisfies these conditions is shown in FIG.

5 and 6, the product of (d ² _s12 -d ² _s11 ) and (d ² _s42 -d ² _s41 ) or the product of (d ² _s22 -d ² _s21 ) and (d ² _s32 -d ² _s31 ). It can be seen that at least one of them is negative. Therefore, the signal-to-noise ratio is improved regardless of the noise source, without restriction of the angle θ formed by the straight line connecting the antennas 11 and 12 of the wireless communication terminal 1 and the straight line connecting the antennas 21 and 22 of the wireless communication terminal 2. .

  In the above considerations, the explanation is made on the assumption that the attenuation rate is inversely proportional to the distance. However, if attention is paid only to the polarity, the same consideration is valid even if the attenuation rate is inversely proportional to the square or the third power of the distance. Moreover, although the case where the four antennas 21, 22, 23, and 24 are arranged at each vertex of the rectangle has been described, the straight line E12 that connects the antennas 21 and 22 and the straight line E34 that connects the antennas 23 and 24 may be parallel. .

<Signal separation unit>
Next, the signal separation unit will be described.

  FIG. 7 is a functional block diagram of the signal separation unit 25 in the present embodiment.

  The signal separation unit 25 illustrated in FIG. 7 includes two-input signal separation units 251 and 252 and a selection unit 253. The antennas 21 and 24 are connected to the 2-input signal separator 251, and the antennas 22 and 23 are connected to the 2-input signal separator 252.

  Each of the two-input signal separation units 251 and 252 separates noise from the received signals received by the antennas 21, 22, 23, and 24, and outputs a signal separation output that has separated the noise and a separation completion signal indicating that the separation is completed. Input to the selection unit 253.

  When the separation completion signal 1 is input from the 2-input signal separation unit 251, the selection unit 253 outputs the signal separation output 1 of the 2-input signal separation unit 251 to the demodulation unit 26 and outputs the separation completion signal 2 from the 2-input signal separation unit 252. When input, the signal separation output 2 of the 2-input signal separation unit 252 is output to the demodulation unit 26. If the separation completion signal has already been input from either of the two input signal separation units 251 and 252, the signal separation output of the one to which the separation completion signal has been input first is output to the demodulation unit 26. Alternatively, the signal separation output having the smaller minimum value of the amplitude variation of the signal separation output when noise is separated is output to the demodulator 26.

  Next, the 2-input signal separation unit will be described. The two-input signal separation units 251 and 252 may separate independent signals and noise in the process used in the blind signal source separation, but the two-input signal separation unit shown in FIG. 8 may be used. Since both the two-input signal separators 251 and 252 have the same configuration, only the two-input signal separator 251 is shown here.

  The two-input signal separation unit 251 shown in FIG. 8 includes automatic gain adjustment amplification / filter units 31 and 32, a variable gain amplifier 33, a differential amplifier 34, and a monitor / separation control unit 35.

The automatic gain adjustment amplification / filter units 31 and 32 remove unnecessary noises of the received signals e ₁ and e ₄ received by the antennas 21 and 24, respectively, and a period during which the automatic gain adjustment amplification / filter units 31 and 32 have outputs. The gains are adjusted so that the average amplitude at Tag becomes a predetermined amplitude, and the received signals e ₁ and e ₄ are amplified.

The variable gain amplifier 33 amplifies the output signal of the automatic gain adjustment amplification / filter unit 32 with the gain c ₁₄ set by the gain control signal.

  The differential amplifier 34 outputs the difference between the output signal of the automatic gain adjustment amplification / filter unit 31 and the output signal of the variable gain amplifier 33 as a signal separation output.

The monitor / separation control unit 35 minimizes the fluctuation of the amplitude of the signal separation output so that the noise component is separated from the signal separation output of the differential amplifier 34 and the signal component transmitted by the wireless communication terminal 1 becomes dominant. the gain c ₁₄ consisting determined, the gain control signal for setting the gain c ₁₄ outputs to the variable gain amplifier 33, and transmits the separated completion signal to the selector 253.

The wireless communication terminal 1 transmits a non-modulated carrier wave (preamble) for a predetermined period before modulating the predetermined carrier wave with a data signal based on information to be transmitted, and the wireless communication terminal 2 separates noise during this period. Processing for obtaining the optimum gain c ₁₄ is performed. The preamble amplitude is constant and hardly fluctuates, whereas the noise amplitude is not constant, so the amplitude fluctuation is large. Therefore, the monitor / separation control unit 35 changes the gain set in the variable gain amplifier 33 and obtains the magnitude of fluctuation in the amplitude of the signal separation output of the differential amplifier 34 within a predetermined period for each set gain. The gain that minimizes the amplitude fluctuation of the signal separation output is set as the optimum gain c ₁₄ for separating noise. In this way, since the gain c ₁₄ set in the variable gain amplifier 33 is obtained immediately before receiving the data signal based on the information to be transmitted, the situation (propagation constant) around the wireless communication terminal 2 changes with time. Even so, it is possible to effectively separate the modulation signal and noise.

  In the above description, the variable gain amplifier 33 is connected to the automatic gain adjustment amplification / filter unit 32. However, the variable gain amplifier is connected to both of the automatic gain adjustment amplification / filter units 31 and 32 to adjust both gains. But you can. At this time, if the gain of one variable gain amplifier is set to 1, it becomes the same as the two-input signal separation unit 251 shown in FIG.

In the two-input signal separation unit 251 shown in FIG. 8, the received signals e ₁ and e ₄ received by the antennas 21 and 24 are directly signal-processed, but as in the modification of the two-input signal separation unit shown in FIG. The received signals e ₁ and e ₄ may be down-converted with a signal having a predetermined frequency output from the local oscillator 36, and then the modulated signal and noise may be separated.

  Further, as in the modification of the signal separation unit shown in FIG. 10, analog-digital conversion units 37, 38 are provided, and the digital gain signal is processed after analog-to-digital conversion of the outputs of the automatic gain adjustment amplification / filter units 31, 32. Thus, the modulation signal and noise may be separated. In this case, the adder obtains the difference between the digital signal converted by the analog-digital converter 37 and the digital signal converted by the analog-digital converter 38 and multiplied by the magnification output from the monitor / separation controller 35. Output to the monitor / separation control unit 35. The monitor / separation control unit 35 obtains amplitude data by performing a peak hold operation, that is, searching for the maximum value or the minimum value in digital signal processing, and outputs the signal output from the addition unit. The magnification of the output of the analog-digital converter 38 is determined so that the amplitude is minimized.

As described above, according to the present embodiment, the wireless communication terminal 1 transmits the non-inverted modulation signal and the inverted modulation signal with the two antennas 11 and 12, and the wireless communication terminal 2 has the four antennas 21, 22, 23, 24 receive received signals e ₁ , e ₂ , e ₃ , e ₄ , and the two-input signal separators 251, 252 receive amplitude fluctuations of the difference between the received signals e ₁ , e ₄ , received The gain that minimizes the fluctuation of the amplitude of the difference between the signals e ₂ and e ₃ is obtained, and the separated signal output of either one of the two-input signal separation units 251 and 252 is demodulated, thereby obtaining the antenna 11 of the wireless communication terminal 1, 12 and the antennas 21, 22, 23, 24 of the wireless communication terminal 2 can be provided, and a wireless communication system capable of improving the signal-to-noise ratio can be provided wherever noise sources are located.

  As the antennas 21, 22, 23, and 24, electrodes arranged on the left and right sides of the gate as disclosed in Japanese Patent Application Laid-Open No. 2011-199395 may be used.

[Second Embodiment]
FIG. 11 is a functional block diagram illustrating a configuration of a wireless communication system according to the second embodiment. The wireless communication system shown in FIG. 11 includes wireless communication terminals 4 and 5. Each of the wireless communication terminals 4 and 5 includes a module having a function of transmitting / receiving, but for simplification, in FIG. 11, only the transmission module is provided for the wireless communication terminal 4 and only the reception module is provided for the wireless communication terminal 5. It is described.

  In the present embodiment, before performing wireless communication, the polarity of noise received using any two of the four antennas of the wireless communication terminal 5 is determined and the determination result is transmitted to the wireless communication terminal 4. When the determination result shows that the noise polarity is the same polarity, the wireless communication terminal 4 transmits a modulation signal having different polarities with the two antennas, and the determination result shows that the noise polarity shows the different polarity. Transmits the modulation signal from only one of the two antennas with the same polarity modulation signal or the two antennas.

  The wireless communication terminal 4 includes two antennas 41 and 42, a terminal processing unit 43, a modulation unit 44, polarity switching buffers 45 and 46, a demodulation unit 47, and transmission / reception changeover switches 48 and 49.

  The terminal processing unit 43 inputs a data signal based on information to be transmitted to the modulation unit 44. In addition, based on the information indicating the polarity of noise received from the wireless communication terminal 5, the terminal processing unit 43 performs non-inversion on either one of the polarity switching buffers 45 and 46 if the noise polarity is the same polarity, The polarity switching buffers 45 and 46 are set so as to transmit the non-inverted modulation signal and the inverted modulation signal in which the phases of the modulation signals are inverted with respect to each other. The polarity switching buffers 45 and 46 are set so that both are non-inverted or inverted and the modulation signals having the same phase are transmitted, or the modulation signal is transmitted from either one of the polarity switching buffers 45 and 46. The polarity switching buffers 45 and 46 are set in

  The modulation unit 44 inputs a modulation signal obtained by modulating a carrier wave having a predetermined frequency with the input data signal to the polarity switching buffers 45 and 46.

  The polarity switching buffers 45 and 46 set whether to function as a non-inverted buffer or an inverted buffer based on the polarity switching signal input from the terminal processing unit 43, and transmit / receive a non-inverted modulation signal or an inverted modulation signal. The signal is output to the antennas 41 and 42 via the changeover switches 48 and 49.

  The transmission / reception changeover switches 48 and 49 connect the antennas 41 and 42 to the polarity switching buffers 45 and 46 during transmission, and connect the antennas 41 and 42 to the demodulation unit 47 during reception.

  The demodulator 47 demodulates the modulated signal transmitted from the wireless communication terminal 5 to obtain information indicating the polarity of noise and inputs the information to the terminal processor 43.

  The wireless communication terminal 5 includes four antennas 51, 52, 53, 54, a signal separation unit 55, a demodulation unit 56, a terminal processing unit 57, a noise polarity determination unit 58, a modulation unit 59, and transmission / reception changeover switches 60, 61. , 62, 63.

  Reception signals received by the antennas 51, 52, 53, 54 are input to the signal separation unit 55 via the transmission / reception change-over switches 60, 61, 62, 63.

  The signal separation unit 55 separates noise from the reception signals received by the antennas 51, 52, 53, and 54, and inputs the modulation signal transmitted from the wireless communication terminal 4 to the demodulation unit 56.

  The demodulator 56 demodulates the modulated signal to obtain a data signal and inputs it to the terminal processor 57.

  The terminal processing unit 57 performs processing based on the input data signal. In addition, a data signal based on information indicating the polarity of noise determined by the noise polarity determination unit 58 is input to the modulation unit 59.

  The noise polarity determination unit 58 determines the polarity of noise based on the noise received by each of the antennas 51, 52, 53, 54 before starting wireless communication with the wireless communication terminal 4, and inputs it to the terminal processing unit 57. To do.

  The modulation unit 59 modulates a carrier wave of a predetermined frequency with a data signal based on the input information indicating the polarity of noise, and modulates the modulated signal via the antennas 51, 52, 53 via the transmission / reception change-over switches 60, 61, 62, 63. , 54.

  FIG. 12 shows a configuration example of the noise polarity determination unit 58. The noise polarity determination unit 58 shown in FIG. 12 multiplies the noise received by the antennas 51 and 54 by the multiplication unit 581, extracts the DC component by the low-pass filter unit 582, and extracts the DC component potential extracted by the determination unit 583. To determine the polarity of noise.

  When the noise received by the antennas 51 and 54 has the same polarity, as shown in FIG. 13, the output of the low-pass filter unit 582 has a high potential, and when the noise has a different polarity, the low-pass The output of the filter unit 582 becomes a low potential. The determination unit 583 sets a threshold value 1 on the high potential side and a threshold value 2 on the low potential side across the center potential, and if the output of the low pass filter unit 582 is higher than the threshold value 1, When it is determined that the noise of the polarity is received and the output of the low-pass filter unit 582 is lower than the threshold value 2, it is determined that the noise of the different polarity is received and a determination signal is output. When the output of the low-pass filter unit 582 is between the threshold value 1 and the threshold value 2, it is determined that the noise is small. In this case, the radio communication terminal 4 may set the polarity switching buffers 45 and 46 in any way. Note that the low potential referred to here is a potential lower than the center potential. For example, when the center potential is zero, the potential is a negative potential. The center potential varies depending on the power supply voltage applied to the circuit. For example, in the case of a single power supply, it is an intermediate potential between the ground and the power supply voltage (which can be either positive or negative). It becomes an intermediate potential between the power supply voltage of the potential and the power supply voltage of the negative potential. Similarly, the high potential is higher than the center potential.

  FIG. 14 is a modification of the noise polarity determination unit 58. The noise polarity determination unit 58 shown in FIG. 14 takes the difference between the noises received by the antennas 51 and 54 by the differential amplifier 34 with the gain of the variable gain amplifier 33 set to 1, and the noise polarity determination unit 58 performs differential operation. The polarity of the noise is determined by comparing the amplitude of the amplifier output with the amplitude of the received noise. When the noise has the same polarity, the amplitude of the differential amplifier output becomes smaller than the amplitude of the noise, and when the noise has a different polarity, the amplitude of the differential amplifier output becomes larger than the amplitude of the noise.

  In the above description, the polarity of noise received by the antennas 51 and 54 is determined. However, the polarity of noise received by any two antennas may be determined. Further, as shown in FIG. 15, using four antennas 51, 52, 53, 54, the polarity of noise received by the antennas 51, 54 is changed to a multiplier 584 of the noise polarity determination unit 58, a low-pass filter unit. It may be determined by the determination unit 583 and the polarity of the noise received by the antennas 52 and 53 by the multiplication unit 581, the low-pass filter unit 582, and the determination unit 583 of the noise polarity determination unit 58. As shown in FIG. 14, the polarity of the noise is determined by comparing the signal separation output of each of the separation processing units 39 of the two-input signal separation units 551 and 552 with the amplitude of the noise received by the antennas 51 and 54 and the antennas 52 and 53. May be.

  The two-input signal separation units 551 and 552 may separate the independent signal and noise in the process used in the blind signal source separation, but the two-input signal shown in FIGS. 7 to 9 of the first embodiment. A signal separation unit 251 may be used.

  As described above, according to the present embodiment, before performing wireless communication, the wireless communication terminal 5 multiplies the noise received by the antennas 51 and 54 to extract the DC component, and based on the potential of the DC component. By determining the polarity of noise and notifying the wireless communication terminal 4 and setting the polarity of the modulation signal transmitted by the antennas 41 and 42 based on the polarity of the noise, the wireless communication terminal 4 modulates according to the communication environment. A signal can be transmitted.

DESCRIPTION OF SYMBOLS 1, 2 ... Wireless communication terminal 11, 12, 21, 22, 23, 24 ... Antenna 13 ... Terminal processing part 14 ... Modulation part 15 ... Non-inversion buffer 16 ... Inversion buffer 25 ... Signal separation part 251, 252 ... 2 input signal Separation unit 253 ... Selection unit 26 ... Demodulation unit 27 ... Terminal processing unit 31, 32 ... Automatic gain adjustment amplification / filter unit 33 ... Variable gain amplifier 34 ... Differential amplifier 35 ... Monitor / separation control unit 36 ... Local oscillators 37, 38 ... Analog-to-digital conversion unit 39 ... separation processing unit 4,5 ... wireless communication terminals 41, 42, 51, 52, 53, 54 ... antenna 43 ... terminal processing unit 44 ... modulation unit 45,46 ... polarity switching buffer 47 ... demodulation Units 48, 49... Transmission / reception changeover switch 55... Signal separation unit 551, 552... 2 Input signal separation unit 553... Selection unit 56 .. Demodulation unit 57. Polarity determination unit 581, 584 ... Multiplication unit 582, 585 ... Low pass filter unit 583 ... Determination unit 59 ... Modulation unit 60, 61, 62, 63 ... Transmission / reception changeover switch 100, 200 ... Wireless communication terminal 101, 201, 202 ... Antenna 210 ... Signal separation unit 220 ... Demodulation unit

Claims (6)

A wireless communication system that performs short-range wireless communication between a wireless transmission device and a wireless reception device,
The wireless transmission device
A first 1, first and second antennas,
Modulation means for modulating a carrier wave based on information to be transmitted;
A first buffer the modulating means inputs a modulated signal modulated, transmitted from the first one antenna without inverting the phase of the modulation signal,
A second buffer that receives the modulated signal modulated by the modulating means, inverts the phase of the modulated signal, and transmits it from the first antenna;
Preamble transmitting means for transmitting, for a predetermined period, a carrier wave that is not modulated before modulating the carrier wave based on information to be transmitted ;
The wireless receiver is
A second 1, second 2 antenna,
A first amplifier for amplifying a received signal received by the second antenna with a first gain;
A second amplifier for amplifying a reception signal received by the second antenna with a second gain;
A first differential amplifier that outputs a difference between an output signal of the first amplifier and an output signal of the second amplifier;
In the predetermined period, the amplitude of the first differential amplification output signal output from the first differential amplifier is detected, and either of the first gain and the second gain is set so that the fluctuation of the amplitude is minimized. A first control means for controlling either or both of them;
Second , second and fourth antennas;
A third amplifier for amplifying the reception signal received by the second and third antennas with a third gain;
A fourth amplifier for amplifying a reception signal received by the second antenna with a fourth gain;
A second differential amplifier that outputs a difference between an output signal of the third amplifier and an output signal of the fourth amplifier;
During the predetermined period, the amplitude of the second differential amplification output signal output from the second differential amplifier is detected, and any of the third and fourth gains is set so that the fluctuation of the amplitude is minimized. A second control means for controlling one or both;
Selecting means for selecting a differential amplified output signal having a smaller minimum value of the amplitude variation among the first and second differential amplified output signals;
Have a, demodulating means for demodulating said differential amplifier output signal selected by the selecting unit,
The radio receiving apparatus separates noise generated by a noise source whose amplitude varies with time from a received signal . The wireless receiver is
The second 1, and the second 2, second 3, determining means for determining the polarity of the noise received by any two of the second 4 antennas,
Transmitting means for transmitting the determination result of the determination means,
The wireless transmission device
When the determination result is received, and the determination result indicates that the polarity of the noise indicates the same polarity, the first and second buffers transmit the modulation signal in which the phases of the modulation signals are inverted. When the first and second buffers are set and the determination result indicates that the noise has a different polarity, the first and second buffers transmit the modulation signal having the same phase of the modulation signal. The wireless communication system according to claim 1, further comprising setting means for setting the first and second buffers so as to transmit the modulated signal from either one of the buffers. The determination means, said retrieval two antennas DC component by multiplying the noise received in each case the potential of the DC component is greater than the first threshold value having the same polarity to the polarity of the noise 3. The wireless communication system according to claim 2, wherein when the potential of the direct current component is lower than a second threshold value, the noise is determined to have a different polarity. The determination unit takes a difference between the noise received by each of the two antennas, compares the magnitude of the amplitude size and the noise amplitude of the difference, the amplitude of the difference is the noise If the amplitude is smaller than the amplitude of the noise, the polarity of the noise is determined to be the same polarity, and if the amplitude of the difference is larger than the amplitude of the noise, the polarity of the noise is determined to be different. The wireless communication system according to claim 2, wherein: The second 1, second 2, second 3, has a local oscillation means for oscillating a signal of a frequency different from the carrier frequency of the second signal received by the fourth antenna, the second 1, second 2, the wireless communication system according to any one of claims 1 to 4, characterized in that the second 3, down-converts the signal received by the second 4 antennas. According to any one of claims 1 to 5, characterized in that it has a digital converter - the second 1, second 2, second 3, the signal received by the second 4 antennas analog into a digital signal Wireless communication system.

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