JP4884442B2 - Radio receiving apparatus and radio communication system - Google Patents

Description

  The present invention relates to a radio reception apparatus and radio communication system that perform radio communication using radio waves.

  Wireless communication using megahertz band radio waves is used in various fields. For example, in an electric power company, a robot telemeter at a hydroelectric power plant measures the water level and flow rate of a dam. And a hydroelectric power station transmits a measurement result to a power station regularly by radio | wireless communication (for example, refer patent document 1). Based on the received data, the power station performs operation management of hydroelectric power stations and substations and supplies electricity stably to consumers.

  By the way, hydroelectric power stations and dams are provided in mountainous areas because they use river water. For this reason, the measurement result of the water level and flow rate of the river is transmitted by radio communication from the hydroelectric power station to the power station through a fixed line of 70 MHz band. At this time, since the hydroelectric power plant is provided in the mountainous area and the power plant is provided in a flat part such as an urban area, mountain diffraction is used for wireless communication from the hydroelectric power plant to the power plant. At power stations, radio waves are directly received by mountain diffraction, and at the same time, reflected waves on the ground surface are received. That is, as shown in FIG. 1 described later, two radio waves may be combined. For this reason, as shown in FIG. 8, a height pattern, which is a strength pattern of the electric field strength of the synthesized radio wave, is generated depending on the reception point of the radio wave. The height pattern is formed according to the height of the reception point.

  When a height pattern occurs, if a radio wave is received at a receiving point with a weak electric field strength, sufficient signal strength cannot be obtained, and measurement data may be lost. In order to prevent such data loss, for example, when receiving with the antenna 101 shown in FIG. 9, the antenna 101 is moved in the vertical direction (direction 111 and reverse direction) along the pole 102 using a driving device (not shown). ) And receive radio waves at a receiving point with strong electric field strength.

In addition, when the driving device of the antenna 101 cannot be installed on the pole 102, a large antenna may be used.
JP-A-5-281000

  By the way, when receiving the radio wave in which the height pattern described above is received, when the antenna 101 is driven in the vertical direction, a driving device is required, and this driving device needs to be installed on the pole 111. In addition, when a large antenna is used instead of installing the driving device, the force that the antenna receives with the wind increases, so it is necessary to use a strong pole 111.

  Furthermore, in a fixed line using mountain diffraction, the diffracting point of the radio wave is affected by the shape of the ridge line, and the arrival direction of the radio wave is not constant due to weather conditions such as snow and rain. In this case, it is necessary not only to move the antenna 101 up and down to accommodate the height pattern, but also to adjust the direction 101 of the antenna.

  The object of the present invention is to solve the above problems and eliminate the need to move or adjust the antenna when receiving a radio wave whose electric field intensity has changed due to a height pattern or when responding to a change in the arrival direction of the radio wave. It is an object of the present invention to provide a wireless reception device and a wireless communication system that can perform the above-described operation.

  In order to solve the above-mentioned problem, the invention of claim 1 is characterized in that an antenna that is arranged apart from each other in the vertical direction, receives radio waves and outputs a high-frequency signal, and first and second ports are connected to the antenna, respectively. And the third and fourth ports output the synthesized high-frequency signal, and radio waves are transmitted between the first and third ports, the first and fourth ports, and the second and third ports. A quarter-wave electrical length transmission path is connected, and a three-quarter wavelength electrical length transmission path is connected between the second and fourth ports. The rat race circuit, and the first to fourth contacts are connected to the first to fourth ports of the rat race circuit, respectively, and one of the contacts is selected and connected to the next stage; The first and second contacts from the first and second ports, respectively The first and second ports are connected through an electrical length transmission line with an infinite impedance, and the impedance when the third and fourth contacts are viewed from the third and fourth ports, respectively, is zero. The wireless receiving device is characterized in that the third and fourth ports are connected through a transmission path of electrical length.

  In the invention of claim 1, two antennas are used. The two antennas are arranged apart from each other in the vertical direction, receive radio waves, and output high-frequency signals. In the first aspect of the invention, the following characteristics of the transmission line forming the rat race circuit are utilized. When the electrical length of the cable of the transmission line is λ / 4, when one end is opened, the impedance viewed from the other end becomes zero. Conversely, when one end is short-circuited, the impedance viewed from the other end becomes infinite.

  In this state, when the first contact is selected by the switch circuit, the impedance of the rat race circuit viewed from the first port is all infinite, and only one antenna is connected to the first port. Connected. As a result, the switch circuit outputs a high-frequency signal from one antenna. Similarly, when the second contact is selected by the switch circuit, only the other antenna is connected to the second port of the rat race circuit. As a result, the switch circuit outputs a high-frequency signal from the other antenna.

  When the third contact is selected by the switch circuit, the synthesized high frequency signal is output from the third port when the high frequency signals from the two antennas are in phase due to the characteristics of the rat race circuit. Similarly, when the fourth contact is selected by the switch circuit, the fourth port outputs the synthesized high frequency signal when the high frequency signals from the two antennas are in reverse phase.

  According to a second aspect of the present invention, in the wireless receiver according to the first aspect, the first to fourth contacts of the switch circuit are opened, the first and second ports of the rat race circuit, and the first and second ports of the switch circuit. The second contact point is connected to a half-wavelength electrical length transmission line or a transmission length that is an integral multiple of the half-wavelength length, respectively. The third and fourth ports and the third and fourth contacts of the switch circuit have a quarter-wavelength electrical length transmission line or an odd-numbered quarter-wavelength electrical length. Each is connected by a transmission line.

  According to a third aspect of the present invention, in the wireless receiver according to the first or second aspect, the first to fourth contacts of the switch circuit are short-circuited, and the first and second ports of the rat race circuit and the first of the switch circuit are connected. The first and second contacts are connected to each other by a quarter-wavelength electrical length transmission line, and the third and fourth ports of the rat race circuit and the third and fourth contacts of the switch circuit Are connected by a transmission line having an electrical length of a half wavelength.

  According to a fourth aspect of the present invention, in the wireless reception device according to any one of the first to third aspects, the two antennas are arranged at a distance that is an odd multiple of the half wavelength of the radio wave to be received. It is characterized by that.

  According to a fifth aspect of the present invention, in the wireless reception device according to any one of the first to fourth aspects, each transmission path of the rat race circuit and each transmission path connecting the rat race circuit and the switch circuit are coaxial. It is formed by a transmission line having a structure.

  A sixth aspect of the present invention is a wireless communication system using the wireless reception device according to any one of the first to fifth aspects, wherein a plurality of the same signals are sequentially transmitted when the signals are transmitted. A control unit that controls the switch circuit of the wireless reception device to sequentially select one of the contacts and connect to the next-stage receiver at a timing at which the transmission device transmits a signal; A wireless communication system is provided.

  According to a seventh aspect of the present invention, in the wireless communication system according to the sixth aspect, when the control unit receives a signal reproduced from the high-frequency signal from the receiver, the control unit detects an error in each signal, and the error is detected. It is characterized by outputting a signal with no signal.

  The invention according to claim 8 is a wireless communication system including, on the transmission side, the wireless reception device according to any one of claims 1 to 5 as a wireless transmission device, and is provided at the transmission side and transmits signals. In the switch circuit, one of the contacts is sequentially selected and controlled to connect to the previous transmitter, and when receiving the signal, the signal is transmitted at the transmission side. A wireless communication system comprising: a receiving device that sequentially receives the signals.

  According to the first aspect of the present invention, when the first or second contact is selected by the switch circuit, the switch circuit outputs a high-frequency signal from one antenna or the other antenna. Moreover, since the two antennas are installed in the vertical direction, it is possible to receive radio waves corresponding to the height pattern. When the third contact is selected by the switch circuit, the third port outputs the high frequency signal when the high frequency signals from the two antennas are in phase. At this time, the directivity formed by the two antennas arranged in the vertical direction is formed in a low direction. As a result, when radio waves arrive from a lower direction, a signal obtained by synthesizing in-phase high-frequency signals is output. When the fourth contact is selected by the switch circuit, the fourth port outputs a high frequency signal when the high frequency signals from the two antennas are in reverse phase. At this time, the directivity formed by the two antennas arranged in the vertical direction is formed in a high direction. As a result, when radio waves arrive from a higher direction, a signal obtained by synthesizing high-frequency signals of opposite phases is output. As a result, it is possible to receive radio waves in response to changes in the arrival direction of radio waves. That is, according to the first aspect of the present invention, it is possible to cope with a case where a height pattern radio wave is received and a change in the arrival direction of the radio wave.

  According to the second and third aspects of the invention, since the rat race circuit and the switch circuit are connected using two types of transmission lines, the connection structure between the rat race circuit and the switch circuit can be simplified. it can.

  According to the invention of claim 4, when the two antennas are arranged apart by an odd multiple of the half wavelength of the radio wave to be received, the radio wave comes from the direction intersecting the arrangement direction of the two antennas. The high-frequency signal of the positive phase is synthesized and output. Further, when radio waves arrive from the arrangement direction of the two antennas, high-frequency signals having opposite phases are synthesized and output. As a result, the antenna can have directivity for selecting radio waves in the direction intersecting with the arrangement direction of the two antennas and in the arrangement direction of the two antennas.

  According to the invention of claim 5, since each transmission path of the rat race circuit and each transmission path connecting the rat race circuit and the switch circuit are formed by the transmission path of the coaxial structure, it is simple and inexpensive. A rat race circuit and a circuit connecting the rat race circuit and the switch circuit can be formed.

  According to the invention of claim 6, one of the contacts is sequentially selected and connected to the next stage with respect to the switch circuit of the wireless receiver. As a result, a plurality of signals from the transmission device are received corresponding to the height pattern and corresponding to the arrival direction of the radio wave, so that the signals from the transmission device can be reliably output.

  According to the seventh aspect of the present invention, since a signal with no error is output from among the signals reproduced by the receiver, the signal from the transmission device can be reliably output.

  According to the eighth aspect of the present invention, when there is a possibility that a height pattern is generated, a signal is transmitted on the transmission side so as to correspond to the height pattern on the basis of the same principle as in the first aspect of the present invention. Enables reliable reception of signals.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
In this embodiment, a case where measurement results such as a river water level and a flow rate measured by a hydroelectric power station of an electric power company are transmitted to the power station by radio waves is taken as an example. A radio communication system according to this embodiment is shown in FIG. The wireless communication system of FIG. 1 includes a robot telemeter 1 and a transmission device 2 installed in a hydroelectric power plant or a dam, and a wireless reception device 3 installed in a power plant.

  The robot telemeter 1 installed in the hydroelectric power station or dam automatically measures the water level and flow rate of the river, and sends measurement data as measurement results to the transmitter 2. When the transmission device 2 receives the measurement data from the robot telemeter 1, the transmission device 2 transmits the measurement data to the power station using radio waves. In order to transmit the measurement data, a fixed line using a 70 MHz band radio wave is used. At this time, since there is a mountain M between the hydroelectric power plant and the power plant, the mountain diffraction M1 is used when installing the fixed line.

  Further, the transmission device 2 of the hydroelectric power station transmits measurement data to the power station as follows. The transmission device 2 sets four transmissions of the same measurement data as a set, and transmits the set of measurement data at a predetermined time interval. For example, the transmission device 2 transmits a set of measurement data to the wireless reception device 3 six times a day. In addition, when transmitting a set of measurement data, the transmission device 2 sequentially transmits the four measurement data at a fixed interval.

  A radio receiver 3 according to this embodiment for receiving such measurement data is shown in FIG. The radio receiving apparatus in FIG. 2 includes a first antenna 10 and a second antenna 20, and a receiving unit 30.

The first antenna 10 and the second antenna 20 are Yagi / Uda antennas in which five antenna elements are arranged, but antennas having different numbers of elements can be used. The first antenna 10 and the second antenna 20 send a high-frequency signal to the receiving unit 30 when receiving radio waves from the hydroelectric power plant. The first antenna 10 and the second antenna 20 are fixed to the pole 102 apart from each other, the second antenna 20 is on the ground surface side, and the first antenna 10 is above the second antenna 20. It is arranged. The first antenna 10 and the second antenna 20 are arranged as follows. Assuming that the wavelength of the radio wave used in the fixed line, that is, the carrier wave is λ, the interval S from the first antenna 10 to the second antenna 20 is:
S = (λ / 2) · (2n + 1)
It is. Where the value n is
n = 0, 1, 2,..., k (natural number)
It is a number. That is, the distance between the first antenna 10 and the second antenna 20 is an odd multiple of the half wavelength of the carrier wave. In this embodiment, the interval S is
S = λ / 2
It is.

By arranging the first antenna 10 and the second antenna 20 apart from each other by λ / 2, the directivity shown in FIG. 3 is formed when receiving radio waves from the hydroelectric power station. In addition, the member shown with the code | symbol 11-15 in the figure and the member shown with the codes | symbols 21-25 are the antenna elements of the 1st antenna 10 and the 2nd antenna 20. FIG. When the radio waves arriving at the first antenna 10 and the second antenna 20 are in phase, that is, when the signal phase difference φ between the first antenna 10 and the second antenna 20 is 0 degrees (positive phase), combined directivity characteristic Ar ₀ shown in FIG. 3 (a) is formed. According to the combined directivity characteristic Ar ₀ , when the direction of radio wave arrival is the arrival direction D with respect to the first antenna 10 and the second antenna 20, that is, between the first antenna 10 and the second antenna 20. When the direction intersects the arrangement direction, the first antenna 10 and the second antenna 20 are separated from each other by λ / 2, so that the gain increases in the arrival direction D and in the opposite direction. However, the first antenna 10 and the second antenna 20 are Yagi / Uda antennas and have directivity. As a result, the first antenna 10 and second antenna 20, for the low-angle radio waves coming, combined directivity characteristic AR ₀ with a high gain is formed.

Further, when the radio waves arriving at the first antenna 10 and the second antenna 20 are in reverse phase, that is, the signal phase difference φ between the first antenna 10 and the second antenna 20 is 180 degrees (reverse phase). In some cases, a combined directivity characteristic Ar ₁₈₀ shown in FIG. 3B is formed. According to the combined directivity characteristic Ar ₁₈₀ , the direction in which radio waves come to the first antenna 10 and the second antenna 20 is a direction intersecting the arrival direction D (hereinafter referred to as “arrival direction U”). In this case, that is, in the arrangement direction of the first antenna 10 and the second antenna 20, since the first antenna 10 and the second antenna 20 are separated by λ / 2, the arrival direction U and vice versa Gain increases in direction. However, as described above, the first antenna 10 and the second antenna 20 are Yagi / Uda antennas and have directivity. As a result, the first antenna 10 and the second antenna 20 form a combined directivity characteristic AR ₁₈₀ having a high gain for incoming radio waves at a high angle.

  The first antenna 10 and the second antenna 20 are connected to the rat race circuit 31 through a coaxial transmission line. The transmission path of the coaxial structure that connects the first antenna 10 and the second antenna 20 is arbitrary as long as it has the same length.

  As shown in FIG. 4, the reception unit 30 includes a rat race circuit 31, a connection unit 32, a selection switch circuit 33, a receiver 34, and a control unit 35.

The rat race circuit 31 of the receiving unit 30 is a circuit formed using a transmission line such as a coaxial transmission line. In this embodiment, a rat race circuit 31 shown in FIG. 5 is used. The rat race circuit 31 has four ports P1 to P4. Ports P1 and P2 are input terminals, and ports P3 and P4 are output terminals. Port P1, a first antenna 10, interposed the connection portion 32 is connected to the contact point 33B ₁ of the selection switch circuit 33, port P2 includes a second antenna 20, interposed the connection portion 32 selects It is connected to the contact point 33B ₂ of the switch circuit 33. The port P3 is interposed a connecting part 32 is connected to the contact 33B ₃ of the selection switch circuit 33, the port P4 is connected to the contact 33B ₄ of the selection switch circuits 33 and connection 32 interposed to. The contacts 33B _{1 to} 33B ₄ of the selection switch circuit 33 will be described later.

  A coaxial transmission line 31A having an electrical length of λ / 4 is connected between the port P1 and the port P3 of the rat race circuit 31, and an electrical wave of λ / 4 is connected between the port P1 and the port P4. A length coaxial transmission line 31B is connected. Also, a coaxial transmission line 31C having an electrical length of λ / 4 is connected between the port P2 and the port P3, and an electrical length of 3λ / 4 is connected between the port P2 and the port P4. A coaxial transmission line 31D is connected. Each coaxial transmission line 31A to 31D is a transmission line through which a high-frequency signal flows.

The rat race circuit 31 operates as follows. In FIG. 5, when the clockwise direction is the direction of the arrow A and the counterclockwise direction is the direction of the arrow B, the high frequency signal input to the port P1 is
Clockwise ... λ / 4 (coaxial transmission line 31A)
Counterclockwise: λ / 4 (coaxial transmission line 31B), 3λ / 4 (coaxial transmission line 31D), λ / 4 (coaxial transmission line 31C)
The port P3 is reached through both routes. At this time, the clockwise signal is delayed by λ / 4, and the counterclockwise signal is delayed by 5λ / 4, that is, λ / 4. As a result, a high frequency signal delayed by λ / 4 is output from the port P3 due to the high frequency signal input to the port P1.

The high frequency signal input to port P2 is
Clockwise: 3λ / 4 (coaxial transmission line 31D), λ / 4 (coaxial transmission line 31B), λ / 4 (coaxial transmission line 31A)
Counterclockwise ... λ / 4 (coaxial transmission line 31C)
The port P3 is reached through both routes. At this time, the clockwise signal is delayed by 5λ / 4, that is, λ / 4, and the counterclockwise signal is delayed by λ / 4. As a result, a high frequency signal delayed by λ / 4 is output from the port P3 due to the high frequency signal input to the port P2.

  Therefore, at port P3, the high frequency signal delayed by λ / 4 generated at the input to port P1 and the high frequency signal delayed at λ / 4 generated at the input to port P2 are combined.

On the other hand, the high frequency signal input to the port P1 is
Clockwise: λ / 4 (coaxial transmission line 31A), λ / 4 (coaxial transmission line 31C), 3λ / 4 (coaxial transmission line 31D)
Counterclockwise ... λ / 4 (coaxial transmission line 31B)
The port P4 is reached via both routes. At this time, the clockwise signal is delayed by 5λ / 4, that is, λ / 4, and the counterclockwise signal is delayed by λ / 4. As a result, a high frequency signal delayed by λ / 4 is output from the port P4 due to the high frequency signal input to the port P1.

The high frequency signal input to port P2 is
Clockwise ... 3λ / 4 (coaxial transmission line 31D)
Counterclockwise: λ / 4 (coaxial transmission line 31C), λ / 4 (coaxial transmission line 31A), λ / 4 (coaxial transmission line 31B)
The port P4 is reached via both routes. At this time, the clockwise signal is delayed by 3λ / 4, and the counterclockwise signal is delayed by 3λ / 4. As a result, a high frequency signal delayed by 3λ / 4 is output from the port P4 due to the high frequency signal input to the port P2.

  Therefore, at port P4, the high frequency signal delayed by λ / 4 generated at the input to port P1 and the high frequency signal delayed by 3λ / 4 generated at the input to port P2 are combined.

  The rat race circuit 31 that operates as described above has two characteristics. First, the first characteristic will be described. This characteristic is that when a high-frequency signal having the same phase is input to the ports P1 and P2 of the rat race circuit 31, a high-frequency signal synthesized from the port P3 is output and a high-frequency signal is not output from the port P4. That is, at the port P3, the high frequency signal delayed by λ / 4 generated by the input to the port P1 and the high frequency signal delayed by λ / 4 generated by the input to the port P2 are added. As a result, a high-frequency signal added and synthesized is output from the port P3. These characteristics are referred to as in-phase output characteristics.

  Further, at the port P4, the high frequency signal delayed by λ / 4 generated by the input to the port P1 and the high frequency signal delayed by 3λ / 4 generated by the input to the port P2 are combined. As a result, the two high-frequency signals cancel each other. That is, the high-frequency signal is not output from the port P4 with the common-mode output characteristics.

  Next, the second characteristic of the rat race circuit 31 will be described. This characteristic is that when high-frequency signals having opposite phases are input to the ports P1 and P2 of the rat race circuit 31, a high-frequency signal synthesized from the port P4 is output and no high-frequency signal is output from the port P3. . That is, at the port P4, the high frequency signal delayed by λ / 4 generated by the input to the port P1 and the high frequency signal delayed by 3λ / 4 generated by the input to the port P2 are combined. At this time, since the phase of the high frequency signal applied to the port P1 is 180 degrees different from that of the high frequency signal applied to the port P2, the phase is different by λ / 2. As a result, the high-frequency signal delayed by λ / 4 generated by the input to the port P1 from the port P4 and the high-frequency signal applied to the port P1 are delayed by 3λ / 4 and only by λ / 2. High-frequency signals with different phases are added together. As a result, the added high frequency signal is output from the port P4. These characteristics are referred to as reverse phase output characteristics.

  Further, at port P3, the high frequency signal delayed by λ / 4 generated by the input to port P1 and the high frequency signal delayed by λ / 4 generated by the input to port P2 are combined. As a result, the high-frequency signal delayed by λ / 4 generated from the input to the port P1 from the port P3 and the high-frequency signal applied to the port P1 are delayed by λ / 4 and only by λ / 2. High-frequency signals having different phases are synthesized. As a result, the high-frequency signals having opposite phases cancel each other out at the port P3. That is, in the reverse phase output characteristic, a high frequency signal is not output from the port P3.

The selection switch circuit 33 of the receiving unit 30 connects any of the ports P1 to P4 of the rat race circuit 31 to the receiver 34 of the next stage via the connecting unit 32. The selection switch circuit 33 includes a contact 33A that is movable under the control of the control unit 35 and contacts 33B _{1 to} 33B ₄ that are fixed and open. The contact 33A is connected to the receiver 34, and the contacts 33B _{1 to} 33B ₄ are connected to the ports P1 to P4 of the rat race circuit 31 via the connection part 32, respectively. That is, the selection switch circuit 33 receives the control of the control unit 35 and connects the receiver 34 to _one of the contacts 33B ₁ to 33B ₄ in order. At this time, contacts that are not connected to the contact 33A, that is, contacts that are not connected to the receiver 34 are opened.

Such a selection switch circuit 33 is configured by, for example, a rotary switch having four contacts (contacts 33B _{1 to} 33B ₄ ). The ports P1 to P4 of the rat race circuit 31 are connected to the four contacts of the rotary switch, and the rotary shaft of the rotary switch is driven to rotate by a pulse motor. The pulse motor is a motor that rotates by a predetermined angle under the control of the control unit 35 and stops at each of the four contacts. In addition, there are various types of selection switch circuit 33 such as a circuit combining a relay.

The connection unit 32 of the reception unit 30 is provided between the rat race circuit 31 and the selection switch circuit 33. The connection part 32 is formed by connection cables 32A to 32D. The connection cables 32A and 32B have an electrical length of λ / 2, and connect the ports P1 and P2 of the rat race circuit 31 to the contacts 33B ₁ and 33B ₂ of the selection switch circuit 33, respectively. The connection cables 32C and 32D have an electrical length of λ / 4, and connect the ports P3 and P4 of the rat race circuit 31 to the contacts 33B ₃ and 33B ₄ of the selection switch circuit 33, respectively.

  The coaxial transmission line used for such a selection switch circuit 33 has the following characteristics. When the electrical length of the cable of the coaxial transmission line is λ / 4, when one end is opened, the impedance when the coaxial transmission line is viewed from the other end becomes zero. On the contrary, when one end is short-circuited, the impedance when the coaxial transmission line is viewed from the other end becomes infinite. The same applies to the transmission lines 31A to 31D having the coaxial structure of the rat race circuit 31.

Since the transmission path of the coaxial structure electrical length is lambda / 4 of the cable has such characteristics, when the contacts 33B ₁ of the selection switch circuit 33 is opened, the electrical length of lambda / 2 cables For the connection cable 32A having a large thickness, the impedance viewed from the port P1 becomes infinite. Connection cable 32B is also similar, when the contacts 33B ₂ of the selection switch circuit 33 is opened, the connection cable 32B, impedance viewed from the port P2 is infinite. The electrical lengths of the connection cables 32A and 32B are not limited to λ / 2, and may be any length as long as the impedance viewed from the ports P1 and P2 is infinite.

Meanwhile, when the contacts 33B ₃ of the selection switch circuit 33 is opened, the connection cable 32C with the electrical length of lambda / 4 cable impedance seen from the port P3 is zero. Connection cable 32D is similar, when the contacts 33B ₄ of the selection switch circuit 33 is opened, the connection cable 32D, the impedance viewed from the port P4 is zero. Note that the electrical length of the connection cables 32C and 32D is not limited to λ / 4, and may be any length as long as the impedance viewed from the ports P3 and P4 is zero.

  When the receiver 34 receives a high frequency signal from the contact 33A of the selection switch circuit 33, the receiver 34 reproduces measurement data representing a water level, a flow rate, and the like from the high frequency signal. Then, the receiver 34 sends the reproduced measurement data to the control unit 35.

The control unit 35 stores in advance the data transmission time of the hydroelectric power plant. When the data transmission time comes, the control unit 35 controls the selection switch circuit 33 in accordance with the timing at which the four measurement data are sequentially transmitted, and sequentially connects the contact 33A to one of the contacts 33B _{1 to} 33B _4. Perform the connection operation. Thereafter, when receiving measurement data from the receiver 34, the control unit 35 performs a parity check on this data and detects an error in the measurement data. And the control part 35 outputs the measurement data without an error to the apparatus of the next stage.

  Next, the operation of the radio communication system according to this embodiment will be described. The robot telemeter 1 of the hydroelectric power station sends measurement data such as the water level and flow rate of the river to the transmitter 2. The transmission device 2 sequentially transmits a set of measurement data, that is, four measurement data at regular intervals at the time of measurement data transmission.

In the wireless receiver 3 at the power station, the control unit 35 of the receiving unit 30 controls the selection switch circuit 33 to connect the contact 33A to the contacts 33B _{1 to} 33B ₄ in accordance with the timing at which the four measurement data are transmitted. To go. In this embodiment, the selection switch circuit 33 connects the contact 33A in the order of the contact 33B ₁ , the contact 33B ₂ , the contact 33B ₃ , and the contact 33B ₄ under the control of the control unit 35.

When the selection switch circuit 33 connects the contact 33A to the contact 33B _1, the high-frequency signal from the first antenna 10, the connection cable 32A, contact 33B _1, through the contacts 33A, it is input to the receiver 34.

Further, when the selection switch circuit 33 connects the contact 33A to the contact 33B _1, as shown in FIG. 6, the contact _33B 2 _{~33B 4} is opened. When the contact 33B ₂ is opened, the characteristics of the transmission path of the electrical length of lambda / 2 of the coaxial structure of the cable, as viewed from the port P2, the electrical length of the cable is a lambda / 2 connection cable 32B The impedance of becomes infinite. In FIG. 6, the direction in which the impedance is viewed is indicated by a thick arrow, and the impedance is indicated by Imp. Since the impedance of the connection cable 32B viewed from the port P2 is infinite, that is, open, the impedance of the transmission line 31C having a coaxial structure with a cable electrical length of λ / 4 viewed from the port P3 becomes zero. Since the impedance of the transmission line 31C having the coaxial structure viewed from the port P3 is zero, that is, a short circuit, the impedance of the transmission line 31A having the coaxial structure of λ / 4 as viewed from the port P1 is infinite. become.

In the same manner, the contacts 33B ₂ is opened, the impedance of the connecting cable 32B as viewed from the port P2 is infinite, as viewed from the port P4, the electrical length of the cable 3 [lambda] / 4 of the coaxial structure The impedance of the transmission line 31D becomes zero. Since the impedance of the transmission line 31D having the coaxial structure viewed from the port P4 is zero, that is, a short circuit, the impedance of the transmission line 31A having the coaxial structure of λ / 4 as viewed from the port P1 is infinite. become.

Thus, since the impedance viewed from the port P1 is infinity, i.e. it opened, in a state in which the path from the contact point 33B ₂ of the selection switch circuit 33 to the port P1 is not connected. In the same way, ready unconnected path from contact point 33B ₃ of the selection switch circuit 33 to the port P1, a state that is not connected to the path from the contact 33B ₄ of the selection switch circuit 33 to the port P1 . That is, only the first antenna 10 and the connection cable 32A are connected to the port P1. Therefore, only the high frequency signal from the first antenna 10 is input to the receiver 34. This state is for receiving a radio wave at a reception point having a high electric field strength in a portion having a high height pattern.

When the selection switch circuit 33 connects the contact 33A to the contact 33B _2, as if it were connected to contact 33A to the contact 33B _1, is not connected path from contact point 33B ₁ of the selection switch circuit 33 to the port P2 state become. Further, since the state in which the path from the contact point 33B ₃ of the selection switch circuit 33 to the port P2 is not connected, the state of the path leading to the port P2 from the contact 33B ₄ is not connected to the selection switch circuit 33. That is, only the second antenna 20 and the connection cable 32B are connected to the port P2. Therefore, only the high frequency signal from the second antenna 20 is input to the receiver 34. This state is for receiving a radio wave at a receiving point having a strong electric field strength in a portion having a low height pattern.

When the selection switch circuit 33 connects the contact 33A to the contact 33B _3, short-circuit all the contacts 33B _1, contact 33B _2, the path from the contact 33B ₄ to port P3, that is, becomes the connected state. In this state, the common mode output characteristic of the rat race circuit 31, when the high-frequency signal and the high frequency signal from the second antenna 20 from the first antenna 10 are in phase with respect to the contact 33B ₃ of the selection switch circuits 33 Thus, the port P3 of the rat race circuit 31 sends a high frequency signal. The selection switch circuit 33 outputs this high frequency signal to the receiver 34. That is, the selection switch circuit 33 Connecting contacts 33A to the contact 33B _3, and outputs the combined signal to a high frequency signal by the low-angle radio waves coming to the receiver 34. This state is for receiving low-angle incoming radio waves.

When the selection switch circuit 33 connects the contact 33A to the contact 33B _4, short-circuit all the path from contact point _33B 1 _{~33B 3} to the port P4, that is, becomes the connected state. In this state, the contact 33B ₄ of the selection switch circuit 33 when the high-frequency signal from the first antenna 10 and the high-frequency signal from the second antenna 20 are in reverse phase due to the reverse-phase output characteristics of the rat race circuit 31. On the other hand, the port P4 of the rat race circuit 31 sends a high frequency signal. The selection switch circuit 33 outputs this high frequency signal to the receiver 34. That is, the selection switch circuits 33 Connecting contacts 33A to the contact 33B _4, and outputs the combined signal a high frequency signal by the high-angle radio waves coming to the receiver 34. This state is for receiving incoming radio waves at a high angle.

  As described above, when the first antenna 10 and the second antenna 20 receive the radio waves having a set of four measurement data, the selection switch circuit 33 sequentially sends four high-frequency signals to the receiver 34. The receiver 34 reproduces measurement data from the four high-frequency signals and sends these measurement data to the control unit 35. When receiving measurement data from the receiver 34, the control unit 35 performs a parity check on each data and detects an error in the measurement data. Then, the control unit 35 outputs the measurement data with the least error to a subsequent apparatus such as a recording apparatus.

Thus, according to this embodiment,
a. Receive radio waves at a strong receiving point in the high part of the height pattern b. Receive radio waves at strong reception points in the low part of the height pattern c. Receive low-angle incoming radio waves d. It is possible to obtain measurement data with no error by performing reception using four types of reception methods of receiving a high-angle incoming radio wave, and selecting measurement data based on an optimum high-frequency signal from among these. This makes it possible to prevent measurement data from being lost. Further, when receiving a height pattern radio wave or responding to a change in the arrival direction of the radio wave, it is possible to eliminate the need to move or adjust the antenna.

(Embodiment 2)
In the first embodiment, the lengths of the connection cable 32A and the connection cable 32B are λ / 2. However, in this embodiment, the lengths of the connection cable 32A and the connection cable 32B are set to zero. That is, it connected directly to the port P1 of the rat race circuit 31 to a contact 33B ₁ of the selection switch circuit 33, connected directly to the port P2 to the contact point 33B ₂ of the selection switch circuit 33.

  According to this embodiment, the connection cable 32A and the connection cable 32B can be omitted, and the configuration of the connection portion 32 can be simplified.

(Embodiment 3)
In the first embodiment, the case where a wireless communication system using a fixed line using a radio wave in the 70 MHz band performs communication is described as an example. However, in this embodiment, wireless communication is performed at a higher frequency than this frequency band. The system communicates. In this case, the rat race circuit 31 and the connection portion 32 are formed on the substrate instead of the coaxial transmission line used in the rat race circuit 31 and the connection portion 32 of the wireless reception device 3. That is, since the wavelength λ is further shortened, the rat race circuit 31 and the connection portion 32 are formed by forming a pattern having a length of λ / 4 and 3λ / 4 on the substrate as a transmission path.

  Thereby, in order to install the rat race circuit 31 and the connection portion 32 for the wireless receiver 3 that performs communication at a frequency higher than the 70 MHz band, the substrate (strip line type) on which the rat race circuit 31 and the connection portion 32 are formed. Therefore, it is not necessary to change the radio receiving device 3 significantly, and the radio receiving device 3 can be created at a lower cost.

(Embodiment 4)
In each of the embodiments described above, the receiver 34 is connected to one of the contacts 33B _{1 to} 33B ₄ of the selection switch circuit 33 in order. At this time, contacts that are not connected to the contact 33A, that is, contacts that are not connected to the receiver 34 are open. In contrast, in this embodiment, the contacts not connected to the receiver 34 are short-circuited, that is, grounded.

  In general, the coaxial transmission lines 31A to 31D of the rat race circuit 31 and the coaxial transmission lines used as the connection cables 32A to 32D of the connection portion 32 are used with their shields grounded. Therefore, when a contact that is not connected to the receiver 34 is grounded, the contact is short-circuited.

Selection switch circuit 33 to such connection, for example, as shown in FIG. 7, are formed by using a rotary switch 33 ₁₀ with four circuit 4 contacts. That is, the circuits 33 _{11 to} 33 ₁₄ of the rotary switch 33 ₁₀ are used to connect or ground the ports P1 to P4 of the rat race circuit 31 to the receiver 34, respectively.

In this case, the lengths of the connection cables 32 </ b> A to 32 </ b> D of the connection unit 32 are reversed from those in the first embodiment. That is, the connection cables 32A and 32B have an electrical length of λ / 4, and the connection cables 32C and 32D have an electrical length of λ / 2. By doing so, for example, when the contacts 33B ₁ of the selection switch circuit 33 are short-circuited, lambda / the fourth connection cable 32A having an electrical length of the cable, the impedance viewed from the port P1 is infinite Become. The same applies to the connection cable 32B.

  According to this embodiment, since the contacts not connected to the receiver 34 are short-circuited, it is possible to reduce the possibility of external noise and the like and the influence of measurement data.

(Embodiment 5)
In each of the embodiments described above, the present invention is applied to the wireless reception device 3. However, it is of course possible to use the receiving unit 30 according to each embodiment on the transmission side. In this case, a transmitter is used instead of the receiver 34, and when the control unit 35 receives the measurement data, the control unit 35 sends the data to the transmitter and controls the selection / selection switch circuit 33, and contacts 33B _{1 to} 33B _4. One of the contacts 33A is sequentially connected. On the reception side, reception is performed at the transmission timing on the transmission side.

  This embodiment uses the same principle as each of the above-described embodiments, and transmits a signal corresponding to the height pattern on the transmission side, so that the signal can be reliably received by the receiving device. To do.

  As mentioned above, although each embodiment of this invention has been described in detail, the specific configuration is not limited to each embodiment, and even if there is a design change or the like without departing from the gist of this invention, It is included in this invention. For example, although the case where the wireless communication system according to each embodiment is used in an electric power company is taken as an example, the present invention can be used in various fields that use wireless communication using radio waves in a megahertz band or a gigahertz band.

1 is a configuration diagram showing a wireless communication system according to Embodiment 1. FIG. 1 is a configuration diagram illustrating a wireless reception device according to Embodiment 1. FIG. FIG. 3A is a diagram illustrating a directivity characteristic of a receiving antenna, FIG. 3A is a diagram illustrating a composite directivity characteristic based on an in-phase component signal, and FIG. 3B is a diagram illustrating a composite directivity characteristic based on an anti-phase component signal. It is a block diagram which shows the structure of a receiving part. It is a figure explaining a rat race circuit. It is a figure which shows the relationship of an impedance. FIG. 10 is a circuit diagram showing a connection part in a fourth embodiment. It is a figure explaining a height pattern. It is a figure explaining the drive of an antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Robot telemeter 2 Transmitter 3 Radio | wireless receiver 10 1st antenna 20 2nd antenna 30 Receiving part 31 Rat race circuit 32 Connection part 33 Selection switch circuit (switch circuit)
34 Receiver 35 Control unit

Claims (8)

An antenna that is arranged apart from each other in the vertical direction, receives radio waves, and outputs a high-frequency signal;
The first and second ports are connected to the antenna, respectively, and the third and fourth ports output the synthesized high frequency signal, the first and third ports, the first and fourth ports, and Between the second and third ports, a transmission line having an electrical length of a quarter wavelength of the radio wave is connected, and between the second and fourth ports, three-quarters of the radio wave is connected. A rat race circuit to which a transmission line of an electrical length of wavelength is connected;
First to fourth contacts are connected to the first to fourth ports of the rat race circuit, respectively, and a switch circuit that selects one of the contacts and connects to the next stage;
The first and second ports are electrically connected to the first and second ports, and the first and second ports are connected to the first and second ports. The third and fourth ports are connected by an electrical length transmission line in which the impedance when the third and fourth contacts are viewed from the third and fourth ports, respectively, is zero.
A wireless receiver characterized by that. The first to fourth contacts of the switch circuit are opened,
The first and second ports of the rat race circuit and the first and second contacts of the switch circuit are a half-wavelength electrical length transmission line or an integral multiple of the half-wavelength length. The third and fourth ports of the rat race circuit and the third and fourth contacts of the switch circuit are each of a quarter wavelength electrical length. Each is connected by a transmission line or a transmission line having an electrical length that is an odd multiple of the length of a quarter wavelength.
The wireless receiver according to claim 1, wherein The first to fourth contacts of the switch circuit are short-circuited,
The first and second ports of the rat race circuit and the first and second contacts of the switch circuit are connected to each other by a quarter-wave electrical length transmission line, respectively. The fourth port and the third and fourth contacts of the switch circuit are respectively connected by a transmission line having an electrical length of a half wavelength.
The wireless receiver according to claim 1 or 2, wherein The two antennas are arranged at a distance that is an odd multiple of the half wavelength of the radio wave to be received.
The wireless reception device according to claim 1, wherein the wireless reception device is a wireless communication device. Each transmission path of the rat race circuit and each transmission path connecting the rat race circuit and the switch circuit are formed of a coaxial transmission line.
The wireless reception device according to claim 1, wherein the wireless reception device is a wireless communication device. A wireless communication system using the wireless reception device according to any one of claims 1 to 5,
A transmitter that sequentially transmits a plurality of the same signals when transmitting a signal;
A control unit that performs control to sequentially select one of the contacts and connect to the next-stage receiver with respect to the switch circuit of the wireless reception device at a timing at which the transmission device transmits a signal;
A wireless communication system comprising: When the control unit receives the signal reproduced from the high-frequency signal by the receiver from the receiver, the control unit detects an error of each signal and outputs a signal having no error.
The wireless communication system according to claim 6. A wireless communication system comprising the wireless reception device according to any one of claims 1 to 5 as a wireless transmission device on a transmission side,
Provided on the transmission side, a control unit that performs control to sequentially select one of each contact and connect to the transmitter in the previous stage for the switch circuit at the timing of transmitting a signal;
When receiving a signal, at the timing of transmitting the signal on the transmission side, a receiving device that sequentially receives the signal;
A wireless communication system comprising:

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