JP2650234B2 - Indoor communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an indoor communication system. For example, the present invention is applied to short-range communication, a cordless office (cordless personal computer, cordless printer, cordless plotter), and the like.

[0002]

2. Description of the Related Art Conventionally, a communication system using a reflector has been known. Normally, a flat plate or a concave plate is used for communication in a specific direction, and few use an omnidirectional reflector. Although many examples of the transmission / reception shared antenna are known, there is no example in which transmission (for example, right) and reception (for example, left) are used by circularly polarized reverse rotation. In satellite communication,
Up-link right-handed, down link left-handed-turn, etc., the polarization is determined by the direction.

In recent years, many personal computers (PCs) have been used in offices, and communication between the PCs has also been actively performed. Further, printers and plotters, which are peripheral devices thereof, have come to be widely used. These devices are usually connected by cables, and once installed, changing the layout of the room requires complicated wiring processing between the devices, making it extremely difficult. Requires a free access floor. On the other hand, peripheral devices such as printers and plotters are significantly less in number of operating times than PCs. Therefore, by sharing one printer or plotter with several PCs, it is possible to reduce equipment costs and floor space. In view of the above, a cordless indoor communication system that does not require wiring between a PC and peripheral devices and between PCs is desired.

[0004] When this cordless operation is pursued, it is necessary to connect each device wirelessly. However, considering the contents to be transmitted, it is assumed that a plurality of channels with a transmission speed of 4800 bps or more are secured, and the frequency band that can be used for a carrier wave is as follows. Several hundred MH
Requires z or higher. The frequency band used for normal indoor communication is 250/380 MHz for cordless telephones.
z, 800MHz band for mobile phone for mobile communication. In communication using these frequency bands, the two stations are generally connected using an omnidirectional antenna. For such communications,
If there is no obstacle in the space between the two poles, stable communication can be ensured. However, when assuming indoors, there are various fixtures, books, and other obstacles between PCs and printers on the desk, and people move between them. For this reason, in addition to the space loss between the two, the effects of these obstacles are added,
Electric field intensity changes and is not stable. For this reason, it is necessary to take measures to cope with this in the transmission system.

On the other hand, considering the use of a short wavelength band of 10 GHz or more, as in the case of the relatively long wavelength described above,
Radio waves cannot be expected to wrap around the shadow area of the obstacle, and must be in line of sight between transmission and reception. But,
In this band, it is easy to provide the antenna with unidirectionality, and it is relatively easy to gain. In addition, as a result, pointing can be easily performed, and by using the ceiling of the room as a reflecting surface, line-of-sight communication can be secured while avoiding the above-described obstacle. Further, since the short wavelength band is used, the transmission capacity can be increased.

[0006]

[Purpose] The present invention has been made in view of the above-described circumstances, and has a special transmission / reception isolation.
To be possible without preparing a receiving separation circuit, to reduce the number of antennas, to enable communication in the office, and to efficiently transmit and receive signals,
Provide an indoor communication system that is easy to point and prevents communication deterioration due to vibrations and changes in the attitude of the antenna, and enables one aperture antenna or one array antenna to be used for both transmission and reception as a transmission / reception antenna. It was done for the purpose of doing.

[0007]

To achieve the above object, the present invention provides (1)
Transmitting means for radiating right-handed or left-handed circularly polarized light; a hemispherical or quarter-spherical radio wave reflector for transmitting radio waves radiated from the transmission means to a receiving means; Receiving means for receiving the transmitted radio wave,
Reception is separated and independent by circularly polarized reverse rotation, further (2) the transmitting means and the receiving means are performed by the same antenna, and (3) single-station to single-station bidirectional communication. Or, performing a plurality of sets of bidirectional communication between single stations, or performing single-station pair-to-multi-way and multi-pair-to-multiple-way bidirectional communication, and (4) in (3), the transmission / reception antenna The beam width Θ (radian), the radius a (m) of the spherical radio wave reflector, and the distance R between the antenna and the radio wave reflector
(m) satisfies the relationship of 4 · a> R · Θ> a. (5) In (1), an aperture formed by a combination of a parabolic reflector and a primary horn antenna as the transmitting / receiving antenna. A 1/4 wavelength phase shift plate is provided in the waveguide of the primary radiator using a surface antenna. (6) In (1), an array antenna is used as the transmission / reception antenna, and a hybrid circuit is formed. It is characterized by having been provided. Hereinafter, a description will be given based on examples of the present invention.

FIG. 1 is a block diagram for explaining an embodiment of an indoor communication system according to the present invention. In FIG. 1, 1 is a transmitting personal computer (PC), 2 is a transmitting transceiver, and 3 is a transmitting antenna. Reference numerals 4 and 5 indicate reflectors, 6 indicates a receiving antenna, 7 indicates a receiving transceiver, and 8 indicates a receiving personal computer. The present invention shows a method of performing bidirectional communication using a frequency band equal to or higher than the X-band. FIG. 1 shows a basic conceptual diagram of the present invention, in which an aperture antenna or an array antenna 1 radiates right-handed or left-handed circularly polarized waves, and the beam width is determined by the distance R ( m). Now, assuming that the diameter of the reflector is 2a (m), the beam width Θ (radian) is 4 · a> R
It is desirable to satisfy Θ> a, and in particular, to set the beam width に to about Θ = 2a / R or more. This is to irradiate the reflector with most of the energy radiated from the antenna and not to radiate unnecessary radio waves to a space other than the reflector, so that the energy can efficiently reach the reception point 6. . However, if the beam is too sharp, pointing becomes difficult, and a slight vibration or a change in the attitude of the antenna causes an offset of the beam, which leads to communication degradation.

The reflector on the hemisphere installed on the ceiling is made of a good conductor. As is well known, since the scattering of the electromagnetic wave by the perfect conducting sphere extends over a wide angle, the transmission wave is scattered over the entire indoor area shown in FIG. 1, and the electromagnetic wave reaches every corner of the room. Here, the circularly polarized wave reflected by the spherical reflector is inverted from the incident circularly polarized wave. For example, if the transmission is right-handed circularly polarized, the received radio wave is left-handed circularly polarized. Reach the receiving point. The receiving point 6 receives this left-handed circularly polarized wave. When transmitting information to the above-mentioned transmission point 3 at the reception point 6, the antenna 6 transmits the same right-hand circularly polarized wave emitted from the antenna 3 for transmission.
The antenna 3 separates transmission and reception by preparing two feeding points of left and right circularly polarized waves, and can use the same frequency in principle.

[0010] Whether the antenna is an aperture antenna or an array antenna, the excitation circuit of the antenna has a 90 ° orthogonal bi-polarization.
With the phase shift synthesizing method, it is possible to easily separate and extract the reverse rotation output. However, in general, the isolation between the counter-polarized waves obtained by the antenna excitation circuit is 30.
Since it is about dB and the circularly polarized wave scattered by the spherical reflector becomes an elliptically polarized wave, it is desirable to set the transmission and reception frequencies by taking a separation appropriate for the transmission band. This makes it easier to ensure isolation between the transmitter and the receiver.

That is, the feature of the present method is that a hemispherical reflector is provided on the indoor ceiling, and the indoor information transmission is performed cordlessly by using the transmission and reception reverse circular polarization. Is that transmission / reception isolation is enabled without preparing a special transmission / reception separation circuit (diplexer). Further, the reflector installed on the ceiling can be replaced by a quarter sphere 4 as shown in FIG. 1, depending on the arrangement between the devices. In addition to this method, even if the indoor layout is changed, new communication is possible only by turning the antennas 3 and 6 toward the reflector 4. By introducing the reflectors 4 or 5 used here, single-to-multi-station, multi-station to multi-station bidirectional communication becomes possible. An example will be described below. Assuming that the room area is 10 × 10 m ² , a use frequency of 10 GHz, a hemispherical reflector having a diameter of 30 cm is installed on the center ceiling of the room, an antenna beam width of 10 °, a gain Gt, Gr of about 24 dB, and a transmission power P
t · 1mW. The received power at this time is calculated using the radar equation,

[0012]

(Equation 1)

Assuming that R = 6 m, Pr = −100 dBm. On the other hand, the receiver noise is obtained by N = kTBBk: Boltzmann constant, T: absolute temperature, B: receiver bandwidth, F: noise figure, and the bandwidth is 9.6 kHz, F = 5 dB. Then, N = -129 dBm and C / N = 29 dB, and sufficient communication can be secured. If Θ = 10 °, R = 6m
Since RΘ ≒ 1.05 m, the size of the reflector can be further increased, and up to 2a = 60 cm if there is no problem in installation and aesthetics. Conversely, if the antenna beam is halved, the gain is improved and the C / N is also improved. By the way, G = 2 at f = 10GHz
To obtain 4 dB, the antenna aperture is approximately 6λ × 6λ.
And it will be about 18cm x 18cm. Suppose that the transmitting and receiving antennas are twice as large as 10λ × 10λ
Then, the beam width becomes Θ ≒ 6 ° and G ≒ 29dB,
C / N will increase by 10 dB. At this time, the antenna is about 30 cm × 30 cm.

An example of a circularly polarized transmitting / receiving antenna will be described. As described above, an antenna for transmitting and receiving using left and right circularly polarized waves used for indoor communication can be an aperture antenna or an array antenna. There are various construction methods of the circularly polarized antenna, and one example is shown in FIGS.
FIGS. 2A to 2C are diagrams showing examples of an aperture antenna, and show a combination of a parabolic reflector and a primary horn antenna. Figure (a) is an overall configuration diagram, and Figure (b) is a diagram (a)
FIG. 3C is a front view of the primary antenna, in which 11 is the primary antenna, 12 is a parabolic reflector, and 13 is a λ / 4 phase shift plate. The λ / 4 phase shift plate 13 provided in the circular waveguide of the primary radiator converts an electric field component parallel to this plate into an electric field component orthogonal to this plate by π / 2 while passing through the phase shift plate. This causes a phase difference. Therefore, two orthogonal probe outputs provided behind the probe can be used for left and right circularly polarized waves, and can be used for both transmission and reception and reverse polarization.

FIG. 3 shows an array antenna (two-element array).
In the figure, 21a and 21b are first dipoles, 22a and 22b are second dipoles, 23 is a terminator, 24 is a hybrid circuit, and 25 is a phase shifter.
The orthogonal polarization of each element is excited with a π / 2 phase difference. At this time, if a hybrid circuit is used to generate quadrature inputs different by π / 2, a sum-difference signal can be extracted from the input terminal. Since this results in left- and right-handed circularly polarized waves, this circuit can be combined to form an array.

[0016]

As apparent from the above description, the present invention has the following effects. (1) Through a hemispherical or quarter spherical radio wave reflector,
An object of the present invention is to make transmission and reception separate and independent by circularly polarized reversal, thereby enabling transmission and reception isolation without preparing a special transmission and reception separation circuit. (2) Claim 2 is based on the method of claim 1 so that transmission and reception are performed by the same antenna, and the number of antennas requiring space is generally reduced. (3) Claim 3 proposes a preferred antenna method in an office by using an aperture antenna or an array antenna as the transmitting / receiving antenna in the method of claim 1. (4) Claim 4 is the communication method according to claim 3, wherein the beam width of the transmitting / receiving antenna Θ (radian);
The radius a (m) of the spherical radio wave reflector described above and the distance R (m) between the antenna and the radio wave reflector described above satisfy the following relationship, so that signal transmission / reception is performed. It is intended to efficiently and easily point and prevent communication deterioration due to vibrations and changes in the attitude of the antenna. 4 · a> R · Θ> a (5) Claim 5 uses an aperture antenna formed by a combination of a parabolic reflector and a primary horn antenna as a transmitting / receiving antenna in the communication method according to claim 1.
By providing a 1/4 wave phase shift plate in the waveguide of the primary radiator, one aperture antenna can be used for both transmission and reception. (6) According to claim 6, when an array antenna is used as a transmitting / receiving antenna in the communication method according to claim 1,
By using a hybrid circuit, one array antenna can be used for both transmission and reception.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an indoor communication system according to the present invention.

FIG. 2 is a diagram illustrating an example of an aperture antenna.

FIG. 3 is a diagram illustrating an example of an array antenna.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmission personal computer (PC), 2 ... Transmission side transceiver, 3 ... Transmission side antenna, 4,5 ... Reflector, 6 ... Receiving side antenna, 7 ... Receiving side transceiver, 8
... Receiver personal computer.

Claims (6)

(57) [Claims] A transmitting means for radiating a right-handed or left-handed circularly polarized wave; a hemispherical or quarter-spherical radio wave reflector for transmitting a radio wave radiated from the transmitting means to a receiving means; An indoor communication system, comprising: receiving means for receiving a radio wave reflected by a reflector, wherein the transmission and the reception are separated and independent from each other by circularly polarized reverse rotation. 2. The indoor communication system according to claim 1, wherein said transmitting means and said receiving means are performed by the same antenna. 3. A single station-to-single station two-way communication, a plurality of sets of two-way communication between single stations, or a single station-to-multi-way communication and a plurality of two-way-to-multi-way communication. 2. The indoor communication system according to 1. 4. The beam width of the transmitting / receiving antenna Θ
(Radian), the radius a (m) of the spherical radio wave reflector, and the distance R (m) between the antenna and the radio wave reflector are 4 ·
4. The indoor communication system according to claim 3, wherein a relationship of a> R · Θ> a is satisfied. 5. The transmission / reception antenna according to claim 1, wherein an aperture antenna formed by a combination of a parabolic reflector and a primary horn antenna is used, and a quarter-wave phase shift plate is provided in a waveguide of the primary radiator. Item 2. The indoor communication method according to Item 1. 6. The indoor communication system according to claim 1, wherein an array antenna is used as said transmitting / receiving antenna and a hybrid circuit is provided.