Electromagnetically shielded building with system for detecting leakage of radio waves thereinto

Abstract: In a building (1) constructed so that its structure and apertures form an electromagnetic screening to prevent leakage of radio communications from within the building, any defect in the screening is detected by a system consisting of a plurality of sensors (4) distributed around each floor of the building to detect waves from every direction, linked to a unit (3) for checking the level of the radiation received from each sensor and comparing it with a normal value. In the case when an abnormally high value at one sensor is detected, the output of a master radio unit (2) on that floor, used for communication within the building, is reduced (see Fig. 4) to reduce the leakage of radio waves to the outside, and an alarm is activated by a visual display (6) and/or printer (7), see Fig. 3, so that the defect can be rectified promptly.

Description: The present invention relates to a building in which is installed a system for detecting and processing an abnormality in electromagnetic shielding of the building in which radio communication is carried out and which is constructed using an electromagnetic shielding material for its structure and apertures such as windows and doorways, so that the whole of the building is formed into an electromagnetic shielding structure. It is general practice in such buildings (which may be referred to as "intelligent" buildings) to utilize jointly information communicating equipment such as a composite electronic switching system and a computer for information communication with an other party inside or outside the building. As a result of an increase in value placed on information and the more diverse as well as individual nature of information, there has been a rapid increase in the amount of information handled. Under these circumstances, it is a problem to provide required information within such buildings quickly at low cost. To solve this problem, use may be made of an information network based on a data highway system that utilizes optical fiber cables, coaxial cables or the like. However, such a data highway system requires that optical fiber cables or coaxial cables are laid throughout the building so that the cables extend to every equipment terminal, and therefore it necessitates a floor duct and a double-floored structure for laying such cables, resulting in a considerable increase in both the cost and duration of construction. If radio waves are used for information communication, no cables are needed. In such a case, however, since the radio waves may have effects outside the building, the use of radio waves is subject to regulation by radio communications law; on the other hand, external radio waves may cause a malfunction of the system. Accordingly, the present applicant has already made various proposals (e.g. EPA 87304616 published 23.11.88 and 87305177, published 11.01.89 concerning a building which is constructed using an electromagnetic shielding material for its structure and apertures such as windows and doorways so that the whole of the building is formed into an electromagnetic shielding structure, thereby enabling free radio communication inside the building without suffering from legal regulation. However, even if the whole of the building is constructed as an electromagnetically shielded structure to enable radio communication inside the building, once the electromagnetic shielding is broken at any part of the building, strong radio waves are continuously released to the outside, causing a problem in terms of radio law. Further, in such a case, the radio communication inside the building is readily affected by external radio waves, resulting in a paralysis of the information transmitting function. Accordingly, it is considerably important in order to avoid such problems to find any defect or deterioration of the electromagnetic shielding in its early stage. However, it is not easy to predict the position there the electromagnetic shielding of an intelligent building will probably be broken. In particular, when the size of the building itself increases, the range of inspection enlarges correspondingly. For this reason, it is considered difficult to make a diagnosis as to whether or not electromagnetic shielding performance is satisfactory, and there has heretofore been no system which is capable of finding a defect or deterioration (abnormality) of electromagnetic shielding of such buildings. It is a primary object of the present invention to provide a building in which is installed a system for detecting and processing an abnormality in electromagnetic shielding which is capable of readily finding deterioration of the electromagnetic shielding performance of an intelligent building and a defect in an electromagnetic shielding structure. EP-A-0248501 discloses a detection system as set out in the pre-characterising portion of the present Claim 1, but only for detecting leakage of radio waves into a room of a building; we now provide means for detecting the floor of a building where an abnormality occurs. The present invention provides a building in which is installed a system for detecting leakage of radio waves into the building which is constructed of electromagnetically shielding material for its external structure and the openings therein, so as to detect defects in said shielding, which system comprises: radio wave detecting means inside said building for detecting the presence of externally generated radio wave signals; level judging means for judging the level of said detected external radio waves; and processing means for detecting and processing an abnormality on the basis of the output from said level judging means, whereby an abnormality in the electromagnetic shielding performance is detectable on the basis of the intensity level of a detected radio wave intruding into said building from the outside; characterized in that the radio wave detecting means is disposed on each floor of the building and in every direction, and said level judging means is arranged to judge the electromagnetic shielding performance to be abnormal on the basis of the fact that the level of a detected external radio wave exceeds a normal value, and thereby to identify the floor of the building where the abnormality is present. We also provide a method of detecting leakage of radio waves into a shielded building, which comprises using the aforesaid system and noting any abnormality of the output of the level judging means, thereby to identify the floor of the building where there is a defect in the shielding. When the electromagnetic shielding performance has deteriorated, external radio waves such as broadcast waves or telecast waves, intrude into the building. Therefore, all of these radio waves are constantly monitored by the radio wave detecting means inside the building. Thus, when the electromagnetic shielding performance has considerably deteriorated, the abnormality can be detected by judging the level of the detected radio wave with the level judging means. Accordingly, it is possible to conduct an appropriate processing by the processing means on the basis of the result of the detection. In the accompanying drawings: Fig. 1 is a plan of one embodiment of an electromagnetic shielding abnormality detecting system which is installed in a building according to the present invention; Fig. 2 is a plan view showing one example of disposition of sensors on each floor of the building; Fig. 3 is a block diagram of the electromagnetic shielding abnormality detecting system which is installed in a building according to the present invention; and Fig. 4 is a flowchart showing the processing executed by the wave level checking and judging unit. One embodiment of the present invention will be described hereinunder with reference to the accompanying drawings. Referring to Fig. 1, the reference numeral 1 denotes a building, 2 radio master units, 3 a wave level checking and judging unit, 4 sensors, 5 a radio communication system, 6 a visual display, 7 a printer and 8 external radio waves. The sensors 4 are disposed in the building 1 to detect radio waves, such as broadcast and telecast waves, which are usually present outside the building 1 in the vicinity of the frequency of a radio wave which is the object of magnetic shielding, that is, the frequency which is assigned to and used for radio communication inside the building 1. In order to provide accuracy in detection of an abnormality in electromagnetic shielding, it is necessary to dispose the sensors 4 on each floor of the building 1 and in every direction, as shown in Fig. 2, so that it is possible to detect the intensity level of any externally intruding radio wave at each floor and from any direction and it is easy to specify precisely a position where an electromagnetic shielding abnormality occurs. The radio master unit 2 of the system 5 are used for radio communication on every floor, while the wave level checking and judging unit 3 monitors the signal from each sensor 4 in order to detect an abnormality in electromagnetic shielding. When the overall level checking portion a of unit 3 detects an abnormality, the wave level floor checking and control portion 3 b controls the radio master unit 2 on the floor where the abnormality is found so as to lower the output level of the radio signal at the floor concerned. Fig. 3 shows a specific example of the system arrangement wherein an external radio wave is detected by each sensor 4 and the level of the detected radio wave is checked to find an abnormal position, while Fig. 4 shows the flow of processing executed by the system. The level checking and judging unit 3 checks the level of an external radio wave having a target frequency which is received by each sensor 4 on the basis, for example, of a preset normal value. If the level of the received radio wave exceeds the normal value, the unit 3 recognizes the floor and directional position where the sensor 4 concerned is installed, and delivers to the radio communication system 5 an abnormality detection signal which informs the system 5 of an abnormality in the electromagnetic shielding. In response to the signal, the radio communication system 5 lowers the output level of the signal transmitted from the radio master unit 2 on the floor where the electromagnetic shielding is found to be abnormal, and further activates an acoustic alarm means or an optical (display) alarm means to inform the operator of the occurrence of an abnormality. In the electromagnetic shielding abnormality detecting system which is installed in a building according to the present invention, external radio waves, such as broadcast waves, which are usually present in the vicinity of the frequency of a radio wave which is the object of electromagnetic shielding are monitored inside the building, so that an abnormality in the electromagnetic shielding of the building is detected on the basis of the fact that the level of a received external radio wave exceeds a predetermined normal value, and when an abnormality occurs, the output of the internal radio wave on the floor where the abnormality is found is immediately lowered and, at the same time, an alarm means is activated to inform the operator of the occurrence of an abnormality. Accordingly, it is possible to take a countermeasure promptly without any risk of the electromagnetic shielding being left in an abnormal state for a long time. It should be noted that the present invention is not necessarily limited to the above-described embodiment and various changes and modifications may be imparted thereto. For example, although in the foregoing embodiment an electromagnetic shielding abnormality is detected according to whether or not the level of a received external radio wave exceeds a normal value and, when an abnormality is found, the output of the internal radio wave on the floor concerned is lowered and the operator is informed of the occurrence of an abnormal situation, it is also possible to diagnose deterioration of the electromagnetic shielding performance by comparison with reception level data or a normal value obtained in the past. As will be clear from the foregoing description, according to the present invention, lowering or deterioration in the electromagnetic shielding performance is checked on the basis of the level of a received external radio wave. Therefore, it is possible to detect an electromagnetic shielding abnormality with a system which is less costly. In addition, since no movable element is used, it is possible to provide a system which requires no labor and which exhibits high durability.

Claims: A building in which is installed a system for detecting leakage of radio waves into the building (1) which is constructed of electromagnetically shielding material for its external structure and the openings therein, so as to detect defects in said shielding, which system comprises: radio wave detecting means (4) inside said building for detecting the presence of externally generated radio wave signals; level judging means (3) for judging the level of said detected external radio waves; and processing means for detecting and processing an abnormality on the basis of the output from said level judging means, whereby an abnormality in the electromagnetic shielding performance is detectable on the basis of the intensity level of a detected radio wave intruding into said building from the outside; characterized in that the radio wave detecting means (4) is disposed on each floor of the building (1) and in every direction, and said level judging means (3) is arranged to judge the electromagnetic shielding performance to be abnormal on the basis of the fact that the level of a detected external radio wave exceeds a normal value, and thereby to identify the floor of the building where the abnormality is present. A building as claimed in Claim 1, wherein said processing means is arranged so as to lower the output of a radio wave transmitter (2) for communication inside said building at a floor where abnormality in the shielding has been detected. A method of detecting leakage of radio waves into a shielded building, which comprises using a system as defined in Claim 1 or 2, and noting any abnormality of the output of the level judging means (3), thereby to identify the floor of the building where there is a defect in the shielding.

Inventors: ISHIKAWA TOSHIYUKI, NAGATA KOJI, NAKAMURA MASATAKE, TAKAHASHI TAKESHI, YABANA YOSHIJI, ISHIKAWA, TOSHIYUKI, NAGATA, KOJI, NAKAMURA, MASATAKE, TAKAHASHI, TAKESHI, YABANA, YOSHIJI
Applicants: SHIMIZU CONSTRUCTION CO LTD, SHIMIZU CONSTRUCTION CO. LTD.
Application year: 1988
Main classification: G01R29
IPC codes: H04B15, H05K9, G01R29