SPECIFICATIONRadio frequency detectorThe present invention relates to radio frequency detectors for giving warning of excessive electro-magnetic radiation.
Many modern activities involve the production of electro-magnetic radiation-for example radio, radar and television transmission, many manufacturing processes, and even the household micro-wave oven which is becoming increasingly popular. Excessive electromagnetic radiation can be extremely harmful to the human body and there is a legal iimit to exposure of 10mW/sq.cm. The nature of electro-magnetic radiation is such that there is no physiological response in the human frame to its presence. Fortunately sources of potentially damaging levels of radiation are readily identifiable and harmful effects can be avoided by suitable safety procedures such as, for example screening between a radiation source and personnel.However accidents do happen as a result, for example, of incorrect positioning of screening, faulty equipment, incorrect operation of equipment, and non-realisation that equipment is currently in operation. There is, therefore, a requirement for a device which will give warning to persons operating in the neighbourhood of non ionising electro-magnetic radiation transmitting equipment of the presence of dangerous radiation.
According to the present invention a radio frequency detector has detector means adapted to detect electro-magnetic radiation in any polarisation, an amplifier, and warning means, the detector being tuned such that the warning means is actuated when the intensity of electro-magnetic radiation exceeds a predetermined level. In one form of the invention suitable for detecting radiation in the range 2-16 Gigahertz the detection means includes two micro wave diodes situated at right angles to one another.
The warning means preferably include a buzzer, a warning light or both. In a preferred form of the invention the device also includes means for indicating that it is functioning correctly.
The device is preferably powered by a rechargeable battery.
One embodiment of the invention, suitable for detecting radiation in the range 2-16 Gighertz, will now be described, by way of example only, with reference to the accompanying diagrammatic drawings of which:Figure 1 is a circuit diagram, andFigures 2 and 3 are component layout diagrams.
A radio frequency detector suitable for detecting microwaves (Figs. 1 and 2) has 2 microwave diodes 10 mounted at right angles to one another. The diodes 10 are connected to an amplifier circuit having, amongst other components, a high impedance input amplifier 11 and a booster amplifier 12, and links 13.
The device has a driver unit shown generally at 14 which includes a test point 15, and a 4.8 volt battery 16. A first switch 17 connects the battery into the circuit (as shown inFig. 1) or to a power input line 18. A green light emitting diode 19 is included in the circuit at all times when the battery is in circuit, and a second switch 20 is moveable between an off position (as indicated in Fig. 1) and an on position, in which current passes through a red light emitting diode 21 and a piezo electric buzzer 22 in response to signals from the microwave diodes 10. In use the device is adjusted using the links 13 such that the second switch 20 is operated when the microwave diodes 10 detect electro-magnetic radiation in excess of a predetermined value such as, for example, the legal limit of 10mW/sq.cm.The first switch 17 connects the battery 16 to a power source through the connection 18 until the battery 16 is full charged. The first switch 17 is then moved to the operative position switching the device on, as will be indicated by the green light emitting diode 19. The device is then attached to a suitable portion Of a person's clothing such as a lapel or a breast pocket. Should the wearer enter a electromagnetic radiation field in excess of the predetermined level this will be-detected by the microwave diodes 10 which will actuate the second switch 20 causing the red light emitting diode 21 to light and the buzzer 22 to sound giving warning to the wearer that he is in danger.
It will be realized that as a result of the microwave diodes 10 being positioned at right angles polarized radiation will be detected whatever the direction of the polarisation relative to the device.
Details of the circuitry will be readily apparent to those skilled in the art and will therefore not be discussed in detail herein.
It will be realized that many variations of the device are possible within the scope of the invention. For example whilst the device described above with reference to Figs. 1 to 3 is suitable for detecting signals in the range of 2-16 Gigahertz a device capable of detecting signals at a frequency as low as 100kHz may be obtained by substituting broad band untuned circuits for the microwave diodes 10.
1. A radio frequency detector having detector means adapated to detect electro-magnetic radiation in any polarisation, an amplifier, and warning means, the detector being tuned such that the warning means is actuated when the intensity of electro-magnetic radiation exceeds a predetermined level.
2. A radio frequency detector as claimed inClaim 1 wherein the detector means includes tw microwave diodes situated at right angles
**WARNING** end of DESC field may overlap start of CLMS **.