Abstract:
A battery-free electromagnetic leakage detector includes a substrate, an antenna, a filter circuit electrically connected with the antenna, a clamp circuit electrically connected with the filter circuit, and an indicating member electrically connected with the clamp circuit. Accordingly, the battery-free electromagnetic leakage detector is structurally simple and compact and can detect electromagnetic waves and display the detection without connection with any external power source.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to an apparatus capable of detecting electromagnetic waves, and more particularly, to a battery-free electromagnetic leakage detector without power supply or battery. 
         [0003]    2. Description of the Related Art 
         [0004]    As the technology progresses through time, the high-technology products also keep progressing. People in the modern time have become more and more dependent on the high-technology products for convenience and their lives are full of electric/electronic products including high-energy appliances, such as electric stoves, microwave stoves, wireless communication products, etc. 
         [0005]    In the daily living environment, the electric appliances are everywhere. However, the currents flowing in the circuit definitely generate electromagnetic waves which may be hazardous to health. Therefore, it is necessary to take precautions for detecting and preventing the electromagnetic waves from leakage. Although active electromagnetic detectors are commercially available for precise detection of the magnitude of the electromagnetic waves, they are expensive and inconveniently portable. 
         [0006]    Among the prior art, there are other approaches of detecting the electromagnetic waves, like U.S. Patent Laid-open No. 2006/0289525 entitled “Microwave Leakage Indicator Card”, which disclosed that an antenna is employed for receiving the microwave energy and then such microwave energy is converted into thermal energy via a back-end circuit to further change the color of the proposed temperature sensitive color indicator for displaying the detection of the electromagnetic waves. Besides, Taiwanese Patent No. M357,670 disclosed a thin energy-saving security alert discoloring device for electromagnetic waves, in which an antenna resonant circuit detects the electromagnetic waves and converts them into magnetic energy to drive a magnetically discoloring material to discolor for displaying detection of the electromagnetic waves. 
       SUMMARY OF THE INVENTION 
       [0007]    The primary objective of the present invention is to provide a battery-free electromagnetic leakage detector, which can detect electromagnetic waves and display the detection without connection with any external power source. 
         [0008]    The secondary objective of the present invention is to provide a battery-free electromagnetic leakage detector, which is structurally simple and compact. 
         [0009]    The foregoing objectives of the present invention are attained by the battery-free electromagnetic leakage detector composed of a substrate, an antenna, a filter circuit electrically connected with the antenna, a clamp circuit electrically connected with the filter circuit, and an indicating member electrically connected with the clamp circuit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic view of a preferred embodiment of the present invention, showing that an antenna is mounted to one side of a substrate. 
           [0011]      FIG. 2  is another schematic view of the preferred embodiment of the present invention, showing that a filter circuit and a clamp circuit are mounted to the other side of the substrate. 
           [0012]      FIG. 3  is a circuit diagram of the preferred embodiment of the present invention. 
           [0013]      FIGS. 4(A)-4(C)  show that indicating members are a color-change indicator, an audio indicator, and a digital display separately. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0014]    Referring to  FIGS. 1-3 , a battery-free electromagnetic leakage detector  10  constructed according to a preferred embodiment of the present invention is composed of a substrate  11 , an antenna  21 , a filter circuit  31 , a clamp circuit  41 , and an indicating member  51 . The detailed descriptions and operations of these elements as well as their interrelations are recited in the respective paragraphs as follows. 
         [0015]    The substrate  11  is a circuit board in this embodiment. 
         [0016]    The antenna  21  is a plate-like planar antenna in this embodiment and located on one of two opposite sides of the substrate  11 . The filter circuit  31 , the clamp circuit  41 , and the indicating member  51  are located on the other side of the substrate  11 . 
         [0017]    The filter circuit  31  is a low pass filter circuit composed of an inductor L and a first capacitor C 1 . The inductor L is made of an elongated copper foil with a predetermined width. The first capacitor C 1  is made of an elongated copper foil having a predetermined width and curved in the shape of an L. At high frequency, the elongated copper foil with the predetermined width can function as an inductor, and the L-shaped elongated copper foil can function as a capacitor. The filter circuit  31  is electrically connected with the antenna  21  via the inductor L. The antenna  21  and the filter circuit  31  which are located on two opposite sides of the substrate  11  are electrically connected with each other via a plated through hole running through the substrate  11 . 
         [0018]    The clamp circuit  41  is composed of two Schottky diodes SD 1  connected in series. The filter circuit  31  is electrically connected with a second capacitor C 2  and then the second capacitor C 2  is electrically connected with the clamp circuit  41 . 
         [0019]    The indicating member  51  is a light emitting diode (LED) in this embodiment and is electrically connected with the clamp circuit  41 . 
         [0020]    It is to be noted that the location of the antenna  21  and the other elements, like the filter circuit  31 , are not limited to the opposite two sides of the substrate  11 , as an example only, and can alternatively be the same side of the substrate  11 . 
         [0021]    Similarly, the indicating member  51  is not limited to the LED, as an example only, and can alternatively be a color-change indicator  51   a , an audio indicator  51   b , or a digital indicator  51   c , as shown in  FIGS. 4(A) to 4(C) , to have the same effect. 
         [0022]    Likewise, the filter circuit  31  is not limited to the low pass filter circuit, as an example only, can alternatively be a band pass filter circuit to have the same effect. The inductor L of the filter circuit  31  can alternatively be a chip inductor or a discrete inductor. The first capacitor C 1  can alternatively be a chip capacitor or a discrete capacitor. Because the band pass filter circuit, the chip inductor, the discrete inductor, the chip capacitor, and the discrete capacitor belong to the prior art, they are unnecessarily shown in the drawings. 
         [0023]    In addition, the antenna  21  is not limited to the planar antenna, as an example only, and can alternatively be a directional antenna, an omnidirectional antenna, a broadband antenna, or any other antenna. Because such antennas belong to the prior art, they are unnecessarily shown in the drawings. 
         [0024]    Referring to  FIG. 3 , when there are electromagnetic waves outside, the antenna  21  can detect and convert their energy into electric energy and then the electric energy can flow to the filter circuit  31 ; the filter circuit  31  can filter the electric energy out of the sensing coverage thereof. The passed electric energy enhances its voltage level via the clamp circuit  41  and meanwhile is rectified through one of the Schottky diodes SD 1  to convert the AC electric energy into the DC one to further drive illumination of the indicating member  51  for security alert. Besides, the clamp circuit  41  operated at high frequency can generate high harmonics which can, by means of the filter circuit  31 , reduce the energy loss radiated outside through the antenna  21 . 
         [0025]    When the intensity of external electromagnetic waves is higher than a predetermined magnitude, the indicating member  51  can illuminate to remind the user that the electromagnetic waves have been higher than certain intensity, thus displaying the detection of the electromagnetic waves. 
         [0026]    In addition, the battery-free electromagnetic leakage detector  10  of the present invention does not need any external power source for operation. 
         [0027]    Moreover, the elements of the present invention are mounted on two opposite sides of the substrate  11 , such that the present invention can be very thin in appearance to facilitate the user to attach it to a surface of a to-be-detected object. Therefore, the present invention includes advantages of simple structure and small size. 
         [0028]    Although the present invention has been described with respect to a specific preferred embodiment thereof, it is in no way limited to the specifics of the illustrated structures but changes and modifications may be made within the scope of the appended claims.