Abstract:
An antenna for wireless communication includes a radiator for receiving and transmitting radio frequency (RF) signals comprising a plurality of recesses formed on the sides of the radiator, a feeding plate stretching out from the radiator for transmitting the RF signals, and a ground plate stretching out from the radiator for grounding.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an antenna for wireless communication, and more specifically, to a planar inverted F antenna (PIFA) with asymmetric or symmetric perturbations.  
           [0003]    2. Description of the Prior Art  
           [0004]    In modern information-oriented society, it is desirable that information is accessible at anytime and at anyplace. Wireless communication equipment is capable of transmitting signals without the use of cables or optical fibers making wireless communication undoubtedly the best way to transmit information. As technology develops, various kinds of wireless communication devices, such as mobile phones and personal digital assistants (PDAs), have become an important means of communicating due to their compactness and portability.  
           [0005]    In the field of wireless communication equipment, antennas, which are used to transmit and receive radio waves in order to transfer and exchange data signals, are unquestionably one of the most important devices. Especially in modern portable wireless communication devices, antennas are required to be compact and must be designed to occupy less space in order to match pace with the miniaturization trend of portable wireless devices. In addition, as the bit rate of radio data signals (sometimes measured in units of bits/second) increases, antenna bandwidth requirements increase as well.  
           [0006]    Please refer to FIG  1 . FIG  1 . is a block diagram of a conventional PDA  2 . The PDA  2  includes a processing module  3 , a liquid crystal display (LCD)  4 , a radio frequency (RF) module  5 , an antenna  6 , a power circuit  7 , a universal serial bus (USB) interface  8 , and a universal a synchronous receiver/transmitter (UART)  9 . The processing module  3  is for controlling data of the PDA  2 , the LCD  4  is for displaying an information platform and data of the processing module  3 , the RF module  5  is for processing signals from the antenna  6  and the processing module  3 , the antenna  6  is for transmitting RF signals, the power circuit  7  provides power to the processing module  3  in order to maintain the operation of the PDA  2 , and the USB interface  8  and the UART  9  allow interface to other peripherals for the PDA  2 . An RF signal received by the antenna  6  is transmitted at first to the RF module  5  for demodulation, and then the demodulated signal is transmitted to the processing module  3  for data processing. When the RF module  5  receives a signal from the processing module  3 , the RF module  5  modulates the signal into an RF signal and radiates the RF signal from the antenna  6  to implement wireless communication.  
           [0007]    Concerning the antenna  6  in FIG. 1, please refer to FIG. 2. FIG. 2 illustrates a conventional planar inverted F antenna  10  installed on a circuit board  12 . The antenna  10  is a PIFA and includes a radiator  14  for receiving and transmitting RF signals, a feeding plate stretching out of the radiator  14  and connected perpendicularly to a feed pad  18  on the circuit board  18  for transmitting RF signals, and a ground plate  20  stretching out from the radiator  14  and connected perpendicularly to the ground plane  22  on the circuit board  12 . The antenna  10  is a single-frequency antenna, which transmits and receives RF signals through the resonance of the radiator  14 . The length of the antenna  14  may influence the frequency range for transmission and reception of RF signals.  
           [0008]    However, in the conventional antenna  10 , the radiator  14  is a conductive strip with straight edges, and its length is approximate quarter the wavelength of the RF signal. Thus, it is a purpose of the present invention to reduce the length of the antenna  10 .  
         SUMMARY OF INVENTION  
         [0009]    It is therefore a primary objective of the present invention to provide a PIFA with asymmetric or symmetric perturbations for the above-mentioned purpose.  
           [0010]    Briefly summarized, an antenna for wireless communication includes a radiator for receiving and transmitting radio frequency (RF) signals comprising a plurality of recesses formed on the side of the radiator, a feeding plate stretching out from the radiator for transmitting the RF signals, and a ground plate stretching out from the radiator for grounding.  
           [0011]    According to the present invention, an antenna for wireless communication includes a substrate comprising a long side, a short side, and two apertures formed along the short side and penetrating the substrate, a radiator formed for receiving and transmitting RF signals on the upper surface of the substrate comprising a plurality of recesses formed on the side of the radiator, a feeding plate connected to the radiator via the apertures for transmitting the RF signals, a ground plane formed on the lower surface of the substrate, a ground plate connected to the radiator and the ground plane via the apertures, and a trench formed between the feeding plate and the ground plate.  
           [0012]    These objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]    [0013]FIG. 1 is a block diagram of a conventional PDA.  
         [0014]    [0014]FIG. 2 illustrates a conventional PIFA installed on a circuit board.  
         [0015]    [0015]FIG. 3 illustrates a PIFA according to the first embodiment of the present invention.  
         [0016]    [0016]FIG. 4 illustrates a PIFA according to the second embodiment of the present invention.  
         [0017]    [0017]FIG. 5 illustrates a PIFA according to the third embodiment of the present invention.  
         [0018]    [0018]FIG. 6 illustrates a PIFA according to the fourth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]    Please refer to FIG. 3 showing a planar inverted F antenna  48  according to the first embodiment of the present invention. In this embodiment, the antenna  48  includes a substrate  36 , a ground plate  30 , a feeding plate  32 , a ground plane  40 , and a radiator  38  for receiving and transmitting RF signals. The radiator  38  includes a plurality of recesses  37  and a trench  42 . The plurality of recesses  37  is formed on the two side of the radiator  38 . The substrate  36  has a long side D 1  and a short side L 1 . The substrate  36  further includes two apertures formed along the short side of the substrate  36  and penetrating the substrate  36 . The feeding plate  32  is connected to the radiator  38  via an aperture, so that the radiator  38  transmits RF signals via the feeding plate  32 . The ground plate  30  is also connected to the radiator  38  and the ground plane  40  via an aperture.  
         [0020]    As shown in FIG. 3, the trench  42  is formed on a side of the radiator  38 , and positioned between the ground plate  30  and the feeding plate  32 . The width L 2  and the length D 2  of the trench  42  may influence the impedance matching of the antenna  48 , as does the distance between the ground plate  30  and the feeding plate  32 .  
         [0021]    The plurality of recesses  37  on the two side of the radiator  38  is arranged asymmetrically and periodically for generating periodical perturbation, in order to shorten the resonance length and shorten the length of the antenna  48  as well.  
         [0022]    Please refer to FIG. 4 showing a planar inverted F antenna  50  according to the second embodiment of the present invention using the same numbering to that in FIG. 3. The functions of the devices in the second embodiment is essentially the same to the first embodiment, thus a repeated description is hereby omitted. The difference between the two embodiments is that, the antenna  50  further includes two metal apertures  44 ,  46  for capacitive loading, so that the length of the antenna can be further reduced.  
         [0023]    Please refer to FIG. 5 and FIG. 6. FIG. 5 illustrates a planar inverted F antenna  60  according to the third embodiment, and FIG. 6 illustrates a planar inverted F antenna  70  according to the fourth embodiment of the present invention using the same numbering to that in FIG. 3. The functions of the devices in the antenna  60  according to the third embodiment are essentially the same to that in the antenna  48  according to the first embodiment. Similarly, the functions of the devices in the antenna  70  according to the fourth embodiment are essentially the same to that in the antenna  50  according to the second embodiment, thus repeated descriptions are hereby omitted. The difference between the third and the first embodiment, as well as between the fourth and the second embodiment, is that the radiator  62  according to the third embodiment and the radiator  72  according to the fourth embodiment generates periodical perturbation by a plurality of recesses arranged symmetrically and periodically, in order to shorten the resonance length and shorten the length of the radiator as well.  
         [0024]    The antennas  48 ,  50 ,  60 ,  70  according to the first, second, third and fourth embodiments respectively all include a substrate. However, this is for example only and an antenna without a substrate can also be used according to the present invention.  
         [0025]    In contrast to the prior art, the PIFA according to the present invention generates periodical perturbation using the plurality of recesses arranged asymmetrically and periodically on the two sides of the radiator  38 ,  52  according to the first and second embodiments or symmetrically and periodically on the two sides of the radiator  62 ,  72  according to the third and fourth embodiments, so that the resonance length and the length of the radiator can be reduced. Additionally, the length of the antenna can be shortened due to capacitive loading of the two metal apertures  44 ,  46 . Consequently, the present invention shows a more practical and efficient way to utilize an antenna in compact wireless mobile communication devices when compared with a conventional PIFA.