Abstract:
A mobile telecommunication apparatus reduces current around a control circuit on a printed circuit board so as to lessen background noise and to improve the radiation characteristic. The mobile telecommunication apparatus includes a printed circuit board located in a body of the mobile telecommunication apparatus; a radio circuit including a modulator circuit and a demodulator circuit arranged on the printed circuit board; a control circuit including a voice circuit for processing a voice signal arranged on the printed circuit board; a first earth conductor for grounding the radio circuit; a second earth conductor for grounding the control circuit and being continuous with the first earth conductor; an antenna connected to the radio circuit; and a slit arranged between the first earth conductor and the second earth conductor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mobile telecommunication apparatus such as a portable telephone and a PHS telephone. 
     2. Description of the Prior Art 
     FIG. 18 illustrates a conventional mobile telecommunication apparatus shown in Japanese Laid-Open Patent Publication No. 7-74807, “A Portable Telephone”. FIG. 18 includes a body  1  of a telecommunication apparatus, an antenna  2 , a transmitter  3 , and a receiver  4 . 
     FIG. 19 is a perspective view which illustrates an internal construction of a conventional mobile telecommunication apparatus. FIG.  20  and FIG. 21 are sectional views seen from a line A-B and a line C-D in FIG. 19, respectively. 
     In FIG.  19 -FIG. 21, the mobile telecommunication apparatus includes a printed circuit board  5 , a radio circuit  6  formed on the printed circuit board  5 , a control circuit  7  formed on the printed circuit board  5 , a voice circuit  8 , shield cases  9   a  and  9   b  surrounding the radio circuit  6 , a feeder line  10 , a feeding circuit  11 , an earth conductor  12  for the radio circuit  6 , an earth conductor  13  for the control circuit, an earth conductor  14  formed between the earth conductors  12  and  13 , and a battery  15 . 
     The printed circuit board  5  is actually a multi-layered circuit board. Parts constructing the radio circuit  6  and the control circuit  7  are mounted on the printed circuit board  5 . The voice circuit  8  is included in the control circuit  7 . 
     The shield cases  9   a  and  9   b  are equipped to shield external noise coming into the radio circuit  6  and to prevent the escape of radiation to the outside. However, since the shield construction around the control circuit  7  is complicated, the shield construction is not generally included. 
     The antenna  2  generally uses a λ/4 monopole antenna (λindicates a wavelength of the frequency being used) or a λ/2 monopole antenna. Impedance of a λ/4 monopole antenna is easily matched and the structure of the feeding circuit  11  is relatively simple. The radiation characteristic of the λ/2 monopole antenna is better than the λ/4 monopole antenna although the construction of feeding circuit  11  becomes a little bit complicated due to impedance matching. The earth conductor  12 , the earth conductor  13 , and the earth conductor  14  arc equipped on the printed circuit board  5 . The earth conductor  14  is equipped between the earth conductor  12  and the earth conductor  13 , and they are connected electrically. 
     The operation of the conventional mobile telecommunication apparatus is explained below. During transmitting, a human voice from a transmitter  3  is converted to a voice signal through the voice circuit  8  in the control circuit  7 . The voice signal is modulated to a high frequency signal by the radio circuit  6 . The modulated high frequency signal is radiated from the antenna  2  via the feeding circuit  11 . 
     On the other hand, during receiving, a high frequency modulated signal which enters the radio circuit  6  via the feeding circuit  11  from the antenna  2  is demodulated to a voice signal through a demodulator circuit. The demodulated voice signal is transduced into an audible human voice by the receiver  4  via the voice circuit  8  in the control circuit  7 . Also, the battery  15  supplies power to the radio circuit  6  and the control circuit  7 . 
     FIG. 22 illustrates an example of a longitudinal current distribution on the side of the printed circuit board  5  facing the battery  15  in the conventional mobile telecommunication apparatus using a λ/4 monopole antenna as the antenna  2 . 
     In FIG. 22, numerals  16  and  17  indicate current amplitude and phase which distribute along the antenna  2  and the radio circuit  6 , respectively. Numerals  18  and  19  indicate current amplitude and phase which distribute along the control circuit  7 , respectively. 
     Current flowing through the earth conductor  14  equipped between the radio circuit  6  and the control circuit  7  is amplified by a parallel plane mode oscillation between the battery  15  and the control circuit  7  that generates a sinewave current  18  having large amplitude. 
     This current having a sinewave distribution greatly influences the voice circuit  8  in the control circuit  7 . This current generates noise in the voice signal which is then transduced by the receiver  4  thereby decreasing the speech quality. 
     Also, the phase  19  of the current flowing along the control circuit  7  on the printed circuit board  5  is contrary to the phase  17  of current distributing between the antenna  2  and the radio circuit  6 . Therefore, the antenna gain of the telecommunication apparatus toward the horizontal direction is extremely attenuated, which decreases the available communication distance. 
     SUMMARY OF THE INVENTION 
     It is an object of the presentation to reduce current around the control circuit on the printed circuit board and to obtain a mobile telecommunication apparatus having less background noise and good antenna radiation characteristics. 
     According to an aspect of the invention, a mobile telecommunication apparatus includes a printed circuit board equipped in a body of the mobile telecommunication apparatus; a radio circuit including modulator circuit and a demodulator circuit arranged on the printed circuit board; a control circuit including a voice circuit for processing a voice signal arranged on the printed circuit board; a first earth conductor for grounding the radio circuit; a second earth conductor for grounding the control circuit and being continuous with the first earth conductor; an antenna connected to the radio circuit; and a slit arranged between the first earth conductor and the second earth conductor. 
     According to another aspcct of the invention, a mobile telecommunication apparatus includes first and second printed circuit boards equipped in a mobile telecommunication apparatus; a radio circuit including a modulator circuit and a demodulator circuit arranged on the first printed circuit board; a control circuit including a voice circuit for processing a voice signal arranged on the second printed circuit board; a first earth conductor for grounding the radio circuit on the first printed circuit board; a second earth conductors for grounding the control circuit on the second printed circuit board; a third earth conductors on the second printed circuit board being electrically connected with the second earth conductor; a connector for connecting the first earth conductor with the third earth conductor; an antenna being connected to the radio circuit; and a slit arranged between the second earth conductor and the third earth conductor. 
     In one preferable alternative, the antenna of the mobile telecommunication apparatus is a slot inner antenna constructed by λ/4 wavelength slot arranged at one portion of the printed circuit board. 
     In another preferable alternative, the antenna of the mobile telecommunication apparatus is a λ/4 wavelength monopole antenna protruding toward outside of the apparatus body. 
     The inner antenna of the mobile telecommunication apparatus can also be a λ/2 monopole antenna protruding toward outside of the apparatus body which is excited from the inner antenna by way of non-contact feeding thereby providing a further alternative. 
     The slit is also preferably constructed by pattern etching process on the printed circuit board. 
     According to a further aspect of the invention,a mobile telecommunication apparatus includes a printed circuit board equipped in a body of the mobile telecommunication apparatus; a radio circuit including modulator circuit and a demodulator circuit arranged on the printed circuit board; a control circuit including a voice circuit for processing a voice signal arranged on the printed circuit board; a first earth conductor formed on a first surface of the printed circuit board for grounding the radio circuit; a second earth conductor formed on a second surface of the printed circuit board for grounding the control circuit; a third earth conductor located on the second surface of the printed circuit board at a corresponding location facing the first earth conductor and being electrically connected with the second earth conductor; a fourth earth conductor located on the first surface of the printed circuit board at a corresponding location facing the second earth conductor; a battery facing the fourth earth conductor; an antenna connected to the radio circuit; and a first slit for electrically separating the first earth conductor and the fourth earth conductor; and a second slit arranged between the second earth conductor and the third earth conductor. 
     According to a further aspect of the invention, a mobile telecommunication apparatus includes a printed circuit board equipped in a body of the mobile telecommunication apparatus; a radio circuit including modulator circuit and a demodulator circuit arranged on the printed circuit board; a control circuit including a voice circuit for processing a voice signal arranged on the printed circuit board; a first earth conductor formed on a first surface of the printed circuit board for grounding the radio circuit; a second earth conductor formed on a second surface of the printed circuit board for grounding the control circuit; a third earth conductor located on the second surface of the printed circuit board at a corresponding location facing the first earth conductor for grounding the radio circuit; a fourth earth conductor located on the first surface of the printed circuit board at a corresponding location facing the second earth conductor for grounding the control circuit; a battery being placed facing the fourth earth conductor; an antenna connected to the radio circuit; and a first slit for electrically separating the first earth conductor and the fourth earth conductor; and a second slit for electrically separating the second earth conductor and the third earth conductor. 
     According to a further aspect of the invention, a mobile telecommunication apparatus includes a multi layered printed circuit board equipped in a body of the mobile telecommunication apparatus, the multi layer includes a plurality of earth conductors and dielectric boards interleaved between the earth conductors; each of the earth conductors includes a first earth conductor for grounding a radio circuit and a second earth conductor for grounding the control circuit; a slit each for electrically separating the first earth conductor and the second earth conductor; a battery being placed facing the second earth conductors; and some of the first earth conductors on any of the surfaces of the dielectric boards arc connected to the any second earth conductors on another surface of the dielectric boards through the earth conductor and the dielectric board. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a perspective view which illustrates an internal construction of a mobile telecommunication apparatus of a first embodiment of the present invention; 
     FIG. 2 is a diagram showing one example of the current on the printed circuit board of the first embodiment of the present invention; 
     FIG. 3 is a perspective view which illustrates a mobile telecommunication apparatus of the second embodiment of the present invention; 
     FIG. 4 is a side sectional diagram which illustrates a mobile telecommunication apparatus of the second embodiment of the present invention; 
     FIG. 5 is a perspective view which illustrates a mobile telecommunication apparatus of the third embodiment of the present invention; 
     FIG. 6 is a diagram showing each separated layer to show a slot antenna of the third embodiment of the present invention; 
     FIG. 7 is a diagram showing calculated values of longitudinal current distribution on the printed circuit board without a slit; 
     FIG. 8 is a diagram showing calculated values of longitudinal current distribution on the printed circuit board with a slit in the third embodiment of the present invention; 
     FIG. 9 is a perspective view showing a structural overview of a mobile telecommunication apparatus of the fourth embodiment of the present invention; 
     FIG. 10 is a perspective view showing a mobile telecommunication apparatus of a fifth embodiment of the present invention; 
     FIG. 11 is a side sectional diagram to explain the operation principle of a mobile telecommunication apparatus of the fifth embodiment of the present invention; 
     FIG. 12 is a diagram showing calculated values of longitudinal current distribution on a printed circuit board without a slit in a mobile telecommunication apparatus having a non-contact antenna, which excites a λ/2 monopole antenna protruding toward outside of the apparatus body; 
     FIG. 13 is a diagram showing calculated values of longitudinal current distribution on a printed circuit board with a slit in a mobile communication of the fifth embodiment of the present invention; 
     FIG. 14 is a perspective view showing a mobile telecommunication apparatus of a sixth embodiment of the present invention; 
     FIG. 15 is a front view showing a printed circuit board equipped in a mobile telecommunication apparatus of the sixth embodiment of the present invention; 
     FIG. 16 is a diagram showing a locational relationship between a printed circuit board and a battery which are included in a mobile telecommunication apparatus of the seventh embodiment of the present invention; 
     FIG. 17 is a diagram showing a locational relationship between a printed circuit board and a battery which are included in a mobile telecommunication apparatus of an eighth embodiment of the present invention; 
     FIG. 18 illustrates a conventional mobile telecommunication apparatus; 
     FIG. 19 is a perspective view which illustrates an internal construction of a conventional mobile telecommunication apparatus; 
     FIG.  20  and FIG. 21 are sectional views seen from a line A-B and a line C-D in FIG. 19, respectively; and 
     FIG. 22 illustrates an example of a longitudinal current distribution on the printed circuit board facing a battery in the conventional mobile telecommunication apparatus which uses a λ/4 monopole antenna. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, arc given by way of illustration only, since various changes and modifications in the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     Embodiment 1 
     A first embodiment of the present invention is explained below. FIG. 1 is a perspective view which illustrates an internal construction of a mobile telecommunication apparatus of a first embodiment of the present invention. 
     FIG. 1 includes a body  1  of a telecommunication apparatus, an antenna  2 , a transmitter  3 , a receiver  4 , a printed circuit board  5 , a radio circuit  6  formed in the printed circuit board  5 , a control circuit  7  formed in the printed circuit board  5 , a voice circuit  8 , shield cases  9   a  and  9   b  surrounding the radio circuit  6 , a feeder line  10 , a is  5  feeding circuit  11 , an earth conductor  12  for the radio circuit  6 , an earth conductor  13  for the control circuit, an earth conductor  14  formed between the earth conductors  12  and  13 , and a battery  15 . 
     A slit  20  is notched between the radio circuit  6  and the control circuit  7  on the printed circuit board  5 . The slit  20  forms a narrow earth conductor  14  which connects the earth conductor  12  and the earth conductor  13 . The earth conductor  12  is referred to as a first earth conductor and the earth conductor  13  is referred to as a second earth conductor. The respective first earth conductors  12  and the second earth conductors  13  are part of the printed circuit board  5 , and they are electrically connected via the earth conductor  14 . 
     FIG. 2 illustrates an example of currents flowing on the printed circuit board  5 . In FIG. 2, arrows  21   a - 21   g  represent the directions of current flowing on the earth conductor of printed circuit board  5 . 
     The current  21   b  longitudinally flowing on the earth conductor  12  of the printed circuit board  5  is prevented by the slit  20  and flows through along the slot  20  like the current  21   c . Therefore, the current path along the slot  20  gets longer and the current flowing through the path along the slot  20  is more attenuated. Also, the current  21   d  longitudinally flowing along the earth conductor  14  of the printed circuit board  5  is suppressed because of narrower width of the earth conductor  14 . 
     Thus, the parallel plain board mode generated between the control circuit  7  and the battery  15  shown in FIG. 22 is suppressed, and the current  21   c - 21   f  around the control circuit  7  is reduced. That is, the current amplitude which distributes along the control circuit  7  is reduced. 
     The printed circuit board  5  can be a multi-layered circuit board which includes a single surface circuit board or a double surface circuit board, and the same current decreasing effect can be obtained regardless of the number of layers. 
     Embodiment 2 
     FIG. 3 shows a perspective view which illustrates a mobile telecommunication apparatus according to a second embodiment. FIG. 4 is a sectional diagram of the mobile telecommunication apparatus depicted in FIG.  3 . 
     In FIG.  3  and FIG. 4, the mobile telecommunication apparatus includes a first printed circuit board  22  equipped with a radio circuit  6  and a feeding circuit  11 , a second printed circuit board  23  is equipped with a control circuit  7 , shield cases  9   a  and  9   b  surrounding the radio circuit  6  and a feeding circuit  11 , and a connector for connecting the first printed circuit board  22  with the second printed circuit board  23 . In this second embodiment, the antenna  2  is connected to the feeding circuit  11  on the edge of the first printed circuit board  22 . 
     The slit  20  is arranged between the first earth conductor  12   a  where the radio circuit  6  is equipped and the second earth conductor  13  where the control circuit  7  is equipped. The lower portion of the third earth conductor  12   b  on the second printed circuit board  23  is connected to the first earth conductor  12   a  via the connector  24 . 
     The slit  20  forms a narrow earth conductor  14  which connects the third earth conductor  12   b  and the second earth conductor  13 . Other construction details of the second embodiment are the same as those of the first embodiment. 
     In the second embodiment, a parallel plain board mode occurring between the first printed circuit board  22  and the second printed circuit board  23  generates a sinusoidal current having a large amplitude. However, the current longitudinally flowing on the earth conductor  12   b  of the second printed circuit board  23  is prevented by the slit  20  and flows through along the slot  20  in the same way as explained in the first embodiment. Therefore, the current flowing from the earth conductor  12   a  on the first printed circuit board  22  to the earth conductor  13  on the second printed circuit board  23  via the connector  24  is suppressed because of the narrow width earth conductor  14 . 
     Thus, the parallel plain board mode generated between the battery  15  and the second printed circuit board  23  is suppressed, and the current around the control circuit  7  is reduced. Also, the current between the first printed circuit board  22  and the second printed circuit board  23  due to the parallel plain board mode is suppressed. Accordingly, the current amplitude which distributes along the control circuit  7  is reduced. 
     The first printed circuit board  22  and the second printed circuit board  23  can be multi-layered circuit boards which include a single surface circuit board or a double surface circuit board, respectively, and the same current decreasing effect can be obtained regardless of the number of layers. 
     Embodiment 3 
     FIG. 5 shows a perspective view which illustrates a mobile telecommunication apparatus according to a third embodiment. FIG. 6 shows a plurality of separated layers which comprise a slot antenna  25 . 
     The construction of FIG. 5 is the same as those of the first embodiment of FIG. 1 except for the slot antenna  25 . Therefore, the detailed explanation except for the slot antenna  25  is omitted. 
     In FIG. 6, the printed circuit board  5  is constructed of a multi-layered structure which includes dielectric layers  27   a ,  27   b , and  27   c  sandwiched between respective copper foil pattern layers  26   a ,  26   b ,  26   c , and  26   d , and a plurality of through-hole platings  28  and earth conductors  30   a  and  30   b  which form slots  29   a  and  29   b , respectively. The number of layers is defined by the number of copper foil layers. In FIG. 6, the printed circuit board  5  has four copper foil layers. Therefore, the printed circuit board  5  is referred to as a four layer circuit board. The other construction details are the same as those of the first embodiment, thus, the detailed explanations thereof are omitted. 
     A slot antenna  25  is equivalent to the λ/2 wavelength slot antenna folded into a U-shape. The slots  29   a  and  29   b  are arranged at the top of the earth conductors  30   a  and  30   b , respectively. The electric length of the slots  29   a  and  29   b  is about λ/4 wavelengths under the resonance frequency. The width of the slots  29   a  and  29   b  is small enough compared to the wavelength. The earth conductors  30   a  and  30   b  having slots  29   a  and  29   b , respectively, are shortened via through-hole platings  28 . This slot antenna  25  operates as a slot antenna having about λ/2 electric wavelength under the resonance frequency. 
     Since the slot antenna  25  is formed using the earth conductors  30   a  and  30   b  on the printed circuit board  5 , large currents flow on the earth conductor  12 . 
     An effect of the slit is explained below. FIG. 7 shows calculated values of longitudinal current distribution on a printed circuit board  5  without a slit  20 . FIG. 8 shows calculated values of longitudinal current distribution on a printed circuit board  5  with a slit  20 . The vertical direction on the figure shows normalized current values on a printed circuit board  5 , which is normalized by a feeder current supplied to the slot antenna  25 . 
     As seen from FIG. 7, the maximum normalized current value is 0.123 around the control circuit  7  on the printed circuit board  5  in case that no slit  20  is provided. Alternatively, the maximum normalized current value is 0.031 around the control circuit  7  on the printed circuit board  5  in case that the slit  20  is provided. In other words, by providing the slit  20  on the printed circuit board  5 , the current around the control circuit  7  on a printed circuit board  5  is decreased by about 12 dB. 
     In the same way as explained in the first embodiment, the current longitudinally flowing on the earth conductor  12  of the printed circuit board  5  is prevented by the slit  20 . Therefore, the current path along the slot  20  gets longer and the current flowing through the path along the slot  20  is more attenuated. Also, the current longitudinally flowing along the earth conductor  14  of the printed circuit board  5  is suppressed because of narrower width of the earth conductor  14 . 
     Thus, the parallel plain board mode generated between the control circuit  7  and the battery  15  is suppressed, and the current around the control circuit  7  is reduced. 
     Furthermore, an effect similar to that obtained for the slot antenna can also be obtained for any other antenna such as an inverted F-type antenna equipped inside of the mobile telecommunication apparatus. 
     Also, the printed circuit board  5  can be a multi-layercd circuit board which includes a single surface circuit board or a double surface circuit board, and the same current decreasing effect can be obtained regardless of the number of layers. 
     In addition, it is possible to use two circuit boards each of which is separately equipped with the radio circuit  6  and the control circuit  7 , respectively, as well as one circuit board commonly equipped with both radio circuit  6  and the control circuit  7  thereon. In each case, the same current decreasing effect can be obtained. 
     Embodiment 4 
     FIG. 9 shows a perspective view which illustrates a mobile telecommunication apparatus according to a fourth embodiment. In FIG. 9, the mobile telecommunication apparatus includes a λ/4 wavelength monopole antenna  31 . 
     The λ/4 wavelength monopole antenna  31  preferably consists of a helical type conductor. The impedance characteristic of the λ/4 wavelength monopole antenna is broadband. Also, it is easy to match the impedance with the circuits in the mobile telecommunication apparatus. The other construction details are the same as the construction details of the first embodiment, thus the detailed explanation thereof is omitted. 
     In the same way as explained in the first embodiment, the current longitudinally flowing on the earth conductor  12  of the printed circuit board  5  is prevented by the slit  20 . Therefore, the current path along the slot  20  gets longer and the current flowing along the current path is more attenuated. Also, the current longitudinally flowing along the earth conductor  14  of the printed circuit board  5  is suppressed because of the relatively narrow width of the earth conductor  14 . 
     Thus, the parallel plain board mode generated between the control circuit  7  and the battery  15  is suppressed, and the current around the control circuit  7  is reduced. 
     Furthermore, an effect similar to that obtained with the λ/4 wavelength monopole antenna can also be obtained for any other antenna such as a straight antenna equipped outside of the mobile telecommunication apparatus. 
     Also, the printed circuit board  5  can be a multi-layered circuit board which includes a single surface circuit board or a double surface circuit board, and the same current decreasing effect can be obtained regardless of the number of layers. 
     In addition, it is possible to use two circuit boards each of which is separately equipped with the radio circuit  6  and the control circuit  7 , respectively, as well as one circuit board commonly equipped with both radio circuit  6  and the control circuit  7  thereon. In each case, the same current decreasing effect can be obtained. 
     Embodiment 5 
     FIG. 10 shows a perspective view which illustrates a mobile telecommunication apparatus according to a fifth embodiment. In FIG. 10, the mobile telecommunication apparatus includes a slot terminating portion  32 , a λ/2 monopole antenna  33  excited by a slot antenna  25 , and an antenna terminating portion  34  of the λ/2 monopole antenna  33 . The λ/2 monopole antenna  33 , which is fixed to the body  1  of the mobile telecommunication apparatus, is coupled to the slot antenna  25  without contacting the printed circuit board  5 . 
     The operation of the λ/2 monopole antenna  33  is explained below. FIG. 11 shows a sectional view of the main portion of the fifth embodiment. In FIG. 11, a slot terminating portion  32  and an antenna terminating portion  34  arc placed at a portion where the electrical field is at a maximum. Therefore, the antenna terminating portion  34  of the λ/2 monopole antenna  33  is coupled to the slot terminating portion  32  of the slot antenna  25  via electrical field. The λ/2 monopole antenna  33  is then excited via equivalent capacity  41  between the antenna terminating portion  34  and the slot terminating portion  32 . The other construction details are the same as those of the first embodiment, thus the detailed explanation thereof is omitted. 
     FIG. 12 illustrates a slot antenna  25  which excites the λ/2 monopole antenna  33  equipped at the outside of the apparatus body without contacting the λ/2 monopole antenna. FIG. 12 shows calculated values of longitudinal current distribution on the printed circuit board  5  without a slit  20 . FIG. 13 shows calculated values of longitudinal current distribution on the printed circuit board  5  with a slit  20  in the mobile telecommunication apparatus according to the fifth embodiment of the present invention. 
     As seen from FIG.  12  and FIG. 13, the maximum normalized current value is 0.116 around the control circuit  7  on the printed circuit board  5  in case that no slit  20  is provided, but the maximum normalized current value is 0.012 around the control circuit  7  on the printed circuit board  5  in case that the slit  20  is provided. In other words, by providing the slit  20  on the printed circuit board  5 , the current around the control circuit  7  on the printed circuit board  5  is decreased down to about 20 dB. 
     In the same way as explained in the first embodiment, the current longitudinally flowing on the earth conductor  12  of the printed circuit board  5  is prevented by the slit  20 . Therefore, the current path along the slot  20  gets longer and the current flowing through the path along the slot  20  is more attenuated. Also, the current longitudinally flowing along the earth conductor  14  of the printed circuit board  5  is suppressed because of the relatively narrow width of the earth conductor  14 . 
     Thus, the parallel plain board mode generated between the control circuit  7  and the battery  15  is suppressed, and the current around the control circuit  7  is reduced. 
     Furthermore, an effect similar to that obtained with the λ/2 monopole antenna can also be obtained for any other antenna such as an inverted F-type antenna equipped inside of the mobile telecommunication apparatus or a helical antenna equipped outside of the mobile telecommunication apparatus. 
     Also, the printed circuit board  5  can be a multi-layered circuit board which includes a single surface circuit board or a double surface circuit board, and the same current decreasing effect can be obtained regardless of the number of layers. 
     In addition, it is possible to use two circuit boards each of which is separately equipped with the radio circuit  6  and the control circuit  7 , respectively, as well as one circuit board commonly equipped with both radio circuit  6  and the control circuit  7  thereon. In each case, the same current decreasing effect can be obtained. 
     Embodiment 6 
     FIG. 14 shows a perspective view which illustrates a mobile telecommunication apparatus according to a sixth embodiment. FIG. 15 shows a front view of a printed circuit board  5  equipped in the mobile telecommunication apparatus of the sixth embodiment of the present invention. In FIG. 14, the mobile telecommunication apparatus include a slit  35  which is constructed on the printed circuit board  5  between the radio circuit  6  and the control circuit  7  by etching a copper foil pattern layer. 
     The construction of the present embodiment makes it easier to define the slit  35  on the printed circuit board  5  between the radio circuit  6  and the control circuit  7 , and has advantages such as a large strength, compared to the machining process that defines the slot as shown above. The other construction details are the same as those of the first embodiment, thus the detailed explanation thereof is omitted. 
     In the same way as explained in the first embodiment, the current longitudinally flowing on the earth conductor  12  of the printed circuit board  5  is prevented by the slit  20  which is constructed by etching processing of the copper foil pattern layer. Therefore, the current path along the slot  20  gets longer and the current flowing through the path along the slot  20  is more attenuated. Also, the current longitudinally flowing along the earth conductor  14  of the printed circuit board  5  is suppressed because of the relatively narrow width of the earth conductor  14 . 
     Thus, the parallel plain board mode generated between the control circuit  7  and the battery  15  is suppressed, and the current around the control circuit  7  is reduced. That is, the current amplitude which distributes along the control circuit  7  is reduced. 
     Furthermore, an effect similar to that obtained with the straight slot can also be obtained with any other slit shape such as a curved slit. 
     In addition, an effect similar to that obtained with the monopole antenna is also obtained for any type of antennas. 
     Also, the printed circuit board  5  can be a multi-layered circuit board which includes a single surface circuit board or a double surface circuit board, and the same current decreasing effect can be obtained regardless of the number of layers. 
     In addition, it is possible to use two circuit boards each of which is separately equipped with the radio circuit  6  and the control circuit  7 , respectively, as well as one circuit board commonly equipped with both radio circuit  6  and the control circuit  7  thereon. In each case, the same current decreasing effect can be obtained. 
     Embodiment 7 
     FIG. 16 shows locational relationship between a printed circuit board  5  and a battery  15  according to a seventh embodiment. In FIG. 16, the printed circuit board  5  is constructed with copper foil pattern layers  26   a  and  26   b , and a dielectric layer  27 . On the copper foil pattern layers  26   a , the earth conductors  12   a  and  13   a  form a slot  35  where narrow portion  14  connects the earth conductors  12   a  and  13   a . Alternatively, on the copper foil pattern layers  26   b , the earth conductors  12   b  and  13   b  form a slot  36  which separates the earth conductors  12   b  and  13   b  without forming the narrow portion  14 . 
     In addition, in FIG. 16, the earth conductor  12   a  on the copper foil pattern layer  26   a  and the earth conductor  12   b  on the copper foil pattern layer  26   b  are connected via through-hole plating  28   a . Similarly, the earth conductor  13   a  on the copper foil pattern layer  26   a  and the earth conductor  13   b  on the copper foil pattern layer  26   b  are connected via through-hole plating  28   b.    
     The slit  35  is formed on the opposite surface of the printed circuit board  5  from the battery  15 . The slit  35  is formed by etching a copper foil pattern layer between the radio circuit  6  and the control circuit  7 . 
     The slit  36  is formed on the surface of the printed circuit board  5  facing the battery  15  and separates the earth conductor  12   a  from the earth conductor  13   a.    
     The surface of the printed circuit board  5  facing the battery  15  generates less parallel board mode because the earth conductor  12   b  and an earth conductor  13   b  are separated. Alternatively, on the surface of the printed circuit board  5  opposite to the battery  15 , the current flowing longitudinally on a printed circuit board  5  is suppressed, and the parallel board mode is not generated because it is not facing the battery. Therefore, the parallel board mode is suppressed between the battery  15  and the control circuit  7 , and the current around the control circuit  7  on a printed circuit board  5  can be further reduced. 
     Furthermore, an effect similar to that obtained with the straight slot can be obtained with any other slit shape such as a curved slit. 
     In addition, an effect similar to that obtained with the monopole antenna is obtained with any type of antennas. 
     Also, the printed circuit board  5  can be a multi-layered circuit board which includes a single surface circuit board or a double surface circuit board, and the same current decreasing effect can be obtained regardless of the number of layers. 
     In addition, it is possible to use two circuit boards each of which is separately equipped with the radio circuit  6  and the control circuit  7 , respectively, as well as one circuit board commonly equipped with both radio circuit  6  and the control circuit  7  thereon. In each case, the same current decreasing effect can be obtained. 
     Embodiment 8 
     FIG. 17 shows the locational relationship between a printed circuit board  5  and the battery  15  according to an eighth embodiment. In FIG. 17, the printed circuit board  5  is constructed with four layers. They are a first copper foil pattern layer  26   a , a second copper foil pattern layer  26   b , a third copper foil pattern layer  26   c , and fourth copper foil pattern layer  26   d , respectively, which are arranged in the order of farthest from the battery  15 . The dielectric layers  27   a ,  27   b , and  27   c  are sandwiched by the first copper foil pattern layer  26   a , the second copper foil pattern layer  26   b , the third copper foil pattern layer  26   c , and the fourth copper foil pattern layer  26   d , respectively. A copper foil pattern  37  is arranged on the earth conductor  12   b  on the second copper foil pattern layer  26   b , and a copper foil pattern  38  is arranged on the earth conductor  13   d  on the fourth copper foil pattern layer  26   d . The copper foil pattern  37  and the copper foil pattern  38  are connected by the through-hole plating  28  through the dielectric layer  27   b , the third copper foil pattern layer  26   c  and the dielectric layer  27   c . Then the earth conductor  12   b  and the earth conductor  13   d  are connected electrically. The slits  39   a ,  39   b ,  39   c  and  39   d  separate the earth conductor  12   a˜d  from the earth conductor  13   a˜d , respectively, on the copper foil pattern layers  26   a ,  26   b ,  26   c  and  26   d , respectively. 
     FIG. 17 shows a connection example between the earth conductors  12   b  on the second copper foil pattern layer  26   b  and the earth conductors  13   d  on the fourth copper foil pattern layer  26   d . The inter-layer connection copper foil pattern  37  is formed on the second copper foil pattern layer  26   b , and the inter-layer connection copper foil pattern  38  for is formed on the fourth copper foil pattern layer  26   d . However, if the earth conductors are connected with the other copper foil pattern layers, any inter-layer connection copper foil patterns can be arranged on any earth conductors unless the inter-layer connection copper foil pattern  37  and the inter-layer connection copper foil pattern  38  are not arranged on the same layer. 
     The earth conductor  12  of the radio circuit  6  or the earth conductor  13  of the control circuit are also connected via the through-hole plating  28 , but they are not illustrated from the view point of the simple figure construction. 
     The earth conductors on the second first copper foil pattern layer  26   b  and the third copper foil pattern layer  26   c  are separated by the slits  39   b  and  39   c , respectively, which separate the current flowing through the radio circuit  6  and the control circuit  7 . 
     At the first copper foil pattern layer  26   a  and the fourth copper foil pattern layer  26   d , that is, at the surface layers of the printed circuit board  5 , the parallel board mode is greatly reduced, because the earth conductors  12   a,d  and the earth conductors  13   a,d  are separated via the slits  39   a  and  39   d , respectively. 
     Therefore, the parallel board mode is suppressed between the battery  15  and the control circuit  7 , and the current around the control circuit  7  on a printed circuit board  5  can be further reduced. 
     In FIG. 17, the current flowing longitudinally on the printed circuit board  5  can be still further suppressed even in the second copper foil pattern layer  26   b  and the third copper foil pattern layer  26   c  which are inner surface layer of the printed circuit board  5 . This is because the earth conductors  12   b,c  and the earth conductors  13   b,c  are separated via the slits  39   b  and  39   c , respectively. 
     Furthermore, an effect similar to that obtained with the straight slot can also be obtained with any other slit shapes such as a curved slit. 
     In addition, an effect similar to that obtained with the monopole antenna is obtained for any types of antennas. 
     Also, the printed circuit board  5  can be a multi-layered circuit board which includes a single surface circuit board or a double surface circuit board, and the same current decreasing effect can be obtained regardless of the number of layers. 
     In addition, it is possible to use two circuit boards each of which is separately equipped with the radio circuit  6  and the control circuit  7 , respectively, as well as one circuit board commonly equipped with both radio circuit  6  and the control circuit  7  thereon. In each case, the same current decreasing effect can be obtained. 
     In case of the two circuit board construction such as shown in FIG. 3, the earth conductor  12  on the first printed circuit board and the earth conductor  13  on the second printed circuit board are connected to each other via a through-hole. 
     As described above, according to the eighth embodiment of the present invention, the current can be reduced around the control circuit  7  by forming the slits  39   a ,  39   b ,  39   c  and  39   d  between the earth conductors  12   a,b,c  and  d  and the earth conductors  13   a,b,c  and  d , respectively. 
     Since the current around a control circuit portion  7  is reduced, the influence for audio circuit in the control circuit  7  can be lowered, and audio noises can be reduced. 
     Since the currents flowing on the earth conductors  13   a,b,c  and  d  of the control circuit on the printed circuit board  5  are reduced, the inverted-phase current acting against the antenna current is decreased. Therefore, the horizontal gain for the body of the mobile telecommunication apparatus is improved, an improved radiation pattern is obtained, and the transmission/reception range thereby increased. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations arc not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included in the scope of the following claims.