Abstract:
A Planar Inverted-F Antenna (PIFA) comprising a radiating element, a ground plane located below the radiating element; a through hole located at a position corresponding to the radiating element, a power feeding connector pin at a position corresponding to the radiating element; a through hole at a position corresponding to the radiating element; a conductive shorting post (pin) located at a position corresponding to the radiating element; a right side vertical plane formed along the edge of the radiating element; a left side vertical plane formed along the other edge of the radiating element; a lower horizontal plane formed by bending the left side vertical plane; a slot on the radiating element; and a dielectric block located in the area between the lower horizontal plane and the ground.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to Planar Inverted-F Antenna (PIFA) and, in particular, to a method of designing a single and multi-band PIFA with a single feed. 
     2. Description of the Related Art 
     The cellular communication industry has experienced an enormous growth in recent years. Of late there has been an increasing emphasis on internal antennas for cellular handsets instead of a conventional external wire antenna. The conventional external wire antenna on a cellular handset exhibits an Omni directional radiation pattern in the azimuth plane. This results in a portion of transmitted power being lost by absorption into the user&#39;s head and consequently leads to a higher value of Specific Absorption Rate (SAR). Internal antennas have several advantageous features such as being less prone for external damage, a reduction in overall size of the handset with optimization, easy portability, and potential for low SAR characteristics. The concept of internal antenna stems from the avoidance of protruding external radiating element by the integration of the antenna into the handset. The printed circuit board of the cellular handset serves as the ground plane of the internal antenna, and also acts to shield RF energy from user&#39;s head. This shielding/blockage effect reduces the power radiated in the direction of the user&#39;s head resulting in an improvement in the front to back (F/B) ratio of the radiation pattern of the internal antenna and lower value of SAR. Among the various choices for cellular internal antennas, PIFA appears to have great promise. The PIFA is characterized by many distinguishing properties such as being relatively lightweight, ease of adaptation and integration into the phone chassis, moderate range of bandwidth, Omni directional radiation patterns in orthogonal principal planes for vertical polarization, versatility for optimization, and multiple potential approaches for size reduction. A possible placement for PIFA inside a typical cellular handset to function as an internal antenna is shown in FIG.  10 . The PIFA also finds useful applications in diversity schemes. Its sensitivity to both the vertical and horizontal polarization is of immense practical importance in mobile cellular communication applications because the antenna orientation is not fixed. All these features render the PIFA to be a good choice as an internal antenna for mobile cellular handsets. Despite all of the desirable features of a PIFA, the PIFA has the limitation of a rather large physical size for practical application. A conventional PIFA should have the semi-perimeter of its radiating element (sum of the length and the width) equal to ¼ of a wavelength at the desired frequency. One-quarter of a wavelength at the center of AMPS frequency band (824-894 MHz) is 87.31 mm while the corresponding value at the center of GSM frequency band (880-960 MHz) is 81.52 mm. With the rapidly advancing size miniaturization of the cellular handset, the space requirement of a conventional PIFA is a severe limitation for practical application. Thus, there is a need for an efficient design technique to reduce the size of the PIFA, in order to realize a practical utility of the PIFA for cellular frequency bands. 
     Rapid expansion of the cellular communication industry in the recent past has created a need for multi-frequency band operation cellular handsets to meet the ever-increasing subscriber demand. In a typical multi-frequency band cellular handset with a single Duplexer, a multi-frequency band antenna with a single feed is the most viable option. Few attempts have been made in the past to design multi-frequency band PIFA with a single feed due to the complexity of design and difficulty in achieving acceptable bandwidths for the resonant bands desired. Multi-band PIFA designs have been realized in the past by using a separate feed path for each band. There is a great concern for a multi-band PIFA design with multiple feed paths having its performance compromised due to the mutual coupling and poor isolation of the various resonant bands. Therefore, the multi-band PIFA with multiple feed paths has not been a logical choice for practical applications in multi-frequency band cellular operations. Therefore, the design of single feed multi-band PIFA has been a topic of specific emphasis and special relevance to cellular communication. 
     A typical placement of a PIFA placed inside the housing of a typical cellular handset to function as an internal antenna is illustrated in FIG.  10 . FIG. 10 is a schematic cut-away side view of a typical cellular handset  40  with an internal antenna  42 . Cellular handset  40  includes a housing  41  in which antenna  42  and other accessories are enclosed. Among other things, the accessories of a cellular handset include a speaker  43 , display  44 , keypad  45 , microphone  46 , battery  47  and a printed circuit board  48  containing various electronic cards. Speaker  43  and microphone  46  define a user direction. When the cellular handset is in use with the keypad  45  pointing towards user&#39;s head, the speaker  43  is placed in the vicinity of user&#39;s ear and the microphone  46  is placed in the close proximity of the user&#39;s mouth. In FIG. 10, the internal antenna  42  is placed directly over the printed circuit board  48  implying that the printed circuit board  48  also serves as a ground plane for the antenna  42 . The internal antenna may also have a separate ground plane. In such a case, the ground plane of the internal antenna  42  is placed over the printed circuit board  48 . The radiating element of the internal antenna  42  is oriented in a direction away from user&#39;s head. The printed circuit board  48  which is located in the region between the internal antenna  42  and the user&#39;s head, blocks a significant amount of the RF field radiated by the antenna  42  in the direction of the user&#39;s head. Such a blockage effect offered by the printed circuit board  48  results in a dip or null in the radiation pattern of the antenna over an angular sector comprising the direction of the user&#39;s head also. Consequently, the amount of RF power of the internal antenna  42  transmitted in the direction of the user&#39;s head is considerably reduced resulting in low value of specific absorption rate (SAR). 
     A conventional prior art single band PIFA assembly is illustrated in FIGS. 11A and 11B. The PIFA  110  shown in FIG.  11 A and FIG. 11B consists of radiating element  101 , ground plane  102 , connector feed pin  104   a , and conductive post or pin  107 . A power feed hole  103  is located corresponding to the radiating element  101 . Connector feed pin  104   a  serves as a feed path for radio frequency (RF) power to the radiating element  101 . The connector feed pin  104   a  is inserted through the feed hole  103  from the bottom surface of the ground plane  102 . The connector feed pin  104   a  is electrically insulated from the ground plane  102  where the pin passes through the hole in the ground plane  102 . The connector feed pin  104   a  is electrically connected to the radiating element  101  at  105   a  with solder. The body of the feed connector  104   b  is electrically connected to the ground plane at  105   b  with solder. The connector feed pin  104   a  is electrically insulated from the body of the feed connector  104   b . A through hole  106  is located corresponding to the radiating element  101 , and a conductive post or pin  107  is inserted through the hole  106 . The conductive post  107  serves as a short circuit between the radiating element  101  and the ground plane  102 . The conductive post  107  is electrically connected to the radiating element  101  at  108   a  with solder. The conductive post  107  is also electrically connected to the ground plane  102  at  108   b  with solder. The resonant frequency of the PIFA  110  is determined by the length (L) and width (W) of the radiating element  101  and is slightly affected by the locations of the feed pin  104   a  and the shorting pin  107 . The impedance match of the PIFA  110  is achieved by the adjusting of the diameter of the connector feed pin  104   a , by adjusting the diameter of the conductive shorting post  107 , and by adjusting the separation distance between the connector feed pin  104   a  and the conductive shorting post  107 . The fundamental limitation of the configuration of the PIFA  110  described in FIG.  11 A and FIG. 11B is the requirement of relatively large dimensions of length (L) and width (W) of the radiating element  101  to achieve resonance in the desired cellular frequency bands (AMPS/GSM). This configuration is limited to only single operating frequency band applications. 
     The prior art techniques to reduce the physical size of the PIFA, while maintaining the resonance in the desired frequency bands include capacitive loading and dielectric loading. The dielectric loading increases the weight and cost of the PIFA while the capacitive loading in the prior art increases the mechanical complexity of the design, thus making it difficult and more expensive to manufacture. The details of these techniques are described below and are accompanied with illustrations. The elements of the PIFA configured with the capacitive loading and dielectric loading techniques which are similar to that of the conventional PIFA  110 , will have the same reference numbers as in FIG.  11 A and FIG.  11 B. Therefore, additional redundant reference explanations have been omitted. 
     A prior art PIFA  120  with conventional capacitive loading is illustrated in FIGS. 12A and 12B. Plate  109  is placed parallel to the ground plane  102  and functions as a capacitive loading element for the radiating element  101 . Plate  109  is separated from the ground plane  102  by a specific distance. The structural configuration of PIFA  120  with capacitive loading element as illustrated in FIG.  12 A and FIG. 12B increases complexity and adds several steps to the manufacturing process. This results in an increased cost of this PIFA design. 
     A prior art PIFA  130  with conventional dielectric loading is illustrated in FIG.  13 A and FIG.  13 B. The entire area between the radiating element  101  and the ground plane  102  is filled with a block of dielectric material  110  of a specified dielectric constant. The introduction of the block of dielectric material into the antenna increases the weight and cost of the PIFA. The block of dielectric material  110  in the entire area of the PIFA also increases the dielectric loss and hence causing lower RF energy radiation efficiency. 
     A description of some prior art configurations of multi-band PIFA with multiple feeds and single feed is as follows. A prior art multi-band PIFA  140  with a separate feed for each band is illustrated in FIG. 14A, FIG. 14 b  and FIG.  14 C. This configuration is a modification of the single band conventional PIFA  110  explained in FIG.  11 A and FIG.  11 B. As can be seen in FIGS. 14A,  14 B and  14 C, the multi-band PIFA  140  consists of two radiating elements  201   a  and  201   b  resonating at two separate frequency bands. The radiating elements  201   a  and  201   b  are positioned above a common ground plane  202 . A narrow L-shaped slot  203  offers a physical division and electrically separates the two radiating elements  201   a  and  201   b . A hole  204  is located corresponding to the radiating element  201   a . A connector feed pin  205   a , used for feeding radio frequency (RF) power to the radiating element  201   a , is inserted through hole  204  from the bottom surface of the ground plane  202 . The connector feed pin  205   a  is electrically insulated from the ground plane  202  where the pin passes through the hole in the ground plane  202 . The connector feed pin  205   a  is electrically connected to the radiating element  201   a  at  206   a  with solder. The body of the feed connector  205   b  is connected to the ground plane at  206   b  with solder. The connector feed pin  205   a  is electrically insulated from the body of the feed connector  205   b . A through hole  207  is located corresponding to the radiating element  201   a . A conductive post or pin  208  which functions as a short circuit between the radiating element  201   a  and the ground plane  202  is inserted through the hole  207 . The conductive post  208  is electrically connected to the radiating element  201   a  at  209   a  with solder. The conductive post  208  is connected to the ground plane  202  at  209   b  with solder. The radiating element  201   a  with relatively larger dimensions of length (L 1 ) and width (W 1 ) resonates at the lower frequency band of the multi-band operation. 
     The impedance match of the radiating element  201   a  is determined by the diameter of the connector feed pin  205   a , the diameter of the conductive shorting post  208  and the distance of separation between the connector feed pin  205   a  and the conductive shorting post  208 . The radiating element  201   b  with relatively smaller dimensions of length (L 2 ) and width (W 2 ) resonates at the higher frequency band of multi-band operation. A power feed hole  210  is located corresponding to the radiating element  201   b . A connector feed pin  211   a , used to feed radio frequency (RF) power to the radiating element  201   b , is inserted through the feed hole  210  from the bottom surface of the ground plane  202 . The connector feed pin  211   a  is electrically insulated from the ground plane  202  where the feed pin passes through the hole in the ground plane  202 . The connector feed pin  211   a  is electrically connected to the radiating element  201   b  at  212   a  with solder. The body of the feed connector  211   b  is connected to the ground plane  202  at  212   b  with solder. The connector feed pin  211   a  is electrically insulated from the body of the feed connector  211   b . A through hole  213  is located corresponding to the radiating element  201   b . A conductive post or pin  214 , which creates as a short circuit between the radiating element  201   b , and the ground plane  202  is inserted through the hole  213 . The conductive post  214  is electrically connected to the radiating element  201   b  at  215   a  with solder. The conductive post  214  is soldered to the ground plane  202  at  215   b . The impedance match of the radiating element  201   b  is determined by the diameter of the connector feed pin  211   a , the diameter of the conductive shorting post  214  and the distance of separation between the connector feed pin  211   a  and the conductive shorting post  214 . 
     The configuration of multi-band PIFA  140  illustrated in FIG.  14 A and FIG. 14B has several disadvantages. Such a configuration of the PIFA can be used only in a multi-band cellular handset with two Duplexers. However, the majority of currently manufactured cellular handsets have only one Duplexer. Adequate isolation between the two frequency bands requires a larger separation between the radiating elements  201   a  and  201   b  necessitating larger width of the L-shaped slot  203 . The increased width of the L-shaped slot without increase of the overall dimensions of the radiating elements  201   a  and  201   b  reduces the bandwidth of the PIFA. Any change in the separation between the two resonant frequency bands involves the change of linear dimensions of the radiating elements  201   a  and  201   b.    
     Z. D. Liu, P. S. Hall and D. Wake, “Dual Frequency Planar Inverted-F Antenna”, IEEE Trans. Antennas and Propagation, Vol. AP-45, No. 10, pp. 1451-1548, October 1997 (hereinafter referred to as Liu et al.) describes a multi-band PIFA with separate feeds with structural configuration similar to the one illustrated in FIG. 14A, FIG.  14 B and FIG. 14 c . P. Kabacik and A. A. Kuchaski, “Optimising the Radiation Pattern of Dual, Frequency Inverted-F Planar Antennas”, JINA Conference, pp. 655-658, 1998 (hereinafter referred to as Kabacik et al.) also describes a multi-band PIFA with separate feeds with similar configuration to the one illustrated in FIG. 14A, FIG.  14 B and FIG.  14 C. Instead of an L-shaped slot  203  separating the two radiating elements as in FIGS. 14A and 14B, a U-shaped slot has been proposed by Kabacik et al. 
     A prior art multi-band PIFA  150  with a single feed is illustrated in FIG.  15 A and FIG.  15 B. The multi-band PIFA  150  consists of a radiating element  301  and a ground plane  302 . An L-shaped slot  303  on the radiating element  301  creates a quasiphysical partitioning of the radiating element  301 . The segment on the radiating element  301  with dimensions of length (L 1 ) and width (W 1 ) resonates at the lower frequency band of the multi-band operation. The segment on the radiating element  301  with dimensions of length (L 2 ) and width (W 2 ) resonates at the upper frequency band of the multi-band operation. A power feed hole  304  is located corresponding to the radiating element  301 . A connector feed pin  305   a , used for feeding radio frequency (RF) power to the radiating element  301 , is inserted through the feed hole  304  from the bottom surface of the ground plane  302 . The connector feed pin  305   a  is electrically insulated from the ground plane  302  where the feed pin passes through the hole in the ground plane  302 . The connector feed pin  305   a  is electrically connected to the radiating element  301  with solder at  306   a . The body of the feed connector  305   b  is connected to the ground plane  302  at  306   b  with solder. The connector feed pin  305   a  is electrically insulated from the body of feed connector  305   b . A through hole  307  is located corresponding to the radiating element  301 . A conductive post or pin  308  which functions as a short circuit between the radiating element  301  and the ground plane  302  is inserted through the hole  307 . The conductive post  308  is connected to the radiating element  301  at  309   a  with solder. The conductive post  308  is also connected to the ground plane  302  at  309   b  with solder. The multi-frequency band impedance match of the radiating element  301  is determined by the diameter of the connector feed pin  305   a , the diameter of the conductive shorting post  308  and the separation distance between the connector feed pin  305   a  and the conductive shorting post  308 . The main disadvantage of the configuration of the multi-band PIFA  150  illustrated in FIG.  15 A and FIG. 15B is the lack of simple means of adjusting the separation of the lower and upper resonant frequency bands. The change in the separation of the resonant frequency bands requires the repositioning of the slot  303 . Liu et al. describes a configuration of a single feed multi-band PIFA, which is similar to the one described in FIG.  15 A and FIG.  15 B. In the single feed multi-band PIFA configuration of Liu et al., the concept of dielectric loading illustrated in FIG.  13 A and FIG. 13B has also been invoked. 
     SUMMARY OF THE INVENTION 
     In the first embodiment of the invention, the single feed multi-band PIFA is characterized by a radiating element located above the ground plane, a shorting pin or post along the centerline of the radiating element adjacent to the power feeding connector pin, a vertical loading plate on the radiating edge adjacent to the power feeding connector pin, a horizontal loading plate on the other radiating edge adjacent to the shorting post, and a block of dielectric material of a specific dielectric constant filling the area between the horizontal loading plate and the ground plane. In a second embodiment of the invention, PIFA is essentially the same as in the first embodiment except that in the second embodiment, a slot loading technique to adjust the resonant frequency of desired bands is described. A third embodiment of the invention is in the design of a single band PIFA having reduced dimensions of the radiating element including the concepts of slot loading, modified capacitive loading and partial dielectric loading combined therein. 
     One of the principal objects of the invention is to circumvent the use of separate feeds for the realization of multi-band operation of a PIFA. 
     A further object of the invention is to provide an efficient design method to achieve the multi-band operation of a PIFA using only a single feed path. 
     Still another object of the invention is to provide a single feed multi-band PIFA which is devoid of currently imposed physical partition of the original structure of a single band PIFA. 
     Still another object of the invention is to provide a design of a single feed multi-band PIFA which has the merit of relative ease of adjusting the separation between the resonant bands without necessitating a dimensional change of the radiating element. 
     Still another object of the invention is to provide a single feed multi-band PIFA configuration having the desirable features of configuration, simplicity, compact size, cost-effectiveness to manufacture and improved manufacturability. 
     Still another object of the invention is to provide a compact single band PIFA. 
     Still another object of the invention is to provide a design of the type described above which involves a combination of a modified prior art capacitive loading technique, a technique of partial dielectric loading and a technique of slot loading. 
     These and other objects will be apparent to those skilled in the art. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1A illustrates a top view of the design configuration of a single feed multi-band PIFA according to the first embodiment of the present invention; 
     FIG. 1B is a sectional view taken along the line  1 B— 1 B of FIG. 1A; 
     FIG. 1C is a sectional view taken along the line  1 C— 1 C of FIG. 1A; 
     FIG. 2 is a Smith Chart depicting the impedance variation of the multi-band PIFA of FIGS. 1A-1C; 
     FIG.  3 . is a frequency response that depicts the characteristics of the VSWR of the multi-band PIFA of FIGS. 1A-1C; 
     FIG. 4A illustrates a top view of the design configuration of a single feed multi-band PIFA according to the second embodiment of the present invention; 
     FIG. 4B is a sectional view taken along the line  4 B— 4 B of FIG. 4A; 
     FIG. 4C is a sectional view taken along the line  4 C— 4 C of FIG. 4A; 
     FIG. 5 is a Smith Chart depicting the impedance variation of the multi-band PIFA of FIGS. 4A-4C; 
     FIG. 6 is a frequency response that depicts the characteristics of the VSWR of the multi-band PIFA of FIGS. 4A-4C; 
     FIG. 7A illustrates a top view of the design configuration of a single band PIFA according to the third embodiment of the present invention; 
     FIG. 7B is a sectional view taken along the line  7 B— 7 B of FIG. 7A; 
     FIG. 7C is a sectional view taken along the line  7 C— 7 C of FIG. 7A; 
     FIG. 8 is a Smith Chart depicting the impedance variation of the single band PIFA of FIGS. 7A-7C; 
     FIG. 9 is a frequency response that depicts the characteristics of the VSWR of the single band PIFA of FIGS. 7A-7C; 
     FIG. 10 depicts the typical placement of an internal antenna in a cellular handset; 
     FIG. 11A is a top view of a prior art single band PIFA; 
     FIG. 11B is a sectional view taken along the line  11 B— 11 B of FIG. 11A; 
     FIG. 12A is a top view of a prior art single band PIFA with capacitive loading element; 
     FIG. 12B is a sectional view taken along the line  12 B— 12 B of FIG. 12A; 
     FIG. 13A is a top view of a prior art single band PIFA with dielectric loading; 
     FIG. 13B is a sectional view taken along the line  13 B— 13 B of FIG. 13A; 
     FIG. 14A is a top view of a prior art multi-band PIFA with separate feeds; 
     FIG. 14B is a sectional view taken along the line  14 B— 14 B of FIG. 14A; 
     FIG. 14C is a sectional view taken along the line  14 C— 14 C of FIG. 14A; 
     FIG. 15A is a top view of a prior art multi-band PIFA with single feed; and 
     FIG. 15B a sectional view taken along the line  15 B— 15 B of FIG.  15 A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention are now explained while referring to the drawings. 
     In the accompanying text describing the single feed multi-band PIFA  10  covered under the first embodiment of this invention, refer to the FIGS. 1A,  1 B and  1 C for illustrations. The PIFA  10  includes a radiating element  11 a that is located above the ground plane  12 . A power feed hole  13  is located corresponding to the radiating element  11   a . A connector feed pin  14   a , serves as an electrical path for radio frequency (RF) power to the radiating element  11   a  is inserted through the feed hole  13  from the bottom surface of the ground plane  12 . The connector feed pin  14   a  is electrically insulated from the ground plane  12  where the feed pin passes through the hole in the ground plane  12 . The connector feed pin  14   a  is electrically connected to the radiating element  11   a at  15   a  with solder. The body of the feed connector  14   b  is electrically connected to the ground plane  12  at  15   b  with solder. The connector feed pin  14   a  is electrically insulated from the body of the feed connector  14   b . A through hole  16  is located corresponding to the radiating element  11   a . A conductive post or pin  17 , which serves as a short circuit between the radiating element  11   a  and ground plane  12 , is inserted through the hole  16 . The conductive post  17  is electrically connected to the radiating element  11   a  at  18   a  with solder. The conductive post  17  is also electrically connected to the ground plane  12  at  18   b  with solder. The radiating element  11   a  is bent 90° at  19  along the edge  19   a  to form a right side vertical plane  11   b . The lower edge of the vertical plane  11   b  is at a specific distance D 3  above the ground plane  12 . The vertical plane  11   b  serves as a capacitive loading plate for the radiating element  11   a . The radiating element  11   a  is bent 90° at  20  along the edge  20   a  to form a left side vertical plane  11   c . The vertical plane  11   c  is again bent 90° at  21  to form a lower horizontal plane  11   d . The horizontal plane  11   d  of width D 7  is at a specific distance D 5  above the ground plane. The horizontal plane  11   d  serves a capacitive loading plate for the radiating element  11   a . A dielectric block  22  of pre-specified dielectric constant is located in the area between the horizontal plane  11   d  and the ground plane  12 . The plastic screws  23   a  and  23   b  hold the dielectric block  22  to the horizontal plane  11   d . The plastic screw nuts  24   a  and  24   b  hold the dielectric block  22  to the ground plane  12 . 
     The PIFA configuration illustrated in FIGS. 1A,  1 B and  1 C functions as multi-band antenna with a single feed. The dimensions of the radiating element  11   a , the right side vertical plane  11   b , the left side vertical plane  11   c , the lower horizontal plane  11   d , the dielectric constant of the block  22  and the location of the shorting pin  17  are the prime parameters that control the resonant frequencies of lower and upper bands. The bandwidths at the lower and upper resonant frequency bands of the multi-band PIFA  10  are determined by: the diameter of the connector feed pin  14   a , the location of the connector feed pin  14   a , the location of the shorting pin  17  and the diameter of the shorting pin  17 . A combination of the radiating element  11   a , the shorting pin  17 , the vertical plane  11   b , the vertical plane  11   c , the horizontal plane  11   d  and the dielectric block  22  results in multiple resonant frequencies of the PIFA  10 . The resonant frequencies are lower than the resonant frequency of the PIFA with only the radiating element  11   a  alone. The lowering of the resonant frequencies of the PIFA  10  is due to the capacitive loading offered by the right side vertical plane  11   b  and lower horizontal plane  11   d . Further reduction of the resonant frequency is due to the dielectric loading caused by the dielectric block  22  located in the area between the lower horizontal plane  11   d  and the ground plane  12 . 
     The results of the tests conducted on the single feed multi-band PIFA  10  illustrated in FIGS. 1A,  1 B and  1 C referred to as the first embodiment of this invention are shown in FIG.  2  and FIG.  3 . FIG. 2 is a Smith Chart of the single feed multi-band PIFA  10  resonating at AMPS (824-894 MHz) and PCS (1850-1990 MHz) bands. FIG. 3 illustrates the VSWR plot of the single feed multi-band PIFA  10  resonating at AMPS and PCS bands. The multi-band impedance match of PIFA  10  has been achieved without use of an external-matching network. The dimensions of the multi-band PIFA  10  are: Length(D 1 +D 7 )=41 mm. Width(D 2 )=31 mm and Height (D 5 +D 6 )=9.5 mm. The projected semi-perimeter of the multi-band PIFA  10  is 72 mm as compared to the semi-perimeter of 87.31 mm of a conventional single band PIFA  110  resonating in AMPS band only. 
     In the accompanying text describing the single feed multi-band PIFA  20  covered under the second embodiment of this invention, refer to FIGS. 4A,  4 B and  4 C for illustrations. The multi-band PIFA  20  illustrated in FIGS. 4A,  4 B and  4 C has an additional slot  25  on the radiating element  11   a . All the other elements of the multi-band PIFA  20  illustrated in FIGS. 4A,  4 B and  4 C are identical to the multi-band PIFA  10  illustrated in FIGS. 1A,  1 B and  1 C which has already been explained while covering the first embodiment of this invention. Further redundant explanation of the single feed multi-band PIFA  20  illustrated in FIGS. 4A,  4 B and  4 C will therefore be omitted. The slot  25  is positioned in between the left side vertical plane  11   c  and the shorting pin  17  and is located corresponding to a position on the radiating element  11   a  of the multi-band PIFA  20  as illustrated in FIGS. 4A,  4 B and  4 C. The choice of the location of the slot  25  illustrated in FIGS. 4A,  4 B and  4 C has been with a specific purpose to offer reactive loading effect to the radiating element  11   a  at the lower resonant band only. Hence, the size and position of the slot  25  will control the resonant frequency of only the lower band of the PIFA  20 . The presence of the slot  25  has no effect on the resonant frequency of the upper band of the PIFA  20 . The results of the tests conducted on the single feed multi-band PIFA  20  illustrated in FIGS. 4A,  4 B and  4 C referred to as the second embodiment of this invention are shown in FIG.  5  and FIG.  6 . FIG. 5 is a Smith Chart of the single feed multi-band PIFA  20  resonating at GSM (880-960 MHz) and DCS (1710-1880 MHz) bands. FIG. 6 illustrates the VSWR plot of the single feed multi-band PIFA  20  resonating at GSM and DCS bands. The multi-band impedance match of the PIFA  20  has been achieved without use of an external-matching network. The dimensions of the multi-band PIFA  20  are Length (D 1 +D 7 )=43.5 mm. Width (D 2 )=31 mm:and Height (D 5 +D 6 )=9 mm. The projected semi perimeter of the multi-band PIFA  20  is 74.5 mm as compared to the semi perimeter of 81.52 mm of a conventional single band PIFA  110  resonating in GSM band only. 
     In the accompanying text describing the miniaturized single band PIFA  30  covered under the third embodiment of this invention, refer to the FIGS. 7A,  7 B and  7 C for illustrations. The design concepts developed under the first and second embodiments of this invention are equally applicable to the design of miniaturized single band PIFA. The single band PIFA  30  illustrated in FIGS. 7A,  7 B and  7 c is similar to that of the single feed multi-band PIFA  20  illustrated in FIGS. 4A,  4 B and  4 C. However, the single band PIFA  30  illustrated in FIGS. 7A,  7 B and FIG. 7C does not have a right side vertical plane  11   b . All the other elements of the single band PIFA  30  illustrated in FIGS. 7A,  7 B and  7 C are identical to the multi-band PIFA  20  illustrated in FIGS. 4A,  4 B and  4 C which has already been explained. Therefore, the further description of the single band PIFA  30  illustrated in FIGS. 7A,  7 B and  7 C has been deleted to avoid the repetition. The results of the tests conducted on the single band PIFA  30  illustrated in FIGS. 7A,  7 B and  7 C referred to as the third embodiment of this invention are shown in FIG.  8  and FIG.  9 . FIG. 8 is a Smith Chart of the single band PIFA  30  resonating at GSM (880-960 MHz) band. FIG. 9 illustrates the VSWR plot of the single band PIFA  30  resonating at GSM band. The single band impedance match of the PIFA  30  has been obtained without use of an external-matching network. The dimensions of the single band PIFA  30  are: Length (D 1 +D 7 )=32 mm: Width (D 2 )=32 mm:Height (D 5 +D 6 )=9.0 mm. As can be seen from these dimensions of the PIFA  30 , the projected semi perimeter of the miniaturized single band PIFA  30  resonating in GSM band is 64 mm only compared to the corresponding value of 81.52 mm of a conventional GSM band PIFA. So the novel design proposed in this invention to achieve the miniaturization of the size of the PIFA in cellular frequency band has been demonstrated. 
     With reference to prior art FIGS. 11, A-B,  12 A-B,  13 A-B,  14 A-C and  15 A-B, it is seen that in all cases one edge of the radiating element of the PIFA is shorted to the ground plane element. Thus, inherently this shorted edge of the radiating element is a non-radiating edge. 
     However in the construction and arrangement of the present invention, and as shown in FIGS. 1A-C,  4 A-C, and  7 A-C, no edge of the radiating element is shorted, thus inherently all four edges of the radiating element are radiating edges. In addition, PIFAs constructed and arranged in accordance with the invention provide a radiating element as a geometric shape (for example a rectangle) that is symmetrically about a centerline of the radiating element, and the PIFA&#39;s shorting pin and single feed pin are spaced from each other and are located along this centerline. 
     FIGS. 1A-C show a single-feed, multi-band, PIFA in accordance with the invention wherein the radiating element is a continuous metal member having no slot therein, with the feed pin located adjacent to a first radiating edge of the radiating element, and with the shorting pin located on the opposite side of the feed pin. 
     FIGS. 4A-C show a single-feed, multi-band, PIFA in accordance with the invention wherein the radiating element contains a slot, with the feed pin located adjacent to a first radiating edge of the radiating element, with the shorting pin located on the opposite side of the feed pin, and with the radiating element including a slot that is located between the shorting pin and a radiating edge that is opposite to the first radiating edge, the slot being a generally linear slot having an open end that is locating on a third radiating edge, and the slot extending into the radiating element generally perpendicular to the centerline of the radiating element. 
     FIGS. 7A-C show a single-feed, single-band, PIFA in accordance with the invention wherein the radiating element contains a slot, with the shorting pin located adjacent to a first radiating edge of the radiating element, with the feed pin located on the opposite side of the shorting pin, and with the radiating element including a slot that is located between the feed pin and a radiating edge that is opposite to the first radiating edge, the slot being a generally linear slot having an open end that is locating on a third radiating edge, the slot extending into the radiating element generally perpendicular to the centerline of the radiating element. 
     Thus the novel design technique of single feed multi-band PIFA and single band PIFA of this invention has accomplished at least all of its stated objectives.