although the invention has been explained in relation to several preferred embodiments , the accompanying drawings and the following detailed descriptions are the preferred embodiment of the present invention . it is to be understood that the following disclosed descriptions will be examples of present invention , and will not limit the present invention into the drawings and the special embodiment . fig2 shows a schematic of a dual - mode co - existence system according to the embodiment of the present invention . the system uses two antennas , which are used for the transmission and reception of the ieee802 . 11b / g system and bluetooth system , and a switch 100 of the double - pole - three - throw configuration according to the present invention . according to the present invention , the antenna diversity switch collectively controls all the switching transistors to form the off or on state such that it can be used as a transmit / receive switch for dual - mode co - existence system and therefore it reduces the areas of the rf modules . now referring to the fig3 , it shows the circuit schematic of the antenna diversity switch 100 according to the embodiment of the present invention . the antenna diversity switch 100 comprises a first transmitting port 111 , a first antenna 121 ; a second transmitting port 112 ; a receiving port 130 ; a second antenna 122 ; a first control unit 141 , electrically connected between the first transmitting port 111 and the first antenna 121 ; a second control unit 142 , electrically connected between the first transmitting port 111 and a second antenna 122 ; a third control unit 143 , electrically connected between the second transmitting port 112 and the first antenna 121 ; a forth control unit 144 , electrically connected between the second transmitting port 112 and the second antenna 122 ; a fifth control unit 145 , electrically connected between the receiving port 130 and the first antenna 121 ; and a sixth control unit 146 , electrically connected between the receiving port 130 and the second antenna 122 . the first antenna 121 and the second antenna 122 can be the antennas of any type but preferably be the diversity antennas . in general , the actions of diversity antennas are classified into the predictive diversity and the true diversity . the predictive diversity uses two antennas located in different locations to receive the signal . it automatically selects the signal with higher intensity so that the antennas always receive the signal of higher intensity . the true diversity uses two receiving modules of the same performance , each connected to one antenna in different locations . the true diversity selects the baseband signal of higher intensity by the results of the comparator and switch circuits . the first transmitting port 111 and the second transmitting port 112 connected to the transmitting ports of an rf transceiver . as shown in fig3 , a first rf signal from the first transceiver of the dual - mode system can be fed to the first transmitting port 111 and then be radiated by the first antenna 121 selected by the first control unit 141 or be radiated by the second antenna 122 selected by the second control unit 142 . in the same way , a second rf signal from the second transceiver of the dual - mode system can be fed to the second transmitting port 112 and then be radiated by the first antenna 121 selected by the third control unit 143 or be t radiated by the second antenna 122 selected by the fourth control unit 144 . the first rf signal and the second rf signal are the signals processed by the rf transceiver , namely the first rf signal and the second rf signal are generated from the baseband signal up - converted by the rf module . the first rf signal and the second rf signal can be any microwave signals of different frequencies and systems , such as advanced mobile phone system ( amps ); code division multiple access ( cdma ); wideband code division multiple access ( wcdma ); global system for mobile communications ( gsm ); global positioning system ( gps ); personal handy - phone system ( phs ); industrial scientific and medical ( ism ) devices ; wireless local area networks ( wlan ) and bluetooth . in present invention , the first rf signal is preferably the rf signal of wlan of ieee802 . 11b / g standard and the second rf signal is preferably the rf signal of the bluetooth system . the receiver 130 is the receiving port of a rf transceiver . as shown in fig3 , a first rf signal from the first antenna 121 will enter the receiving port 130 of the rf transceiver selected by the fifth control unit 145 to be further processed . in the same way , a second rf signal from the second antenna 122 will enter the receiving port 130 of the rf transceiver selected by the sixth control unit 146 to be further processed . a power divider connected to the receiving port 130 ( not shown ) is used for dividing the power of the rf signal from the receiving port 130 and then the rf signal will be further processed in several rf front - end circuits . the first control unit 141 , the second control unit 142 , the third control unit 143 , the forth control unit 144 , the fifth control unit 145 and the sixth control unit 146 all use the field effect transistor as the switching component , where each source node and each drain node are connected to the adjacent circuits and each gate is connected to the control voltage to determine the on / off state of each transistor . the types of the above transistors can be implemented include : bipolar junction transistor ( bjt ), heterojunction bipolar transistor ( hbt ), high electronic mobility transistor ( hemt ), pseudomorphic hemt ( phemt ), complementary metal oxide semiconductor filed effect transistor ( cmos ) and laterally diffused metal oxide semiconductor filed effect transistor ( ldmos ). preferably , phemt is suitable for the gain stage and power stage in the microwave to millimeter wave range . semiconductor materials broadly applicable to the gain stage and power stage include : silicon , silicon - on - insulator ( soi ), silicon - germanium ( sige ), gallium arsenide ( gaas ), indium phosphide ( inp ) and silicon - germanium - carbon ( sige — c ). across the source and drain nodes of each transistor , an inductor is connected to increase the isolation of the antenna diversity switch 100 . fig4 shows the equivalent circuit schematic of the switching transistor 200 in each control unit according to the embodiment of the present invention . the resistor 210 and the capacitor 220 are the equivalent circuit of each transistor of the control unit and it is noted that different transistor will have different resistance and the capacitance . the inductor 230 is employed to neutralize the parasitic capacitance 220 to increase the isolation of the antenna diversity switch in the off state . the inductor and capacitor form a shunt resonant circuit , which has a bandstop response , resulting in high isolation at the shunt resonance frequency . the angular frequency of the bandstop response is where ω = 2πf , c off is the parasitic capacitance of the turned - off transistor . in the on state , the transistor is turned on and has a low turned - on resistance r on ( typically a few ω ) such that the signal is passes through the switch transistor to the load with little insertion loss . by controlling the voltage on the gate of the transistor , the transistor of each control unit can pass or block the signal . now refer to the fig3 for the description of the operating principle of the antenna diversity switch 100 of the present invention . since the antenna diversity switch 100 is used for transmitting and receiving two rf signals of different wireless communication systems , the antenna diversity switch 100 has four different operation modes . at the first operating mode , the antenna diversity switch 100 transmits two different rf signals . as the first control unit 141 is turned on ; the second control unit 142 is turned off ; the third control unit 143 is turned off ; the forth control unit 144 is turned on ; the fifth control unit 145 is turned off and the sixth control unit 146 is turned off , the first transmitting port 111 transmits the first rf signal to the first antenna 121 and the second transmitting port 112 transmits the second rf signal to the second antenna 122 . in addition , the first antenna 121 and the second antenna 122 have a diversity effect , so there is another operation condition as follows . as the first control unit 141 is turned off ; the second control unit 142 is turned on ; the third control unit 143 is turned on ; the forth control unit 144 is turned off ; the fifth control unit 145 is turned off and the sixth control unit 146 is turned off , the first transmitting port 111 transmits the first rf signal to the second antenna 122 and the second transmitting port 112 transmits the second rf signal to the first antenna 121 . it is noted that the above operating principle of the antenna diversity switch 100 transmits the two rf signals of the transceiver through two antennas 121 and 122 , respectively . hence the two signal paths of the antenna diversity switch 100 are not overlapped . fig5 shows the simulated insertion loss and return losses of the first transmitting port 111 and second transmitting port 112 of the antenna diversity switch at the first operating mode . fig6 shows the simulated isolation between each unit of the antenna diversity switch at the first operating mode . fig7 shows the simulated p 1db compression point of the first transmitting port 111 and second transmitting port 112 of the antenna diversity switch at the first operating mode . as shown in fig5 , the insertion loss is less than 0 . 68 db from 1 to 4 ghz . the return losses are greater than 20 db over a 600 mhz bandwidth centered at 2 . 4 ghz . as shown in fig6 , the isolation at 2 . 4 ghz between the first transmitting port 111 and the second transmitting port 112 is larger than 43 db , the isolation between the first transmitting port 111 and the receiving port 130 is larger than 43 db , and the isolation between the second transmitting port 112 and the receiving port 130 is larger than 43 db . as shown in fig7 , the simulated p 1db compression point of the first transmitting port 111 and second transmitting port 112 is 34 . 5 dbm . at the second operating mode , one system is in the transmission state and the other system is in the receiving state . as the first control unit 141 is turned on , the second control unit 142 is turned off , the third control unit 143 is turned off , the forth control unit 144 is turned off , fifth control unit 145 is turned off and the sixth control unit 146 is turned on , the first transmitting port 111 transmits the first rf signal from the first antenna 121 and the second antenna 122 receives the second rf signal to the receiving port 130 so as the second rf signal can feed the transceiver . in addition , since the first antenna 121 and the second antenna 122 are the diversity pair , there is another situation at the second operating mode as follows . as the first control unit 141 is turned off ; the second control unit 142 is turned on ; the third control unit 143 is turned off ; the forth control unit 144 is turned off ; the fifth control unit 145 is turned on and the sixth control unit 146 is turned off , the first transmitting port 111 transmits the first rf signal from the second antenna 122 and the first antenna 121 receives the second rf signal to the receiving port 130 so as the second rf signal can feed the transceiver . it is noted that in above operating principle the first transmitting port 111 transmits the first rf signal from the one of the diversity antennas and another diversity antenna receives the second rf signal to the receiving port 130 so as the second rf signal can feed the transceiver . due to the co - existence of receiving and transmitting , the antenna diversity 100 is in the state of the strong co - channel interference . the high isolation between switches reduces this co - channel interference . since the configuration of the antenna diversity 100 is symmetry , the operating principle of the third operating mode is similar to the second operating mode . as the first control unit 141 is turned off ; the second control unit 142 is turned off ; the third control unit 143 is turned off ; the forth control unit 144 is turned on , fifth control unit 145 is turned on and the sixth control unit 146 is turned off , the first antenna 121 receives the first rf signal to the receiving port 130 so as the first rf signal can feed the transceiver and the second transmitting port 112 transmits the second rf signal from the second antenna 122 . in addition , since the first antenna 121 and the second antenna 122 are the diversity pair , there is another situation at the third operating mode . as the first control unit 141 is turned off ; the second control unit 142 is turned off ; the third control unit 143 is turned on ; the forth control unit 144 is turned off , fifth control unit 145 is turned off and the sixth control unit 146 is turned on , the second antenna 122 receives the first rf signal to the receiving port 130 so as the first rf signal can feed the transceiver and the second transmitting port 112 transmits the second rf signal from the first antenna 121 . it is noted that in above operating principle the second transmitting port 112 transmits the first rf signal from the one of the diversity antennas and another diversity antenna receives the second rf signal to the receiving port 130 so as the second rf signal can feed the transceiver . due to the co - existence of receiving and transmitting , the antenna diversity 100 is also in the state of the strong co - channel interference . the high isolation between switches reduces this co - channel interference . fig8 shows the simulated insertion loss and return losses of the receiving port 130 of the antenna diversity switch at the second operating mode . fig9 shows the simulated insertion loss and return losses of the first transmitting port 111 and second transmitting port 112 of the antenna diversity switch at the third operating mode . fig1 shows the simulated isolation between each unit of the antenna diversity switch at the second and third operating mode . fig1 shows the simulated p 1db compression point of the receiving port 130 of the antenna diversity switch at the second operating mode . fig1 shows the simulated p 1db compression point of the receiving port 130 of the antenna diversity switch at the third operating mode . as shown in fig8 , from 1 to 4 ghz , the insertion loss from the receiving port 130 to the transmitting port is less than 0 . 67 db . at the center frequency of 2 . 4 ghz , the return loss of the receiving port is greater than 25 db and the return loss of the transmitting port is larger than 23 db . as shown in fig9 , from 1 to 4 ghz , the insertion loss from the receiving port 130 to the transmitting port is less than 0 . 76 db . at the center frequency of 2 . 4 ghz , the return loss of the receiving port is greater than 35 db and the return loss of the transmitting port is larger than 35 db . as shown in fig1 , the isolation between the first transmitting port 111 and the second transmitting port 112 is larger than 43 db , the isolation between the first transmitting port 111 and the receiving port 130 is larger than 43 db , and the isolation between the second transmitting port 112 and the receiving port 130 is larger than 43 db . as shown in fig1 , the simulated p 1db compression point of the receiving port 130 is 35 dbm . as shown in fig1 , the simulated p 1db compression point of the transmitting port is 35 dbm . at the fourth operating mode , the antenna diversity switch 100 receives two different rf signals . as the first control unit 141 is turned off ; the second control unit 142 is turned off ; the third control unit 143 is turned off ; the forth control unit 144 is turned off ; the fifth control unit 145 is turned on and the sixth control unit 146 is turned off , the first rf signal and the second rf signal are all received by the first antenna 121 and then propagate to the receiving port 130 . in addition , the first antenna 121 and the second antenna 122 are the diversity antennas , so there is another situation at the fourth operating mode . as the first control unit 141 is turned off ; the second control unit 142 is turned off ; the third control unit 143 is turned off ; the forth control unit 144 is turned off ; the fifth control unit 145 is turned off and the sixth control unit 146 is turned on , the first rf signal and the second rf signal are all received by the second antenna 122 and then propagate to the receiving port 130 . it is noted that in the above operating principle of the antenna diversity switch 100 , the two diversity antennas receive the two rf signals , which are then propagated to the receiving port 130 . fig1 shows the simulated insertion loss and return losses of the receiving port 130 of the antenna diversity switch at the fourth operating mode . fig1 shows the simulated isolation between each unit of the antenna diversity switch at the fourth operating mode and fig1 shows the simulated p 1db compression point of the receiving port 130 of the antenna diversity switch at the fourth operating mode . as shown in fig1 , the insertion loss from the receiving port to the transmitting port is less than 0 . 76 db from 1 to 4 ghz . the return loss of the receiving port 130 is larger than 25 db and the return loss of the transmitting port is larger than 23 db . as shown in fig1 , the isolation between the first transmitting port 111 and the second transmitting port 112 is larger than 43 db , the isolation between the first transmitting port 111 and the receiving port 130 is larger than 43 db , and the isolation between the second transmitting port 112 and the receiving port 130 is larger than 43 db . as shown in fig1 , the simulated p 1db compression point of the receiving port 130 is 29 dbm . although the invention has been explained in relation to its preferred embodiment , it is not used to limit the invention . it is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention as hereinafter claimed .