Abstract:
An object of the present invention is to provide an antenna switch circuit that effectively reduces signal leakages at a cross point even at higher operating frequencies and a high frequency module containing said antenna switch module. The antenna switch circuit comprises: a high frequency signal line to transmit a transmitting signal to be input to transmitting terminals to an antenna terminal and also to transmit a receiving signal to be input to the antenna terminal to receiving terminals; switches that are connected in the middle of the high frequency signal line between transmitting terminal and antenna terminal; switches that are connected in the middle of the high frequency signal line between receiving terminal and antenna terminal; and signal lines to transmit control signals for controlling turning on and off of the switches.

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese application JP 2004-271048 filed on Sep. 17, 2004, the content of which is hereby incorporated by reference into this application. 
     FIELD OF THE INVENTION 
     The present invention relates to an antenna switch circuit for switching the connection to a common antenna between a transmitter circuit and a receiver circuit, and a high frequency module containing said antenna switch circuit. 
     BACKGROUND OF THE INVENTION 
     As the circuits of a mobile phone are increasingly integrated, the thickness of a wiring substrate formed of layered dielectric plates becomes thinner. As a result, if a high frequency signal line is crossed with another signal line over a layer of the wiring substrate, both signal lines come close to each other at the cross point. 
     At the cross point where both signal lines come close to each other, a combined capacitance is formed by both wiring layers and an insulating material in between. Since the frequencies of the high frequency signals used for a mobile phone are in the GHz band, it is inevitable that the high frequency signals leak to other signal lines through this combined capacitance. The patent document 1 below discloses an example in which resistive elements are disposed immediately under and across the high frequency signal line so that other signal lines pass through the resistive elements, in order to reduce the leakage. 
     Patent document 1: JP-A No. 10-178305 
     SUMMARY OF THE INVENTION 
     In a mobile phone, a common antenna is used for transmission and reception and therefore an antenna switch circuit is provided to switch the connection to the antenna between a transmitting circuit and a receiving circuit. Particularly, in a multi-mode mobile phone supporting a plurality of standards, plural transmitting and receiving circuits are provided and the antenna switch circuit is formed such that the connection to the common antenna can be switched among the plurality of transmitting and receiving circuits. In such a case, many switching devices are used and high frequency signal lines to the antenna or those to receiving terminals cross with control signal lines that control the turning on and off of the switching devices, and cross points are formed there. 
     The antenna switch circuit is typically formed by an integrated circuit. As the integration of an integrated circuit is increased, the gap between these signal lines at a cross point becomes narrower. Since an interlayer insulating film is formed at the cross point, a capacitance is formed between the signal lines with the interlayer insulating film acting as a dielectric material. The higher the frequency, the more notable the effect of this capacitance. If transmitting high frequency signals leak through this combined capacitance, power efficiency will be reduced. If receiving high frequency signals leak, receiving sensitivity will be lowered. Moreover, signals that leaked at a cross point may further leak to the receiving signal lines via other cross points or other switch devices. 
     For the multi-mode mobile phone equipped with a battery and operates at high frequencies in GHz band, lower power consumption and higher sensitivity are required. In order to meat these requirements, a decrease in insertion loss between each of the transmitting and receiving circuits and the antenna and high Tx isolation, Rx isolation, and Tx, Rx isolation are required. 
     The conventional method of disposing resistive elements at a cross point can reduce the leakage, but capacitances are combined at the resistive elements across the cross point and consequently the resistance decreases equivalently at high frequencies and the effect of leakage reduction lowers. 
     Furthermore, the conventional method has a problem that the width of a resistive element formed at the cross point with a control signal line changes according to the width of a high frequency signal line. For example, when the sheet resistance is 100 Ω/□ and the width of the high frequency signal line is limited to 500 μm by allowable current, if the width of the resistive element is 10 μm, then the resistive element at the cross point is 10 μm wide, 500 μm long, and at 5 kΩ. When the width of the high frequency signal line is 5 μm, if the width of the resistive element is 10 μm, then the resistive element at the cross point is 10 μm wide, 5 μm long, and at 50 Ω. Thus, the resistance changes with the change in the effect of leakage reduction. Moreover, if the gap between signal lines at a cross point narrows, a high frequency signal line through which high-power transmitting signals flow may generate joule heat at the resistive element since the leaked signals flow through the resistive element. 
     An object of the present invention is therefore to provide an antenna switch circuit that effectively reduces the leakage of signals even if the operating frequency becomes higher, or to provide a high frequency module containing said antenna switch. 
     The antenna switch circuit of the present invention for achieving the above object comprises: a first signal line to transmit a transmitting signal to be input to a transmitting terminal to an antenna terminal and also to transmit receiving signal to be input to the antenna terminal to a receiving terminal; a first switch connected in the middle of the first signal line between the transmitting terminal and the antenna terminal; a second switch connected in the middle of the first signal line between the receiving terminal and the antenna terminal; a second signal line to transmit a first control signal that controls the turning on and off of said first switch; and a third signal line to transmit a second control signal that controls the turning on and off of said second switch, wherein at least either of said second and third signal lines crosses with the first signal line, two resistive elements are disposed across a cross point with said first signal line, and at least either of said second and third signal lines crossing with said first signal line is wired through said two resistive elements. 
     In the construction above, signals that leaked at the cross point is blocked by the two resistive elements and thereby the leakage is reduced. Also, since the resistive elements are not disposed immediately under the cross point, the leakage reducing effect will not be impaired. As a result, the leakage is effectively reduced and the requirements for reduced insertion loss and higher Tx, Rx isolation can be met. 
     A high frequency module of the present invention for achieving the above object comprises: a transmitting circuit that outputs a transmitting signal; a receiving circuit that inputs a receiving signal from an antenna terminal; and an antenna switch circuit that supplies an output signal from the transmitting circuit to the antenna terminal during transmission and supplies a receiving signal from the antenna terminal to the receiving circuit during reception, wherein the antenna switch circuit is said antenna switch circuit. Since the antenna switch circuit enables reduced insertion loss and high and reliable Tx, Rx isolation, thus making it possible to realize a high frequency module with high performance. 
     According to the present invention, current leakage is suppressed by the resistive elements which are disposed away from and across the cross point, not at the cross point, and thereby signal leakage can be effectively reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a schematic diagram for illustrating an embodiment of an antenna switch circuit according to the present invention; 
         FIG. 2  is a plan view of a cross point for illustrating its structure; 
         FIG. 3  is a sectional view of the cross point for illustrating its structure; 
         FIG. 4  is a circuit diagram showing an electrical equivalent circuit of the cross point; 
         FIG. 5  is a schematic diagram for illustrating an embodiment of a high frequency module according to the present invention; 
         FIG. 6  is a graph for illustrating the effect of the present invention on insertion loss; and 
         FIG. 7  is a graph for illustrating the effect of the present invention on Tx, Rx isolation. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the embodiments shown in the drawings, an antenna switch circuit according to the present invention or a high frequency module containing said antenna switch circuit will be described below. The same reference numbers in  FIGS. 1 to 4  denote the same or similar items, and therefore repeated descriptions of them will not be made. 
       FIG. 1  shows an embodiment of the antenna switch according to the present invention. In this figure,  9  and  10  denote switches (first switches) which connect transmitting terminals  1  and  2  to an antenna terminal  8  respectively,  11  is a switch which turns on when receiving and off when transmitting,  12  is a switch that turns off when receiving and on when transmitting for connection with a high frequency ground terminal  7 , and  13  to  16  are switches (second switches) that connect receiving terminals  3  to  6  to the antenna terminal  8  respectively via a switch  11 . Furthermore, in  FIG. 1 ,  81  denotes a high frequency signal line (a first signal line) for transferring transmitting signals that are input to the transmitting terminals  1  and  2  to the antenna terminal  8  and also for transferring received signals that are input to the antenna terminal  8  to the receiving terminals  3  to  6 ,  34  is a control circuit which generates a control voltage for controlling the gate of each switch to turn on or off, and  33  is the antenna switch circuit comprising the switches  9  to  16  and the control circuit  34 . In this configuration, the switches  9  and  10  are connected in the middle of the high frequency signal line  81  connecting the transmitting terminals  1  and  2  and the antenna terminal  8  respectively, and the switches  11  and  13  to  16  are connected in the middle of the high frequency signal line  8  connecting the receiving terminals  3  to  6  and the antenna switch  8  respectively. Thus, the antenna switch circuit  33  selectively connects the antenna terminal  8  to one of the terminals  1  to  6 . The number of switches given here is only an example and the present invention is not restricted to this number. 
     Each of the switches  9  to  16  is composed of an FET (Field Effect Transistor) device, and electrical conduction between the drain and source is controlled by a control voltage applied to the gate. 
     The switches  9  and  10  are each composed of two stage dual-gate transistors in order to deal with an electric power exceeding 1 W. This halves the voltage to be applied to one transistor. The switches  9  and  10  may also be composed of multi stage single-gate transistors or triple-gate transistors for dividing the voltage to be applied. 
     The switch  11  is composed of a one stage triple-gate transistor, the switch  12  is composed of a one stage dual-gate transistor, and the switches  13  to  16  are each composed of a one stage single-gate transistor. The antenna switch circuit  33  includes these switches and the control circuit  34 , all of which are integrated by the semiconductor process on a semi-insulating substrate of compound semiconductor to form a single-chip semiconductor integrated circuit. The control circuit  34  may be formed on a different chip from the one on which the switch circuit  33  is formed. 
     Control of each switch is made by a control voltage to be output from the control circuit  34 , i.e. an ON voltage to turn on the switch and an OFF voltage to turn off the switch, via each of control signal lines  25  to  32  connected to the gate of each switch. Each of resistors  17  to  24  inserted in each control signal line is used to prevent a high frequency signal that is input from the drain or source of the FET switch from leaking from the gate. 
     One end of each of the control signal lines  25  to  32  used to control the switches  9  to  16  is connected to each of the resistors  17  to  24 , and the other end is wired to the control circuit  34  side. Since a high frequency ground terminal  7  must be connected to a ground terminal external to the antenna switch circuit  33  chip by the shortest route, the ground terminal  7  is disposed on the opposite side of the control circuit  34 . 
     In this construction, there are cross points  35 ,  36 ,  37 ,  38 , and  39  where the control signals  26 ,  27 , and  30  to  32  cross with the high frequency signal line  81  respectively. Resistive elements  40  and  41  are inserted in the control signal line  26  (a second signal line) across the cross point  35 , and resistive elements  42  and  43  are inserted in the control signal line  27  across the cross point  36 . Also, across the cross point  37 , resistive elements  44  and  45  are inserted in the control signal line  30  (a third signal line), resistive elements  46  and  47  in the control signal line  31 , and resistive elements  49  and  50  in the control signal line  32 . Furthermore, across the cross point  38 , resistive elements  47  and  48  are inserted in the control signal line  31  and resistive elements  50  and  51  in the control signal line  32 , and across the cross point  39  resistive elements  51  and  52  is inserted in the control signal  32 . 
     Since these elements are formed on the same chip by the semiconductor process, interlayer insulating film made of dielectric film is filled between the wires at a cross point.  FIGS. 2 and 3  shows such cross point  35  and the surrounding structure.  FIG. 2  is a plan view of the cross point  35  and  FIG. 3  is a cross-sectional view of  FIG. 1  cut along the line A-A. The control signal line  26  is formed in the interlayer insulating film  87  that is formed on the semi-insulating substrate  86 , the resistive elements  40  and  41  are formed in the interlayer insulating film  88 , and the high frequency signal line  81  is formed on the interlayer insulating film  87 . The resistive elements  40  and  41  are connected to the control signal line  26  by means of a plug  84 . The cross point  35  is formed between the high frequency signal line  81  and the control signal line  26  in the interlayer insulating film  87 . Thus, the resistive elements  40  and  41  are disposed away from and across the cross point  35 . The other cross points  36 ,  37 ,  38 , and  39  and their surrounding areas are similarly configured. 
       FIG. 4  shows an electrical equivalent circuit of the cross point  35  and its surrounding area. The high frequency signal line  81  is connected to the control signal line  26  in which the resistive elements  40  and  41  are disposed via a coupling capacitance C. A signal which leaks through the coupling capacitance C is blocked by the resistive elements  40  and  41 . 
     The effect of decreasing signal leaks according to the present invention will be described below, for the case where the control circuit  34  exists on the same circuit. 
     First, during the transmission, when a transmitting signal is input to the transmitting terminal  1 , the control circuit  34  outputs voltages to turn on the switches  9  and  12  and turn off the switches  10 ,  11 , and  13  to  16 . At this time, the transmitting signal leaks from the cross points  35  and  36  between the high frequency signal line  81  and the control signal lines  26  and  27  respectively to the control signal lines  26  and  27 , via the interlayer insulating film over the cross points  35  and  36 . 
     Without the resistive elements  40  and  41  at the cross point  35 , the leaked high frequency signal will further leaks to the gate side of the switch  10  and the control circuit  34  side. If all of the resistive elements  18  have the same resistance, the combined resistance when seen from the control signal line  26  is about ¼ thereof, thus making the transmitting signal easy to leak. Furthermore, since a bypass capacitance is connected to each control signal line of the control circuit  34 , the control circuit  34  is short-circuited to the high frequency signal and thereby the high frequency signal is easy to leak. These cause insertion loss deterioration between the transmitting terminal  1  and the antenna terminal  8 . 
     Without the resistive elements  42  and  43  at the cross point  36 , the leaked high frequency signal will further leaks to the gate side of the switch  12  and the control circuit  34  side. There are two resistors  20  at the gate side of the switch  12 . If these resistors have the same resistance the combined resistance when seen from the control signal line  27  is ½ thereof, thus making the high frequency signal easy to leak to the drain side of the switch  12 , i.e. the source side of the switch  11 , and the terminal  7  side. Moreover, since the control circuit  34  is short-circuited to the high frequency signal and thereby the high frequency signal is easy to leak, as mentioned above. As a result, if the high frequency signal leaks to the control circuit  34  or the terminal  7  side, insertion loss deterioration occurs between the terminal  1  and the antenna terminal  8 , and if leaks to the source side of the switch  11 , isolation deterioration occurs between transmission and reception. 
     When the switch  10  is on and the switch  9  is off, if the resistive elements  42  and  43  are not inserted at the cross point  36 , insertion loss deterioration is caused between the transmitting terminal  2  and the antenna terminal  8  and isolation deterioration occurs between transmission and reception, as described above. At the cross point  35 , if the resistive elements  40  and  41  are not provided, a transmitting signal leaks to the control circuit  34  side and the switch  9  side. The control circuit  34  is short-circuited by a bypass capacitance and thereby a transmitting signal is easy to leak, thus resulting in insertion loss deterioration between the transmitting terminal  2  and the antenna terminal  8 . 
     As shown in  FIG. 1 , providing the resistive elements  40 ,  41 ,  42 , and  43  causes the control circuit  34  side and the gate side of the switch  10 , when seen from the cross points  35  and  37 , to be at high impedance and therefore the high frequency signal is hard to leak, thus preventing insertion loss deterioration or isolation deterioration. 
     Now, what happens to a signal input to the receiving terminal  4  from the receiving antenna terminal  8  will be described. The switches  9 ,  10 ,  12 ,  13 ,  15 , and  16  are turned off and the switches  11  and  14  turned on by the control circuit  34 , and a receiving signal input from the antenna terminal  8  is output to the receiving terminal  4  via the switches  11  and  14 . At this time, the signal deteriorates in performance at the cross points  35 ,  36 , and  38  between the high frequency signal line  81  and the control signal lines  26 ,  27 ,  30 ,  31 , and  32 . 
     The control circuit  34  side is short-circuited to the cross points  35  and  36 , thereby causing the high frequency signal to leak, which results in deteriorated insertion loss. However, providing the resistive elements  40  and  42  causes the control circuit  34  side to be at high impedance and thereby prevents insertion loss deterioration. 
     If the resistive elements  46  to  52  are not provided for the cross points  38 , insertion loss deterioration due to a leakage to the bypass capacitance at the control circuit  34  side becomes a problem. Also, isolation deterioration between the receiving terminals  4  and  3 , between the receiving terminals  4  and  5 , and between the receiving terminals  4  and  6  becomes a problem, which is caused by the leakage of a receiving signal to the high frequency wiring which connects the switch  13  and the receiving terminal  3  via the control signal lines  30  to  32  and the cross points  37  to  39 , the high frequency wiring which connects the switch  15  and the receiving terminal  5 , or the high frequency wiring which connects the gate of the switch  16  and receiving terminal  6  at the source side. 
     The resistive elements  47  and  50  suppresses the leakage to the control circuit  34  side and thereby prevents insertion loss deterioration and the leakage of a receiving signal to the high frequency wiring which connects the switch  13  and the receiving terminal  3 . The resistive elements  48  and  51  prevents a the leakage of a receiving signal to the high frequency wiring which connects the switch  15  and the receiving terminal  5 , the leakage of a receiving signal from the gate of the switch  16  to the receiving terminal  6 , and the isolation deterioration between the receiving terminals  4  and  3 , the receiving terminals  4  and  5 , and the receiving terminals  4  and  6 . 
     When a signal is input to the receiving terminal  3  from the antenna terminal  8 , the switches  9 ,  10 ,  12 , and  14  to  16  are turned off and the switches  11  and  13  are turned on by the control circuit  34 , and the receiving signal that is input from the antenna  8  is output to the receiving terminal  3  through the switches  11  and  13 . 
     At this time, the insertion loss deterioration is suppressed by the resistive elements  40  and  42  as in the case of receiving at the receiving terminal  4 . 
     For the cross point  37 , if the resistive elements  44  to  47 ,  49 , and  50  are provided, a receiving signal leaks to the bypass capacitance of the control circuit  34  via the control signal lines  30  to  32  and thereby the insertion loss is deteriorated. Also, a receiving signal leaks to the high frequency wiring which connects the switch  14  and the receiving terminal  4  via the control signal lines  30  to  32 . This deteriorates the Rx isolation, but the resistive elements  44 ,  46 ,  49 ,  47 , and  50  causes the control circuit  34  side when seen from the cross point  37  and the high frequency wiring side connecting the switch  14  and the receiving terminal  4  to be at high impedance, which prevents the leakage of a receiving signal and suppresses performance deterioration. Similarly, the leakage of a receiving signal to the high frequency wiring which connects the switch  15  and the receiving terminal  5  and that from the gate of the switch  16  to the receiving terminal  6  can be prevented. 
     This also applies to the receiving with the antenna terminal  8  and the receiving terminal connected and that with the antenna terminal  8  and the receiving terminal  6  connected. 
     As described above, according to this embodiment, leak current is suppressed by the resistive elements disposed away from and across the cross point and thereby signal leakage is effectively reduced, thus making it possible to reduce insertion loss and to ensure high isolation. Also, generation of joule heat can be suppressed that may occur when a resistive element is placed immediately under the cross point. 
     Depending on the amount of signal leakage at the cross point, it is possible to dispose the resistive elements across either of the cross points  41  and  43  or the cross points  37  to  39 . 
       FIG. 5  shows an embodiment of the high frequency module containing the antenna switch circuit according to the present invention. The module of this embodiment is a transmitting and receiving module for a quad band mobile phone. The quad band consists of the four mobile phone standards: GSM (Global System for Mobile communications) used in Europe, GSM, PCS (Personal Communication Services), and DCS (Digital Communication System), the latter three are used in the U.S. The present invention is not restricted to these standards. For convenience, GSM used in Europe is called GSM1 and GSM in the U.S. GSM2 herein. Since GSM uses 900 MHz band and PCS and DCS use 1800 MHz band, the high frequency module  53  is equipped with a transmitting signal input terminal  54  which is common to GSM1 and GSM2, and a transmitting signal input terminal  55  which is common to PCS and DCS. Furthermore, the module  53  is provided with a control terminal  56 , a PCS receiving terminal  57 , a DCS receiving terminal  58 , a GSM1 receiving terminal  59 , a GSM2 receiving terminal  60 , and an antenna terminal  61 . 
     To the transmitting terminal  54  the input terminal of a power amplifier circuit  62  for GSM1/2 is connected, and to the input terminal thereof the input terminal of a low pass filter  65  is connected that eliminates higher harmonics to be output from the power amplifier circuit  62 . To the output terminal thereof the terminal  2  of a switch circuit  33  is connected. 
     To the transmitting terminal  55  the input terminal of a power amplifier circuit  64  for PCS/DCS is connected, and to the output terminal thereof a low pass filter  65  is connected that eliminates higher harmonics to be output from the power amplifier circuit  64 . To the output terminal thereof the terminal  1  of the switch circuit  33  is connected. 
     The power amplifier circuits  62  and  64  and the low pass filters  63  and  65  make up a transmitting circuit  90 . According to the present invention, the transmitting circuit  90  is not restricted to this configuration. 
     To the control terminal  56 , a control terminal  66  of the control circuit  34  in the switch circuit  33  is connected. 
     To the terminal  3  of the switch circuit  33 , the input terminal of a SAW (Surface Acoustic Wave) filter  67  is connected that eliminates noises and spurious signals other than the PCS receiving frequency band, and to output terminal thereof the input terminal of a low noise amplifier circuit  68  for PCS is connected. To the output terminal thereof the RF (Radio Frequency) input terminal of a mixer (LO)  69  is connected, and the IF (Intermediate Frequency) output terminal is connected to the receiving terminal  57  of the module  53 . 
     To the terminal  4  of the switch circuit  33  the input terminal of a SAW filter  70  is connected that eliminates noises and spurious signals other than DCS receiving frequency band, and to the output terminal thereof the input terminal of a low noise amplifier circuit  71  for DCS is connected. To the output terminal thereof the RF terminal of a mixer  72  is connected, and the IF output terminal is connected to the receiving terminal  58  of the module  53 . 
     To the terminal  5  of the switch circuit  33  the input terminal of a SAW filter  73  is connected that eliminates noises and spurious signals other than GSM1 receiving frequency band, and to the output terminal thereof the input terminal of a low noise amplifier circuit for GSM1 is connected. To the output terminal thereof the RG input terminal of a mixer  75  is connected, and the IF output terminal is connected to the receiving terminal  59  of the module  53 . 
     To the terminal  6  of the switch circuit  33  the input terminal of a SAW filter  76  is connected that eliminates noises and spurious signals other than GSM2 receiving frequency band, and to the output terminal thereof the input terminal of a low noise amplifier circuit for GSM2 is connected. To the output terminal thereof the RG input terminal of a mixer  78  is connected, and the IF output terminal is connected to the receiving terminal  60  of the module  53 . 
     The local terminal of the mixers  69 ,  72 ,  75 , and  78  are connected to the terminal  79  of the module  53 . 
     The low noise amplifier circuits  68 ,  71 ,  74 , and  77 , the SAW filters  67 ,  70 ,  73 , and  76 , and the mixers  69 ,  72 ,  75 , and  78  make up a receiving circuit  91 . According to the present invention, the receiving circuit  91  is not restricted to this configuration. 
     The above sections are mounted on a module substrate to form the module  53 , and the antenna  80  is connected to the antenna terminal  61  of the module  53 . 
     Since the module  53  is applied to a mobile terminal and supports a plurality of communication standards, improved power efficiency at the transmitting side, i.e. low insertion loss of the switch circuit  33 , low insertion loss at the receiving side, and high Rx isolation are required. 
     Furthermore, since the transmitting frequencies of PCS band and the receiving frequencies of DCS band have overlapped operating frequencies in the range from 1850 to 1875 MHz, if a PCS transmitting signal in this band is output, the power that is input to the SAW filter  70  is determined by the isolation between PCS transmission and DCS reception. At this time, the SAW filter is unable to eliminate the PCS transmitting signals and also the SAW filter  70  may be destroyed due to over-input power, which may lead to destruction of the low noise amplifier circuit  71 . Since the power resistance of the SAW filter is approximately 0 dBm and the maximum transmitting power of the PCS transmitter is 34.5 dBm, 36 dB or more isolation is required with a margin of 1.5 dB. The operation of the switch circuit was described in detail with reference to  FIG. 1 , so no description is made here. 
     Now, an advantage of the present invention will be described taking the case of PCS transmission as an example. During the PCS transmission, a signal is input from the control terminal  56  to the terminal  66  of the control circuit  34 . The control circuit  34  is a decoder circuit, and apply voltages to the control signal lines  25  to  32  to turn on the switches  9  and  12  and turn off the switches  10 ,  11 , and  13  to  16  according to the combination of signals input to the terminal  66 . The PCS transmitting signal input to the terminal  55  is amplified to a desired transmitting power by the power amplifier circuit  64 , higher harmonics are eliminated by the filter  65 , and is input to the terminal  1  of the switch  33 . The PCS transmitting signal is radiated from the antenna  80  via the switch  9 , terminal  8 , and terminal  61 . 
     At this time, if the resistive elements  40 ,  42 , and  43  are not provided, some of the PCS transmitting signals leak to the control circuit  34  side and the gate side of the switch  12  at the cross points  35  and  36 . Assuming that the area of the cross point is 300 μm 2 , the thickness of the interlayer insulating film 0.5 μm, and the specific inductive capacity 3.8, the capacitance at the cross point will be 0.2 pF. The insertion loss obtained from this is shown in  FIG. 6  and the Tx, Rx isolation is shown in  FIG. 7 . The insertion loss in this case will be 0.9 dB at 1.91 GHz. 
     In contrast, if the resistive elements  40 ,  42 , and  43  are provided according to the present invention, the insertion loss becomes 0.8 dB and therefore insertion loss deterioration can be reduced. The power efficiency will be increased about 2.3% due to the reduction of 0.1 dB in insertion loss at the transmitting side. 
     The Tx, Rx isolation for the band where the frequencies of PCS transmission and DCS reception are overlapped was 33 dB without the resistive elements  40 ,  42 , and  43 . However, providing the resistive elements  40 ,  42 , and  43  according to the present invention has improved by 5 dB to 38 dB. This improvement of 5 dB in Tx, Rx isolation ensures a sufficient margin in the destruction voltage resistance of the SAW filter  70 . 
     This embodiment has realized the prevention of the deterioration of insertion loss and isolation while supporting the plurality of communication standards.