JP2006270245A - Antenna switch module and communication device using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna switch module capable of shifting the peak of the attenuation between double and triple frequencies and capable of increasing the amount of attenuation between the double and triple frequencies. <P>SOLUTION: The antenna switching module comprises a common antenna; the transmission and reception circuits of a plurality of transmission and reception systems having different passbands; a branching filter connected between the antenna and the transmission and reception circuits; an I/O terminal connected to a branching circuit; an input (reception) terminal connected to the reception circuit; an output (transmission) terminal connected to the transmission circuit; and an antenna switch circuit provided between the input terminal and the output (transmission) one to switch the connection between the antenna and the transmission circuit and that between the antenna and the reception circuit. In the antenna switch circuit, a diode element is connected to a low-pass filter in series in a transmission path from the transmission circuit to the antenna, and a transmission line is provided between the diode element and the low-pass filter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antenna switch module for switching an antenna to a signal path of at least two frequency bands and a communication using the same in a multiband mobile phone system having a communication method different from that of frequency bands such as GSM850, EGSM, DCS, and PCS. It relates to the device.

  The progress of globalization of mobile phones and the like is fast, and mobile phones using a plurality of frequency bands and a plurality of communication methods have been put into practical use. Since it is necessary to operate as a multiband terminal having a different frequency band and communication method, the circuit becomes complicated, and an increase in the number of parts causes an increase in the size and cost of the device. For this reason, it is necessary to actively reduce the number of parts by consolidating circuits and share parts. In particular, the sharing of a large antenna greatly contributes to the miniaturization of the terminal. Therefore, the development of a small antenna switch circuit is an important issue in order to switch one antenna between multibands.

As antenna switch modules become smaller and the number of bands used increases, the amount of harmonics generated during transmission has become a problem. A low-pass filter that combines a series resonance circuit and a parallel resonance circuit is used as means for suppressing the amount of harmonic generation. (For example, refer to Patent Document 1). In this circuit, the resonance frequency of the series resonance circuit and the parallel resonance circuit is adjusted to about twice or three times the main signal frequency, a transmission line for phase adjustment is connected between the series resonance circuit and the parallel resonance circuit, and the attenuation is reduced. It is an increase. Also, a method is used in which an attenuation pole is formed by a resonance circuit composed of an inductor and a capacitor at one end of a low-pass filter that constitutes a parallel resonance circuit to increase the attenuation (for example, Patent Document 2).
JP 2004-328136 A (refer to claim 2 and FIG. 6) Japanese Patent Laying-Open No. 2004-241875 (refer to claim 1, FIG. 1)

  In the low-pass filters of Patent Documents 1 and 2, it is necessary to configure two circuits, a parallel resonance circuit and a series resonance circuit. Therefore, this circuit has a larger circuit configuration than the conventional low-pass filter. Digital devices typified by mobile phones, which have been remarkably developed in recent years, have a strong demand for miniaturization, and the same applies to the built-in components. There is also a demand for miniaturization of an antenna switch module in which a circuit including such a low-pass filter and a duplexer is configured with an electrode pattern on a dielectric sheet and these sheets are laminated to form a laminated body. Therefore, it is disadvantageous from the viewpoint of miniaturization to construct the low-pass filter as in Patent Documents 1 and 2.

  In addition, the resonance frequency of a general low-pass filter in the transmission path is often approximately twice the transmission frequency. FIG. 7 (a) shows high-frequency characteristics simulation data in which a low-pass filter having a DCS / PCS communication mode (transmission frequency: 1710 to 1910 MHz) and a resonance frequency doubled (3420 to 3820 MHz) is connected. An example of this antenna switch circuit is shown in FIG. The circuit of FIG. 7B does not have a circuit configuration for attenuating the triple frequency (5130 to 5730 MHz). However, in practice, the magnitude of the harmonic generation amount of the triple frequency as well as the double frequency is specified in the communication device, and the harmonic generation amount generated from the power amplifier is large in the generation amount of the low-order harmonics. Therefore, it is necessary to preferentially attenuate these low-order harmonic components between the antenna terminal and the power amplifier. Therefore, in order to obtain the attenuation amount of the triple frequency, the circuit around the low-pass filter is adjusted to obtain the attenuation amount of the double frequency while reducing the attenuation amount near the intermediate frequency between the double frequency and the triple frequency. This is dealt with by creating a peak of attenuation near the triple frequency. In FIG. 7 (a), since the attenuation pole near the actual triple frequency is on the higher frequency side than the target triple frequency (5130-5730MHz), the harmonic attenuation amount is out of specification. However, at this time, adjusting the resonance frequency with the low-pass filter itself is troublesome, and even if it is adjusted, it is unavoidable that the second-harmonic attenuation is shifted, and the resonance frequency of the low-pass filter cannot be easily adjusted. . Therefore, it has been difficult to obtain both the second harmonic attenuation and the third harmonic attenuation with a simple low-pass filter.

  Therefore, an object of the present invention is to easily shift the peak of attenuation between the double frequency and triple frequency in a general switch circuit, and to double the frequency and triple the single-stage low-pass filter. It is an object to provide an antenna switch module and a wireless communication device such as a mobile phone using the antenna switch module, which can easily obtain a large amount of frequency attenuation.

  The present invention includes a common antenna, a plurality of transmission / reception transmission circuits and reception circuits having different passbands, a duplexer connected between the antenna and the transmission circuit and reception circuit, and the separation circuit An input / output terminal connected to the receiving circuit, an input (receiving) terminal connected to the receiving circuit, and an output (transmitting) terminal connected to the transmitting circuit, the input / output terminal and the output (transmitting) terminal In an antenna switch module provided with an antenna switch circuit for switching the connection between the antenna and the transmission circuit and the connection between the antenna and the reception circuit, a transmission path from the transmission circuit to the antenna is included in the antenna switch circuit. Is characterized in that a diode element and a low-pass filter are connected in series, and a transmission line is provided between the diode element and the low-pass filter. An antenna switch module.

  In the present invention, a capacitor element is connected between the input / output terminal and the diode element described above, an inductor element is connected between the transmission line and the low-pass filter, and the capacitor element and the inductor element described above are It is desirable that the antenna switch modules are connected in series.

  The diode element in the present invention is preferably an antenna switch module having an input / output terminal side as an anode and an output terminal side as a cathode.

  The present invention is a communication apparatus using the antenna switch module described above.

  According to the present invention, by connecting a transmission line between a diode element constituting an antenna switch circuit and a low-pass filter, harmonic components such as second harmonic and third harmonic generated during transmission can be easily attenuated. It became possible to make it. In addition, by using these antenna switch modules, it is possible to configure a small and high-performance communication device.

  First, the antenna switch circuit portion of the present invention will be described with reference to FIG. In FIG. 1, 11 is an antenna terminal, 12 is a demultiplexing circuit, 13 is a diode, 14 is a transmission line, 15 is a low-pass filter, 16 is a reception terminal, 17 is a transmission terminal, and 18 is an antenna switch circuit. In the present invention, a transmission line 14 is connected between a diode 13 and a low-pass filter 15 as shown in FIG. By changing the line width, length, shape, etc. of the transmission line 14, harmonic components such as second harmonic and third harmonic generated during transmission can be easily attenuated. Even if the transmission line 14 is connected to the anode side of the diode 13, the effect can be obtained. However, since the transmission line 14 affects the impedance on the receiving circuit side, it is preferable to connect the transmission line 14 to the cathode side.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
(Example)
FIG. 2 shows an embodiment of an antenna switch module circuit using the antenna switch circuit of the present invention. This antenna switch module has GSM850 band (transmission frequency: 824 to 849 MHz, reception frequency: 869 to 894 MHz), EGSM band (transmission frequency: 880 to 915 MHz, reception frequency: 925 to 960 MHz), DCS band (transmission frequency: 1710 to It handles signals in four different frequency bands: 1785 MHz, reception frequency: 1805 to 1880 MHz, and PCS band (transmission frequency: 1850 to 1910 MHz, reception frequency: 1930 to 1990 MHz). The demultiplexing circuit 21 connected to the antenna is a combination of a low-pass filter 22 composed of an LC circuit and a high-pass filter 23 composed of an LC circuit. The antenna switch circuits 24 and 26 are connected to the subsequent stage of the branching circuit 21. The antenna switch circuit 24 switches between transmission signals and reception signals of the GSM850 and EGSM paths, and the antenna switch circuit 26 switches between transmission signals and reception signals of the DCS and PCS paths. Further, a GaAs switch 30 is connected to the reception path side downstream of the antenna switch circuit 24, and a GaAs switch 31 is connected to the reception path side downstream of the antenna switch circuit 26. These GaAs switches have a function of switching between GSM850 and EGSM reception signals and DCS and PCS reception signals.

  The capacitor CD6 and the inductor LD4 in the circuit 27 are a part of a notch filter for attenuating a leakage signal from the DCS / PCSTx terminal generated at the time of GSM850 / EGSM transmission. When the leakage signal passes through the diode D4, a large harmonic is generated because the diode D4 is in the OFF state. However, by connecting the transmission line 28 to this circuit as shown in FIG. 1, the leakage signal can be reflected by the capacitor components of the inductor LD4 and the diode D4 in the circuit 27. For this reason, the leakage signal input to the diode D4 becomes small, and the amount of harmonic generation can be attenuated. In the transmission line 28, when DCS / PCS is transmitted, a line in which the diode element and the transmission line are connected serves as a main line, and hardly affects the high frequency characteristics.

  Next, the state of the antenna switch module circuit during DCS / PCS transmission will be described. At the time of transmission, VC2 and VC3 are turned on, and VC1 and VC4 are turned off. When the signal input from the DCS / PCS transmission terminal passes through the low-pass filter 29, the second harmonic and the third harmonic component are attenuated. The signal that has passed through the low-pass filter 29 passes through a circuit 27 that is composed of a diode element D4, a transmission line 28, an inductor element LD4, and a capacitor CD6. At this time, since VC2 is in the on state, the diode element D4 incorporated in the circuit 27 is in the on state, and the signal passing therethrough is hardly attenuated. The signal that has passed through the circuit 27 reaches the connection point P1 between the branching circuit 23 and the λ / 4 transmission line LD1. At this time, the receiving terminal side of the λ / 4 transmission line LD1 is in a short-circuit state substantially at the transmission frequency by the receiving side diode D3 and the grounded capacitor CD4. For this reason, when the receiving terminal side is viewed from the connection point P1, it becomes open at a high frequency and almost no signal leaks to the receiving side. As a result, the signal passing through the low-pass filter 29 passes through the high-pass filter 23 of the branching circuit 21 and is radiated from the antenna terminal.

  Here, first, simulation data of the attenuation amount from DCS / PCS_Tx to ANT when the transmission line 28 is not connected in the circuit 27 is shown in FIG. 3A, and the measured data is shown in FIG. 3B. It should be noted that the amount of attenuation is not limited as long as the area below the filled area in the diagram of the double frequency (3420 to 3820 MHz) can be cleared below the area filled in the figure of the triple frequency (5130 to 5730 MHz). In the antenna switch module, it is necessary to attenuate harmonic signals such as twice or three times the DCS / PCS_Tx transmission frequency. However, in order to satisfy the miniaturization of the antenna switch module, only the single-stage low-pass filter 29 can be connected at most, and it is difficult to connect the multi-stage low-pass filter as in Patent Documents 1 and 2. . The high-frequency characteristics from DCS / PCS_Tx to ANT of the antenna switch module using the single-stage low-pass filter can satisfy the triple frequency attenuation that requires 25 dB or less in the simulation data of FIG. However, as a result of measuring the actual product module, as shown in FIG. 3 (b), the double frequency attenuation was able to obtain the target attenuation of 30 dB or more, but the triple frequency attenuation was the worst. The point was 13 dB, and the standard value was greatly out. Since the resonance frequency of the double frequency attenuation is almost at the target position, it is difficult to shift the resonance frequency.

  Next, simulation data of the high frequency characteristics of the path from DCS / PCS_Tx to ANT in the antenna switch module to which the present invention is applied is shown in FIG. 4 (a), and the measured data is shown in FIG. 4 (b). Since this antenna switch module is connected to the transmission line 28, the peak between the double frequency and the triple frequency is shown in FIG. 4 (a) in the simulation in the case where the transmission line 28 is not connected. It was possible to shift about 500 MHz to the low frequency side compared with around 5 GHz. This peak can be easily adjusted by changing the length and shape of the transmission line 28. For example, when the length of the transmission line 28 is increased, the amount of peak shift increases, and a peak rises on the lower frequency side than in FIG. If the transmission line 28 is wound, the inductor component increases and the peak shifts to the lower frequency side than in FIG. Further, FIG. 4B shows the high frequency characteristics of an actual product module of a circuit to which the transmission line 28 is connected. By connecting the transmission line, the maximum pole of the attenuation that was in the vicinity of the triple frequency in FIG. 4B could be shifted to almost the middle between the double frequency and the triple frequency. Therefore, by shifting the peak of the attenuation amount to the vicinity of the triple frequency while ensuring the target 30 dB of the second harmonic attenuation amount, it is possible to ensure the standard value of 25 dB or more of the third harmonic attenuation amount. Yes.

  Next, FIG. 5 shows a result of comparison of transmission frequency insertion loss depending on whether or not the transmission line 28 is connected. Usually, when a transmission line is connected to a main line through which signals are transmitted, insertion loss is deteriorated. However, in the present invention, there is almost no deterioration in insertion loss before and after the transmission line 28 is connected. This is because the transmission line 28 is sufficiently shorter than λ / 4 of the transmission wavelength, and hardly affects the phase near the transmission frequency. In the present embodiment, the length of the transmission line 28 is 1.2 mm and the line width is 75 μm as described below, and an insertion loss of about 0.01 dB can be seen with or without the transmission line, and there is almost no influence. Recognize.

  Now, the antenna switch module according to the present invention has a laminated structure in which a plurality of dielectric sheets are laminated as shown in FIG. 6, and can be configured to be light and small by mounting chip components on the laminated body. The RX1-4, TX1-2, and ANT terminals on the back side are terminals for high frequency signals, the RX1 terminal is a GSM850_Rx terminal, the RX2 terminal is an EGSM_Rx terminal, the RX3 terminal is a DCS_Rx terminal, the RX4 terminal is a PCS_Rx terminal, and the TX1 terminal is a GSM850. The / EGSM_Tx terminal and the TX2 terminal correspond to the DCS / PCS_Tx terminal. GND is a terminal connected to the ground. Each high-frequency signal terminal is designed so that the transmission terminals are not adjacent to each other. As a result, interference between transmission terminals having high output can be suppressed and insertion loss can be improved.

  The electrode printed on the dielectric sheet of FIG. 6 will be described. FIG. 6 shows a part of a sheet forming a laminated structure of an antenna switch module using the present invention. On the top surface, chip capacitors, inductors, resistors, PIN diodes, GaAs switches, and the like are mounted. On the second sheet, LG3A, LG5A, LF4A, and LF5A are printed as main transmission lines. LG3A is a part of the λ / 4 transmission line LG3 on the receiving side in the switch circuit 24. LG5A is a transmission line for connecting the switch circuit 24 and the GaAs switch 30. The length of the transmission line 38 is about 1.2 mm, and the line width is 75 μm. By changing the length of the transmission line, the transmission line width, and the shape of the transmission line, the attenuation pole of the triple frequency can be shifted. The transmission line 28 is desirably designed so as not to interfere with the low-pass filter 29 and the branching circuit 23. Further, when the transmission line 28 is connected to the anode side of the diode D4, the same effect can be obtained. However, since the impedance of the λ / 4 transmission line LD3 in the reception path is affected, in this embodiment, the cathode of the diode D4. It is desirable to connect the transmission line 38 to the side.

  Three ground electrodes are printed on the third sheet. This electrode pattern has a role of forming a ground capacitance with the ground electrode, and is inserted in order to prevent interference between upper and lower layers. CF2A is a part of the capacitor electrode CF2 for constituting the high-pass filter 23 of the duplexer 21, and LG1A is a part of the transmission line LG1 constituting the low-pass filter 25. By adjusting the length and width of the transmission line, the attenuation characteristic of the high-frequency characteristic between EGSM_Tx → ANT can be adjusted.

  On the fourth sheet, electrodes that are a part of eight main transmission lines are printed. LF1A and LF2A are part of the transmission lines LF1 and LF2 of the low-pass filter 21 constituting the duplexer 33. LG1B and LG2A are part of the transmission lines LG1 and LG2 constituting the low-pass filter 25. LG3A is a part of the λ / 4 transmission line LG3 on the receiving side of the antenna switch circuit 24. The LD 1A is a part of the transmission line constituting the low pass filter 29. LV5A is a transmission line for applying a voltage to the GaAs switches 30 and 31 mounted on the upper surface.

  In the present invention, an electrode of each layer of a dielectric sheet having a thickness of 20 to 80 μm (size after integral firing) is printed and connected through through holes. In FIG. 6, the through hole is a black square. A hole is formed in the square portion to form a through hole. Examples of the dielectric include a low temperature co-fired ceramic (LTCC) material such as alumina glass ceramic. For this laminate, a green sheet made of a ceramic dielectric material that can be fired at a low temperature is prepared, and a conductive paste such as Ag, Pd, or Cu is printed on the green sheet to form a desired electrode pattern. Are appropriately laminated and integrally fired at about 900 ° C. The thickness of the sheet is generally in the range of 25 to 110 μm, and is controlled by the doctor blade method or the like depending on the intended use. A large sheet on which a large number of predetermined internal electrode patterns are formed is laminated, cut into individual chip sizes, and fired to form terminal electrodes, thereby producing a dielectric laminated body. The terminal electrode usually has a three-layer structure of Ag—Ni—solder, and the Ni layer is sufficient to obtain solder heat resistance and to obtain solder wetness by the solder layer. Solder printing using a metal mask is performed on this dielectric multilayer body, and then GaAs switches, diode switches, chip capacitors, resistors, inductors, etc. that cannot be formed in the multilayer body due to their large capacity are mounted and reflowed. To do.

  In the present invention, it is desirable to dispose a metal case so as to surround the chip component disposed on the laminate, or to mold it with a heat resistant resin that can withstand the heat during reflow soldering. By using a metal case or heat-resistant resin, it is possible to flatten the top surface of the chip, and it becomes easier for the manufacturer using the antenna switch module to perform vacuum suction during automatic mounting.

  The present invention can be applied not only to the antenna switch module but also to other communication devices. In particular, the present invention can be applied to Bluetooth communication devices, wireless LAN communication devices (802.11a / b / g / n) that handle high frequencies.

It is a circuit block diagram which shows one Example of the antenna switch circuit based on this invention. It is an equivalent circuit diagram of an antenna switch module using the antenna switch circuit according to the present invention. FIG. 2 shows attenuation characteristics of the path from DCS / PCSTx to ANT when there is no transmission line according to the present invention in the circuit of FIG. 2, where (a) shows simulation data and (b) shows measured data. . FIG. 2 shows the attenuation characteristics of the path from DCS / PCSTx to ANT when the transmission line according to the present invention is present in the circuit of FIG. 2, where (a) shows simulation data and (b) shows measured data. . FIG. 3 shows insertion loss data of a path from DCS / PCSTx to ANT with and without the transmission line according to the present invention in the circuit of FIG. FIG. 3 is a partial development view of a laminated sheet when the antenna switch module of the present invention is configured in a laminated body. An example of a conventional low-pass filter is shown, in which (a) shows an attenuation characteristic, and (b) shows an equivalent circuit diagram.

Explanation of symbols

11: antenna terminal, 12: demultiplexing circuit, 13: diode element, 14: transmission line, 15: low-pass filter, 16: receiving terminal, 17: transmitting terminal, 18: antenna switch circuit 21: demultiplexer, 22: demultiplexing Low-pass filter circuit constituting a wave filter, 23: High-pass filter circuit constituting a duplexer, 24: GSM850 / EGSM path antenna switch circuit, 25: GSM850 / EGSM_Tx path low-pass filter, 26: DCS / PCS path antenna Switch circuit, 27: Harmonic generation suppression circuit when DCS / PCS_Tx is OFF, 28: Transmission line according to the present invention, 29: Low-pass filter of DCS / PCS_Tx path, 30: GaAs for switching GSM850 / EGSM received signal Switch, 31: Turns off DCS / PCS received signal GaAs switch 71: Connection terminal with branching circuit, 72: Reception terminal, 73: Power supply terminal, 74: Transmission terminal, 75: Antenna switch circuit LF: Transmission line LG constituting the duplexer LG: GSM side antenna Transmission line LD constituting a switch circuit: Transmission line CF constituting a DCS side antenna switch circuit: Capacitor electrode constituting a duplexer CG: Capacitor electrode constituting a GSM side antenna switch circuit CD: Constructing a DCS side antenna switch circuit Capacitor electrode D: Diode element G: GaAs switch GND: Ground terminal Tx1: GSM850 / EGSM transmission terminal Tx2: DCS / PCS transmission terminal Rx1: GSM850 reception terminal Rx2: EGSM reception terminal Rx3: DCS reception terminal Rx4: PCS reception terminal

Claims (4)

A common antenna, a plurality of transmission / reception transmission / reception circuits having different passbands, a duplexer connected between the antenna and the transmission / reception circuit, and the demultiplexing circuit An input / output terminal, an input (reception) terminal connected to the reception circuit, and an output (transmission) terminal connected to the transmission circuit, and between the input / output terminal and the output (transmission) terminal In an antenna switch module provided with an antenna switch circuit for switching the connection between the antenna and the transmission circuit and the connection between the antenna and the reception circuit, a diode element is provided in the transmission path from the transmission circuit to the antenna in the antenna switch circuit. An antenna comprising a low-pass filter connected in series and a transmission line provided between the diode element and the low-pass filter Switch module. A capacitor element is connected between the input / output terminal and a diode element, an inductor element is connected between the transmission line and a low-pass filter, and the capacitor element and the inductor element are connected in series. The antenna switch module according to claim 1. 3. The antenna switch module according to claim 1, wherein the diode element has an input / output terminal side as an anode and an output terminal side as a cathode. A communication apparatus using the antenna switch module according to claim 1.