JP2005260837A - Antenna switching module and design method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna switching module capable of easily establishing the compatibility between attenuation of an unnecessary signal and reduction in an insertion loss of a communication signal. <P>SOLUTION: The antenna switching module 10 is configured such that a low pass filter circuit LPF 1 for forming an attenuation pole to a frequency within a communication harmonic band of a DCS system is located in a signal path for interconnecting an antenna terminal ANT and a diplexer circuit DP, a low pass filter circuit LPF 2 for forming an attenuation pole to a frequency within a communication frequency band of the DCS system is located in a signal path connected to a switch circuit SW 2 in the diplexer circuit DP, and a low pass filter circuit LPF 3 for forming an attenuation pole to a frequency within a transmission second harmonic band of an EGSM system is located in a signal path for interconnecting the switch circuit SW 2 and a transmission terminal TX2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an antenna switching module in which at least a part of an antenna switching circuit is formed on a laminate in which dielectric ceramic layers are laminated, and a design method thereof.

  As mobile communication devices such as mobile phones, so-called multiband communication devices capable of performing a plurality of radio wave communication with different communication frequency bands are known. A multi-band compatible communication device includes a transmission circuit and a reception circuit corresponding to each of a plurality of communication systems having different communication frequency bands, an antenna unit that transmits and receives communication radio waves, and the plurality of transmission circuits, reception circuits, and antenna units. And an antenna switching module that forms an antenna switching circuit for switching the signal path between the antenna and the signal path.

  Conventionally, an antenna switching module in which at least a part of an antenna switching circuit is formed on a laminated body in which dielectric ceramic layers are laminated is known as an antenna switching module in order to reduce the size and increase the integration. Various filter circuits are disposed in the signal path of the antenna switching circuit in order to attenuate unnecessary signals such as harmonics. The following patent document discloses an antenna switching module in which various filter circuits are arranged in the signal path of the antenna switching circuit.

JP 2000-165288 A

  However, sufficient studies have not been made on the filter circuit in the antenna switching circuit. Since the filter circuit attenuates unnecessary signals and also attenuates communication signals, it is difficult to achieve both attenuation of unnecessary signals and reduction of insertion loss of communication signals.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an antenna switching module that can easily achieve both attenuation of unnecessary signals and reduction of insertion loss of communication signals. To do.

  In order to solve the above-described problems, an antenna switching module according to the present invention switches a signal path between a transmission circuit and a reception circuit of a plurality of communication systems having different communication frequency bands and an antenna unit that transmits and receives communication radio waves. An antenna switching module in which at least a part of an antenna switching circuit to be performed is formed in a laminated body in which dielectric ceramic layers are laminated, wherein the antenna switching circuit has a relatively low communication frequency band among the plurality of communication systems. A low frequency side switch circuit for switching the signal path to the low frequency side communication system to be used, and a high frequency side using a communication frequency band in the vicinity of a second harmonic of the communication frequency of the low frequency side communication system among the plurality of communication systems A high frequency side switch circuit for switching the signal path for a communication system, and the low frequency side switch And a diplexer circuit that distributes each received signal and each transmitted signal between the high-frequency side switch circuit and the antenna unit, and the signal path that connects the antenna unit and the diplexer circuit includes the high-frequency side A first low-pass filter that forms an attenuation pole at a frequency in a harmonic band with respect to a communication frequency band of the communication system is disposed, and a signal path connected to the low-frequency side switch circuit in the diplexer circuit is connected to the high-frequency side A second low-pass filter that forms an attenuation pole at a frequency within a communication frequency band of the communication system, and a signal path that connects the low-frequency side switch circuit and the transmission circuit of the low-frequency side communication system, A third row forming an attenuation pole at a frequency within the second harmonic band with respect to the transmission frequency band of the low frequency side communication system. Characterized by being arranged pass filter.

  According to the antenna switching module of the present invention, the arrangement and characteristics of the first low-pass filter attenuate the harmonics common to the high-frequency communication system and the low-frequency communication system, and the insertion loss of the low-pass filter increases rapidly. The frequency can be sufficiently separated from the communication frequency band of the high frequency side communication system and the low frequency side communication system, and the insertion loss of the communication signal can be reduced. Further, the arrangement and characteristics of the second low-pass filter attenuate the unnecessary signal near the second harmonic of the low-frequency communication system on the low-pass filter side, and in the diplexer circuit coupled to the low-pass filter. On the high pass filter side, it is possible to reduce the insertion loss of the communication signal of the high frequency side communication system in the vicinity of the attenuation pole frequency. Further, the arrangement and characteristics of the third low-pass filter can ensure a wide attenuation band for attenuating the second harmonic of the transmission signal of the low-frequency communication system together with the second low-pass filter. As a result, it is possible to easily achieve both attenuation of unnecessary signals and reduction of insertion loss of communication signals.

  The antenna switching module of the present invention having the above-described configuration can also take the following aspects. The attenuation pole frequency of the first low-pass filter may be a frequency within a second harmonic band with respect to a communication frequency band of the high-frequency communication system. This can sufficiently attenuate higher-order harmonics among higher harmonics.

  The attenuation pole frequency of the second low-pass filter may be a center frequency of a transmission frequency band or a reception frequency band of the high-frequency communication system. As a result, when the attenuation pole is the center frequency of the transmission frequency band, it is possible to obtain a filter characteristic that emphasizes the reduction of insertion loss with respect to the transmission signal of the high frequency communication system, and the attenuation pole is set to the reception frequency band. In the case of the center frequency, it is possible to obtain filter characteristics that emphasize reduction of insertion loss with respect to the received signal of the high frequency side communication system.

  Further, the attenuation pole frequency of the third low-pass filter is between the attenuation pole frequency of the second low-pass filter among the frequencies that are twice the maximum transmission frequency or the minimum transmission frequency of the low-frequency communication system. The frequency band created in (1) may be one frequency that overlaps a wider range than the second harmonic band with respect to the transmission frequency band of the low-frequency communication system. As a result, a sufficient attenuation band for attenuating the second harmonic of the transmission signal of the low frequency communication system can be secured.

  Further, a high-pass filter that forms an attenuation pole at a frequency within a communication frequency band of the low-frequency communication system may be disposed in a signal path connected to the high-frequency switch circuit in the diplexer circuit. Thereby, on the second low-pass filter side in the diplexer circuit coupled to the high-pass filter, it is possible to reduce the insertion loss of the communication signal of the low-frequency communication system in the vicinity of the attenuation pole frequency. Furthermore, the attenuation pole frequency of the high-pass filter may be the center frequency of the transmission frequency band or the reception frequency band of the low-frequency communication system. As a result, when the attenuation pole is set to the center frequency of the transmission frequency band, it is possible to obtain a filter characteristic that emphasizes the reduction of insertion loss with respect to the transmission signal of the low frequency side communication system, and the attenuation pole is set to the reception frequency. In the case where the center frequency of the band is used, it is possible to obtain a filter characteristic that emphasizes the reduction of the insertion loss with respect to the received signal of the low frequency communication system.

  The low-frequency communication system is an EGSM (Extended Global System for Mobile Communications) system (transmission frequency band: 0.880 to 0.915 GHz (hereinafter referred to as GHz), reception frequency band: 0.925 to 0.960 GHz) When the high frequency side communication system conforms to the DCS (Digital Communication System) system (transmission frequency band: 1.710 to 1.785 GHz, reception frequency band: 1.805 to 1.880 GHz), each low-pass filter As a specific numerical value of the attenuation pole formed by the low frequency side switch circuit, the low frequency side switch circuit switches the signal path for the low frequency side communication system compliant with the EGSM system, and the high frequency side switch circuit is connected to the DCS system. The signal path is switched with respect to the compliant high-frequency communication system, and the first low-pass filter is switched. The attenuation pole frequency of the second low-pass filter is 1.72 to 1.78 GHz, and the attenuation pole frequency of the third low-pass filter is 3.42 to 3.57 GHz. The frequency may be 1.80 to 1.86 gigahertz. As a result, it is possible to obtain filter characteristics emphasizing reduction of insertion loss with respect to the transmission signal of the DCS system.

  The low-frequency side switch circuit switches the signal path for the low-frequency side communication system compliant with the EGSM system, and the high-frequency side switch circuit performs the signal for the high-frequency side communication system compliant with the DCS system. The path is switched, and the attenuation pole frequency of the first low-pass filter is 3.42 to 3.57 GHz, and the attenuation pole frequency of the second low-pass filter is 1.81 to 1.87 GHz. In addition, the attenuation pole frequency of the third low-pass filter may be 1.73 to 1.79 gigahertz. As a result, it is possible to obtain filter characteristics that emphasize reduction of insertion loss with respect to the received signal of the DCS system.

  The high frequency side switch circuit includes one diplex support connected to the diplexer circuit, one transmission port connected to a transmission circuit of a predetermined high frequency communication system, and reception of the predetermined high frequency communication system. The high frequency side switch circuit may include a single diplex support connected to the diplexer circuit and two different high frequency side communication systems. A circuit having one transmission port commonly connected to the transmission circuit and two reception ports respectively connected to the reception circuits of the two different high-frequency communication systems may be used.

  In order to solve the above-described problem, a method for designing an antenna switching module according to the present invention includes a signal path between a transmission circuit and a reception circuit of a plurality of communication systems having different communication frequency bands and an antenna unit that transmits and receives communication radio waves. At least a part of the antenna switching circuit that performs switching is formed in a laminated body in which dielectric ceramic layers are laminated, and the antenna switching circuit uses a relatively low communication frequency band of the plurality of communication systems. A low-frequency side switch circuit that switches the signal path to the side communication system, and a high-frequency side communication system that uses a communication frequency band near the second harmonic of the communication frequency of the low-frequency side communication system among the plurality of communication systems. A high-frequency switch circuit for switching the signal path, the low-frequency switch circuit, and the high-frequency switch A method for designing an antenna switching module comprising a diplexer circuit that distributes each received signal and each transmitted signal between an switch circuit and the antenna unit, the signal path connecting the antenna unit and the diplexer circuit The attenuation pole of the first low-pass filter provided in is set as a frequency in a harmonic band with respect to a communication frequency band of the high-frequency communication system, and provided in a signal path connected to the low-frequency switch circuit in the diplexer circuit. The attenuation pole of the second low-pass filter is a frequency within the communication frequency band of the high-frequency communication system, and is provided in a signal path that connects the low-frequency switch circuit and the transmission circuit of the low-frequency communication system. 3, the attenuation pole of the low pass filter is set to a secondary high frequency with respect to the transmission frequency band of the low frequency side communication system. Characterized by the frequency of the wave band.

  According to the antenna switching module design method of the present invention, it is possible to easily design an antenna switching module that can achieve both attenuation of unnecessary signals and reduction of insertion loss of communication signals.

  In order to further clarify the configuration and operation of the present invention described above, the antenna switching module to which the present invention is applied will be described in the following order.

A. First Example A- (1). Configuration of antenna switching module 10 A- (2). Circuit configuration of antenna switching module 10 A- (3). Filter characteristics of antenna switching module 10 A- (4). Example of equivalent circuit of antenna switching circuit AC1 A- (5). Method for manufacturing antenna switching module 10B. Second Example C.I. Other embodiments

A. First embodiment:
The antenna switching module 10 according to the first embodiment of the present invention is a so-called triple that conforms to three communication systems of EGSM (Extended Global System for Mobile Communications), DCS (Digital Communication System), and PCS (Personal Communication Service). This is a module mounted on a band mobile phone.

A- (1). Configuration of the antenna switching module 10:
The configuration of the antenna switching module 10 will be described. FIG. 1 is a perspective view showing an external structure of the antenna switching module 10. The antenna switching module 10 includes a quadrangular columnar laminated body 100 in which dielectric ceramic layers are laminated, a transmission circuit and a reception circuit of a plurality of communication systems having different communication frequencies in a mobile phone, an antenna unit that transmits and receives communication radio waves, and It is a module implemented between The laminated body 100 is formed with at least a part of an antenna switching circuit AC1 for switching a signal path between a plurality of communication systems and an antenna unit in a cellular phone by a conductor pattern formed in each layer. Note that one side of the laminated surface of the laminated body 100 is about 5 millimeters (hereinafter referred to as mm).

  Various mounting parts such as SAW (Surface Acoustic Wave) filters 121 and 122, a diode 131, a coil 141, and a resistor 151 that form an antenna switching circuit AC1 together with a conductor pattern of each layer are mounted on the uppermost layer surface of the multilayer body 100. Has been. The upper parts of these mounting parts are covered with a shield cap 160 made of a conductive metal soldered to the uppermost surface of the multilayer body 100. The shield cap 160 is connected to the ground via the uppermost surface of the multilayer body 100 when the antenna switching module 10 is mounted.

  FIG. 2 is a bottom view of the antenna switching module 10. In addition to the antenna terminal ANT connected to the antenna unit as various connection terminals on the lowermost layer surface of the laminate 100, as connection terminals related to the EGSM system, there are a transmission terminal TX2 connected to an EGSM system transmission circuit, and an EGSM system. There are provided reception terminals RX2a, RX2b connected to the system reception circuit, and a control terminal VC2 connected to a control circuit for controlling switching of the transmission / reception path of the EGSM system.

  Connection terminals related to the DCS / PCS system are connected to the transmission terminal TX34 connected to the DCS / PCS transmission circuit, the reception terminals RX3a and RX3b connected to the DCS reception circuit, and the PCS reception circuit. Receiving terminals RX4a and RX4b, a control terminal VC34 for controlling switching of ON / OFF of the transmission path of the DCS / PCS system, and a control for controlling switching of ON / OFF of the receiving path of the PCS system. A terminal VC4 is provided.

  When the antenna switching module 10 is mounted between the connection terminal such as the antenna terminal ANT arranged in parallel on one side of the lowermost surface and the connection terminal such as the reception terminal RX4a arranged in parallel on the opposite side, Ground patterns 191, 192, 193, and 194 are provided.

A- (2). Circuit configuration of the antenna switching module 10:
The antenna switching circuit AC1 formed by the antenna switching module 10 will be described. FIG. 3 is a block diagram showing an outline of the antenna switching circuit AC1. The antenna switching circuit AC1 includes a switch circuit SW2 for switching the EGSM signal path, a switch circuit SW34 for switching the DCS / PCS signal path, and each received signal and each transmission to the switch circuits SW2 and SW34. A diplexer circuit DP that performs signal distribution is configured as a main circuit.

  A low-pass filter circuit LPF1 is disposed in a signal path connecting the antenna terminal ANT and the diplexer circuit DP. The low-pass filter circuit LPF1 forms an attenuation pole at “3.495 GHz” that is the center frequency within the second harmonic band (3.42 to 3.57 GHz) with respect to the communication frequency band of the DCS system. Thereby, for example, compared with the case where the attenuation pole is formed at “3.62 GHz” which is the center frequency of the second harmonic band of both the DCS / PCS system, the attenuation pole frequency due to the variation in the filter characteristics of the low-pass filter circuit LPF1 Even if there is a fluctuation, a sufficient attenuation characteristic can be obtained with respect to the low frequency (3.42 GHz) side of the second harmonic band of the DCS system. The signal pass band of the low-pass filter circuit LPF1 is a band through which GSM, DCS, and PCS signals pass, that is, 0.880 to 1.990 GHz.

  The diplexer circuit DP includes a low-pass filter circuit LPF2 disposed on a signal path connected to the switch circuit SW2, and a high-pass filter circuit HPF disposed on a signal path connected to the switch circuit SW34. Both the low-pass filter circuit LPF2 and the high-pass filter circuit HPF are connected to the above-described low-pass filter circuit LPF1 side.

  The low-pass filter circuit LPF2 forms an attenuation pole at “1.7475 GHz” that is the center frequency of the transmission frequency band (1.710 to 1.785 GHz) of the DCS system. The signal pass band of the low-pass filter circuit LPF2 is a band through which an EGSM signal passes, that is, 0.880 to 0.960 GHz. The high pass filter circuit HPF forms an attenuation pole at “0.8975 GHz” which is the center frequency of the transmission frequency band (0.880 to 0.915 GHz) of the EGSM system. The signal pass band of the high-pass filter circuit HPF is a band that allows DCS and PCS signals to pass through, that is, 1.710 to 1.990 GHz.

  A low-pass filter circuit LPF3 is disposed on a signal path connecting the switch circuit SW2 and the transmission terminal TX2. The low-pass filter circuit LPF3 forms an attenuation pole at “1.830 GHz” which is the maximum frequency of the second harmonic band (1.760 to 1.830 GHz) with respect to the transmission frequency band of the EGSM system. The signal pass band of the low-pass filter circuit LPF3 is a band through which an EGSM signal passes, that is, 0.880 to 0.960 GHz.

  Note that the value of the attenuation pole frequency formed by the low-pass filter circuits LPF1, LPF2, LPF3 and the high-pass filter HPF does not have to be strictly the above-described value, and may be in a range of about ± 0.025 GHz of each value. For example, the low-pass filter circuit LPF1 has an attenuation pole frequency in the range of 3.470 to 3.520 GHz, the low-pass filter circuit LPF2 has an attenuation pole frequency in the range of 1.722 to 1.772 GHz, and the low-pass filter circuit LPF3. The attenuation pole frequency may be in the range of 1.805 to 1.855 GHz, and the attenuation pole frequency of the high-pass filter HPF may be in the range of 0.8725 to 0.9225 GHz.

  A SAW filter circuit SAW2 corresponding to the reception frequency band of the EGSM system is disposed in a signal path connecting the switch circuit SW2 and the reception terminals RX2a and RX2b. A SAW filter circuit SAW3 corresponding to the reception frequency band of the DCS system is disposed in a signal path connecting the switch circuit SW34 and the reception terminals RX3a and RX3b. A SAW filter circuit SAW4 corresponding to the reception frequency band of the PCS system is disposed in a signal path connecting the switch circuit SW34 and the reception terminals RX4a and RX4b.

A- (3). Filter characteristics of the antenna switching module 10:
The filter characteristics of the high-pass filter circuit HPF and the low-pass filter circuit LPF2 will be described. FIG. 4 is an explanatory diagram showing an outline of the filter characteristics of the high-pass filter circuit HPF and the low-pass filter circuit LPF2. In the upper part of FIG. 4, the horizontal axis represents frequency, the vertical axis represents insertion loss, and the outline of the filter characteristics of the high-pass filter circuit HPF is indicated by a curve Lhf. In the lower part of FIG. 4, the outline of the filter characteristics of the low-pass filter circuit LPF2 is indicated by a curve Llf2, as in the upper part.

  FIG. 4 shows the filter characteristics when the respective filters are connected as a single circuit instead of connecting the high-pass filter circuit HPF and the low-pass filter circuit LPF2 as the diplexer circuit DP by curves Lhf * and Llf2 *, respectively. Each characteristic shown in FIG. 4 is for explaining the positional relationship between the attenuation poles, and does not accurately indicate the actual insertion loss level.

  The filter characteristic Lhf of the high-pass filter circuit HPF passes through the DCS system communication frequency band (1.710 to 1.880 GHz) and the PCS system communication frequency band (1.850 to 1.990 GHz). The attenuation pole Phf is formed at “.8975 GHz”. The filter characteristic Llf2 of the low-pass filter circuit LPF2 passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and forms the attenuation pole Plf2 at “1.7475 GHz” described above.

  The low-pass filter circuit LPF2 reflects more power energy at frequencies around the attenuation pole Plf2 to the high-pass filter circuit HPF than at other frequencies. Therefore, the high-pass filter circuit HPF passes more signals near this frequency as a result. That is, the filter characteristic Lhf of the high-pass filter circuit HPF that receives the reflected power energy is such that the insertion loss of the frequency around the attenuation pole Plf2 of the low-pass filter circuit LPF2 is smaller than the single filter characteristic Lhf * ( FIG. 4 top). As described above, the frequency (1.7475 GHz) of the attenuation pole Plf2 is the center frequency of the transmission frequency band of the DCS system.

  The high-pass filter circuit HPF reflects the power energy of the frequency around the attenuation pole Phf to the low-pass filter circuit LPF2 more than other frequencies. Therefore, the low-pass filter circuit LPF2 passes more signals near this frequency as a result. That is, the filter characteristic Llf2 of the low-pass filter circuit LPF2 that receives the reflected power energy has a frequency insertion loss around the attenuation pole Phf of the high-pass filter circuit HPF that is smaller than that of the single filter characteristic Llf2 * ( FIG. 4 bottom). As described above, the frequency (0.8975 GHz) of the attenuation pole Phf is the center frequency of the transmission frequency band of the EGSM system.

  A filter characteristic between the transmission terminal TX2 and the antenna terminal ANT will be described. FIG. 5 is an explanatory diagram showing an outline of the filter characteristics between the transmission terminal TX2 and the antenna terminal ANT. At the bottom of FIG. 5, the horizontal axis represents frequency, the vertical axis represents insertion loss, and an outline of the filter characteristics between the transmission terminal TX2 and the antenna terminal ANT is indicated by a curve L (t2-a).

  In the first row in FIG. 5, the horizontal axis represents the frequency and the vertical axis represents the insertion loss, and the outline of the filter characteristics of the low-pass filter circuit LPF1 is indicated by a curve Llf1. In the second stage in FIG. 5, the outline of the filter characteristics of the low-pass filter circuit LPF2 is indicated by a curve Llf2, as in the first stage. In the third stage in FIG. 5, the outline of the filter characteristics of the low-pass filter circuit LPF3 is indicated by a curve Llf3 in the same manner as the first stage. Each characteristic shown in FIG. 5 is for explaining the positional relationship between the attenuation poles, and does not accurately indicate the actual insertion loss level.

  The filter characteristic Llf1 of the low-pass filter circuit LPF1 passes the communication frequency band (0.880 to 1.990 GHz) of the EGSM, DCS, and PCS systems, and forms the attenuation pole Plf1 at “3.495 GHz” described above. The filter characteristic Llf2 of the low-pass filter circuit LPF2 passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and forms the attenuation pole Plf2 at “1.7475 GHz” described above. The filter characteristic Llf3 of the low-pass filter circuit LPF3 passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and forms the attenuation pole Plf3 at “1.830 GHz” described above.

  The input signal input from the transmission terminal TX2 is output from the antenna terminal ANT through the low-pass filter circuit LPF3, the switch circuit SW2, the low-pass filter circuit LPF2 in the diplexer circuit DP, and the low-pass filter circuit LPF1 in this order. In this case, the filter characteristic L (t2-a) between the transmission terminal TX2 and the antenna terminal ANT is a combination of the filter characteristics Llf1, Llf2, and Llf3. The filter characteristic L (t2-a) passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and the second harmonic band (1.760 to 1.830 GHz) with respect to the transmission frequency band of the EGSM system. To form a wide attenuation band, and form an attenuation pole in the second harmonic band (3.42 to 3.57 GHz) with respect to the communication frequency band of the DCS system.

A- (4). An example of an equivalent circuit of the antenna switching circuit AC1:
An example of an equivalent circuit of the antenna switching circuit AC1 formed by the antenna switching module 10 will be described. FIG. 6 is a circuit diagram showing an example of an equivalent circuit of the block diagram of antenna switching circuit AC1 shown in FIG.

  Capacitors C11, C13, and C15 having one side connected to the ground are connected to the low-pass filter circuit LPF1 in order from the antenna terminal ANT side. A capacitor C12 and a coil L12 are connected in parallel between the capacitors C11 and C13, and a capacitor C14 and a coil L14 are connected in parallel between the capacitors C13 and C15, so that a multistage low-pass filter (LC elliptical filter) is connected. Tick filter).

  A coil L21 is connected to the low-pass filter circuit LPF2 on the low-pass filter circuit LPF1 side, and the subsequent stage is connected to the ground via a coil L22 and a capacitor C22, and is configured as an LC filter. Capacitors C25 and C27 are connected in series to the high pass filter circuit HPF in order from the low pass filter circuit LPF1 side. The capacitors C25 and C27 are connected to the ground via a coil L26 and a capacitor C26 and configured as an LC filter.

  In the signal path on the receiving terminal RX2a, RX2b side in the switch circuit SW2, in order from the diplexer circuit DP side, a capacitor C31, one side of which is connected to the grant, a coil L32, and a cathode side are connected to the ground via the capacitor C33. A diode D33 is connected. A control terminal VC2 is connected between the diode D33 and the capacitor C33 via a resistor R34. In order from the diplexer circuit DP side, a diode D35 whose cathode side is connected to the diplexer circuit DP side and a coil L36 whose one side is connected to the ground are connected to the signal path on the transmission terminal TX2 side in the switch circuit SW2. . The switch circuit SW2 switches the signal paths on the reception terminals RX2a, RX2b side and the transmission terminal TX2 side by a control voltage applied to the control terminal VC2.

  A balanced SAW filter circuit SAW2 is connected to the signal path between the switch circuit SW2 and the reception terminals RX2a and RX2b, and a coil L62 is connected between the reception terminals RX2a and RX2b. Note that the SAW filter circuit SAW2 is formed in the SAW filter 121.

  In order from the switch circuit SW2 side, capacitors C41 and C43 whose one side is connected to the ground are connected to the low-pass filter circuit LPF3, and a capacitor C42 and a coil L42 are connected in parallel between the capacitors C41 and C43. It is configured as a low-pass filter (LC elliptic filter).

  A coil L51 is connected in order from the diplexer circuit DP side to the signal path on the receiving terminal RX3a, RX3b side in the switch circuit SW34, and a diode D52 whose cathode side is connected to the ground via a capacitor C53 is connected to the subsequent stage. A resistor R53 having one side connected to the ground is connected between the diode D52 and the capacitor C53. In the signal path on the receiving terminal RX4a, RX4b side in the switch circuit SW34, in order from the diplexer circuit DP side, a diode D54 whose cathode side is connected to the diplexer circuit DP side, a capacitor C54 and a coil L54 are connected in parallel. The stage is connected to a control terminal VC4 via a coil L55. The switch circuit SW34 switches on / off of the signal path on the receiving terminal RX4a, RX4b side by a control voltage applied to the control terminal VC4.

  In the signal path on the transmission terminal TX34 side in the switch circuit SW34, in order from the diplexer circuit DP side, a diode D57 whose cathode side is connected to the diplexer circuit DP side, a capacitor C57, and a coil L57 are connected in parallel. The control terminal VC34 is connected via the coil L58. The switch circuit SW34 switches on / off of the signal path on the transmission terminal TX34 side by a control voltage applied to the control terminal VC34.

  A balanced SAW filter circuit SAW3 is connected to a signal path connecting the switch circuit SW34 and the reception terminals RX3a and RX3b, and a coil L63 is connected between the reception terminals RX3a and RX3b. A balanced SAW filter circuit SAW4 is connected to a signal path connecting the switch circuit SW34 and the reception terminals RX4a and RX4b, and a coil L64 is connected between the reception terminals RX4a and RX4b. The SAW filter circuits SAW3 and SAW4 are formed in the SAW filter 122.

  With these circuit configurations, the antenna switching circuit AC1 is connected between the transmission / reception systems of the three systems EGSM, DCS, and PCS and one antenna unit based on the control voltages of the control terminals VC2, VC34, and VC4. The signal path can be switched.

A- (5). Manufacturing method of antenna switching module 10:
A method for manufacturing the antenna switching module 10 will be described. FIG. 7 is an explanatory diagram showing an outline of the manufacturing process of the antenna switching module 10. When the antenna switching module 10 is manufactured, first, a plurality of green sheets made of a glass ceramic material that can be fired at a low temperature, which is one of dielectric materials, are prepared (step S110). The size of the green sheet is the size of the laminate 100 for a plurality of pieces.

  Thereafter, a through hole for conducting each adjacent layer of the multilayer body 100 and a conductor pattern forming the antenna switching circuit AC1 are formed in each green sheet corresponding to each layer of the multilayer body 100 (step S120). The through hole is formed by making a hole at a location where the through hole is to be formed and then filling the hole with a conductive paste. The conductor pattern is formed by printing a conductor paste. In addition, the material which has silver as a main material is used for the material of the conductor paste of a present Example.

  In this step, conductor patterns to be the various connection terminals and ground patterns 191, 192, 193, 194 shown in FIG. 2 are formed on the green sheet corresponding to the lowermost layer surface of the laminate 100.

  After forming the conductor pattern (step S120), the green sheets on which the conductor patterns of the layers of the multilayer body 100 are formed are stacked in the order of the layers in the multilayer body 100 (step S130), and the stacked green sheets are fired. (Step S140). Thereafter, nickel-gold plating is applied to the conductor pattern appearing on the surface of each laminate 100 in the fired green sheet (step S150), and the mounted components such as the diode 131 and the SAW filter 121 are provided on the uppermost layer surface of each laminate 100. The shield cap 160 is soldered (step S160). Thereafter, the antenna switching module 10 is completed by dividing the laminate 100 into individual pieces (step S170).

  According to the antenna switching module 10 of the first embodiment described above, the harmonics (3.420 to 3.570 GHz) common to the communication frequency bands of the DCS system and the EGSM system due to the arrangement and characteristics of the low-pass filter circuit LPF1. In addition, the frequency at which the insertion loss of the low-pass filter circuit LPF1 rapidly increases can be sufficiently separated from the communication frequency band of the DCS system and the EGSM system, and the insertion loss of the communication signal can be reduced. Further, due to the arrangement and characteristics of the low-pass filter circuit LPF2, on the low-pass filter circuit LPF2 side, an unnecessary signal near the second harmonic with respect to the communication frequency band of the EGSM system is attenuated, and a diplexer circuit coupled to the low-pass filter circuit LPF2 On the high-pass filter circuit HPF side in the DP, it is possible to reduce the insertion loss in the communication frequency band of the DCS system near the attenuation pole frequency. Further, depending on the arrangement and characteristics of the low-pass filter circuit LPF3, together with the low-pass filter circuit LPF2, a wide attenuation band for attenuating the second harmonic with respect to the transmission frequency band of the EGSM system can be secured.

  In addition, the attenuation pole frequency of the low-pass filter circuit LPF1 is a frequency (3.495 GHz) within the second harmonic band with respect to the communication frequency band of the PCS system, and therefore, harmonics having a relatively high level of harmonics are also present. It can be sufficiently attenuated. Further, since the attenuation pole frequency of the low-pass filter circuit LPF2 is the center frequency (1.7475 GHz) of the transmission frequency band of the DCS system, a filter characteristic emphasizing reduction of insertion loss with respect to the transmission signal of the DCS system is obtained. be able to. Further, the attenuation pole frequency of the low-pass filter circuit LPF3 is set to a frequency (1.830 GHz) that corresponds to the attenuation pole frequency (1.7475 GHz) of the low-pass filter circuit LPF2 and is a second harmonic of the maximum transmission frequency of the EGSM system. Therefore, it is possible to secure a sufficient attenuation band for attenuating the second harmonic of the transmission signal of the EGSM system.

  Further, on the low-pass filter circuit LPF2 side in the diplexer circuit DP coupled to the high-pass filter circuit HPF, it is possible to reduce the insertion loss in the communication frequency band of the EGSM system near the attenuation pole frequency. Furthermore, since the attenuation pole frequency of the high-pass filter circuit HPF is the center frequency (0.8975 GHz) of the transmission frequency band of the EGSM system, a filter characteristic that emphasizes the reduction of insertion loss with respect to the transmission signal of the EGSM system is obtained. Can do.

B. Second embodiment:
The antenna switching module 20 according to the second embodiment of the present invention forms an antenna switching circuit AC2 having a circuit configuration similar to that of the antenna switching circuit AC1 shown in FIG. 3, and includes a high-pass filter circuit HPF, a low-pass filter circuit LPF2, The configuration is the same as that of the antenna switching module 10 of the first embodiment except that the attenuation pole frequency of the LPF 3 is different.

  The low-pass filter circuit LPF2 forms an attenuation pole at “1.8425 GHz” which is the center frequency of the reception frequency band (1.805 to 1.880 GHz) of the DCS system. The high pass filter circuit HPF forms an attenuation pole at “0.9425 GHz” which is the center frequency of the reception frequency band (0.925 to 0.960 GHz) of the EGSM system. The low-pass filter circuit LPF3 forms an attenuation pole at “1.760 GHz” which is the minimum frequency of the second harmonic band (1.760 to 1.830 GHz) with respect to the transmission frequency band of the EGSM system.

  Note that the value of the attenuation pole frequency formed by the low-pass filter circuits LPF1, LPF2, LPF3 and the high-pass filter HPF does not have to be strictly the above-described value, and may be in a range of about ± 0.025 GHz of each value. For example, the attenuation pole frequency of the low-pass filter circuit LPF1 is in the range of 3.470 to 3.520 GHz, the attenuation pole frequency of the low-pass filter circuit LPF2 is in the range of 1.817 to 1.867 GHz, and the low-pass filter circuit LPF3 The attenuation pole frequency may be in the range of 1.735 to 1.785 GHz, and the attenuation pole frequency of the high pass filter HPF may be in the range of 0.9175 to 0.9675 GHz.

  The filter characteristics of the high-pass filter circuit HPF and the low-pass filter circuit LPF2 in the second embodiment will be described. FIG. 8 is an explanatory diagram schematically showing the filter characteristics of the high-pass filter circuit HPF and the low-pass filter circuit LPF2 in the second embodiment. In the upper part of FIG. 8, an outline of the filter characteristics of the high-pass filter circuit HPF is indicated by a curve Lhf, with the horizontal axis representing frequency and the vertical axis representing insertion loss. The lower part of FIG. 8 shows the outline of the filter characteristics of the low-pass filter circuit LPF2 by a curve Llf2, as in the upper part.

  In FIG. 8, the filter characteristics in the case where the high-pass filter circuit HPF and the low-pass filter circuit LPF2 are not coupled as the diplexer circuit DP but each filter is connected as a single circuit are shown by curves Lhf * and Llf2 *, respectively. The characteristics shown in FIG. 8 are for explaining the positional relationship between the attenuation poles, and do not accurately indicate the actual insertion loss level.

  The filter characteristic Lhf of the high-pass filter circuit HPF passes through the DCS system communication frequency band (1.710 to 1.880 GHz) and the PCS system communication frequency band (1.850 to 1.990 GHz). The attenuation pole Phf is formed at “.9425 GHz”. The filter characteristic Llf2 of the low-pass filter circuit LPF2 passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and forms the attenuation pole Plf2 at “1.8425 GHz” described above.

  The low-pass filter circuit LPF2 reflects more power energy at frequencies around the attenuation pole Plf2 to the high-pass filter circuit HPF than at other frequencies. Therefore, the high-pass filter circuit HPF passes more signals near this frequency as a result. That is, the filter characteristic Lhf of the high-pass filter circuit HPF that receives the reflected power energy is such that the insertion loss of the frequency around the attenuation pole Plf2 of the low-pass filter circuit LPF2 is smaller than the single filter characteristic Lhf * ( FIG. 8 top). As described above, the frequency (1.8425 GHz) of the attenuation pole Plf2 is the center frequency of the reception frequency band of the DCS system.

  The high-pass filter circuit HPF reflects the power energy of the frequency around the attenuation pole Phf to the low-pass filter circuit LPF2 more than other frequencies. Therefore, the low-pass filter circuit LPF2 passes more signals near this frequency as a result. That is, the filter characteristic Llf2 of the low-pass filter circuit LPF2 that receives the reflected power energy has a frequency insertion loss around the attenuation pole Phf of the high-pass filter circuit HPF that is smaller than that of the single filter characteristic Llf2 * ( FIG. 8 bottom). As described above, the frequency (0.9425 GHz) of the attenuation pole Phf is the center frequency of the reception frequency band of the EGSM system.

  The filter characteristics between the transmission terminal TX2 and the antenna terminal ANT in the second embodiment will be described. FIG. 9 is an explanatory diagram showing an outline of the filter characteristics between the transmission terminal TX2 and the antenna terminal ANT in the second embodiment. In the lowermost stage in FIG. 9, an outline of the filter characteristics between the transmission terminal TX2 and the antenna terminal ANT is indicated by a curve L (t2-a), where the horizontal axis is frequency and the vertical axis is insertion loss.

  In the first row in FIG. 9, the horizontal axis represents the frequency and the vertical axis represents the insertion loss, and the outline of the filter characteristics of the low-pass filter circuit LPF1 is indicated by a curve Llf1. In the second stage in FIG. 9, the outline of the filter characteristics of the low-pass filter circuit LPF2 is indicated by a curve Llf2, as in the first stage. In the third stage in FIG. 9, the outline of the filter characteristics of the low-pass filter circuit LPF3 is indicated by a curve Llf3 in the same manner as the first stage. Each characteristic shown in FIG. 9 is for explaining the positional relationship between the attenuation poles, and does not accurately indicate the actual insertion loss level.

  The filter characteristic Llf1 of the low-pass filter circuit LPF1 passes the communication frequency band (0.880 to 1.990 GHz) of the EGSM, DCS, and PCS systems, and forms the attenuation pole Plf1 at “3.495 GHz” described above. The filter characteristic Llf2 of the low-pass filter circuit LPF2 passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and forms the attenuation pole Plf2 at “1.8425 GHz” described above. The filter characteristic Llf3 of the low-pass filter circuit LPF3 passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and forms the attenuation pole Plf3 at “1.760 GHz” described above.

  The input signal input from the transmission terminal TX2 is output from the antenna terminal ANT through the low-pass filter circuit LPF3, the switch circuit SW2, the low-pass filter circuit LPF2 in the diplexer circuit DP, and the low-pass filter circuit LPF1 in this order. In this case, the filter characteristic L (t2-a) between the transmission terminal TX2 and the antenna terminal ANT is a combination of the filter characteristics Llf1, Llf2, and Llf3. The filter characteristic L (t2-a) passes the communication frequency band (0.880 to 0.960 GHz) of the EGSM system, and the second harmonic band (1.760 to 1.830 GHz) with respect to the transmission frequency band of the EGSM system. To form a wide attenuation band, and form an attenuation pole in the second harmonic band (3.42 to 3.57 GHz) with respect to the communication frequency band of the DCS system.

  According to the antenna switching module 20 of the second embodiment described above, the attenuation pole frequency of the low-pass filter circuit LPF2 is the center frequency (1.8425 GHz) of the reception frequency band of the DCS system. As a result, it is possible to obtain filter characteristics that emphasize reduction of insertion loss. Further, the attenuation pole frequency of the low-pass filter circuit LPF3 is set to a frequency (1.760 GHz) that corresponds to the attenuation pole frequency (1.8425 GHz) of the low-pass filter circuit LPF2 and is a second harmonic of the minimum transmission frequency of the EGSM system. Therefore, it is possible to secure a sufficient attenuation band for attenuating the second harmonic of the transmission signal of the EGSM system. Further, since the attenuation pole frequency of the high-pass filter circuit HPF is the center frequency (0.9425 GHz) of the reception frequency band of the EGSM system, a filter characteristic that emphasizes the reduction of insertion loss with respect to the reception signal of the EGSM system is obtained. Can do.

C. Other embodiments:
As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, it can implement with various forms within the range which does not deviate from the meaning of this invention. is there. For example, instead of the switch circuit SW34 of the antenna switching circuit AC1, a switch circuit SWtr for switching the signal path between the transmission system and the reception system in the DCS / PCS system, as in the antenna switching circuit AC3 shown in FIG. A switch circuit SWr that switches a signal path between the DCS system and the PCS system of the reception system may be provided. Further, instead of the switch circuit SW34 of the antenna switching circuit AC1, a switch circuit SW3 for switching a DCS signal path is provided as in the antenna switching circuit AC4 shown in FIG. 11, and two communication systems of EGSM and DCS are provided. The present invention may be applied to an antenna switching module mounted on a compliant so-called dual-band mobile phone. Further, the switch circuit SW2 may be applied to an antenna switching module that is a switch circuit that switches a signal path of a GSM850 (Global System for Mobile Communications 850) system in addition to the EGSM system.

1 is a perspective view showing an external structure of an antenna switching module 10. FIG. 4 is a bottom view of the antenna switching module 10. FIG. It is a block diagram which shows the outline of antenna switching circuit AC1. It is explanatory drawing which shows the outline of the filter characteristic of the high-pass filter circuit HPF and the low-pass filter circuit LPF2. It is explanatory drawing which shows the outline of the filter characteristic between transmission terminal TX2 and antenna terminal ANT. FIG. 4 is a circuit diagram illustrating an example of an equivalent circuit of the block diagram of the antenna switching circuit AC1 illustrated in FIG. 3. 4 is an explanatory diagram showing an outline of a manufacturing process of the antenna switching module 10. FIG. It is explanatory drawing which shows the outline of the filter characteristic of the high pass filter circuit HPF and low-pass filter circuit LPF2 in a 2nd Example. It is explanatory drawing which shows the outline of the filter characteristic between transmission terminal TX2 in 2nd Example, and antenna terminal ANT. It is a block diagram which shows the outline of antenna switching circuit AC3. It is a block diagram which shows the outline of antenna switching circuit AC4.

Explanation of symbols

10, 20 ... Antenna switching module 100 ... Laminated body 121, 122 ... SAW filter 131 ... Diode 141 ... Coil 151 ... Resistor 160 ... Shield cap 191, 192, 193 , 194 ... ground pattern AC1, AC2, AC3, AC4 ... antenna switching circuit ANT ... antenna terminal TX2, TX3, TX34 ... transmission terminal VC2, VC34, VC4 ... control terminal RX2-4a, RX2-4b ... Reception terminal DP ... Diplexer circuit SW2, SW34, SWtr, SWr ... Switch circuit HPF ... High pass filter circuit LPF1, LPF2, LPF3 ... Low pass filter circuit SAW2, SAW3, SAW4. ..SAW filter circuit

Claims (12)

A dielectric ceramic layer is laminated on at least a part of an antenna switching circuit for switching a signal path between a transmission circuit and a reception circuit of a plurality of communication systems having different communication frequency bands and an antenna unit for transmitting and receiving communication radio waves. An antenna switching module formed in the laminated body,
The antenna switching circuit is
A low frequency side switch circuit for switching the signal path for a low frequency side communication system using a relatively low communication frequency band among the plurality of communication systems;
A high frequency side switch circuit for switching the signal path for a high frequency side communication system using a communication frequency band near the second harmonic of the communication frequency of the low frequency side communication system among the plurality of communication systems;
A diplexer circuit that distributes each received signal and each transmitted signal between the low frequency side switch circuit and the high frequency side switch circuit and the antenna unit, and
A signal path connecting the antenna unit and the diplexer circuit is provided with a first low-pass filter that forms an attenuation pole at a frequency within a harmonic band with respect to a communication frequency band of the high-frequency communication system,
In the signal path connected to the low frequency side switch circuit in the diplexer circuit, a second low-pass filter that forms an attenuation pole at a frequency within the communication frequency band of the high frequency side communication system is disposed,
An attenuation pole is formed at a frequency within a second harmonic band with respect to a transmission frequency band of the low frequency communication system in a signal path connecting the low frequency switch circuit and the transmission circuit of the low frequency communication system. Antenna switching module with 3 low-pass filters.   The antenna switching module according to claim 1, wherein the attenuation pole frequency of the first low-pass filter is a frequency within a second harmonic band with respect to a communication frequency band of the high-frequency communication system.   The antenna switching module according to claim 1 or 2, wherein the attenuation pole frequency of the second low-pass filter is a center frequency of a transmission frequency band or a reception frequency band of the high-frequency communication system. The antenna switching module according to any one of claims 1 to 3,
The attenuation pole frequency of the third low-pass filter is created between the attenuation pole frequency of the second low-pass filter out of the maximum transmission frequency of the low-frequency side communication system or a frequency that is twice the minimum transmission frequency. The antenna switching module, wherein the frequency band is one frequency that overlaps more widely with respect to the second harmonic band with respect to the transmission frequency band of the low frequency side communication system.   The high-pass filter which forms an attenuation pole in the frequency within the communication frequency band of the said low frequency side communication system is arrange | positioned in the signal path | route connected to the said high frequency side switch circuit in the said diplexer circuit. The antenna switching module described.   The antenna switching module according to claim 5, wherein the attenuation pole frequency of the high-pass filter is a center frequency of a transmission frequency band or a reception frequency band of the low-frequency communication system. The antenna switching module according to any one of claims 1 to 6,
The low frequency side switch circuit performs switching of the signal path to the low frequency side communication system in accordance with at least one of GSM850 system or EGSM system,
The high frequency side switch circuit performs switching of the signal path with respect to the high frequency side communication system based on at least one of a DCS system or a PCS system. The antenna switching module according to any one of claims 1 to 7,
The high frequency side switch circuit is:
One diplex support connected to the diplexer circuit;
One transmission port connected to a transmission circuit of a predetermined high-frequency communication system;
An antenna switching module comprising: one reception port connected to a reception circuit of the predetermined high frequency side communication system. The antenna switching module according to any one of claims 1 to 7,
The high frequency side switch circuit is:
One diplex support connected to the diplexer circuit;
One transmission port connected in common to each transmission circuit of two different high-frequency communication systems;
An antenna switching module comprising: two reception ports respectively connected to the reception circuits of the two different high-frequency communication systems. The antenna switching module according to claim 1,
The low frequency side switch circuit performs switching of the signal path for the low frequency side communication system compliant with the EGSM system,
The high frequency side switch circuit performs switching of the signal path for the high frequency side communication system compliant with a DCS system,
The attenuation pole frequency of the first low-pass filter is 3.42 to 3.57 GHz,
The attenuation pole frequency of the second low-pass filter is 1.72 to 1.78 gigahertz,
The attenuation pole frequency of the third low-pass filter is 1.80 to 1.86 GHz. Antenna switching module. The antenna switching module according to claim 1,
The low frequency side switch circuit performs switching of the signal path for the low frequency side communication system compliant with the EGSM system,
The high frequency side switch circuit performs switching of the signal path for the high frequency side communication system compliant with a DCS system,
The attenuation pole frequency of the first low-pass filter is 3.42 to 3.57 GHz,
The attenuation pole frequency of the second low-pass filter is 1.81-1.87 GHz,
The antenna switching module, wherein the attenuation pole frequency of the third low-pass filter is 1.73 to 1.79 gigahertz. A dielectric ceramic layer is laminated on at least a part of an antenna switching circuit for switching a signal path between a transmission circuit and a reception circuit of a plurality of communication systems having different communication frequency bands and an antenna unit for transmitting and receiving communication radio waves. Formed into a laminated body,
The antenna switching circuit is
A low frequency side switch circuit for switching the signal path for a low frequency side communication system using a relatively low communication frequency band among the plurality of communication systems;
A high frequency side switch circuit for switching the signal path for a high frequency side communication system using a communication frequency band near the second harmonic of the communication frequency of the low frequency side communication system among the plurality of communication systems;
A diplexer circuit for distributing each reception signal and each transmission signal between the low frequency side switch circuit and the high frequency side switch circuit and the antenna unit, and a design method of an antenna switching module,
The attenuation pole of the first low-pass filter provided in the signal path connecting the antenna unit and the diplexer circuit is a frequency within a harmonic band with respect to the communication frequency band of the high-frequency communication system,
The attenuation pole of the second low-pass filter provided in the signal path connected to the low frequency side switch circuit in the diplexer circuit is a frequency within the communication frequency band of the high frequency side communication system,
An attenuation pole of a third low-pass filter provided in a signal path connecting the low frequency side switch circuit and the transmission circuit of the low frequency side communication system is a second harmonic with respect to the transmission frequency band of the low frequency side communication system. A method for designing an antenna switching module with a frequency within the band.

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