JP2003198204A - High frequency module - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a high-frequency module capable of accurately measuring a pass band characteristic in a mounted state when a SAW filter arranged in an antenna switching circuit is mounted. A high-frequency module in which a SAW filter is mounted on a dielectric substrate and a strip line and a switching diode are connected to the SAW filter, the electrode pad having a switching diode mounted thereon.
The electrode pad 3a on the side connected to the SAW filter sf among the electrodes a and 3b is arranged such that the first connection portion 31 and the second connection portion 32 are divided.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency module provided with an antenna circuit used for communication equipment. 2. Description of the Related Art Generally, a mobile communication device represented by a portable telephone supplies an antenna switching signal for supplying a signal received from an antenna to a receiving circuit and supplying a transmission signal from the transmitting circuit to the antenna. It has a circuit. Such an antenna circuit is treated as a high-frequency module in which a predetermined wiring pattern is formed on a dielectric substrate, a strip line is formed, and a switching diode, a SAW filter, and a DC limiting capacitor are mounted. In addition, other than the above-described antenna switching circuit, the high frequency module is configured by mounting all or a part of the receiving circuit and all or a part of the transmitting circuit at the same time. For example, a high-frequency module provided with an antenna switching circuit is formed using a dielectric substrate on which an antenna terminal, a reception terminal, a transmission terminal, a control terminal, and a ground terminal are formed. The functions of the receiving terminal and the transmitting terminal change depending on the configuration of the high-frequency module.
When an antenna switching circuit is simply formed on a dielectric substrate, an antenna is connected to the antenna terminal, a receiving circuit is connected to the receiving terminal, and a transmitting circuit is connected to the transmitting terminal. [0004] Such an antenna switching circuit is shown in FIG.
As shown in (1), a switching diode D1 and a capacitor C5 are arranged between the antenna terminal ANT and the transmission terminal TX via a DC limiting capacitor C1. Note that the cathode side of the switching diode D1 is on the antenna terminal ANT side. The strip lines SL and SAW are provided between the antenna terminal ANT and the receiving terminal RX through the DC limiting capacitor C1 described above.
The filter sf and the capacitors C3 and C3 are arranged. [0005] A switching diode D and a capacitor C4 are arranged between a connection point X between the strip line SL and the SAW filter sf and a ground potential. Further, an inductance element L and a capacitor C6 are arranged between the anode of the switching diode D1 and the ground potential, and a bias current is applied to the two switching diodes D1 and D between the inductance element L and the capacitor C6. A control terminal CONT to be supplied is arranged. Here, the strip line SL has a line length of １ ／ with respect to the wavelength λ of the center frequency of the signal that is not desired to be derived from the reception terminal RX, for example, the transmission signal.
Further, the SAW filter sf selectively extracts only a signal of a predetermined frequency from a reception signal derived to a reception circuit. The capacitors C1 to C6 are DC limiting capacitors for enabling a signal (bias current) supplied to the control terminal CONT to be supplied to the switching diodes D1 and D stably. Further, a coil L is arranged between the capacitor C2 and the capacitor C3.
This prevents interference of received signals between the two receiving terminals RX1 and RX2. In such a switching circuit, for example, when conduction is established between the antenna terminal ANT and the transmission terminal TX, a signal for turning on the switching diodes D1 and D is supplied to the control terminal CONT. As a result, the switching diode D1 is turned on, and at the same time, the switching diode D is turned on. When the switching diode D is turned on, one end of the strip line SL is short-circuited via the capacitor C4.
For example, it operates with a short stub for a transmission signal. That is, the transmission signal is blocked by the strip line SL and is prevented from flowing to the reception terminals RX1 and RX2.
As a result, the transmission signal can be connected between the antenna terminal ANT and the transmission terminal TX without attenuation. When a signal for turning off the switching diodes D1 and D is supplied to the control terminal CONT, the switching diode D1 is turned off and the connection between the antenna terminal ANT and the transmission terminal TX is cut off. . Then, the strip line SL operates as a mere transmission line, and the received signal supplied from the antenna terminal ANT extracts only a predetermined frequency component by the SAW filter sf via the strip line SL,
It will be connected to the receiving terminals RX1 and RX2. For example, when processing received signals of two reception frequencies,
Two SAW filters sf are required, and each
Since it is necessary to design so as not to interfere with the filter characteristics of the filter sf, as one of the designs, the constant of the phase matching circuit in which the phase matching circuit is added to each SAW filter is different from the center frequency of the SAW filter. The characteristic impedance of the filter and the characteristic impedance of the phase matching circuit are designed to be approximately 50 ohms near these center frequencies. These characteristic impedances are designed to suppress the interference by utilizing the fact that the impedance of the transmission line can be matched at the frequency to be passed and cannot be matched at other frequencies. In some cases, an inductance element or a capacitor element is used for these phase circuits. However, miniaturization has been proposed in which an LC component is formed using a microstrip line, and the inner layer is formed on a laminated substrate. These high-frequency modules use, for example, a laminated substrate on which a dielectric layer is laminated, and have an internal capacitor electrode forming a capacitor of each circuit and an inductor conductor forming a strip line SL inside the dielectric layer. An internal wiring layer including a film and a via-hole conductor connecting these elements is formed. On the surface of the laminated substrate, there are a switching diode and a resistor mounted on the surface of the substrate, and a capacitor which is difficult to be mounted inside the substrate. Then, a surface wiring conductor layer including an electrode pad for connecting and mounting each of these elements is formed. In forming this surface wiring layer, strip lines and external terminals are simultaneously formed as necessary. [0010] In the manufacturing process, a laminated substrate is formed in which the conductors, electrodes, and internal wiring layers, which become the respective elements, are formed inside, and a surface wiring layer is formed on the surface. Then, each electronic component element is formed by soldering and mounting on an electrode pad on the surface. The mounted electronic component element is a SAW filter. To reduce the size of the high-frequency module as a whole, a cavity is formed in a laminated substrate, and a chip of the SAW filter (an IDT electrode is formed on a piezoelectric substrate). Was accommodated in a cavity, and the cavity was sealed with a lid. However, in a SAW filter mounted on such a high-frequency module, the S
The pass band characteristics before mounting the AW filter can be measured relatively easily. However, when mounted on a dielectric substrate, for example, when a SAW filter element is mounted on a laminated substrate, the SAW filter element is immediately connected directly to the strip line SL via the surface wiring layer. That is, the electrical characteristics of the SAW filter sf after mounting are different from those of other mounted components and the strip line SL.
And the pattern of the surface wiring layer becomes a stub, and there is a problem that the pass band characteristic in a mounted state of the SAW filter cannot be measured accurately. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a high-frequency module capable of accurately measuring a pass band characteristic of a mounted SAW filter and guaranteeing the pass band characteristic. Is to provide. According to the present invention, an antenna terminal connected to an antenna, a reception terminal connected to a reception circuit, and a transmission terminal connected to a transmission circuit are formed on a dielectric substrate.
A capacitor, a strip line, a SAW filter between the antenna terminal and the reception terminal from the antenna terminal side,
In a high-frequency module in which capacitors are sequentially arranged and a switching diode is arranged between a connection point between the strip line and the SAW filter and a ground potential, the strip line is provided on a surface of the dielectric substrate. An electrode pad connected to a SAW filter and connected to one terminal electrode of the switching diode; a first connection portion to which the strip line is connected;
A second connection part to which a filter is connected, and one terminal electrode of the switching diode is connected to the first terminal.
And a second high frequency module. According to the present invention, the switching diode connected to the connection point between the strip line and the SAW filter has one terminal electrode of the switching diode at the connection point (before the SAW filter) connected to the first terminal.
And a second connection portion. That is, the SAW filter is connected to, for example, only one connection portion, that is, only the first connection portion. When the SAW filter is mounted, the SAW filter is electrically connected to the strip line SL and the internal wiring layer. Not. Therefore, when the SAW filter is mounted and the passband characteristic of the SAW filter is measured using the first connection unit, the passband characteristic of the mounted SAW filter can be accurately measured. The output side of the SAW filter, that is, the output terminal, is measured using a capacitor mounting electrode pad before mounting a capacitor to be connected thereafter. In mounting the switching diode, the other terminal of the switching diode is connected to an electrode pad which is at a ground potential. The one terminal is joined so as to straddle the first connection portion and the second connection portion. Thus, the SAW filter is connected to the switching diode and to the strip line. As described above, the pass band characteristics of the mounted SAW filter can be easily measured immediately after the SAW filter is mounted on the laminated substrate, and therefore, the SAW filter can be replaced during the manufacturing process. Since the characteristics of the SAW filter can be adjusted, it is not necessary to discard the high-frequency module on which all the mounted components are mounted. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a high-frequency module according to the present invention will be described in detail with reference to the drawings. FIG. 1 is an external perspective view of the high-frequency module of the present invention in a state where a shield case is omitted, FIG. 2 is a cross-sectional view of the high-frequency module of the present invention, and FIG. FIG. 10 is a high-frequency module, and the high-frequency module 10 is a laminated substrate 1 that is a dielectric substrate.
1, a surface wiring layer 12, a mounted component 13, and a terminal electrode 14. Further, a cavity 15 for accommodating a SAW filter 16 (sf in the circuit diagram of FIG. 4) is formed in the laminated substrate 11, for example, two SAW filters 16 are accommodated in the cavity 15, It is sealed. The internal wiring layer 2 is provided inside the multilayer substrate 11.
0 and via-hole conductors 21 are formed. Other circuits including the antenna switching circuit shown in FIG. 4, for example, are mounted on such a high-frequency module 10. Other circuits are all or a part of a receiving circuit, all or a part of a transmitting circuit, an oscillating circuit for generating a local oscillation signal, and an LC filter circuit for cutting off high-frequency noise. Or In addition, all or part of these circuits become integrated circuits and become part of the mounting component 13. Further, a plurality of terminal electrodes 14 shown on the laminated substrate 11 are formed. The terminal electrode 14 includes an antenna terminal connected to an antenna, a reception terminal connected to a reception circuit, and a transmission terminal connected to a transmission circuit. (A reception terminal is a transmission terminal. If they are integrated, they will be input and output terminals), a ground terminal connected to ground potential,
These are control terminals for performing a predetermined operation of the mounted circuit. The mounting components 13 include switching diodes, capacitors, resistors, coils, and the like.
Although the SAW filter 16 is housed in the cavity 15 of the multilayer substrate 1 in the drawing, the SAW filter 16 is distinguished from the mounting component 13 mounted on the surface of the multilayer substrate 11.
The filter may be mounted on the surface of the laminated substrate 11 and handled as a mounted component. The surface wiring layer 12 of the laminated substrate 11
It is a wiring constituting a predetermined circuit, includes a part of a terminal electrode and an electrode pad, and is constituted by a strip line and an inductor conductor formed on the surface. Internal wiring layer 20 formed on laminated substrate 11
Is a wiring constituting a predetermined circuit and, if necessary, is constituted by a strip line and a capacitor electrode constituting a capacitor. In addition, the via-hole conductor 21 is a wiring that forms a predetermined circuit in the thickness direction of the substrate, and may be configured as a part of the inductor conductor using a predetermined inductance component. Here, the S accommodated in the cavity 15
The AW filter 16 is electrically and mechanically connected to an electrode pad formed on the bottom surface of the cavity 15, and this electrode pad serves as an internal wiring layer and a via-hole conductor inside the laminated substrate 11. Derived to the surface. This derived conductor is indicated by reference numeral 19. The mounting component 13, the SAW filter 16, the internal wiring layer 10, the surface wiring layer 12, and the internal wiring layer 1
0 or a strip line SL included in the surface wiring layer 12
Thereby, the antenna switching circuit of FIG. 4 is configured. Here, the SAW filter 16 is a filter excellent in pass band characteristics, that is, excellent in frequency selection, and is very important in extracting the reception frequency in the communication system on the reception side of the antenna switching circuit. Parts. However, since the frequency selection characteristic is very good, the characteristic greatly varies depending on the pattern of the surrounding surface wiring layer connected to the SAW filter 16 and the parasitic inductance component of the strip line. That is, even if the characteristics are satisfied by the SAW filter alone (before mounting), the characteristics fluctuate due to the effect of the wiring layer pattern and the strip line when actually mounted on the multilayer substrate 11. The electrode at the connection point X with the strip line SL, that is, the connection point X with the switching diode D, which is one of the mounted components 13, is located at the preceding stage of the SAW filter sf of the antenna switching circuit in which this factor is most serious. The structure of the pad is improved so that the pass band characteristics of the mounted state of the SAW fill sf can be accurately measured. More specifically, as shown in FIG.
In the pair of electrode pads 3a and 3b on which the switching diode D is mounted, one of the electrode pads 3a is connected to, for example, the first connecting portion 31 to which the anode terminal electrode of the switching diode D is connected. And two connecting portions 32. The other electrode pad 3b is an electrode pad to which the cathode terminal electrode is connected, and is a single mounting area. For example, the first connection part 31 constituting one electrode pad 3 a is connected to the lead conductor 19 led out to the surface of the laminated substrate 11. That is, it is connected to the SAW filter 16. Although not shown in FIG. 3, the second connection unit 32 is connected to the strip line SL. Although not shown in FIG. 3, the other electrode pad 3b is connected to a resistor R or a capacitor as it is, and then connected to a wiring layer serving as a ground potential or a terminal electrode 14 having a ground potential. Although solder is omitted in FIG. 3,
The anode end of the switching diode D is joined across the first connection portion 31 and the second connection portion 32. Accordingly, the SAW filter 16 can be connected to the strip line SL and simultaneously to the anode of the switching diode D. With such a structure, the SAW filter 16 is housed in the cavity 15 (the mounting component 1).
3 in a state in which the switching diode is not mounted), since the SAW filter 16 and the strip line SL formed on the laminated substrate 11 are electrically separated from each other, the first connection portion 31 must be used. Accordingly, the pass band characteristics of the mounted SAW filter 16 can be accurately measured. When measuring the characteristics of the mounted state of the SAW filter 16, the first connecting portion 31 on the strip line SL side of the SAW filter 16 as described above.
Is used. On the receiving circuit side of the SAW filter 16, for example, when one of the capacitor electrode pads to which a capacitor is connected is connected via the surface wiring layer 12, one of the capacitor electrode pads is used for measurement. What is necessary is just to measure using it as an electrode. In the above-described embodiment, the description has been given of the high-frequency module having the antenna switching circuit. However, depending on the mode of the antenna switching circuit (by using the switching diode in the reverse direction and supplying the bioelectric current from the receiving circuit side). It can be changed as appropriate. Further, regarding the configuration of the SAW filter,
In the figure, two SAW filters each having a balanced output type interdigital electrode formed on a lithium tantalate single crystal substrate are arranged in parallel in the cavity 15. The number may be one element. According to the present invention, the pass band characteristics of the SAW filter can be changed even after the SAW filter is mounted.
It can measure accurately without being affected by the stripline, surface wiring layer, and internal wiring layer formed on the laminated substrate, and
It becomes possible to adjust the pass band characteristics during the manufacturing process, replace the SAW filter, etc., and to achieve a high-frequency module with stable operation and reduced manufacturing cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a high-frequency module of the present invention with a shield case omitted. FIG. 2 is a schematic sectional view of a high-frequency module according to the present invention. FIG. 3 is a partial plan view showing a surface wiring layer of a switching diode portion of the laminated substrate of the present invention. FIG. 4 is a circuit diagram showing a part of a general antenna circuit. [Description of Signs] 10 High-frequency module 11 Laminated substrate 12 Surface wiring layer 13 Mounting component 14 Terminal electrode 15 Cavity 16, sf SAW filter SL Strip line D Switching diode C Capacitor R Resistance

Claims (1)

Claims: 1. An antenna terminal connected to an antenna, a reception terminal connected to a reception circuit, and a transmission terminal connected to a transmission circuit are formed on a dielectric substrate, and the antenna terminal and the reception terminal are connected to each other. A high-frequency module in which a capacitor, a strip line, a SAW filter, and a capacitor are sequentially arranged from the antenna terminal side, and a switching diode is arranged between a connection point between the strip line and the SAW filter and a ground potential. In the above, the strip line and the SA are provided on the surface of the dielectric substrate.
An electrode pad connected to a W filter and connected to one terminal electrode of the switching diode, the electrode pad being connected to a first connection portion to which the strip line is connected; And a second connection portion to which the switching diode is connected, and one terminal electrode of the switching diode is joined so as to straddle the first and second connection portions. module.