JP2008060169A - High-frequency power amplifier and communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an influence of undesired radiation in a high-frequency power amplifier using a resin cap and a communication terminal using the amplifier. <P>SOLUTION: The high-frequency power amplifier for amplifying high-frequency signals includes a substrate 31, an amplifying element 33 located on the substrate 31, and the resin cap 36 with a magnetic material mixed in a shape for covering the substrate on which the element 33 is provided. A magnetic field generated by the element 33 is absorbed by the magnetic material in the cap 36. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency power amplifier suitable for application to, for example, an amplifier included in a mobile phone terminal, and a communication terminal such as a mobile phone terminal including the high-frequency power amplifier, and more particularly to a technique for reducing unnecessary radiation.

  Since a transmitter (transmitter) included in a wireless communication terminal such as a mobile phone terminal needs to wirelessly transmit a large output signal of several hundred mW to several W, a high frequency power amplifier is used to amplify the transmission signal. . A high-frequency power amplifier has an integrated chip shape, and a metal cap, which is a lid member made of a metal plate, is conventionally attached to the surface of the chip-shaped high-frequency power amplifier. The configuration is such that the power amplifier does not radiate outside.

  However, a metal cap made of a metal plate has a relatively high manufacturing cost for components, so that a resin cap having a lid member made of resin is used as a high frequency power amplifier, thereby reducing the manufacturing cost of the high frequency power amplifier. What has been put into practical use. Even when a power amplifier using a resin cap is used, a shield case made of a metal plate or the like is placed on the circuit board on which the power amplifier is placed. The structure is not radiated.

Patent Document 1 has a description of an example of a shield structure that suppresses unnecessary radiation of an electronic device. In the example described in Patent Document 1, it is described that a separate component (magnetic core) that suppresses unnecessary radiation is arranged in a shield case to suppress unnecessary radiation.
JP 10-163665 A

  When using a power amplifier with a resin cap, even though the shield case can prevent unwanted radiation from radiating to the outside, there is a problem that the effect of unwanted radiation on other parts placed in the seal case is significant. It was. That is, in the case of a power amplifier using a conventional metal cap, the unnecessary radiation level from the power amplifier itself is sufficiently small, and there is almost no problem. On the other hand, in the case of a power amplifier using a resin cap, unnecessary radiation is emitted into the shield case through the resin cap, and a high-frequency current is generated.

  FIG. 12 is a cross-sectional view showing an example in which a power amplifier using a conventional resin cap is arranged inside a shield case. A high-frequency power amplifier 91, a high-frequency transmission unit 92, and the like are disposed on the circuit board 90. The circuit board 90 is covered with a metal shield case 94 so as to cover the high-frequency power amplifier 91 and the high-frequency transmission unit 92. As a configuration.

  Here, the high frequency power amplifier 91 using a resin cap has a configuration in which a surface mount device 91b is attached on an organic substrate 91a made of ceramic or the like, and a resin cap 91c is further disposed thereon. What is indicated by an arrow in FIG. 12 is an example of a magnetic field distribution generated at the time of power amplification in the surface mount device 91b disposed on the organic substrate 91a. Thus, a magnetic field is generated inside the shield case. The generation of the magnetic field by the high-frequency power amplifier occurs because the amplifier 91 does not use a metal cap but uses a resin cap. When there is a magnetic field distribution as shown in FIG. 12, a high-frequency current flowing through the metal shield case 94 is generated as shown by an arrow as shown in FIG. 13 with the metal shield case attached.

  When such a high-frequency current is generated, there is a problem that the characteristics of other circuit components in the shield case are affected and the characteristics of the transmission signal are deteriorated. In order to solve this problem, for example, it is conceivable that the power amplifier and other circuit components (devices) are separately covered with a shield case. In this case, however, the mounting area on the circuit board is considered. This was disadvantageous for downsizing the equipment.

  Further, by increasing the height of the shield case and increasing the distance between the upper surface of the power amplifier and the inner surface of the shield case, the structure shown in FIG. Although it is possible, the thickness of the entire transmitter including the shield case will increase, which will hinder the thinning of the device. In particular, in the case of a communication terminal such as a mobile phone terminal, miniaturization and thinning have been demanded, and miniaturization of a shield case for housing a power amplifier has been demanded. Further, as described in Patent Document 1, when a magnetic core or the like is arranged in a shield case to suppress unnecessary radiation, the number of necessary parts increases and a metal cap is omitted as a power amplifier. As a result, the point of reducing the manufacturing cost is offset and the manufacturing cost is increased.

  The present invention has been made in view of this point, and an object thereof is to reduce the influence of unnecessary radiation in a high-frequency power amplifier using a resin cap and a communication terminal using the high-frequency power amplifier.

  The present invention relates to a high frequency power amplifier that amplifies a high frequency signal, and a resin cap in which a magnetic material is mixed in a shape that covers a substrate, an amplification element disposed on the substrate, and a substrate on which the amplification element is disposed. It is set as the structure provided with.

  By doing in this way, it acts so that the high frequency magnetic field as unnecessary radiation generated from the device constituting the high frequency power amplification unit is absorbed by the magnetic material mixed in the resin cap, and from the high frequency power amplification unit to the substrate Electromagnetic waves radiated to other circuit components such as the upper high-frequency transmitter can be reduced.

  According to the present invention, the unnecessary radiation from the high frequency power amplifier can be absorbed by the magnetic material mixed in the resin cap, and the unnecessary radiation can be effectively reduced. Therefore, for example, by amplifying the transmission signal by the high frequency power amplification unit, unnecessary radiation to the circuit components around the high frequency power amplification unit can be reduced, and deterioration of communication quality can be reduced. Therefore, even when an amplifier using a resin cap is used as the high-frequency power amplifier, good characteristics similar to those when a metal cap is used are ensured.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In this embodiment, the present invention is applied to a transmission signal processing circuit provided in a mobile phone terminal. The transmission signal is, for example, a high-frequency signal having a transmission frequency of about several hundred MHz to several GHz.

  1 and 2 are diagrams showing a configuration of a high-frequency power amplifier according to the present embodiment. FIG. 1 is a cross-sectional view, FIG. 2 is an exploded perspective view, and FIG. 1 is taken along a line II in FIG. The cross section along is shown in an assembled state. The high-frequency power amplifier 30 in the present embodiment is used by being mounted on a circuit board as will be described later, and is configured on an organic substrate 31 such as ceramic.

  A concave portion 32 is formed in the center of the organic substrate 31, and a field effect transistor (FET) 33 that is an amplifying element is disposed in the concave portion 32. Further, other chip components 34 necessary as a high frequency power amplifier are arranged around the recess 32. The field effect transistor 33 is connected to other circuit components by a wire 35.

  In this example, the magnetic material mixed resin cap 36 is disposed on the upper surface of the organic substrate 31 on which the field effect transistor 33 and the like are disposed. In the space between the inner surface 37 of the magnetic material mixed resin cap 36 and the upper surface of the organic substrate 31, a field effect transistor 33, a chip component 34, and the like are disposed.

  The magnetic body mixed resin cap 36 is formed of a resin mixed with a magnetic material. As the magnetic material to be mixed, it is preferable to use a magnetic material having almost no electrical conductivity, such as ferrite, and the high frequency magnetic field is concentrated and absorbed by the action of the mixed magnetic material. For example, a carbon-based resin is used as the resin. Details of the action of the magnetic material will be described later.

  Next, a configuration example of a communication terminal in which the high frequency power amplifier according to the present embodiment is arranged will be described with reference to FIG. The high frequency power amplifier 30 of this example is disposed on a hard circuit board 10 as shown in FIG. In this example, the high-frequency transmitter 12 and the high-frequency power amplifier 30 are arranged on one circuit board 10. The high-frequency transmission unit 12 is a component in which a circuit that generates a high-frequency transmission signal having a frequency to be transmitted is configured, and the high-frequency power amplifier 30 configured as a high-frequency power amplification unit uses the high-frequency transmission signal output from the high-frequency transmission unit 12. To perform high-frequency power amplification. In the high frequency power amplifier 30, for example, amplification with a large output signal of several hundred mW to several W is performed. A signal line 13 is connected to the high frequency transmitter 12.

  Then, a shield case 20 made of a conductive member such as metal is disposed on the circuit board 10 on which the high-frequency power amplifier 30 and the high-frequency transmitter 12 are disposed. In this example, as shown in FIG. 3, the shield case 20 has a size substantially the same as that of the circuit board 10 and covers the entire surface of the circuit board 10. The configuration is in contact with the 20 side surfaces. Circuit components such as the high-frequency power amplifier 30 and the high-frequency transmitter 12 are accommodated in a space formed between the inner surface of the shield case 20 and the surface of the circuit board 10.

  In the assembled state, the shield case 20 is configured to be electrically connected to the ground potential portion of the circuit board 10 and shield with the ground potential.

  In FIG. 3, circuit components other than the high-frequency power amplifier 30 and the high-frequency transmitter 12 are omitted. For example, a high-frequency circuit provided in a mobile phone terminal such as a receiving unit may also be arranged on the circuit board 10.

  FIG. 4 shows an example in which the circuit board 10 to which the shield case 20 is attached is built in a mobile phone terminal. A circuit board 10 to which a shield case 20 is attached is disposed in a mobile phone terminal 1 configured using a casing of a predetermined shape, and a high-frequency power amplifier 30 (not shown) in the circuit board 10 is disposed. ) Is supplied to an antenna (not shown) built in the housing for wireless transmission. Note that the configuration of the housing illustrated in FIG. 4 is merely an example, and is not limited to the mobile phone terminal having this shape.

  FIG. 5 is a diagram illustrating a configuration example of a circuit block assembled on the circuit board 10. In the case of this example, the high-frequency transmission unit 12 generates a high-frequency transmission signal having a transmission frequency, and the generated transmission signal is supplied to the high-frequency power amplifier 30 to be amplified to necessary transmission power. is there. The amplified transmission signal is supplied to the antenna 15 via the duplexer 14 and wirelessly transmitted. When the antenna 15 is also used as a receiving antenna, the duplexer 14 extracts the received signal. It should be noted that the circuit components constituting the duplexer 14 are also preferably arranged on the circuit board 10.

  Next, an example of a circuit configuration when the high-frequency power amplifier 30 shown in FIGS. 1 and 2 is used as a high-frequency power amplifier provided in a mobile phone terminal will be described with reference to FIG. The input terminal RFin of the high frequency power amplifier 30 is connected to the gate of the first field effect transistor FET1 via the coil L1. A connection point between the input terminal RFin and the coil L1 is grounded via a capacitor C1.

  The amplified output of the first field effect transistor FET1 is further connected to the gate of the second field effect transistor FET2 via the coil L2. One end and the other end of the coil L2 are grounded via capacitors C2 and C3. The amplified output of the second field effect transistor FET2 is supplied to the output terminal RFout of the high frequency power amplifier 30 via the capacitor C5. The connection point between the second field effect transistor FET2 and the capacitor C5 is grounded via the capacitor C4. The capacitor and the coil correspond to the chip component 34 shown in FIGS.

  The circuit configuration of the high-frequency power amplifier 30 shown in FIG. 6 is an example, and various circuit configurations already known as high-frequency power amplifiers can be applied. As the amplifying element, an amplifying element other than the field effect transistor may be used.

Next, the operation of the high frequency power amplifier 30 configured as described above will be described.
The high frequency power amplifier 30 of this example has a magnetic material mixed resin cap 36 mixed with a magnetic material, and concentrates the high frequency magnetic field passing through the magnetic material mixed resin cap 36 by the action of the mixed magnetic material. And act to absorb. By absorbing in this way, the high-frequency magnetic field leaking into the shield case is reduced, and the high-frequency current flowing on the surface of the shield case 20 is reduced. Therefore, the noise is reduced, the influence on the device characteristics of other circuit components in the shield case is reduced, and the deterioration of the characteristics of the transmission power signal can be improved. When the circuit of the reception system is assembled on the circuit board 10, the reception characteristics are also improved.

Here, an example of the frequency characteristic of the magnetic permeability of the magnetic material will be described with reference to FIG. FIG. 7 is a graph illustrating an example of frequency characteristics of magnetic permeability of a magnetic material. The complex magnetic permeability μ is expressed by the following equation.
μ = μ′−jμ ″
Here, μ ′ is a real part and μ ″ is an imaginary part (loss).

  The real part μ ′ tends to decrease as the frequency increases, and the higher the value, the higher the frequency magnetic field can be concentrated. The imaginary part μ ″ tends to increase to a certain frequency and decrease when exceeding a certain frequency, and the higher the value, the higher the frequency magnetic field can be absorbed. As a magnetic material to be used, a magnetic material having an appropriate value of complex permeability μ = μ′−jμ ″ is selected, and a desired complex permeability μ = μ ′ at a transmission frequency used in a mobile phone terminal to which the high frequency power amplifier 30 is attached. In order to obtain −jμ ″, the resin material is mixed with a magnetic material with an appropriate amount of distribution and manufactured by resin molding.

  In this way, leakage of unnecessary radiation from the magnetic substance mixed resin cap 36 to the outside can be reduced by concentrating and absorbing the high frequency magnetic field with the magnetic material in the magnetic substance mixed resin cap 36. Therefore, the high-frequency current flowing in the shield case 20 is reduced, and the high-frequency current from the high-frequency power amplifier 30 does not affect the high-frequency transmission unit 12 arranged on the circuit board 10, and the high-frequency transmission unit 12 outputs The characteristics of the transmitted signal do not deteriorate due to the influence of unnecessary radiation.

  Here, FIG. 8 shows an example of the magnetic field distribution inside the shield case when the high-frequency power amplifier 30 of the present embodiment is arranged inside the shield case 20. The arrows in FIG. 8 indicate the magnetic field flow. Since the magnetic substance mixed resin cap 36 is provided in the high frequency power amplifier 30, a high frequency magnetic field is absorbed by the magnetic substance mixed resin cap 36, and the flow of the magnetic field near the surface of the high frequency power amplifier 30 is shown in FIG. Compared to the conventional example, the number is significantly reduced.

  An example of the high-frequency current flowing on the surface of the shield case 20 when the high-frequency power amplifier 30 is arranged inside the shield case 20 is indicated by an arrow in FIG. 9, and the high-frequency current flowing on the surface of the shield case 20 is also shown in FIG. Compared to the conventional example, the number is significantly reduced, and there is almost no flow of the high-frequency current to the side where the high-frequency transmission unit 12 is disposed.

  In the configuration shown in FIGS. 1 and 2, a space is formed between the inner surface 37 of the magnetic substance mixed resin cap 36 and the upper surface of the organic substrate 31, and an amplification element or the like is disposed in the space. However, the upper surface of the organic substrate 31 may be filled with the magnetic material mixed resin so that there is almost no gap. That is, for example, as shown in a cross section in FIG. 10, as a high-frequency power amplifier 30 ′, a field effect transistor 33 as an amplifying element and a chip portion 34 are arranged on the upper surface of an organic substrate 31 and connected by a wire 35. In this state, the magnetic material mixed resin cap 36 'filled with the magnetic material mixed resin with almost no gap is disposed. Other parts are configured in the same manner as the high-frequency power amplifier 30 shown in FIGS.

  With this configuration, the magnetic body is disposed closer to the amplifying element, and unnecessary radiation can be absorbed more effectively.

  In addition, the resin cap itself may be configured such that a separate magnetic material mixed sheet is stuck on the resin cap or the like without mixing the magnetic material. That is, for example, as shown in FIG. 11, as a high-frequency power amplifier 30 ″, a field effect transistor 33 as an amplifying element, a chip portion 34, and the like are arranged on the upper surface of the organic substrate 31 and are connected by a wire 35. In this state, the upper surface of the substrate 31 is covered with a resin cap 40. A magnetic material is not mixed in the resin cap 40 itself, and a magnetic material is mixed on the resin cap 40. The magnetic material mixed resin sheet 42 is pasted, and the other parts are configured in the same manner as the high-frequency power amplifier 30 shown in FIGS.

  With this configuration, the resin cap itself can be the same as the conventional resin cap, and the effect of absorbing unnecessary radiation can be obtained simply by adding the magnetic material mixed resin sheet 42. In FIG. 11, the magnetic material mixed resin sheet 42 is pasted on the surface of the resin cap 40, but the magnetic material mixed resin sheet is pasted on the back surface (or both the front and back surfaces) of the resin cap 40. It may be.

  In the above-described embodiment, the present invention is applied to the high-frequency power amplifier in the transmission unit (transmitter) included in the mobile phone terminal, but the present invention can also be applied to communication terminals including other similar high-frequency power amplifiers.

  In the above-described embodiment, ferrite has been described as an example of the magnetic material to be mixed with the resin cap. However, other magnetic materials may be mixed.

It is sectional drawing which shows the structural example of the high frequency power amplifier by one embodiment of this invention. It is a disassembled perspective view which decomposes | disassembles and shows the structure of the high frequency power amplifier by one embodiment of this invention. It is a disassembled perspective view which decomposes | disassembles and shows the structure on the circuit board by one embodiment of this invention. It is a perspective view which shows the example which incorporated the circuit board in the mobile telephone terminal by one embodiment of this invention. It is a block diagram which shows the example of a circuit to which the high frequency power amplifier by one embodiment of this invention is connected. It is a circuit diagram which shows the circuit example of the high frequency power amplifier by one embodiment of this invention. It is a characteristic view which shows the frequency characteristic example of the magnetic permeability of a magnetic body. It is explanatory drawing which shows the example of a magnetic field distribution inside the shield case by one embodiment of this invention in a cross section. It is a perspective view which shows the example of high frequency current distribution on the surface of the shield case by one embodiment of this invention. It is sectional drawing which shows the structural example by other embodiment of this invention. It is sectional drawing which shows the structural example by other embodiment of this invention. It is explanatory drawing which shows the example of a magnetic field distribution inside the shield case which has arrange | positioned the conventional high frequency power amplifier in a cross section. It is a perspective view which shows the example of high frequency current distribution on the surface of the shield case which has arrange | positioned the conventional high frequency power amplifier.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Mobile phone terminal, 10 ... Circuit board, 12 ... High frequency transmission part, 13 ... Signal line, 14 ... Duplexer, 15 ... Antenna, 20 ... Shield case, 30, 30 ', 30 "... High frequency power amplifier, 31 ... Organic Substrate, 32 ... concave portion, 33 ... field effect transistor (FET), 34 ... chip component, 35 ... wire, 36, 36 ', 36 "... magnetic substance mixed resin cap, 37 ... inner surface, 40 ... resin cap, 41 ... inner surface 42 ... Magnetic material mixed resin sheet, 90 ... Circuit board, 91a ... Organic substrate, 91b ... Surface mount device, 91c ... Resin cap, 92 ... High frequency transmitter, 93 ... Signal line, 94 ... Metal shield case

Claims (4)

In a high frequency power amplifier that amplifies a high frequency signal,
A substrate,
An amplifying element disposed on the substrate;
A high-frequency power amplifier comprising: a resin cap mixed with a magnetic material in a shape covering a substrate on which the amplifying element is disposed. The high frequency power amplifier according to claim 1, wherein
The high frequency power amplifier according to claim 1, wherein the magnetic material mixed with the resin cap is a magnetic material having little conductivity. The high frequency power amplifier according to claim 1, wherein
The high-frequency power amplifier according to claim 1, wherein the resin cap is disposed so as to fill an upper surface on which the amplification element is disposed with almost no gap. In a communication terminal equipped with a high-frequency power amplifier that amplifies a high-frequency transmission signal,
As the high-frequency power amplifier,
A substrate,
An amplifying element disposed on the substrate;
A communication terminal comprising a resin cap mixed with a magnetic material in a shape covering a substrate on which the amplification element is arranged.

Images