JP2008028635A - High frequency electric power amplifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency electric power amplifying device of broadband and low noise corresponding to a multiband multimode, without increasing a circuit scale. <P>SOLUTION: An impedance adjustment part 12 adjusts impedance so as to match a value suitable for the frequency of a high frequency signal RF according to the control by a control part 13. An amplifier part 11 amplifies the high frequency signal RF outputted from the impedance adjustment part 12 on a predetermined profit. A first low impedance part 14 is a circuit for making impedance to a difference frequency (¾Rx-Tx¾) small, and is connected between a GND and the input side of the impedance adjustment part 12. A second low impedance part 15 is a circuit for making impedance to a sum frequency (Rx+Tx) small, and is connected between a GND and the output side of the impedance adjustment part 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency power amplifying apparatus that reduces reception band noise of an amplifier that operates nonlinearly in a wide band.

  As is well known, in a transmission / reception device such as a cellular phone, the signal spectrum at the input terminal of the high-frequency power amplifying device is a wide-band noise spectrum including a transmission frequency (Tx) signal spectrum and a reception frequency (Rx) with strong signal strength. Is the sum of When a signal having such a frequency spectrum is input to the high-frequency power amplifier, the reception band noise increases due to the following two factors, and the noise characteristics of the high-frequency power amplifier are degraded.

  One factor is the noise in the reception band added by the high frequency power amplifier. The noise in the reception band is dependent on the input load, and the load noise can be minimized by optimizing the input load impedance. Further, when the frequency changes, the optimum input load impedance also changes.

  Another factor is noise that occurs when a high-level transmission signal is input and the high-frequency power amplifying apparatus saturates and performs non-linear operation, and the transmission signal and noise are mixed to generate another frequency band. The noise that is a problem here is noise generated in the reception band due to noise of a specific frequency and secondary distortion of the transmission signal. FIG. 8 is a diagram for explaining the cause of noise generated in this reception band.

  Noise frequencies that cause noise generated in the reception band are two frequencies: a sum frequency (Rx + Tx) and a difference frequency (| Rx−Tx |). The signal of the sum frequency (Rx + Tx) is down-converted by mixing with the Tx signal, and noise of the reception frequency Rx that is the difference is generated. Further, the signal of the difference frequency (| Rx−Tx |) is up-converted by mixing with the Tx signal to generate noise of the reception frequency Rx that is the sum of the signals. Therefore, in order to reduce the reception band noise, it is necessary to reduce the noise of the sum frequency (Rx + Tx) and the noise of the difference frequency (| Rx−Tx |).

  In a transmission / reception device such as a mobile phone, the maximum value of noise intensity in the reception band of the transmission signal is defined in order to prevent the transmission signal from interfering with weak reception signals of other mobile phones. In order to satisfy this rule, a filter element having a large attenuation in the reception band may be externally attached to the high frequency power amplifier. However, in this case, since the transmission signal is also lost, the usage time of the mobile phone is shortened. Moreover, the cost and mounting area increase by adding external parts.

In order to solve such a problem, a method capable of reducing reception band noise without using an external filter element has been proposed. See, for example, US Pat.
In this conventional method, attention is paid to the fact that the noise generated in the reception band is noise obtained by up-converting the noise of the difference frequency (| Rx−Tx |) with the transmission signal. Specifically, in order to reduce noise at the difference frequency (| Rx−Tx |), a resonance circuit having a small impedance at the difference frequency (| Rx−Tx |) is inserted.

FIG. 9 is a diagram showing a configuration in which a general impedance adjustment function is added to the conventional high-frequency power amplifying device disclosed in Patent Document 1. In FIG. This conventional high frequency power amplifying apparatus includes an amplifying unit 101, an impedance adjusting unit 102, a control unit 103, a resonance circuit 104, a plurality of inductor elements L3 to L4, capacitors C3 to C6, and resistance elements R3 to R4. It is configured. The resonance circuit 104 includes an inductor element L5, capacitors C7 to C8, and a resistor element R5, and each constant is designed so that the impedance becomes small at the difference frequency (| Rx−Tx |).
JP 2003-298364 A

  However, the resonance circuit 104 used in the conventional high-frequency power amplifier described above has a narrow bandwidth that can be attenuated. For this reason, no matter how well the circuit is designed, only noise of difference frequency (| Rx−Tx |) corresponding to a specific system (or noise of sum frequency (Rx + Tx)) can be attenuated. See FIG.

  Furthermore, in the field of wireless communication devices in recent years, there is an increasing expectation for a multi-band multi-mode that enables a plurality of different wireless systems to be used in one device. When the plurality of different radio systems are, for example, W-CDMA, DCS, PCS, and GSM850, each radio system has the transmission frequency Tx, the sum frequency (Rx + Tx), and the difference frequency (| Rx−) shown in FIG. Tx |).

  For this reason, a high-frequency power amplifying device is required to have a broadband attenuation performance that can cover all of a plurality of wireless systems even if only the sum frequency (Rx + Tx) or only the difference frequency (| Rx−Tx |) is focused. Will be. In order to realize this requirement, a configuration in which a plurality of conventional high-frequency power amplifiers shown in FIG. 9 are connected in parallel by the number of wireless systems is conceivable. However, the scale of the high-frequency power amplifying apparatus becomes enormous and is not realistic.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a wideband and low noise high-frequency power amplifying apparatus compatible with multiband multimode without increasing the circuit scale.

  The present invention is directed to a high-frequency power amplifier that amplifies a plurality of high-frequency signals having different frequencies corresponding to a plurality of wireless systems. In order to achieve the above object, the high-frequency power amplifying device of the present invention includes a wireless system that uses an input high-frequency signal and an impedance adjustment unit that adjusts impedance to a value corresponding to the channel frequency, and an impedance adjustment unit. An amplifier that amplifies the high-frequency signal to be output with a predetermined gain and an impedance adjustment unit connected in parallel to the input side of the impedance adjustment unit. And a first impedance reduction unit for reducing the frequency difference over the entire difference frequency of the plurality of wireless systems.

  Preferably, a second impedance reduction unit that reduces the impedance of the sum frequency that is the sum of the transmission frequency and the reception frequency used by the wireless system over the total frequency of the plurality of wireless systems is provided on the output side of the impedance adjustment unit. It is better to connect them in parallel.

Typically, the first impedance reduction unit includes an inductor element, a series circuit of an inductor element and a resistor element, or a low-pass filter.
In addition, the second impedance reduction unit includes a series circuit of an inductor element, a capacitive element, and a resistive element, a capacitive element, or a high-pass filter.

  According to the present invention, the reception band noise can be increased by reducing the broadband sum frequency noise and difference frequency noise, respectively, with a very simple structure without having a plurality of resonance circuits for a plurality of radio systems. Can be prevented.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration of a high-frequency power amplifying device according to an embodiment of the present invention. The high frequency power amplifying device of the present invention includes an amplifying unit 11, an impedance adjusting unit 12, a control unit 13, a first low impedance reducing unit 14, a second low impedance reducing unit 15, and a plurality of inductor elements L3. To L4, capacitors C3 to C6, and resistance elements R3 to R4.

  Note that the configuration of the plurality of inductor elements L3 to L4, capacitors C3 to C6, and resistor elements R3 to R4 is an example used because it is easy to compare with the conventional high frequency power amplifier (FIG. 9). Therefore, in addition to the configuration shown in FIG. 1, it is possible to design freely according to the state of the high-frequency signal RF desired to be obtained from the output of the amplifying unit 11, matching with the subsequent device, and the like.

  The control unit 13 controls the impedance adjustment unit 12 according to the frequency of the high-frequency signal RF input to the high-frequency power amplification device, that is, according to the radio system using the input high-frequency signal RF and the channel frequency. The impedance adjustment unit 12 adjusts the impedance to a value that matches the frequency of the high-frequency signal RF in accordance with control by the control unit 13. The amplification unit 11 amplifies the high-frequency signal RF output from the impedance adjustment unit 12 with a predetermined gain. The first impedance reduction unit 14 is a circuit for reducing the impedance with respect to the difference frequency (| Rx−Tx |), and is connected between the input side of the impedance adjustment unit 12 and the ground (GND). FIG. 1 shows an example in which the first impedance reduction unit 14 is an inductor element L1. The second impedance reduction unit 15 is a circuit for reducing the impedance with respect to the sum frequency (Rx + Tx), and is connected between the output side of the impedance adjustment unit 12 and the ground. FIG. 1 shows an example in which the second impedance reduction unit 15 is a series circuit of an inductor element L2, a capacitive element C2, and a resistive element R2.

  FIG. 2 shows values of a transmission frequency Tx, a difference frequency (| Rx−Tx |), and a sum frequency (Rx + Tx) in an example of a plurality of wireless systems used in a mobile phone or the like. Yes.

  As can be seen from FIG. 2, when the difference frequencies of the three wireless systems of W-CDMA, DCS, and PCS are combined, a frequency range of 20 MHz to 190 MHz is obtained. Therefore, when designing a broadband high-frequency power amplifying apparatus corresponding to three wireless systems of W-CDMA, DCS, and PCS, the first low impedance unit 14 has an impedance up to a predetermined value at a frequency of 190 MHz or less. A smaller element, for example, an inductor element is used. Thereby, only the 1st impedance reduction part 14 can reduce the difference frequency noise of three radio systems collectively.

  Further, when the sum frequency of the three wireless systems of W-CDMA, DCS, and PCS is combined, a frequency range of 3.515 GHz to 4.15 GHz is obtained. Therefore, when designing a broadband high-frequency power amplifying apparatus corresponding to three wireless systems of W-CDMA, DCS, and PCS, the second low impedance unit 15 has a predetermined impedance at a frequency of 3.5 GHz or more. An element that decreases to a value, for example, a circuit including a capacitor element is used. Thereby, only the 2nd impedance reduction part 15 can reduce the sum frequency noise of three radio systems collectively.

  FIG. 3 is a diagram showing frequency characteristics in the high-frequency power amplifying apparatus according to the embodiment of the present invention. As shown in FIG. 3, the high frequency power amplifying apparatus of the present invention has a difference frequency (| Rx−Tx |) and a sum frequency (Rx + Tx) more than the conventional high frequency power amplifying apparatus (see FIG. 10). The amount of attenuation is large. Although attenuation is observed at the transmission frequency Tx, there is no influence in actual use at this level.

In addition to the structure shown in FIG. 1, the structure shown in FIGS. 4-6 can be considered for the 1st impedance reduction part 14 and the 2nd impedance reduction part 15, for example.
FIG. 4 shows an example in which the first impedance reduction unit 14 is the inductor element L1 and the second impedance reduction unit 15 is only the capacitive element C2.

  FIG. 5 shows an example in which the first impedance reduction unit 14 is a series circuit of an inductor element L1 and a resistance element R1, and the second impedance reduction unit 15 is a series circuit of a capacitance element C2 and a resistance element R2. Is shown. In this case, it is preferable that at least one of the resistance elements R1 and R2 has a resistance value of 10Ω or less. When the resistance element is inserted as described above, the stability of the high-frequency power amplifier increases.

  FIG. 6 shows an example in which the first impedance reduction unit 14 is a low-pass filter LPF, and the second impedance reduction unit 15 is a high-pass filter HPF. When the band filter is configured as described above, a steep attenuation characteristic can be obtained, so that the difference frequency noise and the sum frequency noise can be further attenuated, and at the same time, the loss of the transmission signal can be improved.

  FIG. 7 is a diagram illustrating a typical configuration example of the impedance adjustment unit 12. In FIG. 7, the impedance adjustment unit 12 includes three impedance elements 121 to 123 and changeover switches 124 and 125. By appropriately switching the changeover switches 124 and 125 according to the change of the wireless system, it is possible to determine an optimum impedance value suitable for the transmission frequency Tx of the wireless system.

  As described above, according to the high-frequency power amplifying device according to the embodiment of the present invention, a wide-band sum frequency noise and a simple structure without having a plurality of resonance circuits for a plurality of wireless systems. Difference frequency noise can be reduced to prevent an increase in reception band noise.

In the above-described embodiment, the high-frequency power amplifying apparatus including both the first impedance reduction unit 14 and the second impedance reduction unit 15 has been described. However, the first impedance reduction unit 14 or the second impedance reduction unit 14 Even if only one of the impedance reduction units 15 is used, an effect of reducing reception band noise can be obtained.
For example, when only the first impedance reduction unit 14 is provided, a 2 GHz band system and an 800 MHz band system (for example, GSM850) can be realized by one high frequency power amplifier.

  The present invention can be used for a high frequency power amplifying apparatus and the like corresponding to a plurality of radio systems, and in particular, with a very simple structure, it is possible to reduce wideband sum frequency noise and difference frequency noise respectively and reduce reception band noise. This is suitable for preventing the increase.

The figure which shows the structure of the high frequency power amplifier which concerns on one Embodiment of this invention. The figure which shows the example of each frequency value in a radio | wireless system The figure which shows the frequency characteristic in the high frequency power amplifier which concerns on one Embodiment of this invention. The figure which shows the other structural example of the 1st and 2nd impedance reduction parts 14 and 15 The figure which shows the other structural example of the 1st and 2nd impedance reduction parts 14 and 15 The figure which shows the other structural example of the 1st and 2nd impedance reduction parts 14 and 15 The figure which shows the typical structural example of the impedance adjustment part 12. Diagram explaining the cause of noise generated in the reception band The figure which shows the structure of the conventional high frequency power amplifier The figure which shows the frequency characteristic in the conventional high frequency power amplifier

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 101 Amplifying part 12, 102 Impedance adjustment part 13, 103 Control part 14, 15 Low impedance part 104 Resonance circuit 121-123 Impedance element 124, 125 Changeover switch L1-L5 Inductor element C1-C8 Capacitor R1-R5 Resistance element

Claims (8)

A high-frequency power amplifier that amplifies a plurality of high-frequency signals having different frequencies corresponding to a plurality of wireless systems,
An impedance adjustment unit that adjusts the impedance to a value corresponding to a wireless system using an input high-frequency signal;
An amplifying unit for amplifying a high-frequency signal output from the impedance adjusting unit with a predetermined gain;
A first connected in parallel to the input side of the impedance adjuster and lowering an impedance of a difference frequency, which is an absolute value difference between a transmission frequency and a reception frequency used by a wireless system, over all difference frequencies of the plurality of wireless systems. A high frequency power amplifying apparatus comprising a low impedance unit.   A second low impedance connected in parallel to the output side of the impedance adjuster and reducing the impedance of the sum frequency, which is the sum of the transmission frequency and the reception frequency used by the wireless system, over the total frequency of the plurality of wireless systems The high frequency power amplifying apparatus according to claim 1, further comprising: a conversion unit.   The high frequency power amplifying apparatus according to claim 1, wherein the first impedance reduction unit includes an inductor element.   The high frequency power amplifying apparatus according to claim 1, wherein the first impedance reduction unit is configured by a series circuit of an inductor element and a resistance element.   The high frequency power amplifier according to claim 1 or 2, wherein the first impedance reduction unit is configured by a low pass filter.   The high-frequency power amplifying apparatus according to claim 2, wherein the second impedance reduction unit is configured by a series circuit of an inductor element, a capacitive element, and a resistive element.   The high frequency power amplifying apparatus according to claim 2, wherein the second impedance reduction unit includes a capacitive element. The high frequency power amplification device according to claim 2, wherein the second impedance reduction unit is configured by a high-pass filter.

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