JP2008078735A - High frequency amplifier, and portable telephone employing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency amplifier which can ensure good high frequency performance while reducing the mounting area of components used, and to provide a portable telephone employing it. <P>SOLUTION: The high frequency amplifier comprises an input matching circuit 11 for matching the impedance of a high frequency signal inputted externally and modulated by a plurality of modulation systems, power amplifiers Tr1 and Tr2 performing power amplification of the high frequency signal impedance of which is matched in the input matching circuit, an RF switch 12 which delivers the high frequency signal outputted from the power amplifier while switching depending on the modulation system, and a plurality of outut matching circuits 20 and 21 for matching the impedance to optimize power efficiency and adjacent channel leakage power ratio for each high frequency signal outputted from the RF switch. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency amplifier that amplifies a high-frequency signal and a mobile phone using the same, and more particularly to a technique for supporting a plurality of modulation schemes such as a W-CDMA modulation scheme and an N-CDMA modulation scheme.

  2. Description of the Related Art Conventionally, W-CDMA (Wideband-Code Division Multiple Access) systems, N-CDMA (Narrowband-Code Division Multiple Access) systems, and the like are known as modulation systems employed in, for example, mobile phones.

  FIG. 4 is a diagram showing a configuration of a conventional W-CDMA compatible mobile phone. In this cellular phone, a high-frequency signal from the W-CDMA baseband IC 50 is power amplified by a power amplification IC 51, sent to an antenna 53 via a duplexer 52, and transmitted from the antenna 53 as a radio wave. In FIG. 4, the circuit on the receiving side is not shown. This W-CDMA mobile phone uses a frequency band of 830 to 840 MHz.

  The power amplifier IC 51 includes an input matching circuit 61, a W-CDMA power amplifier 62, and an output matching circuit 63. The W-CDMA power amplifier 62 amplifies a high-frequency signal input from the input terminal IN and impedance-matched by the input matching circuit 61. The output of the W-CDMA power amplifier 62 is impedance-matched by the output matching circuit 63 and output from the output terminal OUT. Further, a bias current is supplied to the W-CDMA power amplifier 62 from the outside.

  FIG. 5 is a diagram showing a configuration of a conventional N-CDMA compatible mobile phone. In this cellular phone, a high-frequency signal from the N-CDMA baseband IC 70 is amplified by a power amplification IC 71, sent to an antenna 74 via a duplexer 72 and a diplexer 73, and transmitted from this antenna 74 as a radio wave. The In FIG. 5, the circuit on the receiving side is not shown. In this N-CDMA compatible mobile phone, a frequency band of 815 to 830 MHz is used.

  The power amplifier IC 71 includes an input matching circuit 81, an N-CDMA power amplifier 82, and an output matching circuit 83. The N-CDMA power amplifier 82 amplifies the high-frequency signal that is input from the input terminal IN and impedance-matched by the input matching circuit 81. The output of the N-CDMA power amplifier 82 is impedance matched by the output matching circuit 83 and output from the output terminal OUT. The N-CDMA power amplifier 82 is supplied with a bias current from the outside.

  By the way, in recent years, mobile phones compatible with multiband / multimode corresponding to two or more different frequency bands and different modulation schemes such as the above-described W-CDMA modulation scheme and N-CDMA modulation scheme have been developed. Such a mobile phone needs to include a power amplifier (PA) and a peripheral circuit that are different for each modulation method. Further, since the current supplied to the power amplifier needs to be set individually depending on the modulation method, it is necessary to provide a bias circuit for each power amplifier. As a result, there are problems that the number of parts is increased, the mounting area is increased, the outer shape of the product is increased, the product price is increased, and the defect rate is increased.

In order to solve such a problem, Patent Document 1 discloses a high-frequency circuit device corresponding to a plurality of signals having different frequency bands and modulation methods, and a mobile communication terminal using the same. The high frequency circuit device disclosed in Patent Document 1 includes an amplifier that amplifies power of signals of at least two modulation systems (for example, W-CDMA and DCS systems), a matching circuit connected to the amplifier, and a duplexer. The circuit has a first path configured to be coupled to the antenna and a second path configured to couple the matching circuit to the antenna without including a duplexer. The first path is selected when the amplifier amplifies one of the at least two modulation schemes, and the second path is selected when the amplifier amplifies another signal. In both the first path and the second path, the output impedance of the amplifier matches the impedance of the amplifier as viewed from the antenna side. As a result, it is possible to provide a high-frequency circuit device with low circuit loss corresponding to multiband / multimode and a mobile communication terminal using the same.
JP 2005-294894 A

  As described above, in the conventional technology, for example, when a high-frequency amplifier is applied to a mobile phone that supports multiband / multimode, for example, a power amplifier IC for W-CDMA as shown in FIG. It is necessary to mount two types of components such as a power amplification IC for N-CDMA as shown. As a result, there are problems that the number of components constituting the high-frequency amplifier increases, the mounting area increases, the outer shape of the product increases, the product price increases, and the defect rate increases.

  Further, in the technique disclosed in Patent Document 1 that solves such a problem, the output matching circuit optimizes the output power, but distortion (adjacent channel power ratio “ACPR: Adjacent Channel Power Ratio”). ) And optimization of power efficiency are not considered, and there is a problem that good high-frequency performance cannot be obtained.

  The present invention has been made in order to solve the above-described problems, and the problem is that the mounting area of components to be used is reduced, and a high-frequency amplifier that can obtain good high-frequency performance and the same are used. To provide a mobile phone.

  In order to solve the above-mentioned problem, a high-frequency amplifier according to a first aspect of the present invention includes an input matching circuit that performs impedance matching of a high-frequency signal modulated by a plurality of modulation methods input from the outside, and an input matching circuit. For each of a power amplifier that amplifies power of a high-frequency signal with impedance matching, an RF switch that switches and outputs a high-frequency signal output from the power amplifier according to a modulation method, and a high-frequency signal output from the RF switch And a plurality of output matching circuits for impedance matching so that the power efficiency and the adjacent channel leakage power ratio are optimized.

  According to a second aspect of the present invention, there is provided a high frequency amplifying apparatus according to the first aspect of the present invention, wherein the bias current supplied to the power amplifier is adjusted so that the adjacent channel leakage power ratio is optimum for each of the modulation methods. A bias supply / control circuit for switching is provided.

  According to a third aspect of the present invention, there is provided a mobile phone including a baseband signal converter that converts a baseband signal into a high-frequency signal, a high-frequency amplifier that amplifies a high-frequency signal from the baseband signal converter, and a high-frequency amplifier. An antenna that transmits a high-frequency signal output from the air, and the high-frequency amplifier includes an input matching circuit that performs impedance matching of the high-frequency signal modulated by a plurality of modulation methods input from the baseband signal conversion unit, A power amplifier that amplifies the high frequency signal impedance-matched by the input matching circuit, an RF switch that switches and outputs the high frequency signal output from the power amplifier according to the modulation method, and a high frequency signal output from the RF switch Impedance matching to optimize power efficiency and adjacent channel leakage power ratio for each And a bias supply / control circuit that switches a bias current supplied to the power amplifier so that an adjacent channel leakage power ratio is optimized for each of the modulation schemes. And

  According to the first aspect of the present invention, a plurality of output matching circuits each corresponding to a plurality of modulation schemes are provided, and impedance matching is performed on the input high-frequency signal by the input matching circuit, and then amplified by the power amplifier. Since the output matching circuit corresponding to the modulation method outputs the impedance matching so that the power efficiency and the adjacent channel leakage power ratio are optimized, the power amplifier is shared by the plurality of modulation methods. As a result, the number of components in the peripheral circuit is reduced, and the mounting area of the components can be reduced. In addition, a plurality of output matching circuits respectively corresponding to a plurality of modulation schemes are provided, and impedance matching is performed so that the power efficiency and the adjacent channel leakage power ratio are optimized for each of the plurality of modulation schemes. It can be optimized and good high frequency performance can be obtained.

  According to the second aspect of the present invention, the bias current can be applied to the power amplifier so that the adjacent channel leakage power ratio is optimized for each of the modulation methods, so that the high frequency characteristics can be optimized. Good high frequency performance can be obtained. Further, since only one bias supply / control circuit needs to be provided for a plurality of modulation schemes, it is possible to reduce the mounting area of components, the product price, the defective rate, and the like.

  According to the third aspect of the present invention, since the power amplifying device corresponding to a plurality of modulation methods is provided inside one mobile phone, a mobile phone compatible with multiband and multimode can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a circuit configuration of a high-frequency amplification device according to Embodiment 1 of the present invention. This high-frequency amplification device includes a baseband IC 1, a control IC 2, a power amplification IC 3, and a bias supply / control circuit 4.

  The baseband IC 1 is a frequency conversion device that corresponds to the baseband signal conversion unit of the present invention and converts a baseband signal into a high-frequency signal. The high-frequency signal obtained by the conversion in the baseband IC 1 is sent to the power amplification IC 3. Further, the baseband IC 1 sends a signal corresponding to the baseband signal to the control IC 2.

  The control IC 2 generates a control signal indicating a modulation method based on the signal sent from the baseband IC 1 and sends it to the bias supply / control circuit 4.

  The power amplifier IC 3 includes a semiconductor pellet 10, a first output matching circuit 20, and a second output matching circuit 21. The cylindrical symbol in FIG. 1 represents a through hole. Rectangular symbols L1 to L3 represent 50Ω lines, L4 represents an inductor line, and L5 represents a high impedance line.

  In the semiconductor pellet 10, an input matching circuit 11, a first-stage transistor Tr1, a rear-stage transistor Tr2, an RF switch 12, and a bias circuit 13 are formed. The first-stage transistor Tr1 and the rear-stage transistor Tr2 correspond to the power amplifier of the present invention.

  The input matching circuit 11 includes, for example, a 50Ω line L1 and a capacitor C11. The input matching circuit 11 performs impedance matching of a high-frequency signal input from the input terminal IN via the DC component blocking capacitor C1, and sends the impedance match to the first-stage transistor Tr1. .

  The first-stage transistor Tr1 amplifies the power of the input high-frequency signal according to the bias current supplied from the bias circuit 13, and sends it to the subsequent-stage transistor Tr2. The rear-stage transistor Tr2 amplifies the power of the high-frequency signal sent from the first-stage transistor Tr1 according to the bias current supplied from the bias circuit 13, and sends the amplified signal to the RF switch 12 via the DC component blocking capacitor C2.

  A series resonance circuit composed of a capacitor C21 and an inductance by an inductor line L4 is connected to the output side of the rear-stage transistor Tr2, and acts to lower the level of the component of the frequency 2f0 that is twice the peak frequency f0. Therefore, only the high-frequency signal having the peak frequency f0 is sent from the rear-stage transistor Tr2 to the RF switch 12.

  The RF switch 12 connects the input terminal to either the output terminal P1 or the output terminal P2 according to the signal Vg sent from the bias supply / control circuit 4. As a result, the high-frequency signal sent from the rear-stage transistor Tr2 is output from the output terminal P1 or the output terminal P2 in accordance with the signal Vg sent from the bias supply / control circuit 4.

  The bias circuit 13 optimizes the distortion (primary adjacent channel leakage power ratio: ACPR1) of each of the first-stage transistor Tr1 and the subsequent-stage transistor Tr2 according to the signals Vc1, Vcon, and Vdc sent from the bias supply / control circuit 4. Bias currents Ic1 and Ic2 are generated and supplied to the first-stage transistor Tr1 and the subsequent-stage transistor Tr2, respectively. Capacitors C31 to C33 connected to the lines of signals Vc1, Vcon and Vc2 are decoupling capacitors.

  FIG. 2 is a diagram illustrating the relationship between the bias current and ACPR1 when the modulation method is N-CDMA and the frequency is 830 MHz. FIG. 2A shows the relationship between the bias current Ic1 of the first-stage transistor Tr1 and ACR1 when the bias current Ic2 of the rear-stage transistor Tr2 is fixed to 45 mA. FIG. 2A shows that 9 mA is optimal for the bias current Ic1 of the first-stage transistor Tr1. FIG. 2B shows the relationship between the bias current Ic2 of the rear-stage transistor Tr2 and ACR1 when the bias current Ic1 of the first-stage transistor Tr1 is fixed to 9 mA. As can be seen from FIG. 2B, the optimum bias current Ic2 of the rear-stage transistor Tr2 is 45 mA.

  The first output matching circuit 20 includes a 50Ω line L2 and a capacitor C12, and an impedance Zout that optimizes the distortion and efficiency of W-CDMA with respect to a high-frequency signal output from the output terminal P1 of the RF switch 12. The output is output from the first output terminal OUT1 with matching.

  The second output matching circuit 21 includes a 50Ω line L3 and a capacitor C13, and an impedance Zout that optimizes N-CDMA distortion and efficiency with respect to a high-frequency signal output from the output terminal P2 of the RF switch 12. The output is output from the second output terminal OUT2 with matching.

  These first output matching circuit 20 and second output matching circuit 21 have load impedance that optimizes distortion (adjacent channel leakage power suppression ratio “ACLR1: Adjacent Cannel Leakage power Ratio”) and power efficiency. As shown in FIG. 3, the power efficiency and the distortion are in a trade-off relationship. The first output matching circuit 20 is required to select a load impedance satisfying both. In the example shown in FIG. 3, the load impedance Re at the optimum load point is 5 [Ω].

  The bias supply / control circuit 4 generates signals Vc1, Vcon, and Vdc for generating a bias current that optimizes distortion and power efficiency in each modulation method in accordance with a control signal from the control IC 2, and generates a semiconductor pellet 10 The bias circuit 13 is set. Further, a signal Vg for switching the RF switch 12 in the semiconductor pellet 10 is generated and sent to the RF switch 12.

  As described above, in the conventional high-frequency amplifier, it is necessary to provide a power amplifier and a peripheral circuit corresponding to each modulation method in order to correspond to two different modulation methods, but the implementation of the present invention shown in FIG. The high-frequency amplifier according to Example 1 includes a common input matching circuit 11 and a power amplifier (first-stage transistor Tr1 and rear-stage transistor Tr2) for each modulation method, and an individual first output matching circuit 20 and a second output for each modulation method. By providing the output matching circuit 21, one power amplifying device is configured.

  Next, the operation of the high frequency amplifying apparatus according to the first embodiment of the present invention configured as described above will be described separately for the case of operating in the W-CDMA modulation system and the case of operating in the N-CDMA modulation system. To do.

(1) When operating in the W-CDMA modulation system The high-frequency signal input to the input terminal IN of the power amplifier IC 3 is, as shown in the transmission path a, the input matching circuit 11, the first-stage transistor Tr1, the rear-stage transistor Tr2, and the RF switch. 12 is transmitted to the first output terminal OUT1 (W-CDMA OUT) through the first output matching circuit 20 configured to have the distortion of the W-CDMA modulation system and the optimum power efficiency impedance. At this time, the first output matching circuit 20 has an optimum impedance of Zout = 7.0 + j7.3 [Ω]. At the same time, the bias supply / control circuit 4 uses the bias current Ic1 that flows through the collector of the first-stage transistor Tr1 and the bias current Ic2 that flows through the collector of the subsequent-stage transistor Tr2 in order to obtain the best distortion characteristics and power efficiency. = 7 mA, Ic2 = 25 mA.

  As a result, the first output matching circuit 20 and the bias current are optimized, and the high frequency performance of the power amplifier IC 3 is maximized. Specifically, the power efficiency is 50% or more, and the primary adjacent channel leakage power ratio ACPR1 is −40 dBc or less, and the secondary adjacent channel leakage power ratio ACPR2 is −50 dBc or less. Note that the frequencies of the points at which W-CDMA primary adjacent channel leakage power ratio ACPR1 and secondary adjacent channel leakage power ratio ACPR2 are measured are as follows.

Primary adjacent channel leakage power ratio ACPR1: center frequency (f0) ± 5 MHz
Secondary adjacent channel leakage power ratio ACPR2: center frequency (f0) ± 10 MHz
(2) When operating in the N-CDMA modulation system The high-frequency signal input to the input terminal IN of the power amplifier IC 3 is, as shown by the transmission path b, the input matching circuit 11, the first-stage transistor Tr1, the rear-stage transistor Tr2, and the RF switch. 12 is transmitted to the second output terminal OUT2 (N-CDMA OUT) through the second output matching circuit 21 configured to have N-CDMA modulation system distortion and power efficiency optimum impedance. At this time, the second output matching circuit 21 has an optimum impedance of Zout = 5.0 + j0.2 [Ω]. At the same time, the bias supply / control circuit 4 uses the bias current Ic1 that flows through the collector of the first-stage transistor Tr1 and the bias current Ic2 that flows through the collector of the subsequent-stage transistor Tr2 in order to obtain the best distortion characteristics and power efficiency. = 9 mA and Ic2 = 45 mA.

  As a result, the second output matching circuit 21 and the bias current are optimized, and the high frequency performance of the power amplifier IC 3 is maximized. Specifically, the power efficiency is 40% or more, and the primary adjacent channel leakage power ratio ACPR1 is −50 dBc or less, and the secondary adjacent channel leakage power ratio ACPR2 is −60 dBc or less. In addition, the frequency of the point which measures N-CDMA primary adjacent channel leakage power ratio ACPR1 and secondary adjacent channel leakage power ratio ACPR2 is as follows.

Primary adjacent channel leakage power ratio ACPR1: center frequency (f0) ± 0.885 MHz
Secondary adjacent channel leakage power ratio ACPR2: center frequency (f0) ± 1.98 MHz

  The high-frequency amplifier according to the present invention can be used in a multiband / multimode mobile phone.

It is a figure which shows the circuit structure of the power amplification apparatus which concerns on Example 1 of this invention. FIG. 6 is a diagram for explaining a bias current that optimizes distortion (ACPR1) in the power amplification device according to the first embodiment of the present invention. It is a figure for demonstrating the load impedance which optimizes distortion (ACLR1) and power efficiency in the power amplifier device which concerns on Example 1 of this invention. It is a figure which shows the structure of the conventional mobile phone corresponding to W-CDMA. It is a figure which shows the structure of the conventional mobile phone corresponding to N-CDMA.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Baseband IC, 2 ... Control IC, 3 ... Power amplification IC, 4 ... Bias supply / control circuit, 10 ... Semiconductor pellet, 11 ... Input matching circuit, 12 ... RF switch, 13 ... Bias circuit, 20 ... Output matching Circuit, 20a... First output matching circuit, 20b... Second output matching circuit, Tr1... First stage transistor, Tr2.

Claims (3)

An input matching circuit for impedance matching of a high-frequency signal modulated by a plurality of modulation methods input from the outside;
A power amplifier that amplifies the power of the high-frequency signal impedance-matched by the input matching circuit;
An RF switch that switches and outputs a high-frequency signal output from the power amplifier according to a modulation method;
A plurality of output matching circuits that perform impedance matching so that power efficiency and adjacent channel leakage power ratio are optimized for each of the high-frequency signals output from the RF switch;
A high frequency amplifying apparatus comprising:   2. The high frequency amplifier according to claim 1, further comprising a bias supply / control circuit that switches a bias current supplied to the power amplifier so that an adjacent channel leakage power ratio is optimized for each of the modulation methods. apparatus. A baseband signal converter for converting a baseband signal into a high-frequency signal;
A high-frequency amplifier for amplifying a high-frequency signal from the baseband signal converter;
An antenna for transmitting a high-frequency signal output from the high-frequency amplifier to the air,
The high-frequency amplifier is
An input matching circuit for impedance matching of a high-frequency signal modulated by a plurality of modulation schemes input from the baseband signal converter;
A power amplifier that amplifies the power of the high-frequency signal impedance-matched by the input matching circuit;
An RF switch that switches and outputs a high-frequency signal output from the power amplifier according to a modulation method;
A plurality of output matching circuits that perform impedance matching so that power efficiency and adjacent channel leakage power ratio are optimized for each of the high-frequency signals output from the RF switch;
A bias supply / control circuit for switching a bias current supplied to the power amplifier so that an adjacent channel leakage power ratio is optimized for each of the modulation schemes;
A mobile phone characterized by comprising:

Images