JP2008193633A - Power amplifier - Google Patents

Abstract

In a high-frequency power amplifier circuit, an analog circuit, a feedback loop, and a large smoothing capacitor are not provided. To be able to cope with wideband signals without reducing efficiency.
A power amplifier includes an amplifier, a plurality of switching current sources, a plurality of switching current sources, a plurality of rectifiers, and a modulator. The modulator 14 outputs a control signal corresponding to the envelope component of the high frequency signal. Each of the switching current sources 15, 16, and 17 flows a current controlled by the control signal output from the modulator 14. The currents flowing from the switching current sources 15, 16, and 17 are rectified by the rectifiers 18, 19, and 20, added together, and supplied to the amplifier 11. The amplifier 11 operates with high power supply efficiency by the supplied current, amplifies the input high-frequency signal, and outputs a signal composed of a modulated wave with a change in amplitude.
[Selection] Figure 1

Description

  The present invention relates to a power amplifier using a semiconductor element as an amplifying element.

  Conventionally, a power amplifier using a semiconductor element as an amplifying element is known. In order to operate such a power amplifier with high power supply efficiency, it is important to operate the power amplifier so that the time integration of the product of the current and voltage at the output terminal of the element is small, thereby reducing the loss inside the element. For this purpose, it is effective to operate the amplifier in saturation.

  An amplifier is known in which an amplitude-modulated wave is efficiently extracted from an amplifying element that is always operating in saturation. Examples of such an amplifier include LINC (Linear Amplifying Usage Nonlinear Components), Doherty amplifier, ET (Envelope Tracking), and EER (Envelope Eliminating and Restoration).

  FIG. 2 shows the configuration of LINC. As shown in FIG. 2, the LINC includes two amplifiers 1 and 2. Each of the amplifiers 1 and 2 performs a saturation operation using a signal having a constant amplitude and a phase change as an input signal. The output signals of the two amplifiers 1 and 2 are combined by the combining unit 3 and output. When the phase of the input signal of each of the amplifiers 1 and 2 changes, the amplitude of the output signal changes.

  FIG. 3 shows the configuration of the Doherty amplifier. As shown in FIG. 3, the Doherty amplifier includes a main amplifier 4, an auxiliary amplifier 5, and two ¼ wavelength lines 6 and 7. A signal obtained by delaying the input signal of the main amplifier 4 by λ / 4 by the quarter wavelength line 6 is input to the auxiliary amplifier 5. A signal obtained by delaying the output signal of the main amplifier 4 by λ / 4 by the quarter wavelength line 7 and the output signal of the auxiliary amplifier 5 are combined and output. Normally, the main amplifier 4 is operated in class A or class AB, and the auxiliary amplifier 5 is operated in class B. When the input power is increased, the main amplifier 4 starts the saturation operation first, and high efficiency is obtained.

  FIG. 4 shows the configuration of ET or EER. As shown in FIG. 4, the ET or EER includes a high-frequency high-power amplifier 8 and a low-frequency amplifier 9. In the case of EER, a high-frequency high-power amplifier 8 receives a signal having a constant amplitude. The low frequency amplifier 9 receives an envelope component signal having amplitude information. The high-frequency high-power amplifier 8 is always in a saturation operation, and the bias is modulated by the output signal of the low-frequency amplifier 9 to output a signal having an amplitude modulation component. In the case of ET, a signal whose amplitude varies is input to the high-frequency high-power amplifier 8.

  By the way, as a high frequency amplifier using a semiconductor element as an amplifying element, one having the following configuration is known. A circuit for detecting an envelope component of an input signal applied to the control electrode of the semiconductor amplifying element, and a voltage applied to the drain electrode or the collector electrode of the semiconductor element are substantially proportional to the envelope component detected by the circuit. A voltage control circuit. The voltage control circuit includes a plurality of DC power supplies having different voltages with low internal resistance, and includes switching means for extracting different power supply voltages from the plurality of DC power supplies according to the voltage applied to the drain electrode or the collector electrode (for example, (See Patent Document 1).

JP-A-62-277806 (2. Claims (1))

  However, the above-described conventional amplifier has the following problems. In LINC, it is difficult to efficiently combine the outputs of two amplifiers. In the Doherty amplifier, the transmission band that combines the matching circuit and the phase shift circuit of the main amplifier and the auxiliary amplifier becomes narrow. In ET and EER, it is difficult to make the bias of a high-frequency high-power amplifier correspond to a fast amplitude change of an envelope component signal. Further, the conventional power amplifier is provided with an analog circuit, a feedback loop, and a large smoothing capacitor, and there is a limit to follow the ET power source with a wideband signal for power saving of the power source circuit itself. Furthermore, in the conventional power amplifier, if the power supply voltage changes greatly in a short time, the efficiency decreases.

  An object of the present invention is to provide a power amplifier circuit that does not require an analog circuit, a feedback loop, or a large smoothing capacitor in order to eliminate the above-described problems caused by the prior art. Another object of the present invention is to provide a power amplifier circuit that can cope with wideband signals without reducing the efficiency.

  In order to solve the above-described problems and achieve the object, a power amplifier according to the present invention includes an amplifier, a plurality of switching current sources, a plurality of rectifiers, and a modulator. The modulator outputs a control signal corresponding to the envelope component of the high frequency signal. Each switching current source passes a current controlled by a control signal output from the modulator. The currents flowing from the respective switching current sources are rectified by the rectifier, and then added together and supplied to the amplifier. The amplifier operates with high power supply efficiency by the supplied current, amplifies the input high-frequency signal, and outputs a signal composed of a modulated wave with a change in amplitude.

  According to the present invention, even without an analog circuit, a feedback loop, and a large smoothing capacitor, it is possible to amplify a high-frequency signal at a sufficiently high speed with high power supply efficiency.

  The power amplifier according to the present invention has an effect that an analog circuit, a feedback loop, and a large smoothing capacitor are unnecessary. In addition, there is an effect that it is possible to cope with a wideband signal without reducing the efficiency.

  Exemplary embodiments of a power amplifier according to the present invention will be explained below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of a power amplifier according to an embodiment of the present invention. As shown in FIG. 1, the power amplifier includes an amplifier 11, a quarter wavelength line 12 constituted by an open stub, an inductor 13, a modulator (MOD) 14, m switching current sources 15, 16, 17, and m rectifiers 18, 19, and 20 are provided. Here, m is a natural number.

  The amplifier 11 is not particularly limited, and is composed of, for example, a source-grounded MOS transistor. This MOS transistor amplifies the high-frequency signal input to its gate terminal and outputs the amplified signal from the drain terminal. The drain terminal is connected to the inductor 13 for supplying a bias (drain voltage) to the amplifier 11 and the quarter wavelength line 12. This bias is modulated by the switching current sources 15, 16 and 17.

The modulator 14 performs ΔΣ modulation on the _n- bit digital envelope signals e ₀ , e ₁ , and e _n−1 , and forms an m-bit control signal p ₀ that is waveform-shaped into an RZ (Return to Zero) signal having a predetermined time width. , P ₁ , p _m−1 are output. The digital envelope signals e ₀ , e ₁ , e _n-1 are digital signals of envelope components of the high frequency signal amplified by the amplifier 11. Here, n is a natural number.

The first switching current source 15 has a configuration in which an inductor 21 and a MOS transistor 22 are connected in series between a power source and a ground point. A drain voltage is supplied to the MOS transistor 22 via the inductor 21. The source terminal of the MOS transistor 22 is grounded. The gate terminal of the MOS transistor 22 is connected to the terminal of the modulator 14 that outputs the control signal p ₀ . The drain terminal of the MOS transistor 22 is connected to the input terminal of the first rectifier 18.

The second switching current source 16 is configured in the same manner as the first switching current source 15 by an inductor 23 and a MOS transistor 24. The gate terminal of the MOS transistor 24 is connected to the terminal of the modulator 14 that outputs the control signal p ₁ . The drain terminal of the MOS transistor 24 is connected to the input terminal of the second rectifier 19.

The m-th switching current source 17 is configured in the same manner as the first switching current source 15 by an inductor 25 and a MOS transistor 26. The gate terminal of the MOS transistor 26 is connected to the terminal of the modulator 14 that outputs the control signal p _m−1 . The drain terminal of the MOS transistor 26 is connected to the input terminal of the mth rectifier 20.

  The first rectifier 18, the second rectifier 19, and the m-th rectifier 20 are respectively supplied from the first switching current source 15, the second switching current source 16, and the m-th switching current source 17. Rectify current. The currents rectified by each of the first rectifier 18, the second rectifier 19, and the m-th rectifier 20 are added together and supplied to the drain terminal of the amplifier 11 as a power supply current. Since the switching current sources 15, 16, and 17 are weighted in advance, the combined current value has multi-bit accuracy.

  As each rectifier 18, 18, 20, for example, a normal rectifying semiconductor diode can be used. More preferably, each of the rectifiers 18, 19, and 20 may be composed of a Schottky diode that has a small decrease in forward voltage or an active rectifier that includes a MOS transistor that has almost no decrease in forward voltage.

Next, the operation of the power amplifier having the configuration shown in FIG. 1 will be described. When the digital envelope signals e ₀ , e ₁ , e _n-1 are input to the modulator 14, the control signals p ₀ , p ₁ , p _m-1 output from the modulator 14 according to the input signals. Is asserted as appropriate and goes high (“1”).

The MOS transistors 22, 24, and 26 of the switching current sources 15, 16, and 17 are turned on only while the control signals p ₀ , p ₁ , and p _m-1 are at a high level. Thereby, in the switching current source in which the MOS transistor is turned on, a current flows through the inductor of the switching current source. No current flows through the inductor of the switching current source in which the MOS transistor is not turned on. Energy is stored in the inductors 21, 23, 25 through which the current flows.

The asserted control signals p ₀ , p ₁ , and p _m−1 return to a low level (“0”) after a certain period. Due to the inversion of the signal level, the MOS transistors 22, 24, and 26 in the conductive state of the switching current sources 15, 16, and 17 return to the non-conductive state. Then, the energy stored in the inductors 21, 23, 25 of the switching current sources 15, 16, 17 becomes current and flows through the rectifiers 18, 19, 20, and is summed and supplied to the amplifier 11 as a power supply current. Is done. The amplifier 11 operates with high power supply efficiency by the supplied power supply current, and outputs a signal composed of a modulated wave with a change in amplitude.

  As described above, according to the embodiment, it is possible to amplify a high-frequency signal by operating the amplifier 11 at a sufficiently high speed with high power supply efficiency without an analog circuit, a feedback loop, or a large smoothing capacitor. . Therefore, an analog circuit, a feedback loop, and a large smoothing capacitor are not required. In addition, there is an effect that it is possible to cope with a wideband signal without reducing the efficiency.

  In addition, since the power consumption of the power amplifier is small and the power amplifier has high power supply efficiency characteristics, when the power amplifier according to the embodiment is applied to a mobile phone system or other wireless communication system, the following An effect is obtained. When applied to a mobile device, a device capable of outputting necessary RF power for a long time using a small and light battery can be realized. When applied to a fixed station or base station, power consumption and heat generation are reduced, so that the apparatus can be reduced in size, increased in reliability, and extended in life. Moreover, the convenience at the time of installing an apparatus improves.

  As described above, the present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the number of switching current sources may be one. In this case, a 1-bit control signal is output from the modulator 14.

  As described above, the power amplifier according to the present invention is useful for a power amplifier that amplifies a millimeter-wave electrical signal from a wide-band microwave, and particularly, a mobile device of a mobile phone system or other wireless communication system, or a fixed It is suitable for a power amplifier that amplifies a transmission signal or a reception signal in a station or a base station.

It is a figure which shows the structure of the power amplifier concerning embodiment of this invention. It is a figure which shows the structure of LINC which is one of the conventional power amplifiers. It is a figure which shows the structure of the Doherty amplifier which is one of the conventional power amplifiers. It is a figure which shows the structure of ET or EER which is one of the conventional power amplifiers.

Explanation of symbols

11 Amplifier 14 Modulator 15, 16, 17 Switching current source 18, 19, 20 Rectifier 21, 23, 25 Inductor 22, 24, 26 Transistor

Claims (5)

An amplifier for amplifying a high-frequency signal;
A plurality of switching current sources for supplying current to the amplifier;
A modulator for controlling the amount of current supplied from the plurality of switching current sources to the amplifier according to an envelope component of the high-frequency signal;
A power amplifier comprising: The switching current source includes a transistor that switches between a conductive state and a non-conductive state based on an output signal of the modulator, and an inductor that stores energy when the transistor is conductive.
The power amplifier according to claim 1, wherein after the transistor changes from a conductive state to a non-conductive state, the energy stored in the inductor is caused to flow as a current to the amplifier.   The power amplifier according to claim 1, wherein currents flowing from a plurality of the switching current sources are added together and supplied to the amplifier. A plurality of rectifiers for rectifying currents flowing from the plurality of switching current sources;
The power amplifier according to claim 3, wherein currents flowing from a plurality of the switching current sources are added together after being rectified by the rectifier. An amplifier for amplifying a high-frequency signal;
A switching current source for supplying current to the amplifier;
A modulator for controlling an amount of current supplied from the switching current source to the amplifier according to an envelope component of the high-frequency signal;
A power amplifier comprising:

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