JP2002368716A - Ofdm high efficiency power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an OFDM high efficiency power amplifier that can enhance the efficiency of power amplification of a signal such as an OFDM signal where a peak signal sometimes appears with a small-size and reduced weight that can reduce the power consumption. SOLUTION: The OFDM high efficiency power amplifier is provided with a basic part amplifier means 112 that can linearly amplify power of an OFDM signal received at a prescribed signal level or below, a peak part amplifier means 313 that amplifies power of the peal level of the OFDM signal in excess of the prescribed level at a higher efficiency than that of the basic part amplifier means 112 when receiving the peak level of the OFDM signal in excess of the prescribed signal level, a composite means 114 that composites an output signal from the basic part amplifier means 112 with an output signal from the peak part amplifier means 313, and pre-distortion means 211, 312 that convert the signal level in order to compensate the nonlinearity in the amplifier characteristic of one or both of the basic part amplifier means 112 and the peak part amplifier means 313.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an OFDM (Orthogonal Frequency Division Mu) which requires good linearity.
The present invention relates to an amplifier used for power amplification of a signal, and more particularly, to an OFDM high-efficiency power amplifier for highly efficient power amplification.

[0002]

2. Description of the Related Art Conventionally, in a power amplifier of an OFDM signal (see FIG. 5) composed of a large number of carriers and having a peak signal which is higher than the average signal level by a few dozen dB, the power amplifier has a non-linear characteristic. It is known that a modulation component is generated, thereby deteriorating the equivalent CN ratio. In the case of a digital signal, the deterioration of the equivalent CN ratio causes an increase in the error rate. Therefore, in order to prevent the deterioration of the equivalent CN ratio, a power amplifier of the OFDM signal is required to have amplification characteristics with good linearity.

[0003] In order to ensure the linearity of the amplification characteristic, for example, a class-A operation power amplifier is used in a conventional OFDM transmitter. Further, as a class A operation power amplifier, OF
In order to properly amplify the power of the peak signal sometimes appearing in the DM signal, the peak signal is 10d higher than the average signal level.
A device capable of power-amplifying an input signal higher than B is used. As a result, the conventional O.S.
As a transmitter of the FDM signal, a transmitter capable of outputting 10 kW or more is used even when an antenna output requires only 1 kW.

As described above, in order to secure the linearity of the amplification characteristics over a wide range, a conventional power amplifier for amplifying an OFDM signal requires a back-off amount of 10 dB or more. Also, as is well known, in a class A operation power amplifier, the power supply voltage (also referred to as a drain voltage), the bias voltage, the output idle current, and the like are affected by the back-off amount regardless of the waveform of the input OFDM signal. It is kept at a constant value according to it.

[0005]

As described above, the conventional O
In a power amplifier for amplifying an FDM signal, a large idle current is always supplied in preparation for a peak signal sometimes appearing in an input OFDM signal, and a large amount of power is continuously consumed. Therefore, the efficiency of a transmitter is low, and the power required for transmission is low. There was a problem that reduction could not be achieved.

The present invention has been made to solve such a problem, and an object of the present invention is to improve the efficiency of power amplification in a power amplification of a signal such as an OFDM signal in which a peak signal sometimes appears, and to reduce the size of the power amplification. An object of the present invention is to provide an OFDM high-efficiency power amplifier capable of reducing the weight and power consumption.

[0007]

In consideration of the above points, the invention according to claim 1 provides an input OFD at a signal level or lower.
A basic section amplifying means capable of linearly power-amplifying the M signal; a peak section amplifying means for amplifying the OFDM signal exceeding the predetermined signal level; Means for synthesizing a signal which has been power-amplified by the means, wherein the peak section amplifying section power amplifies a portion of the OFDM signal exceeding the predetermined signal level more efficiently than the basic section amplifying section. Configuration.

[0008] With this configuration, the O signal below a predetermined signal level can be used.
When the basic portion, which is an FDM signal, is input, power amplification is performed linearly, and OFDM signals exceeding a predetermined signal level are output.
When the peak portion, which is a signal, is input, the portion below the predetermined signal level is linearly amplified, and the portion above the predetermined signal level is power-amplified with high efficiency.
An OFDM high-efficiency power amplifier capable of high-efficiency and amplification characteristics with good linearity can be realized. In addition, since the power can be efficiently amplified, the size and weight of the device can be reduced, and the power consumption can be reduced.

According to a second aspect of the present invention, in the first aspect, the basic unit amplifying unit is a class A power amplifier, and the peak unit amplifying unit is a class AB operating amplifier and a class B operating amplifier. , An amplifier operating in class C, or an amplifier operating in class D.

[0010] With this configuration, the basic portion of the OFDM signal is subjected to class A operation power amplification with high linearity, and the peak portion exceeding a predetermined signal level is subjected to the above operations only when the peak portion occurs. High-efficiency power amplification is performed using any of the amplifiers, and the amplified OFDM signal is generated by combining with the amplified basic part. An efficient power amplifier can be realized.

According to a third aspect of the present invention, in the first or second aspect, the basic unit amplifying means converts a signal amplitude for compensating for non-linearity in amplification characteristics to an input OFDM signal. On the other hand, it has a configuration further provided with a pre-distortion means to be performed in advance.

With this configuration, it is possible to compensate for the nonlinearity of the basic section amplifying means using the pre-distortion means.
O with high efficiency and capable of improving the linearity of amplification characteristics
An FDM high efficiency power amplifier can be realized.

According to a third aspect of the present invention, in the first aspect of the present invention, the peak section amplifying means converts the signal amplitude for compensating for nonlinearity in the amplification characteristic. , For the input OFDM signal,
It has a configuration further provided with a pre-distortion means for performing in advance.

According to this configuration, the nonlinearity of the peak section amplifying means for performing high-efficiency power amplification using the pre-distortion means can be compensated, so that the OFDM which is highly efficient and can improve the linearity of the amplification characteristic can be achieved. A highly efficient power amplifier can be realized.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An OFDM high-efficiency power amplifier according to a first embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1A is a block diagram illustrating a configuration of an OFDM high-efficiency power amplifier according to the first embodiment of the present invention. The OFDM high-efficiency power amplifier 100 shown in FIG.
2. It is composed of a peak section amplifying means 113 and a combining means 114.

The signal distribution unit 111 outputs the input OFDM signal (RF band) to the basic unit amplification unit 112 and the peak unit amplification unit 113. The basic unit amplifying unit 112 is an amplifying unit that amplifies a known class A operation or the like and has amplification characteristics with good linearity. Hereinafter, in the first embodiment, the description will be given assuming that the basic unit amplifying means 112 is a class A amplifier. The basic unit amplifier 112 amplifies a basic unit (see FIG. 1B) of an OFDM signal described below.

The above-mentioned basic part is, for example, an OFDM signal shown in FIG. 1B whose amplitude falls within a range sandwiched between two thick solid lines 121 shown in FIG. 1B. Say. In addition, the peak portion refers to an OFDM signal other than this, that is, a signal whose amplitude is out of the range between the two thick solid lines 121. These two thick solid lines 1
The level corresponding to the amplitude indicated by 21 is a predetermined signal level determined by the characteristics of the basic section amplifying means 112 and the peak section amplifying means 113. Hereinafter, this "predetermined signal level" is referred to as a reference signal level.

The peak section amplifying means 113 is an amplifying means for efficiently amplifying a known class B operation or the like. Hereinafter, the first
In the embodiment, the peak section amplifying means 113 will be described as a class B push-pull amplifier. Note that the peak section amplifying means 113 is not necessarily a push-pull amplifier, but is a push-pull amplifier for convenience of explanation of the operation (for ease of explanation).

The basic section amplifying means 112 amplifies the OFDM signal in a class A operation when the OFDM signal is equal to or lower than the reference signal level.
The amplified signal is output to the combining means 114. Note that the linearity of the amplification characteristic is not guaranteed for the peak portion. The peak section amplifying unit 113 amplifies the OFDM signal in a class B operation, and outputs the amplified signal to the combining unit 114.
In the amplification of the class B operation, by appropriately setting the bias, a signal portion exceeding the above-described reference signal level when a peak portion is input can be selectively and efficiently amplified. Then, when the basic part is input, it does not operate.

Referring to FIG. 4, a description will be given of signal components amplified and output by the basic section amplifying section 112 and the peak section amplifying section 113. Curve A in FIG. 4 is a signal component that is amplified and output by the basic unit amplifying unit 112 when there is a signal input on the horizontal axis.
Is a signal component that is amplified and output by the peak section amplifying unit 113 when a signal is input on the horizontal axis.

As is apparent from FIG. 4, when the input OFDM signal is only the basic part, the input OFDM signal is amplified only by the basic part amplifying means 112, and when the input OFDM signal is the peak part, the input OFDM signal is amplified. The signal is amplified by the basic section amplification section 112 and the peak section amplification section 113. Therefore, when the input signal level exceeds the reference signal level, the peak section amplifying means 113 starts amplification.

As is clear from the above description, the sum of the output of the basic section amplifying means 112 and the output of the peak section amplifying means 113 is the output signal of the peak section after amplification. The output after amplification of the peak portion is shown by a curve B in FIG. The amplified output of the peak portion can be regarded as a signal amplified by one amplifier having a linear amplification factor.

The synthesizing means 114 includes a basic part amplifying means 112
And the output signal of each time from the peak part amplifying means 113 are combined to obtain the output signal of the OFDM high efficiency power amplifier 100. Note that the synthesis performed by the synthesis unit 114 can be performed by series synthesis in which the amplified basic portion and the amplified peak portion are superimposed, but a phase synthesis method disclosed in Japanese Patent No. 3056091 can be used. Can be synthesized more efficiently. Also, the basic part amplifying means 112
And the phase of the output of the peak part amplifying means 113 need to be in phase. However, since both means are constituted by analog circuits, the in-phase can be secured only by adjusting the length of the wiring cable. .

As described above, the OFDM high-efficiency power amplifier according to the first embodiment of the present invention performs power amplification of Class A operation for an OFDM signal (basic part) having a predetermined signal level or lower, and performs predetermined amplification. OFDM exceeding the signal level of
For the signal (peak portion), only when the peak portion occurs, high-efficiency power amplification of class B operation such as class B push-pull amplification is performed.
Since a DM signal is generated, it is possible to realize an OFDM high-efficiency power amplifier that can achieve high efficiency and amplification characteristics with good linearity. In addition, since the power can be efficiently amplified, the size and weight of the device can be reduced, and the power consumption can be reduced.

FIG. 2 is a circuit diagram showing a second embodiment according to the present invention.
FIG. 3 is a block diagram illustrating a configuration of an FDM high-efficiency power amplifier. OFDM high efficiency power amplifier 2 according to second embodiment
Reference numeral 00 denotes a configuration in which a first pre-distortion unit 211 and a second pre-distortion unit 212 are added to the OFDM high-efficiency power amplifier 100 according to the first embodiment. Note that the peak section amplifying section 213 according to the second embodiment is different from the peak section amplifying section 11 according to the first embodiment.
Different from No. 3, this is an amplifying means for amplifying a known class AB operation or the like.

In the following, the peak part amplifying means 213 is set to AB
Class push-pull amplifier, and among the constituent means of the high-efficiency power amplifier 200 according to the second embodiment, the same constituent means as those of the OFDM high-efficiency power amplifier 100 according to the first embodiment are the same. And the description is omitted.

Here, each pre-distortion means 21
Numerals 1 and 212 are means for compensating for non-linearity in the amplification characteristics of the amplification means 112 and 213, such as a known pre-distortion circuit. That is, the first pre-distortion unit 211 increases the nonlinearity of the amplification characteristic of the basic unit amplification unit 112 so as to improve the linearity of the output signal from the basic unit amplification unit 112 with respect to the output signal from the signal distribution unit 111. This is a means for converting the signal amplitude of the output signal from the signal distribution means 111 in advance and compensating for it in consideration of the characteristics.

Similarly, the second pre-distortion means 2
Numeral 12 designates a function of the peak amplifying means 213 (class push-pull amplifier) so as to improve the linearity of the output signal from the signal distributing means 111 from the peak amplifying means 213 (class push-pull amplifier). This is a means for converting the signal output from the signal distribution unit 111 in advance to convert the signal amplitude in consideration of the non-linearity in the amplification characteristic, thereby performing compensation.

From the viewpoint of compensation for non-linearity,
Even if either the first pre-distortion means 211 or the second pre-distortion means 212 is omitted, the non-linearity in the amplification characteristics of the power amplification means connected to the remaining pre-distortion means remains without being omitted. It is clear that can be improved.

As described above, the OFDM high-efficiency power amplifier according to the second embodiment of the present invention provides the power of the OFDM signal by providing the pre-distortion means between the signal distribution means and each amplification means. An OFDM high-efficiency power amplifier capable of improving the linearity of amplification characteristics in amplification can be realized. Further, AB as the peak section amplifying means 213
By using the class power amplifying means, it is possible to realize an OFDM high-efficiency power amplifier capable of reducing power consumption by reducing idle current and the like, as compared with the case of using a class A operation power amplifier.

FIG. 3 is a circuit diagram showing an O-type oscillator according to a third embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of an FDM high-efficiency power amplifier. OFDM high-efficiency power amplifier 3 according to third embodiment
00 is a class AB push-pull amplifier used as the peak amplifier 213 of the OFDM high-efficiency power amplifier 200 according to the second embodiment replaced with a class C push-pull amplifier or other power amplifier of another operation that can increase the efficiency. It is a thing. In the following, the same components as those of the OFDM high-efficiency power amplifier 200 according to the second embodiment are denoted by the same reference symbols, and description thereof is omitted.

The peak amplifying means 313 is an amplifying means for performing high-efficiency power amplification, such as a class C push-pull amplifier as described above. The peak section amplifying means 313
Since power amplification such as class operation is performed, the linearity of the amplification characteristic is reduced. Second pre-distortion means 312
Are used to compensate for this reduction in linearity.
And the peak amplifying means 313.

From the viewpoint of compensation for non-linearity,
Even if the first pre-distortion means 211 is omitted, O
Clearly, the nonlinearity in the amplification characteristics of the entire FDM high efficiency power amplifier 300 can be improved. Further, as the peak amplifying means 313, a class D push-pull amplifier of a more efficient switching amplification type may be used instead of the class C push-pull amplifier.

As described above, in the OFDM high-efficiency power amplifier according to the third embodiment of the present invention, the pre-distortion means is provided between the signal distribution means and each amplification means, and if there is no signal input, the power is reduced. By using a class C power amplifier or the like that does not cause loss for amplification of the peak portion, it is possible to realize an OFDM high-efficiency power amplifier that has high efficiency and an amplification characteristic with good linearity.

[0035]

As described above, according to the OFDM of the present invention,
The high-efficiency amplifier performs power amplification with good linearity such as class A operation power amplification for the signal component of the OFDM signal below a certain signal level, and when a signal exceeding the signal level is input, if there is no signal input, To provide an OFDM high-efficiency power amplifier capable of realizing high-efficiency and high-linearity amplification characteristics by starting power amplification such as class B operation without power loss and combining amplified signals. be able to.

Further, the amount of back-off can be reduced by eliminating the necessity of linearly amplifying signals of a wide range of signal levels, which has been performed by a class-A power amplifier in a conventional power amplifier for OFDM signals. OFDM that can reduce the size and weight of the device and reduce power consumption
A highly efficient power amplifier can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an OFDM high-efficiency power amplifier according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an OFDM high-efficiency power amplifier according to a second embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of an OFDM high-efficiency power amplifier according to a third embodiment of the present invention.

FIG. 4 shows an input signal level of an OFDM signal and OF after amplification.
FIG. 4 is a diagram schematically illustrating a relationship between a DM signal and a signal level.

FIG. 5 is a diagram illustrating an example of a time waveform of an OFDM signal.

[Explanation of symbols]

100, 200, 300 OFDM high-efficiency power amplifier 111 Signal distribution means 112 Basic part amplifying means (Class A amplifier) 113 Peak part amplifying means (Class B push-pull amplifier) 114 Synthesis means 121 Reference signal level 122 Basic part 123 Peak part 211 First pre-distortion means 212, 312 Second pre-distortion means 213 Peak amplification means (Class AB push-pull amplifier) 313 Peak amplification means (Class C push-pull amplifier)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasuaki Nishida 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Center F-term (reference) 5J069 AA01 AA21 AA41 AA62 AA63 AA64 AA65 AA66 CA21 CA36 CA92 FA15 KA00 KA68 KC06 KC07 SA14 TA01 TA02 TA06 5J092 AA01 AA21 AA41 AA62 AA63 AA64 AA65 AA66 CA21 CA36 CA92 FA15 KA00 KA68 SA14 TA01 TA02 TA06 5K022 DD01 DD21

Claims (4)

[Claims] 1. A basic part amplifying means capable of linearly amplifying an input OFDM signal below a predetermined signal level, a peak part amplifying means for amplifying the OFDM signal exceeding the predetermined signal level, and the basic part amplifying means. Synthesizing means for synthesizing the signal amplified by the power and the signal amplified by the peak part amplifying means, wherein the peak part amplifying part converts the portion of the OFDM signal exceeding the predetermined signal level into An OFDM high-efficiency power amplifier, which amplifies power more efficiently than a basic unit amplifying means. 2. The power amplifier according to claim 1, wherein the amplification unit is a class A power amplifier, and the peak amplification unit is a class AB operation amplifier, a class B operation amplifier, a class C operation amplifier, or a D class operation amplifier.
2. An OFDM high-efficiency power amplifier according to claim 1, wherein the amplifier is one of class-operated amplifiers. 3. The pre-distortion means further comprising: a pre-distortion means for previously performing conversion of a signal amplitude for compensating for non-linearity in amplification characteristics with respect to an input OFDM signal. The OFDM high-efficiency power amplifier according to claim 1 or 2. 4. The peak amplifying means further comprises a pre-distortion means for preliminarily converting an input OFDM signal into a signal amplitude for compensating for nonlinearity in amplification characteristics. The OFDM high-efficiency power amplifier according to any one of claims 1 to 3.