JP2000252760A - Feedforward power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a feedforward power amplifier that can compensate distortion even in the case of a system where channels are densely arranged. SOLUTION: A CDMA pilot signal modulator 12 receives a pilot signal generated by a pilot signal generator 13, and a modulation signal for a frequency band in response to at least one channel component in the input signal is coded by according to two orthogonal codes different from the input signal and the coded signals are superimposed and summed. Thus, in a system where channels are densely arranged with a high frequency efficiency, distortion can effectively be compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed-forward amplifier distortion compensation system mainly used for a base station apparatus of a mobile communication device.

[0002]

2. Description of the Related Art In recent years, a power amplifier having high output and good linearity has been required for a base station apparatus of mobile communication equipment.
This is realized by performing distortion compensation by a feedforward method.

FIG. 3 shows an example of the configuration of a conventional feedforward power amplifier. In FIG. 3, 21 is an input terminal, 31 is an output terminal, 22 is a power divider, 25 and 28 are power combiners, 23 and 29 are vector adjusters, 24 is a main amplifier, 26 and 27 are delay circuits, and 30 is Auxiliary amplifier, 3
2, 34 and 36 are combiners, 33 is a pilot signal generator, 35 is an input signal detector, and 37 is a pilot signal detector. Also, the power distributor 22, the power combiners 25 and 2
8 and the symbol a attached to the vector adjusters 23 and 29
Ｐp represents each port.

The operation of the foot-forward power amplifier configured as described above will be described below.

An input signal containing a multi-channel component input from an input terminal 21 is split into two by a power splitter 22. One of the two divided output signals is a vector adjuster 2
The signal is input to one of the two inputs of the combiner 32 via 3. The pilot signal generated by the pilot signal generator 33 is input from the other input of the combiner 32, is added and synthesized with the input signal, and is amplified by the main amplifier 24.
It is input to port g of power combiner 25. At this time, in addition to the input signal component and the pilot signal, a signal including a distortion component due to intermodulation is input due to the non-linearity of the main amplifier 24. The other signal split into two by the power divider 22 is input to the port h of the power combiner 25 via the delay circuit 26. An input signal from the main amplifier 24 is output from a port i of the power combiner 25, and a composite signal of an input signal from the main amplifier 24 and an input signal from the delay circuit 26 is output from a port j. At this time, port j
The input signal component of the output signal from the
Through the input signal component detector 35, and adjusts the vector adjuster 23 and the delay circuit 26 so that the level of the input signal component is minimized. A signal including only the distortion component and the pilot signal is output. This output signal is
The signal is input to the vector adjuster 29 via the combiner 34,
After being amplified by the auxiliary amplifier 30, it is input to the port o of the power combiner 28.

On the other hand, a signal including an input signal component, a distortion component, and a pilot signal output from port i is input to port n of power combiner 28 via delay circuit 27. Here, if the input signal components input to the port n and the port o are equal in phase and opposite in phase, the distortion component and the pilot signal are canceled out, so that only the pilot signal among the signals output from the port p is combined. By using a pilot signal detector 37 via a detector 36 and adjusting the vector adjuster 29 and the delay circuit 27 so that the pilot signal is minimized, the distortion component and the pilot signal are output from the output terminal 31. A signal of only the canceled input signal component is output.

FIGS. 4A to 4D show ports a,
The frequency spectrum of the signal at g, j, p is shown.

[0008]

In the conventional feedforward distortion compensation system, the channel interval is wider than the occupied band of the signal in each channel to be amplified. It was easy to detect. However, in order to increase the frequency use efficiency, it is desirable to arrange the channels densely. For example, in the case of the W-CDMA system, the occupied bandwidth of the signal is 4.096 MHz, whereas the channel interval is 5 MHz. And the channel arrangement is dense. However, if the frequency of the pilot signal matches the frequency of the input signal, normal feedforward control cannot be performed.
There is a problem that it is difficult to arrange pilot signals in a system having a close channel interval as in the system.

An object of the present invention is to provide a feedforward power amplifier capable of performing distortion compensation even in a system having a close channel interval, in consideration of such problems of the conventional feedforward distortion compensation system. Things.

[0010]

SUMMARY OF THE INVENTION The present invention provides at least two
An input signal encoded with two mutually orthogonal codes is 2
A first power divider for distributing, a first vector adjuster for adjusting an amplitude and a phase of one output of the first power divider, a pilot signal generating means for generating a pilot signal, Pilot modulation means for encoding and superimposing and adding a pilot signal with at least two mutually orthogonal codes different from the input signal to a modulation signal in a frequency band corresponding to at least one channel component; A main amplifier for amplifying the output, a first delay circuit for delaying the other output signal of the first power divider, an output signal of the main amplifier and an output signal of the first delay circuit, and A first power combiner having an output signal of the amplifier as a first output and a second output as a composite signal of the output signal of the main amplifier and the output signal of the first delay circuit; A second delay circuit for delaying the first output signal of the adult device, a second vector adjuster for adjusting the second output of the amplitude and phase of the first power combiner, the second
, A second power combiner for combining an output signal of the auxiliary amplifier and an output signal of the second delay circuit, and a second power combiner of the first power combiner. An input signal level detector for detecting a level of a composite signal of the output signal of the main amplifier and the output signal of the first delay circuit from the output, and controlling the first vector adjuster based on the detection result; Pilot signal detecting means for demodulating and detecting a coded pilot signal from an output signal of the power combiner, and controlling a second vector adjuster such that the level of the detected pilot signal is reduced. Feedforward power amplifier.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment.

FIG. 1 is a block diagram of a feedforward power amplifier according to an embodiment of the present invention. FIG.
, 1 is an input terminal, 11 is an output terminal, 2 is a power divider, 5, 8 are power combiners, 3, 9 are vector adjusters,
4 is a main amplifier, 6 and 7 are delay circuits, 10 is an auxiliary amplifier,
14 and 16 are combiners, 12 is a CDMA pilot signal modulator, 13 is a pilot signal generator, 15 is an input signal level detector, and 17 is a CDMA pilot signal detector. Symbols a to p assigned to the power distributor 2, the power combiners 5, 8 and the vector adjusters 3, 9 represent respective ports.

The operation of the foot forward power amplifier configured as described above will be described below.

Here, it is assumed that the input signal is a carrier having at least one or more channel components encoded with at least two mutually orthogonal codes.

First, an input signal from an input terminal 1 is split into two by a power splitter 2. One of the two split outputs is
The signal is input from port b to one of the two inputs of the CDMA pilot signal modulator 12 via the vector adjuster 3. On the other hand, the pilot signal generated by the pilot signal generator 13 is input from the other input of the CDMA pilot signal modulator 12, and is applied to a modulated signal of a frequency band corresponding to at least one or more channel components of the input signal. After being encoded with at least two mutually orthogonal codes different from the input signal and superimposed and added, the signals are amplified by the main amplifier 4 and input to the port g of the power combiner 5.
At this time, a signal containing a distortion component due to intermodulation in addition to the input signal component due to the non-linearity of the main amplifier 4 is input.

The other signal divided into two by the power divider 2 is input from the port c via the delay circuit 6 to the port h of the power combiner 5. An output signal of the main amplifier 4 is output from a port i of the power combiner 5, and a composite signal of an output signal of the main amplifier 4 and an output signal of the delay circuit 6 is output from a port j. At this time, only the input signal component of the output from the port j is detected by the input signal level detector 15 via the coupler 14 and the vector adjuster 3 and the vector adjuster 3 are set so that the level of the input signal component is minimized. By adjusting the delay circuit 6, only the distortion component from which the input signal component is canceled out from the port j and the pilot signal which is encoded by at least two mutually orthogonal codes and superimposed and added to the input signal component are added. A signal is output. This output signal is input to the vector adjuster 9 via the coupler 14, amplified by the auxiliary amplifier 10, and then input to the port o of the power combiner 8.

The signal including the input signal component, the distortion component, and the pilot signal output from the port i of the power combiner 5 is input to the port n of the power combiner 8 via the delay circuit 7. Here, if the distortion components input to the port n and the port o are equal in amplitude and opposite in phase, the distortion component and the pilot signal are canceled out, so that only the pilot signal out of the signals output from the port p is combined. 16 and demodulated using a CDMA pilot signal detector 17 and adjusting the vector adjuster 9 and the delay circuit 7 so that the level of the demodulated pilot signal is minimized. And a signal of only the input signal component in which the pilot signal component is canceled.

FIGS. 2A to 2D show ports a,
FIG. 2 is a diagram illustrating an example of a frequency spectrum of a signal at g, j, and p. In this way, by adopting the configuration of FIG. 1, in a feedforward power amplifier, a pilot signal is generated between a channel and an adjacent channel. Since there is no need to apply the voltage, it is possible to effectively perform distortion compensation in a system with high frequency efficiency in which channels are densely arranged.

As described above, according to the present embodiment, a code-encoded and frequency-spread input signal is
By superimposing and adding a pilot signal that is code-encoded by a code different from the input signal and spread in frequency, it is possible to effectively perform distortion compensation even in a system with high frequency efficiency where channels are densely arranged. Become.

Although the above embodiment has been described assuming that the number of channels of the input signal is four, it goes without saying that the number of channels is not limited to this.

Further, in the above-described embodiment, the superposition and addition of the coded pilot signal is performed on one channel. However, the present invention is not limited to this, and the superposition and addition of the pilot signal may be performed on two or more channels. Good.

[0022]

As is apparent from the above description, the present invention is applicable to at least one or more channel components of an input signal composed of multi-channel components encoded by at least two mutually orthogonal codes. Since the pilot signal is encoded with at least two mutually orthogonal codes different from the input signal and superimposed and added to the modulated signal in the frequency band, it is not necessary to allocate a specific frequency for the pilot signal. Therefore, there is no need to apply a pilot signal between a channel and an adjacent channel, so that distortion compensation can be effectively performed even in a high frequency efficiency system in which channels are densely arranged. Have.

[Brief description of the drawings]

FIG. 1 is a block diagram of a feedforward power amplifier according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a frequency spectrum of a signal at ports a, g, j, and p in the embodiment.

FIG. 3 is a block diagram of a conventional feedforward power amplifier.

FIG. 4 is a diagram showing a frequency spectrum of a signal at ports a, g, j, and q in a conventional example.

[Explanation of symbols]

 1,21 input terminal 2,22 power divider 3,9,23,29 vector adjuster 4,24 main amplifier 5,8,25,28 power combiner 6,7,26,27 delay circuit 10,30 auxiliary amplifier 11, 31 Output terminal 12 CDMA pilot signal modulator 13, 33 Pilot signal generator 14, 16, 32, 34, 36 Combiner 15, 35 Input signal level detector 17 CDMA pilot signal detector 37 Pilot signal detector

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroaki Kosugi 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Shinichi Kugo 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Telecommunications Industry Co., Ltd. F term (reference) 5J090 AA04 AA41 CA01 CA21 CA22 CA26 CA27 FA08 FA17 GN03 GN05 GN07 HN03 HN08 KA15 KA16 KA23 KA26 KA53 KA55 KA68 MA14 MA20 SA14 TA01 TA03

Claims (2)

[Claims] 1. A first power divider for dividing an input signal encoded by at least two mutually orthogonal codes into two, and a first power divider for adjusting an amplitude and a phase of one output of the first power divider. A vector adjuster, a pilot signal generating means for generating a pilot signal, and at least two signals different from the input signal with respect to a modulation signal in a frequency band corresponding to at least one channel component of the input signal.
Pilot modulation means for encoding and superimposing and adding a pilot signal with two mutually orthogonal codes, a main amplifier for amplifying the output of the pilot modulation means, and a second amplifier for delaying the other output signal of the first power divider. 1, the output signal of the main amplifier and the output signal of the first delay circuit are combined, and the output signal of the main amplifier is used as a first output, and the output signal of the main amplifier and the first A first power combiner that uses the output signal of the delay circuit as a second output signal as a second output signal, a second delay circuit that delays a first output signal of the first power combiner, 1st power combiner second
A second vector adjuster for adjusting the amplitude and phase of the output of the second amplifier, an auxiliary amplifier connected to the second vector adjuster, and an output signal of the auxiliary amplifier and an output signal of the second delay circuit. A second power combiner for combining, and a level of a combined signal of the output signal of the main amplifier and the output signal of the first delay circuit is detected from a second output of the first power combiner, and An input signal level detector that controls the first vector adjuster based on the detection result and a pilot signal encoded from an output signal of the second power combiner are demodulated and detected, and the detected A feed-forward power amplifier, comprising: pilot signal detection means for controlling the second vector adjuster so that the level of the pilot signal is reduced. 2. An input signal comprising a carrier having at least two different frequency components, wherein said pilot modulating means is configured to control a carrier of at least one of said at least two frequencies. And superimposing and adding pilot signals encoded by at least two mutually orthogonal codes.
3. The feedforward power amplifier according to 1.