Amplifiers – Hum or noise or distortion bucking introduced into signal...
Reexamination Certificate
2003-05-28
2004-12-21
Choe, Henry (Department: 2817)
Amplifiers
Hum or noise or distortion bucking introduced into signal...
C330S151000
Reexamination Certificate
active
06833758
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to power amplifiers and, more specifically, to a power amplifier capable of compensating for distortion occurring during signal amplification by pre-distortion.
2. Description of the Background Art
In recent years, mobile communications have required a transmitting apparatus located at a base station to collectively amplify a large number of signal channels. For this reason, a highly-efficient power amplifier with more linearity has been demanded. In order to increase the linearity of the power amplifier, adoption of a circuit for compensating for distortion, such as the one employing a pre-distortion scheme, is a requisite,.
FIG. 16
is a block diagram illustrating the configuration of a conventional power amplifier. The power amplifier illustrated in
FIG. 16
includes an input terminal
601
, an output terminal
602
, a power splitter
603
, a delay unit
604
, a distortion generating circuit
605
, a variable attenuator
606
, a variable phase shifter
607
, a power combiner
608
, a power amplifying circuit
609
, a directional coupler
610
, and a control unit
611
.
In the above-configured amplifier capable of compensating for distortion by pre-distortion, a carrier signal supplied through the input terminal
601
is split by the power splitter
603
into two carrier signals. Based on one of these two carrier signals, the distortion generating circuit
605
generates a distortion signal. This distortion signal is adjusted in amplitude and phase by the variable attenuator
606
and the variable phase shifter
607
, respectively, and is then supplied to the power combiner
608
. The other one of the two carrier signals obtained by the power splitter
603
is, on the other hand, delayed by the delay unit
604
, and is then supplied to the power combiner
608
. The power combiner
608
combines the distortion signal adjusted in amplitude and phase and the delayed carrier signal together for output to the power amplifying circuit
609
. The signal output from the power combiner
608
is amplified by the power amplifying circuit
609
, and is then output to outside of the power amplifier from the output terminal
602
.
Provided between the power amplifying circuit
609
and the output terminal
602
is a directional coupler
610
. The directional coupler
610
divides the signal output from the power amplifying circuit
609
into two signals, and one of these two signals is output to the control unit
611
. The control unit
611
controls the variable attenuator
606
and the variable phase shifter
607
so that inter modulation distortion (hereinafter simply referred to as “distortion”) occurring at the power amplifying circuit
609
while amplifying the carrier signal is equal in amplitude and opposite in phase to the distortion signal supplied to the power combiner
608
.
As described above, in the conventional power amplifier capable of compensating for distortion by pre-distortion, the distortion signal is generated so as to be equal in amplitude and opposite in phase to the distortion signal occurring at the power amplifying circuit
609
while amplifying the carrier signal. Furthermore, the generated distortion signal is added in advance to the carrier signal to be supplied to the power amplifying circuit
609
. That is, distortion components equal in amplitude and opposite in phase are injected to the input side of the amplifier. With this, the conventional power amplifier reduces the distortion occurring at the power amplifying circuit
609
.
The conventional power amplifier illustrated in
FIG. 16
, however, has some problems as follows. In the distortion components occurring at the power amplifying circuit
609
(hereinafter referred to as “IM3 components”), if ternary distortion components occurring at a low frequency side (hereinafter referred to as “IM3L components”) and ternary distortion components occurring at a high frequency side (hereinafter referred to as “IM3U components”) have a significant level difference, it is impossible to sufficiently suppress both of these IM3L and IM3U components. This is because, if the distortion components (IM3L and IM3U components) have a large asymmetric characteristic as stated above, it is difficult for the distortion generating circuit
605
to generate a distortion signal which is equal in amplitude and opposite in phase to both of the IM3L and IM3U components.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a power amplifier capable of compensating for distortion by pre-distortion and achieving a large distortion suppressing effect even if IM3L components and IM3U components both occurring at the power amplifier have a large level difference.
The present invention has the following features to attain the object mentioned above.
A first aspect of the present invention is directed to a power amplifier which amplifies an original signal including a plurality of signals of different frequencies. The power amplifier includes:
a signal input section for inputting the original signal;
an amplifying section for amplifying the original signal input from the signal input section;
a signal output section for outputting the signal amplified by the amplifying section to outside of the power amplifier;
an envelope signal generating section for generating an envelope signal having components identical to envelope components included in the original signal;
a distortion signal generating section for generating, based on the original signal, a distortion signal for canceling distortion components occurring while the original signal is amplified by the amplifying section;
a first envelope signal injecting section for injecting the envelope signal to a signal amplifying route from the signal input section to the signal output section so as to eliminate an asymmetric characteristic of the distortion components; and
a distortion signal injecting section for injecting the distortion signal to the signal amplifying route so as to suppress the distortion components.
In the above first aspect, the envelope signal can eliminate the asymmetric characteristic of the distribution components occurring at the power amplifier. Furthermore, the distortion signal can reduce the distortion components occurring at the power amplifier. That is to say, with the use of two signals, the envelope signal and the distortion signal, elimination of the asymmetric characteristic of the distortion component and reduction of the distortion components are performed individually. In a conventional method, it is impossible to generate a distortion signal which coincides with the asymmetric characteristic of the distortion components occurring at the amplifying section. Therefore, the distortion components having the asymmetric characteristic cannot be sufficiently suppressed. According to the first aspect, however, the asymmetric characteristic of the distortion components can be eliminated by the envelope signal. Thus, a large distortion suppressing effect can be achieved even with the use of a distortion signal which can be generated by the conventional method.
According to a second aspect based on the first aspect, the power amplifier further includes:
an envelope signal detecting section for detecting a level of the envelope signal; and
a first envelope signal adjusting section for adjusting, based on the level of the envelope signal detected by the envelope signal detecting section, an amplitude and a phase of the envelope signal to be injected to the signal amplifying route.
In the above second aspect, the amplitude and phase of the envelope signal to be injected to the signal amplifying route are adjusted in accordance with the level of the envelope signal itself. Here, the level of the envelope signal is changed in accordance with the level of the original signal. Also, the amplitude and phase of the envelope signal to be injected is changed in accordance with the level of the original signal. In view of these, the amplitude and the phase of
Fujiwara Seiji
Ishida Kaoru
Matsuyoshi Toshimitsu
Choe Henry
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Power amplifier does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power amplifier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power amplifier will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3298840