Amplifier apparatus

Amplifiers – Hum or noise or distortion bucking introduced into signal...

Reexamination Certificate

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C330S151000

Reexamination Certificate

active

06486734

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an amplifier apparatus suitable for use in communication terminals such as mobile phones, base stations, and RF circuits.
2. Description of the Related Art
In the mobile communications terminals such as mobile phones, base stations, and RF circuits, a signal to be transmitted is amplified by an electric power amplifier before transmitted. At that time, an intermodulation distortion component is caused in an output of the amplifier. Since this intermodulation distortion component appears as noises in the signal transmitted, a feedback-type amplifier or any ordinary type of amplifier has been used in the conventional art to remove this intermodulation distortion component.
FIG. 18
of the accompanying shows a distortion feedback-type amplifier disclosed in Japanese Patent Laid-Open Publication No. HEI 5-167356. The distortion feedback-type amplifier
100
of
FIG. 18
comprises a first dividing circuit
101
, a first phase/power level regulating circuit
102
, a first amplifier (primary amplifier)
103
, a second dividing circuit
104
, a second phase/power level regulating circuit
105
, a first combining circuit
106
, a second amplifier (auxiliary amplifier)
107
, a band-pass filter
108
a,
a third phase/power level regulating circuit
108
b,
and a second combining circuit
109
.
The first dividing circuit
101
divides an input signal from an input terminal (IN) to pick up a part of the input primary signal as an auxiliary signal for distortion detection (described later). The first phase/power level regulating circuit
102
regulates the phase and the power level of the auxiliary signal obtained by the first dividing circuit
101
.
The primary amplifier
103
amplifies the primary signal received from the first dividing circuit
101
, and the second dividing circuit
104
picks up a part of an output of the primary amplifier
103
.
The second phase/power level regulating circuit
105
regulates the phase and the power level of the signal picked up by the second dividing circuit
104
. The first combining circuit
106
combines the signal (frequency spectrum
114
) from the second phase/power level regulating circuit
105
and the auxiliary signal (frequency spectrum
115
) that has been regulated in phase/power level by the first phase/power level regulating circuit
102
to cancel a primary signal component contained in the output (frequency spectrum
113
) from the primary amplifier
103
for detecting an intermodulation distortion component (hereinafter also called “distortion component”).
For this purpose, the first phase/power level regulating circuit
102
and the second phase/power level regulating circuit
105
regulates phase rotation and attenuation of the input signal in such a way that a primary signal component
130
in the amplified signal (frequency spectrum
114
) is combined with the auxiliary signal (frequency spectrum
115
) in opposite phases at the same power level by the first combining circuit
106
.
The auxiliary amplifier
107
amplifies the distortion component (frequency spectrum
116
) obtained by the first combining circuit
106
. The third phase/power level regulating circuit
108
b
regulates the phase and power level of the output of the auxiliary amplifier
107
. The band-pass filter
108
a
removes unnecessary band components in the signal from the third phase/power level regulating circuit
108
b.
Since the phase is rotated through 360 degrees between the opposite ends of the pass band in the band-pass filter
108
a,
a phase error with respect to a feedback signal (distortion compensating signal) is apt to be increased. Particularly, the wider the band width, the phase error would increase.
The second combining circuit
109
combines the distortion compensating signal (frequency spectrum
117
) from the band-pass filter
108
a
with the primary signal (frequency spectrum
112
) from the first dividing circuit
101
(frequency spectrum
118
).
The third phase/power level regulating circuit
108
b
regulates the phase rotation and the power level of the distortion component obtained from the auxiliary amplifier
107
in such a way that the distortion component (frequency spectrum
116
) amplified by the auxiliary amplifier
107
is opposite in phase to the primary signal component
130
of the signal (frequency spectrum
118
) to be input to the primary amplifier
103
and that the distortion component
131
is canceled in the output (frequency spectrum
119
) of the primary amplifier
103
.
Namely, the second dividing circuit
104
, the second phase/power level regulating circuit
105
, the first combining circuit
106
, the auxiliary amplifier
107
, the third phase/power level regulating circuit
108
b,
and the band-pass filter
108
a
constitute a feedback loop (feedback system)
135
for an input/output system of the primary amplifier
103
.
With this construction, in the conventional distortion feedback-type amplifier
100
, the primary signal (frequency spectrum
111
) input from the input terminal (IN) is divided into the primary signal (frequency spectrum
112
) and the auxiliary signal (frequency spectrum
110
) by the first dividing circuit
101
, which auxiliary signal is then input to the first phase/power level regulating circuit
102
to be regulated in phase rotation and attenuation.
In the meantime, the primary signal (frequency spectrum
112
) is amplified by the primary amplifier
103
, at which time a distortion component
131
with respect to the primary signal component
130
is generated in the output (frequency spectrum
113
) of the primary amplifier
103
due to the nonlinear characteristic of the primary amplifier
103
.
Then a part of the output signal (frequency spectrum
113
) of the primary amplifier
103
is picked up by the second dividing circuit
104
and is regulated in phase and power level by the second phase/power level regulating circuit
105
.
The auxiliary signal (frequency spectrum
115
) having passed the first phase/power level regulating circuit
102
is combined with the primary signal (frequency spectrum
114
) in opposite phase at the same power level by the first combining circuit
106
to cancel the primary signal component
130
, thereby extracting only the distortion component
131
(frequency spectrum
116
).
The thus extracted distortion component
131
is amplified by the auxiliary amplifier
107
and is then regulated in phase rotation and attenuation by the third phase/power level regulating circuit
108
b.
After that, unnecessary band components other than the desired band, which are caused such as by oscillation in the feedback loop
135
, are stopped by the band-pass filter
108
a
so that only the desired band component is output to the second combining circuit
109
as the distortion compensating signal (frequency spectrum
117
).
The second combining circuit
109
thereby combines the distortion compensating signal (frequency spectrum
117
) with the primary signal (frequency spectrum
112
) to output the combined signal (frequency spectrum
118
) to the primary amplifier
103
.
As the result, the effect of the non-linear characteristic of the primary amplifier
103
is canceled in the signal(frequency spectrum
118
) input to the primary amplifier
103
. The resultant signal (frequency spectrum
119
) whose intermodulation distortion component
131
is restrained is thus output from the primary amplifier
103
via the second dividing circuit
104
, whereupon this signal is output from the output terminal (OUT) as the output of the distortion feedback-type amplifier
100
.
Assuming that a transfer function of the distortion feedback-type amplifier
100
of
FIG. 18
is obtained using an equivalent circuit of
FIG. 19
, the output e
o
of the distortion feedback-type amplifier
100
is given by
e
o
=A·e
io
+D
  (1)
where e
i
is the primary signal to be input from the input terminal, D is the intermodulation distortion component to be added to the output of the primary am

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