Amplifiers – With plural amplifier channels – Redundant amplifier circuits
Reexamination Certificate
2000-01-31
2001-05-29
Pascal, Robert (Department: 2817)
Amplifiers
With plural amplifier channels
Redundant amplifier circuits
C330S286000
Reexamination Certificate
active
06239656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power amplifier, and a microwave power amplifier with a non-linear distortion compensation function in particular.;
2. Description of the Related Art
In line with development of increasingly smaller and lighter cellular telephones in recent years, an IC supply voltage has been reduced and increasingly lower power consumption is required. As an IC supply voltage decreases, transistors composing a power amplifier become saturated more easily. Thus, the amount of noise superimposed over an amplified output signal tends to increase.
However, in order to meet stringent requirements from users, optimal communications using cellular telephones must be secured even in a low power consumption environment.
In securing the communication quality, it is important to compensate non-linear distortion of a microwave power amplifier. An example of non-linear distortion compensation circuit of a power amplifier is described in the Japanese Patent Application No.HEI 6-37551.
Suppressing non-linear distortion of the microwave power amplifier requires extraction of a distortion component signal in the first place. Then, the phase of the extracted distortion component signal is inverted. The inverted signal is superimposed over the original signal to cancel out the distortion component.
However, separating only the distortion component from the output signal of the power amplifier requires a dedicated distortion extraction circuit, which will require more circuit parts. This may increase the cost of the apparatus.
This also requires prior fine adjustment of added circuit parts. Such adjustment is troublesome.
SUMMARY OF THE INVENTION
It is an objective of the present invention to reduce distortion of a microwave power amplifier while suppressing an increase in the number of parts of the circuit and avoiding trouble of prior adjustment of the circuit.
The present invention uses a balanced amplifier comprising a hybrid power divider and hybrid power combiner for power amplification. The present invention actively uses one port (terminal) of the hybrid power combiner, which would normally be terminated, as a distortion detection port (terminal).
That is, output ports other than the output ports for normal signals in the balanced amplifier circuit would conventionally be terminated with terminal resistors connected. However, these ports have the feature that a distortion component generated in the amplifier is outputted to these ports without being suppressed so much as a normal signal.
Focusing on this finding, it is possible to extract distortion by using one port of the hybrid power combiner that would conventionally be terminated as a distortion detection port without using any special circuit. Adding desired adjustment to the output of this port and feeding this output forward to the output of the power amplifier can cancel out the distortion component, thus eliminating the distortion component.
It is desirable that the distortion signal outputted from one port of the hybrid power combiner be subjected to adjustment of attenuation of the signal level, phase shift or amplitude. This will enhance the distortion elimination effects.
Mounting the power amplifier of the present invention in a mobile communication apparatus can secure a clear communication quality with less distortion.
REFERENCES:
patent: 4392252 (1983-07-01), Cluniat
patent: 4439740 (1984-03-01), Harrington
patent: 4564816 (1986-01-01), Kumar et al.
patent: 4656434 (1987-04-01), Selin
patent: 5287069 (1994-02-01), Okubo et al.
patent: 6128479 (2000-10-01), Fitzpatrick et al.
patent: 0936731A1 (1999-08-01), None
patent: 4301905 (1992-10-01), None
patent: 637551 (1994-02-01), None
European Search Report dated Jun. 30, 2000.
Rodrigo Cordeiro Tupynamba et al., “MESFET Nonlinearities Applied to Predistortion Linearizer Design”, International Microwave Symposium Digest (MTT-S), US, New York, IEEE, vol.—, 1992, pp. 955-958.
Enoki Takashi
Nagata Hideo
Choe Henry
Matsushita Electric - Industrial Co., Ltd.
Pascal Robert
Stevens Davis Miller & Mosher LLP
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