Telecommunications – Transmitter – Power control – power supply – or bias voltage supply
Reexamination Certificate
1999-07-12
2001-08-07
Maung, Nay (Department: 2681)
Telecommunications
Transmitter
Power control, power supply, or bias voltage supply
C455S091000, C455S522000, C330S149000, C375S296000, C375S297000
Reexamination Certificate
active
06272326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a distortion compensation address generator, a distortion compensating circuit, and a transmitter.
2. Description of the Related Art
In communication apparatuses such as a cellular phone, etc., as shown in FIG.
17
(
a
), a signal is radio transmitted from an antenna
503
through amplification due to an IF amplifier
501
and a transmitting amplifier
502
. As an I/O (input/output) characteristic of the transmitting amplifier
502
, it is ideal that a good linearity as shown in a dot-dash line of FIG.
17
(
b
) is ensured. However, in actual, as shown in a solid line of FIG.
17
(
b
), an amplification factor is reduced as input signal voltage increases higher because of a characteristic of a semiconductor element forming the transmitting amplifier
502
, with the result that a non-linear distortion occurs. This distortion causes deterioration of communication quality.
For this reason, in order to compensate for the non-linear distortion of the transmitting amplifier, there is provided a circuit (distortion compensating circuit)
500
for compensating for the distortion at a digital data stage as shown in FIG.
17
(
a
).
The distortion compensating circuit
500
compensates for transmitting data using compensation data having a characteristic opposite to the actual I/O characteristic of the transmitting amplifier (characteristic shown in the solid line of FIG.
17
(
b
)), so that the linearity of transmitting amplifier
502
is improved.
Since the value of transmitting data varies instantaneously in real time, the compensation of the non-linear distortion of the transmitting amplifier must be performed to follow the variation at high speed.
Also, in mobile communication, transmission power control is carried out for the purpose of reducing co-channel interference and power consumption of the mobile apparatus. If a gain of the transmitting amplifier is adjusted by the transmission power control, the compensation for the non-linear distortion must be carried out to follow the adjustment appropriately.
In FIG.
17
(
a
), the reason why a transmission power control signal is input to not only the transmitting amplifier
502
but also the compensating circuit
500
is that the distortion compensation must be carried out in accordance with transmission power.
As a useful system, which realizes a high speed distortion compensation, there is a system in which distortion compensation data is stored in a memory and an memory address is generated at high speed by address tables and distortion compensation data is output from the memory, that is, a memory access system using the address tables.
However, in the memory access system using the address tables, numerous comparators, which are operated in parallel, are required, and these comparators must be operated at high speed to follow the change in transmitting data, with the result that there is difficulty in downsizing the communication apparatus and obtaining low power consumption.
Also, for compensating for the non-linear distortion of the transmitting amplifier in mobile communication, particularly a cellular phone, transmission power of the transmitting amplifier varies over several tens of gradations (levels) by transmission power control. Therefore, the number of address generation tables corresponding to the number of gradations must be prepared. Moreover, in order to perform high-speed distortion compensation, it is necessary to operate the plurality of address generation tables. Therefore, in view of this point, there is difficulty in downsizing the communication apparatus and obtaining low power consumption.
The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to realize miniaturization of the circuit and low power consumption as ensuring high-speed distortion compensation of the transmitting amplifier.
SUMMARY OF THE INVENTION
A distortion compensation address generator of the present invention in one preferred mode includes a plurality of comparators each for comparing a transmission power value with a respective predetermined reference value, a decoder for decoding an output of each of the plurality of comparators, and comparator control means for turning off a part of the plurality of comparators being not used in generation of the address, corresponding to a level of the transmission power value.
In accordance with the level of the transmission power value, only a part of numerous comparators built in an address generation table is operated and the other comparators are turned off, so that power consumption in the circuit can be restrained.
Also, according to one preferred mode of the present invention, comparator control means compares the transmission power value with an operation area coefficient prepared in advance so as to generate a control signal for turning off the part of the comparators.
The comparison between the coefficient (operation area coefficient) prepared in advance and the transmission power value makes it possible to determine a comparator to be turned off in real time.
According to the other preferred mode of the present invention, the distortion compensation address generator of the present invention further comprises transmission power calculation means for calculating the transmission power value based on transmitting data.
This makes it possible to calculate a necessary transmission power value instantaneously.
Moreover, according to the other preferred mode of the present invention, transmission power calculation means combines a plurality of transmitting signals to calculate transmission power.
Since transmission power can be calculated by combining the plurality of signals, the address generator of the present invention can be used in not only a mobile apparatus for a cellular phone but also a base station apparatus.
According to the other preferred mode of the present invention, there is provided a distortion compensation address generator includes,
an address generation table having a plurality of comparators each for comparing a transmission power value with a respective predetermined reference value, a decoder for decoding an output of each of the plurality of comparators, and comparator control means for turning off a part of the plurality of comparators being not used in generation of the address in accordance with a level of the transmission power value,
an address calculator for providing a predetermined calculation to the transmission power value so as to generate the address, and
a switching circuit for comparing the transmission power value with a predetermined threshold value to turn on either the address generation table or the address calculator, corresponding to a comparison result. Since the number of comparators are increased as the transmission power value is increased, current consumption in the address generation table is increased when the transmission power value becomes great. On the other hand, in an address calculator for generating an address in real time after executing a predetermined calculation, operating current is substantially determined by an amount of hardware. For this reason, current consumption is substantially constant regardless of the transmission power value. Therefore, both are complementarily combined and used under a predetermined condition, thereby making it possible to restrain an amount of current consumption in the entire address generator most effectively.
Also, according to the other preferred mode of the present invention, the switching circuit turns on the address generation table when the transmission power is lower than a threshold value and turns on the address calculator when the transmission power is higher than the threshold value.
In an address generation table with a comparator-off function, as the input power value is smaller, the effect of reduction in current consumption is brought to the fore. For this reason, the address generation table is used in an area where the in
Greenblum & Bernstein P.L.C.
Matsushita Electric - Industrial Co., Ltd.
Maung Nay
Trinh Sonny
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