Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation
Reexamination Certificate
2001-02-16
2004-03-16
Trinh, Sonny (Department: 2685)
Telecommunications
Receiver or analog modulated signal frequency converter
Local control of receiver operation
C455S232100, C455S245100, C455S126000, C330S279000
Reexamination Certificate
active
06708025
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an automatic gain controller and an automatic gain control method for outputting the input signal, whose level varies, in a manner that the input signal is made constant via feedback loop, and radio communications apparatus having the automatic gain control function.
The automatic gain control, typically abbreviated as AGC, has been implemented in a variety of signal processors. For example, in radio communications, the signal level of a received signal varies due to fading in a radio propagation path. Thus the receiving system of radio communications apparatus is equipped with an automatic gain control function in order to make constant the level of the received signal and to reduce demodulation errors.
In automatic gain control, it is desired that pull-in operation can be made in an early stage after power-on. For example, some of the radio communications apparatus that uses a battery as a power supply performs intermittent reception in order to prolong service life of the battery. In such radio communications apparatus, power-on/off is frequently repeated so that the request for reduction of the initial pull-in time is earnest.
As a technology for reducing the initial pull-in time, the “high-speed AGC circuit” is described in the Japanese Patent Publication No. H11-88083. The “high-speed AGC circuit” according to this conventional example maintains the AGC operation point by controlling the gain control signal of the amplifier via a pulse signal having an arbitrary pulse width at power-on, thus reducing the initial pull-in time.
However, for an aforementioned conventional automatic gain controller, a complicated control was required to reduce the initial pull-in time at power-on. Such a control was only realized by most of the related feature in a hardware configuration. This presented a problem of expansion of the circuit scale.
SUMMARY OF THE INVENTION
The invention, in view of the aforementioned circumstances, aims at providing an automatic gain controller and an automatic gain control method for reducing the initial pull-in time at power-on, and radio communications apparatus having the automatic gain control function.
An automatic gain controller according to the invention is characterized in that the automatic gain controller comprises variable gain amplifying means for variably amplifying an input signal based on a gain control signal to output a signal of a predetermined level, gain control signal generating means for generating an automatic gain control signal based on the difference between the level of the output signal of the variable gain amplifying means and a target value, sweep signal output means for outputting a sweep signal used for scanning across the minimum value and the maximum value of the variable gain range of the variable gain amplifying means, gain voltage value detecting means for detecting the control voltage value of the sweep signal obtained when the level of the output signal has coincided with the target value, and gain control signal supplying means for supplying the sweep signal as a gain control signal to be supplied to the variable gain amplifying means in the initial stage of operation, supplying the control voltage value obtained when the level of the output signal has coincided with the target value after the sweep operation via the sweep signal, and supplying the automatic gain control signal that is based on the difference after output of the control voltage value.
Preferably, the gain control signal supplying means assumes completion of the sweep operation when the sweep signal has traversed across one and the other of the minimum value and the maximum value in the variable gain range, and outputs the control voltage value as the gain control signal on completion of the sweep operation. Or, the gain control signal supplying means stops the sweep operation when the level of the output signal has coincided with the target value, and outputs the control voltage value as the gain control signal on stoppage of the sweep operation.
Preferably, the automatic gain controller comprises start operation control means for determining that the control voltage value of the sweep signal obtained when the level of the output signal has coincided with the target value has fallen within a predetermined control value range of the variable gain range of the variable gain amplifying means, and supplying the median of the control value range as the gain control signal to the variable gain amplifying means at the start of the next operation when the control voltage value has fallen within this control value range a predetermined number of times in succession.
Preferably, the automatic gain controller comprises sweep control means for determining that the control voltage value of the sweep signal obtained when the level of the output signal has coincided with the target value has been biased to one side of the variable gain range of the variable gain amplifying means, and performing sweep operation in the direction opposite to the sweep direction of the sweep signal at the start of the next operation when the control voltage value has fallen within this biased control value range a predetermined number of times in succession.
An automatic gain control method according to the invention is an automatic gain control method for variably amplifying an input signal based on a gain control signal via the variable gain amplifying means to output a signal of a predetermined level, characterized in that the automatic gain control method comprises a sweep signal supplying step for supplying a sweep signal that scans across the minimum value and the maximum value of the variable gain range of the variable gain amplifying means in the initial stage of operation, a control voltage value supplying step for detecting the control voltage value of the sweep signal obtained when the level of the output signal of the variable gain amplifying means has coincided with the target value and supplying the control voltage value after the sweep operation via the sweep signal, and an automatic gain control signal supplying step for generating an automatic gain control signal based on the difference between the level of the output signal of the variable gain amplifying means and a target value and supplying the automatic gain control signal after output of the control voltage value.
Preferably, the sweep signal supplying step assumes completion of the sweep operation when the sweep signal has traversed across one and the other of the minimum value and the maximum value in the variable gain range, and outputs the control voltage value as the control voltage value supplying step. Or, the sweep signal supplying step stops the sweep operation when the level of the output signal has coincided with the target value, and supplies the control voltage value as the control voltage value supplying step on stoppage of the sweep operation.
Preferably, the automatic gain control method comprises a start operation control step for determining that the control voltage value of the sweep signal obtained when the level of the output signal has coincided with the target value has fallen within a predetermined control value range of the variable gain range of the variable gain amplifying means, and supplying the median of the control value range as the gain control signal to the variable gain amplifying means at the start of the next operation when the control voltage value has fallen within this control value range a predetermined number of times in succession.
Preferably, the automatic gain control method comprises a sweep control step for determining that the control voltage value of the sweep signal obtained when the level of the output signal has coincided with the target value has been biased to one side of the variable gain range of the variable gain amplifying means, and performing sweep operation in the direction opposite to the sweep direction of the sweep signal at the start of the next operation when the control voltage value has
Ichikawa Yasufumi
Iwata Yasushi
Pearne & Gordon LLP
Trinh Sonny
LandOfFree
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