Amplifiers – With semiconductor amplifying device – Including temperature compensation means
Reexamination Certificate
1999-09-13
2001-05-08
Mottola, Steven J. (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including temperature compensation means
C330S134000
Reexamination Certificate
active
06229397
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an automatic gain control circuit, a receiving apparatus incorporating the circuit, an automatic gain control method for the receiving apparatus and a recording medium on which a program for causing the automatic gain control method to be executed. More particularly, the present invention relates to an automatic gain control circuit arranged to commonly use an automatic gain control loop to reduce the size of the circuit so as to prevent enlargement of the mounting area of a circuit substrate and power consumption in the circuit and a receiving apparatus incorporating the circuit. More particularly, the present invention relates to an automatic gain control method for a receiving apparatus with which elongation of time required to complete a process and enlargement of power consumption can be prevented when a software program is used to automatically control gains of a plurality of receiving systems and a recording medium.
As a conventional automatic gain control circuit for a receiving apparatus, an automatic gain control circuit having a structure, for example, as shown in
FIG. 10
, is known. Referring to
FIG. 10
, the conventional automatic gain control circuit comprises a variable gain amplifier
11
, a demodulating portion
12
, an A/D converter
13
, a level detector
14
, an averaging portion
21
, an adder
22
for calculating difference in a converged value, a multiplier
23
for controlling a loop gain, an adder
24
of an integration circuit, a latch circuit
25
of the integration circuit, a calculating portion
26
and a D/A converter
27
.
In the foregoing conventional automatic gain control circuit, when received signal Ri has been input, the received signal Ri is amplified by the variable gain amplifier
11
, and then demodulated by the demodulating portion
12
. Then, the received signal Ri is converted into a digital value by the A/D converter
13
so as to be demodulated output Rd. The level of a portion of the demodulated output Rd is detected by the level detector
14
, and then fetched by an automatic gain control loop.
Data subjected to the level detection is averaged for a predetermined time by the averaging portion
21
. Then, convergence to the input of the A/D converter
13
is realized by calculating the difference from a predetermined target level A by the adder
22
for calculating difference in a converged value. Then, the multiplier
23
for controlling a loop gain multiplies loop gain control value B in the automatic gain control circuit. The output of the multiplier
23
is, as change from preceding data, input to the integration circuit composed of the adder
24
and the latch circuit
25
. Thus, integrated data is latched in the latch circuit
25
at the timing of the latch timing control value D. Integrated data of the integration circuit is converted into data corresponding to a control voltage for the variable gain amplifier
11
by the calculating portion
26
. The D/A converter
27
converts data into an analog voltage so as to be fed back as the control voltage for the variable gain amplifier
11
.
Hitherto, when the gains of a plurality of receiving systems are automatically controlled by using the automatic gain control circuit structured as shown in
FIG. 10
, the automatic gain control loops must be formed by the number which is the same as the number of the receiving systems. That is, when one automatic gain control loop shown in
FIG. 10
is used to control a plurality of receiving system, for example, two receiving systems, the automatic gain control circuit shown in
FIG. 10
is provided for each of the receiving systems, as shown in FIG.
11
.
As described above, the conventional automatic gain control circuit and the receiving apparatus incorporating the circuit above are used to automatically control the gains of n (n is a positive integer not smaller than two) receiving systems. When the automatic gain control loop is structured by hardware, that is, constituted by electronic elements, the size of the automatic gain control loop block is enlarged to n times the size required when one receiving system is controlled. Thus, there arises a problem in that the mounting area of the circuit substrate is enlarged or the power consumption in the circuit is enlarged.
When a DSP (Digital Signal Processor) is employed in the automatic gain control loop to use a software program to automatically control the gains of n receiving systems, there also arises a problem in that time required to complete the automatic gain control process is elongated and, therefore, power consumption is enlarged.
SUMMARY OF THE INVENTION
To overcome the foregoing problems, an object of the present invention is to provide an automatic gain control circuit incorporating a plurality of variable gain amplifiers for controlling the amplitudes of a plurality of received signals in response to control signals and arranged to commonly use an automatic gain control loop to reduce the size of the circuit so as to prevent enlargement of the mounting area of a circuit substrate and power consumption in the circuit and a receiving apparatus incorporating the circuit.
Another object of the present invention is to provide an automatic gain control circuit which is capable of preventing elongation of time required to complete a process and enlargement of power consumption if the DSP (Digital Signal Processor) is employed in an automatic gain control loop and a software program is used to automatically control gains of a plurality of receiving systems and a recording medium.
To solve the foregoing problems, an automatic gain control circuit of the present invention and incorporating n variable gain amplifiers for controlling the amplitudes of n (n is a positive integer not smaller than two) received signals in response to control signals, the automatic gain control circuit comprising: control-signal generating means for detecting the level of one of n received signals to generate a feedback signal so as to employ the feedback signal as a control signal for one of the n variable gain amplifiers; and first correction means for subjecting the control signal for the one variable gain amplifier generated by the control-signal generating means to correction of dispersion of temperature characteristics of the other variable gain amplifiers so as to employ the corrected signals as control signals for the other variable gain amplifiers.
Preferably, in the automatic gain control circuit, the first correction means is a thermistor for performing temperature compensation.
An automatic gain control circuit according to another aspect of the invention, comprises n variable gain amplifiers each of which controls the amplitudes of n (n is a positive integer not smaller than two) received signals in response to a control signal, the automatic gain control circuit comprising: control-signal generating means for detecting the level of one of n received signals to generate a feedback signal so as to employ the feedback signal as a control signal for one of n variable gain amplifiers; and second correction means for subjecting the control signal for the one variable gain amplifier generated by the control-signal generating means to correction of dispersion of temperature characteristics and frequency characteristics of the other variable gain amplifiers so as to employ the corrected signals as control signals for the other variable gain amplifiers.
Preferably, in the automatic gain control circuit, the second correction means is adding means for adding a predetermined correction value to the control signal of the one variable gain amplifier.
Additionally, in the automatic gain control circuit, the control-signal generating means comprises n level detection means for detecting the levels of n received signals; comparison means for comparing the detected levels of the n received signals; and selection means for selecting an output of a level detection means having a highest detected level in accordance with a result of a comparison mad
Matsushita Electric - Industrial Co., Ltd.
Mottola Steven J.
Pearne & Gordon
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