Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation
Reexamination Certificate
2000-07-05
2003-06-10
Appiah, Charles N. (Department: 2745)
Telecommunications
Receiver or analog modulated signal frequency converter
Local control of receiver operation
C455S232100, C330S279000, C375S345000
Reexamination Certificate
active
06577852
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to an automatic gain control (will also be referred to as an “AGC” hereinafter) for gain controlling an input signal whose signal level is varied in a signal reception system of a mobile communication apparatus in such a manner that the level of the input signal is made constant by a feedback loop. More specifically, the present invention is directed to an automatic gain control device and an automatic gain control method, capable of switching an operation of a circuit employed in a control system in response to a condition of an automatic gain control operation, and also is directed to a radio communication apparatus having such an automatic gain control operation.
Conventionally, in various sorts of signal processing apparatuses, for example, radio communication apparatus, strengths of electromagnetic wave reception electric fields are varied by wave attenuate ions in electromagnetic wave propagation paths, so that signal levels of reception signals to be processed are varied. As a result, automatic gain control (AGC) operations are carried out in order to reduce demodulation errors, while making the variation of this reception signal constant. For instance, in portable telephones operated in the CDMA system, PDCs (personal digital cellular) of the TDMA system, and PHSs (personal handy-phone system) in the TDMA/TDD system, a strength of a signal reception electric field is detected from a reception signal, a gain of a variable gain amplifier is automatically controlled in response to this detection signal so as to make a constant level of an output signal. As such an automatic gain control manner, an open-loop control system and a closed-loop control system are known in this field. In the open-loop control system, a gain of a variable amplifier provided at a post stage is controlled in response to a control signal. This control signal is generated by detecting a level variation of an input signal. In the closed-loop control system, a gain of a variable gain amplifier provided at a prestage is controlled in response to this control signal.
In radio communication apparatus for executing such an automatic gain control, reductions of power consumption are required. More specifically, in the case of portable telephones, since rechargeable batteries are employed as power sources thereof, reductions of power consumed in these portable telephones are strongly required in order to prolong, or extend operable time of these portable telephones. Japanese Patent Application No. Hei-9-324111 filed by the Applicant in 1997 describes the radio base station apparatus capable of achieving the low power consumption in the system requiring the AGC circuit.
In the conventional signal processing apparatuses, even under such a condition that an automatic gain control becomes stable, for instance, even under such a stable reception condition that a strength of a reception electric field becomes constant (namely, non-move state in the case of portable telephone), this automatic gain control operation is continuously carried out. This execution may constitute one of factors as to why power consumption is increased. As a result, there is a problem that the power consumption cannot be reduced in the apparatus which requires the automatic gain control operation, and thus, the requirement for the long time operation of this signal processing apparatus can be hardly satisfied.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-explained problem, and therefore, has an object to provide an automatic gain control device, an automatic gain control method, and a radio communication apparatus having the automatic gain control function, capable of reducing power consumption while executing an automatic gain control operation, and capable of being driven for a long time period.
An automatic gain control device according to first aspect of the present invention, is an automatic gain control device in which an input signal is variable-amplified by variable gain amplifying means to obtain a predetermined output signal, the automatic gain control device comprises: control signal generating means for generating a variable gain control signal in response to an output signal level of the variable gain amplifying means; control signal holding means for holding the variable gain control signal; and operation control means for bringing at least a portion of circuits of the relevant automatic gain control system into a non-operative condition in such a case that a condition detecting level based upon the input signal is not changed for a predetermined time period, and for sending out the variable gain control signal held by the control signal holding means to the variable gain amplifying means under the non-operative condition.
An automatic gain control device, according to second aspect of the present invention, is an automatic gain control device in which an input signal is variable-amplified by variable gain amplifying means to obtain a predetermined output signal, the automatic gain control device comprises: control signal generating means for generating a variable gain control signal in response to an output signal level of the variable gain amplifying means; control signal holding means for holding the variable gain control signal; condition detecting level holding means for holding a condition detecting level in response to the input signal; condition detecting level difference calculating means for calculating a difference between a preceding condition detecting level and a present condition detecting level, which are held by the condition detecting level holding means; and operation control means for bringing at least a portion of circuits of the relevant automatic gain control system into a non-operative condition in the case that the difference of the condition detecting level is equal to zero, and for sending out the variable gain control signal held by said control signal holding means to the variable gain amplifying means under the non-operative condition; and also for releasing the non-operative condition of the circuit of the automatic gain control system when the difference of the condition detecting level is not equal to zero.
Also, according to third aspect of the invention, the operation control means uses the level of the variable gain control signal as the condition detecting level based upon the input signal; and when the level of the variable gain control signal is not changed for a predetermined time period, the operation control means brings at least a portion of the circuits of the relevant automatic gain control system to the non-operation condition.
Alternatively, according to fourth aspect, the automatic gain control device is further comprised of detecting means for detecting the output signal to obtain a detection-signal; and the operation control means uses the level of the detection signal as the condition detecting level based upon the input signal; and when the level of the detection signal is not changed for a predetermined time period, the operation control means brings at least a portion of the circuits of the relevant automatic gain control system to the non-operation condition.
Alternatively, according to fifth aspect, the automatic gain control device is further comprised of reception electric field strength detecting means for detecting a reception electric field strength of an input signal based upon the out signal; and the operation control means uses the reception electric field strength as the condition detecting level based upon the input signal; and when the reception electric field strength is not changed for a predetermined time period, the operation control means brings at least a portion of the circuits of the relevant automatic gain control system to the non-operation condition.
Alternatively, according to sixth aspect, the automatic gain control device is further comprised of fading pitch detecting means for detecting a fading pitch of an input signal based upon the output
Ichikawa Yasufumi
Iwata Yasushi
Appiah Charles N.
Matsushita Electric - Industrial Co., Ltd.
Pearne & Gordon LLP
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