Telecommunications – Receiver or analog modulated signal frequency converter – Local control of receiver operation
Reexamination Certificate
1999-06-28
2001-09-25
Nguyen, Lee (Department: 2683)
Telecommunications
Receiver or analog modulated signal frequency converter
Local control of receiver operation
C455S232100, C455S240100, C455S245100, C455S250100, C375S345000
Reexamination Certificate
active
06295445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic gain controlling method for controlling the variable amount of the gain according to the level of the received signal using an RSSI (Receive Signal Strength Indicator) that detects the electric field intensity of the received signal so as to convert the received signal as an analog signal into a digital signal. The present invention also relates to an automatic gain controlling apparatus corresponding to the automatic gain controlling method and a communication receiving apparatus having the automatic gain controlling apparatus.
2. Description of the Related Art
A conventional receiving apparatus for use with a radio communication system performs an automatic gain controlling process corresponding to the fluctuation of the level of the received signal.
In for example a CDMA mobile communication system of which a plurality of users use the same frequency, an RSSI that detects the electric field intensity of the received signal is used to control the variable amount of a gain varying unit disposed in a receiving apparatus so as to keep the level of a signal that is supplied to an analog/digital (A/D) converting unit.
However, in the conventional radio communication receiving apparatus, as shown in
FIG. 1
, the RSSI controls the gain varying unit so that the variable amount thereof is proportional to the input level as the level of the received signal. Thus, since the variable amount of the gain varying unit is controlled corresponding to information of the preceding slot of the received signal. Consequently, when the level of the received signal largely fluctuates, the variable amount of the gain varying unit becomes excessive. As a result, the automatic gain controlling process may not properly operate corresponding to the abrupt fluctuation of the received signal for fading, shadowing and so like.
SUMMARY OF THE INVENTION
The present invention is made from the above-described point of view. An object of the present invention is to provide a gain controlling method that allows a received signal to be stable received level against the fluctuation of the level of the received signal. Another object of the present invention is to provide a gain controlling apparatus corresponding to the gain controlling method and a communication receiving apparatus having the gain controlling apparatus.
A first aspect of the present invention is an automatic gain controlling method for causing an RSSI (Receive Signal Strength Indicator) to detect the electric field intensity of a received signal supplied to a demodulating unit so as to control the variable amount of the gain of a radio frequency signal and output a signal in a predetermined level, the method comprising the steps of (a) detecting the electric field intensity of the received signal and controlling the variable amount of the gain corresponding to the detected electric field intensity, and (b) causing the demodulating unit to convert the received signal into the digital signal and controlling the variable amount of the gain so as to converge the average value of the converted digital signal at a digital signal in a predetermined amplitude level.
When the variable amount of the gain is controlled corresponding to the electric field intensity, the variable amount of the gain is almost constant in a predetermined level range of the received signal.
When the digital signal is averaged, a signal detected in each predetermined time period is converted into a digital signal within a predetermined number of bits corresponding to almost the same level.
The digital signals are averaged in a predetermined time period.
A second aspect of the present invention is an automatic gain controlling apparatus, comprising a gain varying unit for keeping a received signal in a predetermined level, an analog/digital converting unit for converting the signal kept in the predetermined level by the gain varying unit into a digital signal, an RSSI controlling portion for detecting the electric field intensity of the received signal and controlling the variable amount that causes the gain varying unit to vary the received signal in a predetermined level corresponding to the detected electric field intensity, and an averaging process circuit for averaging the level of the digital signal received from the analog/digital converting unit and controlling the variable amount that causes the gain varying unit to vary the signal in a predetermined level so as to converge the digital signal received from the analog/digital converting unit at a predetermined amplitude level.
The RSSI controlling portion has an RSSI circuit for detecting the electric field intensity of the received signal, and a level determining unit having at least one threshold value for setting a range of which the conversion amount of the gain is almost constant in a predetermined range of the electric field intensity detected by the RSSI circuit.
The averaging process circuit converts a signal detected in each predetermined time period into a digital signal within a predetermined number of bits corresponding to almost the same level and averages each of bits of the digital signals.
The averaging process circuit averages the number of bits of the digital signals in a predetermined time period.
A third aspect of the present invention is a communication receiving apparatus, comprising a radio frequency receiving portion for receiving a transmitted signal, an automatic gain controlling apparatus for converting the signal received from the radio frequency receiving portion into a digital signal, the automatic gain controlling apparatus having a gain varying unit for keeping a received signal in a predetermined level, an analog/digital converting unit for converting the signal kept in the predetermined level by the gain varying unit into a digital signal, an RSSI controlling portion for detecting the electric field intensity of the received signal and controlling the variable amount that causes the gain varying unit to vary the received signal in a predetermined level corresponding to the detected electric field intensity, and an averaging process circuit for averaging the level of the digital signal received from the analog/digital converting unit and controlling the variable amount that causes the gain varying unit to vary the signal in a predetermined level so as to converge the digital signal received from the analog/digital converting unit at a predetermined amplitude level, and a base band portion for demodulating a digital signal that has been modulated on a transmitting side and received from the automatic gain controlling apparatus to original information.
The RSSI controlling portion has an RSSI circuit for detecting the electric field intensity of the received signal, and a level determining unit having at least one threshold value for setting a range of which the conversion amount of the gain is almost constant in a predetermined range of the electric field intensity detected by the RSSI circuit.
The averaging process circuit converts a signal detected in each predetermined time period into a digital signal within a predetermined number of bits corresponding to almost the same level and averages each of bits of the digital signals.
The averaging process circuit averages the number of bits of the digital signals in a predetermined time period.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.
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patent: 6038435 (2000-03-01), Zhang
patent: 9-247113 (1997-09-01), None
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Foley & Lardner
NEC Corporation
Nguyen Lee
Nguyen Simon
LandOfFree
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