Amplifiers – With semiconductor amplifying device – Including gain control means
Reexamination Certificate
2000-12-28
2002-12-17
Nguyen, Patricia (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including gain control means
C330S302000, C333S08100R
Reexamination Certificate
active
06496072
ABSTRACT:
PRIORITY
This application claims priority to an application entitled “Amplifying Apparatus for a Mobile Station Receiver and Method for Controlling the Same” filed in the Korean Industrial Property Office on Dec. 29, 1999 and assigned Serial No. 99-65240, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a mobile station, and in particular, to an amplifying apparatus for securing a good impedance match of a mobile station receiver and a method for controlling the same.
2. Description of the Related Art
FIG. 1
is a circuit diagram illustrating a conventional amplifying apparatus.
Referring to
FIG. 1
, a CDMA (Code Division Multiple Access) mobile station receives a radio signal through an antenna
110
and provides the received signal to a receiver through a duplexer
109
. In the receiver, the received signal is provided to a low-noise amplifier (LNA)
108
through capacitors
107
and
108
. The low-noise amplifier
108
amplifies the received signal and provides the amplified signal to a controller (not shown). When the signal output from the low-noise amplifier
108
is higher than or equal to a predetermined level, the controller generates a control voltage Vcont of a first level (e.g., 3V) to attenuate (or decrease) the level of the received signal.
The control voltage Vcont generated by the controller is provided to a base of a bipolar junction transistor (BJT)
111
. The BJT
111
is turned ON in response to the control voltage Vcont at the first level. Then, the power supply voltage VCC is provided to a diode
101
in the receiver through resistors
102
and
103
. As a result, the diode
101
becomes conductive (or is turned ON), so that the received signal being provided from the duplexer
109
to the receiver is attenuated by the circuit comprised of the resistor
102
, the capacitor
105
and the resistor
103
.
However, as the diode
101
is turned ON, an impedance of the amplifying apparatus is decreased as compared with the case where the diode
101
is turned OFF. As a result, the impedance of the amplifying apparatus is not matched with an output impedance of the low-noise amplifier
108
. Hence, the filtering characteristics of a filter in the receiver is degraded due to the signal output from the low-noise amplifier
108
. Further, because of the impedance mismatch, abnormal oscillation occurs and the output signal includes ripple components, so that the demodulated signal may have errors.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide an amplifying apparatus for securing a good impedance match of a mobile station receiver and a method for controlling the same.
It is another object of the present invention to provide an amplifying apparatus for removing ripple components from the output signal.
To achieve the above and other objects, there is provided an amplifying apparatus for a mobile station receiver. In the amplifying apparatus, a low-noise amplifier amplifies a received signal to a preset level. A controller detects a level of a signal corresponding to a first frame of the received signal output from the low-noise amplifier, and generates a control voltage according to the detected level. An attenuation determining resistor determines an attenuation of the received signal. A first switching element is connected in series to the attenuation determining resistor, and is turned ON according to the control voltage so as to attenuate the received signal through the attenuation determining resistor. An impedance compensation resistor is connected in parallel to the attenuation determining resistor, and compensates for a decrease in an impedance due to turn-ON of the first switching element.
Further, a second switching element is connected in parallel to the impedance compensation resistor and the first switching element. The second switching element is turned ON according to the control voltage so as to provide the received signal to the low-noise amplifier without attenuation.
Preferably, the control voltage is at a first level when the level of the signal corresponding to the first frame of the received signal output through the low-noise amplifier is higher than or equal to a threshold level. The control voltage is at a second level when the level of the signal corresponding to the first frame is lower than the threshold level.
Preferably, when the control voltage is at the first level, the first switching element is turned ON and the second switching element is turned OFF. When the control voltage is at the second level, the first switching element is turned OFF and the second switching element is turned ON.
REFERENCES:
patent: 4684881 (1987-08-01), Diller et al.
patent: 5351030 (1994-09-01), Kobayashi et al.
patent: 5877612 (1999-03-01), Straw
Cho Seung-Ki
Jeong Yong-Seong
Lee Jae-Min
Lee Woo-Yong
Yang Sang-Yong
Dilworth & Barrese LLP
Nguyen Patricia
Samsung Electronics Co,. Ltd.
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