RADIO RECEIVER BECOMES ACCOMPLISHED THE GAIN CONTROL BY THE LOW PASS FILTER

摘要

A radio receiver for performing gain control by a low pass filter is provided to configure an LPF as a gm-C(transconductance-capacitor) filter by using OTA(Over The Air), perform gain tuning through the control of a first bias voltage applied to the LPF, and perform frequency tuning through the control of a second bias voltage, thereby simplifying the configuration of the radio receiver without a separate variable gain controller. A radio receiver includes a receiver(100) and an AGCL(Automation Gain Control Loop)(200). The receiver receives amplifies a RF(Radio Frequency) signal, and converts the amplified RF signal into a basebase signal. The AGCL controls the gain of the baseband signal converted through the receiver. The AGCL includes a first LPF(Low Pass Filter)(210), a second LPF(220), an RSSI(Received Signal Strength Indicator)(260), an MCU(Micro Control Unit)(250), first and second voltage-current converters(270,280), and a current-voltage converter(290). The first LPF has a first bias voltage terminal and a second bias voltage terminal, and tunes the frequency of a signal outputted through the receiver by the control of a bias voltage inputted to the second bias voltage terminal. The second LPF is connected to the output terminal of the first LPF, has a first bias voltage terminal and a second bias voltage terminal, and performs frequency tuning and gain tuning by the control of the bias voltage inputted through the first bias voltage terminal and the second bias voltage terminal. The RSSI detects the voltage level of a signal outputted from the first LPF and outputs a voltage varied linearly according to an input voltage. The MCU receives the output signal of the RSSI and outputs a reference voltage and a second bias voltage. The first and second voltage-current converters are connected to each of the output terminal of the RSSI and the output terminal of the MCU to convert output voltages into currents separately and output the converted currents. The current-voltage converter converts the sum of currents outputted from the first and second voltage-current converters into voltages and applies a bias voltage to the first bias voltage terminal of the second LPF.