Digital demodulation circuit using automatic gain control circuit having temperature compensation function

摘要

A digital demodulation circuit amplifies a received signal of an intermediate frequency with a variable gain control amplifier so as to convert it into a baseband signal, which is separated into a common-mode component and an orthogonal component. A first gain control voltage is generated based on the common-mode component and the orthogonal component. Additionally, a temperature correction value is generated by smoothing a pulse-width modulation signal, having a pulse width corresponding to ambient temperature, and by adding a predetermined gain and an offset thereto. A second gain control voltage is generated by adding the temperature correction value to the first gain control voltage. The variable gain control amplifier amplifies a received signal with the second gain control voltage. Thus, it is possible to achieve a temperature compensation function and an automatic gain control function in the digital demodulation circuit with a simple circuit configuration.

主权项

1. A digital demodulation circuit comprising:
a variable gain control amplifier which amplifies a received signal of an intermediate frequency; an orthogonal demodulator which converts the received signal, amplified by the variable gain control amplifier, into a baseband signal so as to separate it into a common-mode component and an orthogonal component; an A/D converter which converts the common-mode component and the orthogonal component of the baseband signal into digital signals; a gain control circuit which generates a first gain control voltage based on the digital signals; a temperature compensation circuit which generates and smoothes a pulse-width modulation signal, having a pulse width corresponding to ambient temperature, so as to add a predetermined gain and an offset, compensating for variations in ambient temperature, thereto, thus generating a temperature correction value; and an adder which adds the temperature correction value to the first gain control voltage so as to generate a second gain control voltage, wherein the variable gain control amplifier amplifies the received signal with a gain corresponding to the second gain control voltage.