Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
A technique is described whereby digital circuitry is used for the demodulation of a radio frequency (RF) carrier for use in low cost broadband modems as used in broadband cable television networks. The circuit, as shown in the drawing, consists of buffer amplifier 10, coupling capacitor 11 and transistor gate 12. The basic concept provides a means of demodulating an analog RF signal by a digital signal at broadband carrier frequency, utilizing open collector transistor gate 12 as an effective analog demodulator. If a digital signal source 13 at frequency F0 is used to switch the gate 12 at frequency F0 and an analog signal is impressed on the output of gate 12, chopper demodulation occurs. This allows a wide dynamic range of input signals with excellent balancing being effected through the choice of coupling capacitor 11.