Patent ID: 8315585

Claim:
Method for a fast reduction in voltage of a DC component and low-frequency components at the output of a mixing circuit (MC) in a receiver of a UHF transceiver within a time interval (T) beginning at an end of transceiver transmission and being defined by the communication protocol, characterized in that a current from a controlled current source (CCS), which is controlled by a control voltage (cv), is subtracted from an output current signal (mos) of the mixing circuit (MC), that a current resulting from said subtraction is conducted to an input of an operational amplifier (A) and said current is there cancelled by an equal current in the opposite direction, which current flows from an output of the operational amplifier (A) through a resistor (FBR) in a return path back to its input, that those components of a voltage signal (ols) from the output of the operational amplifier (A) are amplified, whose frequency lies first below the higher and later below the lower multiple of the lower frequency limit of a modulation signal in a received signal (rs) and finally lies below the lower frequency limit of the modulation signal in the received signal (rs), that said control voltage (cv) is generated in that said amplified DC component and low-frequency components of the voltage signal (ols) act on a control terminal of the controlled current source (CCS) through a variable-gain amplifier (VGA) and an adjustable resistor (AR) and that after expiration of said time interval (T) when the voltage of said voltage signal (osl) at the output of the operational amplifier (A), in which signal the voltage of said DC component and those low-frequency components has been reduced by then, whose frequency is below the low frequency limit of the modulation signal in the received signal (rs), should be in a first voltage window between a low voltage limit (lvl) and a high voltage limit (hvl), an output signal (os) having the reduced voltage of said DC component and low-frequency components is generated in that said voltage signal (ols) from the output of the operational amplifier (A) is filtered by a band-pass filter, which passes components in the frequency band of said modulation signal, and is amplified.