US 2011/0034143 A1Published application

Method and circuit for a fast reduction in voltage of a dc component and low-frequency components at a mixing circuit output in a receiver of a uhf transceiver

OwnerVinko Kunc, Anton Stern +2inventors

InventorsVinko Kunc, Anton Stern, Andrej Vodopivec, Maja Atanasijevic-Kunc

Life of this patent

Estimating the term…

Loading patent…

Abstract

A difference between an output current signal (mos) of the mixing circuit (MC) and a current from a controlled current source (CCS) is conducted to an input of an operational amplifier (A). A control voltage (cv) for said current source is a voltage at the output of the operational amplifier (A) being filtered by a low-pass filter, whose limiting frequency equals a low frequency limit of the modulation signal in the received signal (rs). The method is speeded up in that the limiting frequency of the low-pass filter is increased by two to three orders of magnitude at the beginning and is gradually lowered to said value. A rather short time duration of the transient process is achieved so that the working point with a low voltage of the DC component and low-frequency components is set at least five times faster than so far.

Claims16

Dependent claims

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 (o1s) 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 (o1s) 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 (os1) 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 (o1s) 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.

12 more elements

Circuit 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 the end of transceiver transmission and being defined by the communication protocol, characterized in

that an output current signal (mos) of the mixing circuit (MC) is conducted to an input of an operational amplifier (A), whose output terminal is connected through a resistor (FBR) in a return path to an input terminal of the operational amplifier (A),
that a current from a controlled current source (CCS) is subtracted from an output current signal (mos) of the mixing circuit (MC),
that the output terminal of the operational amplifier (A) is connected through a variable-gain amplifier (VGA) and an adjustable resistor (AR)
on the one hand to a control terminal of the controlled current source (CCS) and
on the other hand to a terminal of a supply source through a capacitor (EC) outside the integrated circuit,
that a control circuit (CC), to whose inputs
a voltage signal (o1s) from the output of the operational amplifier (A),
an output signal (os) having a reduced voltage of said DC component and low-frequency components,
a start signal (ss), which triggers a setting of the adjustable resistor (AR),
a hold signal (hs), which freezes a value of said control voltage (cv) for controlling the controlled current source (CCS) whenever the UHF transceiver finished receiving and starts transmitting, and
a signal (mfbs) carrying data on a frequency band of the modulation signal in a received signal (rs), are conducted,
generates a control signal (cs) out of said signals, by means of which control signal (cs) a resistance of the adjustable resistor (AR) is set in such manner that an upper frequency limit of current components generated by the controlled current source (CCS) is determined in connection with the external capacitor (EC) as a low frequency limit of the modulation signal in the received signal (rs) or as a multiple of said low frequency limit,
and that the voltage signal (o1s) from the output of the operational amplifier (A) is conducted to an input of a circuit (BPFaA),
which is both a band-pass filter for components in the frequency band of said modulation signal as well as an amplifier and wherefrom said output signal (os) having reduced voltage of the DC component and the low-frequency components,
whose frequency lies below the lower frequency limit of a modulation signal in the received signal (rs).

12 more elements

Dependencies are inferred from the claim text.