Other

Ams International Ag

Ams R&d Analogni Polprevodniki, D.o.o.

Ids Microchip Ag

Kunc, Vinko

Vodopivec, Andrej

Atanasijevic-kunc, Maja

Stern, Anton

Maja Atanasijevic-Kunc

Vinko Kunc

Andrej Vodopivec

Anton Stern

Jernej Rozman

A method is performed for a signal transmitted by an RFID interrogator being a radiofrequency electromagnetic sine wave. An amplitude noise contribution RSdto a demodulated received signal RSd within a frequency interval of a low-pass filter is determined by means of a measured demodulated transmitted signal TSd as RSd=k.TSd in that a dc component DCin said demodulated received signal RSd and a dc component DCin said demodulated transmitted signal TSd are measured and a conversion factor k is determined as k=DC:DC. A receiver output signal O is continuously generated out of the received signal by subtracting said amplitude noise contribution RSdfrom the demodulated received signal RSd, filtering the cleaned signal RSd-k.TSd by the low-pass filter and amplifying it. The conversion factor is determined in an exceptionally simplified way as said ratio of said dc components. No receiving interruptions are needed.

Method for reducing amplitude noise in a received signal within an RFID interrogator

A calibrating output signal of the transmitter is generated in an interrogator in that a first output signal of a local oscillator is shallowly amplitude-modulated with a pilot signal having a frequency at which a contactless-card encodes data. A receiver reference signal is generated by combining the calibrating output signal of the transmitter and a signal whose carrier signal has a frequency equaling the frequency of the local oscillator signals, conducting the combined signal through a band-pass filter and amplifying it. A first and a second receiver output signals are cleared by subtracting the receiver reference signal, which has been attenuated by a calibrated factor and has a calibrated polarity, from the first and the second receiver output signal, respectively. The attenuation factor and the polarity of the receiver reference signal are sporadically calibrated for each of both receiver output signals by determining and setting the attenuation factor and the polarity of the receiver reference signal as a pair of values for each of both receiver output signals, at which pair of values the first and the second cleared receiver output signals have the lowest amplitude. The signal-to-noise ratio for the interrogator receiver output signal is improved, because this signal no longer contains an amplitude noise of the interrogator transmitter.

Method for reducing a noise in a signal received in a contactless-card interrogator and a circuit to perform said method

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.

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

According to the method for regulating the supply voltage of an electronic circuit a regulating element with variable resistivity and the outer supply voltage being applied to an input terminal of said regulating element is controlled by an amplified difference between a reference voltage and a part of a regulated supply voltage whereat at first an instant, on which the regulating circuit and the electronic circuit start operating, is detected, and then such value of the reference voltage is set on said instant that the regulated supply voltage will equal a maximum allowable supply voltage of the electronic circuit and the supplied electronic circuit puts itself in a state of a maximum current consumption. Then an operating voltage drop across said regulating element is measured at regular time intervals and the reference voltage is then each time reduced by one degree until said operating voltage drop is below or equals a chosen most appropriate value of said operating voltage drop. The supplied electronic circuit puts itself in a state of a normal current consumption when said operating voltage drop has exceeded the chosen most appropriate value of said voltage drop. According to a variant embodiment the operating voltage drop is then uninterruptedly measured and, if its value decreases below a chosen minimum value of said operating voltage drop due to a disturbance in the outer supply voltage, a flag is set in a memory in the case of a disturbance potentially dangerous to the electronic circuit.

Method for regulating supply voltage

The measurement of a very low intensity of an electric current is carried out by 5 integrating the electric current over integration cycles having a time period ti and measuring a peak value of a sawtooth voltage at an integrated circuit output each time at the end of the integration cycle, whereat noise voltage components of a frequency above a cut-off frequency, which has a value of the order of magnitude (0,1&#xd7;2&#x3c0;&#xd7;ti), being parts of a voltage of a noise generated in an operational amplifier comprised in the integrated circuit are filtered out of the said sawtooth voltage and noise components, which have the origin in the high-frequency voltage components of Johnson noise, which appear in the low-frequency spectral part of the sawtooth voltage as aliasing, are subtracted from a filtered sawtooth voltage. A higher absolute accuracy of the measurement is achieved by means of a reduction of the direct as well as the aliasing contribution of the Johnson noise of the operational amplifier in the measuring circuit.

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Ljubljana, Slovenia

Maja Atanasijevic-Kunc