# US 2014/0192934 A1 · Receiver filter for dc-wander removal in a contactless smartcard > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0192934 A1 - Document ID: US20140192934A1 - Status: Published application - Kind: A1 - Application number: 13/735,780 - Filed: 2013-01-07 - Published: 2014-07-10 - Earliest claimed: 2013-01-07 - Assignees: NXP B.V. - Applicants: NXP B.V. - Inventors: Massimo Ciacci; Remco Cornelis Herman van de Beek; Ghiath Al-Kadi - Web page: https://patentgrep.com/patent/US20140192934A1 ## CPC - H04B 1/16: Circuits - H04B 1/0003: {Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain (digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00)} - H04L 25/03: Shaping networks in transmitter or receiver, e.g. adaptive shaping networks - H04L 25/06: DC level restoring means; Bias distortion correction {; Decision circuits providing symbol by symbol detection} - H04B 5/26: using coils - H04L 25/0266: {Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Embodiments of a method for processing a baseband signal in a Direct Current (DC)-suppressed system, a system for processing a baseband signal in a DC-suppressed system, and a smart card are described. In one embodiment, a method for processing a baseband signal in a DC-suppressed system involves processing the baseband signal in the analog domain with a first high pass filter (HPF), converting the processed baseband signal to a digital signal, and processing the digital signal in the digital domain with a second HPF to provide a discrete-time differentiation of the baseband signal. Other embodiments are also described. ## Claims ### Claim 1 A method for processing a baseband signal in a Direct Current (DC)-suppressed system, the method comprising: processing the baseband signal in the analog domain with a first high pass filter (HPF); converting the processed baseband signal to a digital signal; and processing the digital signal in the digital domain with a second HPF to provide a discrete-time differentiation of the baseband signal. ### Claim 2 (depends on 1) The method of claim 1, further comprising: receiving a wireless signal at an antenna of the DC-suppressed system; and demodulating the wireless signal into the baseband signal. ### Claim 3 (depends on 2) The method of claim 2, wherein the DC-suppressed system is a smart card. ### Claim 4 (depends on 3) The method of claim 3, wherein receiving the wireless signal comprises receiving the wireless signal from a smart card reader. ### Claim 5 (depends on 1) The method of claim 1, wherein processing the digital signal in the digital domain with the second HPF comprises generating an output signal, wherein the output signal is a discrete-time differentiated version of the baseband signal. ### Claim 6 (depends on 5) The method of claim 5, wherein processing the digital signal in the digital domain with the second HPF comprises compensating only the dominant pole of a transfer function of the first HPF. ### Claim 7 (depends on 1) The method of claim 1, wherein processing the digital signal in the digital domain with the second HPF comprises filtering the digital signal in the digital domain using a receiver filter. ### Claim 8 (depends on 7) The method of claim 7, wherein the receiver filter comprises a digital finite impulse response (FIR) filter. ### Claim 9 (depends on 8) The method of claim 8, wherein the FIR filter comprises a delay element, a multiplier, and an adder. ### Claim 10 (depends on 8) The method of claim 8, wherein the FIR filter is a single zero FIR filter with a single tap delay and a single coefficient. ### Claim 11 (depends on 1) The method of claim 1, wherein the DC-suppressed system is a phase-shift keying (PSK) demodulation system. ### Claim 12 (depends on 11) The method of claim 11, further comprising: receiving a wireless signal at an antenna of the PSK demodulation system; and demodulating the wireless signal into the baseband signal using a PSK demodulator. ### Claim 13 (depends on 12) The method of claim 12, wherein processing the baseband signal in the analog domain with the first HPF comprises processing the baseband signal using a phase lock loop (PLL). ### Claim 14 (depends on 13) The method of claim 13, wherein processing the digital signal in the digital domain with the second HPF comprises performing differentiation on the digital signal in the digital domain using a PLL equalizer. ### Claim 15 A system for processing a baseband signal in a Direct Current (DC)-suppressed system, the system comprising: a first high pass filter (HPF) configured to process the baseband signal in the analog domain; an analog-to-digital converter (ADC) configured to convert the processed baseband signal to a digital signal; and a second HPF configured to process the digital signal in the digital domain to provide a discrete-time differentiation of the baseband signal. ### Claim 16 (depends on 15) The system of claim 15, wherein a wireless signal is received at an antenna of the DC-suppressed system, and wherein the wireless signal is demodulated into the baseband signal. ### Claim 17 (depends on 15) The system of claim 15, wherein the DC-suppressed system is a smart card. ### Claim 18 (depends on 15) The system of claim 15, wherein the second HPF is further configured to compensate only the dominant pole of a transfer function of the first HPF. ### Claim 19 (depends on 15) The system of claim 15, wherein the second HPF comprises a digital single zero finite impulse response (FIR) filter with a single tap delay and a single coefficient. ### Claim 20 A smart card comprising: an antenna configured to receive a wireless signal; an analog front-end configured to process the wireless signal and to convert the wireless signal into a digital signal; a digital signal processing (DSP) unit configured to perform digital signal processing on the digital signal; and a processor configured to process the digital signal from the DSP unit according to one or more protocols, wherein the analog front-end comprises: a demodulator configured to demodulate the wireless signal into a baseband signal; a first high pass filter (HPF) configured to process the baseband signal in the analog domain; and an analog-to-digital converter (ADC) configured to convert the processed baseband signal to the digital signal, and wherein the DSP unit comprises a second HPF configured to process the digital signal in the digital domain to provide a discrete-time differentiation of the baseband signal.