Patent ID: 9235735
Filing Date: 2016-01-12
CPC Classification: G06K,G08B,H01Q,H04B

Claim Text:
1. A method of operating a card reader to perform a separate customization sequence to improve communication between the card reader and a contactlessly readable card situated in a local area of the card reader, which comprises steps of: producing a radio frequency magnetic field in the local area of the card reader, a magnetic field strength of the radio frequency magnetic field is controlled in order to execute communication with the contactlessly readable card, and an information transmission from the card reader to the contactlessly readable card situated in the local area prompts an execution of amplitude shift keying modulation between two non-zero magnetic field strengths, an unmodulated magnetic field strength a and a modulated magnetic field strength b; evaluating the radio frequency magnetic field with unmodulated magnetic field strength and the radio frequency magnetic field with modulated magnetic field strength for detecting and analyzing a variation in the radio frequency magnetic field by the contactlessly readable card situated in the local area; evaluating the radio frequency magnetic field with the unmodulated magnetic field strength and the radio frequency magnetic field with the modulated magnetic field strength using one of a reception inductor or reception antenna, which is different than a transmission inductor or a transmission antenna that is used, to receive the radio frequency magnetic field signal with the unmodulated magnetic field strength and the radio frequency magnetic field with the modulated magnetic field strength and ascertaining a modulation index m comparing the modulation index m customizing the magnetic field strengths when controlling a production of the radio frequency magnetic field in order to bring the modulation index m executing the separate customization sequence iteratively which includes substeps of: performing the amplitude shift keying between the unmodulated magnetic field strength a and the modulated magnetic field strength b, and varying at least one of the modulated magnetic field strength or the unmodulated magnetic field strength, in each case on a basis of a comparison between the modulation index m