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EMI/RANGE ISSUES - CR95HF

Question asked by loader.byron on May 30, 2014
Latest reply on Jul 24, 2014 by ST NFC
Hi Guys,

We are trying to build a multi-disapline access control reader terminal. The CR95HF was chosen for the design. The reader is not an OEM reader and is required to read a number of cards from Various Suppliers.

We have opted to run the RF Supply from 5V in the hope. We used the spreadsheet "CR95HF EMI Filter Calculation.xls" for the front end matching calculation and component selection.

When compared against other designs we have done, we are experiencing quite poor range with a range of Mifare tags. Our antenna design is approx 70mm x 70mm (2 turns)

We matched 2 designs, one with an emi filter and one without. Both failed CE compliance testing even though they were well matched. The one without failed badly. The one with emi filter failed on harmonics 13 and 15. 

We stopped design at that point and worked on another design but we are picking it up again to try and finish the design. 

Have you firstly got any advice on how to improve the range overall and secondly how to reduce the harmonics?






 

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