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Ch2. Reader Antenna Design

Ch2. Reader Antenna Design. (Part II). Outline. Antenna Design for different system Directly matched antenna Proximity Reader Antenna : Design Example Reference. RC 500 Reader IC and system. (RC 500 ). (8051 ). (Direct Matched antenna application system).

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Ch2. Reader Antenna Design

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  1. Ch2. Reader Antenna Design (Part II)

  2. Outline • Antenna Design for different system • Directly matched antenna • Proximity Reader Antenna : • Design Example • Reference

  3. RC 500 Reader IC and system (RC 500 ) (8051 ) (Direct Matched antenna application system)

  4. 使用HF RFID技術開發點名系統 常用的讀取器天線設計做法是直接匹配到700歐姆的天線輸入阻抗(發射機輸出端阻抗是700歐姆 天線電路 諧振電路 接收電路 匹配 匹配 或其他讀取器 700 Ohm 濾波器 天線 值接完全匹配天線電路(700Ohm)

  5. 50  Short Range antenna Directly Matched antenna (700 ) 50  Full Range antenna I. Antenna Design for different system A. EMC-Filter and Impedance Matchingof

  6. RC500 / RC400 Zi Tx1 Zi: complex source impedance Zi = Ri(f)+jX(f) Vi TVss Method I: EMC-Filter + Impedance Matching to 50(Short Range : cable length>30 mm, d less than <50 mm) Start: Output stage of the reader is represented by a model

  7. + Matching RC500 / RC400 EMC Filter L0 Zi Tx1 C1 Z = 50 Ohm Zi: complex source impedance Zi = Ri(f)+jX(f) C0 Vi TVss EMC-Filter + Impedance Matching to 50 (Short Range) (LPF)

  8. 13.56 MHz Z = 50  L0 Tx1 Maximum Power C1 Z RC500 RC400 C0 Minimum harmonics TVss S22 L0 = 1 H C0 = 68 pF C1 = 68 pF S21 ~ Power Out EMC-Filter + Impedance Matching to 50 (Short Range)

  9. Rx-Circuit RC 500 RX RC 400 R C 1 3 VMID R 2 C 4 AVSS Tx 50 TX1 L C 0 1 C 0 TVSS TVSS Tx-circuit TX2 Rx-Circuit: R1 = 470  … 2,7 k R2 = 820  C3 = 15 pF C4 = 100 nF Tx-Circuit: L0 = 1 H C0 = 68 pF C1 = 68 pF EMC-Filter + Impedance Matching to 50 (Short Range) The AC voltage divider of R1+C3 and R2 has to be designed taking into the AC voltage limits on pin RX

  10. Method 2: EMC Filter + Matching RC500 / RC400 Tx1 Zi L0 C0 Vi Zi: complex source impedance Zi = Ri+jX Z  700 Ohm TVss Vi C0 L0 Tx2 Zi EMC-Filter + Impedance Matching to 700(Directly Matched: directly connected or cable length < 30 mm)

  11. Rx-Circuit RC 500 RX RC 400 R C 1 3 VMID R 2 C 4 AVSS TX1 L Tx-Circuit 0 C 0 Z  700 Ohm GND TVSS 0 C 0 L TX2 Rx-Circuit: R1 = 470  … 2,7 k R2 = 820  Tx-Circuit: L0 = 1 H C0 = 136 pF C3 = 15 pF C4 = 100 nF EMC-Filter + Impedance Matching to 700(Directly Matched) (up to 100 mm)

  12. EMC Filter + Matching RC500 / RC400 Tx1 Zi L0 C1 C0 Vi TVss Zi: complex source impedance Zi = Ri+jX Vi C0 L0 50 Tx2 C1 Zi Method 3: EMC-Filter + Impedance Matching to 50(Full Range : cable length > 30 mm, up to 100 mm)

  13. Rx-Circuit RC 500 RX RC 400 R C 1 3 VMID R 2 C 4 AVSS TX1 L C 0 1 C 0 TVSS 0 C 1 0 C L 50 TX2 Tx-circuit Rx-Circuit: R1 = 470  … 2,7 k R2 = 820  Tx-Circuit: L0 = 1 H C0 = 68 pF C1 = 82 pF C3 = 15 pF C4 = 100 nF EMC-Filter + Impedance Matching to 50(Full Range)

  14. Antenna Circuitry RC500 RC400 (or other Reader) Rx Rx- Circuit Tx Matching Matching Antenna EMC- Filter Antenna Design EMC-Filter and Impedance MatchingSummary

  15. 1) Matching - 50-Short-Range - Directly-Matched - 50-Full-Range 2) Resonance 3) Tuning 4) Q-factor with the same receive circuit 5) Finetuning 6)Receive Circuit 6) Receive Circuit Antenna Design EMC-Filter and Impedance MatchingSummary

  16. Directly matched antenna Proximity Antenna Training for 13.56 MHz

  17. Directly matched antenna RC500 RC400 (or other Reader) Rx Rx- Circuit Tx Matching Matching Antenna Z=700 Z=700 EMC- Filter Directly matched antenna

  18. ! load impedance = 700 1) Matching 1) Matching 2) Resonance resonance at 13.56 MHz 4) Q-factor quality factor  35 quality factor  100 6) Receive Circuit Directly matched antenna Requirements: 2) Resonance 3) Tuning 4) Q-factor 5) Finetuning

  19. Directly matched antenna 3) Tuning 4) Q-factor 5) Finetuning 6) Receive Circuit Guideline: 1) Matching • Design a coil • Calculate the parallel capacitance • Tune resonance and impedance • Connect antenna to the RC500 • Tune again • Check (and adjust) the Q-factor • Finetune resonance and impedance • Find the values for Rx-circuit 2) Resonance 3) Tuning 4) Q-factor 5) Finetuning 6) Receive Circuit

  20. Directly matched antenna Complete antenna Antenna Coil C1a and C2a in parallel to achieve the required matching values!

  21. RCoil La Estimation: La+b = L: coil inductance l: length of the conductor circular: l = 2**r (r=coil radius) square l = 4*a (a lateral length) d: diameter of the conductor N: number of turns : shape factor  =1.07 for circular coils =1.54 for square coils Lb RCoil Directly matched antenna Antenna coil L and R of the antenna coil shall be measured at 13.56 MHz (impedance analyser or L-C-R Meter). @13.56 MHz! D or width of the PCB conductor)

  22. RCoil 1.5 L [µH] 1 0.5 La 0 5 10 15 20 antenna radius [cm] 2 Lb N RCoil 1 0 5 10 15 20 antenna radius [cm] Directly matched antenna Antenna coil

  23. Directly matched antenna Simplification Due to the symmetrical circuitry of the whole antenna the antenna can be simplified: Rext is used to adjust quality factor!

  24. Consider the power consumption! • MIFARE Q = 35 • I*CODE Q = 100 General: Directly matched antenna Calculate the external resistor Rext is used to adjust quality factor! It is small and always overestimated!

  25. with Directly matched antenna Calculate the capacitors Remark: there is an Excel-Sheet available, that supports this calculation.

  26. 1 2 measured calculated Directly matched antenna Estimation: Startvalues for the tuning Rext is small and always overestimated!

  27. Start tune phase to 0° ± 10° with C2 possible ? fres>13.56MHz ? increase C2 no yes yes no decrease C2 Z < Zant-10%? yes decrease C1 no Tuning OK |Z|=Zant ± 10% phase=0° ± 10° Z >Zant+10% ? yes no increase C1 Directly matched antenna Tune resonance and impedance

  28. 80 3500 13.56 MHz 60 3000 40 2500 20 2000 0 1500 |Zin| [] phase [deg.] -20 2000 -40 Zant 1500 -60 1000 -80 500 phase -100 0 10 11 12 13 14 15 16 17 18 f [MHz] Directly matched antenna Tune resonance and impedance

  29. Directly matched antenna Connect Antenna to the RC500 Guideline: • Design a coil • Calculate the parallel capacitance • Tune resonance and impedance • Connect antenna to the RC500 • Tune again • Check (and adjust) the Q-factor • Finetune resonance and impedance • Find the values for Rx-circuit

  30. Start Matching Circuit Antenna Find dmax R C1a Add C C < 10 pF Find dmax C2a C La distance increased ? yes C2b Lb decrease C2 no R no C is added C1b yes no remove C add 2* C to C2a add 2* C to C2b Directly matched antenna Tune resonance and impedance

  31. PICC, Miller Coding

  32. PHILIPS Channel A: 500mV/DIV Timebase: 1µs/DIV 2.5µs 95% A send request command “Antenna Loop” Reader Directly matched antenna Checking the Q-Factor

  33. Modulator Source Switch 0 1 2 3 Serial Data OUT Envelope Tx Miller Coder Modulator Driver Mfin Pin3 Decoder Source Switch Serial Data IN Manchester OUT Subcarrier Demodulator Carrier Demodulator Manchester Decoder Rx Pin 29 Manchester w. Subcarrier Mfout Pin 4 0 1 2 3 Envelope MFout Select Switch Transmit NRZ RFU Subcarrier Demodulator 7 6 5 4 3 2 1 0 0 1 Digital Test Signal Directly matched antenna RC500 Serial Signal Switch

  34. RC500 test signals Pin 4 (3): Transmit NRZ 2V/Dev. Pin 4 (2): Envelope 2V/Dev. RFOut 0.5V/Div. time in msec Directly matched antenna Checking the Q-Factor

  35. Directly matched antenna Check Guideline: • Design a coil • Calculate the parallel capacitance • Tune resonance and impedance • Connect antenna to the RC500 • Tune resonance and impedance • Check (and adjust) the Q-factor • Finetune resonance and impedance • Find the values for Rx-circuit

  36. Startvalue: Insert RX-Circuitry Check the card’s answer with oscilloscope (trigger on Pin 4, Envelope) Get the max. operating distance send request command Check the received signal at the RC500 (Pin 4, Manchester) Reader Adjust R1 (valid Manchester at min. and max operating distance) Directly matched antenna Check the cards answer “Antenna-Loop” Attention: Input voltage at Pin 29 (Rx) shall not exceed ± 1.5V!

  37. RC500 test signals RFOut 1V/Dev. Pin 4 (4): Manchester with Subcarrier 2V/Dev. Pin 4 (5): Manchester 2V/Dev. time in msec Directly matched antenna Checking the Q-Factor

  38. 3) Tuning 4) Q-factor 5) Finetuning 6) Receive Circuit Directly matched antenna Summary 1) Matching • Design a coil • Calculate the parallel capacitance • Tune resonance and impedance • Connect antenna to the RC500 • Tune resonance and impedance • Check (and adjust) the Q-factor • Finetune resonance and impedance • Find the values for Rx-circuit 2) Resonance 3) Tuning 4) Q-factor 5) Finetuning 6) Receive Circuit

  39. Proximity Reader Antenna: Design Example Proximity Antenna Training for 13.56 MHz

  40. Rx-Circuit RC 500 RX RC 400 R C 1 3 VMID R 2 C 4 AVSS TX1 L Tx-Circuit 0 C 0 Z  700 Ohm GND TVSS 0 C 0 L TX2 Rx-Circuit: R1 = 2,2 k R2 = 820  Tx-Circuit: L0 = 1 H C0 = 136 pF C3 = 15 pF C4 = 100 nF EMC-Filter + Impedance Matching to 700(given parameters)

  41. Antenna Coil = open = short

  42. Results of the measurement (impedance analyser or L-C-R Meter): RCoil @13.56 MHz! La Lb RCoil Antenna Coil

  43. Calculation

  44. Calculation

  45. Due to the measurement uncertainty this value maybe not accurate. (Probably the exact value is lower!) Check the Q-factor!!! Calculation

  46. Tuning C2a Tune the resonance circuitry to the required impedance! C1a C1b C2b

  47. 使用HF RFID技術開發點名系統 讀取器天線設計與製作Part3 設計結果:線寬 1mm, 線距1mm,最外圈長55mm；寬55mm；金屬厚度0.05mm ADS模擬量測值: C1:15.4 pF C2:15.4 pF C3:151.85 pF C4:151.85 pF R1:2.3 Ohm R2:2.3 Ohm

  48. 使用HF RFID技術開發點名系統 讀取器天線設計與製作Part4 • 天線設計流程

  49. 使用HF RFID技術開發點名系統 讀取器天線設計與製作Part5 • 實驗結果 輸入阻抗圖 讀取器結構圖和輸出波形

  50. Reference Menu • AN78010-Application note — • MIFARE (14443 A) 13.56 MHz RFID Proximity Antennas • MFRC500-reader-Icdatasheet • M210_Directly_Matched_Ant_v11_RBt

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