Texas Instruments TRF7960TB, Руководство пользователя, Страница: 15 / 21

RES(total)
2
1
C =
ω L
RES(total)
2
1
C =
(2π × 13.56 MHz) × 0.95 μH
RES(total)
C = 145.157 pF
PAR
R
Q =
2πfL
PAR
R = 2πfLQ
PAR
R = 1.29 kΩ
PAR
R = 647 Ω
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Antenna Tuning Details
13 Antenna Tuning Details
Module antenna as shipped is tuned for 50- Ω impedance at 13.56 MHz. It has a nominal bandwidth of 1.3
MHz, which results in a quality factor of approximately 10. Module antenna circuit has a board mounted
UFL connector installed for users to experiment with different tuning solutions or disconnect the onboard
antenna and experiment with antennas of their own design or application. Below are some
design/application notes to reference when changing the antenna Q factor or experimenting further to
improve a particular application.
TRF7960TB coil antenna tuning details starts with calculations to produce the theoretical values shown
below (and based on measurements of antenna coil on Rev B board.) Coil value nominally measures 0.95
µH at 13.56 MHz and XL = 0.8 + j80.8 = 0.990 at 63.4°.
To calculate the necessary values required for course resonance tuning and proper Q setting of the
antenna,
Equation 1 is used.
(1)
Where, w = 2 p f
Therefore,
(2)
(3)
The dampening resistor value can now be calculated for a desired Q value using Equation 4 .
(4)
Therefore,
(5)
For Q = ~20 (ISO15693 operations):
(6)
Use standard value of 1.3 k Ω .
For Q = ~10 (ISO14443 and ISO15693 operations):
(7)
Use standard value of 680 Ω .
15 SLOU297 – October 2010 TRF7960TB HF RFID Reader Module
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