SkyeModule M1 Antenna Design Guide
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Skyetek Inc
1525 Market St. Ste 200
Denver, CO 80202
www.skyetek.com
Main 720.328.3425 Fax:720.228.2400
3
Custom Antennas
Inductive loop RFID antennas can be made from any electrically conducive material such as tape,
wire, or tubing. The basic requirement is that the antenna is a “loop” with one or more turns. As a
general rule, circular and square antenna loops are optimal geometries. The length to width ratio of a
rectangular antenna should not exceed about 3:1. You can design a custom antenna to provide more
read range and more read coverage than you can get from the internal antenna of the M1.
L1 is the RFID loop antenna. The antenna can be made from wire, copper tape, copper tubing, or
other conductive materials.
ANT has a typical output impedance of 50-ohm at 13.56MHz. The external antenna should be
matched to this 50-ohm output drive impedance. The series capacitance Zs provides the matching
adjustment.
3.1
Design Procedure
The following antenna design procedure can be used. Start with a measured or calculated
inductance for L1, then calculate the capacitor values, then measure and adjust for optimal
performance.
1.
Determine the inductance of L1.
a.
Build and measure the inductance of L1.
b.
Design and calculate the inductance of L1.
2.
Determine the capacitance Cp. Pick appropriate values for C2 and C3.
3.
Determine the capacitance Cs for matching the M1 output impedance to the antenna input
impedance. Pick appropriate values for C1 and C4.
The resonant frequency of the parallel impedance Zp circuit is governed by the following equation
where,
L1 is the inductance of the antenna loop
R4 is ignored Cp = C2 || C3 ƒ = 13.56MHz is the desired resonant frequency.
