ATSAM4S-WPIR-RD Atmel, ATSAM4S-WPIR-RD Datasheet - Page 25

• Manufacturer Part Number: ATSAM4S-WPIR-RD
• Description: Development Boards & Kits - ARM SAM4S16 W.PIR CAMERA REF. DESIGN
• Manufacturer: Atmel

Specifications of ATSAM4S-WPIR-RD

• Rohs: yes
• Product: Reference Designs
• Tool Is For Evaluation Of: ATSAM3S4BA
• Core: ARM Cortex M3
• Interface Type: JTAG, USB
• Operating Supply Voltage: 5 V
• Data Bus Width: 32 bit
• For Use With: RF231USB-RD

Figure 5-9. Antenna tuning test board (without RF shielding).
To avoid sheath currents it is important to use a ferrite bead fixed on the coaxial cable. The bead should be as close as
possible at the DUT (see
Figure
5-10). The use of a second bead at the coaxial port of the NWA is also practical.
Furthermore, the RF shielding with a cutout at one side is placed on its appropriate footprint.
Figure 5-10. DUT with metal shielding plugged into laptop, coaxial cable with ferrite bead.
At first the device has to be calibrated for network analyzer measurements. This is done by preparing three additional
devices: one with a 50Ω load, another one with a short circuit and the last one with an open end. The reference point for
all devices is the matching part L3. Because of the existing 0402 footprint it is easy to create a load, short and open
end.
After calibration the DUT has to be measured without matching parts L2, L3 and C41. The resonance behavior depends
on the measurement position and all influencing elements in the vicinity. Without matching parts the antenna resonance
frequency is too high
(Figure
5-11).
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Atmel AVR2030: ATRF231USB – Hardware User Manual [APPLICATION NOTE]
42018A−AVR−08/2012