capacitor placement of C63 and C62. See schematics for details. The RF layout is identical to
the CC2420EM, which is part of the CC2420DK Development Kit.
Antenna
The PCB antenna is a so-called Inverted-F type. The Inverted-F antenna is a wire monopole
where the top section is folded down to be parallel with the ground plane. By folding the
antenna down you will reduce the height and maintain a resonant wire length. A capacitance
will be introduced to the input impedance of the antenna due to the parallel section. However,
as a rule of thumb design guide, the height (L+H) will be approximately equal to a
quarter wavelength (
λ
/4). A reduction of the antenna height (H) will in general decrease the
antenna bandwidth. Please see Figure 2 for the antenna dimensions.
Figure 2: Antenna dimensions
The height of the antenna is defined as the distance from the ground plane to the parallel
section, and the length is from the end of the antenna parallel section to the feed point.
Length: L = (26.19 mm – 9.19 mm + 1.22 mm x ½) = 17.61 mm
Height: H = (6.17 mm + 0.97 mm - 1.19 mm x ½) = 6.55 mm
Quarter wavelength:
λ
/4 = (L + H) = 17.61 mm + 6.55 mm = 24.16 mm
The physical size of the antenna is decreased somewhat compared to the theoretical length,
(
λ
= c/4*f = 3x10
8
/ 4x2.45x10
9
) = 30.61 mm
The radiated pattern for the PCB antenna was measured with the horizontal polarization
direction for the CC2420DB by measuring with vertical and horizontal mounting of the
demonstration board.
Important:
Chipcon AS
SmartRF
®
CC2420DBK Demonstration Board Kit User Manual
(rev. 1.3) 2004-11-03 Page 5/ 52
