CC2420 Chipcon AS, CC2420 Datasheet - Page 57

• Manufacturer Part Number: CC2420
• Description: 2.4 GHz RF Transceiver for IEEE 802.15.4 and ZigBee
• Manufacturer: Chipcon AS

The simplest way of making a PER
measurement will be to use another
CC2420
However, this makes it difficult to measure
the exact receiver performance.
Using a signal generator, this may either
be set up as O-QPSK with half-sine
shaping or as MSK. If using O-QPSK, the
phases must be selected according to [1].
PCB Layout Recommendations
A four layer PCB is highly recommended.
The second layer of the PCB should be
the used as a ground plane.
The top layer should be used for signal
routing, and the open areas should be
filled with metallisation connected to
ground using several vias.
The area under the chip is used for
grounding and must be well connected to
the ground plane with several vias.
The ground pins should be connected to
ground as close as possible to the
package pin using individual vias. The de-
coupling capacitors should also be placed
as close as possible to the supply pins
and connected to the ground plane by
Antenna Considerations
CC2420
types of antennas. A differential antenna
like a dipole would be the easiest to
interface not needing a balun (balanced to
un-balanced transformation network).
The length of the λ/2-dipole antenna is
given by:
Chipcon AS SmartRF ® CC2420 Preliminary Datasheet (rev 1.0), 2003-11-17
•
can be used together with various
The
control register should be set to
20,
Demodulator,
Synchroniser and Data Decision
section.
as the reference transmitter.
as
L = 14250 / f
MDMCTRL1.CORR_THR
described
in
Symbol
the
SmartRF
If using MSK, the chip sequence must be
modified such that the modulated MSK
signal has the same phase shifts as the O-
QPSK sequence previously defined.
For a desired symbol sequence s
s
sequence c
is found using table lookup from Table 3
on page 21. It can be seen from
comparing the phase shifts of the O-QPSK
signal with the frequency of a MSK signal
that the MSK chip sequence is generated
as:
(c
(c
arbitrarily selected.
separate vias. Supply power filtering is
very important.
The external components should be as
small as possible (0402 is recommended)
and surface mount devices must be used.
Caution should be used when placing the
microcontroller
interference with the RF circuitry.
A Development Kit with a fully assembled
Evaluation Module is available. It is
strongly advised that this reference layout
is followed very closely in order to get the
best performance.
The schematic, BOM and layout Gerber
files for the reference designs are all
available from the Chipcon website.
where f is in MHz, giving the length in cm.
An antenna for 2450 MHz should be 5.8
cm. Each arm is therefore 2.9 cm.
Other commonly used antennas for short-
range
helical and loop antennas. The single-
ended monopole and helical would require
a balun network between the differential
output and the antenna.
n-1
0
32n-1
xnor c
of length n symbols, the desired chip
xor c
communication
1
), (c
0
, c
32n
1
1
, c
) where c
xor c
2
in
®
, …, c
2
), (c
order
CC2420
32n-1
are
2
of length 32n
xnor c
32n
Page 57 of 85
to
monopole,
0
may be
, s
3
), … ,
1
avoid
, … ,