EM2420-STR Ember, EM2420-STR Datasheet - Page 56

• Manufacturer Part Number: EM2420-STR
• Description: IC RF TXRX ZIGBEE 2.4GHZ 48-QLP
• Manufacturer: Ember

Specifications of EM2420-STR

• Mfg Application Notes: EM2420
• Frequency: 2.4GHz
• Data Rate - Maximum: 250kbps
• Modulation Or Protocol: 802.15.4
• Applications: ZigBee™
• Power - Output: -3dBm
• Sensitivity: -94dBm
• Voltage - Supply: 2.1 V ~ 3.6 V
• Current - Receiving: 19.7mA
• Current - Transmitting: 17.4mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 48-QLP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Memory Size: -

The simplest way of making a PER
measurement is to use another
the reference transmitter. 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].
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.
PCB Layout Recommendations
Ember’s EM2420 reference design fully
describes PCB considerations.
A four layer PCB is highly recommended.
In our reference design, the top layer is
used for signal routing, and the open
areas
connected to ground using several vias.
Layer 2 has not been used in our EM2420
reference designs. Layer 3 is used for
power routing and the bottom layer serve
as ground plane with a little routing.
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
Antenna Considerations
The
various types of antennas. A differential
antenna like a dipole would be the easiest
to interface without a balun (balanced to
unbalanced transformation network).
The length of the λ/2-dipole antenna is
given by:
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.
Ember Part Number: 120-0049-000D
EM2420
are
can be used together with
L = 14250 / f
filled
with
metallization
EM2420
EM2420 Datasheet
as
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.
and connected to the ground plane by
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 Ember website.
Other commonly used antennas for short-
range
helical and loop antennas. The single-
ended monopole and helical antennas
would require a balun network between
the differential output and the antenna.
Monopole
antennas with a length corresponding to
one quarter of the electrical wavelength
(λ/4). They are very easy to design and
can be implemented simply as a “piece of
wire” or even integrated into the PCB.
n-1
0
32n-1
xnor c
of length n symbols, the desired chip
xor c
communication
1
), (c
0
, c
antennas
32n
1
1
, c
) where c
xor c
2
in
, …, c
2
), (c
order
EM2420
32n-1
are
are
2
of length 32n
32n
xnor c
Page 56 of 84
to
monopole,
0
may be
resonant
, s
3
), … ,
1
avoid
, … ,