RFM22B-868-S1 QUASAR, RFM22B-868-S1 Datasheet - Page 21

• Manufacturer Part Number: RFM22B-868-S1
• Description: MODULE, TRANSCEIVER, 20DB,SMD,868MHZ
• Manufacturer: QUASAR

Specifications of RFM22B-868-S1

• Modulation Type: FSK, GFSK, OOK
• Data Rate Max: 256Kbps
• Sensitivity: -121dBm
• Supply Voltage Range: 1.8V To 3.6V
• Supply Current: 85mA
• Interface Type: SPI
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3.5. Frequency Control
For calculating the necessary frequency register settings it is recommended that customers use the
HOPERF Register Calculator worksheet (in Microsoft Excel) available on the product website. These
methods offer a simple method to quickly determi ne the correct settings based on the application
requirements. The following information can be used to calculated these values manually.
3.5.1. Frequency Programming
In order to receive or transmit an RF signal, the desired channel frequency, f
RFM22B/23B. The carrier frequency is generated by a
reference
modulo
accumulators. This design was made to obtain the desired frequency resolution of the synthesizer. The overall
division ratio of the feedback loop consist of an integer part (N) and a fractional part (F).In a generic sense, the
output frequency of the synthesizer is as follows:
The fractional part (F) is determined by three different values, Carrier Frequency (fc[15:0]), Frequency Offset
(fo[8:0]), and Frequency Deviation (fd[7:0]). Due to the fine resolution and high loop bandwidth of the synthesizer,
FSK modulation is applied inside the loop and is done by varying F according to the incoming data; this is
discussed
fine-tune
fc[15:0] register will determine the fractional component. The equation for selection of the carrier frequency is
shown below:
The integer part (N) is determined by fb[4:0]. Additionally, the output frequency can be halved by connecting a ÷2
divider to the output. This divider is not inside the loop and is controlled by the hbsel bit in "Register 75h.
Frequency Band Select." This effectively partitions the entire 240–960 MHz frequency range into two separate
bands: High Band (HB) for hbsel = 1, and Low Band (LB) for hbsel = 0. The valid range of fb[4:0] is from 0 to 23. If a
higher value is written into the register, it will default to a value of 23. The integer part has a fixed offset of 24 added
to it as shown in the formula above. Table 12 demonstrates the selection of fb[4:0] for the corresponding
frequency band.
After selection of the fb (N) the fractional component may be solved with the following equation:
fb and fc are the actual numbers stored in the corresponding registers.
Add R/W Function/Description
Tel: [phone]
73
74
75
76
77
R/W
R/W
R/W Frequency Band Select
R/W
R/W
64000
the carrier frequency and counteract crystal tolerance errors. For simplicity assume that only the
frequency
further
Frequency Offset 1
Frequency Offset 2
Nominal Carrier
Nominal Carrier
Frequency 1
Frequency 0
in
and
Fax: [phone]
"3.5.4.
fc[15 : 0] = ⎜
f
TX
the
= 10MHz * (hbsel + 1) * ( fb[4 : 0] + 24 +
clock
Frequency
fc[15]
fo[7]
fc[7]
f
D7
carrier
⎛
⎝ 10MHz * (hbsel + 1)
of
= 10MHz × (hbsel + 1) × ( N + F )
f
OUT
fc[14]
sbsel
fo[6]
fc[6]
D6
the
f
TX
Deviation"
= 10MHz × ( N + F )
E-mail: [e-mail]
(3
hbsel
fc[13]
rd
fo[5]
fc[5]
D5
Fractional-N Synthesizer, using 10 MHz
order)
− fb[4 : 0] − 24 ⎟ * 64000
Also,
fc[12]
fo[4]
fb[4]
fc[4]
D4
ΔΣ
a
modulator.
fc[15 : 0]
fc[11]
fo[3]
fb[3]
fc[3]
64000
fixed
D3
carrier
⎞
⎠
, must be programmed into the
http://www.hoperf.com
offset
)
RFM22B/23B
fc[10]
fo[2]
fb[2]
fc[2]
D2
This
can
fo[1] fo[0]
fo[9] fo[8]
fb[1] fb[0]
fc[9] fc[8]
fc[1] fc[0]
D1
modulator
be added
D0 POR Def.
both as the
uses
BBh
00h
00h
35h
80h
to
21