CC2400 Chipcon AS, CC2400 Datasheet - Page 41

• Manufacturer Part Number: CC2400
• Description: 2.4 GHz RF Transceiver
• Manufacturer: Chipcon AS

Linear IF and AGC Settings
CC2400
where the signal amplification is done in
an analog VGA (variable gain amplifier).
The gain of the VGA is controlled by the
the digital part of the IF-chain after the
ADC (Analog Digital Converter).
The AGC (Automatic Gain Control) loop
ensures that the ADC operates inside its
RSSI
CC2400
Signal Strength Indicator) giving a digital
value
RSSI.RSSI_VAL[7:0] register.
The RSSI reading provides a measure of
the signal power entering the RF input.
The scale is logarithmic, so that
RSSI_VAL provides a value in dB.
The number of samples that are used to
calculate the average signal amplitude is
controlled
RSSI.RSSI_FILT[1:0]
RSSI filter length (averaging) can be done
over up to 8 symbols. This will determine
the response time of the RSSI.
Chipcon AS
that
is based on a linear IF chain
has a built-in RSSI (Received
SmartRF
can
be
®
CC2400 PRELIMINARY Datasheet (rev. 1.1), 2003-10-02
by
read
register. The
form
the
the
SmartRF
dynamic range by using an analog/digital
feedback loop.
The AGC characteristics are set through
the AGCCTRL, AGCTST0, AGCTST1 and
AGCTST2 registers.
The RSSI measurement can be referred to
the power at the RF input pins by using
the following equation:
where
RSSI_OFFSET is –54dB. (If the gain in
the LNA/Mixer is changed from the default
settings, the offset is changed.)
A typical plot of the RSSI_VAL reading as
function of input power is shown in Figure
20 (for 1Mbps).
P = RSSI_VAL + RSSI_OFFSET [dBm]
the
®
nominal
CC2400
value
Page 41 of 73
of