WT21 View Datasheet(PDF) - Unspecified
Part Name
Description
MFG CO.
'WT21' PDF : 54 Pages View PDF
10
Bluetooth Radio
10.1 Bluetooth Receiver
The receiver features a near-zero Intermediate Frequency (IF) architecture that allows the
channel filters to be integrated onto the die. Sufficient out-of-band blocking specification at the
Low Noise Amplifier (LNA) input allows the receiver to be used in close proximity to Global
System for Mobile Communications(GSM) and Wideband Code Division Multiple Access (W-
CDMA) cellular phone transmitters without being desensitised. The use of a digital Frequency
Shift Keying(FSK) discriminator means that no discriminator tank is needed and its excellent
performance in the presence of noise allows WT21 to exceed the Bluetooth requirements for co-
channel and adjacent channel rejection.
For EDR, the Demodulator contains an ADC which is used to digitise the IF received signal. This
information is then passed to the EDR modem.
10.1.1 RSSI Analogue to Digital Converter
The Analogue to Digital Converter (ADC) implements fast Automatic Gain Control (AGC). The
ADC samples the Received Signal Strength Indicator (RSSI) voltage on a slot-by-slot basis. The
front-end LNA gain is changed according to the measured RSSI value, keeping the first mixer
input signal within a limited range. This improves the dynamic range of the receiver, improving
performance in interference limited environments.
10.2 Bluetooth Transmitter
The transmitter features a direct IQ modulator to minimise the frequency drift during a transmit
timeslot, which results in a controlled modulation index. Digital baseband transmit circuitry
provides the required spectral shaping.
The internal Power Amplifier (PA) has a maximum output power of +6dBm.
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