ATR2406_14 Datasheet, PDF (5/26 Pages) ATMEL Corporation – Low-IF 2.4-GHz ISM Transceiver

3. Functional Description
3.1 Receiver
The RF signal at RF_IN is differentially fed through the LNA to the image rejection mixer IR_MIXER, driving the integrated
low-IF band-pass filter. The IF frequency is 864kHz. The limiting IF_AMP with an integrated RSSI function feeds the signal to
the digital demodulator DEMOD. No tuning is required. Data slicing is handled internally.
3.2 Clock Recovery
For a 1152Kbit/s data rate, the receiver has a clock recovery function on-chip.
The receiver includes a clock recovery circuit which regenerates the clock out of the received data. The advantage is that
this recovered clock is synchronous to the clock of the transmitting device (and thus to the transmitted data), which
significantly reduces the load of the processing microcontroller.
The falling edge of the clock is the optimal sampling position for the RX_Data signal, so at this event the data must be
sampled by the microcontroller. The recovered clock is available at pin 6.
3.3 Transmitter
The transmit data at TX_DATA is filtered by an integrated Gaussian filter (GF) and fed to the fully integrated VCO operating
at twice the output frequency. After modulation, the signal is frequency divided by 2 and fed to the internal preamplifier PA.
This preamplifier supplies typically +4dBm output power at TX_OUT.
A ramp-signal generator RAMP_GEN, providing a ramp signal at RAMP_OUT for the external power amplifier, is integrated.
The slope of the ramp signal is controlled internally so that spurious requirements are fulfilled.
3.4 Synthesizer
The IR_MIXER, the PA, and the programmable counter (PC) are driven by the fully integrated VCO, using on-chip inductors
and varactors. The output signal is frequency divided to supply the desired frequency to the TX_DRIVER, the 0/90 degree
phase shifter for the IR_MIXER, and to be used by the PC for the phase detector (PD) (f_PD = 1.728MHz). Open loop
modulation is supported.
3.5 Power Supply
An integrated band-gap–stabilized voltage regulator for use with an external low-cost PNP transistor is implemented.
Multiple power-down and current saving modes are provided.
ATR2406 [DATASHEET]
5
4779Q–ISM–09/14