T2801 Просмотр технического описания (PDF) - Atmel Corporation

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T2801

DECT Single-Chip Transceiver

Atmel Corporation 

3. Functional Description

3.1 Receiver

The RF signal at RF_IN is fed to an image rejection mixer IR_MIXER with its differential outputs

MIXER_OUT1 and MIXER_OUT2 driving an IF-SAW filter at 110.592 MHz or 112.32 MHz. The

IF amplifiers IF_AMP1 and IF_AMP2 with an external IF_TANK and an integrated RSSI function

feed the signal to the demodulator DEMOD working at f = fIF/2 ([55 MHz) and finally to an inte-

grated baseband filter BB. For demodulator tuning in production, an integrated 5-bit

Digital-to-Analog (D/A) converter is provided to control the on-chip varicap diode.

3.2 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 fre-

quency-divided by 2 and fed via a TX/RX SWITCH to the TX_DRIVER. This bus-controlled

driver amplifier supplies typical +3 dBm output power at TX_OUT. An integrated ramp-signal

generator, RAMP_GEN, provides a ramp signal at RAMP_OUT for the external power amplifier.

The slope of the ramp signal is controlled by a capacitor at the RAMP_SET pin.

3.3 Synthesizer

The IR_MIXER, the TX_DRIVER and the programmable counter PC are driven by the fully inte-

grated VCO (including on-chip inductors and varactors). An 3-bit digital-to-analog converter is

used to pretune the frequency. The output signal is frequency-divided to supply the desired fre-

quency to the TX_DRIVER, 0/90 degree phase shifter for the IR_MIXER and to be used by the

PC for the phase detector PD (fPD = 3.456 MHz). Unlimited multislot operation is possible by

using the integrated advanced closed-loop modulation concept based on the modulation com-

pensation circuit MCC.

3.4 Power Supply

An integrated bandgap-stabilized voltage regulator for use with an external low-cost PNP tran-

sistor is implemented. Multiple power-down and current saving modes are provided.

14 T2801

4567B–DECT–03/06

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