13

T2802

4509F–DECT–10/03

Functional Description

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= f

tunning in production an integrated 5-bit digital-to-analog (D/A) converter is provided to

control the on-chip varicap diode.

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 via a TX/RX SWITCH to the TX_DRIVER. This

bus-controlled driver amplifier supplies typically +3 dBm 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 by a

capacitor at the RAMP_SET pin.

Synthesizer

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

fully integrated VCO (including on-chip inductors and varactors). A 3-bit digital-to-analog

converter is used to pretune the frequency. The output signal is frequency-divided to

supply the desired frequency 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 (f

Unlimited multislot operation is possible by using the integrated advanced closed-loop

modulation concept based on the modulation compensation circuit MCC.

Power Supply

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

PNP transistor is implemented. Multiple power-down and current saving modes are

provided.