Operating instructions

2.0 Receiver

Figure 6-3: 800/900 Receiver Block Diagram

2.1 Receiver Front-End

The RF signal is received via the antenna and applied to a low-pass filter. For 800/900MHz, the filter

consists of C902, C904, C905 and L901. The filtered RF signal is passed through the antenna switch

and then applied to a pre-filter. The pre-filter comprises of a SAW filter FL401 located in between of 2

GaAs switches U400 and U403. The input and output of the GaAs switches are 50 Ohm points. The

SAW filter is a 2 in 1 filter which provides large attenuation at image, half IF and other out-band

frequencies.

The pre-filter does not need tuning by the Trident IC. Depending on the carrier frequency, the Trident

IC will enable the control line of the GaAs switches to feed the signal either 800MHz or 900MHz to

and from the SAW filter.

The output of the pre-filter is passed through a RF step attenuator (D400) to limit the amount RF

power fed into the LNA (U400). After being amplified, the RF signal is further filtered by a post-filter.

The pre and post filter are identical. The post-filter consists of U404, U405 and FL402. The post-filter

does not need any tuning by the Trident IC as well.

LNA

RF Jack

Mixer

SAW FilterSAW Filter

Crystal

Filter

IF Amp

SIGNAL

PROCESSING

Synthesizer

ABACUS IC

SSI TO OMAP

16.8MHz

Reference Clock

ntenna

First LO from AGC from Trident IC

FGU

Second LO VCO

Antenna Switch/

Harmonic Filter/

Matching Network