CML Microcircuits

COMMUNICATION SEMICONDUCTORS

PRODUCT PREVIEW

ATB010 – dPMR RF Demonstrator

© 2009 CML Microsystems Plc

Page 2 of 6

August 2009

Tx/Rx

Switch

LNA

PA

PLL

Rx Section

Tx Section

SAW

Image Filter

Xtal Filter

(Fc = 45MHz)

RSSI

Data/Audio

MOD2

AUXDAC4

Power

Detector

LO 1

LO 2

44.545MHz

VCTXO

19.2MHz

MOD1

AUXADC3

AUXDAC1

The ATB010 functional block diagram

On-board Circuits

Front end LNA

A UHF discrete bipolar LNA. Along with subsequent stages, this is biased to achieve the demanding

receiver intermodulation requirements.

SAW image filter

This filter (after the LNA) is an 8MHz bandwidth 446MHz SAW filter providing rejection of image and

other spurious responses.

Mixer

After approximately 2dB of attenuation, a diode ring mixer is used to convert from 446MHz to the 1st IF

of 45MHz. This requires approximately +4dBm LO drive.

Post mixer IF amplifier

An isolation amplifier that provides a good match at its output to the crystal filter. The input from the

mixer is matched by a Pi network giving a good 50Ohm match.

IF crystal filter

A 4-pole, fundamental mode, 2 x UM1 packaged crystal filter with a passband of approximately

+/-3.75kHz. Correct matching of the filters is necessary to achieving optimum performance.

Post filter amplifier

A resistive termination to the FM IF IC input. It also provides a high input impedance to the crystal filter

output matching network. The gain provided overcomes the losses in not matching to the high

impedance of the FM IF IC input.