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UAA2073AM

Image rejecting front-end for GSM applications

Philips Electronics 

Philips Semiconductors

Image rejecting front-end

for GSM applications

Product specification

UAA2073AM

FUNCTIONAL DESCRIPTION

Receive section

The circuit contains a low-noise amplifier followed by two

high dynamic range mixers. These mixers are of the

Gilbert-cell type. The whole internal architecture is fully

differential.

The local oscillator, shifted in phase to 45° and 135°,

mixes the amplified RF to create I and Q channels.

The two I and Q channels are buffered, phase shifted by

45° and 135° respectively, amplified and recombined

internally to realize the image rejection.

Pin SBS allows sideband selection:

• fLO > fRF (SBS = 1)

• fLO < fRF (SBS = 0).

Where fRF is the frequency of the wanted signal.

Balanced signal interfaces are used for minimizing

crosstalk due to package parasitics. The RF differential

input impedance is 150 Ω (parallel real part), chosen to

minimize current consumption at best noise performance.

The IF output is differential and of the open-collector type,

tuned for 175 MHz. Typical application will load the output

with a 680 Ω resistor load at each IF output, plus a 1 kΩ

load consisting in the input impedance of the IF filter or in

the input impedance of the matching network for the IF

filter. The power gain refers to the available power on this

1 kΩ load. The path to VCC for the DC current should be

achieved via tuning inductors. The output voltage is limited

to VCC + 3Vbe or 3 diode forward voltage drops.

Fast switching, on/off, of the receive section is controlled

by the hardware input RXON.

handbook, full pagewidth

VCC1

RFINA

RFINB

GND1

LNA

MIXER

IF

amplifier

MIXER

IF

amplifier

LOIN

+45o

SBS

IF

COMBINER

+135o

RXON

IFA

IFB

MBH188

Fig.3 Block diagram, receive section.

1997 Jan 27

5

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