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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

FEATURES

• Low-noise, wide dynamic range amplifier

• Very low noise figure

• Dual balanced mixer for at least 30 dB on-chip image

rejection

• IF I/Q combination network for 175 MHz

• Down-conversion mixer for closed-loop transmitters

• Independent TX/RX fast on/off power-down modes

• Very small outline packaging

• Very small application (no image filter).

APPLICATIONS

• 900 MHz front-end for GSM hand-portable equipment

• Compact digital mobile communication equipment

• TDMA receivers.

GENERAL DESCRIPTION

UAA2073AM contains both a receiver front-end and a high

frequency transmit mixer intended for GSM

(Global System for Mobile communications) cellular

telephones. Designed in an advanced BiCMOS process it

combines high performance with low power consumption

and a high degree of integration, thus reducing external

component costs and total front-end size.

The main advantage of the UAA2073AM is its ability to

provide over 30 dB of image rejection. Consequently, the

image filter between the LNA and the mixer is suppressed

and the duplexer design is eased, compared with a

conventional front-end design.

Image rejection is achieved in the internal architecture by

two RF mixers in quadrature and two all-pass filters in

I and Q IF channels that phase shift the IF by 45° and 135°

respectively. The two phase shifted IFs are recombined

and buffered to furnish the IF output signal.

This means that signals presented at the RF input at

LO − IF frequency are rejected through this signal

processing while signals at LO + IF frequency can form the

IF signal.

The receiver section consists of a low-noise amplifier that

drives a quadrature mixer pair. The IF amplifier has

on-chip 45° and 135° phase shifting and a combining

network for image rejection.The IF driver has differential

open-collector type outputs.

The LO part consists of an internal all-pass type phase

shifter to provide quadrature LO signals to the receive

mixers. The all-pass filters outputs are buffered before

being fed to the receive mixers.

The transmit section consists of a down-conversion mixer

and a transmit IF driver stage. In the transmit mode an

internal LO buffer is used to drive the transmit IF

down-conversion mixer.

All RF and IF inputs or outputs are balanced to reduce

EMC issues.

Fast power-up switching is possible. A synthesizer-on

(SX) mode enables LO buffers independent of the other

circuits. When SXON pin is HIGH, all internal buffers on

the LO path of the circuit are turned on, thus minimizing

LO pulling when remainder of receive chain is

powered-up.

ORDERING INFORMATION

TYPE

NUMBER

UAA2073AM

PACKAGE

NAME

DESCRIPTION

SSOP20 plastic shrink small outline package; 20 leads; body width 4.4 mm

VERSION

SOT266-1

1997 Jan 27

2

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