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UAA2073M

Image rejecting front-end for GSM applications

Philips Electronics 

Philips Semiconductors

Image rejecting front-end

for GSM applications

Product specification

UAA2073M

Local oscillator section

The local oscillator (LO) input directly drives the two

internal all-pass networks to provide quadrature LO to the

receive mixers.

The LO differential input impedance is 50 Ω

(parallel real part).

A synthesizer-on (synthon) mode is used to power-up the

buffering on the LO inputs, minimizing the pulling effect on

the external VCO when entering transmit or receive

modes.

This mode is active when the SYNTHON input is HIGH.

Table 1 shows status of circuit in accordance with TXON,

RXON and SYNTHON inputs.

Transmit mixer

This mixer is used for down-conversion to the transmit IF.

Its inputs are coupled to the transmit RF and down-convert

it to a modulated transmit IF frequency which is phase

locked with the baseband modulation.

The transmit mixer provides a differential input at 200 Ω

and a differential output driver buffer for a 1 kΩ load. The

IF outputs are low impedance (emitter followers).

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

by the hardware input TXON.

handbook, halfpage

to RX

VCC2

RXON

TXON

SYNTHON

GND2

RX

CURRENT

TX

REGULATORS IF

QUAD

LO

to TX

LOINA

LOINB

MBG796

handbook, halfpage

LOIN

TX MIXER

TXON

TXINB

SYNTHON TXINA

TXOIFA

TXOIFB

MBG797

Fig.4 Block diagram, LO section.

Fig.5 Block diagram, transmit mixer.

1995 Dec 07

6

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