UAA2077 データシートの表示（PDF） - Philips Electronics

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UAA2077

2 GHz image rejecting front-end

Philips Electronics 

Philips Semiconductors

2 GHz image rejecting front-end

Product specification

UAA2077BM

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 centre frequency of the receive band is adjustable by

the voltage on pin VQUADLO. This should be achieved by

connecting a resistor between VQUADLO and VCC. Over

25 dB of image rejection can be obtained by an optimum

resistor value.

A synthesizer-ON mode (SX mode) is used to power-up all

LO input buffers, thus minimizing the pulling effect on the

external VCO when entering the receive or transmit mode.

This mode is active when SXON = 1.

Transmit mixer

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

Its inputs are coupled to the transmit RF which is

down-converted to a modulated transmit IF frequency,

phase-locked with the baseband modulation.

The IF outputs are high-impedance (open-collector type).

Typical application will load the output with a differential

500 Ω load; for example, a 500 Ω resistor load, connected

to VCC for DC path, at each TX output, plus a differential

1 kΩ consisting of the input impedance of the matching

network for the following TX part. The mixer can also be

used for frequency up-conversion.

Fast switching ON/OFF, of the transmit section is

controlled by the hardware input TXON.

handbook, halfpage

VCCLO

VQUADLO

LOGND

to RX

QUAD

LOINA LOINB

to TX

MGD156

handbook, halfpage

LOIN

TX MIXER

TXOA

TXOB

TXON TXINB TXINA

MGD153

Fig.4 Block diagram, LO section.

Fig.5 Block diagram, transmit mixer.

Table 1 Control of power status

EXTERNAL PIN LEVEL

TXON

LOW

LOW

HIGH

LOW

LOW

HIGH

HIGH

HIGH

RXON

LOW

HIGH

LOW

LOW

HIGH

LOW

HIGH

HIGH

SXON

LOW

LOW

LOW

HIGH

HIGH

HIGH

LOW

HIGH

CIRCUIT MODE OF OPERATION

power-down mode

RX mode, fLO < fRF: receive section and LO buffers to RX on

TX mode: transmit section and LO buffers to TX on

SX mode: complete LO section on

SRX mode, fLO < fRF: receive section on and SX mode active

STX mode: transmit section on and SX mode active

RX mode, fLO > fRF: receive section and LO buffers to RX on

SRX mode, fLO > fRF: receive section on and SX mode active

1995 Dec 13

6

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