ADMV1455BBCZ-R7 datasheet(78/141 Pages) AD

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Data Sheet

ADMV1455

THEORY OF OPERATION

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MIXER OVERVIEW

The ADMV1455 contains an image rejection down converting I/Q

mixer with excellent linearity and noise figure. The necessary LO

signals, 2×LO_I and 2×LO_Q, to drive the mixer come from the

LO signal chain. The output from the RF signal chains, RF_C,

also feeds into the mixer. The mixer supports RF and LO input

frequencies up to 55GHz. The quadrature outputs of the mixer,

IF_I and IF_Q, are then used to drive the IF signal chain and I/Q

baseband signal chain. Figure 176 shows the mixer.

The mixer contains a gate selection bit field in Register 0x17D. For

I/Q baseband mode, set this register to 0, and for IF mode, set this

Figure 176. Mixer Diagram

MIXER SIDEBAND SELECTION

The ADMV1455 mixer sideband can be selected by swapping the

mixer LO inputs, 2×LO_I and 2×LO_Q. To swap these inputs, use

is for cases where the RF frequency > the 2×LO frequency. Set this

bit to 1 for the lower sideband, which is for cases where the RF

frequency < the 2×LO frequency.

I/Q BASEBAND SIGNAL CHAINS

The I/Q baseband signal chains of the ADMV1455 support frequen-

cies from DC to 8GHz and consist of baseband amplifiers. The

baseband amplifiers include VOCM adjustment and DC offset correc-

tions. Figure 177 shows the I/Q baseband signal chains.

To use the I/Q baseband signal chains, set Register 0x184 to 0. Set

If not using the I/Q baseband signal chains, set Register 0x107,

Bits[3:0], to 1 to power down the baseband amplifiers.

The I/Q baseband outputs are internally DC-coupled with a 75Ω

differential output impedance, which allows the outputs to interface

with either 50Ω or 100Ω differential load impedance. When these

outputs are not used, they can be left floating.

Figure 177. IF and I/Q Baseband Signal Chains

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