ADMV1455BBCZ-R7 datasheet(76/141 Pages) AD

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Data Sheet

ADMV1455

THEORY OF OPERATION

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Rev. 0 | 76 of 141

DSA1

The ADMV1455 includes a wideband, standalone, digital step at-

tenuator, DSA1. This attenuator is intended for use in systems

where more dynamic range control is required at the expense of

the system noise figure. The device includes 15dB of attenuation

control, with steps of 1dB. The attenuation is proportional to the

value programmed.

When using the bypass registers (Register 0x28A set to 1), use

the bypass registers (Register 0x28A set to 0), use Register 0x600,

Bits[3:0] to set the DSA1 state.

To use DSA1, the output of the previous stage in a system line

up must be connected to DSA_IN and, then, DSA_OUT must be

connected to RF_IN through a short PCB trace. If DSA1 is not

used, both DSA_IN and DSA_OUT can be left floating.

RF SIGNAL CHAINS

The RF_IN ball of the ADMV1455 is connected directly to a LNA,

followed by two switch selectable, wideband, RF signal chains. The

low band, RF signal chain operates from 17.7GHz to 34GHz, and

the high band, RF signal chain operates from 30GHz to 55GHz.

Each signal chain includes multiple DSAs and tunable filters. Figure

175 shows the RF signal chains. Note that the RF signal chains

output (RF_C) is fed into the I/Q mixer.

To select the low band, RF signal chain, set Register 0x800, Bit

7, to 0 and set Register 0x801, Bits [6:5] both to 0. To select the

high band, RF signal chain, set Register 0x800, Bit 7, to 1 and set

Figure 175. RF Signal Chain Diagram

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