ADL5960ACCZ-R2 datasheet(18/32 Pages) AD

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Data Sheet

ADL5960

THEORY OF OPERATION

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Rev. A | 18 of 32

Phase synchronization between the ADL5960 devices is achieved

through the LO and offset frequency signals. For optimal accuracy,

it is preferable to match the propagation delays from the LO source

to each of the ADL5960 devices. Residual delay differences can

be addressed through calibration procedures for the VNA system.

Routing of the signal lines to the offset interface is less critical,

because these operate at much lower frequencies.

The SYNC interface is used to force the LO and offset dividers

in all ADL5960 devices to the same known initial state, such that

no phase ambiguities exist between the devices. A single pulse

applied to this input after power-on is sufficient to synchronize

all devices. Perform this synchronization before an LO signal is

applied. In that case the timing of the SYNC pulse is not critical.

For the optimal accuracy, simultaneous sampling of all ADL5960

IF channels is recommended. For high port counts, a multichannel

simultaneous sampling ADC can significantly reduce the solution

footprint. Some of these multichannel devices include built-in digital

downconversion (DDC) and decimation filters, which reduce the

amount of processing required in the digital signal processor (DSP).

The performance of the system can further be enhanced by insert-

ing a programmable RF filter in the RF path to filter any harmonic

content of the RF source, and a programmable attenuator to com-

pensate for tilt vs. frequency introduced by filters, switches, and

transmission lines.

Figure 54. Multiport Vector Network Analyzer Based on the ADL5960

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