Budgeting Resolver Excitation Phase Through Driver, Cable, and Filters

A resolver interface can have correct signal amplitudes yet exceed the phase relationship supported by its resolver-to-digital converter. Excitation drivers, the resolver, cable, and input filters all contribute. Review the complete path instead of assigning the entire allowable phase shift to one component.

Identify the reference and returned signals

The Analog Devices AD2S1210 data sheet specifies a phase lock range for the relationship between excitation and returned sine and cosine signals. It also provides fault information related to phase and tracking conditions.

Use the exact converter configuration and operating frequency. Its resolution setting, reference generation, and supported tracking behavior belong in the interface record rather than being treated as unrelated firmware details.

Build a phase contribution map

List the excitation output, power driver, any output filter, resolver winding behavior, cable, input attenuation, and input filters. Determine how the phase relationship changes across the intended excitation frequency and component variation.

Keep amplitude and phase requirements separate. A filter can provide acceptable carrier amplitude while adding enough phase lag to reduce the remaining margin. Likewise, matching only the nominal corner frequencies of the sine and cosine channels does not prove matched phase under all conditions.

Measure at defined points

Capture excitation at the relevant reference point and the returned signals at the converter inputs. Account for probe and channel timing differences. Choose a shaft position where the observed channel has sufficient amplitude for a reliable phase measurement.

Near a sine or cosine null, noise can dominate its apparent phase. Compare measurements at several positions and use the converter manufacturer’s guidance for interpreting the carrier relationship.

Verify static and moving operation

Check stationary angle accuracy and then representative speed and acceleration. Monitor phase, amplitude, loss-of-signal, and tracking indications as applicable. A static angle reading does not establish dynamic tracking performance.

Repeat with the intended cable and temperature conditions. If a filter or excitation amplifier changes, remeasure the total phase relationship rather than assuming the component’s individual bandwidth is sufficient.

Save path contributions, reference points, excitation settings, signal amplitudes, phase measurements, and dynamic results. A satisfactory interface remains inside the converter’s supported operating region with a documented margin. It does not equate a plausible angle at one shaft position with a complete validation of excitation phase, sine and cosine matching, and motion tracking throughout the assembled system’s operating range. Keep the cable length and filter component revision alongside each phase measurement so later changes remain traceable.