DCFM Frequency Offset

DC FM Carrier Offset is a measure of carrier-frequency shift due to residual DC on the ESG’s EXT1 DC -coupled path when FM mode is selected. Any DC level in this path will cause a constant offset (deviation) in the CW frequency.

For this test, the ESG is set to a selected carrier frequency and FM is enabled. The EXT 1 input is selected and left open. A specific value of FM deviation is selected and a DC FM calibration is executed.

For FM ON and FM OFF, the carrier frequency is measured with a frequency counter. Any shift in the carrier frequency must be due to a residual DC voltage somewhere in the EXT 1 input path.

Required Test Equipment

Instrument

Critical Specifications for This Test

Recommended Model1

Frequency Counter

Frequency Resolution ≥ 0.1 Hz at 1 GHz

53230A Opt [106 or 115]
  1. Refer to the main equipment list for alternate models.

Connections and Setup Procedures
  • All test equipment requires a 30 minute warm-up period to ensure accurate performance.
  • In the following test setup, direct cable and adapter connections are designated as solid lines. Changeable cable and adapter connections are designated as dashed lines.
  • Connect all test equipment as shown.
  • Connect GPIB cables to all GPIB-controlled test equipment.
  • While performing this test, follow all instructions on the controller display.