240 N5511A Phase Noise Test System User’s GuideFM Discriminator Measurement ExamplesFM Discriminator Single Channel Measurement using FM Rate and DeviationCalibrationFM Discriminator Single Channel Measurement using FM Rate andDeviation CalibrationRequired EquipmentTable 10-3 shows equipment required for this example in addition to the phasenoise test system and your DUT.Determining the discriminator (delay line) lengthPerform the following steps to determine the minimum delay line length (τ)possible to provide an adequate noise to measure the source.1. Determine the delay necessary to provide a discriminator noise floor thatis below the expected noise level of the DUT. Figure 10-11 shows the noisefloor of the discriminator for given delay times (t).2. Determine the length of coax required to provide the necessary delay (τ).(Eight feet of BNC cable will provide 12 ns of delay for this example.)3. Determine the loss in the delay line. Verify that the signal source will beable to provide a power level at the output of the delay line of between +5and +17 ICBM. Be sure to take into account an additional 4 to 6 dB of lossTo prevent damage to the test set’s components, do not apply a signal beyond the systemsspecifications. Refer to the data sheet for power specifications.In order to use the FM rate and deviation calibration method you must have a signal source that iscalibrated for FM modulation rate and FM deviation parameters. All Keysight Technologies signalgenerators meet this requirement.To ensure accurate measurements allow the DUT and measurement equipment to warm up atleast 30 minutes before making the noise measurement.Table 10-3 Required Equipment for the FM DiscriminatorMeasurement ExampleEquipment Quantity CommentsSignal Generator 1 +19 dBm output level at tested carrier frequency.Calibrated FM at a 20 kHz rate with 10 kHz PeakDeviation.Power Splitter 1 NARDA 30183Delay Line Delay (or length) adequate to decorrelate source noise.Phase Shifter 1 ±180° phase shifter at lowest carrier frequency tested.
