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PHASE NOISE MEAS. AND THE 89441A Step-by-Step Instructions of One Example DUT: 3325A synthesizer/function generator Measurement frequency 10.7 MHz, Amplitude: 1.5 dBm, Not phase-locked to HP 89441A For comparison, all measurements will be made at a 10 kHz offset from the carrier. 89441A key presses follow the text and are shown as: [Hardkey] [softkey] Note: Softkey labels may change slightly due to option configuration. 89441A Setup RF Vector Mode, Center Frequency = 10.7 MHz, Span = 39.0625 kHz. Use the Counter to accurately measure the carrier frequency and to set the center frequency of the analyzer. Turn the Counter function off when finished (to speed up measurements). Span is selected to be at least twice the desired max offset of 10 kHz, and a cardinal span of 10 MHz/2n is chosen to speed averaging. Maximum speed is achieved with the analyzer's maximum number of frequency points (System Utility) equal to the number of points actually selected (ResBW/Window), channel 2 turned off, and calculations on unused traces turned off. [Preset] [receiver] [RF (2-2650 MHz)] [RF (2-2650 MHz) normal] [Instrument Mode] [Vector] [Frequency] [center] 10.7 [MHz] [span] 39.0625 [kHz] [Marker Function] [freq counter on] [Shift] [Mkr > Peak] [Shift] [Mkr > CF] [freq counter off] Set the input range to the lowest value which does not cause the OV1 (overload channel 1) annunciator to appear in the display. Using the most sensitive input range possible reduces the noise contribution of the analyzer to the measurement. In some cases a measurement with a modest overrange will work well because small amounts of distortion due to overrange do not affect the measurement. For more details press Help, Range, ch1 range. [Range] [ch1 range] use the up and down arrow keys to adjust the range An auto zero should be performed after we've touched the ADC overload (OV1) region. This clears out potential bad data from the ADC loop. If a CAL is performed (see the step immediately below), this auto zero will be performed automatically. It is useful to make sure the analyzer is up to a stable temperature and do a CAL at this point. Stable temperature and lack of cal (or other relay) activity provides for most consistent operation of noise subtraction. Disable auto calibration (which might affect noise subtraction) but do not be concerned with auto-zero operations performed during the measurement. [System Utility] [single cal] [auto cal off] Select RBW Auto/Arb, with # points = 801 This is a useful default for reasons of frequency resolution and update/average rate. RBW can be set in Fixed mode to more round-number values to make noise bandwidth corrections easier (see example below). # points can be increased for greater frequency resolution at small offsets. RBW filter type can be changed to Gaussian for greater frequency resolution at sm