Agilent Technologies HP 8642A/B Specifiche Scaricare il pdf (Pagina 401)

Table 8-1. Numbered Error Messages (5 of 17)

(cont'd)

Large Spur on Input Signal

A sharp peak on an otherwise correct loop suppression curve is evidence of a large spur

(typically > —40 dBc) near the phase lock loop (PLL) bandwidth of the measurement {within

a factor of two). Press Proceed to continue with the measurement. The measurement results

may not be totally accurate but the noise graph will provide you with the offset frequency and

approximate level of the spur. (Chapter 6 Evaluating Measurement Results in the HP 3048A

Operating Manual, provides information that will help you isolate the spur source).

If you are not able to reduce the spur level to < —40 dBc, it may be possible to make an

accurate noise measurement by changing the PLL bandwidth. Measurement accuracy is only

affected by spurs > -40 dBc that are within a factor of 2 of the PLL bandwidth.

The PLL bandwidth is shown as a function of Peak Tuning Range (PTR) in Figure 8-2. (The

PTR for the measurement is determined by multiplying the VCO's Tuning Constant by the

VCO's Voltage Tuning Range entered for the measurement. For further information about

changing the PTR, refer to Changing the PTR in Chapter 3 of the Operating Manual.

3. High Noise on Input Signal

NOTE

Be sure that SOURCE OUT on the rear panel of the HP 3561A is connected

to NOISE INPUT on the rear panel of the HP 11848A. If these ports are

not connected, connect them now, press the Retry softkey.

A noisy loop suppression curve is caused when one or both of the input signals has noise

near the small angle line at offsets near the phase lock loop (PLL) bandwidth. For information

about verifying the noise level and recommended actions for compensating for a high noise

level,

refer to Evaluating Noise Above the Small Angle Line in

Chapter 3 of the Operating Manual.

Unable to detect the presence of a beatnote.

Action:

Check to be sure that the correct Phase Detector is selected in the Inst. Params menu.

Check sources to verify the frequency of each output signal.

3. Check for a beatnote. (A procedure for tuning the beatnote to within the Capture Range

for the measurement is provided in the Checking the Beatnote section of each Phase

Lock Loop measurement example in Chapter 3 of the Operating Manual. An oscilloscope

connected to the HP 11848A AUX MONITOR port can be helpful for monitoring and

zeroing the beatnote.)

The sources must be within 50 kHz (20 MHz with an RF analyzer) of each other to allow

the system to function correctly.

8-6 Numbered Error Messages rev.05SEP89

1 2 ... 396 397 398 399 400 401 402 403 404 405 406 ... 452 453

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Agilent Technologies HP 8642A/B Specifiche Pagina 401