Support HpW-Works.com wrote: > Bruce, > > >>> There's no evidence of a cross power spectrum function in this suite. >>> One needs to be able to average at least 10,000 cross power spectra for some >>> applications. >>> > In the PSD (power density)& PSP (power spectrum) there are cross power and cross > power complex average implemented (selectable using the spectrum channel mixer)! > Additional to this you may apply / add averaging of the resulting spectrum or use > additional peak hold. > > Average of 10'000 cross points is a large count and often seen on 1-4k sample size. > Better in my opinion is to use a higher sample size 32k-64k and then less averaging > is required. > The equivalent phase noise (measured in dBc/Hz) is essentially independent of the sample size. So increasing the sample size isnt particularly useful for reducing the phase noise floor. The increased frequency resolution achieved by increasing the sample size is only useful for measuring spurs. In the direct digital method of measuring phase noise a few terasamples (a few gigasamples at baseband) need to be processed to achieve a sufficiently low instrument noise floor. However with a sound card plus a mixer a somewhat lower number of samples should suffice since there is no carrier. > Just download the evaluation version with fully feature set. > > HpW > > > Bruce

Bruce Griffiths schrieb: > Support HpW-Works.com wrote: >> Bruce, >> >>>> There's no evidence of a cross power spectrum function in this suite. >>>> One needs to be able to average at least 10,000 cross power spectra >>>> for some >>>> applications. >> In the PSD (power density)& PSP (power spectrum) there are cross >> power and cross >> power complex average implemented (selectable using the spectrum >> channel mixer)! >> Additional to this you may apply / add averaging of the resulting >> spectrum or use >> additional peak hold. >> >> Average of 10'000 cross points is a large count and often seen on >> 1-4k sample size. >> Better in my opinion is to use a higher sample size 32k-64k and then >> less averaging >> is required. > The equivalent phase noise (measured in dBc/Hz) is essentially > independent of the sample size. > So increasing the sample size isnt particularly useful for reducing > the phase noise floor. > The increased frequency resolution achieved by increasing the sample > size is only useful for measuring spurs. > In the direct digital method of measuring phase noise a few > terasamples (a few gigasamples at baseband) need to be processed to > achieve a sufficiently low instrument noise floor. > However with a sound card plus a mixer a somewhat lower number of > samples should suffice since there is no carrier. >> Just download the evaluation version with fully feature set. >> >> HpW >> >> > Bruce > > A HP/Agilent VEE based solution would be much more flexible. There is a sound card driver available. I just didn't get deep enough into digital signal processing before the 3562A came... Adrian > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

Hi Bruce, >> The equivalent phase noise (measured in dBc/Hz) is essentially independent of >> the sample size. The dBc/Hz normalization is based on this (also the sample rate). While the sample rate & sample size = FFT Bin size (resolution or filter band width) is used to get the required correction factor of the spectrum to get the dBc / (1Hz) Y scaling back. >> So increasing the sample size isnt particularly useful for reducing the phase >> noise floor. By theory, yes... but we use a sound card with a lot of flicker noise on the lower end, also we have the 10...20Hz low freq. cutoff due the usage of a servo / single 5V power. Also the raising noise below 100Hz (ADC serve & noise on the ADC power / input circuit) limits the performance. In my simple test increase of the sample size reduced the noise floor in better way than just using sample size with 1-2K and large averaging cycles. Keep in mind, Bin resolution is sample rate / sample size: Example: - 32khz / 32678 = about 1Hz - 32khz / 1024 = about 31 Hz >> However with a sound card plus a mixer a somewhat lower number of samples >> should suffice since there is no carrier. Ideally the input circuit & ADC of the 3562A would be nice but with much larger RAM buffer and ASIO interface O:) Hanspeter >> -----Original Message----- >> From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf >> Of Bruce Griffiths >> Sent: Dienstag, 27. November 2012 12:31 >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Best phase detector / mixer for 100MHz? >> >> Support HpW-Works.com wrote: >> > Bruce, >> > >> > >> >>> There's no evidence of a cross power spectrum function in this suite. >> >>> One needs to be able to average at least 10,000 cross power spectra >> >>> for some applications. >> >>> >> > In the PSD (power density)& PSP (power spectrum) there are cross >> > power and cross power complex average implemented (selectable using the >> spectrum channel mixer)! >> > Additional to this you may apply / add averaging of the resulting >> > spectrum or use additional peak hold. >> > >> > Average of 10'000 cross points is a large count and often seen on 1-4k >> sample size. >> > Better in my opinion is to use a higher sample size 32k-64k and then >> > less averaging is required. >> > >> The equivalent phase noise (measured in dBc/Hz) is essentially independent of >> the sample size. >> So increasing the sample size isnt particularly useful for reducing the phase >> noise floor. >> The increased frequency resolution achieved by increasing the sample size is >> only useful for measuring spurs. >> In the direct digital method of measuring phase noise a few terasamples (a few >> gigasamples at baseband) need to be processed to achieve a sufficiently low >> instrument noise floor. >> However with a sound card plus a mixer a somewhat lower number of samples >> should suffice since there is no carrier. >> > Just download the evaluation version with fully feature set. >> > >> > HpW >> > >> > >> > >> Bruce >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there.

Support HpW-Works.com wrote: > Hi Bruce, > > >>> The equivalent phase noise (measured in dBc/Hz) is essentially independent of >>> the sample size. >>> > The dBc/Hz normalization is based on this (also the sample rate). While the sample > rate& sample size = FFT Bin size (resolution or filter band width) is used to get > the required correction factor of the spectrum to get the dBc / (1Hz) Y scaling > back. > > >>> So increasing the sample size isnt particularly useful for reducing the phase >>> noise floor. >>> > By theory, yes... but we use a sound card with a lot of flicker noise on the lower > end, also we have the 10...20Hz low freq. cutoff due the usage of a servo / single > 5V power. Also the raising noise below 100Hz (ADC serve& noise on the ADC power / > input circuit) limits the performance. > > In my simple test increase of the sample size reduced the noise floor in better way > than just using sample size with 1-2K and large averaging cycles. > > Keep in mind, Bin resolution is sample rate / sample size: > > Example: > > - 32khz / 32678 = about 1Hz > - 32khz / 1024 = about 31 Hz > Your sample sizes are far too small to be particularly useful in measuring phase noise down to offsets of 1-10Hz or so, Phase noise is highly coloured at such offsets necessitating the use of bin sizes substantially smaller than the lowest offset frequency of interest. However decreasing the bin size beyond a small fraction of the lowest frequency of interest is counter productive in that one forgoes the effect of averaging to reduce the variance of the noise signal power within each bin. There is a NIST paper on the effect of equivalent filter bandwidth on the accuracy of coloured noise measurements. Indeed one can break the frequency range into a set of bands, the higher frequency bands having larger bin sizes and greater averaging and hence (lower bin noise signal power variance) than the lower frequency bands. However for the purposes of spur identification using as small a bin size as possible can be useful. > > >>> However with a sound card plus a mixer a somewhat lower number of samples >>> should suffice since there is no carrier. >>> > > Ideally the input circuit& ADC of the 3562A would be nice but with much larger RAM > buffer and ASIO interface O:) > > Hanspeter > > Using a high end PC should allow real time signal processing with 200ksps or greater, this is certainly the case for some external USB instruments. Bruce

Hi Would be nice to use something like the ADS1278. http://www.ti.com/product/ads1278 Lots of channels to cross correlate, and very little flicker noise. Bob On Nov 28, 2012, at 9:29 AM, Support HpW-Works.com <support@hpw-works.com> wrote: > Hi Bruce, > >>> The equivalent phase noise (measured in dBc/Hz) is essentially independent of >>> the sample size. > > The dBc/Hz normalization is based on this (also the sample rate). While the sample > rate & sample size = FFT Bin size (resolution or filter band width) is used to get > the required correction factor of the spectrum to get the dBc / (1Hz) Y scaling > back. > >>> So increasing the sample size isnt particularly useful for reducing the phase >>> noise floor. > > By theory, yes... but we use a sound card with a lot of flicker noise on the lower > end, also we have the 10...20Hz low freq. cutoff due the usage of a servo / single > 5V power. Also the raising noise below 100Hz (ADC serve & noise on the ADC power / > input circuit) limits the performance. > > In my simple test increase of the sample size reduced the noise floor in better way > than just using sample size with 1-2K and large averaging cycles. > > Keep in mind, Bin resolution is sample rate / sample size: > > Example: > > - 32khz / 32678 = about 1Hz > - 32khz / 1024 = about 31 Hz > > >>> However with a sound card plus a mixer a somewhat lower number of samples >>> should suffice since there is no carrier. > > > Ideally the input circuit & ADC of the 3562A would be nice but with much larger RAM > buffer and ASIO interface O:) > > Hanspeter > >>> -----Original Message----- >>> From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf >>> Of Bruce Griffiths >>> Sent: Dienstag, 27. November 2012 12:31 >>> To: Discussion of precise time and frequency measurement >>> Subject: Re: [time-nuts] Best phase detector / mixer for 100MHz? >>> >>> Support HpW-Works.com wrote: >>>> Bruce, >>>> >>>> >>>>>> There's no evidence of a cross power spectrum function in this suite. >>>>>> One needs to be able to average at least 10,000 cross power spectra >>>>>> for some applications. >>>>>> >>>> In the PSD (power density)& PSP (power spectrum) there are cross >>>> power and cross power complex average implemented (selectable using the >>> spectrum channel mixer)! >>>> Additional to this you may apply / add averaging of the resulting >>>> spectrum or use additional peak hold. >>>> >>>> Average of 10'000 cross points is a large count and often seen on 1-4k >>> sample size. >>>> Better in my opinion is to use a higher sample size 32k-64k and then >>>> less averaging is required. >>>> >>> The equivalent phase noise (measured in dBc/Hz) is essentially independent of >>> the sample size. >>> So increasing the sample size isnt particularly useful for reducing the phase >>> noise floor. >>> The increased frequency resolution achieved by increasing the sample size is >>> only useful for measuring spurs. >>> In the direct digital method of measuring phase noise a few terasamples (a few >>> gigasamples at baseband) need to be processed to achieve a sufficiently low >>> instrument noise floor. >>> However with a sound card plus a mixer a somewhat lower number of samples >>> should suffice since there is no carrier. >>>> Just download the evaluation version with fully feature set. >>>> >>>> HpW >>>> >>>> >>>> >>> Bruce >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.