2014-11-24 03:52 AM
Hello,
I built a system using a ad converter (PCM4202 from TI) and a sta311b DSP. I drive the power fets with the ffx pwm stage of the sta311b. When I measure the phase response of the hole system (without any dsp settings) I get a very bad phase plot. Is it possible to correct the phase with the speaker tune option? Can I measure the Phase and generate a speaker response file like I would do with a mems microphone? Thanks in advance.2014-11-25 03:26 AM
I'm unsure about the root cause of your bad phase plot but it will arguably depends on the overall system architecture (including ADC and power FETs). You could try to optimized the response by measuring it and compensating with STA311B embedded filtering stages but I would first try to understand what's the real culprit of your bad response. Also, STSpeakerTune technology is more to compensate the frequency response, not the phase - a new topic on this subject has just been posted highlighting how to quickly assess the feature.
Marco2014-11-26 01:04 AM
Hello Marco,
thanks a lot for your fast reply. So I measured the phase just above the adc and sta311b. The adc (pcm4202 from ti) has a very low phase marging, nearly zero. I know it from other projects. The phase response over the fet stage and lc filter is 8° max. So that's ok. Now some screenshots form my rohde&schwarz upl system: First: STA311b with dsp bypassed, Input driven with 96kHz 24bit I2S 256fshttp://www.mikrocontroller.net/attachment/238173/Phase_AnalogIn-AMP_out.jpg
Second: STA311b with dsp bypassed, Input driven with 192kHz 24bit I2S 128fshttp://www.mikrocontroller.net/attachment/238180/Phase_192khz.jpg
In 192kHz mode the phase over the sta311 looks much better but still not linear. Do you have any idea? Do you have a phase plot from your labor? Thanks, Bernhard2014-12-03 12:25 AM
Hi Marco,
can you say anything about my Phase plots? Do you have a Phase plot over the sta311b from your lab? Regards Bernhard2014-12-03 05:01 PM
Hi Bernhard ,
the group delay of STA311B is around 0.53mS @ 48Khz FS , so if you increaed sample frequency , the delay will be reduced . Thanks2014-12-05 11:46 AM
Hi Zhao,
Group delay should have no influence to the phase delay... Have you looked at the screens I added in my previous post? You can see a high phase delay and yes the delay gets better with higher sampling rate but still not acceptable even with 192kHz. Can you make a phase plot in your lab? Thanks again Bernhard2014-12-09 07:38 PM
hi bernhard,
plesae find phase shift plot in attachment. if the x aixs had been divieded in linear, you can find the phase shift period was fixed , measns a constant delay timingcaused this shift. Thanks ________________ Attachments : phase_shift_linear_.emf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Ht1Z&d=%2Fa%2F0X0000000aIw%2FcoNdk5JoJO0ESnLXRlKODLsyURWytDKps4fXEcSM.Es&asPdf=falsephase_shift_log.emf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Ht1e&d=%2Fa%2F0X0000000aIx%2FUBBsWAb24OdLdoW.0yIaenRY4_WJuEU_tfdoA._vfIE&asPdf=false