we are trying to measure the noise figure for our receiver, but seems the receiver output noise power is too low to measure. Here is the receiver configuration: RF+ADC+DDC(digital down converter) the total RF gain is 40dB(that is the maximum gain we can get), and the RF noise figure is about 5dB the ADC is 14 bit the DDC decimation rate is about 1600, and the dynamic range is 90dB. Here is our problem the receiver input noise power is -174dBm/Hz after RF the noise power becomes -174dBm/Hz+40dB+5dB=-139dBm/Hz. the bandwidth is about 30MHz so after ADC we get around +-40 counts. but then since the DDC has a huge reduce to the bandwidth, after DDC the noise due to the analog device is too small to show on the spectrum. Here is my question: 1. when we talk about noise figure for a digital receiver, it is the RF+ADC, or the DDC will also contribute to the noise figure even though it is all digital? If DDC contributes, in what manner? 2. the noise floor at the DDC output is too low to see, is there any other experiment setup method that I can get around this? 3. we can cascade two RF to increase the gain, but then the measurement become the noise figure for RF+RF+ADC+DDC, from this measurement how can I estimate the actual receiver noise figure? Thanks a lot.
Noise figure measurement
Started by ●March 31, 2009
Reply by ●March 31, 20092009-03-31
gobruins wrote:> 1. when we talk about noise figure for a digital receiver, it is the > RF+ADC, or the DDC will also contribute to the noise figure even though it > is all digital? If DDC contributes, in what manner?When you talk about noise figure, you mean the SNR impairment due to whatever reasons. Let's say your system needs the minimal signal of X to operate normally, whereas the theoretical limit is Y. The noise figure is X/Y.> 2. the noise floor at the DDC output is too low to see, is there any other > experiment setup method that I can get around this?If you can't see the noise floor after the DDC, that means your sensitivity is limited by DDC, not by RF part. Setup the DDC properly.> 3. we can cascade two RF to increase the gain, but then the measurement > become the noise figure for RF+RF+ADC+DDC, from this measurement how can I > estimate the actual receiver noise figure?The question does not make sense. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Reply by ●March 31, 20092009-03-31
'theoretical limit is Y', how can I compute this number?> >gobruins wrote: > >> 1. when we talk about noise figure for a digital receiver, it is the >> RF+ADC, or the DDC will also contribute to the noise figure even thoughit>> is all digital? If DDC contributes, in what manner? > >When you talk about noise figure, you mean the SNR impairment due to >whatever reasons. Let's say your system needs the minimal signal of X to>operate normally, whereas the theoretical limit is Y. The noise figure >is X/Y. > > >> 2. the noise floor at the DDC output is too low to see, is there anyother>> experiment setup method that I can get around this? > >If you can't see the noise floor after the DDC, that means your >sensitivity is limited by DDC, not by RF part. Setup the DDC properly. > >> 3. we can cascade two RF to increase the gain, but then themeasurement>> become the noise figure for RF+RF+ADC+DDC, from this measurement howcan I>> estimate the actual receiver noise figure? > >The question does not make sense. > > >Vladimir Vassilevsky >DSP and Mixed Signal Design Consultant >http://www.abvolt.com >
Reply by ●March 31, 20092009-03-31
'theoretical limit is Y', how can I compute this number?> >gobruins wrote: > >> 1. when we talk about noise figure for a digital receiver, it is the >> RF+ADC, or the DDC will also contribute to the noise figure even thoughit>> is all digital? If DDC contributes, in what manner? > >When you talk about noise figure, you mean the SNR impairment due to >whatever reasons. Let's say your system needs the minimal signal of X to>operate normally, whereas the theoretical limit is Y. The noise figure >is X/Y. > > >> 2. the noise floor at the DDC output is too low to see, is there anyother>> experiment setup method that I can get around this? > >If you can't see the noise floor after the DDC, that means your >sensitivity is limited by DDC, not by RF part. Setup the DDC properly. > >> 3. we can cascade two RF to increase the gain, but then themeasurement>> become the noise figure for RF+RF+ADC+DDC, from this measurement howcan I>> estimate the actual receiver noise figure? > >The question does not make sense. > > >Vladimir Vassilevsky >DSP and Mixed Signal Design Consultant >http://www.abvolt.com >
Reply by ●March 31, 20092009-03-31
You don't have to. Just pay money. VLV gobruins wrote:> 'theoretical limit is Y', how can I compute this number? > > > > >>gobruins wrote: >> >> >>>1. when we talk about noise figure for a digital receiver, it is the >>>RF+ADC, or the DDC will also contribute to the noise figure even though > > it > >>>is all digital? If DDC contributes, in what manner? >> >>When you talk about noise figure, you mean the SNR impairment due to >>whatever reasons. Let's say your system needs the minimal signal of X to > > >>operate normally, whereas the theoretical limit is Y. The noise figure >>is X/Y. >> >> >> >>>2. the noise floor at the DDC output is too low to see, is there any > > other > >>>experiment setup method that I can get around this? >> >>If you can't see the noise floor after the DDC, that means your >>sensitivity is limited by DDC, not by RF part. Setup the DDC properly. >> >> >>>3. we can cascade two RF to increase the gain, but then the > > measurement > >>>become the noise figure for RF+RF+ADC+DDC, from this measurement how > > can I > >>>estimate the actual receiver noise figure? >> >>The question does not make sense. >> >> >>Vladimir Vassilevsky >>DSP and Mixed Signal Design Consultant >>http://www.abvolt.com >> > > > > > >
Reply by ●March 31, 20092009-03-31
On Mar 31, 11:42�am, "gobruins" <chunmei.k...@gmail.com> wrote:> we are trying to measure the noise figure for our receiver, but seems the > receiver output noise power is too low to measure. > > Here is the receiver configuration: RF+ADC+DDC(digital down converter) > the total RF gain is 40dB(that is the maximum gain we can get), and the RF > noise figure is about 5dB > the ADC is 14 bit > the DDC decimation rate is about 1600, and the dynamic range is 90dB. > > Here is our problem > the receiver input noise power is -174dBm/Hz > after RF the noise power becomes -174dBm/Hz+40dB+5dB=-139dBm/Hz. > the bandwidth is about 30MHz > so after ADC we get around +-40 counts. > but then since the DDC has a huge reduce to the bandwidth, after DDC the > noise due to the analog device is too small to show on the spectrum. > > Here is my question: > 1. when we talk about noise figure for a digital receiver, it is the > RF+ADC, or the DDC will also contribute to the noise figure even though it > is all digital? If DDC contributes, in what manner? > > 2. the noise floor at the DDC output is too low to see, is there any other > experiment setup method that I can get around this? > > 3. we can cascade two RF to increase the gain, but then the measurement > become the noise figure for RF+RF+ADC+DDC, from this measurement how can I > estimate the actual receiver noise figure? > > Thanks a lot.You need to feed a calibrated noise level into your system, rather than relying on kTB. See this app note (Y-factor method): http://www.maxim-ic.com/appnotes.cfm/an_pk/2875 John
Reply by ●March 31, 20092009-03-31
To use the Y-factor method, when turning the noise source power off, isn't the input noise power still KTB? In that way we still can not read it at the DDC output. Also another issue is that we do not have analogue output, we only have recorded digital data. So once it is below the minimum voltage level, our receiver can not pick up the noise.>On Mar 31, 11:42=A0am, "gobruins" <chunmei.k...@gmail.com> wrote: >> we are trying to measure the noise figure for our receiver, but seemsthe>> receiver output noise power is too low to measure. >> >> Here is the receiver configuration: RF+ADC+DDC(digital down converter) >> the total RF gain is 40dB(that is the maximum gain we can get), and theR=>F >> noise figure is about 5dB >> the ADC is 14 bit >> the DDC decimation rate is about 1600, and the dynamic range is 90dB. >> >> Here is our problem >> the receiver input noise power is -174dBm/Hz >> after RF the noise power becomes -174dBm/Hz+40dB+5dB=3D-139dBm/Hz. >> the bandwidth is about 30MHz >> so after ADC we get around +-40 counts. >> but then since the DDC has a huge reduce to the bandwidth, after DDCthe>> noise due to the analog device is too small to show on the spectrum. >> >> Here is my question: >> 1. when we talk about noise figure for a digital receiver, it is the >> RF+ADC, or the DDC will also contribute to the noise figure even thoughi=>t >> is all digital? If DDC contributes, in what manner? >> >> 2. the noise floor at the DDC output is too low to see, is there anyothe=>r >> experiment setup method that I can get around this? >> >> 3. we can cascade two RF to increase the gain, but then themeasurement>> become the noise figure for RF+RF+ADC+DDC, from this measurement howcan =>I >> estimate the actual receiver noise figure? >> >> Thanks a lot. > >You need to feed a calibrated noise level into your system, rather >than relying on kTB. See this app note (Y-factor method): > >http://www.maxim-ic.com/appnotes.cfm/an_pk/2875 > >John >
Reply by ●March 31, 20092009-03-31
On Mar 31, 2:02�pm, "gobruins" <chunmei.k...@gmail.com> wrote:> To use the Y-factor method, when turning the noise source power off, isn't > the input noise power still KTB? In that way we still can not read it at > the DDC output. > Also another issue is that we do not have analogue output, we only have > recorded digital data. So once it is below the minimum voltage level, our > receiver can not pick up the noise. > > > > >On Mar 31, 11:42=A0am, "gobruins" <chunmei.k...@gmail.com> wrote: > >> we are trying to measure the noise figure for our receiver, but seems > the > >> receiver output noise power is too low to measure. > > >> Here is the receiver configuration: RF+ADC+DDC(digital down converter) > >> the total RF gain is 40dB(that is the maximum gain we can get), and the > R= > >F > >> noise figure is about 5dB > >> the ADC is 14 bit > >> the DDC decimation rate is about 1600, and the dynamic range is 90dB. > > >> Here is our problem > >> the receiver input noise power is -174dBm/Hz > >> after RF the noise power becomes -174dBm/Hz+40dB+5dB=3D-139dBm/Hz. > >> the bandwidth is about 30MHz > >> so after ADC we get around +-40 counts. > >> but then since the DDC has a huge reduce to the bandwidth, after DDC > the > >> noise due to the analog device is too small to show on the spectrum. > > >> Here is my question: > >> 1. when we talk about noise figure for a digital receiver, it is the > >> RF+ADC, or the DDC will also contribute to the noise figure even though > i= > >t > >> is all digital? If DDC contributes, in what manner? > > >> 2. the noise floor at the DDC output is too low to see, is there any > othe= > >r > >> experiment setup method that I can get around this? > > >> 3. we can cascade two RF to increase the gain, but then the > measurement > >> become the noise figure for RF+RF+ADC+DDC, from this measurement how > can = > >I > >> estimate the actual receiver noise figure? > > >> Thanks a lot. > > >You need to feed a calibrated noise level into your system, rather > >than relying on kTB. See this app note (Y-factor method): > > >http://www.maxim-ic.com/appnotes.cfm/an_pk/2875 > > >JohnYou are correct, you get kTB with power off. It will be invisible to your system. Can you capture raw ADC data and use that? Alternatively, program some digital gain into your DDC to bring the noise level up where you can see it. John
Reply by ●March 31, 20092009-03-31
To use the Y-factor method, when turning the noise source power off, isn't the input noise power still KTB? In that way we still can not read it at the DDC output. Also another issue is that we do not have analogue output, we only have recorded digital data. So once it is below the minimum voltage level, our receiver can not pick up the noise.>On Mar 31, 11:42=A0am, "gobruins" <chunmei.k...@gmail.com> wrote: >> we are trying to measure the noise figure for our receiver, but seemsthe>> receiver output noise power is too low to measure. >> >> Here is the receiver configuration: RF+ADC+DDC(digital down converter) >> the total RF gain is 40dB(that is the maximum gain we can get), and theR=>F >> noise figure is about 5dB >> the ADC is 14 bit >> the DDC decimation rate is about 1600, and the dynamic range is 90dB. >> >> Here is our problem >> the receiver input noise power is -174dBm/Hz >> after RF the noise power becomes -174dBm/Hz+40dB+5dB=3D-139dBm/Hz. >> the bandwidth is about 30MHz >> so after ADC we get around +-40 counts. >> but then since the DDC has a huge reduce to the bandwidth, after DDCthe>> noise due to the analog device is too small to show on the spectrum. >> >> Here is my question: >> 1. when we talk about noise figure for a digital receiver, it is the >> RF+ADC, or the DDC will also contribute to the noise figure even thoughi=>t >> is all digital? If DDC contributes, in what manner? >> >> 2. the noise floor at the DDC output is too low to see, is there anyothe=>r >> experiment setup method that I can get around this? >> >> 3. we can cascade two RF to increase the gain, but then themeasurement>> become the noise figure for RF+RF+ADC+DDC, from this measurement howcan =>I >> estimate the actual receiver noise figure? >> >> Thanks a lot. > >You need to feed a calibrated noise level into your system, rather >than relying on kTB. See this app note (Y-factor method): > >http://www.maxim-ic.com/appnotes.cfm/an_pk/2875 > >John >
Reply by ●March 31, 20092009-03-31
we captured some ADC raw data, but it does not show us good average noise power as we expected, still trying to figure out why. And meanwhile in the DDC we are trying to scale up the input data by 2 bits, when we load the new DDC into our receiver, we will capture some data. hopefully that will give us a nice noise floor. Thanks for your advice.>On Mar 31, 2:02=A0pm, "gobruins" <chunmei.k...@gmail.com> wrote: >> To use the Y-factor method, when turning the noise source power off,isn'=>t >> the input noise power still KTB? In that way we still can not read itat>> the DDC output. >> Also another issue is that we do not have analogue output, we onlyhave>> recorded digital data. So once it is below the minimum voltage level,our>> receiver can not pick up the noise. >> >> >> >> >On Mar 31, 11:42=3DA0am, "gobruins" <chunmei.k...@gmail.com> wrote: >> >> we are trying to measure the noise figure for our receiver, butseems>> the >> >> receiver output noise power is too low to measure. >> >> >> Here is the receiver configuration: RF+ADC+DDC(digital downconverter)>> >> the total RF gain is 40dB(that is the maximum gain we can get), andth=>e >> R=3D >> >F >> >> noise figure is about 5dB >> >> the ADC is 14 bit >> >> the DDC decimation rate is about 1600, and the dynamic range is90dB.>> >> >> Here is our problem >> >> the receiver input noise power is -174dBm/Hz >> >> after RF the noise power becomes-174dBm/Hz+40dB+5dB=3D3D-139dBm/Hz.>> >> the bandwidth is about 30MHz >> >> so after ADC we get around +-40 counts. >> >> but then since the DDC has a huge reduce to the bandwidth, afterDDC>> the >> >> noise due to the analog device is too small to show on thespectrum.>> >> >> Here is my question: >> >> 1. when we talk about noise figure for a digital receiver, it isthe>> >> RF+ADC, or the DDC will also contribute to the noise figure eventhoug=>h >> i=3D >> >t >> >> is all digital? If DDC contributes, in what manner? >> >> >> 2. the noise floor at the DDC output is too low to see, is thereany>> othe=3D >> >r >> >> experiment setup method that I can get around this? >> >> >> 3. we can cascade two RF to increase the gain, but then the >> measurement >> >> become the noise figure for RF+RF+ADC+DDC, from this measurementhow>> can =3D >> >I >> >> estimate the actual receiver noise figure? >> >> >> Thanks a lot. >> >> >You need to feed a calibrated noise level into your system, rather >> >than relying on kTB. See this app note (Y-factor method): >> >> >http://www.maxim-ic.com/appnotes.cfm/an_pk/2875 >> >> >John > >You are correct, you get kTB with power off. It will be invisible to >your system. Can you capture raw ADC data and use that? Alternatively, >program some digital gain into your DDC to bring the noise level up >where you can see it. > >John >
