I think that the term dynamic range of a receiver is one of the most confusing specs when talking about receiver performance. What does the term mean to you? My problem is that many times I see receivers that have a wide "static" range due to a front end attenuator that can be varied, but that does not seem to be what dynamic range is about. It seems to me that dynamic range is about the ability to discriminate two levels coming into the receiver (both in the IF "desirable" signal passband) at the same time. Any thoughts? Brent
Dynamic Range of Receiver
Started by ●October 10, 2010
Reply by ●October 10, 20102010-10-10
On 10/10/2010 01:41 PM, brent wrote:> I think that the term dynamic range of a receiver is one of the most > confusing specs when talking about receiver performance. What does > the term mean to you? > > My problem is that many times I see receivers that have a wide > "static" range due to a front end attenuator that can be varied, but > that does not seem to be what dynamic range is about. It seems to me > that dynamic range is about the ability to discriminate two levels > coming into the receiver (both in the IF "desirable" signal passband) > at the same time. > > Any thoughts?Different services have different definitions, and manufacturers will always try to jerk you around. Even within a service there are multiple definition -- 3rd-order IM dynamic range, image rejection, etc. You just need to understand the issues, and ask the right questions. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by ●October 10, 20102010-10-10
On 10/10/2010 1:41 PM, brent wrote:> I think that the term dynamic range of a receiver is one of the most > confusing specs when talking about receiver performance. What does > the term mean to you? > > My problem is that many times I see receivers that have a wide > "static" range due to a front end attenuator that can be varied, but > that does not seem to be what dynamic range is about. It seems to me > that dynamic range is about the ability to discriminate two levels > coming into the receiver (both in the IF "desirable" signal passband) > at the same time. > > Any thoughts? > > BrentIt's been a long time .... but I would think of dynamic range being determined by the noise level for the floor and the clipping level at the peak. The ability to discriminate two signals I believe is "selectivity". Fred
Reply by ●October 10, 20102010-10-10
On 10/10/2010 05:24 PM, Fred Marshall wrote:> On 10/10/2010 1:41 PM, brent wrote: >> I think that the term dynamic range of a receiver is one of the most >> confusing specs when talking about receiver performance. What does >> the term mean to you? >> >> My problem is that many times I see receivers that have a wide >> "static" range due to a front end attenuator that can be varied, but >> that does not seem to be what dynamic range is about. It seems to me >> that dynamic range is about the ability to discriminate two levels >> coming into the receiver (both in the IF "desirable" signal passband) >> at the same time. >> >> Any thoughts? >> >> Brent > > It's been a long time .... but I would think of dynamic range being > determined by the noise level for the floor and the clipping level at > the peak. > The ability to discriminate two signals I believe is "selectivity".Dynamic range can also be defined as the noise floor vs. the strength of a pair of off-frequency signals necessary to bring the third-order intermodulation products up to the noise floor. IIRC analog CATV amps were specified as the noise floor vs. the strength of _many_ off-frequency signals. So there are lots of different "dynamic ranges". -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by ●October 10, 20102010-10-10
On Oct 10, 4:41�pm, brent <buleg...@columbus.rr.com> wrote:> I think that the term dynamic range of a receiver is one of the most > confusing specs when talking about receiver performance. �What does > the term mean to you? > > My problem is that many times I see receivers that have a wide > "static" range due to a front end attenuator that can be varied, but > that does not seem to be what dynamic range is about. �It seems to me > that dynamic range is about the ability to discriminate two levels > coming into the receiver (both in the IF "desirable" signal passband) > at the same time. > > Any thoughts? > > BrentBrent, you are correct the term is ambiguous and I have seen misunderstandings before... the AGC can allow the __desired signal___ dynamic range to be very wide... but as you say.. that tells nothing about the ability of the Rx to Rx a weak desired signal despite a strong nearby interferer.. I have seen the term ___instantaneous___ dynamic range used to describe that. I think the best way to avoid confusion is to create a spec in terms of use case, i.e. be able to Rx a 1uV signal with 2 50 mV signals in the first and second adj channel etc... these are sometimes called blockers.. Mark
Reply by ●October 11, 20102010-10-11
On Oct 10, 10:42�pm, Mark <makol...@yahoo.com> wrote:> On Oct 10, 4:41�pm, brent <buleg...@columbus.rr.com> wrote: > > > I think that the term dynamic range of a receiver is one of the most > > confusing specs when talking about receiver performance. �What does > > the term mean to you? > > > My problem is that many times I see receivers that have a wide > > "static" range due to a front end attenuator that can be varied, but > > that does not seem to be what dynamic range is about. �It seems to me > > that dynamic range is about the ability to discriminate two levels > > coming into the receiver (both in the IF "desirable" signal passband) > > at the same time. > > > Any thoughts? > > > Brent > > Brent, you are correct the term is ambiguous and I have seen > misunderstandings before... > > the AGC can allow the __desired signal___ dynamic range to be very > wide... > > but as you say.. that tells nothing about the ability of the Rx to Rx > a weak desired signal despite a strong nearby interferer.. �I have > seen the term ___instantaneous___ �dynamic range used to describe > that. > > I think the best way to avoid confusion is to create a spec in terms > of use case, i.e. be able to Rx �a 1uV signal with 2 50 mV signals in > the first and second adj channel etc... �these are sometimes called > blockers.. > > MarkThat is excellent advice. From the top level spec a potentially surprising number of lower level specs can be derived, like phase noise for example. John
Reply by ●October 11, 20102010-10-11
On Oct 11, 5:41�am, John <sampson...@gmail.com> wrote:> On Oct 10, 10:42�pm, Mark <makol...@yahoo.com> wrote: > > > > > > > On Oct 10, 4:41�pm, brent <buleg...@columbus.rr.com> wrote: > > > > I think that the term dynamic range of a receiver is one of the most > > > confusing specs when talking about receiver performance. �What does > > > the term mean to you? > > > > My problem is that many times I see receivers that have a wide > > > "static" range due to a front end attenuator that can be varied, but > > > that does not seem to be what dynamic range is about. �It seems to me > > > that dynamic range is about the ability to discriminate two levels > > > coming into the receiver (both in the IF "desirable" signal passband) > > > at the same time. > > > > Any thoughts? > > > > Brent > > > Brent, you are correct the term is ambiguous and I have seen > > misunderstandings before... > > > the AGC can allow the __desired signal___ dynamic range to be very > > wide... > > > but as you say.. that tells nothing about the ability of the Rx to Rx > > a weak desired signal despite a strong nearby interferer.. �I have > > seen the term ___instantaneous___ �dynamic range used to describe > > that. > > > I think the best way to avoid confusion is to create a spec in terms > > of use case, i.e. be able to Rx �a 1uV signal with 2 50 mV signals in > > the first and second adj channel etc... �these are sometimes called > > blockers.. > > > Mark > > That is excellent advice. From the top level spec a potentially > surprising number of lower level specs can be derived, like phase > noise for example. > > John- Hide quoted text - > > - Show quoted text -Actually dynamic range is still best described as in the classic case where the largest signals determine the top of the range that in turn create distortion products that just start to pop out of the noise floor in a given analysis bandwidth. The classic description has used two tones, (TOI), and NF. This is still a very effect description used to spec receiver design. Adjustable gain is used as a method of optimizing dynamic range. This becomes especially important when you have A/D converters in that back end that can create their own artifacts. Complex modulation schemes come with their own vernacular, but it�s a play on the above concept.
Reply by ●October 11, 20102010-10-11
On Oct 11, 10:06=A0am, jim <fiscalconsoc...@gmail.com> wrote:> On Oct 11, 5:41=A0am, John <sampson...@gmail.com> wrote: > > > > > > > On Oct 10, 10:42=A0pm, Mark <makol...@yahoo.com> wrote: > > > > On Oct 10, 4:41=A0pm, brent <buleg...@columbus.rr.com> wrote: > > > > > I think that the term dynamic range of a receiver is one of the mos=t> > > > confusing specs when talking about receiver performance. =A0What do=es> > > > the term mean to you? > > > > > My problem is that many times I see receivers that have a wide > > > > "static" range due to a front end attenuator that can be varied, bu=t> > > > that does not seem to be what dynamic range is about. =A0It seems t=o me> > > > that dynamic range is about the ability to discriminate two levels > > > > coming into the receiver (both in the IF "desirable" signal passban=d)> > > > at the same time. > > > > > Any thoughts? > > > > > Brent > > > > Brent, you are correct the term is ambiguous and I have seen > > > misunderstandings before... > > > > the AGC can allow the __desired signal___ dynamic range to be very > > > wide... > > > > but as you say.. that tells nothing about the ability of the Rx to Rx > > > a weak desired signal despite a strong nearby interferer.. =A0I have > > > seen the term ___instantaneous___ =A0dynamic range used to describe > > > that. > > > > I think the best way to avoid confusion is to create a spec in terms > > > of use case, i.e. be able to Rx =A0a 1uV signal with 2 50 mV signals =in> > > the first and second adj channel etc... =A0these are sometimes called > > > blockers.. > > > > Mark > > > That is excellent advice. From the top level spec a potentially > > surprising number of lower level specs can be derived, like phase > > noise for example. > > > John- Hide quoted text - > > > - Show quoted text - > > Actually dynamic range is still best described as in the classic case > where the largest signals determine the top of the range that in turn > create distortion products that just start to pop out of the noise > floor in a given analysis bandwidth. =A0The classic description has used > two tones, (TOI), and NF. =A0This is still a very effect description > used to spec receiver design. > > Adjustable gain is used as a method of optimizing dynamic range. =A0This > becomes especially important when you have A/D converters in that back > end that can create their own artifacts. > > Complex modulation schemes come with their own vernacular, but it=92s a > play on the above concept.- Hide quoted text - > > - Show quoted text -Another issue to keep in mind is that out of band signals can certainly =93wad-up=94 the front end, thus making any in band measurements useless. But having said that, most applications have a predetermined environment of use, and prefiltering may have to be employed. The importance of describing the application and setting systems specs can not be over stated if the goal is a positive out come on a receiver project.
Reply by ●October 11, 20102010-10-11
On 10/11/2010 10:19 AM, jim wrote:> On Oct 11, 10:06 am, jim<fiscalconsoc...@gmail.com> wrote: >> On Oct 11, 5:41 am, John<sampson...@gmail.com> wrote: >> >> >> >> >> >>> On Oct 10, 10:42 pm, Mark<makol...@yahoo.com> wrote: >> >>>> On Oct 10, 4:41 pm, brent<buleg...@columbus.rr.com> wrote: >> >>>>> I think that the term dynamic range of a receiver is one of the most >>>>> confusing specs when talking about receiver performance. What does >>>>> the term mean to you? >> >>>>> My problem is that many times I see receivers that have a wide >>>>> "static" range due to a front end attenuator that can be varied, but >>>>> that does not seem to be what dynamic range is about. It seems to me >>>>> that dynamic range is about the ability to discriminate two levels >>>>> coming into the receiver (both in the IF "desirable" signal passband) >>>>> at the same time. >> >>>>> Any thoughts? >> >>>>> Brent >> >>>> Brent, you are correct the term is ambiguous and I have seen >>>> misunderstandings before... >> >>>> the AGC can allow the __desired signal___ dynamic range to be very >>>> wide... >> >>>> but as you say.. that tells nothing about the ability of the Rx to Rx >>>> a weak desired signal despite a strong nearby interferer.. I have >>>> seen the term ___instantaneous___ dynamic range used to describe >>>> that. >> >>>> I think the best way to avoid confusion is to create a spec in terms >>>> of use case, i.e. be able to Rx a 1uV signal with 2 50 mV signals in >>>> the first and second adj channel etc... these are sometimes called >>>> blockers.. >> >>>> Mark >> >>> That is excellent advice. From the top level spec a potentially >>> surprising number of lower level specs can be derived, like phase >>> noise for example. >> >>> John- Hide quoted text - >> >>> - Show quoted text - >> >> Actually dynamic range is still best described as in the classic case >> where the largest signals determine the top of the range that in turn >> create distortion products that just start to pop out of the noise >> floor in a given analysis bandwidth. The classic description has used >> two tones, (TOI), and NF. This is still a very effect description >> used to spec receiver design. >> >> Adjustable gain is used as a method of optimizing dynamic range. This >> becomes especially important when you have A/D converters in that back >> end that can create their own artifacts. >> >> Complex modulation schemes come with their own vernacular, but it�s a >> play on the above concept.- Hide quoted text - >> >> - Show quoted text - > > > Another issue to keep in mind is that out of band signals can > certainly �wad-up� the front end, thus making any in band measurements > useless.Another way to put that is that there's not really one two-tone dynamic range -- in general, the closer the two tones get to the intended signal, the stages of the receiver they can get to and the more opportunities they'll have to cause distortion. So signals that are way out won't get through the initial filter, signals that are somewhat out will hit the first mixer, signals that are closer in yet will (depending on the receiver architecture) get through the roofing filter and hit the second mixer, etc. In really weak signal work one also sometimes has to pay attention to a single strong signal mixing with phase noise in the LO and raising the noise floor in the passband. I don't know if this is of concern to anyone but NASA and amateur radio operators, though.> But having said that, most applications have a predetermined > environment of use, and prefiltering may have to be employed.Or at least the environment is somewhat static, and the installation tech will have the opportunity to tweak things (up to and including arguing with owners of other towers in a tower farm about rusty bolts causing IM distortion outside of any radio).> The importance of describing the application and setting systems specs > can not be over stated if the goal is a positive out come on a > receiver project.Any complex project, receiver or not!!! -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html
Reply by ●October 11, 20102010-10-11
On Oct 10, 8:24=A0pm, Fred Marshall <fmarshall_xremove_the...@xacm.org> wrote:> On 10/10/2010 1:41 PM, brent wrote: > > > I think that the term dynamic range of a receiver is one of the most > > confusing specs when talking about receiver performance. =A0What does > > the term mean to you? > > > My problem is that many times I see receivers that have a wide > > "static" range due to a front end attenuator that can be varied, but > > that does not seem to be what dynamic range is about. =A0It seems to me > > that dynamic range is about the ability to discriminate two levels > > coming into the receiver (both in the IF "desirable" signal passband) > > at the same time. > > > Any thoughts? > > > Brent > > It's been a long time .... but I would think of dynamic range being > determined by the noise level for the floor and the clipping level at > the peak. > The ability to discriminate two signals I believe is "selectivity". > > FredI view selectivity as the ability to discriminate one channel from the next and dynamic range as the ability of the receiver to process different level signals within the passband.
