Hello, Books describing LTI systems often make reference to "real valued impulse response". I am little confused here ... what type of practical systems would have "complex values impulse response" vis-a-vis "real valued impulse response" Thank you _____________________________ Posted through www.DSPRelated.com
real valued impulse response
Started by ●August 15, 2014
Reply by ●August 15, 20142014-08-15
The baseband-equivalent impulse response of a carrier-modulated system is generally complex-valued. On Friday, August 15, 2014 4:15:39 AM UTC-4, SBR123 wrote:> Hello, > > > > Books describing LTI systems often make reference to "real valued impulse > > response". I am little confused here ... what type of practical systems > > would have "complex values impulse response" vis-a-vis "real valued impulse > > response" > > > > Thank you > > > > _____________________________ > > Posted through www.DSPRelated.com
Reply by ●August 15, 20142014-08-15
so Julius, is there a wire somewhere that, when you connect a DVM to it, it reads a complex value for the voltage? :-) On 8/15/14 8:51 AM, julius wrote:> The baseband-equivalent impulse response of a carrier-modulated system is generally complex-valued. > > > On Friday, August 15, 2014 4:15:39 AM UTC-4, SBR123 wrote: >> Hello, >> >> >> >> Books describing LTI systems often make reference to "real valued impulse >> >> response". I am little confused here ... what type of practical systems >> >> would have "complex values impulse response" vis-a-vis "real valued impulse >> >> response" >> >> >> >> Thank you >> >> >> >> _____________________________ >> >> Posted through www.DSPRelated.com >-- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●August 15, 20142014-08-15
What's a DVM? On Friday, August 15, 2014 9:11:05 AM UTC-4, robert bristow-johnson wrote:> so Julius, is there a wire somewhere that, when you connect a DVM to it, > > it reads a complex value for the voltage? > > > > :-) > > > > On 8/15/14 8:51 AM, julius wrote: > > > The baseband-equivalent impulse response of a carrier-modulated system is generally complex-valued. > > > > > > > > > On Friday, August 15, 2014 4:15:39 AM UTC-4, SBR123 wrote: > > >> Hello, > > >> > > >> > > >> > > >> Books describing LTI systems often make reference to "real valued impulse > > >> > > >> response". I am little confused here ... what type of practical systems > > >> > > >> would have "complex values impulse response" vis-a-vis "real valued impulse > > >> > > >> response" > > >> > > >> > > >> > > >> Thank you > > >> > > >> > > >> > > >> _____________________________ > > >> > > >> Posted through www.DSPRelated.com > > > > > > > >
Reply by ●August 15, 20142014-08-15
Digital VoltMeter like you place the two probes on two different nodes to measure the voltage between them and it reads out "4.89 + j*2.01 volts". (my point is that "imaginary-valued voltages are imaginary", but inside the mind of a computer there is nothing stopping us from representing a complex-valued quantity. the "baseband-equivalent" is an *equivalent* in a representative sense, not the *actual*.) later. On 8/15/14 9:49 AM, julius wrote:> What's a DVM? > > > On Friday, August 15, 2014 9:11:05 AM UTC-4, robert bristow-johnson wrote: >> so Julius, is there a wire somewhere that, when you connect a DVM to it, >> >> it reads a complex value for the voltage? >> >> >> >> :-) >> >> >> >> On 8/15/14 8:51 AM, julius wrote: >> >>> The baseband-equivalent impulse response of a carrier-modulated system is generally complex-valued. >> >>> >> >>> >> >>> On Friday, August 15, 2014 4:15:39 AM UTC-4, SBR123 wrote: >> >>>> Hello, >> >>>> >> >>>> >> >>>> >> >>>> Books describing LTI systems often make reference to "real valued impulse >> >>>> >> >>>> response". I am little confused here ... what type of practical systems >> >>>> >> >>>> would have "complex values impulse response" vis-a-vis "real valued impulse >> >>>> >> >>>> response" >> >>>> >> >>>> >> >>>> >> >>>> Thank you >> >>>> >> >>>> >> >>>> >> >>>> _____________________________ >> >>>> >> >>>> Posted through www.DSPRelated.com >> >>> >> >> >> >> >> > >-- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●August 15, 20142014-08-15
On Fri, 15 Aug 2014 09:58:21 -0400, robert bristow-johnson <rbj@audioimagination.com> wrote:>like you place the two probes on two different nodes to measure the >voltage between them and it reads out "4.89 + j*2.01 volts".IQ modulators and demodulators generate measurable components 90� out of phase, one of which can be defined as the real part and the other (or its negative) as the imaginary part. That's the key: we can take two signals, define one of them to be the real part of a complex signal and the other to be the imaginary part, and analyze accordingly. Greg
Reply by ●August 15, 20142014-08-15
On Fri, 15 Aug 2014 03:15:39 -0500, "SBR123" <100967@dsprelated> wrote:>Hello, > >Books describing LTI systems often make reference to "real valued impulse >response". I am little confused here ... what type of practical systems >would have "complex values impulse response" vis-a-vis "real valued impulse >response" > >Thank youAnything where phase matters. Communication Channel impulse responses are typically represented with complex quantities, especially when the modulation method uses complex-valued symbols (i.e., phase matters). Even when the modulation is real-valued (e.g., BPSK), the complex-valued channel response can be important, since the signal phase can be changed by the channel. There are actually a lot of practical examples. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●August 15, 20142014-08-15
Top posting -- uhgh. So, Robert -- don't you have at least one such DMM stashed away? I thought it was essential for anyone who seriously worked in DSP! On Fri, 15 Aug 2014 09:11:05 -0400, robert bristow-johnson wrote:> so Julius, is there a wire somewhere that, when you connect a DVM to it, > it reads a complex value for the voltage? > > :-) > > On 8/15/14 8:51 AM, julius wrote: >> The baseband-equivalent impulse response of a carrier-modulated system >> is generally complex-valued. >> >> >> On Friday, August 15, 2014 4:15:39 AM UTC-4, SBR123 wrote: >>> Hello, >>> >>> >>> >>> Books describing LTI systems often make reference to "real valued >>> impulse >>> >>> response". I am little confused here ... what type of practical >>> systems >>> >>> would have "complex values impulse response" vis-a-vis "real valued >>> impulse >>> >>> response" >>> >>> >>> >>> Thank you >>> >>> >>> >>> _____________________________ >>> >>> Posted through www.DSPRelated.com >>-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●August 15, 20142014-08-15
On Friday, August 15, 2014 9:58:21 AM UTC-4, robert bristow-johnson wrote:> Digital VoltMeter > > like you place the two probes on two different nodes to measure the > voltage between them and it reads out "4.89 + j*2.01 volts".I don't often need a volt meter, but when I do I prefer somebody else do the measurement for me ;-).> > (my point is that "imaginary-valued voltages are imaginary", but inside > the mind of a computer there is nothing stopping us from representing a > complex-valued quantity. the "baseband-equivalent" is an *equivalent* > in a representative sense, not the *actual*.) > > later. >Not sure what you're getting at, but I believe Greg Berchin has the answer.
Reply by ●August 17, 20142014-08-17
"Tim Wescott" wrote in message news:2vCdneXeWKr8uXPOnZ2dnUVZ5g2dnZ2d@giganews.com... Top posting -- uhgh. So, Robert -- don't you have at least one such DMM stashed away? I thought it was essential for anyone who seriously worked in DSP! But in DSP wouldn't the DVM only read "1" or "0" ? ;-) On Fri, 15 Aug 2014 09:11:05 -0400, robert bristow-johnson wrote:> so Julius, is there a wire somewhere that, when you connect a DVM to it, > it reads a complex value for the voltage? > > :-) > > On 8/15/14 8:51 AM, julius wrote: >> The baseband-equivalent impulse response of a carrier-modulated system >> is generally complex-valued. >> >> >> On Friday, August 15, 2014 4:15:39 AM UTC-4, SBR123 wrote: >>> Hello, >>> >>> >>> >>> Books describing LTI systems often make reference to "real valued >>> impulse >>> >>> response". I am little confused here ... what type of practical >>> systems >>> >>> would have "complex values impulse response" vis-a-vis "real valued >>> impulse >>> >>> response" >>> >>> >>> >>> Thank you >>> >>> >>> >>> _____________________________ >>> >>> Posted through www.DSPRelated.com >>-- Tim Wescott Wescott Design Services http://www.wescottdesign.com
