Hi, I'm an hold analog engineer , actually developing a DSP based application and I need to change of 90 degrees the phase of a signal on the range of 50 - 250 Hz aving the system a 200uSec sampling rate. I have considered the Hilbert FIR filter but for the moment I cannot get it to work not even reducing the sampling rate. In particular I nedd to phase shift by 90 degrees a signal (voltage) respect to another (current) in order to calculate the instantaneous REACTIVE power by a simple multiplication. Any suggestion would be very appreciated. Thanks everybody
90 degrees phase shift
Started by ●July 1, 2005
Reply by ●July 1, 20052005-07-01
Giuseppe Sbarra wrote:> Hi, > I'm an hold analog engineer , actually developing a DSP based application > and I need to change of 90 degrees the phase of a signal on the range of > 50 - 250 Hz aving the system a 200uSec sampling rate. > I have considered the Hilbert FIR filter but for the moment I cannot get it > to work not even reducing the sampling rate. > In particular I nedd to phase shift by 90 degrees a signal (voltage) respect > to another (current) in order to calculate the instantaneous REACTIVE power > by a simple multiplication. > > Any suggestion would be very appreciated. > Thanks everybody > >I'm not sure why your hilbert transform wouldn't be working so I can't comment on it. On the other hand, if you were to compute the RMS value of the voltage and current and compute the mean power then the reactive "power" should be Vrms * Irms - real power. That's how I'd do it. -- ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●July 1, 20052005-07-01
"Tim Wescott" <tim@seemywebsite.com> wrote in message news:11cath1cpvl3i29@corp.supernews.com...> Giuseppe Sbarra wrote: > >> Hi, >> I'm an hold analog engineer , actually developing a DSP based application >> and I need to change of 90 degrees the phase of a signal on the range of >> 50 - 250 Hz aving the system a 200uSec sampling rate. >> I have considered the Hilbert FIR filter but for the moment I cannot get >> it >> to work not even reducing the sampling rate. >> In particular I nedd to phase shift by 90 degrees a signal (voltage) >> respect >> to another (current) in order to calculate the instantaneous REACTIVE >> power >> by a simple multiplication. >> >> Any suggestion would be very appreciated. >> Thanks everybody >> >> > I'm not sure why your hilbert transform wouldn't be working so I can't > comment on it. > > On the other hand, if you were to compute the RMS value of the voltage and > current and compute the mean power then the reactive "power" should be > > Vrms * Irms - real power. > > That's how I'd do it. >Surely that is'nt true V*I=S=sqrt(P^2 +Q^2) so reactive power = Q = sqrt(S^2 - P^2)> -- > ------------------------------------------- > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com
Reply by ●July 1, 20052005-07-01
Pierre de Vos wrote:> "Tim Wescott" <tim@seemywebsite.com> wrote in message > news:11cath1cpvl3i29@corp.supernews.com... > >>Giuseppe Sbarra wrote: >> >> >>>Hi, >>>I'm an hold analog engineer , actually developing a DSP based application >>>and I need to change of 90 degrees the phase of a signal on the range of >>>50 - 250 Hz aving the system a 200uSec sampling rate. >>>I have considered the Hilbert FIR filter but for the moment I cannot get >>>it >>>to work not even reducing the sampling rate. >>>In particular I nedd to phase shift by 90 degrees a signal (voltage) >>>respect >>>to another (current) in order to calculate the instantaneous REACTIVE >>>power >>>by a simple multiplication. >>> >>>Any suggestion would be very appreciated. >>>Thanks everybody >>> >>> >> >>I'm not sure why your hilbert transform wouldn't be working so I can't >>comment on it. >> >>On the other hand, if you were to compute the RMS value of the voltage and >>current and compute the mean power then the reactive "power" should be >> >>Vrms * Irms - real power. >> >>That's how I'd do it. >> > > Surely that is'nt true > > V*I=S=sqrt(P^2 +Q^2) > so > reactive power = Q = sqrt(S^2 - P^2) >Well, I'll be dipped in shaving cream. Thank you for finding my error. It's still an easier calculation than the Hilbert Transform, though. ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●July 1, 20052005-07-01
Giuseppe Sbarra wrote:> > Hi, > I'm an hold analog engineer , actually developing a DSP based application > and I need to change of 90 degrees the phase of a signal on the range of > 50 - 250 Hz aving the system a 200uSec sampling rate. > I have considered the Hilbert FIR filter but for the moment I cannot get it > to work not even reducing the sampling rate. > In particular I nedd to phase shift by 90 degrees a signal (voltage) respect > to another (current) in order to calculate the instantaneous REACTIVE power > by a simple multiplication.If you are using an FIR hilbert transform, you need to remember that there is a transport delay in the FIR filter and you need to delay the unfiltered version as well. Erik -- +-----------------------------------------------------------+ Erik de Castro Lopo nospam@mega-nerd.com (Yes it's valid) +-----------------------------------------------------------+ Saying Python is easier than C++ is like saying that turning a light switch on or off is easier than operating a nuclear reactor.
Reply by ●July 1, 20052005-07-01
"Giuseppe Sbarra" <giuseppe_sbarra@tin.it> wrote in news:q9exe.101452$75.4536009@news4.tin.it:> Hi, > I'm an hold analog engineer , actually developing a DSP based > application and I need to change of 90 degrees the phase of a signal > on the range of 50 - 250 Hz aving the system a 200uSec sampling rate. > I have considered the Hilbert FIR filter but for the moment I cannot > get it to work not even reducing the sampling rate. > In particular I nedd to phase shift by 90 degrees a signal (voltage) > respect to another (current) in order to calculate the instantaneous > REACTIVE power by a simple multiplication. > > Any suggestion would be very appreciated. > Thanks everybody >Wideband 90-degree phase shift networks are used in the phasing method of single sideband generation. The network consists of two sets of cascaded second-order all-pass sections which maintain a 90 degree phase difference to within a specified accuracy over a specified bandwidth. An introduction to the design of analog 90-degree phase shift networks can be found at: http://home.att.net/~wa1sov/technical/allpass/allpass.html Once you have the pole-zero locations, you should be able to implement the filter digitally.
Reply by ●July 1, 20052005-07-01
Tim Wescott <tim@seemywebsite.com> wrote in news:11cbep3v3id1d9@corp.supernews.com:> Pierre de Vos wrote: > >> "Tim Wescott" <tim@seemywebsite.com> wrote in message >> news:11cath1cpvl3i29@corp.supernews.com... >> >>>Giuseppe Sbarra wrote: >>> >>> >>>>Hi, >>>>I'm an hold analog engineer , actually developing a DSP based >>>>application and I need to change of 90 degrees the phase of a signal >>>>on the range of 50 - 250 Hz aving the system a 200uSec sampling >>>>rate. I have considered the Hilbert FIR filter but for the moment I >>>>cannot get it >>>>to work not even reducing the sampling rate. >>>>In particular I nedd to phase shift by 90 degrees a signal (voltage) >>>>respect >>>>to another (current) in order to calculate the instantaneous >>>>REACTIVE power >>>>by a simple multiplication. >>>> >>>>Any suggestion would be very appreciated. >>>>Thanks everybody >>>> >>>> >>> >>>I'm not sure why your hilbert transform wouldn't be working so I >>>can't comment on it. >>> >>>On the other hand, if you were to compute the RMS value of the >>>voltage and current and compute the mean power then the reactive >>>"power" should be >>> >>>Vrms * Irms - real power. >>> >>>That's how I'd do it. >>> >> >> Surely that is'nt true >> >> V*I=S=sqrt(P^2 +Q^2) >> so >> reactive power = Q = sqrt(S^2 - P^2) >> > Well, I'll be dipped in shaving cream. Thank you for finding my > error. > > It's still an easier calculation than the Hilbert Transform, though. > > ------------------------------------------- > Tim Wescott > Wescott Design Services > http://www.wescottdesign.comYou also missed the stipulation that a calculation of instantaneous power was required.
Reply by ●July 1, 20052005-07-01
TheGhost. wrote:> "Giuseppe Sbarra" <giuseppe_sbarra@tin.it> wrote in > news:q9exe.101452$75.4536009@news4.tin.it: > > >>Hi, >>I'm an hold analog engineer , actually developing a DSP based >>application and I need to change of 90 degrees the phase of a signal >>on the range of 50 - 250 Hz aving the system a 200uSec sampling rate. >>I have considered the Hilbert FIR filter but for the moment I cannot >>get it to work not even reducing the sampling rate. >>In particular I nedd to phase shift by 90 degrees a signal (voltage) >>respect to another (current) in order to calculate the instantaneous >>REACTIVE power by a simple multiplication. >> >>Any suggestion would be very appreciated. >>Thanks everybody >> > > > Wideband 90-degree phase shift networks are used in the phasing method of > single sideband generation. The network consists of two sets of cascaded > second-order all-pass sections which maintain a 90 degree phase difference > to within a specified accuracy over a specified bandwidth. An introduction > to the design of analog 90-degree phase shift networks can be found at: > http://home.att.net/~wa1sov/technical/allpass/allpass.html > Once you have the pole-zero locations, you should be able to implement the > filter digitally.There are better ways to design a digital all-pass filter pair to achieve relative quadrature. The best you can do analog over a decade is about half a degree. With a digital pair you do better than that over a wider band. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●July 1, 20052005-07-01
Jerry Avins <jya@ieee.org> wrote in news:lMWdnZN04tN6e1jfRVn-2Q@rcn.net:> TheGhost. wrote: >> "Giuseppe Sbarra" <giuseppe_sbarra@tin.it> wrote in >> news:q9exe.101452$75.4536009@news4.tin.it: >> >> >>>Hi, >>>I'm an hold analog engineer , actually developing a DSP based >>>application and I need to change of 90 degrees the phase of a signal >>>on the range of 50 - 250 Hz aving the system a 200uSec sampling rate. >>>I have considered the Hilbert FIR filter but for the moment I cannot >>>get it to work not even reducing the sampling rate. >>>In particular I nedd to phase shift by 90 degrees a signal (voltage) >>>respect to another (current) in order to calculate the instantaneous >>>REACTIVE power by a simple multiplication. >>> >>>Any suggestion would be very appreciated. >>>Thanks everybody >>> >> >> >> Wideband 90-degree phase shift networks are used in the phasing >> method of single sideband generation. The network consists of two >> sets of cascaded second-order all-pass sections which maintain a 90 >> degree phase difference to within a specified accuracy over a >> specified bandwidth. An introduction to the design of analog >> 90-degree phase shift networks can be found at: >> http://home.att.net/~wa1sov/technical/allpass/allpass.html Once you >> have the pole-zero locations, you should be able to implement the >> filter digitally. > > There are better ways to design a digital all-pass filter pair to > achieve relative quadrature. The best you can do analog over a decade > is about half a degree. With a digital pair you do better than that > over a wider band. > > JerryThen, perhaps you should provide the original poster with some references that will help him get started.
Reply by ●July 1, 20052005-07-01
.TheGhost wrote:> Jerry Avins <jya@ieee.org> wrote in news:lMWdnZN04tN6e1jfRVn-2Q@rcn.net:...>>There are better ways to design a digital all-pass filter pair to >>achieve relative quadrature. The best you can do analog over a decade >>is about half a degree. With a digital pair you do better than that >>over a wider band. > > > > Then, perhaps you should provide the original poster with some references > that will help him get started.I'm hazy on the details. I think Randy Yates can provide them succinctly. Although I don't always succeed, I try very hard not to misinform, keeping mum when I know that I don't know. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
