On 6 Mar, 22:04, steve sulis <stevesulis-...@yahoo.co.uk> wrote:> On 6 Mar, 06:35, "pal.debabrata123" <pal.debabrata...@gmail.com> > wrote: > > > Is my understanding correct that output impedence (of a source)can be > > modelled by fir/iir filters. The application is none other than voip slic > > who tries to adjust its output impedence so that it becomes the conjugate > > of telephone impedence , thereby maximising power transfer to the > > telephone.I was struggling to get the idea..the pressing questions are > > does a slic behave like a constant current/voltage source?Is the impedence > > is in parallel or series? how a resistor and inductor in series can be > > modelled by a filter? > > > Any insight is greatly appreciated. � > > Patent No �US 6990191 by Legerity includes the fundamentals of what > you want. > Personaly, I used a voltage source via resistive feed to realise a > constant current dc path plus a programmable ac telco impedance done > by FIR filters to get the international matching networks although my > app was not a consumer chip but a precision lab measurement system. > > HTH SteveSorry, that should have been IIR filters.
impedence matching by fir / iir filter
Started by ●March 6, 2008
Reply by ●March 6, 20082008-03-06
Reply by ●March 7, 20082008-03-07
>Richard Owlett wrote: > > ... > >> I wonder if what the OP is actually interested in would be "telephone >> line equalization networks"? > >Maybe he'd like to replace the transformer on his utility pole with a >small computer that calculates the voltage to be delivered to his house. > >Jerry >-- >Engineering is the art of making what you want from things you can get. >??????????????????????????????????????????????????????????????????????? >Ha Ha , good answer, but I was planning to put "the small computer" behind the transformer .Assume transformer behaves the same way all the time and the voltage actually " delivered" to my house depends on length and quality the wire connecting "transformer and my house". The computer should adjust input to the transformer to deliver stable voltage to all houses!
Reply by ●March 7, 20082008-03-07
On Thu, 6 Mar 2008 10:16:48 -0800, "BobW" <nimby_NEEDSPAM@roadrunner.com> wrote:> >"Allan Herriman" <allanherriman@hotmail.com> wrote in message >news:6p90t352ok1ngoc6vbr3e0tgkpcase06ms@4ax.com... >> On Thu, 6 Mar 2008 07:56:59 -0800, "BobW" >> <nimby_NEEDSPAM@roadrunner.com> wrote: >> >>> >>>"pal.debabrata123" <pal.debabrata123@gmail.com> wrote in message >>>news:POydnWsNAPMwDVLanZ2dnUVZ_qSonZ2d@giganews.com... >>>> Is my understanding correct that output impedence (of a source)can be >>>> modelled by fir/iir filters. The application is none other than voip >>>> slic >>>> who tries to adjust its output impedence so that it becomes the >>>> conjugate >>>> of telephone impedence , thereby maximising power transfer to the >>>> telephone.I was struggling to get the idea..the pressing questions are >>>> does a slic behave like a constant current/voltage source?Is the >>>> impedence >>>> is in parallel or series? how a resistor and inductor in series can be >>>> modelled by a filter? >>>> >>>> Any insight is greatly appreciated. >>>> >>> >>>The standard source (and hence termination) impedance for a 2 wire loop is >>>600ohms in series with a 2.15uF capacitor (don't ask me where the >>>precision >>>cap value came from). >> >> The good thing about standards is that there are so many of them. Each >> country has a different standard POTS termination impedance. It's been >> a while since I've looked at the exact values, but I do recall that >> most of them were about 600ohm in the voice frequency range, with a >> capacitive component causing the impedance to fall at higher >> frequencies. >> A quick google came up with "In the United States, the loop is >> nominally 600R, whereas in Britain it is a 300R resistance in series >> with a parallel combination of 1 kR and 220 nF." >> Which country does the 600R + 2.15uF come from? >> > >Allan -- I think that you're confusing the line-modeling network's impedance >(used in the transhybrid circuit) with the line circuit's source/termination >impedance. The 600ohm+2.15uF is from Bell Pub 48002. I have never seen an >R||C used for a source/termination in a line circuit.Bob, I meant exactly what I said. Remember: I'm not the one who's confused here. Regarding the various line impedances, you will need to go outside North America to see something other than Bellcore specs. Most countries specify a termination impedance which has a both a (real) pole and a (real) zero, with the zero being at a higher frequency than the pole. Allan
Reply by ●March 7, 20082008-03-07
pal.debabrata123 wrote:>> Richard Owlett wrote: >> >> ... >> >>> I wonder if what the OP is actually interested in would be "telephone >>> line equalization networks"? >> Maybe he'd like to replace the transformer on his utility pole with a >> small computer that calculates the voltage to be delivered to his house. >> >> Jerry >> -- >> Engineering is the art of making what you want from things you can get. >> ??????????????????????????????????????????????????????????????????????? >> > Ha Ha , good answer, but I was planning to put "the small computer" behind > the transformer .Assume transformer behaves the same way all the time and > the voltage actually " delivered" to my house depends on length and > quality the wire connecting "transformer and my house". The computer > should adjust input to the transformer to deliver stable voltage to all > houses!I think the OP's confusion arises from failure to distinguish a physical operation from its mathematical description. Certainly, there are active impedance generators, just as there are active filters. Active impedance generators require frequency-dependent gain functions; those can be implemented computationally. They also require delivery or absorption of power, the kind that lights bulbs. Hence my (probably too subtle) wisecrack about the pole transformer. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●March 7, 20082008-03-07
"Allan Herriman" <allanherriman@hotmail.com> wrote in message news:45b2t35tghktkodh0f0g0jgdn7p2eluv93@4ax.com... [snip]>>> >> >>Allan -- I think that you're confusing the line-modeling network's >>impedance >>(used in the transhybrid circuit) with the line circuit's >>source/termination >>impedance. The 600ohm+2.15uF is from Bell Pub 48002. I have never seen an >>R||C used for a source/termination in a line circuit. > > Bob, I meant exactly what I said. Remember: I'm not the one who's > confused here. > > Regarding the various line impedances, you will need to go outside > North America to see something other than Bellcore specs. Most > countries specify a termination impedance which has a both a (real) > pole and a (real) zero, with the zero being at a higher frequency than > the pole. > > AllanAllan, My apologies. It appears that you are correct. This Intersil app note shows this complex drive/termination impedance capability: http://www.intersil.com/data/an/an9607.pdf I am now both a little older and a lot wiser. Thanks, Bob
