Do you think in the not too distant future some guy at home or at Uni is going to re-invent the RC first-order filter? After years of study at Uni and z-transforms,difference equations,c programing and such like some guy is going ot have a Eureka moment..F*** me I can do all this with a few external components and an op-amp!! Way hay... Hardy
The discovery of the R-C circuit.
Started by ●October 18, 2008
Reply by ●October 18, 20082008-10-18
HardySpicer wrote:> Do you think in the not too distant future some guy at home or at Uni > is going to re-invent the RC first-order filter? After years of study > at Uni and z-transforms,difference equations,c programing and such > like some guy is going ot have a Eureka moment..F*** me I can do all > this with a few external components and an op-amp!!A local lumber yard had a special on boards a few years ago: Saws like plastic! Drills like plastic! Glues up like plastic! What's more, you can nail it! Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●October 28, 20082008-10-28
On Oct 18, 8:19�pm, HardySpicer <gyansor...@gmail.com> wrote:> Do you think in the not too distant future some guy at home or at Uni > is going to re-invent the RC first-order filter? After years of study > at Uni and z-transforms,difference equations,c programing and such > like some guy is going ot have a Eureka moment..F*** me I can do all > this with a few external components and an op-amp!! > Way hay... > > HardyTom Barnwell, formerly a professor at Georgia Tech, once described DSP as ��That discipline which has allowed us to replace a circuit previously composed of a capacitor and a resistor with two anti-aliasing filters, an A-to-D and a D-to-A converter, and a general purpose computer (or array processor) so long as the signal we are interested in does not vary too quickly.�
Reply by ●October 28, 20082008-10-28
Jerry Wolf wrote: (snip)> Tom Barnwell, formerly a professor at Georgia Tech, once described DSP > as > ��That discipline which has allowed us to replace a circuit previously > composed of a capacitor and a resistor with two anti-aliasing filters, > an A-to-D and a D-to-A converter, and a general purpose computer (or > array processor) so long as the signal we are interested in does not > vary too quickly.�Well, the restriction is there for the analog circuit, as capacitors get harder to make at higher frequencies. Resistors don't have as many problems as capacitors at high frequencies. -- glen
Reply by ●October 28, 20082008-10-28
On Oct 28, 11:38�am, Jerry Wolf <jjwo...@verizon.net> wrote:> On Oct 18, 8:19�pm, HardySpicer <gyansor...@gmail.com> wrote: > > > Do you think in the not too distant future some guy at home or at Uni > > is going to re-invent the RC first-order filter? After years of study > > at Uni and z-transforms,difference equations,c programing and such > > like some guy is going ot have a Eureka moment..F*** me I can do all > > this with a few external components and an op-amp!! > > Way hay... > > > Hardy > > Tom Barnwell, formerly a professor at Georgia Tech, once described DSP > as > ��That discipline which has allowed us to replace a circuit previously > composed of a capacitor and a resistor with two anti-aliasing filters, > an A-to-D and a D-to-A converter, and a general purpose computer (or > array processor) so long as the signal we are interested in does not > vary too quickly.�Given that the antialiasing filter might itself be a resistor and a capacitor, does that mean DSP is totally redundant? :-) Dirk
Reply by ●October 28, 20082008-10-28
Glen Herrmannsfeldt wrote:> Jerry Wolf wrote: > (snip) > >> Tom Barnwell, formerly a professor at Georgia Tech, once described DSP >> as >> ��That discipline which has allowed us to replace a circuit previously >> composed of a capacitor and a resistor with two anti-aliasing filters, >> an A-to-D and a D-to-A converter, and a general purpose computer (or >> array processor) so long as the signal we are interested in does not >> vary too quickly.� > > Well, the restriction is there for the analog circuit, as capacitors > get harder to make at higher frequencies. Resistors don't have as > many problems as capacitors at high frequencies.Even attaching them resistors be a problem. General Radio used to make planar radial resistors for terminating coaxial lines. Not only is the resistance and maintenance of radial symmetry important, but the radial distribution of resistivity on the disk affects reflections on the line. I can make a drop of water much purer than I can make any electrical component, with the possible exception of a superconducting inductor. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●October 28, 20082008-10-28
Jerry Avins wrote: (snip on resistors and capacitors)> Even attaching them resistors be a problem. General Radio used to make > planar radial resistors for terminating coaxial lines. Not only is the > resistance and maintenance of radial symmetry important, but the radial > distribution of resistivity on the disk affects reflections on the line.I would make the resistor distributed along a coaxial line such that the absorption is not at just one point. Reflections will also be distributed, and will tend to cancel out any imperfections in the resistor. Also, the power rating will be better with the heat distributed out.> I can make a drop of water much purer than I can make any electrical > component, with the possible exception of a superconducting inductor.It is interesting, though, that resistivity has one of the largest dynamic ranges of any physical quantity. -- glen
Reply by ●October 29, 20082008-10-29
glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:>Jerry Avins wrote:>(snip on resistors and capacitors)>> Even attaching them resistors be a problem. General Radio used to make >> planar radial resistors for terminating coaxial lines. Not only is the >> resistance and maintenance of radial symmetry important, but the radial >> distribution of resistivity on the disk affects reflections on the line.>I would make the resistor distributed along a coaxial line >such that the absorption is not at just one point. Reflections >will also be distributed, and will tend to cancel out any >imperfections in the resistor.I'm trying to wrap my head around the idea that distributing a resistor will still have the effect of terminating a transmission line, and I'm not getting it. Steve
Reply by ●October 29, 20082008-10-29
Steve Pope wrote:> glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote: > >> Jerry Avins wrote: > >> (snip on resistors and capacitors) > >>> Even attaching them resistors be a problem. General Radio used to make >>> planar radial resistors for terminating coaxial lines. Not only is the >>> resistance and maintenance of radial symmetry important, but the radial >>> distribution of resistivity on the disk affects reflections on the line. > >> I would make the resistor distributed along a coaxial line >> such that the absorption is not at just one point. Reflections >> will also be distributed, and will tend to cancel out any >> imperfections in the resistor. > > I'm trying to wrap my head around the idea that distributing > a resistor will still have the effect of terminating a transmission > line, and I'm not getting it.Imagine a disk that caps the end of a piece of co-ax, making circumferential contact to the outer conductor and pressed also against the inner conductor. Imagine that the resistivity is adjusted so that an ohmmeter would indicate the co-ax's characteristic impedance when connected at the far end of the line. That's a pretty good termination, and from a little way back it should be hard to tell from local measurements if the line terminates or continues. Close enough, there might be distortion of the radial electric field, but varying the resistivity in the radial direction while maintaining radial symmetry can eliminate that effect. A termination made that way can have a reflection coefficient < .001 from DC well into the GHz range. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●October 29, 20082008-10-29
Jerry Avins <jya@ieee.org> writes:> Steve Pope wrote: >> glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote: >> >>> Jerry Avins wrote: >> >>> (snip on resistors and capacitors) >> >>>> Even attaching them resistors be a problem. General Radio used to >>>> make planar radial resistors for terminating coaxial lines. Not >>>> only is the resistance and maintenance of radial symmetry >>>> important, but the radial distribution of resistivity on the disk >>>> affects reflections on the line. >> >>> I would make the resistor distributed along a coaxial line >>> such that the absorption is not at just one point. Reflections >>> will also be distributed, and will tend to cancel out any >>> imperfections in the resistor. >> >> I'm trying to wrap my head around the idea that distributing >> a resistor will still have the effect of terminating a transmission >> line, and I'm not getting it. > > > Imagine a disk that caps the end of a piece of co-ax, making > circumferential contact to the outer conductor and pressed also > against the inner conductor. Imagine that the resistivity is adjusted > so that an ohmmeter would indicate the co-ax's characteristic > impedance when connected at the far end of the line. That's a pretty > good termination, and from a little way back it should be hard to tell > from local measurements if the line terminates or continues. Close > enough, there might be distortion of the radial electric field, but > varying the resistivity in the radial direction while maintaining > radial symmetry can eliminate that effect. A termination made that way > can have a reflection coefficient < .001 from DC well into the GHz > range.Jerry, Please tell me where you are teaching so I can enroll in your classes. --An admirer -- % Randy Yates % "Watching all the days go by... %% Fuquay-Varina, NC % Who are you and who am I?" %%% 919-577-9882 % 'Mission (A World Record)', %%%% <yates@ieee.org> % *A New World Record*, ELO http://www.digitalsignallabs.com
