ads l matching network
I need your advise, because I wish to design for my thesis of magister in data networks, a cuadripole programmable electronically, which can adapt, from 24kHz to 1100kHz, an impedance (the ADSL transmission line to user house, which sees the Dislam from the central office) which varies with the frequency in a arbitrary way. The objetive is obtain the maximum throughput possible of the line, despite of the mismatches and line parasitic derivations into the subscriber house.
To make this, I am thinking in a multitude of capacitors and inductors of different values and with a FPGA or a microntroller with analog switches interconnect them into a network ladder. This will be a formidable problem, that I will tackle later.
1) My inmediate issue is to find an algoritm or procedure that I can use to compute the matching network, preferably without human intervention. I am thinking in a Matlab or Matcad program, but, please do not feel influenced for me
2) The other advise that I need, is your sincere opinion about if you think that the theme is enough original for a thesis, or you heard before about a similar project.
You should use an DSP to compensate for line distortion. First find the line parameters with a unity pulse and then make an equilizer to compensate for line parameters no L,C or R's needed at all !,.
My assumption is, that ADSL transmitter/receiver chip already performs adaptive line matching including correction of frequency dependant attenuation and line discontinuities (if seen at all). Line is terminated with nominal impedance, but as the dominant non-ideal behaviour is due to attenuation rather than reflections, this isn't a real disadvantage. If I'm correct, an additional adaptive matching circuit would only cause losses respectively decreased SNR and not have any benefit.
Did you check the basic situation of ADSL transmission in this regard, particularly which type of line compensation is already done in existing hardware?
I had the same understanding that ADSL chipsets perform equilizing, but since your a student I thought you wanted to make your own ADSL system
Dear PaulHolland and Fvm, thanks for your replies.
The ADSL perform equalizing selecting the channels that have better S/N ratio, but do not perform, neither the Dislam, analog impedance matching. Think it is very difficult (I want to do that) adapt more than a decade.
Please forget the ADSL word, and think in a transmision line, of 5km of lenght, normally with not wanted bridged taps, joints, connections with rust, and probably bad ended, all proper of an old twisted wire pair infrastructure.
The Zin that sees the Dislam varies the module and the phase with the frequency. I wish to design a broadband matching circuit that mantain the Zin=600 ohm from 25kHz to 1100kHz, in order to maximize the energy transfer.