High frequency low pass filter - avoid the use of inductors

Discussion in 'Wireless & RF Design' started by santais, Dec 2, 2014.

  1. santais

    Thread Starter New Member

    Mar 18, 2011
    Hi all.

    I'm currently working on an embedded project, where I'm making a decoder for a PAL video signal, to be used for object recognition.

    At the moment, I'm stuck at the point, where I want to filter the chroma away from the luma signal, which is located at around 3 MHz to 4.5 MHz.

    So far I've tried to make a simple 6. order Butterworth LC analog low pass filter, however the values obtained for the inductors, are simply too small compared to inference from other magnetic fields etc. I spoke with my professor and he suggested a simple RC filter. From what I read, the problem with RC filters at higher frequencies is because of the underdamped response of the system. As in this case, an active filter is more reliable. But due to the limitations of high bandwith OP-AMP available at the university and the waiting time if I am to order one, makes it a bit difficult to construct a simple low pass filter before the deadline.

    So I was wondering, if any if you had en pre experience in which it would be possible to make a fairly simple filter, without having to order any specific components. The cutoff frequency is desired to be around 3 - 3.5 MHz with a stopband attenuation of 20 dB.

    Thanks in advance!
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    color tv has used that for years, and the inductors are not super tiny. there are also SAW (surface acoustic wave ) filters designed for american color tv's .
  3. santais

    Thread Starter New Member

    Mar 18, 2011
    Thanks for the answer alfacliff. Never heard of it, but definitely going to look into it!
  4. Papabravo


    Feb 24, 2006
    Show us your specifications and calculations. What kind of inductorrs are you considering? You may have made a mistake somewhere. I've made several bandpass and notch filters for the 80 M amateur band.