Can Custom Cable Designs Simplify PI Filter Configurations?

[bobber_adam]

Is it possible to design a cable with properties (Capacitance and Inductance) to reduce the number of components needed for the PI filter? I know I can design a cable to have a specific capacitance and specific inductance, but I am not sure if or how i would get these to work with the pi filter. A pi filter has a shunt capacitor, a series inductor and another shunt capacitor If I use the shield of a coax cable as my gound and design the capacitance correct for one of my capacitors in the filter could I get by eliminating one of the capacitors and just placing a series inductor and shunt capacitor in the circuit? Is it possible to use both a designed in capacitance and inductance and only add the second shunt capacitor?

 

[waht]

A coax with its capacitance and inductance will exhibit a constant impedance. All cables are designed to have a 50 ohm impedance, or 75 ohm for the cable industry. The dielectric will also determine the cutoff frequency. So to use it as a low pass filter for any arbitrary frequency is just too much work.

What you have to do is match impedance of the PI filter to the coax.


At higher frequencies we take advantage of microstrip transmission lines that can be made with different impedances that can be arranged as a PI filter and matched to another transmission line.

 

[oswaler]

Yes, it is possible to design a cable with specific capacitance and inductance properties to reduce the number of components needed for a PI filter. This can be achieved by carefully selecting the materials and dimensions of the cable to achieve the desired capacitance and inductance values. However, it is important to note that the cable alone may not be able to fully replace all the components in a PI filter. The PI filter is designed to provide a specific frequency response, and the cable alone may not be able to achieve this without additional components.

In your proposed solution, using the shield of a coaxial cable as the ground and designing the capacitance for one of the capacitors in the filter, it may be possible to eliminate one of the capacitors and only use a series inductor and a shunt capacitor in the circuit. However, this would require careful design and testing to ensure that the frequency response of the filter is still within the desired range.

It is also possible to use a cable with both designed capacitance and inductance and only add the second shunt capacitor in the circuit. Again, this would require careful design and testing to ensure that the filter is still effective in achieving the desired frequency response.

In conclusion, while it is possible to design a cable with specific capacitance and inductance properties to reduce the number of components needed for a PI filter, it is important to carefully consider the desired frequency response and to test the circuit to ensure its effectiveness.