Based on the analysis of circuits and impedance-frequence characteristics of DC filters, two formulas of parameter design for double tuned filter and triple tuned filter are presented in this paper according to impedance at tuning point being 0.

For these reasons the tuned filter must be used when the reactive compensation is done at the existing of system harmonic so as to fulfill the following tasks:do reactive.

The newly developed auto-tuned filters are introduced in this paper.

Single tuned filter is made of capacitance.

The study of multiple-cavity RF tunable filter;

After explaining how to exploit the huge potential capacity of the optical fiber in order to realize high bit rate communication, the paper describes the components used for the wavelength division multi access communication network, particularly the tunable filters and lasers as .

The effect of classic voltage and liquid crystals material parameters on tunable filter transmission spectrum was numerically calculated.

Numerical analysis of tunable filter based on MOEMS technology driven by electrostatic force;

Theoretical study on photonic crystal tunable filter with multiple channels;

Based on this,a tunable filter of double channel of one-dimensional photonic crystal is designed,with the tunable wavelength of 140 nm,tunable FWHM of 1～5 nm,peak value of transmissivit.