tracking filter

Bandpass filter is used widely in front-end of receiver.
Now I want to deisgn a bandpass tracking filter used in TV receiver.
With a voltage Vt,I can change the bandpass band to select the right TV channel
Because the mixer has the problem with the image signal,
so the bandpass tracking filter must has the additional funtion to reject the image signal and the reject band aslo can be changed with the voltge Vt


Can anyone tell me some resources about how to design this type of filter with variable capacitance diode and how to caluate the filter's parameters

thanks