pls give me some ideas on how to design the filter with?

Frequency range 1880MHz---1900MHz

My VCO working frequency is almost 3.8GHz,so i must control the 2nd harmonic radiation.

What i need is some solutions about how to design the filter with impedance matching.Sometimes i can find out good filter circuits,but impedance mis-matching.

Please give me your professional advices.

Your question is vague. Could you please make it clear?

I am sorry for this.

I need some professional suggestions about how to handle complex relations between RF filter and impedance matching.

RF signal from PA need a filter,but i must consider the impedance matching.It always confused me.I have no ideas.

Thank you in advance.

Impedance matching is simple compensating the reactance at the port and making resistive parts are equal. For example, you have a PA that have output impedance Zout=50-j20. It is capacitive impedance because X is negative. In order to have maximum power transfer to the load and minimum power reflected back to the output circuit of the PA you need to make the load having input impedance of Zload=50+j20. This is so called conjugate match and it will ensure that reactance compensates and there will be no reflections whereas resistive parts are equal and maximum power is flow to the load. It is relatively easy to do for single frequency, but harder for broadband applications. The goal is to be as close to conjugate match as it possible. There are some exceptions, for example, optimal noise input or output matching, or special matching for stability issues.

In your particular case if PA has Zout=50-j20, filter must have Zin=50+j20. It can be done by different ways depends on bandwidth, power level and so on.

If you need Professional suggestion the You should take help of software such as ADS or Genesys for impedance matching.
you need not worry much since I dont see your Bandwidth is large, it is 20 MHz,right?
Take help of softwares,you will get optimum match & good power transfer.