【 reference ：Xuan A N, Negra R. Design of concurrent multiband biasing networks for multiband RF power amplifiers[C]//2012 42nd European Microwave Conference. IEEE, 2012: 1-4.】

Regulations f1 > f2 > ··· > fi , The characteristic impedance of an open microstrip line is Z1, The characteristic impedance of the feeding microstrip is Z0. The open microstrip line is 1/4 Wavelength line , Generally, the characteristic impedance is high , It is beneficial to reduce the size of offset network .

chart 1 Shown , At frequency f1 It's about , The open microstrip line is frequency f1 Of 1/4 Wavelength line , At point 1 There is a short circuit at , The length is l1 The feeding microstrip will point 1 Short circuit conversion point at 0 Open circuit at . Empathy , The offset microstrip design of other frequency points is similar , Due to the point 1 There is a short circuit at , It will not affect the design of other frequency points .

The detailed calculation formula is as follows ：

ADS Design examples

Here is a 1.8GHz、2.2GHz、2.6GHz Three frequency offset network ADS Demonstrate with simulation design examples

Calculate the length of each microstrip line according to the above formula , The construction schematic diagram is as follows:

Simulation results

You can see , stay 1.8GHz、2.2GHz and 2.6GHz It's about ,S11 Both in -30dB following . Put the port 2 And port 3 invalid , Join the grounding point , see 1 Port impedance , The construction schematic diagram is as follows: ：

Simulation results

It can be seen that , The port impedance at the three designed frequency points shows infinity , Meet design requirements .

Layout Layout demonstration

The three grounding capacitors are Murata capacitors , They are bypass capacitors at three frequency points respectively , Bypass capacitance simulation ：

Simulation results

If there are shortcomings , Welcome criticism and correction , Or exchange power amplifier design experience through private letters .