The Analysis Of Ltcc Balanced Bandpass Filter Design Method Based On Symmetric Circuit

With the development of communications, electronic products and household appliances go to the direction of the high-frequency, digital, the requirements of the components’ integrated as well as modular are more and more urgent. The balance filter is also developed with the needs of both the filter and balun functionality and miniaturization. In this paper, based on symmetric circuit, LTCC balanced bandpass filter design method is analyzed, and balanced bandpass filters which accord with targets are designed.This paper first introduces the basic principle of designing filter-the filter design theory based on the insert loss method and the three-coupled line based on the performance of the symmetrical circuit. The coupling matrix relations verify the bandpass filter-balanced filter conversion based on the symmetric circuit, namely presents design method that the extension from two-port coupled resonator circuit for three-port coupled resonator circuit, make out the three-port coupling resonator circuit model by this method, matlab simulation of the third-order Chebyshev bandpass filter to prove the feasibility of conversion circuits. Then use this conversion process design LTCC balanced filter with no transmission zeros, center frequency is2.45GHz, bandwidth is200MHz.Finally, how to introduce and design the transmission zeros is analysed, design a balanced bandpass filter with transmission zeros by the method which is presented in Chapter III (on the basis of band-pass filter design balance bandpass filter). The Dimensions of LTCC balanced bandpass filter is2.0m×1.25mm×0.9mm, center frequency is2.45GHz, bandwidth is100MHz, insertion loss is less than3.5dB in passband, minimum attenuation between880-990MHz is51dB and has a good phase and amplitude balance. This design has good application prospect in the Bluetooth headset,802.11b/g/n wireless local area network module, Wi-Fi, GPS and other RF wireless receiver module.