Research On Miniaturized Filter Technology For 5G Communication System

With the rapid development of the fifth generation mobile communication technology,the requirements for the size and performance of the device are getting higher and higher.The filter plays a very important role in the communication system,and is often used in a phase-locked loop feedback loop and to suppress image interference generated after mixing.Therefore,a high-performance and miniaturized filter design is particularly important.Low temperature co-fired ceramic(LTCC)technology and integrated passive device(IPD)technology of gallium arsenide substrate are very conducive to the miniaturization of the device.The former allows the designer to design in the third dimension,the latter can meet the high precision requirements for component size.Based on the above two technologies,this paper designs a small S-band lumped low-pass filter and a new K-band reflectionless band-pass filter.The main work contents are as follows:(1)The inductance and capacitance structure under the multi-layer junction dielectric structure was studied,the common inductance and capacitance model and its equivalent circuit were given,the extraction methods of each parameter in the model were analyzed.Using LTCC technology,a miniaturized lumped low-pass filter based on elliptic function topology is designed.Its cut-off frequency is 3.9GHz,the in-band return loss is better than 17dB,and the physical size of the filter is 3.65mm×2.9mm×1.5mm(0.047?g×0.037?g×0.019?g)(2)A reflectionless band-pass filter structure consisting of a Lange coupler and a reflective filter is proposed.The principle of non-reflection is analyzed,and the anti-load migration capabilities of the reflective filter and reflectionless filter are analyzed.On this basis,a thin-film IPD technology was used to design a miniaturized reflective millimeter wave bandpass filter and a 3dB Lange coupler Among them,the band-pass filter uses a foldable mesh resonator,and the area is significantly reduced compared to the traditional split ring resonator.The center frequency of the resulting reflectionless bandpass filter is 26GHz,the relative bandwidth is about 8%,the in-band return loss is better than 20dB,and the out-of-band return loss is better than 14dB in a wide frequency band.The physical size of the filter is 2.2mm×1.9mm(0.18?g×0.164?g).