Study On Application Of DGS Structure In Common Mode Suppression Of High-speed Differential Signals

With the rapid development of semiconductor manufacturing technology,the chip operating frequency continues to increase,the clock frequency and data transmission rate continue to increase and the circuit package size gradually decreases,the electronic information system has been developed at a high speed.On the one hand,electronic information systems are rapidly developing in the direction of miniaturization,high speed,and high reliability.On the other hand,the signal integrity problem caused by electromagnetic interference has become one of the key factors restricting the performance improvement of electronic information system.When the data transmission rate reaches the Gbps order,compared with the signal integrity problems such as delay,reflection and crosstalk of single-terminal transmission signal lines,differential signaling technology is widely used in high-speed data transmission circuit systems because of its strong noise immunity,low crosstalk and strong antielectromagnetic interference ability.However,in the actual design of signal integrity,common-mode noise is inevitably generated from the timing offset and amplitude imbalance generated by the signal from the signal source,to the process error and wiring discontinuity in the layout design.Common mode noise(CMN)will not only seriously affect the signal integrity,reduce the performance of high speed circuits,but also cause serious electromagnetic radiation problems.Therefore,in order to suppress common-mode noise,it is necessary to design a miniaturized and high-performance common-mode noise filter in a small-volume and highly integrated circuit system to filter out noise while ensuring good transmission characteristics of differential signals.In order to solve the signal integrity caused by common-mode noise in high-speed interconnection circuit system,two kinds of high-performance common-mode noise filters are studied and designed.Firstly,a broadband common-mode filter based on complementary resonant structure is proposed based on the study of quarterwavelength transmission line resonator.The filter uses a quarter-wavelength resonator structure in the form of a coplanar waveguide complementary inside and outside to achieve miniaturization of the common-mode filter,while effectively increasing the suppression bandwidth of common-mode noise due to multiple common-mode transmission zeros.The Z zigzag short-circuit branch line makes the inductive current distribution uneven,increases the coupling,and effectively excites different resonant modes to deepen the suppression depth,and by cascading resonant units of different lengths to obtain ultra-wide common-mode noise suppression stopband.The CMN can be suppressed over 20 dB from 4.1 to 12.5 GHz,with a relative bandwidth of 101%.Secondly,on the basis of studying the common mode filter of ? type defect ground structure(DGS),a common mode filter based on multimode coupled defect ground structure is proposed.The miniaturization of the physical size is achieved by removing the other half of the structure of the ? DGS;at the same time,a quarter-wavelength resonator is etched again inside the structure,which increases the number of common-mode zeros,and realizing the wide-band suppression characteristics by multi-mode coupling.The common-mode noise suppression frequency range is 3.4?9.8 GHz,the relative bandwidth is as high as 98%.Through the simulation and physical test of the above two common-mode noise suppression structures,the consistency of the two results verifies that they have excellent common-mode noise suppression performance,while effectively maintaining the signal integrity of differential signal transmission.