High-frequency Digital Circuit EMC Design Of Blind Signal Receiver

With the rapid development of microelectronics technology and related technology, Multi-layer Printed Circuit Board (PCB) is more complex. At the same time, the working frequency is increasing. PCB design has entered the stage of GHz or more, but along with the frequency increases, bringing a series problem of electromagnetic interference. Working clock/rise time of signal bus has reached the picosecond, high frequency harmonics components of the signal is also increased, which produced a wider spectrum of electromagnetic radiation and brought a great challenge in electromagnetic compatibility design of the system.At high frequencies, common components will turn out a series of parasitical properties, for example, even a very short wire may become the transmitting antenna to form the electromagnetic interference (EMI). Therefore, in the PCB design, EMC design has been widespread concerned.Firstly, the definition of high-speed signals and high-frequency circuits are described, the PCB transmission line theory and the radiation theory of PCB, including electric dipole radiation and magnetic dipole radiation are introduced in this paper. Secondly, this paper take the high-frequency digital circuit of blind signal receiver as research object, introduced the hardware design of high-frequency digital circuits of the reciver, proposed a method of set up simulation model from Cadence PCB layout to Slwave. The resonant mode and radiation of high-frequency digital circuits of the reciver PCB model are simulated and analyzed by using Ansoft’s Slwave, obtained resonance conditions, near-field radiation and far-field radiation results inside the 100MHz to IGHz range. Then the simulation results are analyzed in this paper, proposed improve measures to related EMI problems, enhanced the system’s electromagnetic compatibility. Simultaneously, the effects of parasitic capacitance, parasitic inductance generated by vias at high frequencies on the PCB EMI’s are also studied.For the receiver PCB vias, this paper put forward relevant optimization measures, introduced some guidelines to follow in the PCB design. Secondly, in order to carry out the electromagnetic compatibility test of high-frequency digital circuits under normal operating conditions, this paper elaborated the software design in detail,which is essential to ensure the normal operation of high-frequency circuits.The software design is mainly FPGA logic design, including the design ideas and module division, the logical design of each module, and carried out performance testing to ensure the system is working properly.Finally, completed the radiated emission test of blind signal receiver frequency circuit PCB under working condition, including far-field radiation test and near-field radiation test. Simulation results were compared to verify the correctness of the simulation.For the strong radiation of high-frequency harmonics and resonance frequency appearing in the test, some measures for improvement has taken in the paper.Compared the test results after the improvements with before, it proved the measures are effective. Meanwhile, remaining deficiencies and future research directions are presented.