Abstract:TDR simulations using FDTD technology are used to analyze a high-speed HDMI connector.Accurate modeling and simulation of high speed connectors is critical to successful high-speed signal transmission. This example demonstrates how a time domain based EM simulator helps in identifying problem areas, and discontinuities of an HDMI connector. The speed of the simulator makes it easy to run multiple simulations for a better understanding and to optimize for a good impedance profile throughout the transitions.
High speed connectors are widely employed for high speed digital signal transmission. With the progress of technology, more advanced transmission interfaces are used such as Universal Serial Bus (USB), Digital Video Interface (DVI), High Definition Multimedia Interface (HDMI), etc. High speed connectors compatible with these interfaces are also advancing. Since these connectors are used for applications up to 10.2 Gbit/s (for HDMI), accurate modeling and simulation of them becomes critical to successful high speed signal transmission.
HDMI has emerged as a data transmission standard for HDTV and other consumer electronics. Since HDMI is transmitting digital data without compression, it eliminates signal interference and attenuation seen in traditional connection standards. HDMI connectors are compact in size and have up to 29 pins. The main design challenge is to maintain a good impedance profile (continuity) throughout multiple interconnect transitions, especially at high speed data rates.
To model connector impedance, the first step is to model a 100 Ohm differential pair on a PCB for reference. The differential pair is excited by two 50 Ohm +1V/-1V differential signal sources to test impedance. If the TDR signal maintains 0.5 V on each source and then jumps to 1V, it is a good 100 Ohm differential pair.
Figure 1: Modeling a reference differential pair in EMPro
The next step is to import the connector CAD file into EMPro and align the 3D model with the differential pair from step 1.
Figure 2: Imported HDMI connector CAD file in EMPro
An FDTD simulation was run and the TDR results are shown in Figure 3. By using an NVIDIA GPU the simulation was accelerated and finished within 20 minutes and consumed about 300 MB RAM.
Figure 3: TDR results
For this application, FDTD time domain EM simulation technology is preferable to FEM frequency domain. FDTD easily provides the impedance data through the interconnect transitions. It also provides more efficient meshing to handle complex 3D structures and faster simulation when utilizing GPU acceleration.
Fast EM simulation helps identify problem areas, and discontinuities of connectors. Running multiple simulations in a fraction of the time helps you understand and optimize for a good impedance profile throughout the transitions. As a result, high performance connector designs can be achieved.