Transmission Line Noise Source Simulation with CST

This article demonstrates the simultaneous excitation of arbitrary waveforms at a number of different ports. A noise source in the form of a loop circuit is place above an IC package and the influence of the noise source on the transmission of differential signals in the IC feed tranmssion lines is investigated. Two frequency ranges were simulated, 1-10 GHz and 1-20 GHz. The simulations were carried out using the simultaneous excitation feature in CST MICROWAVE STUDIO® (CST MWS).

Figure 1: Tranmsission Line noise model created in CST MWS
Figure 1 shows the model created entirely within the user interface of CST MWS. Two waveguide ports are used to excite the structure with user-defined rectangular pulses at 2.5GHz and 3GHz (ports 2 and 4 respectively). At waveguide ports 1 and 3 the output signals record the effect of the noise source excited at discrete port 5. The noise signals applied are also user-defined over a range 1 to 10GHz and 1 to 20GHz. The plastic IC package under the source is defined as dielectric block.
The simulatenous excitation features in CST MWS allows arbitrary signals to be injected into the calculation domain with user-defined signals, amplitudes, phase shifts and time delays.

Figure 2: Input Signals at 2.5GHz(I2G), 3GHz(I3G), Noise at 10GHz(N10G) and output waveforms on the 2.5GHz (o21) and 3GHz (o41) Lines respectively
Figure 2 shows the 2.5GHz and 3GHz transmission line signals in conjunction with the 1 to 10GHz Noise source (upper graph). The lower graph shows how little the transmission signals at the out ports are distorted.

Figure 3: Input Signals at 2.5GHz(I2G), 3GHz(I3G), Noise at 20GHz(N20G) and output waveforms on the 2.5GHz (o21) and 3GHz (o41) Lines respectively
The case for the 1-20 GHz noise source is shown in figure 3 where the effect on the tranmssion signals is significant.
This article has served to show the ability of CST MWS to simulate simultaneous arbitrary signals hence permitting the realistic simulation of systems consisting of multiple time-varying sources.

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