The capacitor structure shown in Figure 2.1 was realized using Low-Temperature Cofired Ceramic (LTTC) technology. An electromagnetic simulation of the capacitor structure was performed using SONNET to obtain its scattering parameters (S-parameters). EMtoSPICE was used to convert the S-parameters of the capacitor structure to a broadband SPICE model (or subcircuit). As shown in Figure 2.2, the responses of the SPICE model generated by EMtoSPICE show good agreement to the S-parameters. The simluated time-domain transmissometry (TDT) response of the SPICE model was obtained using a SPICE solver, LTSPICE, and correlated to the measured TDT response of the capacitor structure. Figure 2.3 shows the measurement setup where C is the capacitor structure under test and Zs and Zl are terminating impedances of a digital sampling oscilloscope. A 250 mV step with a rise time of 35 ps was propagated on the structure and the transmitted voltage was measured. Figure 2.4 shows the measured and simulated TDT responses of the capacitor structure. They are in good agreement.

Figure 1.1.  Capacitor layout
Figure 2.1. Layout of the resistor structure. All dimensions are in mils.

Figure 1.2.  S-parameter vs. model
Figure 2.2. S-parameters vs. the responses of the SPICE model generated by EMtoSPICE. Phase in degrees.

Figure 1.3.  Measurement setup
Figure 2.3. Measurement setup

Figure 1.4.  TDT meas vs sim
Figure 2.4. TDT measurement vs. simulation of the capacitor structure shown in Figure 2.1.