Question

6.1.1 In order to illustrate that the LISN essentially presents 50Ω impedances between phase and ground and between neutral and ground, use PSPICE to plot the frequency response of the impedance looking into one side of the LISN shown in Fig. P6.1.1 over the conducted emission frequency range of 150 kHz-30 MHz for two cases of impedance seen looking into the power net: (1) short-circuit load and (2) open-circuit load. Determine the values at each end of the frequency band. [Short-circuit: 38.31 2 and 47.62 Ω; open-circuit. 37.85 Ω and 47.62 Ω 50 HH Short Open 50 Ω FIGURE P.6.1.1

Answer 1

Consider the circuit. 50 μΗ 0.1 HF Short 1 F Open 50 Ω 1 kn Draw the circuit in SPICE with load open (high resistance). L1 50u C2 0.1u V12 R24 1Vac 100MEG oVdc C1 1u R22 R23 50 1k Perform frequency analysis for the frequency in the range 150 kHz to 30 MHz OrCAD Capture CIS - Lite- [/ - (SCHEMATIC1: PAGE2)] File Design Edit Vieu Tools Place S Analysis PSpice Accessories Options Window Help Simulation Settings- m2 Configuration Files Data Collection Probe Window General Analysis Options AC Sweep Type Analysis Type: AC Sweep/Noise O Linear Start Frequency: 150k Options: OLogarithmic End Frequency 30Meg Total Points: General Settings 100000 Decade Monte CarloWorst Case Parametric Sweep Noise Analysis Enabled Output Voltage: Temperature (Sweep) N Source Save Bias Interval: int Load Bias Point Output File Options Include detailed bias point information for nonline ar controlled sources and semiconductors (OP) Cancel Ok Apply Reset Help

Obtain the simulation output 48 46+ A4- 42- 40- 384 36+ 20MHZ 5MHZ 10MHZ 15MHZ 25MHZ 30MHZ OHz 1/ I (V12) Observe that for an open-circuit, the impedance the lower end is 37.8 ohms and the impedance at the higher end is 47.6 ohms Draw the circuit in SPICE with load short-circuited (zero resistance) L1 50u C2 0.1u V12 R24 1Vac 0.1 oVdc C1 1u R22 R23 50 1k C w

Obtain the simulation output. 48- 46 44 42- 40- 38+ OHz 5MHZ 10MHZ 15MHZ 20MHZ 25MHZ 30MHZ 1/1 (V12) Frequency Observe that for a short-circuit, the impedance the lower end is 38.3 ohms and the impedance at the higher end is 47.6 ohms.