![]() ![]() Bogdan Adamczyk, Foundations of Electromagnetic Compatibility with Practical Applications, Wiley, 2017.ĭr.Bogdan Adamczyk and Dimitri Haring, “ EMC Filters Comparison Part I: CL and LC Filters,” In Compliance Magazine, January 2020.Insertion losses of the LC filter and T filters are virtually identical.Note: These conclusions are based on the filter study with the source impedance of 50 Ω, load impedance of 1 kΩ, and the component values L = 4.7 µH, C = 10 nF. Since the LC filter contains one fewer inductor, it should be chosen over the T filter.Ĭonclusions of the filter studies in Part I and Part II It is apparent that the LC and T filter insertion losses are very similar. Figure 13: Insertion loss (s 21 and s 34) measurements of the two configurations shown in Figure 11 Figure 12: Insertion loss of the two configurations shown in Figure 11įigure 13 shows the measurement results for the two configurations shown in Figure 11 and simulated in Figure 12. Figure 11: LC and T filter configurationsįigure 12 shows the insertion loss of the two filter configurations. Let’s compare these two filters.įigure 11 shows the LT spice simulation schematic. The insertion loss curve of the LC filter looks similar to the insertion loss curve of the T filter. At 10 MHz the difference between the simulated insertion losses of the two filters is 29.78 dB which is close to the measured difference of 28.02 dB. The measurement results are consistent with the simulation results. Figure 10: Insertion loss (s 21 and s 34) measurements of the two configurations shown in Figure 8 The insertion loss of the π filter at 10 MHz is about 29.78 dB higher than that of the LC filter.įigure 10 shows the measurement results for the two configurations shown in Figure 8 and simulated in Figure 9. Figure 9: Insertion loss of the two configurations shown in Figure 8Īs can be seen from Figure 9, the π filter outperforms the LC filter (except for a small range of frequency around the resonance point at 1 MHz). Figure 8: LC and π filter configurations – low impedance source, high impedance loadįigure 9 shows the insertion loss of the two filter configurations. Figure 8 shows the LT spice simulation schematic. Next, let’s compare the insertion loss of the π filter with the insertion loss of the LC filter discussed in Part I. Table 2: Simulated and measured insertion loss for T filter Table 1: Simulated and measured insertion loss for π filter In the frequency range 100 kHz – 10 MHz the simulated and measured results are remarkably close, as summarized in Tables 1 and 2. Figure 7: Insertion loss (s 21 and s 34) measurements of the two configurations shown in Figure 3 Figure 6 shows a close-up of the two PCB filter boards used in this measurement.įigure 6: T and π filters used for measurementsįigure 7 shows the measurement results for the two configurations shown in Figure 3 and simulated in Figure 4. ![]() Since a four-channel network analyzer was used, we could evaluate the two different filter configurations simultaneously. Figure 5: EMC filter VNA measurement setup To verify the simulations results the measurement setup shown in Figure 5 was used. This is consistent with the general rule that the inductor should be placed on the low-impedance side and the capacitor on the high-impedance side. The insertion loss of the π filter at 10 MHz is about 29.5 dB higher than that of the T filter. Figure 4: Insertion loss of the two configurations shown in Figure 3Īs can be seen from Figure 4, the π filter outperforms the T filter (except for a small range of frequency around the resonance point at 1 MHz). ![]() The filter configurations are tested with 1 kΩ impedance on the load side.įigure 4 shows the insertion loss of the two filter configurations. The measurement made by the network analyzer at Port 2 is across its internal 50 Ohm impedance. Verification via Simulations and Measurements π and T Filter Comparisonįigure 3 shows the LT spice simulation schematic. The 50 Ohm source impedance is provided by the network analyzer at Port 1. Figure 2: π and T filters: source impedance low and load impedance highįigure 3: T and π filter configurations – low impedance source, high impedance load ![]()
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