We can now develop low-pass and high-pass filter sections. First consider the T-network
shown in Figure 8.9. Intuitively, we can see that this is a low-pass filter network because
the series inductors and shunt capacitor tend to block high-frequency signals while passing
low-frequency signals. Comparing with the results given in Table 8.1, we have Z1 = jωL
and Z2 = 1/jωC, so the image impedance is