Fig. 1. Terahertz band range

Fig. 2. Time-domain reflection signals under different faults^[26]

Fig. 3. Schematic diagram of time-domain reflection of terahertz pulses

Fig. 4. Microstrip circuit wire design diagrams (unit: mm). (a) Straight metallic wire; (b) metallic wire with branching lines; (c) square metallic spiral wire; (d) physical microstrip circuit

Fig. 5. Distribution of electric/magnetic field lines in the cross-section of metallic microstrip line

Fig. 6. Time-domain reflection signals of straight metallic wires with different lengths. (a) Straight metallic wire with length of 5 mm; (b) straight metallic wire with different lengths

Fig. 7. Reflected signals from the samples with 50 mm long main conductor and branch lines. (a) A sample with one branch line; (b) a sample with 2 branch lines; (c) samples with 2 and 3 branch lines

Fig. 8. Reflected signals from the samples with 100 mm long main conductor and branch lines. (a) A sample with 1 branch line; (b) a sample with 2 branch lines; (c) samples with 2 and 3 branch lines

Fig. 9. Time-domain reflection signal of continuously bent wire

Fig. 10. Error analysis. (a) Unevenness detection error versus length for different types of wires; (b) microscopic image of microstrip line

Fig. 11. Simulation of the inhomogeneity of different types of microstrip lines. (a) Different lengths of straight lines; (b) microstrip lines with different numbers of T-branch lines and different lengths of main conductor; (c) continuously bent line

Fig. 12. Microstrip line impedance discontinuity equivalent circuit. (a) T-branch line and its equivalent circuit; (b) bent wire and its equivalent circuit