A novel power line detection method exploiting the Bragg point of power line is proposed in this paper. First, the radar echo of power line is divided into multi-band along the frequency dimensional with incomplete repetition at equal intervals. Then, the candidate power lines in the echo of each frequency band can be found exploiting the Hough transform and constant false alarm rate (CFAR). Since the Bragg angle of the power line will change with frequency while that of the artefacts is fixed, the power lines can be easily detected from the background by exploiting unique frequency feature of Bragg angle of power line.

The big threat to helicopters flying at low altitudes is power line, that leads many collision accidents. Due to the small size of power line from others, it is difficult for pilots to detect it from a distance using the visual or optical devices. Since the high speed, heavy mass and poor mobility of large helicopters, it requires a long time and distance for early warning. Considering the good ability of all-weather detecting and better atmospheric penetration than the laser, it can be applied to detect power line for millimeter-wave radar. In this paper, we first carry out the power line echo simulation to characterize the backscattering of power line. As a result, a power line detection method through semantics segmentation is proposed. The results show that our method can improve the detection rates and provide a better performance on the anti-ground clutter performance.

The existing methods for calculating electromagnetic scattering can be used to obtain the RCS of power lines. However, these methods do not take advantage of the periodicity of power lines. We propose a fast electromagnetic scattering calculation method combining the integral equation discontinuous Galerkin (IEDG) method and the characteristic modes-Sherman–Morrison–Woodbury algorithm (CM-SMWA) exploiting the power lines with stranded structure. We adopt the IEDG to discretize the electric field integral equation (EFIE) so that the EFIE can deal with non-conformal grids and significantly increase the flexibility of the CM-SMWA. Combing with the periodic property of power lines, the modeling and grid generation shall be carried out within one cycle (stranding) of the power line, and the grids of the rest cycle of the power line can be spliced by translating the grid of the divided sections. The advantage of the proposed method lies in that only the CM of one segment needs to be calculated, and the result can be applied to other segments to avoid repeated calculation of the CMs. The simulation results of the RCS of power lines show that the calculation time of our method is cut down by 50% as compared to the conventional CM-SMWA.

Power lines are the biggest threat to helicopters flying at low altitudes, so the detection of power lines is of great significance to helicopter safety. This paper proposes a Bragg feature detection method for power lines based on broadband Bragg features. The method first obtains radar echo data through FMCW broadband data of power lines. Then, the FMCW data is segmented, radar echoes of different frequency bands are formed by distance FFT, and the characteristic points of the candidate power lines echoed in different frequency bands are accurately measured. Finally, through the angle changes of different frequencies, it is confirmed whether it is the Bragg point of the power line, and then the Bragg point characteristics of the power line are identified. This is conducive to solving the problem of false alarms and errors associated with power lines under complex conditions.

The radar cross-section (RCS) of power lines has an important significance for detection of the power lines. The method of moments (MoM) can calculate the RCS of power lines. However, the efficiency of the MoM is limited by the time-consuming computing process, as well as the expensive storage overhead. In order to enhance the efficiency and reduce the storage of the RCS calculation of power lines, we propose an RCS calculation method that combines the characteristic mode (CM) with a Sherman–Morrison–Woodbury formula-based algorithm (SMWA), which is referred to as a CM-SMWA. CMs are used as the basis functions for reducing the dimension of the MoM impedance matrix, and the SMWA is applied to directly solve the CMs-reduced matrix equation, which can reduce the computational time and storage. The numerical results demonstrate that the proposed method can obtain the RCS of power lines, with different incident angles and different polarizations, at a higher efficiency. At 35 GHz, compared with the conventional MoM, for a typical LGJ50-8 power line with a length of 0.276 m, the computation time is reduced by 62.4% and the memory occupation is reduced by 96.4%.