A performance comparison of RELAX and MODE for multipath height finding

To measure the height of extended targets using radar wave multipath propagation, the line-of-sight (LOS) and the longest non-line-of-sight (NLOS) echos from a coherent target must be resolved accurately. This paper compares the performance of the recursive Fourier algorithm RELAX and the Method of Direction Estimation (MODE) algorithm for the purpose of multipath height finding. The main comparison consists of determining how accurate can a target height be estimated based on the LOS and NLOS spectrum output of the RELAX and the MODE algorithm. A multipath propagation model is presented and a target height formula is derived based on Sensor-Target geometry. It is then shown from the derived height formula that the height estimation accuracy of the algorithm highly depends on the range resolution of the sensor. The RELAX and MODE algorithms are applied separately to real world data for multipath components resolving. The extracted frequency and amplitude parameters are then used to retrieve target heights. The estimated height results based on RELAX and MODE spectrum are then compared and discussed. The results show that under sufficient Signal to Noise Ratio (SNR), MODE can achieve similar performance as RELAX using lower computation costs.