1. Introduction
Automotive radar applications generally involve two types of radar, long-range radar (LRR) and short-range radar (SRR), which are able to detect targets within a range of around 100 and 10m, respectively[1]. An LRR has been developed at millimeter wave band e.g., 76 GHz band using FM-CW, chirp, 2CW, and spread spectrum technologies. However, the LRR at 76 GHz band has not been widely used because of the expensive hardware. It also has not sufficient short-range resolution. Vehicular radars using ultra-wideband (UWB) are expected to be SRRs at sub-millimeter wave band e.g., 22–29 GHz band, and are capable of detecting both the distance to, and angle of the target[2] at a high resolution.