具空間多樣性以補償地面多路徑效應之汽車防撞警示雷達設計

Abstract

本論文旨在討論路面對汽車防撞雷達造成的多重反射以干涉接收訊號，進而降低接收訊號之強度，使得偵測率下降之問題。本文提出一具地面多重路徑補償之一發二收頻率連續調變波雷達並應用在汽車防撞雷達之設計，此外，文中也提出一些汽車防撞雷達之設計及應用。 首先，介紹及討論一些常使用在車用雷達方面的雷達技術及目標物辨識方法，其波型的設計尤其重要也是討論的重點；再者，目標物辨識對雷達來說更是重要的一環；因此，探討一些常使用到的固定偵測率技術並著重於多目標物之情形；此外，目標物追蹤技術對車用雷達亦是重要的課題。 再者，為了能夠有效的描述地面對雷達波的影響，一個由射綫追蹤演算法所發轉出來的四射線模型將被提出並計算地面效應對雷達所造成的影響，由模擬的數據得知地面效應對一些常使用的車用雷達頻率24及77 GHz將造成劇烈的訊號衰減，然而本文使用一高通濾波器可以稍稍補償此訊號衰減之現象。 有鑑於地面干涉雷達波之現象，我們提出一具地面多重路徑補償之一發二收頻率連續調變波車用雷達架構以補償路面所造成之訊號衰減；在此架構之中，適當的間隔在兩接收天線之間可以使其兩天線擁有好的訊號互補效應，並配合本文所提出之最大值選擇演算法，如此一來可以有效的提升訊號與地面雜波之比例進而增加訊號偵測率。 文末，將實現此具地面多重路徑補償之一發二收之頻率連續調變波雷達並應用於24-GHz前視雷達，其量測與模擬的結果相當吻合，此架構可以有效的提升訊號強度，並提升雷達偵測率；此外，一個體積精巧並操作於24-GHz頻段之盲點偵測雷達將被提出並應用於短距離偵測之上，此設計符合ISO 17387之規範，可以大幅提升駕駛人對於盲區的保障。再者，一操作於24-GHz頻段之單車道偵測前視雷達雷達將被提出以作為前方碰撞偵測之應用，其技術將可應用在未來自動緊急煞車系統之上；最後，一高增益雙槽孔基板合成波導陣列天線將被提出並作為未來應用於77-GHz之防撞雷達應用。

This dissertation discusses a realistic road surface can cause multipath reflection, degrade the received power, and reduce detection probability for automotive radar application. A one-transmitter-two-receiver (1T2R) frequency-modulation continuous-wave (FMCW) radar architecture with spatial diversity and ground-effect compensation for automotive applications has been proposed. Besides, several vehicle collision warning radars have been developed and implemented for automotive applications. In the first stage of this dissertation, several techniques to acquire data and recognize as a target have been introduced and discussed, especially for automotive radar application. The focus is on waveform design in general and on automotive applications in particular. Target detection is an important issue for all radar systems. Therefore some Constant False Alarm Rate (CFAR) procedures are discussed which can be applied, especially in multiple target situations, to avoid masking. Additionally some tracking techniques are introduced and discussed for target recognition which have been developed for automotive applications Next, the multipath reflection caused by a road surface has been presented. A four-ray model has been introduced to estimate the received power response with a ground surface by ray-tracing technique. The power responses of multi-reflection with ground surface at 24 and 77 GHz have been investigated and discussed, which reveal the road surface leads severe power degeneration. Moreover, a Sallen-Key high pass filter has been introduced to compensate the path loss of the received power response. Based on the knowledge of multipath effect of a road surface, we further proposes a one-transmitter-two-receiver frequency-modulation continuous-wave (FMCW) radar architecture with spatial diversity and ground-effect compensation for automotive applications. In the proposed design, suitable spacing between the two receiving antennas compensated for the multipath effect of the road surface and improved the signal-to-ground-clutter ratio of the receivers at certain distances. In the last part of the dissertation, a spatial-diversity 24-GHz radar has been proposed and implemented for forward-looking application. The measurement results show a good agreement with the calculated results, which largely increase the received power and detection rate. Besides, a compact 24-GHz blind spot detection (BSD) radar has been developed for a short range warning application referring to ISO 17387 specification, which provided a good protection in the blind zone for the driver. Moreover, a single-lane-cover 24-GHz radar has also been presented to provide a forward collision warning feature, and has the potential to be applied in the Autonomous Emergency Braking (AEB) system in the future. Finally, a high gain slot-pair substrate-integrated-waveguide (SIW) antenna has been presented as a candidate for the proposed spatial-diversity architecture for 77 GHz vehicle collision warning application.