Integrated communication and radar scheme for future intelligent transportation systems

This PhD thesis presents comprehensive study and development of integrated communication and radar systems (iCars) based on a single transceiver platform for future intelligent transportation systems (ITSs). Following a broad and in-depth literature review, first of all, a novel modulation scheme is proposed in this work, in which radar and communication signals are arranged in sequential time slots of one operation cycle and therefore, their interference is minimized. Also, time-agility or flexible functional reconfiguration can be easily achieved by adaptively or cognitively adjusting all software-programmable time durations in the modulation waveform according to usage situations. Moreover, functional fusion between two operation modes can be made possible from the following two aspects. One is that targets' ranges and velocities obtained through the radar mode can be used in the communication mode to mitigate multipath fading and compensate the Doppler spreading effect caused by the mobility of onboard units. The other is that by making use of the communication features, different onboard transceivers can exchange data such as targets' range and velocities, which in fact forms a radar network with range increment and accuracy enhancement of target finding. Finally, the proposed modulation waveform is advantageous from a networking perspective since a specific time slot can be assigned to each unit in the same service cell on the basis of a time division multiple access (TDMA) while different service cells can use different frequencies for data transmission based on the frequency division multiple access (FDMA). In order to prove our proposed system concept, a low-frequency system demonstrator has been built in the 5.9-GHz band assigned by the U.S. federal communications commission's (FCC's) for dedicated short range communication (DSRC) applications. Based on the FCC's rules and practical requirements of automotive applications, system specifications are defined and then link budget analysis is performed for both radar and communication modes in order to provide theoretical insight into system functionality and understand special design considerations. Conventional heterodyne transceiver architecture is modified to adapt our proposed modulation waveform. Subsequently, the entire system is modeled and analyzed in a commercial simulation package in order to find out achievable system performance as well as perform system optimization. On the basis of careful system analysis and simulation, the proposed low-frequency system prototype is built with commercial off-the-shelf components, and experiments are carried out to evaluate system performance for both radar and communication modes. Measured bit-error-rate (BER) in the communication mode agrees very well with theoretical values, and measured detection ranges and velocities in the radar mode exhibit very small error compared to the predefined values in the channel emulator. For enhancing data rate in the communication mode and range resolution in the radar mode, another high-frequency system has been designed and prototyped in the 24-GHz industrial, scientific and medical (ISM)-band with the help of the emerging substrate integrated waveguide (SIW) technology, which has presented multiple advantages such as low cost, high quality-factor (high- Q) and versatile compatibility with standard printed circuit board (PCB) process. In this 24- GHz system, a number of innovative SIW passive components including wideband couplers, broadband phase shifters and highly-selective filters have been proposed together with novel design and synthesis method by virtue of numerical calibration techniques. In particular, an accurate and efficient method has been proposed to synthesize four-line interdigitated (Lange) coupler. Moreover, a fundamental modeling strategy has also been proposed to characterize and establish equivalent circuit models of mutual couplingof any orders and this modeling technique is then applied in the design of a pair of 8×8 microstrip array at 24 GHz. Finally, by integrating our developed SIW passive components with commercial off-the-shelf active devices, the entire 24-GHz system is designed and prototyped onto a single substrate. Experimental results show very promising system performance for both high speed data communication and high accuracy target detection. (Abstract shortened by UMI.)

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