In this paper a new slot array antenna with 45° inclined linear polarization for application in collision avoidance systems is presented. The proposed antenna is fed by a travelling wave and hence, in contrast with standing wave arrays, it has a wide impedance bandwidth. However, unlike conventional travelling wave arrays, it has a broadside radiation pattern at center frequency. In order to have a broadside radiation pattern, an in-phase excitation should be applied to slots. This is accomplished by properly determining the length and offset of slots which are separated one half guided wavelength from each other. Also to have a 45° polarization, inclined slots are used. Based on the presented design method, a linear array with nine slots is designed, simulated and fabricated at the center frequency of 10 GHz. Simulated and measured results are in good agreement with each other. The measured −10 dB impedance bandwidth, maximum gain, side lobe level, cross polarization discrimination and simulated radiation efficiency are >3 GHz, 13.66 dBi, 10.88 dB, 16.48 dB and 79.4%, respectively.

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