Multiple-Loop Array Antenna with Switched Beam for Short-Range Radars

This paper proposes a multiple-loop array antenna (MLAA) for short-range pulse radars in the quasi-millimeter wave frequency band. The MLAA, which consists of multiple loop elements and two detour elements, has a tilt-beam characteristic, and is small in planar size. There are two schemes included in our method of applying the MLAA to a short-range pulse radar. One is a scheme that switches the beam direction by selecting the MLAA's feed points. The other is a scheme that switches between the two MLAAs with the fixed tilt-beam characteristic, the beam directions of which are different to each other. The advantage of using the switched-beam characteristic is that the number of sensors can be reduced. In this paper, we demonstrate the MLAA with the switched beam. The MLAA with a switch circuit using PIN diodes is measured to have the characteristics of 10 dBi in gain at 26 GHz, together with an effective switched-beam characteristic.