A sensor board for transmitting and receiving directional radar signals including a non-conductive substrate having a plurality of first recesses distributed at intervals along at least one edge of the non-conductive substrate; a microwave oscillator including an RC oscillator circuit and a transistor Q1; an anti-coupling foil; a first filter circuit configured to filter an input power Vcc; a second filter circuit configured to filter an output signal; a receiving antenna; and a transmitting antenna including a first wire laid over the plurality of first recesses along the edge of the non-conductive substrate; and a plurality of first electrically conductive protrusions embedded in the first recesses, the first wire electrically connecting the first electrically conductive protrusions.