| 摘要 |
<p>PURPOSE: TO improve the efficiency of antennas to considerably improve S/N by selecting antennas for scanning of transmission and that of reception independently of each other at the time of transmission and reception. CONSTITUTION: A selecting circuit which selects one of plural antennas, a transmission/reception switching circuit which connects the selected antenna to a transmission circuit or a reception circuit, a connection control circuit which controls these operations, and a discriminating circuit which discriminates and transmits the position and the state of a switch in accordance with the reception signal characteristic are provided-One antenna estimated to be closest to the position indicator by the connection control circuit is selected to perform the transmission at the time of transmission, and all antennas are scanned at the time of receiving the ratio wave returned from the position indicator, thereby obtaining the signal characteristic distribution required for coordinate detection. Since the radio wave arrives in a range wider than a conventional method, antennas can be designed at wider intervals of arrangement, and as the result, the number of antennas is reduced.</p> |
