| 摘要 |
PURPOSE:To attain light weight and small size of a radio transmission/reception equipment by adding respectively a tuning circuit to each end of a loop antenna and constituting each of a tunning circuit so as to form the synthesized resonance frequency for the loop antenna and the tuning circuit into two different frequencies thereby sharing one loop antenna for different frequencies. CONSTITUTION:Series-parallel resonance circuits, 3, 3' comprising a coil L1, capacitors C1, C2 and a coil L2, capacitors C3, C4 respectively are connected to both ends 2, 2' of the loop antenna element 1. Further, the resonance frequency of the two resonance circuits 3, 3' and the loop antenna element 1 in total three components is two desired frequencies f1, f2 and the circuit element is decided so that the impedance of input/output terminals 4, 4' tapped down by capacity division of the resonance circuits 3, 3' becomes the input/output impedance of the transmission reception circuit to be connected to them, e.g., 50OMEGA. Thus, in connecting a receiver of the reception frequency f1 to the input/ output terminal 4 of the resonance circuit 3 and the transmitter using the transmission frequency f2 of the resonance circuit 3' respectively, one antenna is used as the shared antenna of the transmission and reception equipment having different frequencies from each other. |
