| 摘要 |
<p>PROBLEM TO BE SOLVED: To apply a reverse voltage to an off side high frequency switch to suppress the high frequency distortion and to reduce current consumption by controlling the operation of the high frequency switch dividing plural signal paths by control power supply respectively provided in a transmitting part and a receiving part. SOLUTION: When a DCS system of a dual band portable telephone set is transmitted, a control voltage 3 V is applied from a transmitting part side control power supply Vc1d of DCS system high frequency switch 13a and a receiving part side control power supply Vc2g of a GSM system high frequency switch 14a, and voltage 0 V is also applied from a receiving part side control power supply Vc2d of the switch 13a and from a transmitting part side control power supply Vc1g of the switch 14a. Thus, a forward current is caused to flow to D1 and D2 of the switch 13a to turn on the switch 13a, and a reverse voltage is applied to G1g and D2g of the switch 14a to turn off the switch 14a so that a signal can be prevented from sneaking from the GSM system. In the case of transmission of the GSM system or reception in each system, a signal of another system is similarly prevented from sneaking by appropriately applying a control voltage.</p> |
