| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain required attenuation when over-loaded without deteriorating the noise figure by connecting an attenuator in parallel with a reception main path via a single pole double-throw electronic switch by way of two single-throw electronic switches. SOLUTION: Each electronic switch is made up of a FET and a HEMT, and switches 3, 4 and an attenuator 5 with a switch 2 are integrated into one- chip. The length of a line being a component of the switches 3, 4 is selected sufficiently shorter than a wavelength of a passing signal and then a stray capacitance is small. In the case of usual reception, a moving arm of the switch 2 is thrown to the position of a terminal S1 and the switches 3, 4 are open. Thus, the input signal is not almost affected by the existence of the switches 3, 4 or the attenuator 5. When a signal from an electric field strength detection section in a reception section has a threshold level or over, the moving arm of the switch 2 is thrown to the position of a terminal Sn and the switches 3, 4 are closed. In this case, the signal received by the antenna 11 is accurately attenuated via the switch 3, the attenuator 5 and the switch 4, and the resulting signal is given to the reception section 9.</p> |
