| 摘要 |
In the level converter for radio-frequency amplifiers according to the invention, preferably broadband amplifiers for receiving antenna systems, an electronically adjustable attenuating section is in each case inserted at the inputs of the first and a following amplifier stage. By continuously changing an adjustment voltage, first the attenuation 2 of the second attenuating section can be set up to the maximum value and only then the attenuation 1 of the first attenuating section at the input of the first amplifier stage. The invention has the advantage that, due to the attenuation of the subsequent attenuating section, output levels which are too high can be lowered without noticeably reducing the signal/noise ratio and the amplifier input. It is advantageous for this purpose to select the attenuation of the subsequent attenuating section to be less than the preceding gain. It is only when this attenuation is not sufficient for avoiding cross modulation interference due to output levels which are too high, for example in a broadband amplifier which is supplied with several received signals having different levels, that all input levels are additionally decreased by the preceding attenuation. The resultant reduction in signal/noise ratio, which is disadvantageous for low received levels, is accepted.
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