PURPOSE: To attain high-frequency transmission having excellent transmission characteristics, by compensating the delay characteristics stably even to the change in ambient temperature, through the provision of a delay equalizer compensating the delay characteristics between a frequency converter and a high frequency amplifier.

CONSTITUTION: An IF input signal is mixed with an output of a local oscillator 2 at a transmission frequency converter 1, delay-equalized 8 and amplified at an RF amplifier 3. The output is transmitted from an antenna 5 via a branching filter 4. Since the delay equalizer 8 compensating the delay of the filter 4 is provided between the converter 1 and the amplifier 3, the types of materials of constituting elements are the same and the temperature coefficient is the same. Thus, the deterioration in the compensation effect of the delay characteristics is not almost caused even if the ambient conditions are changed.