Radio frequency circuit, control circuit for maintaining the output power of radio frequency signal at a predetermined level and method thereof

摘要

The circuit for maintaining the magnitude of the radio frequency (RF) signal at at least one predetermined level comprises a detection circuit 16 connected to the RF signal generator 22 by a 4-port coupling device 12. In one embodiment of the invention, an impedance inverter 30 in series with the diode D3 is connected between the load termination L of the coupling circuit 12 and ground. As the output signal power approaches the predetermined lower limit threshold, the series connection of the impedance inverter and the diode becomes closer to a short circuit. As the output signal power approaches the predetermined upper limit threshold, the series connection of the impedance inverter and the diode becomes closer to the open circuit, The gain is provided for the signal received by the detection circuit and the attenuation is provided for the signal received by the detection circuit above the second amplitude level. Since the transmission level detection circuit of the present invention requires a lower power than the conventional circuit, a 1%-2% or less of the amplifier output is required for reliable operation at an RF output level of several milliwatts It only needs to be.