| 摘要 |
The present invention is an RF cancellation circuit located between the output of a power amplifier and downstream circuitry, such as a transmitting antenna. The RF cancellation circuit cancels reflections resulting from antenna impedance mismatches, thereby presenting a constant load impedance to the output of the power amplifier. The RF cancellation circuit extracts a portion of the reflected signal, phase-shifts by 180 degrees and amplifies the extracted portion of the reflected signal to create a cancellation signal, and then cancels the balance of the reflected signal by adding in the cancellation signal. Directional circuitry is used to process the reflected signals without interfering with normal transmitted signals. Presenting a constant load impedance to the output of the power amplifier helps facilitate compliance with total radiated power into load mismatch specifications.
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