Adjustable directional coupler circuit

A correction circuit for a directional coupler comprising an input port configured to receive an input signal, an output port configured to output the input signal to a load, a forward coupled port configured to output a first coupled signal comprising a desired first coupled signal proportional to forward power of the input signal and an extraneous first coupled signal proportional to reverse power of a reflected signal corresponding to a portion of the input signal reflected from the load, and a reverse coupled port configured to output a second coupled signal comprising a desired second coupled signal proportional to the reverse power of the reflected signal, the correction circuit comprising:

• a first adjustable gain component configured to adjust a magnitude of the second coupled signal output from the reverse coupled port;
• a first adjustable phase shifter configured to adjust a phase of the second coupled signal to provide an adjusted second coupled signal;
• and
• a first summing circuit configured to add the adjusted second coupled signal and the first coupled signal at the forward coupled port in order to cancel the extraneous first coupled signal,
• wherein the first adjustable gain component and the first adjustable phase shifter are adjustable in response to a frequency of the input signal.

An adjustable directional coupler, comprising:

• a first port configured to receive an input signal from a signal source;
• a second port configured to output the input signal to a load;
• a third port configured to output a first coupled signal comprising a desired first coupled signal proportional to forward power of the input signal flowing from the first port to the second port and an extraneous first coupled signal proportional to reverse power of a reflected signal flowing from the second port to the first port, the reflected signal corresponding to a portion of the input signal reflected from the load;
• and
• a fourth port configured to output a second coupled signal comprising a desired second coupled signal proportional to the reverse power and an extraneous second coupled signal proportional to the forward power;
• and
• a correction circuit configured to adjust magnitude and phase of a sample of the second coupled signal to provide an adjusted second coupled signal, and to sum the adjusted second coupled signal and the first coupled signal at the third port to cancel the extraneous first coupled signal, wherein the magnitude and the phase are adjusted as a function of frequency of the input signal, and adjustment amounts for adjusting the magnitude and the phase, respectively, are previously set for each of a plurality of frequencies of the input signal by calibrating the settings at the plurality of frequencies.