A source power coupler for coupling a power source to a first transmission line and a second transmission line. DC power from the power source is conducted by the source power coupler to the first and the second transmission lines while AC signals on the first and the second transmission lines are isolated from the power source by the source power coupler. The source power coupler is comprised of an operational amplifier having a non-inverting input and an inverting input. The gate of a transistor is coupled to an output of the operational amplifier. The transistor's drain is coupled to one of the transmission lines. And the transistor's source is coupled to the inverting input of the op-amp. Thereby, a control loop is formed, which provides an AC impedance between the power source and one of the transmission lines. A resistor is coupled between the source of the transistor and the power source, and a capacitor is coupled between the non-inverting input of the op-amp and the power source. Another resistor is coupled between the non-inverting input of the op-amp one of the transmission lines. The capacitor and the second resistor provide a second control loop. This control loop provides a constant direct current voltage across the transistor.
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