Extended bandwidth RF amplifier

An amplifier system comprising:

• (a) a first quadrature coupler, having a coupled pass band over its operating frequency range, comprising a first and a second input port, and a first and a second output port, said first input port being directly connected to the second output port by means of a direct through-line through said coupler, and said second input port being designated as an isolated port of said first coupler,
• (b) a second quadrature coupler having a coupled passband over its operating frequency range which overlaps at least a portion of the coupled pass band of said first quadrature coupler, comprising a first and a second input port and a first and a second output port, said second input port being directly connected to said first output port by means of a through-line through said second coupler, and said second output port being designated the isolated port of said second coupler,
• (c) a first amplifier having an input port and an output port and a passband that overlaps and exceeds that of said first and second quadrature couplers,
• (d) a second amplifier having an input port and an output port, and a passband that at least equals that of said first amplifier,
• (e) means for providing the following connections:
• (1) the input port of the first amplifier to the first output port of the first quadrature coupler,
• (2) the output port of the first amplifier to the first input port of the second quadrature coupler,
• (3) the input port of the second amplifier to the second output port of the first quadrature coupler,
• (4) the output port of the second amplifier to the second input port of the second quadrature coupler,
• (f) a first phase shifter connected directly in series with said first amplifier, and
• (g) a second phase shifter connected directly in series with said second amplifier, said second phase shifter having a phase difference from said first phase shifter of nominally one-hundred-and-eighty degrees to enable a signal applied to an input port of the first quadrature coupler to pass through both quadrature couplers via both amplifiers in the overlapping portion of the operating frequency range of the quadrature couplers and to pass through a direct path formed of the electrical path through the through-line of the first quadrature coupler, the second phase shifter, the second amplifier, the through-line of the second quadrature coupler to the first output port of the second coupler when said signal is outside the overlapping portion of the operating frequency range of said quadrature couplers, said signal being able, when within the overlapping portion of the operating frequency range, to pass through a coupled path formed of the electrical path through a coupled-line of the first quadrature coupler, the first phase shifter, the first amplifier, a coupled line of the second quadrature coupler to the first output port of the second coupler.