Shared-antenna interface apparatus for simultaneous transmit and receive

An apparatus comprising:

• a first quadrature coupler having first, second, third, and fourth ports;
• a second quadrature coupler having first, second, third, and fourth ports, wherein the first quadrature coupler is coupled to the second quadrature coupler such that the second port of the first quadrature coupler is coupled to the second port of the second quadrature coupler, and the third port of the first quadrature coupler is coupled to the third port of the second quadrature coupler;
• an antenna coupled to the first port of the first quadrature;
• a transmitter coupled to the third port of the first quadrature;
• a receiver coupled to the fourth port of the second quadrature coupler;
• and
• a termination impedance coupled to the first port of the second quadrature coupler.

An apparatus comprising:

• a multiple-input-multiple-output (MIMO) antenna array;
• a plurality of quadrature couplers coupled to the MIMO array;
• a plurality of receivers coupled to the plurality of quadrature couplers, wherein an individual one of the receivers of the plurality of receivers comprise:
• switches which are controllable by time varying signals;
• and
• capacitive devices coupled to the switches;
• and
• a plurality of transmitters coupled to the plurality of quadrature couplers.

A method for reducing signal interference, the method comprising:

• sending a first signal to a first port of a quadrature coupler;
• transmitting the first signal via one or more antennas coupled to a second port of the quadrature coupler;
• receiving a second signal from the second port of the quadrature coupler;
• and
• sending the second signal to a receiver via third and fourth ports of the quadrature coupler;
• and
• controlling switches of the receiver to recover the second signal.