Radio frequency transmit/receive switch with coupled transmission lines

A transmit-receive switch configurable between a receive mode and a transmit mode comprising:

• a receive port for outputting received radio-frequency signals;
• a transmit port for receiving radio-frequency signals to transmit;
• an antenna connected to the receive port through a receive path and a first coupled transmission line comprising a first pair of spaced apart transmission lines that galvanically isolates the receive path from the antenna, the antenna also connected to the transmit port through a transmit path and a second coupled transmission line comprising a second pair of spaced apart transmission lines that galvanically isolates the transmit path from the antenna;
• and
• a receiver switch connected to the receive path and configured to selectively present an open circuit to the receive path when the transmit-receive switch is in the receive mode and a short circuit to ground when the transmit-receive switch is in the transmit mode;
• and
• a transmitter switch connected to the transmit path and configured to selectively present an open circuit to the transmit path when the transmit-receive switch is in the transmit mode and short circuit to ground when the transmit-receive switch is in the receive mode.

A radio-frequency (RF) switching circuit comprising:

• a receive port connected to a balanced side of a receive balun;
• a transmit port connected to a balanced side of a transmit balun;
• an antenna coupled to an unbalanced side of the receive balun through a first coupled transmission line, the antenna also coupled to an unbalanced side of the transmit balun through a second coupled transmission line;
• and
• a first field-effect transistor connected to the first coupled transmission line and the unbalanced side of the receive balun at a receive path node, where in the first field-effect transistor is configured to selectively present an open circuit to the receive path node when the RF switching circuit is in a receive mode or a short circuit to the receive path node when the RF switching circuit is in a transmit mode;
• and
• a second field-effect transistor connected to the second coupled transmission line and the unbalanced side of the transmit balun at a transmit path node, where in the second field-effect transistor is configured to selectively present an open circuit to the transmit path node when the RF switching circuit is in the transmit mode or a short circuit to ground when the RF switching circuit is in the receive mode.