Acoustic matrix filters and radios using acoustic matrix filters

A time division duplex (TDD) radio, comprising:

• a transmitter;
• a receiver;
• a filter, comprising:
• a first filter port configured for connecting to an antenna and a second filter port;
• n sub-filters, where n is an integer greater than one, each sub-filter having a first sub-filter port connected to the first filter port and a second sub-filter port connected to the second filter port;
• a first acoustic resonator connected between the first filter port and ground;
• or
• a second acoustic resonator connected between the second filter port and ground, wherein
• the first and second acoustic resonators are configured to create respective transmission zeros adjacent to a lower edge of a passband of the filter;
• and
• a transmit/receiver switch to selectively connect the second filter port to one of an output of the transmitter and an input of the receiver.