Bridge-type filters

An apparatus comprising:

• at least one radio-frequency front-end comprising a filter circuit, the filter circuit comprising:
• a first port that is single-ended;
• a second port that is single-ended;
• a transformer comprising a first terminal, a second terminal, and a third terminal, the third terminal coupled to the second port;
• a first resonator coupled between the first port and the first terminal of the transformer;
• a second resonator coupled between the first port and the second terminal of the transformer;
• a third resonator coupled between the first terminal of the transformer and a ground;
• and
• a fourth resonator coupled between the second terminal of the transformer and the ground.

An apparatus comprising:

• a filter circuit comprising:
• a first port;
• a second port having a terminal that is coupled to a ground;
• a transformer comprising a first terminal, a second terminal, and a third terminal, the third terminal coupled to another terminal of the second port;
• first means for resonating coupled between the first port and the first terminal of the transformer, the first means for resonating comprising a first acoustic resonator having a first characteristic and a second acoustic resonator having a second characteristic, the first acoustic resonator coupled to the second acoustic resonator;
• second means for resonating coupled between the first port and the second terminal of the transformer;
• third means for resonating coupled between the first terminal of the transformer and the ground;
• and
• fourth means for resonating coupled between the second terminal of the transformer and the ground, the fourth means for resonating comprising a third acoustic resonator having a third characteristic and a fourth acoustic resonator having a fourth characteristic, the third acoustic resonator coupled to the fourth acoustic resonator.

A method for filtering signals, the method comprising:

• converting from a first signal to a first signal component and a second signal component;
• propagating the first signal component through a first resonator and across a third resonator;
• propagating the second signal component through a second resonator and across a fourth resonator;
• routing the first signal component from the third resonator to a first terminal of a transformer;
• routing the second signal component from the fourth resonator to a second terminal of the transformer;
• and
• converting, using the transformer and responsive to the routing of the first signal component and the routing of the second signal component, from differential signaling that includes the first signal component and the second signal component to single-ended signaling of a second signal.

An apparatus comprising:

• a filter circuit comprising:
• a transformer having a first inductor and a second inductor electromagnetically coupled to the first inductor, a first terminal of the second inductor coupled to an output port of the filter circuit, a second terminal of the second inductor coupled to a ground;
• a first resonator arrangement coupled between an input port of the filter circuit and a first terminal of the first inductor of the transformer, the first resonator arrangement comprising a first acoustic resonator having a first characteristic and a second acoustic resonator having a second characteristic, the first acoustic resonator coupled to the second acoustic resonator;
• a second resonator arrangement coupled between the input port and a second terminal of the first inductor;
• a third resonator arrangement coupled between the first terminal of the first inductor and the ground;
• and
• a fourth resonator arrangement coupled between the second terminal of the first inductor and the ground, the fourth resonator arrangement comprising a third acoustic resonator having a third characteristic and a fourth acoustic resonator having a fourth characteristic, the third acoustic resonator coupled to the fourth acoustic resonator.