Polyphase filter with interphase coupling

An apparatus for filtering a signal, the apparatus comprising:

• a polyphase filter comprising:
• a direct-current (DC) bias voltage node;
• a plus in-phase filter unit comprising an input node, an output node, and a control node;
• a minus in-phase filter unit comprising an input node, an output node, and a control node;
• a plus quadrature-phase filter unit comprising an input node, an output node, and a control node;
• a minus quadrature-phase filter unit comprising an input node, an output node, and a control node;
• a plus in-phase switch coupled to the control node of the plus in-phase filter unit, the DC bias voltage node, and both of the input node of the plus quadrature-phase filter unit and the input node of the minus quadrature-phase filter unit;
• and
• a minus in-phase switch coupled to the control node of the minus in-phase filter unit, the DC bias voltage node, and both of the input node of the plus quadrature-phase filter unit and the input node of the minus quadrature-phase filter unit,
• the plus in-phase switch configured to selectively couple the DC bias voltage node, the input node of the plus quadrature-phase filter unit, or the input node of the minus quadrature-phase filter unit to the control node of the plus in-phase filter unit;
• and
• the minus in-phase switch configured to selectively couple the DC bias voltage node, the input node of the plus quadrature-phase filter unit, or the input node of the minus quadrature-phase filter unit to the control node of the minus in-phase filter unit.

An apparatus for filtering a signal, the apparatus comprising:

• at least one antenna;
• a wireless interface device coupled to the at least one antenna and comprising a polyphase filter, the polyphase filter comprising:
• a direct-current (DC) bias voltage node;
• a plus in-phase filter unit comprising an input node, an output node, and a control node;
• a minus in-phase filter unit comprising an input node, an output node, and a control node;
• a plus quadrature-phase filter unit comprising an input node, an output node, and a control node;
• a minus quadrature-phase filter unit comprising an input node, an output node, and a control node;
• a plus in-phase switch coupled to the control node of the plus in-phase filter unit, the DC bias voltage node, and one or both of the input node of the plus quadrature-phase filter unit and the input node of the minus quadrature-phase filter unit;
• and
• a minus in-phase switch coupled to the control node of the minus in-phase filter unit, the DC bias voltage node, and one or both of the input node of the plus quadrature-phase filter unit and the input node of the minus quadrature-phase filter unit;
• a display screen;
• and
• at least one processor operatively coupled to the display screen and the wireless interface device, the at least one processor configured to present one or more graphical images on the display screen based on one or more wireless signals received via the at least one antenna using the polyphase filter of the wireless interface device.

A filter, comprising:

• a first filter unit comprising a first input node, a first output node, a first capacitor coupled between the first input node and ground, a first current source coupled to the first input node, and a first transconductor coupled between the first current source and the first output node, the first input node being coupled to a first mixer configured to provide a first phase signal component, the first current source comprising a transistor having a drain coupled to the first transconductor, a source coupled to a power distribution network node, and a gate;
• a second filter unit comprising a second input node, a second output node, a second capacitor coupled between the second input node and ground, a second current source coupled to the second input node, and a second transconductor coupled between the second current source and the second output node, the second input node being coupled to a second mixer configured to provide a second phase signal component;
• and
• means for selectively coupling the gate of the transistor to the second input node and for selectively coupling the gate of the transistor to a bias.

A method for operating at least one polyphase filter, the method comprising:

• propagating a plus in-phase signal component through a plus in-phase filter unit that comprises a control transistor;
• propagating a minus in-phase signal component through a minus in-phase filter unit that comprises a control transistor;
• propagating a plus quadrature-phase signal component through a plus quadrature-phase filter unit that comprises a control transistor;
• propagating a minus quadrature-phase signal component through a minus quadrature-phase filter unit that comprises a control transistor;
• selectively coupling the plus quadrature-phase signal component or the minus quadrature-phase signal component to a control terminal of the control transistor of the plus in-phase filter unit;
• and
• selectively coupling the plus quadrature-phase signal component or the minus quadrature-phase signal component to a control terminal of the control transistor of the minus in-phase filter unit.