Weakly coupled based harmonic rejection filter for feedback linearization power amplifier
View Patent ↗Radio frequency (RF) filters configured to filter undesired signal components (e.g., noise and harmonics) from RF signals are disclosed. In one embodiment, an RF filter includes a first inductor coil having a first winding and a second inductor coil having a second winding and a third winding. The second winding of the second inductor coil is configured to have a first mutual magnetic coupling with the first winding, while the third winding of the second inductor coil is configured to have a second mutual magnetic coupling with the first winding. The second winding is connected to the third winding such that the first mutual magnetic coupling and the second mutual magnetic coupling are in opposition. In this manner, the first inductor coil and the second inductor coil may be provided in a compact arrangement while providing weak mutual magnetic coupling between the first inductor coil and the second inductor coil.
1. A radio frequency (RF) filter comprising:
a first inductor coil having a first winding and configured to:
have a mutual electric coupling with a second inductor coil and generate an electric flux in response to an RF signal, such that the electric flux substantially transfers the RF signal to the second inductor coil; and
the second inductor coil having a second winding and a third winding, wherein:
the second winding is configured to have a first mutual magnetic coupling with the first winding of the first inductor coil;
the third winding is configured to have a second mutual magnetic coupling with the first winding of the first inductor coil; and
the second winding is connected to the third winding such that the first mutual magnetic coupling and the second mutual magnetic coupling are in opposition to substantially cancel an aggregate mutual magnetic coupling between the first inductor coil and the second inductor coil.
2. The RF filter of claim 1 wherein:
the first winding of the first inductor coil is configured to generate a magnetic flux in response to the RF signal; and
the second winding and the third winding of the second inductor coil are connected such that the magnetic flux induces opposing electromotive induction in the second winding and the third winding so that the first mutual magnetic coupling and the second mutual magnetic coupling are in opposition.
3. The RF filter of claim 2 wherein the second winding and the third winding of the second inductor coil are configured such that the first mutual magnetic coupling cancels the second mutual magnetic coupling.
4. The RF filter of claim 1 wherein:
the second winding is wound in a first rotational direction; and
the third winding is wound in a second rotational direction that is opposite of the first rotational direction.
5. The RF filter of claim 1 wherein:
the first winding defines a plane and has a perimeter;
the second winding is configured such that a first projection of the second winding onto the plane is within the perimeter of the first winding; and
the third winding is configured such that a second projection of the third winding onto the plane is within the perimeter of the first winding.
6. The RF filter of claim 5 wherein the second winding and the third winding are in the plane defined by the first winding and within the perimeter of the first winding.