A 3-port dielectric phase shifting unit, comprising: a feeding network, which comprises: a first end, a second end opposite to the first end, and an input port disposed at the first end on the feeding network; and a dielectric plate (6b, 4) for impedance matching and for moving along a predetermined path, which comprises: a first end, a second end opposite to the first end of the dielectric plate (6b, 4), a first matching hole (3b, 2), and a second matching hole (4b, 3), wherein the first end of the dielectric plate is closer to the first end of the feeding network than the second end of the feeding network, and the first matching hole (3b, 2) is larger than the second matching hole (4b, 3); wherein the first matching hole (3b, 2) is defined at the first end of the dielectric plate and close to the input port (2b, 1); the second matching hole (4b, 3) is also defined at the first end of the dielectric plate but further away from the input port (2b, 1) and said first end of the dielectric plate than the first matching hole (3b, 2); wherein the first matching hole (3b, 2) is disposed between said first end of the dielectric plate and the second matching hole and the first matching hole (3b, 2) and second matching hole (4b, 3) together define an impedance matching portion; wherein the feeding network further comprises a first output port (1b, 5) and a second output port (5b, 6) respectively connected to the input port (2b, 1) through a power divider, wherein the first output port (1b, 5) is disposed near the input port (2b, 1) and the second output port (5b, 6) is disposed further away from the input port (2b, 1) than the first output port (1b, 5), and wherein a network branch from the power divider to the first output port (1b, 5) is not covered by the dielectric plate (6b, 4) and another network branch from the power divider to the second output port (5b, 6) is covered by the dielectric plate (6b, 4). a feeding network, which comprises: a first end, a second end opposite to the first end, and an input port disposed at the first end on the feeding network; and a dielectric plate (6b, 4) for impedance matching and for moving along a predetermined path, which comprises: a first end, a second end opposite to the first end of the dielectric plate (6b, 4), a first matching hole (3b, 2), and a second matching hole (4b, 3), wherein the first end of the dielectric plate is closer to the first end of the feeding network than the second end of the feeding network, and the first matching hole (3b, 2) is larger than the second matching hole (4b, 3); wherein the first matching hole (3b, 2) is defined at the first end of the dielectric plate and close to the input port (2b, 1); the second matching hole (4b, 3) is also defined at the first end of the dielectric plate but further away from the input port (2b, 1) and said first end of the dielectric plate than the first matching hole (3b, 2); wherein the first matching hole (3b, 2) is disposed between said first end of the dielectric plate and the second matching hole and the first matching hole (3b, 2) and second matching hole (4b, 3) together define an impedance matching portion; wherein the feeding network further comprises a first output port (1b, 5) and a second output port (5b, 6) respectively connected to the input port (2b, 1) through a power divider, wherein the first output port (1b, 5) is disposed near the input port (2b, 1) and the second output port (5b, 6) is disposed further away from the input port (2b, 1) than the first output port (1b, 5), and wherein a network branch from the power divider to the first output port (1b, 5) is not covered by the dielectric plate (6b, 4) and another network branch from the power divider to the second output port (5b, 6) is covered by the dielectric plate (6b, 4).