Magnetic resonance imaging device, power amplifier module and power combiner

A power amplifier module, comprising:

• a first power amplifier for providing a first electric power;
• a second power amplifier for providing a second electric power;
• and
• a power combiner comprising:
• a first transmission line or lumped circuit element electrically connected to a first port which is configured to receive the first electric power;
• a second transmission line or lumped circuit element electrically connected between the first transmission line or lumped circuit element and a common port, wherein a first connection point is located between i) the first transmission line or lumped circuit element and ii) the second transmission line or lumped circuit element;
• a third transmission line or lumped circuit element electrically connected to a second port which is configured to receive the second electric power;
• a fourth transmission line or lumped circuit element electrically connected between the third transmission line or lumped circuit element and the common port, wherein a second connection point is located between i) the third transmission line or lumped circuit element and ii) the forth transmission line or lumped circuit element;
• and
• a balance capacitive element or balance inductive element coupled between a including a first end and a second end, wherein the first end is electrically connected to the first connection point, and the second end is electrically connected to the second connection point,
• wherein (i) an odd-mode input impedance of the first port is zero and (ii) an odd-mode input impedance of the second port is zero, such that a voltage at the first port is equal to a voltage at the second port when a current flowing through the first port and a current flowing through the second port are unbalanced.

A magnetic resonance imaging (MRI) system, comprising:

• a main magnet for generating a main magnetic field;
• a gradient coil assembly;
• a gradient amplifier for exciting the gradient coil assembly to produce a gradient magnetic field affecting the main magnetic field along selected gradient axes;
• a radio frequency (RF) coil assembly;
• and
• an RF amplifier comprising:
• a first power amplifier for providing a first electric power;
• a second power amplifier for providing a second electric power;
• and
• a power combiner comprising:
• a first transmission line or lumped circuit element electrically connected to a first port which is configured to receive the first electric power;
• a second transmission line or lumped circuit element electrically connected between the first transmission line or lumped circuit element and a common port, wherein a first connection point is located between i) the first transmission line or lumped circuit element and ii) the second transmission line or lumped circuit element;
• a third transmission line or lumped circuit element electrically connected to a second port which is configured to receive the second electric power;
• a fourth transmission line or lumped circuit element electrically connected between the third transmission line or lumped circuit element and the common port, wherein a second connection point is located between i) the third transmission line or lumped circuit element and ii) the forth transmission line or lumped circuit element;
• and
• a balance capacitive element or balance inductive element including a first end and a second end, wherein the first end is electrically connected to the first connection point, and the second end is electrically connected to the second connection point,
• wherein (i) an odd-mode input impedance of the first port is zero and (ii) an odd-mode input impedance of the second port is zero, such that a voltage at the first port is equal to a voltage at the second port when a current flowing through the first port and a current flowing through the second port are unbalanced, and
• wherein the common port is configured to provide a combined electric power based on combining the first electric power and the second electric power, the combined electric power is configured to excite the RF coil assembly to transmit RF signals.

A power combiner, comprising:

• a first transmission line electrically connected to a first port;
• a second transmission line electrically connected between the first transmission line and a common port, wherein a first connection point is located between i) the first transmission line or lumped circuit element and ii) the second transmission line or lumped circuit element;
• a third transmission line electrically connected to a second port;
• a fourth transmission line electrically connected between a third transmission line and the common port, wherein a second connection point is located between i) the third transmission line or lumped circuit element and ii) the forth transmission line or lumped circuit element;
• and
• a balance capacitive element or balance inductive element including a first end and a second end, wherein the first end is electrically connected to the first connection point, and the second end is electrically connected to the second connection point,
• wherein (i) an odd-mode input impedance of the first port is zero and (ii) an odd-mode input impedance of the second port is zero, such that a voltage at the first port is equal to a voltage at the second port when a current flowing through the first port and a current flowing through the second port are unbalanced, and
• wherein a sum of an electrical length of the first transmission line and the second transmission line is equal to a half of a wavelength of signals transmitted along the first transmission line and the second transmission line, and a sum of an electrical length of the third transmission line and the fourth transmission line is equal to a half of a wavelength of signals transmitted along the third transmission line and the fourth transmission line.