Marchand balun circuit

1. Technical Field

The present disclosure relates to baluns, particularly, to a Marchand balun circuit.

2. Description of Related Art

As is known, Marchand balun is one of the most popular forms of microwave balun used to convert unbalanced signals to balanced signals. As shown in FIG. 2 , a conventional Marchand balun 10 includes four coupled lines 101 which form six terminals. The six terminals respectively are two grounded terminals, one terminal which is hung up, one unbalanced terminal NP, and two balanced terminals BP. The unbalanced terminal NP is used to connect to an unbalanced device, such as a coaxial cable. The two balanced terminals BP are used to connect to balanced device, such as a dipole antenna. The Marchand balun receives unbalanced signals from the unbalanced device via the unbalanced terminal NP, and converts the unbalanced signals to balanced signals, and then outputs the balanced signals, to the balanced device via the two balanced terminals BP.

However, the conventional Marchand balun does not include matching circuit, and is difficult to control the frequency response and the bandwidth of the balanced signals that are output.

Therefore, it is desirable to provide a Marchand balun circuit to overcome the described limitations.

Many aspects of the present disclosure are better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a schematic diagram of a Marchand balun circuit, in accordance with an exemplary embodiment.

FIG. 2 is a schematic diagram of a conventional Marchand balun.

Embodiments of the present disclosure will now be described in detail, with reference to the accompanying drawings.

Referring to FIG. 1 , a Marchand balun circuit 1 includes a Marchand balun 10 and a matching circuit 20 . The Marchand balun 10 includes two grounded terminals (not labeled), a terminal (not labeled) which is hung up, an unbalanced terminal NP, and two balanced terminals BP. The matching circuit 20 includes an unbalanced matching circuit 201 and a balanced matching circuit 202 . The unbalanced matching circuit 201 is connected to the unbalanced terminal NP and is used to match the unbalanced terminal NP. The balanced matching circuit 202 is connected to the balanced terminal BP, and is used to match the balanced terminal BP.

In detail, as shown in FIG. 1 , the unbalanced matching circuit 201 includes a first resistor R 1 , a first impedance Rs 1 , and a second impedance Rs 2 . The first impedance Rs 1 and the second impedance Rs 2 are connected between the unbalanced terminal NP and ground in series. The first resistor R 1 is connected between the ground and a connection node N 1 of the first impedance Rs 1 and the second impedance Rs 2 .

The balanced matching circuit 202 includes a second resistor R 2 , a third resistor R 3 , a third impedance Rs 3 , a fourth impedance Rs 4 , a fifth impedance Rs 5 , and a sixth impedance Rs 6 . The third impedance Rs 3 and the fourth impedance Rs 4 are connected between one balanced terminal BP and the ground in series. The fifth impedance Rs 5 and the sixth impedance Rs 6 are connected between the other balanced terminal BP and the ground in series. The second resistor R 2 is connected between the ground and a connection node N 2 of the third impedance Rs 3 and the fourth impedance Rs 4 . The third resistor R 3 is connected between the ground and a connection node N 3 of the fifth impedance Rs 5 and the sixth impedance Rs 6 .

The connection node N 1 is used to connect to an unbalanced device, such as a coaxial cable, a probe, and etc, and the Marchand balun 10 receives unbalanced signals from the unbalanced device via the unbalanced terminal NP and the connection node N 1 . The connection nodes N 2 , N 3 are used to connect to a balanced device, such as a dipole antenna, and etc, then the Marchand balun 10 converts the unbalanced signals to balanced signals and outputs the balanced signals to the balanced device via the two balanced terminals BP and the connection nodes N 2 , N 3 .

In the embodiment, the impedance value of the impedances and the resistance value of the resistors of the unbalanced matching circuit 201 are determined by parameters of the unbalanced device connected to the unbalanced matching circuit 201 , such as the diameter of the coaxial cable, or the resistance value of the probe. The impedance value of the impedances and the resistance value of the resistors of the balanced matching circuit 202 are determined by the parameters of the balanced device, such as the length of the dipole antenna.

Therefore, in the present disclosure, the Marchand balun circuit 1 can better control the frequency response and bandwidth of the balanced signals that it converts.

It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being exemplary embodiments of the present disclosure.