CN109494967B

CN109494967B - Unbalanced-balanced converter and balanced-unbalanced converter

Info

Publication number: CN109494967B
Application number: CN201811516937.9A
Authority: CN
Inventors: 柳光福
Original assignee: AERODEV ELECTROMAGNETIC TECH Inc
Current assignee: AERODEV ELECTROMAGNETIC TECH Inc
Priority date: 2018-12-12
Filing date: 2018-12-12
Publication date: 2021-03-05
Anticipated expiration: 2038-12-12
Also published as: CN109494967A

Abstract

The invention provides an unbalance-balance converter, which comprises an unbalance-balance conversion coil, wherein the unbalance-balance conversion coil comprises a magnetic ring, and a coaxial cable is uniformly wound on the magnetic ring; the coaxial cable comprises an inner conductor and an outer conductor which are coaxially arranged, and an insulating filling layer is arranged between the inner conductor and the outer conductor; the unbalance-balance conversion coil is fixed in the center of the shielding box through a bracket; one end of the shielding box is provided with a first connector, and the other end of the shielding box is provided with a second connector and a third connector; the inner and outer conductors at one end of the coaxial cable are respectively welded to the inner and outer conductors of the first connector, and the inner and outer conductors at the other end of the coaxial cable are respectively welded to the inner conductors of the second and third connectors. The invention also provides a balun which is formed by exchanging the input end and the output end of the balun. The invention uses the coaxial cable product to manufacture the converter, can maintain the input and output impedance of the converter as the impedance of the coaxial cable, and is convenient to manufacture.

Description

Unbalanced-balanced converter and balanced-unbalanced converter

Technical Field

The invention relates to an unbalanced-balanced converter and a balanced-unbalanced converter for mutually converting a balanced signal and an unbalanced signal, belonging to the technical field of power electronics.

Background

The balun and the balun are passive devices that transform a balanced signal and an unbalanced signal to each other, and their electrical principles are shown in fig. 1. The conventional method of fabricating the balun transformer is: in a first step, two wires, such as wires 1-10 and wires 2-20 in FIG. 1, are twisted together; in a second step, the impedance of the 2-wire twisted port, i.e., the impedance between port 1 and port 2 (or between port 10 and port 20), is tested to a desired value, such as 50 ohms. The impedance of the expected value is closely related to the geometry of the 2-wire twist. And thirdly, winding a certain number of turns on the magnetic core or the magnetic ring according to the using frequency range and environment of the unbalanced-balanced converter to manufacture the unbalanced-balanced converter. The specific number of turns is determined by the lowest frequency at which the balun operates.

The challenge in actually manufacturing an unbalanced-balanced converter is: on the one hand, the impedance of the twisted pair is almost impossible to achieve exactly 50 ohms or 75 ohms. On the other hand, in the process of winding the unbalanced-balanced conversion coil on the magnetic core or the magnetic ring, the geometrical size of the twisted double wires is changed, so that the impedance between the twisted double wires is unstable, and the desired value is difficult to achieve.

Disclosure of Invention

The technical problem to be solved by the invention is how to keep the input and output impedance of the unbalanced-balanced converter constant all the time at a desired value.

In order to solve the above technical problem, an aspect of the present invention is to provide an unbalanced-balanced converter, including: the transformer comprises an unbalance-balance transformation coil, wherein the unbalance-balance transformation coil comprises a magnetic ring, and a coaxial cable is uniformly wound on the magnetic ring;

the coaxial cable comprises an inner conductor and an outer conductor, and an insulating filling layer is arranged between the inner conductor and the outer conductor;

the unbalance-balance conversion coil is fixed in the center of the shielding box through a bracket; one end of the shielding box is provided with a first connector which is used as an input end of the unbalanced-balanced converter; the other end of the shielding box is provided with a second connector and a third connector which are used as output ends of the unbalanced-balanced converter;

the inner conductor of one end of the coaxial cable of the unbalanced-balanced conversion coil is welded to the inner conductor of the first connector, and the outer conductor of the end of the coaxial cable is welded to the outer conductor of the first connector or the wall surface of the shielding box at one side close to the outer conductor of the first connector; this end is the unbalanced end of the balun;

an inner conductor of the other end of the coaxial cable of the unbalanced-balanced conversion coil is soldered to an inner conductor of the second connector, and an outer conductor of the end of the coaxial cable is soldered to an inner conductor of the third connector; this end is the balanced end of the balun.

Preferably, the impedance across the inner or outer conductor of the coaxial cable of the balun coil must satisfy: 2 pi L is more than 10 times of the impedance of the coaxial cable;

l is the inductance of the inner or outer conductor of the coaxial cable of the balun coil in H.

Preferably, the bracket is made of an insulating material.

Preferably, the magnetic ring is a magnetic ring made of a single material or a combined magnetic ring made of magnetic rings made of different materials.

Preferably, the outer conductor is externally provided with an insulating coating layer.

Preferably, the impedance of the first, second and third connectors is the same as the coaxial cable.

The present invention also provides a balun transformer characterized in that: the input end and the output end of the unbalanced-balanced converter are exchanged to form the balanced-unbalanced converter.

The device provided by the invention overcomes the defects of the prior art, and the unbalance-balance converter is manufactured by using a coaxial cable product, so that the input impedance and the output impedance of the unbalance-balance converter can be ensured to be kept unchanged all the time when the impedance of the coaxial cable is kept, and the unbalance-balance converter can be wound very conveniently. The input end and the output end of the unbalanced-balanced converter are exchanged to form the balanced-unbalanced converter.

Drawings

FIG. 1 is a schematic diagram of an unbalanced to balanced converter;

FIG. 2 is a schematic view of a coaxial cable configuration;

FIG. 3 is a schematic view of magnetic core lamination;

FIG. 4 is a schematic diagram of an unbalanced to balanced conversion coil;

fig. 5 is a schematic diagram of an unbalanced to balanced converter.

Detailed Description

The invention will be further illustrated with reference to the following specific examples.

This embodiment uses a coaxial cable product to manufacture the balun.

Referring to fig. 2, the coaxial cable 8 includes an inner conductor 15-15 'and an outer conductor 16-16' coaxially disposed, with an insulating filler layer 17-17 'between the inner conductor 15-15' and the outer conductor 16-16 ', and an insulating coating layer 19 outside the outer conductor 16-16'.

Winding the coil of the balun transformer with the coaxial cable 8 requires that the impedance of the inner conductor 15-15 'or the outer conductor 16-16' must be such that: 2 pi minimum operating frequency the inductance of the inner conductor 15-15 '(or the outer conductor 16-16'), the calculated impedance being greater than 10Multiple coaxial cable impedance. For example, let the lowest operating frequency be 10kHz, the impedance of the coaxial cable be 50 ohms, the inductance of the inner conductor 15-15' be L, and the unit H be 2 π 10⁴L > 10 x 50 ohms.

A plurality of amorphous magnetic rings with the outer diameter of 32mm, the inner diameter of 18mm and the height of 12mm and 7k ferrite magnetic rings with the outer diameter of 31mm, the inner diameter of 19mm and the height of 12mm are selected, and the inductance value of 1 turn with the frequency from 1kHz to 100kHz is measured by a digital bridge. 2 rings with higher inductance and close inductance are selected from the amorphous magnetic ring and the 7k ferrite magnetic ring respectively. Then, an amorphous magnetic ring 40 and a 7k ferrite magnetic ring 30 were concentrically pasted with 703 glue to obtain a combined magnetic ring 35 shown in fig. 3. The unbalanced-balanced transformer coil shown in fig. 4 was fabricated with 14 turns of 50 ohm coaxial cable 8, designated RG316, evenly distributed over the composite magnetic ring 35.

The inductance of the inner conductors 15-15 '(or the outer conductors 16-16') of the balun coils was measured and is shown in table one. When the frequency is 10kHz, the impedance of the inner conductor 15-15 '(or the outer conductor 16-16') is 2 × pi × 10000Hz × 15.7mH 985.96 ohm, which is 19.7 times of 50 ohm, and meets the impedance requirement when the low frequency is 10 kHz.

Table-inductance of the inner conductor 15-15

Frequency of

1kHz

10kHz

20kHz

40kHz

50kHz

100kHz

Inductance value

17.5mH

15.7mH

13.3mH

9.46mH

8.22mH

5.44mH

Referring to fig. 5, 1N-type female connector 34 is provided at one end of a steel shield case 28 having a length of 82mm, a width of 67mm and a height of 56mm, and 2N-type

female connectors

32 and 33 are provided at the other end of the steel shield case 28. In the steel shield case 28, a bracket made of an epoxy plate 23 is provided, and the unbalance-balance conversion coil is placed at the center of the steel shield case 28 by the bracket. The inner conductor 15 'of the coaxial cable at the end of the unbalanced-balanced conversion coil is welded to the inner conductor 64 of the N-type female connector 34, and the outer conductor 16' of the coaxial cable at the end of the unbalanced-balanced conversion coil is welded to the wall of the steel shield box of the outer conductor of the N-type female connector 34, close to the outer conductor of the N-type female connector 34. The inner conductor 15 of the coaxial cable at the other end of the unbalanced-balanced conversion coil is welded to the inner conductor of the N-type female connector 32, and the outer conductor 16 of the coaxial cable at the other end of the unbalanced-balanced conversion coil is welded to the inner conductor of the N-type female connector 33. And checking that the welding is correct, sealing the cover plate, and finishing the manufacture of the unbalanced-balanced converter. Wherein the end of the female N-type connector 34 is the unbalanced end of the balun and the ends of the female N-

type connectors

32 and 33 are the balanced ends of the balun.

In this embodiment, the unbalanced-balanced converter is manufactured by using a coaxial cable product, so that the input impedance and the output impedance of the unbalanced-balanced converter can be maintained at 50 ohms and can be kept unchanged all the time, and the unbalanced-balanced converter can be wound very conveniently.

The input and output ends of the balun are exchanged to form the balun. That is, the ends of the N-type

female connectors

32 and 33 are balanced terminals of the balun, and the end of the N-type female connector 34 is an unbalanced terminal of the balun, and the input and output impedances thereof are maintained at 50 ohms and are always kept constant.

While the invention has been described with respect to a preferred embodiment, it will be understood by those skilled in the art that the foregoing and other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention. Those skilled in the art can make various changes, modifications and equivalent arrangements, which are equivalent to the embodiments of the present invention, without departing from the spirit and scope of the present invention, and which may be made by utilizing the techniques disclosed above; meanwhile, any changes, modifications and variations of the above-described embodiments, which are equivalent to those of the technical spirit of the present invention, are within the scope of the technical solution of the present invention.

Claims

1. An unbalanced to balanced converter, characterized by: the device comprises an unbalance-balance transformation coil wound by a coaxial cable (8), wherein the unbalance-balance transformation coil comprises a magnetic ring, and the coaxial cable (8) is uniformly wound on the magnetic ring;

the coaxial cable (8) comprises an inner conductor (15-15 ') and an outer conductor (16-16 '), wherein an insulating filling layer (17-17 ') is arranged between the inner conductor (15-15 ') and the outer conductor (16-16 ');

the unbalance-balance conversion coil is fixed in the center of the shielding box (28) through a bracket; one end of the shield case (28) is provided with a first connector (34) as an unbalanced end of the unbalanced-balanced converter; the other end of the shielding box (28) is provided with a second connector (32) and a third connector (33) which are used as the balance end of the unbalanced-balanced converter;

the inner conductor of one end of the coaxial cable (8) of the unbalance-balance conversion coil is welded to the inner conductor (64) of the first connector (34), and the outer conductor of the end of the coaxial cable (8) is welded to the outer conductor of the first connector (34) or the wall surface of the shielding box (28) on one side close to the outer conductor of the first connector (34);

the inner conductor of the other end of the coaxial cable (8) of the unbalance-balance conversion coil is welded to the inner conductor of the second connector (32), and the outer conductor of the end of the coaxial cable (8) is welded to the inner conductor of the third connector (33);

the impedance across the inner conductor (15-15 ') or the outer conductor (16-16') of the coaxial cable (8) of the unbalanced-balanced transformer coil must be such that: 2 pi L is 10 times the impedance of the coaxial cable;

l is the inductance of the inner conductor (15-15 ') or the outer conductor (16-16') of the coaxial cable (8) of the unbalanced-balanced transformer coil, expressed in H.

2. A balun transformer as claimed in claim 1 wherein: the bracket is made of an insulating material.

3. A balun transformer as claimed in claim 1 wherein: the magnetic ring is a combined magnetic ring formed by magnetic rings made of a single material or magnetic rings made of different materials.

4. A balun transformer as claimed in claim 1 wherein: the outer conductor (16-16') is externally provided with an insulating coating (19).

5. A balun transformer as claimed in claim 1 wherein: the first connector (34), the second connector (32) and the third connector (33) all have the same impedance as the coaxial cable (8).

6. A balun transformer characterized by: the balun transformer of any one of claims 1 to 5 having the input and output thereof reversed.