JPS6016088Y2 - Balanced unbalanced converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a balanced/unbalanced converter used in a VHF and UHF band power amplification device.

In general, push-pull connections of transistors have been commonly used in high-power amplifier devices in the VHF and UHF bands in order to increase the output of the device and improve linearity.

FIG. 1 shows a circuit example of a push-pull connection power amplifier.

In the figure, a high frequency signal applied between input terminals 1 and 1' is divided into two parts with a phase difference of 180 degrees by an input side balanced/unbalanced conversion transformer 3, and an impedance matching capacitor is used. , 8.11 and transmission lines 13.14 to the bases of the amplification transistors 5 and 6 with a phase difference of 180 degrees.

The signals amplified by the transistors 5 and 6 are applied from each collector to the output side balanced/unbalanced conversion transformer 4 via impedance matching transmission lines 15, 16 and capacitors 12, 9, 10, and are combined by 180 degrees. , taken out between output terminals 2 and 2'.

Note that bias circuits for the bases and collectors of the transistors 5 and 6 are omitted in FIG.

In such a push-pull type power amplifier, the balanced/unbalanced conversion transformers 3 and 4 are constructed by spirally winding a semi-flexible coaxial cable as shown in FIG.

In the figure, 90 is a coaxial cable constituting a balanced/unbalanced conversion transformer, 91 is an unbalanced terminal, and 92 and 93 are balanced terminals.

FIG. 3 shows the actual structure of the push-pull type power amplifier shown in FIG. 1 using the above-mentioned balanced/unbalanced conversion transformer, and FIG. 4 is a side view of the same.

In addition, in Fig. 3, as in the case of Fig. 1, the base,
The collector bias circuit is omitted.

In FIG. 3, numeral 37 is a printed circuit board having conductors on both sides, and the shaded portions indicate the conductors.

The input signal applied between the input terminal 21 and the ground terminal 21' is divided into 18 jets by a balanced unbalanced conversion transformer 23 constituted by a coaxial cable as shown in FIG.
Capacitors 27 and 28 for impedance matching, respectively
．． 31 from the transmission line 33.34 to the transistor 25.26.

The signal amplified by the transistors 25 and 26 is transferred to the transmission line 3.
5.36 to capacitor 3 for output impedance matching
2, 29, and 30, the output terminal 22 is combined by 180 degrees by the balanced/unbalanced conversion transformer 24 shown in FIG.
and the ground terminal 22'.

In a power amplifier having such a configuration, one end of the outer conductor of the input side and output side balanced/unbalanced conversion transformers 23 and 24 constitutes a balanced terminal and cannot be grounded.
It is easy to induce or be induced into other circuits, and due to its structure, it is three-dimensional as shown in Figure 4, so it is easy to cause mutual induction between the input side and the output side, so it is not a normal power amplifier. There were drawbacks that hindered the operation of

In addition, since the outer conductor of semi-flexible coaxial cables is a copper pipe, it is hard and takes a lot of time to form, is difficult to connect and fix on the printed circuit board mentioned in 37 above, and is also susceptible to temperature changes. Expansion and contraction add strain to the joint between the terminal and the printed circuit board, which has the disadvantage of causing accidents such as soldering coming off when used for long periods of time.

The present invention eliminates the above-mentioned drawbacks, and aims to provide a balanced-unbalanced converter that is less likely to cause inductive effects and that is easy to assemble and wire.

An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 5 and 6, 80 is a dielectric plate, and 85 and 86 are first and second strip lines made of copper foil or the like.

As shown in the figure, the first and second strip lines 85 and 86 are wired on the front and back surfaces of the dielectric plate 80, and are bent so that the wire length is set to 1/4 of the transmission signal wavelength λ.

Further, these strip lines 85 and 86 have the same line width 1 over their entire length, and face each other with a dielectric plate 80 interposed therebetween as shown in FIG. 6, so that a predetermined impedance is formed between both lines.

Both lines 85 and 86 are coupled by this impedance, and the impedance value is determined by the line width l and the dielectric plate 80.
Set by the material and thickness of the

Note that this impedance is 85.86
They may also be formed by shifting them from each other so that some of them face each other.

Also, terminals 81, 82.81' of strip lines 85.86 formed on the side edges of the dielectric plate 80.

82' are formed so as to be shifted from each other in order to easily connect with other circuits.

These terminals 81, 82, 81', 82' are formed so that the line lengths are equal to each other.

That is, the terminal 81 and the terminal 8
2', terminal 81' and terminal 82 correspond to each other.

Note that the strip lines 85 and 86 are formed by ordinary printed wiring.

In FIG. 5, terminal 81' is grounded, and terminals 81 and 81'
When a high frequency signal is applied between terminal 82 and ground, terminal 82
A distribution signal having a phase difference of 180 degrees is derived between '' and ground, and the same effect as that of the balanced/unbalanced conversion transformer shown in FIG. 2 can be obtained.

Such a balanced/unbalanced converter is connected to the power amplifier shown in FIG. 1 as shown in FIG. 7.

In FIG. 7, 53 and 54 are the balanced unbalanced converters, and the terminal 81' of the input side balanced unbalanced converter 53 and the terminal 82' of the output side balanced unbalanced converter 54 are conductors connected to the ground plane of the amplifier board 67. 72 and 73, respectively.

In the figure, the input terminal 8 of the input side balanced unbalanced converter 53
The high frequency signal applied between
．． 82', and are introduced into input matching capacitors 57 and 58 through connecting conductors 74 and 75, respectively, and are connected to amplifying transistors 55 and 56 via impedance matching capacitor 51 and transmission lines 63 and 64, respectively.
added to the base of.

The signal amplified by the transistor 55.56 is sent from the collector to the connection conductor 76.77 via the transmission line 65.66 for impedance matching and the capacitors 52, 59.60.
terminals 81.81 of the output side balanced-unbalanced converter 54 via
' respectively, and are combined by 180 degrees to terminal 82.
82'.

According to the above configuration, since both the input side balanced unbalanced converter 53 and the output side balanced unbalanced converter 54 are configured in a planar manner, mutual induction can be extremely reduced and ideal amplification operation can be performed. can be set.

In addition, since the above-mentioned balanced-unbalanced converter can be constructed from a printed circuit board, there is no need for the conventional processing and shaping of coaxial cables, and the labor for assembly and wiring can be saved, which is particularly effective in mass production. No distortion is applied to the connection point with the amplifier board, improving reliability.

Furthermore, since the cross-sectional areas of the strip lines can be made completely equal, the balance between the balanced terminals can be improved compared to when conventional coaxial cables are used.

Although the line length is set to λ/4 in FIG. 5, the line length and the impedance between the lines may be selected to arbitrary values depending on the impedance connected to each terminal.

Further, the bending of the line is not limited to that shown in the drawings, and the line may be bent in any shape on the substrate.

As described above, according to the present invention, it is possible to obtain a balanced unbalanced index converter with good characteristics by forming it planar and eliminating the induction effect.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a push-pull amplifier using a balanced/unbalanced converter, Figure 2 is a perspective view of a conventional balanced/unbalanced conversion transformer, and Figure 3 is the conversion transformer shown in Figure 2 as shown in Figure 1. Figure 4 is a side view of Figure 3, and Figure 5 is a front view of the circuit implemented in the circuit.
The figure is a perspective view showing one embodiment of the balanced unbalanced converter according to the present invention, FIG. 6 is a sectional view taken along line A-A in FIG. 5, and FIG. FIG. 1 is a front view of the device mounted on the circuit shown in FIG. 1, and FIG. 8 is a side view of FIG. 7. 80... Dielectric plate, 85.86... First and second strip lines, 53.54...
Balanced unbalanced converter.

Claims (1)

[Scope of utility model registration request] A dielectric plate, and first and second strip lines that are shaped to face each other on both sides of the dielectric plate and are wired to have equal line lengths with terminal portions arranged at side edges of the dielectric being shifted from each other. Balanced unbalanced converter with.