JPS63115401A - Push-pull transformer - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a push-pull transformer according to claim 1.

In prior art television satellite receivers there is a need to convert a first intermediate frequency to a second intermediate frequency. In this case the first intermediate frequency is between 950 MHz and 1750 MHz.
The second intermediate frequency in the region is 483 MHz. A push-pull transformer is required to control the mixer diode with the oscillator signal used for wideband conversion. In this case the oscillator signal is tuned in the range 1460 MHz to 2230 MHz.

Effects of the Invention The advantage of the push-pull transformer described in the characteristic part of claim 1 is that there is no need to separately manufacture a module as a transformer, and the push-pull transformer as a whole can be a part of a television satellite receiver. The point is to do the following. In this way, the cost of a television satellite receiver can be significantly reduced by the invention.

The embodiment section describes advantageous embodiments of the push-pull transformer according to claim 1.

It is particularly advantageous to provide conductive connections between the strip lines that are connected in phase. In this way, it is possible to prevent the output from the in-phase output side from dropping rapidly with increasing frequency when the electrical length of the strip line is not much smaller than one wavelength of the oscillator. can.

Example theory Next, the present invention will be explained based on examples using figures.

Identical parts in each figure are designated by the same numbers.

The strip lines 1.2.3 are mounted in parallel on a printed circuit board (not shown).

It's short. The intermediate strip line 2 is connected to ground potential via the termination shown at the top in the figure, and the other end forms the input side 4 of the transformer. The upper end of the strip line 3 is also connected to ground potential. The other end forms the in-phase output side 5. (S) The IJ tube line 1 is connected so that the phase is opposite to that of the IJ tube line 2 and 3.) From the output side 5 of the IJ tube line 1, from the output side 6 A signal having a phase difference of 180° compared to the signal is extracted. Also, the strip line 2 connected so that the phases are the same
A conductive connection 7 is formed between and 3. In this way, it can be ensured that the amplitude characteristic at the output side 6 has a uniform course. If this conductive connection 7 is not made, a band-cancelling operation will occur near the upper end of the operating band, and this band-cancelling operation will cause the symmetry between the outputs 5 and 6 to be such that the maximum transmission frequency is smaller than the band-cancelling frequency. It becomes a serious hindrance. This will be explained in conjunction with FIGS. 2 and 6.

In one advantageous embodiment of the push-pull transformer according to the invention, the input side 4 is connected to the output side of a variable frequency oscillator 8 and the output sides 5, 6 are connected to mixer diodes 9, 10.

In FIG. 2, on a part of the printed circuit board 11, in addition to other circuits of the television satellite receiver, an IJ tube line 1.2.3 constituting the transformer of the present invention is shown. It is shown being worn. In the figure, printed circuit board 1
The strip line located on the back side of 1 is indicated by a dashed line. The conductor track 13 is connected to ground potential.

From the output terminals 5 and 6, frequency-dependent signals with a phase difference of 180° and the same amplitude are taken off.

Since the amplitude and phase change depending on the coupling length of the strip lines 2 and 1 or 2 and 3, it is necessary that the loops 1 and 3 have the same characteristics as possible. The distance to input loop 2 must be the same distance on average. 3
When a real line is provided in one plane (single-sided copper layer), the above requirements can be met if the line is formed in a straight line. Control of SMD double Schottky diodes is however not possible. This is because the distance between terminals 5 and 6 is too large.

The selected loop shape of the line allows the spacing between the connecting terminals 5 and 6 to be significantly reduced.

Since the output coupling lines 1 and 3 are located one above the other in two different planes, their lengths can be selected equally. One half of the input line 2 is applied to the top side of the printed circuit board and the other half to the back side, and a feedthrough connection is made at 12. Output coupling line (1 or 3)
therefore has a minimum spacing and a maximum spacing for the input coupling line 2. The average coupling spacing is however equal for both output lines. The net capacitive coupling between the loop ends 4 and 6 which are not connected to ground potential in the common mode part of the transformer is maximum. In this case, band cancellation for high frequencies occurs. This disturbance is reduced as follows.

a) Increase the bond spacing between points 4 and 6. The input coupling loop 2 has the largest coupling distance to the line 3 at the point 4 .

b) additionally conductively connecting lines 2 and 3; In this way the coupling is increased and the disturbances caused by the band cancellation characteristic are reduced.

Depending on the distance from ground potential of the conductive connection 7, the output sides 5 and 6
The intersection of the amplitude characteristic curves at and can be adjusted as shown in FIG.

In the particular use of push-pull mixers (balanced mixers), the frequency can therefore be adjusted in such a way that the mixer provides maximum isolation given a 180 DEG phase difference.

In the case of a push-pull transformer, the line length is set to 4, which is the maximum frequency of λ. In this way, the coupling coefficient is maximum. However, this length is chosen slightly smaller in a practical push-pull transformer, since otherwise band cancellation would cause disturbances in the case of common-mode operation.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit diagram of a push-pull transformer according to the present invention. FIG. 2 is a perspective view of a portion of a printed circuit having a push-pull transformer of the present invention. FIG. 6 is an amplitude-frequency diagram.

Claims (1)

[Claims] 1. In a push-pull transformer for high frequency signals, three substantially parallel strip lines (1, 2, 3) are provided on one insulating carrier (11). , 3) are connected to each other in phase and form one input side (4) and an in-phase output side (6), and the strip lines (1) connected in opposite phase form a push-pull output side (5). A push-pull transformer characterized by forming. 2. A push-pull transformer according to claim 1, wherein a conductive connection (7) is provided between the strip lines (2, 3) connected in phase. 3. The conductive connection (7) of the strip line (2, 3) is located closer to the ground terminal of the strip line (2, 3) than on the input side or the push-pull output side. Push-pull transformer described in scope 2. 4. The strip lines (1, 2, 3) are located in one plane and the strip line (2) forming the input side (4) is provided between other strip lines. The push-pull transformer according to any one of Items 1 to 4. 5. The strip lines (1, 3) forming the output side are provided in different sides of the printed circuit board (11) and a part of the strip line (2) forming the input side (4) is provided on one side. The push-pull transformer according to any one of claims 1 to 3, wherein the push-pull transformer is located inside the push-pull transformer and another part is located inside the other surface. 6. The strip line (2) forming the input side (4) is
Push-pull transformer according to claim 5, characterized in that in its end region connected to earth potential it passes through the plane in which the strip line (3) forming the in-phase output side (6) is provided. . 7. Claims 1 to 6 which can supply the signal of the variable frequency oscillator (8) to the input side (4) and connect mixer diodes (9, 10) to the output side (5, 6). The push-pull transformer according to any one of paragraphs.