JPS61274401A - Strip line type directional coupler - Google Patents

Abstract

PURPOSE:To make the titled directional coupler serve for a necessary measurement with a degree of coupling and a directivity of a high accuracy, extending over a wide frequency band, by varying almost linearly a mutual interval of two pieces of strip lines and the respective line widths, and making a ratio of the mutual interval and the line width roughly constant along the longitudinal direction of the strip line. CONSTITUTION:The titled directional coupler is constituted so that a conductor width of a strip line for forming a main line P and a coupling line S, and a mutual interval are varied linearly extending from d1 to d2, and from D1 to D2, respectively, and also a ratio of the mutual interval and the line width, D1/d1 or D2/d2 becomes the almost same prescribed value. Also, it is desirable to correct a variation of a characteristic impedance which is generated along the longitudinal direction of the line, by curving to some extent a tapered line conductor running along the longitudinal direction of the line. In this regard, an absolute value of the line length is set in advance so as to become equal substantially to 1/4 of a wavelength lambdagL of the lowest frequency in a use frequency range.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides two strip lines forming a main line and a coupled line arranged in parallel on a dielectric substrate having a ground conductor plate on the bottom surface, This is a strip line type directional coupler that separates traveling waves and reflected waves for use in voltage standing wave ratio measurements, etc., and is particularly designed to be commonly used over a wide frequency band. .

(Prior art) This type of IJ tube line type directional coupler can be applied to various frequencies over a wide frequency band, and has no effect on the traveling waves of the main line. It is required to be able to separate reflected waves into coupled lines with good coupling and directionality, and the conventional structure was as shown in FIG. 2.

That is, in the conventional configuration shown in the second figure, the strip lines of the main line P and the coupled line S are spaced apart and parallel to each other on the top surface of a dielectric substrate (not shown) on which a grounded conductor plate is attached to the bottom surface. and characteristic impedance 2 from the input power supply.
It is connected to the input terminal check □ of the main line P through the terminal resistor R1 of ゜, and the equipment under test Tt- is connected to the output terminal O□ of the main line P.
The load impedance 2 is grounded through a terminal resistor R3.

- 10,000, the coupling terminal 02 of the coupled line S parallel to the main line P is connected to a flow measuring device M for measuring the voltage amplitude of traveling waves or reflected waves, and the other ends I and I have a characteristic impedance of 2°. A terminating resistor R is connected.

Therefore, in the conventional configuration, the main line P and the coupled line S
The length is 14 wavelengths of the frequency used,
It is arranged on a dielectric substrate (not shown) having a high dielectric constant, is easy to manufacture, has high precision, and is inexpensive.
Furthermore, since it is extremely compact at high frequencies, it has been widely used in the past.

(Problem that XA Ming tries to solve) However, in the nine conventional strip line type directional couplers mentioned above, the line lengths of the main line P and the coupled line S are set to the wavelength of the operating frequency. , outside the immediate frequency range of the frequency used, the degree of coupling and the n1 degree of directionality decrease significantly. Therefore, for example, when using a directional coupler to measure the voltage standing wave ratio, etc. over a wide frequency range from the UHF band to the SHF band for various equipment related to satellite broadcasting, it is possible to perform the required measurements. In practical terms, there was an extremely serious problem in that a plurality of such directional couplers, each having the above-mentioned line lengths set individually for each frequency, had to be incorporated into the measuring device and used by switching.

The present invention solves the above-mentioned conventional problems and, for example,
When measuring voltage standing wave ratio, etc. over a wide frequency band ranging from the band to the SHF band, the strip line type directional coupling The purpose is to provide all the necessary resources.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides two strip lines, each forming a main line and a coupled line, on the top surface of a dielectric substrate provided with a bottom surface (a grounded conductor plate). In a strip line type directional coupler which is arranged parallel to each other, the length of the two strip lines is made to approximately correspond to the lowest frequency in the frequency range used, and
The mutual spacing between the two strip lines and the respective track widths are changed almost linearly, and the ratio of the mutual spacing and the track width is kept almost constant along the longitudinal direction of the IJ tube track. It is characterized by:

(Function) Therefore, according to the present invention, (i) the IJ tube line type directional coupler can be made to have a much wider band than the conventional one;

(Example) The present invention will be described in detail below with reference to the drawings.

First, an example of the configuration of a strip line type directional coupler according to the present invention is shown in FIG.

As is clear from comparing the configuration example shown in FIG. 1 with the conventional configuration shown in FIG. The mutual spacing and line width of the main line P and the coupled line S are changed in a tapered manner along the longitudinal direction of the line, and the ratio of the mutual spacing to the line width is set at any point f in the longitudinal direction of the line. 2, the values are multiplied by t so that they are approximately the same constant value. That is, the conductor width id of the main line P and the coupled line 5t-r, z strip line.
From □ to d3, and the mutual interval from D1 to d3,
The thickness t of the IJ tubular line conductor is changed substantially linearly to form a mutually coupled line S). Assume that t((D, d) is smaller by 1.

Also, in the longitudinal direction l of the line, the traveling direction i of the electrical signal is
In order to compensate for the line propagation loss that occurs, the tapered line conductor along the longitudinal direction of the line is slightly curved, thereby causing a change in characteristic impedance ΔωL along the longitudinal direction of the line. The absolute value of the line length is
As in the conventional configuration, the wavelength of the lowest frequency in the operating frequency range t is set to be substantially equal to 1/4 of 1gt. A state of constant coupling loss can be achieved over a wide frequency range of 1350 MH2. That is,
If the mutual spacing between the main line and the coupled line is constant, both the degree of coupling and directivity will be in the best condition when the line length is 1/ of the wavelength λ of the frequency used. Therefore, if the line length is the wavelength of the lowest frequency in the used frequency range f, then /
If 4# is set, the degree of coupling will decrease as the frequency increases. Such a decrease in the degree of coupling can be achieved by increasing the mutual spacing of the lines by increasing the frequency, that is, by increasing the wavelength λ.
This is appropriately compensated for by increasing the degree of bonding by bringing the materials closer together.

On the other hand, deterioration of directionality occurs as the mutual spacing of the lines approaches, and this deterioration of directionality is also caused by the present invention, as the ratio of the mutual spacing of the lines to the conductor width of the line increases along the longitudinal direction of the line. It is likewise suitably compensated for by varying the conductor width of the line along its length, so that it remains approximately the same constant value.

That is, the strip line type directional coupler of the present invention is constructed by skillfully utilizing the above-mentioned change in characteristics exhibited by the IJ tube line type directional coupler itself.

Next, FIG. 3 shows a schematic diagram of a measurement system for an intermediate frequency FM signal transmission system for satellite broadcasting, which is constructed and arranged using a strip line type directional coupler with one band widened as described above. In the measurement system with the illustrated configuration, a wide frequency range W ranging from 470 MHz to 1350 MHz, for example
In this study, characteristics such as the voltage standing wave ratio of each part of a transmission system that transmits intermediate frequency band signals for satellite broadcasting in the form of FM signals can be measured using a single strip line type directional coupling tF.
The measuring system can be easily and easily carried out using a t-tem, and such a measuring system can be constructed at a much lower cost than in the past.

That is, in the illustrated configuration 8, a pair of coupled lines S□, S2 having opposite directions to the main line P of the directional coupler C of the present invention are commonly coupled, and the switch SW
, t-switching so that the traveling wave Pf and the reflected wave pr can be selectively extracted from the output terminal (3) as the directional coupler output. In contrast, the strip line type directional coupler El having such a configuration has an oscillation output of 1.08 to 1.33 GHz from the SHF band oscillator (A) SH and 470 to 738.52 MHz from the UHF band oscillator (B) U) I. The oscillation output is switched by a switch SW, and the level is adjusted by a meter M such as an electric field strength meter, and then supplied via a broadband amplifier Afc. Note that each oscillator SH,
The DC voltage applied to the varactor of the oscillation tuning circuit in UH is finely adjusted by potentiometers L and B, respectively, and the channel is switched by switch SW in Ul (for F, the video signal is Terminal (1) uses test signal input such as modulation signal as modulation signal.
FM modulation money is added to the FM modulator F supplied from ○In addition, each device in this measurement system is stabilized by the DC voltage total stabilizing device E of the battery G and then supplied as a power supply voltage.

(Effects) As is clear from the above description, according to the present invention, the main line and the coupled line in a stripline type directional coupler that is arranged substantially parallel to the main line and has nine coupled lines. When the length is set to approximately 1/4 of the wavelength of the lowest frequency in the operating frequency range f 2, the mutual spacing of the lines and the line width are changed almost linearly along the longitudinal direction,
Moreover, by setting the ratio of the mutual spacing to the line width to be a constant value that is almost the same along the length of the line, a single line can be used over a wide frequency range from the UHF band to the SHF band, for example. IJ tube line type directional couplers are commonly used to provide high precision couplers and directivity, for example, for broadcasting waves in the 5I (F band) and U
A special effect can be obtained in that measurement of the voltage standing wave ratio, etc. of the transmission system with respect to the intermediate frequency signal using each channel of the HF band can be carried out easily and reliably.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of the tank bottom of an IJ tube line type directional coupler according to the present invention, Fig. 2 is a block diagram showing the configuration of a conventional strip line type directional coupler, and Fig. 3 1 is a block diagram showing an example of the configuration and arrangement of a satellite broadcast transmission system measuring device using an inventive directional coupler; FIG. P...Main line S, S□, S2...Coupled line M...Amplitude measuring device V...Input power supply T.
...Equipment under test SR...SHF band oscillator UH...UHF oscillator F...FM modulator A...Wideband amplifier C
...Directional coupler G...Battery E...Stabilizer Fig. 3

Claims (1)

[Claims] 1. A strip line type directional coupling in which two strip lines forming a main line and a coupling line are arranged substantially parallel to each other on the upper surface of a dielectric substrate having a ground conductor plate on the bottom surface. In the device, the lengths of the two strip lines are made to correspond approximately to the lowest frequency in the frequency range used, and the mutual spacing of the two strip lines and the respective line widths are changed almost linearly, and the mutual spacing is A strip line type directional coupler, characterized in that the ratio of the width of the strip line and the line width is substantially constant along the longitudinal direction of the strip line. 2. The strip line type directional coupler according to claim 1, wherein the length of the two strip line lines is approximately 1/4 of the wavelength at the lowest frequency. vessel.