JPH0151201B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is applicable to, for example, the 4GHz band and 6GHz band, or
A waveguide phase shifter that shares two frequency bands, the 20GHz band and the 30GHz band, and provides a specific phase difference between electromagnetic waves polarized in two mutually orthogonal directions propagating in the waveguide. It is.

Application examples of such a phase shifter include a circularly polarized wave generator (90° phase shifter) that converts linearly polarized waves to circularly polarized waves or circularly polarized waves to linearly polarized waves, or a polarization rotator (90° phase shifter). The 180° phase shifter is well known and is used in power supply circuits for communication antennas in the microwave or millimeter wave bands.

For this purpose, as a phase shifter having relatively flat frequency characteristics across two frequency bands,
A phase shifter having the structure shown in FIGS. 1a and 1b has conventionally been used.

In FIG. 1, 1 is a circular waveguide whose tube axis is Z, and 2 is a plurality of conductor rods, which are parallel to the tube axis Z and are opposite to each other in the circular waveguide 1.
A plurality of rod-shaped conductors are arranged in a line at specific intervals on the inner wall of a pipe. Note that the protrusion length of the two groups of conductor rods near both ends of the circular waveguide gradually decreases.

Here, the axis connecting two groups of opposing conductor rods is the X axis, the axis perpendicular to the axis X is the Y axis, and the axis X is 45
The electromagnetic wave incident at an angle of degree is E, and the electromagnetic wave E
, the _X component is _E It is determined that In addition, in c of the same figure, the upper and lower limit frequencies of the two frequency bands used are f _L1 , f _L2 , f _H1 , respectively.
Define f _H2 .

First, the effect of the conductor rod 2 on the electric field component _EX of the electromagnetic wave E shown in FIG. 1 will be explained. It is well known that the conductor rod 2 exhibits capacitive susceptance to the electric field component _EX . The magnitude of this susceptance can be adjusted by the insertion length l of the conductor rod 2, and the larger l is, the larger the capacitive susceptance is.
The frequency characteristic of this susceptance exhibits a larger capacitive susceptance as the frequency becomes higher, and the frequency characteristic becomes more remarkable as the insertion length l becomes larger.

Therefore, when a plurality of such conductor rods 2 are arranged in a line parallel to the tube axis _Z at a specific interval d, the phase of the electric field component E As the frequency becomes higher, the phase becomes more delayed compared to the current phase, and this situation is shown by curve 3 in FIG. 1c.

Next, the effect of the conductor rod 2 on the electric field component E _Y will be explained. It is well known that the conductor rod 2 exhibits inductive susceptance to the electric field component E. The magnitude of this susceptance can be adjusted by the diameter D of the conductor rod 2, and the conductor rod 2 with a larger diameter has a larger inductive susceptance, but the frequency characteristic of this susceptance is such that the lower the frequency, the larger the inductive susceptance. The larger the diameter D, the more remarkable the frequency characteristics.

Therefore, when a plurality of such conductor rods 2 are arranged in a line parallel to the tube axis _Z at a specific interval d, the phase of the electric field component E Compared to the phase at that time, the lower the frequency, the more the phase advances, as shown by curve 4 in FIG. 1c.

The relative phase φ in the Z-axis direction between the polarized waves generated between the electric field component E _X and _the electric field component E _Y is
It is determined by equation (1), where the respective propagation wavelengths for E _Y are λ _gX and λ _gY .

φ (degrees) = 360・L・(1/λ _gX −1/λ _gY ) ...(1) The relative phase between the polarized waves obtained by equation (1) is flat with little deviation from the required phase φ ₀ It is desirable to have a flat phase characteristic with little deviation over two frequency bands by the frequency characteristics of the capacitive susceptance and inductive susceptance of the conductor rod 2 mentioned above. is difficult. However, the deviation from the required phase φ ₀ can be made approximately equal across the two frequency bands.

Figures 2a and b show an example of the change in capacitive susceptance and inductive susceptance when the insertion length l of the conductor rod 2 is changed, and the relative position φ between polarized waves caused by this. . In Fig. 2, the large insertion length is denoted by l〓, and the small insertion length is denoted by l〓.
As can be seen from the figure, by changing the insertion length from l〓 to l〓, the magnitude of the relative phase φ between the polarized waves changes.
In addition, the frequency characteristics of the capacitive susceptance especially near the upper limit frequency f _H2 in the high frequency band change significantly, and a steep curve 5 is obtained. Therefore, the relative phase between polarizations φ also increases at frequencies near f _H2 ,
The curve 6 has a steep rise. On the other hand, Fig. 3 a, b
is an example of the change in capacitive susceptance and inductive susceptance when the diameter D of the conductor rod 2 is changed,
This shows the relative phase φ between the polarized waves caused by this. In Figure 3, the large diameter D〓,
The smaller diameter is taken as D〓. As can be seen from the figure, by changing the diameter D〓 to the diameter D〓, the inductive susceptance changes significantly near the lower limit frequency f _L1 of the low frequency band, and a steep curve 7 is obtained. Therefore, the relative phase φ between the polarized waves also becomes large at frequencies near f _L1 , resulting in a curve 8 with a steep rise.
In this way, by selecting the insertion length l and diameter D of the conductor rod 2 loaded into the circular waveguide 1, it is possible to
The deviation from the required phase φ ₀ can be made approximately equal over the frequency band. Furthermore, by selecting the total number of conductor bars 2 in consideration of the permissible deviation from the required phase φ ₀ , the frequency characteristics of the relative phase φ between the polarized waves can be finally determined by the curve 9 shown in FIG. It is possible to obtain flat frequency characteristics with relatively little deviation from φ ₀ in two frequency bands.

However, with the phase shifter having the conventional structure shown in FIGS. Although it is possible to obtain a further increase, the tube axis length L increases and the phase shifter becomes larger, which is not desirable. Therefore, a different structure has to be used, and although some of the structures are described in detail in patent publications (Patent Application Publication 1982-20825), the structure of the phase shifter is a circular waveguide. A plurality of wide waveguides are added to the tube wall forming an angle of 90 degrees with respect to the tube wall on which the conductor rods 2 are arranged on the outside of the tube 1, and the overall structure is large. Therefore, it is physically difficult to arrange a plurality of phase shifters in a certain limited place in order to configure a feeding circuit for a cluster feed such as a multi-beam antenna, and the overlap becomes heavy. As described above, the conventional phase shifter has the disadvantage that it is difficult to reduce the size and weight of the phase shifter.

The present invention improves the conventional phase shifter for the purpose of eliminating these drawbacks of the conventional phase shifter.
An object of the present invention is to provide a phase shifter with better frequency characteristics.

The drawings will be described in detail below.

FIGS. 5a and 5b show an embodiment of the present invention, and numerals 1 and 2 in the figures are the same as those in FIGS. 1a and 1b. 10 is a diameter D 2 different from the diameter D ₁ of the conductor rod ₂
It is a conductor rod. d ₁ is the arrangement interval of the conductor bars 2, and d ₂ is the arrangement interval of the conductor bars 10. That is, the phase shifter of the present invention includes a plurality of conductor rods 2 having a diameter D ₁ arranged at an interval d ₁ and a plurality of conductor rods 2 having a diameter D _{2 arranged at an interval d 2 .}
It has a structure including a plurality of conductor rods 10. Here, by choosing the relationships D ₁ > D ₂ and d ₁ > d ₂ , we attempted to improve the frequency characteristics of the relative phase between polarized waves and to make the tube axis length L ₂ shorter than the conventional one, thereby making it more compact. .

The sixth example shows how the above results can be obtained.
Figures a and b. Figures 6a and b show an example of changes in capacitive susceptance and inductive susceptance when the diameter and insertion length of the conductor rods are kept constant and the arrangement spacing d ₁ , d ₂ of the conductor rods is varied. It is a graph showing changes in relative phase φ between polarized waves caused by changes. In Figure 6, f _L1 , f _L2 , f _H1 ,
f _H2 is the same as in Figure 1c. d〓 and d〓 respectively indicate the arrangement interval of the conductor rods, and have a relationship of d〓>d〓. As can be seen from the figure, the capacitive susceptance decreases as the spacing between the conductor rods becomes smaller, and its frequency characteristics become more pronounced as the frequency increases, as shown by curve 11 in FIG. 6a. On the other hand, the inductive susceptance hardly changes even if the arrangement spacing of the conductor rods is changed, and becomes as shown by curve 12 in FIG. 6a. Therefore, the relative phase φ between the polarizations is reduced by the curve 1 in Figure 6b due to the decreasing effect of capacitive susceptance.
3 to curve 14. This means that the relative phase φ between polarized waves can be controlled only in the high frequency band, while leaving almost no change in the low frequency band.

The embodiment of the present invention shown in FIGS. 5a and 5b is constructed by paying attention to the effect of changing the diameter of the conductor rod shown in FIG. 3, in addition to the effects of the conductor rod described above. be. That is, (1) If the diameter D ₂ of the conductor rod is reduced without changing the insertion length of the conductor rod and the arrangement interval thereof, the frequency characteristics of the relative phase φ in the band from f _L1 to f _L2 will be reduced.

(2) If the arrangement interval d ₂ of the conductor rods is reduced without changing the diameter and insertion length of the conductor rods, the frequency characteristics of the relative phase φ will decrease in the band from f _H1 to f _H2 as shown in Figure 6. .

This will be explained in detail using FIG. 7. Figure 7 shows
This figure shows an actual measurement example of a circularly polarized wave generator (90° phase shifter) representing an embodiment of the present invention. In the figure, the vertical axis indicates the relative phase (degrees) between polarized waves, and the horizontal axis indicates frequency. f _L1 to f _L2 represent the 17.7GHz to 19.45GHz band (hereinafter referred to as the 20GHz band), and f _H1 to f _H2
Indicates the 27.5GHz to 29.25GHz band (hereinafter referred to as the 30GHz band). Curve 15 shows an actual measurement example of a conventional circularly polarized wave generator for both 20/30 GHz bands.
This is the characteristic of approximately 20 conductor rods of 0.08 wavelength arranged at intervals of approximately 0.25 wavelength. Further, curve 16 shows an actual measurement example of a circularly polarized wave generator according to the present invention, and its configuration is as follows:
Approximately 10 conductor rods with a diameter of approximately 0.06 wavelength are arranged at an interval of approximately 0.2 wavelength in the center of the circular waveguide, and 5 conductor rods are arranged at both ends.
Each conductor rod has a diameter of about 0.08 wavelength and is arranged at intervals of about 0.25 wavelength. First, by relatively changing the diameter of half of the conductor rods from 0.08 wavelength to 0.06 wavelength, 20G
In the Hz band, the frequency characteristics of the inductive susceptance decrease and the relative phase characteristics become flat. However, at the same time, in the 30 GHz band, the capacitive susceptance increases slightly, the phase deviates significantly from the required relative phase of 90°, and the frequency characteristics deteriorate, resulting in a curve 17 in FIG. Therefore,
The arrangement interval of the ten conductor rods having a diameter of 0.06 wavelength is changed from 0.25 wavelength to 0.2 wavelength. Then, due to the above-mentioned effect (2) of the conductor rod, the capacitive susceptance decreases in the 30 GHz band, and it works to further compensate for the deterioration in frequency characteristics caused by reducing the diameter of the conductor rod. , as a result, the seventh
A curve 16 in the figure is obtained. However, it must be noted here that the deterioration of the frequency characteristics caused by making the diameter of the conductor rod relatively small
In addition to selecting the arrangement spacing of the conductor rods, the number of conductor rods must be selected so as to work in the direction of more compensation. For example, if the number is small, the phase characteristics in the 20GHz band will not be improved much, while if the number is too large,
This means that it will not be possible to compensate for the phase characteristics in the 30 GHz band. Therefore, this is the main point of the present invention, and
This is a limitation due to the configuration and requires caution. In any case, by doing so, a better value of the phase characteristic can be obtained compared to the conventional characteristic (curve 15 in the figure). Physically, the overall length of the circularly polarized wave generator is
It can be approximately 84% longer than conventional ones.

The above description has been made assuming that a circular waveguide is used in both the embodiment and the actual measurement example. However, the shape of the waveguide is not limited to a circle. For example, an elliptical waveguide, an elliptical waveguide,
A rectangular waveguide may also be used. Further, the diameter of the conductor rods and the arrangement interval thereof are not limited to two types, and the same effect can be expected with three or more types. Furthermore, the above is not limited to two frequency bands, and similar effects can be expected in the case of a single wide frequency band or multiple frequency bands of three or more.

As described above, the plurality of conductor rods arranged in a row at specific intervals on the inner wall of the waveguide parallel to the tube axis and facing each other have different diameters, and the conductor rods have different diameters.
According to the phase shifter of the present invention, which uses conductor bars arranged at different intervals from the previous arrangement, the frequency characteristics of the relative phase between polarized waves can not only be made flat even when two frequency bands are shared, but also easily This has the great advantage of having a short overall length and miniaturization. Particularly, it is highly effective when used in a power supply circuit for a cluster feed such as a multi-beam antenna.

[Brief explanation of drawings]

FIG. 1 shows the structure and operating principle of a conventional dual-band phase shifter, in which a is a front view, b is a longitudinal sectional view, and c is a diagram showing the operating principle. Figure 2 shows the effect of the conductor rods constituting the phase shifter, where a shows the frequency characteristics of susceptance, and b
is a diagram showing relative phase. FIG. 3 shows the effect of the conductor rods related to the phase shifter, where a shows the frequency characteristics of susceptance, and b shows the relative phase. FIG. 4 is a diagram showing the phase characteristics of the phase shifter, and FIG. 5 is a diagram showing an embodiment of the present invention, in which a is a front view and b is a longitudinal sectional view. Figure 6 shows the effect of the conductor rod according to the present invention, where a shows the frequency characteristics of susceptance, and b
is a diagram showing phase characteristics. FIG. 7 is a diagram showing an actual measurement example of the present invention. In the figure, 1...Circular waveguide, 2...Conductor bar, 3,
4, 5, 6, 7, 8, 9... Characteristic curve, 10...
Conductor rods different from conductor rod 2, 11, 12, 13,
14, 15, 16, 17...Characteristic curve. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1. In a waveguide phase shifter that provides a specific phase difference between electromagnetic waves polarized in two mutually orthogonal directions within at least two used frequency bands, the waveguide phase shifter provides: A plurality of rod-shaped conductors are arranged on the inner wall of the waveguide in parallel to the tube axis direction of the waveguide, and the plurality of rod-shaped conductors have a first diameter. a first conductor group in which rod-shaped conductors having a second diameter are regularly arranged with a second interval; A frequency band common phase shifter characterized in that it is a combination. 2. The frequency band common phase shifter according to claim 1, wherein the second diameter and the second interval are smaller than the first diameter and the first interval, respectively.