JPS60214105A - Phase shifter - Google Patents

Abstract

PURPOSE:To obtain a phase shifter using a liquid crystal used up to a high frequency region by utilizing the dielectric anisotropy of the liquid crystal so as to change the amount of phase shift of a radio wave passing through the liquid crystal. CONSTITUTION:A cell is formed with two sets of dielectric thin plates 7 opposed to each other and one set of a conductor thin plate 8 opposed to each other and in parallel with the progressing direction 5 of the radio wave. The liquid crystal 9 is filled in the cell. The direction of orientation of molecules is changed by impressing a voltage to the liquid crystal 9 from a power supply section 4 via the conductor thin film 8. Further, the dielectric constant of the liquid crystal in the direction of electric field of the radio wave is changed by turning on/off the impressed voltage. Since the amount of phase shift of the radio wave is changed corresponding to the change in the dielectric constant, the cell is used as the phase shifter. The phase shifter using the liquid crystal applied up to a high frequency region is obtained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a phase shifter used in, for example, a radio wave lens that electronically scans a beam.

[Prior art]

Figure 1 shows, for example, Microwave Journal.
This is a diagram showing a phase shifter used in a conventional radio wave lens that electronically scans a beam shown in February 1981 issue, P, 45 to P, 53. In Figure 1, 111 is a metal grid;
(2) is a pin diode that exhibits equivalent short-circuit or open characteristics depending on the polarity of the applied bias voltage, and (3) is a pin diode (
2) is a dielectric plate that fixes the device in space, and (4) is a power supply unit that supplies a bias voltage to the pin diode (2).

(5) is an arrow indicating the traveling direction of the radio wave, and (6) is an arrow indicating the electric field direction (polarized wave) of the radio wave.

Figure 2 is a diagram showing the operating principle of a conventional phase shifter.
Figure (=) is a configuration diagram, and Figures 2 (b) and 2 (C) are equivalent diagrams when a forward or reverse bias voltage is applied to the pin diode (2), respectively. still.

The symbols in the figure are the same as in FIG. 1. Now, in Fig. 2(a), by setting the installation interval of the thorn diodes (2) to a dimension of 1/2 wavelength or less, and by setting the width and interval of the metal grating 110 to predetermined dimensions, Fig. 2(a) is obtained. b)
, The metal grid (1) in (C) acts as an inductive and capacitive circuit element for radio waves with an electric field direction parallel to the metal grid fi+ passing through it, and the transmission phase amount of the radio waves advances. , resulting in a delay.Therefore, it functions as a phase shifter.

However, as mentioned above, since the bin diode is used, 1. When the frequency of radio waves becomes high, such as in the mi'lJ wave or submillimeter wave band, 1. The effect of the junction capacitance of the bin diode (2) becomes large, and it does not become completely open even when reverse bias is applied. Therefore, the change in the amount of transmission phase when switching forward/reverse bias becomes small, making it difficult to use as a phase shifter. There was significant deterioration in characteristics.

Similarly, as the frequency of radio waves increases, the metal grid tl+
There are drawbacks in that manufacturing problems arise, such as strict dimensional accuracy such as one width interval, and difficulty in mounting the bin diode (2).

[Summary of the invention]

The present invention was made with the aim of improving such drawbacks, and proposes a phase shifter using liquid crystal that can be used up to a high frequency range.

[Embodiments of the invention]

FIG. 3 is a partially cutaway diagram showing an embodiment of the present invention.
In the figure, (4) to (6) are the same as the conventional device shown in FIG. 1, and (7) is two sets of 6-electric thin plates facing each other;
(8) is a pair of conductive thin plates parallel to and facing the direction of propagation of radio waves, and (9) is a liquid crystal filled in a cell composed of (7) and (8).

In the phase shifter configured as above, the amount of phase shift of the radio wave is mainly determined by the dielectric constant of the liquid crystal in the direction of the electric field, and if this is now ε, the amount of phase shift of the radio wave Φ can be approximated by the following equation. .

Here, d: thickness of the liquid crystal layer in the direction of propagation of the radio wave λ: wavelength of the radio wave Figure 4 is a cross-sectional view of an example showing the relationship between the applied voltage and the molecular orientation of the liquid crystal, and (a) If not, (b
) indicates the case where voltage is applied.

In the figure, (4) and (6) to (9) are the same as in Figure 3, +fl is a liquid crystal molecule whose long direction indicates the direction of molecular orientation, Uυ, and Q2 are in the power supply section (4). Includes power supply and switch respectively. Now Figure 4 (a
), when no voltage is applied, the molecules are orientated in advance so that they are perpendicular to the electric field of the radio wave. As shown in FIG. 4(b), when a voltage is applied, the molecules are oriented in the direction of the electric field of the radio wave.

Figure 5 shows the frequency characteristics of the dielectric constant of liquid crystal in the molecular orientation direction.
FIG. 3 is a diagram showing a comparison between the orientation direction and a direction perpendicular to the orientation direction.

In the figure, the horizontal axis is frequency (H2).

The vertical axis is the relative permittivity, the magnetic flux is the relative permittivity in the orientation direction of the molecules, and the broken line is the relative permittivity in the direction perpendicular to the orientation direction.

As mentioned above, the orientation direction of one molecule of liquid crystal can be changed by applying an external voltage, and the dielectric constant in the orientation direction and the direction orthogonal to it differs at most frequencies, so PX crystal By turning the applied voltage ON/OFF using this characteristic of , it is possible to change the permittivity ε of the liquid crystal in the direction of the electric field of the radio wave, and as shown in equation (1), the radio wave changes in response to the change in ε. Since the amount of phase shift changes, it can be used as a phase shifter.

〔Effect of the invention〕

As explained above, this invention is a phase shifter that changes the amount of phase shift according to the bias voltage applied to the liquid crystal.

Since it can be used up to a high frequency range and there are no particular constraints on 1-dimensional accuracy, it has the effect of solving manufacturing problems when used in a high frequency range.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 11 is a diagram showing a conventional phase shifter, Fig. 2 is a diagram showing the operating principle of the conventional phase shifter, and Fig. 3 is a diagram showing an embodiment of the present invention. The cutaway diagram, M4 diagram, is a cross-sectional view of an example showing the relationship between applied voltage and molecular orientation of liquid crystal. FIG. 5 is a diagram showing the frequency characteristics of the dielectric constant of liquid crystal. In the figure, 11 is a metal grid, and (2) is a bin diode. (3) is a dielectric plate, (4) is a power supply section, and (5) is a direction in which radio waves travel. (6) is the electric field direction of the radio wave, (7) is the dielectric thin plate, (8)
is a thin conductor plate, (9) is a liquid crystal, α1 is a molecule of liquid crystal, flυ
is the power supply, and α is the switch. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa Figure 2 (/2) (b)' CC) Figure 3] Figure 4 (0) IJ4rIIJ (b)

Claims (1)

[Claims] A cubic or rectangular parallelepiped cell consisting of two sets of thin dielectric plates facing each other and a set of thin conductive plates facing and parallel to the direction of propagation of radio waves; It is composed of a liquid crystal that changes the alignment direction of one molecule by applying voltage, and has dielectric anisotropy that changes accordingly, and a power supply unit that supplies and controls the voltage applied to the liquid crystal. A phase shifter characterized in that the amount of phase shift of radio waves when transmitted through the liquid crystal is changed by utilizing the dielectric anisotropy of the liquid crystal that changes accordingly.