JPS60214104A - Electromagnetic - Google Patents

Abstract

PURPOSE:To decrease number of layers in the progressing direction of a radio wave and also to apply an electromagnetic lens up to a high frequency region by forming the electromagnetic lens with a phase shifter using a liquid crystal. CONSTITUTION:The electromagnetic lens is formed by arranging required number of the phase shifters 11 in a face orthogonal to the radio wave progressing direction from an antenna horn 4. The phase shifter 11 is formed by arranging required number of phase shift elements 12 in the progressing direction of a radio wave 11. The phase shift element 12 consists of two sets of dielectric thin plates 13 opposed to each other and a cell made of one set of a conductor thin plate 14 in parallel with the progressing direction of the radio wave and packed with the liquid crystal 15. Then the phase shift element 12 is arranged corresponding to the bit number of a control signal in the progressing direction of the current. Thus, the number of layers in the progressing direction of the radio wave is decreased and since the liquid crystal is used, the lens is applied up to a high frequency region.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a radio wave lens that electronically controls the refraction direction of a beam using an external control signal.

[Prior art]

Figure 1 shows, for example, Microwave Journal.
This is a diagram showing a conventional radio wave lens that electronically controls the refraction direction of a beam, which was shown in February 1981 issue P, 45 to P, 53. A pin diode that exhibits equivalent short-circuit or open characteristics depending on the polarity of the applied bias voltage.

(3) is the metal grid (1) and the pin diode 12+
A dielectric plate for fixing in i-space, (41 is a horn antenna that irradiates radio waves to this radio wave lens, (51 is the above-mentioned wire mesh lattice (11, pin diode (21, dielectric plate (3)
), (6) and (7) are made by stacking multiple single-layer lens plates to direct the beam to the left and right sides, respectively.
A lens (8) that refracts the light up and down indicates the direction of the electric field of the radio wave.

Fig. 2 is a diagram showing the operating principle of the single-layer lens plate (51), Fig. 2 (a) is a configuration diagram, and Fig. 2 (bl) and (c) are pin diode +21 with forward and reverse directions, respectively. Equivalent diagram when bias voltage is applied, Figure 2 (
d) is a diagram showing the principle of beam refraction. still.

In the figure, (1) to 181 are the same as in FIG. 1, and (9) indicates the wave direction of the radio wave in the direction in which the radio wave travels (beam direction).

Now, in Fig. 2(a), the mounting interval of the pin diodes (2) is set to a dimension of 1/2 wavelength or less, and the metal grating Il
By setting the width of l and the interval tubes to predetermined dimensions, the metal grid (11 in Fig. 2(t)) I(C) is , act as conductive and capacitive circuit elements, respectively, and the transmitted phase amount of radio waves leads and lags respectively.

As shown in Fig. 2(a), for example, with one single layer lens plate (5), the upper half is forward biased (- in the figure) and the lower half is reverse biased (■ in the figure is a pin diode (21). By adding each, the phase of the upper half advances and the phase of the lower half lags, as mentioned above.

The wavefront (9) of the radio wave changes and is equivalently seen as shown by the broken line in the figure, and the traveling direction Qll of the radio wave is refracted downward.

However, as described above, the conventional radio wave lens shown in Fig. 1 combines a pin diode and a metal grating, and changes the amount of transmission phase by switching the bias voltage in the forward/reverse direction to refract the beam. When this -wave lens is combined with a fixed beam antenna to configure an electronic scanning antenna, if the transmission phase amount is changed every Δφ radian, the layer of the single-layer lens plate in the direction of propagation of the wave is 1%. The number N is expressed by the following equation assuming that the beam is scanned vertically and horizontally.

2π N=2(--s) ...111 Δφ For example, if Δφ is π/8 radian used in a normal electronic scanning antenna, the number of layers N is 30, and the number of layers per layer is 2/2. Since pin diodes must be used at intervals of one wavelength or less, the number of pin diodes required is enormous, resulting in drawbacks such as high cost and difficult assembly.

Furthermore, as the frequency increases, such as in the millimeter wave band and submillimeter wave band, the influence of the pin diode's junction capacitance increases, and even when reverse bias is applied, it does not become a perfect order of magnitude. Therefore, when switching between forward and reverse bias, The disadvantage is that the change in the amount of transmitted phase becomes small, making it difficult to refract the beam.

[Summary of the invention]

This invention was made with the purpose of improving such drawbacks, and it is possible to change the amount of transmission phase corresponding to the number of bits in order to reduce the number of layers in the direction of propagation of the IL wave, and to This project proposes a radio wave lens that can be used up to high frequency ranges.

[Embodiments of the invention]

FIG. 3 is a diagram showing an embodiment of the present invention.

In the figure, 141. tel is the same as in FIG. 1, and αυ is the phase shifter constituting the radio lens according to the present invention.

FIG. 4 is a partially missing diagram showing an example of the configuration of the phase shifter,
In this case, a 4-bit phase shifter is used as an example. In the figure, Q21 is a phase shift element corresponding to each pit constituting the phase shifter; +13. +141. (Is
constitutes each phase shift element t-. Two sets of thin dielectric plates facing each other, a set of thin conductive plates facing each other and parallel to the direction of propagation of radio waves, and a liquid crystal filled in a cell made up of the thin plates, each of which has a bias voltage applied to it. Connecting wire for? show.

In the phase shift element α3 configured as described above.

The amount of phase shift of radio waves is mainly determined by the permittivity of the liquid crystal in the direction of the electric field9. Letting this be ε2, the phase shift amount Φ of the radio wave can be approximated by the following equation.

Φ=-L! a (W-t) (radian) ...(
2) λ ρ where d: Thickness of the liquid crystal layer of one phase shift element with respect to the direction of radio wave propagation λ: Wave wavelength Figure 5 is a cross-sectional view of an example showing the relationship between applied voltage and liquid crystal molecular orientation. , (a) is when no voltage is applied, (b
) indicates the case where voltage is applied.

In the figure, +81 and (L35-fl+9) are the same as in FIG.

αη is a liquid crystal molecule whose long direction indicates the direction of molecular orientation.

(ill and al respectively indicate a power supply and a switch for applying a bias voltage. If no voltage is applied as shown in Fig. 5(a), the molecules are orientated so that they are perpendicular to the direction of the radio wave. Implement this in advance.

As shown in FIG. 5(b), when a voltage is applied, the molecules are oriented in the direction of the electric field of the radio wave.

FIG. 6 is a diagram illustrating an example of the frequency characteristics of the dielectric constant of a liquid crystal, comparing the molecular orientation direction and the direction orthogonal to the orientation direction. In the figure, the horizontal axis is the frequency (Hz) and the vertical axis is the dielectric constant, the solid line is the dielectric constant in the orientation direction of the molecules, and the broken line is the total dielectric constant in the direction perpendicular to the orientation direction.

As mentioned above, liquid crystals can change the alignment direction of two molecules by applying an external voltage, and since the dielectric constant in the alignment direction and the direction orthogonal to it differs at most frequencies, this property of liquid crystals can be changed. By changing the applied voltage to 0N10FF, the permittivity ερ of the liquid crystal in the direction of the electric field of the radio wave can be changed, and as shown in equation (2), the amount of phase shift of the radio wave changes in response to the change in ερ. change.

Now, if the relative permittivity of the liquid crystal in the alignment direction is εd, and the relative permittivity in the direction perpendicular to the alignment is εC, then the change in phase shift ΔΦ caused by turning the voltage to the liquid crystal from OFF to ON is approximated by the following equation. .

ΔΦ=d(F;5-)<radian)...(3)th (
3) From the relationship in the equation, the absolute value of ΔΦ is π.

π/2. π/4. Choose a thickness d that is π/8 radians.

A 4-bit phase shifter can be formed by setting this to the thickness of the liquid crystal in the direction of propagation of the radio wave of each bit's phase shift element.

FIG. 1 is a diagram showing the principle of refraction of radio waves by the radio wave lens according to the present invention. In the figure (8+ -Ql is in Figure 2,
aυ are the same as in Figure 3 (12A).

(12B), (12C), (12D) are π and π, respectively
/2. π/4°π/8 radian phase shift element is shown. Here, it is assumed that the phase shift elements shaded with diagonal lines are biased so that the phase is delayed. Now there are four phase shifters a
Since υ retards the phase shift of the transmitted wave by π/8 radians from top to bottom, the wave front of the wave equally parsimoniously becomes like a broken line, and the direction of propagation of the radio wave is refracted downward.

The above explanation was for the case of 4 bits.

This radio wave lens is not limited by the number of bits due to its configuration, and can arrange as many phase shift elements as necessary in the direction of wave propagation.

〔Effect of the invention〕

As explained above, compared to conventional electronically controlled radio wave lenses, this invention can significantly reduce the number of layers (number of elements) in the direction of propagation of radio waves for the same minimum phase shift, resulting in lower costs. In addition, when used at high frequencies such as millimeter wave and submillimeter wave bands, the use of liquid crystals eliminates the need for pin diodes, which was a problem with conventional radio lenses. See the effects that can solve the problem.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a conventional radio wave lens, Fig. 2 is a diagram showing the operating principle of a single-layer lens plate, Fig. 3 is a diagram showing an embodiment of the present invention, and Fig. 4 is a diagram showing the configuration of a phase shifter. Some missing figures showing examples,
FIG. 5 is a cross-sectional view of an example showing the relationship between applied voltage and molecular orientation of liquid crystal, FIG. 6 is a diagram showing frequency characteristics of relative dielectric constant of liquid crystal, and FIG. 7 is refraction of radio waves of the radio wave lens according to the present invention. FIG. In the figure, αυ is a metal grid, (2; is a pin diode, (3) is a dielectric plate, (41 is a horn antenna, (5) is a single layer lens plate, +61. +71 is a lens, +81
is the direction of the electric field of the radio wave, -(9) is the wavefront of the radio wave, is the traveling direction of the radio wave, Qυ is the phase shifter, α3 is the phase shift element, Ql is the dielectric thin plate, α is the conductive thin plate, a! 9 is a liquid crystal, the wire is a connection line, Q7) is a liquid crystal molecule, o8 is a power supply, and α9 is a switch. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa 1B Figure 3 Figure 2 (cl) Figure 4 Figure 5 (a) 6 6 (b) 6

Claims (1)

[Claims] In a radio wave lens that electronically controls the direction of refraction of a beam by a signal such as an external voltage, there are two lenses facing each other.
A cubic or rectangular parallelepiped cell consisting of a set of dielectric thin plates and a set of conductor thin plates parallel to and opposite to the direction of propagation of radio waves; Change the orientation direction of the 0 molecule. A phase shift element consisting of a liquid crystal that handles the dielectric anisotropy that changes accordingly is divided into predetermined lengths corresponding to the number of bits of the control signal, and arranged in the direction of propagation of the % wave for the number of bits. A radio wave lens characterized in that a required number of phase shifters are arranged in a plane perpendicular to the direction of propagation of radio waves in order to refract the beam.