RU2620893C1 - Device for reception of orthogonal linearly polarized waves - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device contains two low-noise amplifiers, a bridge device, as well as coaxially located and interconnected a segment of a circular waveguide and a coupler of orthogonal linearly polarized waves, made on a circular waveguide and equipped with a short-circuit. In this case, a phase-shifting inhomogeneity located at the end of a dielectric rod passed through an aperture of radius r<0.1R in a short-circuit with the possibility of axial rotation, where R is the radius of a circular waveguide, is located in the circular waveguide section. In the wall of the coupler of orthogonal linearly polarized waves, two communication holes are made, connected through identical segments of the rectangular waveguide to the input arms of the bridge device, and with the centers located in one transverse plane lying at a distance λv/4 from the reflective surface of the short-circuit, and at a distance πR/2 one from the other, where λv is the wavelength in the circular waveguide at the mean operating frequency. The phase-shifting inhomogeneity is selected in such a way as to ensure a phase shift of 90°, and the bridge device is made in the form of an unbalanced quadrature waveguide bridge, whose input arms through identical sections of the rectangular waveguide and identical to the low-noise amplifiers are connected to couplers of the coupler of orthogonal linearly polarized waves, so that the inputs of low-noise amplifiers are located at the closest distance from the coupler couplers of orthogonal linearly polarized waves.

EFFECT: reduction of the noise temperature of the device for receiving orthogonal linearly polarized waves.

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Description

The invention relates to microwave technology and can be used in satellite communications and in systems of direct television broadcasting with polarization sealing.

Known devices [1] - [5], which can be used to receive orthogonal linearly polarized waves of arbitrary orientation. A feature of these devices is the presence of a rotating segment of a circular waveguide with a phase-shifting inhomogeneity installed in it, which introduces a phase shift of 180 °. By rotating this segment of the circular waveguide, and with it the phase-shifting inhomogeneity, the required orientation of the orthogonal linearly polarized waves is achieved.

One of the drawbacks of these devices is the use of drives in them, which, in addition to the necessary rotation of the phase-shifting heterogeneity, carry out the rotation of the circular waveguide segment, which requires additional drive power. Another disadvantage of these devices is that to ensure rotation of the circular waveguide segment, rotating joints should be located at its ends, which use throttle connections that are rather narrow-band in terms of matching.

Closest to the claimed device is a device for receiving orthogonal linearly polarized waves [6], containing two low-noise amplifiers (LNA), a bridge device in the form of a double waveguide tee, the output E and H shoulders of which are connected to the LNA inputs, as well as coaxially located and connected between them a segment of a circular waveguide and a coupler of orthogonal linearly polarized waves, made on a circular waveguide and equipped with a short circuit, while in the segment of a circular waveguide is placed in a dia phase-shifting inhomogeneity fixed on the end of the dielectric rod, passed through an opening of radius r <0.1R in the short circuit with the possibility of axial rotation, where R is the radius of the circular waveguide, and two coupling holes are made in the coupler wall of orthogonal linearly polarized waves, connected through identical segments of a rectangular waveguide with the input arms of the bridge device, and with the centers located in one transverse plane lying at a distance of λv / 4 from the reflective surface short-circuit, and at a distance πR / 2 from one another, where λw - wavelengths in a circular waveguide at an average operating frequency.

The disadvantage of this device, as well as all the devices discussed above, is the rather high level of noise temperature, which affects the quality of reception.

The technical result is to reduce the noise temperature of the device for receiving orthogonally linearly polarized waves. The technical result is achieved by reducing the length of the section between the input of the device and the inputs of the LNA, which will lead to a decrease in the losses of this section and, consequently, to a decrease in the noise temperature of the device. Reducing the length of this section can be achieved, firstly, by using a phase-shifting heterogeneity introducing a phase shift of 90 ° instead of a phase-shifting heterogeneity introducing a phase shift of 180 °, which will almost halve the length of a segment of a circular waveguide and the length of the phase-shifting inhomogeneity located in it secondly, due to the transfer of the LNA from the output of the device directly to the location of the communication holes in the coupler of orthogonal linearly polarized waves.

In FIG. 1 shows a front view and side view (longitudinal section) of the inventive device, which contains:

- low noise amplifiers - 1;

- bridge device - 2;

- segment of a circular waveguide - 3;

- coupler of orthogonal linearly polarized waves - 4;

- short circuit - 5;

- phase shifting heterogeneity - 6;

- dielectric rod - 7;

- two communication holes - 8;

- identical segments of a rectangular waveguide - 9, 10;

- input shoulders of the bridge device - 11.

The inventive device contains two identical LNAs (1) with waveguide inputs and outputs, a bridge device (2) made in the form of an unbalanced quadrature waveguide bridge with communication along a wide or narrow wall, as well as a segment of a circular waveguide coaxially located and interconnected (3 ) and a coupler of orthogonal linearly polarized waves (4), made on a circular waveguide and equipped with a short-circuit (5), while in the segment of a circular waveguide the phase-shifting nonuniform axis (6), which provides a 90 ° phase shift, and is fixed at the end of the dielectric rod (7), passed through an opening of radius r <0.1R in the short circuit with the possibility of axial rotation, where R is the radius of the circular waveguide and linearly orthogonal in the wall of the coupler For polarized waves, two communication holes (8) are made, connected through the LNA (1), the waveguide inputs of which are located at the closest possible distance from the communication holes (8), and identical segments of a rectangular waveguide (9), (10) with the input arms of the bridge device ( 11), with e the centers of the communication holes (8) coincide with the centers of the cross sections of the waveguide inputs of the LNA (1) and are in the same transverse plane lying at a distance λv / 4 from the reflective surface of the short circuit and at a distance πR / 2 from one another, where λv is the length waves in a circular waveguide at an average operating frequency.

For simplicity, we consider the operability of the claimed device under the assumption that all the inputs and outputs of the component parts (elements) of the device are consistent, and the components themselves do not introduce ohmic losses. In this case, the operability of the device is easiest and can be confirmed in a compact form using the apparatus of Jones matrices and vectors [7] - [9].

The inventive device is intended for receiving orthogonal linearly polarized waves (LPT). The orientation of the electric field vectors of these waves determines a certain rectangular coordinate system (SC), one axis of which is parallel to the electric field vector of one wave, the other axis is parallel to the electric field vector of another wave. We call this coordinate system SK1.

The Jin matrix, composed of Jones vectors, in which the first (left) column is the Jones vector corresponding to the 1st LPV, and the second (right) column is the Jones vector corresponding to the 2nd LPV, has a diagonal form in SK1.

The matrix composed of Jones vectors at the output of the device (Jout) is related to the matrix composed of Jones vectors at the input of the device (Jin) by the following matrix relation:

where T is the Jones matrix (transfer matrix) of the entire device.

If both LPs at the input of the device have a unit amplitude and a zero phase, then the matrix Jin has the form:

and in this case Jout = T.

In order for the claimed device to receive orthogonal LPTs with a high level of cross-polarization isolation (CRC), the Jout matrix should be close to the diagonal one.

CRC for the first decision-maker is defined as | 201g (T ₁₁ / T ₁₂ ) |, for the second - as | 201g (T ₂₂ / T ₁₂ ) |.

Theoretically, CRC = ∞ if Jout has a diagonal form.

или

or

Consider the Johns matrix of the claimed device in order to confirm its performance and determine the conditions under which the maximum cross polarization isolation is ensured.

The Jones matrix of the entire device is a sequential product of Jones matrices (transfer matrices) of its elements or its components (sections) consisting of several sequential elements.

The transfer matrix T is determined up to a complex factor by which all its elements are multiplied, since this factor does not affect the cross-polarization characteristics of the device.

In expression (3), the matrices T (π / 4), T (-π / 4) and T (β) are the matrices of transition from one SC to another by the operation of rotating the coordinate system by angles + 45 °, -45 ° and β, respectively.

These matrices are of the form:

where α = π / 4, α = -π / 4 and α = β, respectively.

In the expression (3), using the indicated matrices, a transition is made to the following four rectangular coordinate systems having a common center located on the common axis of a segment of a circular waveguide 3 and a coupler of orthogonal linearly polarized waves (OOLPV) 4:

1. SK1 - as defined above (the orientation of its coordinate axes coincides with the orientation of the electric field vectors of two orthogonal LPs arriving at the input of the claimed device),

2. SK2 - coordinate system, one of the axes of which lies in the plane in which the phase-shifting heterogeneity 6 is placed,

3. SK3 - coordinate system, one of the axes of which lies in the plane of symmetry OOLPV 4,

4. SK4 - coordinate system, the axis of which pass through the centers of the communication holes 8.

The first rightmost matrix in (3) T (π / 4) is the transition matrix from SK1 to SK2. The second matrix on the right (Tf) is the transmission matrix of the phase-shifting inhomogeneity 6, introducing a phase shift of 90 °. In SK2, it has a diagonal view:

The third matrix on the right is T (-π / 4) - in expression (3) is the inverse transition matrix from SK2 to SK1.

The next matrix T (β) is the transition matrix from SK1 to SK3. The angle β in this matrix is the angle between the coordinate axes of the coordinate systems SK1 and SK3. Since the orientation of the orthogonal LPs at the input of the device is arbitrary, the angle β can be any.

The fifth matrix to the right of To in (3) is the transmission matrix of the OOLV in SC3. Since one of the coordinate axes of SK3 lies in the plane of symmetry of the OOLPV, the transmission matrix To in this coordinate system has the diagonal form:

In this expression, ψ _c is the phase of the transmission coefficient from the OOLV input to the LNA inputs, when the electric field vector of the incident wave at the OVL input is in the symmetry plane of the OVL. ψ _p is the phase of the transmission coefficient from the OOLV input to the LNA inputs, when the vector of the electric field of the incident wave at the OVL input is in the plane perpendicular to the symmetry plane of the OVL. Obviously, in the first case, in-phase excitation of the communication holes 8 takes place, in the second, antiphase. Denote by δ the phase difference of the considered transmission coefficients (δ = ψ _c -ψ _p ), which, as will be shown below, is the main factor determining the cross-polarization characteristics of the claimed device.

The next matrix T (π / 4) in expression (3) is the transition matrix from SK3 to SK4. If the matrix To determines the phases of the transmission coefficients from the input of the OOLV to the inputs of the LNA during the in-phase (ψ _c ) and antiphase (ψ _p ) excitation of the communication holes, then the matrix T (π / 4) determines the values of the modules of the coefficients of the transmission from the input of the OVL to the inputs of the LNA. From the values of the elements of this matrix, it follows that both in-phase and in-phase excitation of the communication holes, exactly half the power of the wave that excites the communication holes 8 from the side of the circular waveguide OOLPV comes to the input of each LNA.

The product of the TvTu matrices in (3) is the transfer matrix of the device portion enclosed between the communication holes 8 and the input arms of the bridge device 11. Each of the Tu matrices (the matrix of the device portion enclosed between the communication holes 8 and the outputs of the LNA 1) and TV ( the matrix of the device section enclosed between the inputs of the segments of the rectangular waveguide 10 and the outputs of the segments of the rectangular waveguide 9) has a diagonal shape, and due to the identity of the segments of the rectangular waveguide 9, 10 and the identity of LNA 1, the diagonal elements The nts of each of these matrices are the same. Thus, the transmission matrix Tw⋅Tu can be represented as:

where A is a complex factor whose module is equal to the gain of the LNA, and the phase is equal to the sum of the phases of the transmission coefficients of the LNA and segments of a rectangular waveguide 9, 10.

Multiplying transfer matrices in (3) and using matrix equality

up to a complex factor, we find the transfer matrix of the section “device input - input arms 11 of the bridge device)”:

where θ = π / 4 + (ψ _with -ψ _n ) / 2 = θ = π / 4 + δ / 2

The last leftmost matrix Tm in expression (3) is the transmission matrix of the bridge device, which for the quadrature waveguide bridge has the form:

where the “+” sign refers to a quadrature bridge with communication along a wide waveguide wall (case of a stub bridge, see Fig. 1), the “-” sign refers to a quadrature bridge with communication along a narrow waveguide wall (case of a gap bridge).

Taking into account (4) and (5), the transfer matrix of the entire device T can be represented, up to a complex factor, in the form:

Multiplying the two transfer matrices on the left in (6) and taking into account that θ = π / 4 + δ / 2, we obtain the desired transfer matrix of the entire device:

in the case of using a quadrature bridge with communication over a wide wall of the waveguide and

in the case of using a quadrature bridge with communication along a narrow waveguide wall.

From (7) and (8) it follows that the CRC of the claimed device when using an ideal quadrature waveguide bridge with a transitional attenuation of 3 dB is equal to:

Theoretically, it is possible to achieve X = ∞ only by using an unbalanced quadrature waveguide bridge, in which the transition attenuation is not equal to 3 dB. The transfer matrix of such a bridge is:

where γ ≠ π / 4, the “+” sign refers to a quadrature bridge with coupling along a wide waveguide wall, the “-” sign refers to a quadrature bridge with coupling along a narrow waveguide wall.

Substituting γ instead of π / 4 in (6) and performing matrix multiplication, we obtain:

From (11) it follows that when using an unbalanced quadrature waveguide bridge, the CRC of the claimed device is (theoretically) infinity if: θ-γ = 0 in the case of a bridge with wide wall coupling and θ + γ = π / 2 in the case of a bridge with coupling on a narrow wall.

Substituting θ = π / 4 + δ / 2 into the equalities θ-γ = 0 and θ + γ = π / 2, we obtain γ = π / 4 + δ / 2 and γ = π / 4-δ / 2, respectively.

From formula (9) it follows that if γ differs from the obtained values (π / 4 ± δ / 2) by no more than one degree, then the cross-polarization isolation value at the output of the inventive device will be at least 35 dB, which is sufficient for high-quality reception signals of both polarizations.

Estimate the degree of "imbalance" of the quadrature waveguide bridge used in the inventive device. It is determined by δ / 2.

To estimate the value of δ / 2, we consider the case when an LBI (wave H11 in a circular waveguide) enters the OOLV 4 input, the plane of polarization of which coincides with the diametrical plane passing through the center of one of the two communication holes 8 (i.e., the electric field vector is parallel one of the axes of SK4). For definiteness, we call the coupling hole lying in the plane perpendicular to the plane of polarization of the incident wave the first, and the coupling hole lying in the plane of polarization of the incident wave, the second. The incident wave H11 in a circular waveguide with a given polarization will excite the first communication hole and will not excite the second. However, the reactive fields scattered by the first communication hole in the circular waveguide in the form of non-propagating higher types of waves H21, H41, H61 ... also excite the second communication hole. As a result, the main part of the power of the incident wave H11 in the circular waveguide will go through the first communication hole to the input of one LNA, and a much smaller part of the power of the incident wave H11 will go through the second communication hole to the input of another LNA. In both cases, the power carrier from the communication holes to the LNA will be wave H10, since the LNA inputs are made in the form of rectangular waveguides. Calculations and experiments show that the ratio of these powers is approximately equal to 18 ÷ 20 dB. It means that

| 201g tg (δ / 2) | ≈18 ÷ 20 (dB), whence δ / 2≈5 ° ÷ 8 °.

It follows from the foregoing that the technical result of the present invention, reducing the noise temperature, is achieved by reducing the number of elements and reducing the distance between the input of the entire device and the inputs of low-noise amplifiers, which leads to an increase in the noise figure of merit of the device and, therefore, to increase the signal-to-noise ratio by his exit. As a result, the output of the claimed device improves the quality of the signals received on the waves of both polarizations. The level of cross-polarization isolation at the output of the device also affects the signal-to-noise ratio and, therefore, the signal quality. Therefore, the use of an unbalanced quadrature waveguide bridge, providing a level of cross-polarization isolation at the output of the device at least 35 dB, is a necessary condition for the implementation of the present invention.

Literature

1. US patent No. 3215957, CL. 333-21.

2. US patent No. 4090137, CL. 325-60.

3. US Patent No. 4233576, cl. 333-16.

4. US patent No. 4507665, cl. 343-786.

5. US patent No. 5583515, CL. 342-361.

6. Antonenko V.M., Berlyavsky I.Z. and others. "Device for receiving orthogonal linearly polarized waves" AC N 1821846 from 12.02.90 Н01Р 1/16. Publ. 06/15/93. Bull. N22.

7. Gorshkov M.M. "Ellipsometry" - M.: Sov. Radio, 1974, pp. 62-76.

8. Kornblit "Microwave optics. Optical principles as applied to the design of microwave antennas." - M.: Communication, 1980, pp. 245-274.

9. Azzam, Bashar "Ellipsometry and polarized light." - M .: Mir, 1981

Claims (1)

A device for receiving orthogonal linearly polarized waves, comprising two low-noise amplifiers with waveguide inputs, a bridge device, as well as a segment of a circular waveguide coaxially arranged and interconnected, and a coupler of orthogonal linearly polarized waves, made on a circular waveguide and equipped with a short circuit, while in a segment of a round waveguide a phase-shifting heterogeneity is placed in the diametrical plane, fixed at the end of the dielectric rod passed through the hole with r <0.1R in the short circuit with the possibility of axial rotation, where R is the radius of the circular waveguide, and two communication holes with centers located in one transverse plane lying at a distance λв / 4 from the reflecting surface are made in the wall of the coupler of orthogonal linearly polarized waves short-circuit, and at a distance πR / 2 from one another, where λw is the wavelength in a circular waveguide at an average operating frequency, and connected through identical segments of a rectangular waveguide, with the input arms of the bridge device, distinguishing the fact that the length of the phase-shifting heterogeneity is set so as to provide a phase shift of 90 °, and the bridge device is made in the form of an unbalanced quadrature waveguide bridge, the input arms of which, through identical segments of a rectangular waveguide and identical low-noise amplifiers with waveguide inputs and outputs, are connected to communication holes of the coupler of orthogonal linearly polarized waves so that the centers of the communication holes coincide with the centers of the cross sections of the waveguide inputs in low-noise amplifiers, while the communication holes of the coupler of orthogonal linearly polarized waves and the waveguide inputs of low-noise amplifiers are located as close as possible to each other.

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