RU2487447C2 - Small-size wideband waveguide-horn antenna and antenna array structure based thereon - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: wideband horn antenna array has an open waveguide, having a radiating end and a tail end, top and bottom conducting crests inside the waveguide; behind the tail part of the waveguide there is a conducting frame; between the tail part of the bottom crest and the back wall of the frame there is a gap; waveguide and tail parts of the crests facing each other are parallel to the base. In the back wall of the frame opposite the end face of the tail part of the bottom crest there is an opening for entry of the centre conductor of a communication cable with a transceiver through an insulator. A cable shield is mounted on the back wall of the frame and has electrical contact with the back wall. The concave part of the crest lies near the radiating end of the waveguide and the convex part of the crest connects the end of the crest on the base with the concave part. The antenna array has columns in which horns are spaced apart by a distance close to half the minimum signal wavelength.

EFFECT: reduced weight and size characteristics of the wideband waveguide horn, enabling operation thereof as part of antenna arrays.

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Description

The present invention relates to radar, in particular to waveguide-horn antenna elements used in mirrored antennas and antenna arrays (AR).

The development trend of modern radar detection and guidance is the combined use of active and passive radar methods, respectively, expanding the range of operating frequencies of antenna devices. This is especially true for radars built on the basis of phased AR arrays, the radiating elements of which are waveguide horns. An example of the construction of broadband waveguide horns are devices [1, 2, 3].

The waveguide horn [1] is an AR element operating in the frequency band 3-6 GHz, represents a rectangular waveguide, closed at one end by a short-circuited conductive plug. In the center of the wide walls of the waveguide and orthogonally, the upper and lower conductive ridges are not in contact with each other. Each crest represents a flat three-stage structure diverging in the direction of the radiation direction, which does not extend beyond the waveguide and does not come into contact with the short-circuited plug. The width of the ridges is less than half of the wide wall of the waveguide. The steps of the crest are either parallel or otrogonal to the wide wall of the waveguide. The second and third stage of the ridges (the step number is counted from the waveguide plug) are located symmetrically with respect to the longitudinal axis of the waveguide and represent a two-stage transformer matching the impedance of free space with the output of the first stage through which the waveguide signal is input / output. The first sections of the ridges are part of a waveguide transition to a strip or coaxial communication line with a transceiver, the ends of which are located at different distances from the stub and are not connected to it. The crests of the first stage have grooves symmetrically located relative to the longitudinal axis of the waveguide, the open parts of the grooves are facing each other, the length of the grooves does not exceed the length of the first stage, the depth of the grooves allows the L-shaped probe to pass from the strip or coaxial communication line mounted on the plug to lower crest in isolation. In this case, a part of the probe passes through the slot of the upper ridge parallel to the longitudinal axis of the waveguide, the second part of the probe passes orthogonally to the longitudinal axis of the waveguide through the first and second slots with a recess relative to the end of the lower ridge equal to the width of the probe. There is a window in the plug through which the horizontal part of the probe is connected to the connection with the strip communication line, or a cable. If the antenna is connected to the transceiver via a coaxial communication line, the screen of the coaxial cable is connected to the outer wall of the stub and ends behind the inner wall of the stub, the continuation of the central core of the coaxial cable is a L-shaped probe connecting the coaxial line to the lower ridge.

The advantage of the waveguide horn is its small longitudinal and transverse dimensions, ensuring its operation as part of the AR. However, the operating frequency range covers one octave, which is not enough for application in the passive channel of the radar detection and guidance.

A second example of a broadband horn is a waveguide horn [2], in which a pair of symmetrical conducting ridges are mounted on the inner surface of a rectangular horn. The plane in which the ridges are located, orthogonal to the upper and lower walls of the horn, passes through the longitudinal axis of the horn. The bases of the ridges are linear segments located on the inner, conducting wall of the horn, the sides of the ridges facing each other diverge from the mouth of the horn toward the aperture in a smooth curved line. Outside the horn above each ridge, additional conductive triangular ridges are attached, orthogonally corresponding to the outer wall. Additional ridges are the same size. One side of the additional ridge is located in the plane of the mouth of the horn and is orthogonal to its longitudinal axis, the second side connects the top of the additional ridge with its base. The length of the base of the additional ridge is less than the length of the linear part of the main ridge. On the entire curved surface of the main ridges or a part close to the throat, there are furrows up to a quarter of the wavelength; an insert is turned into the furrow that points to the opposite crest. In addition, the lateral surfaces of the ridges are lined with ferromagnetic materials with a relative magnetic permeability of more than 1. Coaxial input / output of the microwave signal to the horn is made through a waveguide-coaxial transition in which ferromagnetic material is introduced between the coaxial input / output of the microwave signal and the blanked part of the waveguide.

The advantage of the horn [2] is a wide range of operating frequencies of 1-18 GHz. However, the presence of additional ridges that reduce the lower boundary of the operating frequencies does not allow the use of a horn in the composition of the AR, where the distance between the horns should be close to half the minimum operating wavelength.

As a broadband horn, adopted as a prototype, is a waveguide horn [3], which is used as part of a monopulse antenna system and ensures its operation in the frequency range from 3.6 to 15 GHz. Each rectangular horn has a radiating and energizing, non-damped end. The waveguide is excited by the microwave signal of the transceiver through a waveguide-cable junction mounted on a wide wall of the waveguide near the end of the supply end of the waveguide. In the waveguide orthogonal to one of the wide walls, parallel to its longitudinal axis is a single conductive comb, representing a three-stage impedance transformer. The first section matches the coaxial input of the antenna with the waveguide, the second and third sections coordinate the impedance of the waveguide section with a horn. In the horn, unlike the waveguide, there are two ridges extending beyond the mouth of the horn, the distance between the ends of the ridges behind the mouth of the horn exceeds the vertical size of the mouth of the horn, the line connecting the ends of the ridges outside the horn is orthogonal to the longitudinal axis of the waveguide. The lower crest of the horn is also a continuation of the lower crest of the waveguide, the upper crest is in the plane of the lower crest, orthogonal to the upper wall of the horn and fixed on it. The shape of the ridges facing each other is described by an exponential law. Between the ridges in the horn and outside it there is a gap that increases in the direction of radiation and ensures the coordination of the impedance of the rectangular horn with free space. The exponential side of the upper ridge begins from the base of the ridge. The central core of the waveguide-coaxial transition is connected to the tail of the lower crest.

The advantage of the waveguide horn [3] is a wide band of operating frequencies from 3.6 GHz to 15 GHz, provided by the use of conductive diverging ridges extending beyond the mouth of the horn.

The disadvantage of the horn is a significant excess of the distance between the ends of the ridges located beyond the mouth of the horn, half the minimum working wavelength of the microwave signal, which does not allow its use in the AR, where this requirement is mandatory.

The aim of the invention is to reduce the overall mass characteristics of a broadband waveguide horn, ensuring its operation as part of the AR.

The goal is realized in that in a broadband waveguide horn [3] by eliminating the matching transformer, changing the design of the microwave signal supply to the lower ridge and the shape of the ridges facing each other, the longitudinal length of the horn and the distance between the ends of the ridges beyond shout.

This goal is achieved by the fact that a broadband horn [3], containing an open waveguide, one end of which is called radiating, and the second - tail, upper and lower conductive ridges installed inside the waveguide, the base of the ridges are mounted on the upper and lower walls of the waveguide and have them electrical contact, the ridges are in the same plane, orthogonal to the upper and lower walls of the waveguide, there is a gap along the entire length between the ridges, part of the ridges extends beyond the radiating end of the waveguide, a line connecting the ends of the ridges, extending beyond the radiating part of the waveguide, orthogonal to the longitudinal axis of the waveguide, the width of the ridges is less than half the width of the waveguide, the tail of the lower ridge is electrically connected to the central core of the communication cable with the transceiver, characterized in that a conductive frame consisting of an upper and lower flat is introduced behind the tail of the waveguide the base and the rear wall orthogonal to them, the base of the frame are a continuation of the upper and lower walls of the waveguide, the width of the rear wall corresponds to the width of the bases, the upper and the bottom ridges are in the plane passing through the longitudinal axis of the waveguide, the tail parts of the upper and lower ridges exit the waveguide, their bases are attached to the upper and lower walls of the frame, respectively, the sides of the ridges facing each other are symmetrical with respect to the longitudinal axis of the waveguide, the tail part of the upper the ridge is fixed and electrically connected to the rear wall of the frame, there is a gap between the rear part of the lower ridge and the rear wall of the frame, between the lower wall of the frame and the tail of the lower row there is a rectangular gap, the length of which along the longitudinal axis of the waveguide is equal to a quarter of the minimum wavelength of the signal, and the height is half the distance from the lower wall of the frame to the upper boundary of the lower crest, the waveguide and tail parts of the crests facing each other are parallel to the base, part of the crests, extending beyond the radiating end of the waveguide, have concave and convex sections, while the concave part is most closely located to the radiating end of the waveguide, is part of a circle whose radius is longitudinal axis of the waveguide, the convex part of the crest connects the end of the crest on the base with the concave part, in the rear wall of the frame opposite the end of the tail of the lower crest there is a hole for input through the insulator of the central core of the communication cable with the transceiver, the cable screen is fixed to the rear wall of the frame and has it electrical contact, the central core of the cable passing through the insulator on the rear wall of the frame is connected to the center of the end face of the tail of the lower ridge.

The antenna array based on the proposed horns contains columns in which the horns are spaced apart from each other by a distance close to half the minimum wavelength of the signal, differs in that. that the speakers of the columns are located under each other in such a way that the lower sides of the waveguide and the frame of the upper horn are the upper sides of the waveguide and the frame located underneath the horn, the pair of lower and upper ridges included in the horns located under each other are performed as a single structure, fixed on the common wall of the waveguide and the frame.

The invention is illustrated by further description with reference to the following drawings.

Figure 1 shows the geometry of a single broadband speaker.

Figure 2 shows the column geometry of a broadband antenna array.

Figure 3 presents the geometry of a pair of lower and upper ridges included in adjacent horns of the antenna array column

Figure 4 presents the measurement results of the VSWR horn in the operating frequency range.

In figure 1, 2 and 3, the following notation:

1 - waveguide;

2 - Upper ridge;

3 - Lower ridge;

4 - The convex part of the ridge;

5 - Concave part of the ridge;

6 - Frame;

7 - The hole in the rear wall of the frame;

8 - cable;

9 - Bookcase design of the column of waveguides and the antenna array frame;

10 - Unified construction of a pair of lower and upper ridges included in adjacent horns;

R is the radius of the circle of the concave part of the ridge.

In figure 4, the following notation:

VSWR - standing wave voltage coefficient;

F - frequency value, GHz.

In figure 1, the upper 2 and lower 3 conductive ridges are installed inside the waveguide 1, the bases of the ridges 2 and 3 are mounted on the upper and lower walls of the waveguide 1 and have electrical contact with them, the ridges 2 and 3 are in the same plane with the longitudinal axis of the waveguide 1, orthogonal to its upper and lower walls, between ridges 2 and 3 there is a gap along the entire length, part of the ridges extends beyond the radiating end of waveguide 1, the line connecting the ends of ridges 2 and 3 extending beyond the radiating part of waveguide 1 is orthogonal to the longitudinal axis of waveguide 1, width combs 2 and 3 men its half width of the waveguide 1, the tail of the waveguide 1 is connected to the upper and lower walls of the conductive frame 6, consisting of an upper and lower flat base and the rear wall orthogonal to it, the base of the frame 6 is a continuation of the upper and lower walls of the waveguide 1, the width of the rear wall of the frame 6 corresponds to the width of the bases, the sides of the ridges 2 and 3, facing each other, are symmetrical relative to the longitudinal axis of the waveguide 1, there is a gap between the tail of the lower ridge 3 and the rear wall of the frame 6, between the lower The frame 6 and the tail of the lower ridge 3 have a rectangular gap, the length of which along the longitudinal axis of the waveguide is four of the minimum wavelength of the signal, and the height of the gap is half the distance from the bottom wall of the frame to the upper boundary of the lower ridge 3, the end of the tail of the upper ridge 2 is fixed on the back wall of the frame 6 and is electrically connected to it, the waveguide and tail parts of the ridges 2 and 3 facing each other are parallel to the base, the parts of the ridges 2 and 3 extending beyond the radiating end of the waveguide 1 are concave e 5 and convex 4 sections, while the concave part 5 of ridges 2 and 3, closest to the radiating end of waveguide 1, is part of a circle whose radius is on the longitudinal axis of waveguide 1, the convex part 4 of ridges 2 and 3 connects its end to base with a concave part 5, in the rear wall of the frame 6 opposite the end of the tail of the lower ridge 3 there is a hole 7 for input through the insulator of the Central core of the communication cable 8 with a transceiver, the screen of the communication cable 8 is fixed to the rear wall of the frame 6, has an electric contact and does not go beyond it, the central core of the communication cable 8 is connected to the center of the end face of the tail of the lower ridge 3.

In figure 2, the waveguides 1 and the frames 6 of the single horns are combined in a rack structure 9, in which the lower sides of the upper waveguide and the frame of the upper horn are the upper sides of the waveguide and the frame of the speaker underneath, while the upper 2 and lower 3 ridges of the outer horns of the antenna column the gratings are executed and installed individually, and the pairs of lower and upper ridges included in adjacent horns located one below the other are made as a single structure 10 (Fig. 3), mounted on a common wall of the waveguides 1 and the frame s 6.

The speaker operates in the following sequence. The excitation signal of a single horn (Fig. 1) comes from the transceiver via cable 8. The screen of cable 8 is electrically connected and fixed to the conductive housing 6. The central core of cable 8 in isolation through the hole in the housing 6 is electrically connected to the center of the end of the tail of the lower conductive ridge 3 . In the presence of a microwave signal of the transceiver, the electromagnetic wave is excited in the waveguide 1 and propagates through the waveguide 1 in the direction of the diverging ridges 2 and 3. The gaps between the tail of the lower ridge and the housing provide m high impedance point between the input microwave signal, and the frame wall, respectively, the permissible value of the standing wave voltage coefficient (VSWR) from the transceiver in the operating frequency range. The ridges 2 and 3 inside the waveguide 1 and beyond its opening increase the working frequency range of the horn, the concave part of the ridges allows to reduce the longitudinal size of the horn to 1.5λ (where λ is the minimum wavelength of the microwave signal). The experimental dependence of the VSWR in the waveguide horn in the operating frequency range of 2-20 GHz does not exceed 2.5 and is shown in Fig.4.

The design of the column AR on the basis of the proposed broadband speaker is shown in figure 2. For technological reasons, ensuring ease of manufacture, the waveguide parts 1 and the horn bodies 6 are made as a rack structure 9, the lower 3 and upper 2 horns combs located one above the other are made as a single structure 10. A more detailed form of the paired design of the ridges 10 is shown in FIG. .3.

The technical advantage of the proposed broadband horn and antenna array is to reduce the longitudinal size of the speaker, respectively antenna array, to 1.5 minimum signal wavelengths. In addition, the design of the horn and the AP provide a reduction in mass by reducing the size of the side wall of the waveguide, simplifying the manufacturing and tuning technology due to open access to the horn elements located in the frame.

The manufacture and testing of the speaker and antenna array confirmed their operability in a wide range of operating frequencies.

All elements included in the broadband waveguide horn and AR can be made of aluminum according to the existing technology known in the radio industry.

LITERATURE

1. US patent No. 5359339 from 10.25.94. "Broadband short-horn antenna"

2. US patent No. 7161550 from 01/09/07. "Dual and quad-ridged horn antenna with improved antenna pattern characteristics"

3. US patent No. 5406298 dated 11/04/95 "Small wideband passive / active antenna"

Claims (2)

1. A broadband horn of the antenna array containing an open waveguide, one end of which is called radiating, and the other end is the tail, the upper and lower conductive ridges installed inside the waveguide, the base of the ridges are mounted on the upper and lower walls of the waveguide and have electrical contact with them, the ridges are in one plane, orthogonal to the upper and lower walls of the waveguide, there is a gap between the ridges along the entire length, part of the ridges extends beyond the radiating end of the waveguide, a line connecting the ends of the ridges extending beyond the radiating part of the waveguide, orthogonal to the longitudinal axis of the waveguide, the width of the ridges is less than half the width of the waveguide, the tail of the lower ridge is electrically connected to the central core of the communication cable with a transceiver, characterized in that a conductive frame consisting of an upper and lower flat base is introduced behind the tail of the waveguide orthogonal to the back wall, the base of the frame is a continuation of the upper and lower walls of the waveguide, the width of the back wall corresponds to the width of the bases, the upper and lower ridges are in the plane passing through the longitudinal axis of the waveguide, the tail parts of the upper and lower ridges exit the waveguide, their bases are mounted on the upper and lower walls of the frame, respectively, the sides of the ridges facing each other are symmetrical with respect to the longitudinal axis of the waveguide, the tail of the upper ridge and is electrically connected to the back wall of the frame, there is a gap between the tail of the lower ridge and the back wall of the frame, there is a straight line between the bottom of the frame and the tail of the lower ridge the gap, the length of which along the longitudinal axis of the waveguide is equal to four of the minimum wavelength of the signal, and the height of the gap is half the distance from the lower wall of the frame to the upper boundary of the lower crest, the waveguide and tail parts of the crests facing each other are parallel to the base, parts of the crests emerging beyond the radiating end of the waveguide, have concave and convex sections, while the concave part is most closely located to the radiating end of the waveguide, is part of a circle whose radius is on the longitudinal axis of the waves yes, the convex part of the ridge connects the end of the ridge on the base with the concave part, in the rear wall of the frame opposite the end of the tail of the lower ridge there is a hole for input through the insulator of the central core of the communication cable with the transceiver, the cable screen is fixed to the rear wall of the frame and has an electrical contact with it , the central core of the cable passing the insulator on the rear wall of the frame is connected to the center of the end face of the tail of the lower ridge. 2. An antenna array containing columns in which the horns are spaced apart from each other by a distance close to half the minimum wavelength of the signal, characterized in that the horns contain the features of claim 1, are located under each other so that the lower sides of the waveguide and the frame the upper horn are the upper sides of the waveguide and the frame of the horn below it, a pair of lower and upper ridges included in the horns located under each other are performed as a single structure, mounted on a common wall of the waveguide and the frame.

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