Ridge gap waveguide with mechanically adjustable operating frequency range

Abstract

The invention relates to a mechanical structure enabling the adjustment of the operating frequency range of ridge-gap waveguides used for the transmission of electromagnetic waves in other high-frequency applications, particularly satellite, radar, aviation, and communication systems, and a waveguide containing this structure.

Description

[0001] RIDGE GAP WAVEGUIDE WITH MECHANICALLY ADJUSTABLE OPERATING FREQUENCY RANGE

[0002] Technical Field

[0003] The invention relates to a structure enabling the mechanical adjustment of the operating frequency ranges of ridge gap waveguides used for the transmission of electromagnetic waves in other high-frequency applications, particularly satellite, radar, aviation, and communication systems.

[0004] Prior Art

[0005] Waveguides are hollow metallic conductor structures where high-frequency electromagnetic waves are carried and guided. Waveguides are generally of rectangular or circular crosssection, and the dimensions of the guide determine which wavelengths and which modes it can support. Due to the manufacturing difficulties of waveguides with metallic conductive surfaces, perfect electrical conductor (PEC)-perfect magnetic conductor (PMC) parallel plate waveguide structures have started to be developed today. However, since PMC material does not exist in nature, this behavior is provided by Artificial Magnetic Conductors (AMC) formed by the periodic positioning of three-dimensional (3D) metallic conductor pins. AMCs, which are a type of high impedance surface, exhibit PMC behavior in certain frequency bands. In such parallel plate waveguide applications, while the lower and upper conductors behave like PEC, the periodic pin arrays behave like PMC, and the revealed PEC- PMC structure ensures the waveguide operates in a certain frequency range by suppressing unwanted cavity modes that would occur inside the waveguide.

[0006] Since the physical lengths of the periodic pin structures in PEC-PMC structure waveguides are fixed, the waveguides operate only in a certain frequency range. Therefore, different designs and productions are required to be made for different frequency bands (L band, S band, C band, X band, Ku band, Ka band, K band, etc.). This situation causes additional cost and time losses.

[0007] The document numbered JP2002171106 A relates to a waveguide used in a microwave band or a millimeter-wave band and a method directed towards the adjustment of the waveguide. It is stated that as the operating frequency increases, the metal piece becomes smaller, and therefore, it is difficult to perform the bonding process to the desired location. Therefore, the invention comprises an adjusting element made of dielectric material at a predetermined position on the inner surface of the waveguide. Since the adjusting element serving to adjust the electrical characteristic of the waveguide is formed using a dielectric material, even if the adjusting element deviates slightly, the electrical characteristic does not show fluctuation, and the desired electrical characteristic can be obtained. The adjusting element is attached to the inner circumferential surface of the waveguide.

[0008] In the document numbered US9806393B2, a microwave / millimeter-wave waveguide in which a narrow gap is formed between two parallel surfaces of conductive material by using a texture or a multi-layer structure on one of the surfaces is described. The microwave / millimeter-wave waveguide further comprises one or more conductive elements such as a metal ridge on one of the two surfaces, a groove, or a metal strip located in a multilayer structure between the two surfaces. Electromagnetic waves propagate along the conductor, and at least one of the surfaces is equipped with means to prevent the waves from propagating in directions other than the ridge, groove, or strip.

[0009] The microwave / millimeter-wave waveguide operates in all of one or more sub-frequency bands of the 1 GHz to 100 THz frequency range. The microwave / millimeter-wave waveguide comprises two opposing conductive material surfaces arranged to form a narrow gap between them.

[0010] In the document titled “Ayarlanabilir gah§ma frekans arahgina sahip mukemmel manyetik iletken yiizeyli metal mahfaza tasanmi” ( akir, M. (2020). Master's Thesis. Sakarya University Institute of Science and Technology), a PMC surfaced metal enclosure design containing a circular cross-section pin array having an adjustable operating frequency range is proposed. For the proposed model, firstly a 5^5 pin array was used, and the electrical performance of the metal enclosure was analyzed numerically. In the document, a movable plate design positioned on the pins is presented. This design comprises screws, adjustable plates, and pins. PMC surfaced cover designs containing a circular cross-section pin array having band-stop filter characteristics were made to suppress unwanted resonances that each cavity would create at its own operating frequency. In the designs, it was aimed to obtain the desired operating frequency ranges only by changing the pin lengths. For this purpose, as seen in the mentioned figure, movable plates were positioned on the pins, and it was targeted to change the pin lengths by moving them in the up and down direction. The movements of the plates in the up and down direction are provided by adjustment screws found on them. To determine the positions of the movable plates on the pins, the lower and upper limits of the operating band ranges of the first, second, and third cavities are required to be defined. For this purpose, the operating frequency ranges of the cavities having center operating frequency values of 11 GHz, 16 GHz, and 21 GHz were determined as 6.96-15.00 GHz, 19.79-25 GHz, and 13.61-25 GHz, respectively. In this document, movable plates directed towards use for the suppression of cavity resonances are described.

[0011] Objectives of the Invention

[0012] The object of this invention is to develop a waveguide enabling the mechanical adjustment of the operating frequency range of PEC -PMC structure waveguides. In this way, the operation of the waveguide in different frequency bands will be ensured with a single waveguide design and production.

[0013] Another object of this invention is to develop a waveguide enabling wideband or multi -band applications by increasing the operating frequency range. The wideband or multi-band characteristic will be provided by positioning the movable plates at heights different from each other.

[0014] Detailed Description of the Invention

[0015] The waveguide implemented to achieve the objects of this invention is shown in the attached figures.

[0016] Figure 1 The schematic perspective view of a waveguide according to an embodiment of the invention containing a ridge.

[0017] Figure 2 The side view of a waveguide according to an embodiment of the invention containing a ridge.

[0018] Figure 3 The top cross-sectional view of a waveguide according to an embodiment of the invention containing a ridge.

[0019] Figure 4 The perspective view of the adjustment plate and adjustment screw used in a waveguide according to the invention. The parts located in the figures are individually numbered, and the counterparts of these numbers are given below.

[0020] 1. Body

[0021] 2. Ridge

[0022] 3. Pin

[0023] 4. Adjustment screw

[0024] 5. Adjustment plate

[0025] 6. Pin hole

[0026] The waveguide subject to the invention basically comprises: a conductive body (1) defining a cavity in the form of a rectangular prism, at least one conductive ridge (2) in the form of a rectangular prism separating the cavity into at least two sections, a plurality of pins (3) found in each section of the cavity, an adjustment plate (5) positioned in each section of the cavity in a manner passed onto the pins (3) by means of pin holes (6) found on it and corresponding to each pin (3), an adjustment screw (4) extending parallel to the pins (3), one end of which is connected to the related adjustment plate (5) and one end of which is found outside the body (1) to allow adjustment, in order to ensure the adjustment of the height of the adjustment plates (5) relative to the bases of the pins (3).

[0027] The adjustment screws (4) extend to the outside of the body (1) by passing through a screw hole on the upper conductive surface of the body (1). Threads fitting onto the surface of the adjustment screws (4) are also found on the inner surfaces of these screw holes. In this way, as a result of the rotation of the adjustment screws (4) from their ends located outside the body (1), the adjustment screws (4) can move back and forth inside the related screw hole, and both the adjustment of the positions of the adjustment plates (5) and their fixation in these positions are ensured. In an embodiment of the invention, nuts located on the adjustment screws (4) and capable of being tightened onto the related screw hole are also found in order for the adjustment screws (4) and consequently the adjustment plates (5) to be fixed in a more reliable manner. The waveguide subject to the invention allows the positioning of the adjustment plates (5) independently of each other. In this way, by positioning the adjustment plates (5) at heights different from each other, the waveguide can also be used in wideband or multi-band applications. In particular, embodiments of the invention containing more than one ridge (2) and more than two adjustment plates (5) will enable the waveguide to exhibit wideband or multi-band characteristics with the use of the adjustment plates (5) at different heights.

[0028] The structure proposed for the mechanical adjustment of the operating frequency ranges of ridge gap waveguides within the scope of this invention is shown schematically with the attached figures. The air gap distance (hgap) between the upper conductive surfaces of the body (1) and the periodic pin (3) arrays in PEC-PMC structure waveguides seen in Figure 3 plays a very important role in determining the suppression frequency range of unwanted cavity modes that will occur inside the waveguide. According to theoretical results well known or easily derivable from Maxwell's equations, the distance of the gap between the upper conductive surfaces and the periodic pin (3) arrays must be hgap < lambda / 4 for the suppression of transverse magnetic (TM) modes that will occur inside the waveguide, and hgap < lambda / 2 for the suppression of transverse electric (TE) modes. When the center frequency value of the operating frequency range is taken into account, the lengths of the metal pins (3) are required to be equal to hpin = lambda / 4. Here, lambda represents the wavelength of the center operating frequency of the waveguide.

[0029] As the height of the air gap decreases, the band-stop frequency range increases, and the structure becomes more suitable for electromagnetic wave transmission. PEC-PMC structure waveguides are designed in three different forms: groove-gap waveguide, ridge-gap waveguide, and inverted-microstrip waveguide. While the lower and upper conductive surfaces of the waveguide behave like PEC, the periodic pin (3) structures stop the transmission of the electromagnetic wave in the operating frequency range by behaving like PMC. In this case, while wave transmission is provided only via the groove in the groovegap waveguide, it is provided only via the ridge (2) in the ridge-gap waveguide. Similarly, in the inverted-microstrip waveguide, wave transmission is provided via the microstrip transmission line.

[0030] In the waveguide subject to the invention, as also shown in the figures, metal adjustment plates (5) are positioned on the pin (3) structures of the ridge-gap waveguide, and with the up and down movement of the adjustment plates (5), the changing of the pin (3) lengths and, in this way, the mechanical adjustment of the operating frequency range of the ridge-gap waveguide are ensured. The metal adjustment plates (5) positioned on the pin (3) structures behave like PEC, while the parts of the pins (3) remaining between the adjustment plates (5) and the upper conductive surface of the waveguide behave like PMC, stopping the transmission of the unwanted electromagnetic wave. Adjustment screws (4) are positioned on the adjustment plates (5) to ensure the up-down movement of the adjustment plates (5), and the movement of the adjustment plates (5) is provided mechanically with the rotation of the adjustment screws (4) clockwise or counter-clockwise. The sensitivity of the up-down movement of the adjustment plates (5) can be determined by the root diameter, thread depth, and thread angle of the adjustment screws (4). Consequently, the ridge-gap waveguide design proposed within the scope of this invention paves the way for the operation of waveguides in different frequency bands with a single production, by ensuring the mechanical adjustment of the operating frequency range of the waveguides and ensuring the operating frequency range to exhibit wideband or multi-band characteristics depending on the positions of the adjustment plates (5).

Claims

CLAIMS1. A ridge-gap waveguide, comprising: a conductive body (1) defining a cavity in the form of a rectangular prism, at least one conductive ridge (2) in the form of a rectangular prism separating the cavity into at least two sections, a plurality of pins (3) found in each section of the cavity, characterized in that it comprises: an adjustment plate (5) positioned in each section of the cavity in a manner passed onto the pins (3) by means of pin holes (6) found on it and corresponding to each pin (3), an adjustment screw (4) extending parallel to the pins (3), one end of which is connected to the related adjustment plate (5) and one end of which is found outside the body (1) to allow adjustment, in order to ensure the adjustment of the height of the adjustment plates (5) relative to the bases of the pins (3).

2. The waveguide according to claim 1, characterized in that it comprises screw holes located on the upper conductive surface of the body (1), through which the adjustment screws (4) pass.

3. The waveguide according to claim 2, characterized in that it comprises threads located on the inner surfaces of the screw holes, fitting onto the surface of the related adjustment screw (4).

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