A differentially-fed ultra-wideband radar antenna with directional radiation

Abstract

The present invention discloses a differentially-fed ultra-wideband radar antenna with directional radiation, which includes a dielectric substrate, a differential port, a connecting probe, a balun transmission line, a balun ground, an antenna feeder, and an antenna ground. The differential port, the connecting probe, the balun transmission line, the balun ground, and the antenna ground are all disposed on the dielectric substrate. One end of the differential port is connected to the balun transmission line, and the other end is connected to the balun ground through the connecting probe. The connecting probe is disposed through the dielectric substrate. The antenna feeder is disposed on the antenna ground and is connected to the balun transmission line. The antenna ground includes a first element, a second element, a third element, and a fourth element arranged side by side. The balun transmission line feeds power to the first element, the second element, the third element, and the fourth element through the antenna feeder. Compared with the prior art, the present invention has the advantages of simple structure, lower sidelobe level of the antenna and lower coupling between elements, and higher end-fire direction gain of the antenna while broadening the antenna spectrum bandwidth.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of antennas. Specifically, it relates to a differential antenna for ultra-wideband radar with directional radiation. Background Art

[0002] Ultra-wideband radar systems have the advantages of low power consumption, good electromagnetic compatibility, strong anti-interference ability, etc. And because modulation and demodulation are not required, the system structure is relatively simple, with the characteristics of low cost and easy maintenance. Therefore, ultra-wideband radars that are convenient to use, measure accurately, and are safe and reliable are very suitable for application scenarios such as vital sign detection, and can be widely used in future non-contact medical care, intelligent nursing, intelligent elderly care and other medical and health fields, greatly reducing the operating costs of institutions such as hospitals and nursing homes.

[0003] Ultra-wideband radar systems require antennas to cover an extremely large bandwidth. According to the definition of the Federal Communications Commission (FCC) in the United States: the relative bandwidth of a wireless communication system is greater than 25%, or the absolute bandwidth is greater than 500 MHz. In addition to the ultra-wideband requirements, the vital sign detection radar antennas applied in scenarios such as hospitals and nursing homes should also have the following characteristics:

[0004] First, the antenna should be a differential antenna. With the continuous development of communication technology, the volume requirements of electronic devices are getting smaller and smaller, and the weight requirements are also getting lighter and lighter. Since the circuit for processing differential signals can easily achieve a highly integrated single chip, the radio frequency ports of current radar chips are all differential ports.

[0005] Second, the antenna should be a directional antenna. To meet the need of setting multiple beds in a single room in a nursing home, the ultra-wideband radar vital sign detection system should be able to detect a certain bed without being interfered by adjacent beds, which requires the antenna to have a narrow beam characteristic in the horizontal direction.

[0006] Currently, there are several types of ultra-wideband antennas, such as spiral antennas, broadband planar monopole antennas, Vivaldi antennas, etc. that can achieve multiple octaves of ultra-wideband, as well as various improved antennas of these antennas. However, spiral antennas require a loaded reflection cavity, making the structure too complex and not conducive to mass production; planar monopole antennas are omnidirectional antennas, which are not conducive to applications such as radar that require directional radiation; Vivaldi antennas are relatively large in volume. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a differential antenna for ultra-wideband radar with directional radiation, which can solve the defects of the existing antenna structure being complex and not conducive to radar directional radiation.

[0008] The ultra-wideband radar differential antenna with directional radiation of the present invention includes a dielectric plate, a differential port, a connecting probe, a balun transmission line, a balun ground, an antenna feeder, and an antenna ground. The differential port, the connecting probe, the balun transmission line, the balun ground, and the antenna ground are all arranged on the dielectric plate. One end of the differential port is connected to the balun transmission line, and the other end is connected to the balun ground through the connecting probe. The connecting probe is arranged through the dielectric plate. The antenna feeder is arranged on the antenna ground and is connected to the balun transmission line. The antenna ground includes a first array element, a second array element, a third array element, and a fourth array element arranged side by side. The balun transmission line feeds power to the first array element, the second array element, the third array element, and the fourth array element through the antenna feeder.

[0009] Further, the antenna feeder includes a first T-shaped power divider, two second T-shaped power dividers, and four coupling lines. The two second T-shaped power dividers are symmetrically arranged at the two output ports of the first T-shaped power divider. The input port of each second T-shaped power divider is respectively connected to the corresponding output port of the first T-shaped power divider. A coupling line is arranged at the output port of each second T-shaped power divider. The input port of the first T-shaped power divider is connected to the balun transmission line.

[0010] Further, the input port of the first T-shaped power divider and / or the second T-shaped power divider has a transmission line width of 35 ohms, and its output port has a transmission line width of 50 ohms.

[0011] Further, the first array element and / or the second array element and / or the third array element and / or the fourth array element is a slot array antenna.

[0012] Further, the slot element in the slot array antenna is composed of a wide slot and a narrow slot that are connected up and down. The wide slot is located at the upper part of the slot element, and the narrow slot is located at the lower part of the slot element.

[0013] Further, the total length of the narrow slot and the wide slot is one-quarter of the wavelength in the medium at the center frequency of the antenna. The length of the wide slot is half of the length of the narrow slot. The coupling line is near the midpoint of the corresponding narrow slot.

[0014] Further, a director is correspondingly arranged above the wide slot of the slot array antenna.

[0015] Further, the length of the director is less than one-quarter of the wavelength in the medium at the center frequency of the antenna, and the perpendicular distance from the corresponding wide slot is one-eighth of the wavelength in the medium at the center frequency of the antenna.

[0016] Further, the balun transmission line has an exponentially tapered structure, with the narrow end having a 50-ohm impedance and the wide end having a 100-ohm impedance, and its length is greater than half of the wavelength in the dielectric at the lowest operating frequency band of the antenna;

[0017] and / or, the balun ground has an exponentially tapered structure, the width of the end connected to the connection probe is the same as that of the balun transmission line, and the width of the other end is 3 to 5 times that of the balun transmission line.

[0018] Further, the first element, the second element, the third element, and the fourth element have the same structure, and adjacent elements among the first element, the second element, the third element, and the fourth element are isolated by L-shaped slots.

[0019] The ultra-wideband radar differential antenna with directional radiation of the present invention includes a dielectric board, a differential port, a connection probe, a balun transmission line, a balun ground, an antenna feeder, and an antenna ground. The differential port, the connection probe, the balun transmission line, the balun ground, and the antenna ground are all arranged on the dielectric board. One end of the differential port is connected to the balun transmission line, and the other end is connected to the balun ground through the connection probe. The connection probe is arranged through the dielectric board. The antenna feeder is arranged on the antenna ground and is connected to the balun transmission line. The antenna ground includes a first element, a second element, a third element, and a fourth element arranged side by side. The balun transmission line feeds the first element, the second element, the third element, and the fourth element through the antenna feeder. Compared with the prior art, the present invention has the advantages of simple structure, lower sidelobe level and coupling between elements of the antenna, and higher gain in the end-fire direction of the antenna while broadening the spectral bandwidth of the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0021] Figure 1 is a schematic structural diagram of the ultra-wideband radar differential antenna with directional radiation according to an embodiment of the present invention;

[0022] Figure 2 is a top view of the ultra-wideband radar differential antenna with directional radiation according to an embodiment of the present invention;

[0023] Figure 3 is a schematic structural diagram of the antenna feeder of the present invention;

[0024] Figure 4 is a schematic structural diagram of the antenna ground, the L-shaped slot, and the director of the present invention;

[0025] Figure 5 is a top view of the differential port, the balun transmission line, and the balun ground of the present invention;

[0026] Figure 6 It is a schematic diagram of the differential port, balun transmission line, and balun ground of the present invention.

[0027] Explanation of reference numerals:

[0028] Differential port - 1 is connected to probe - 2

[0029] Balun transmission line - 3, balun ground - 4

[0030] Antenna feeder - 5, first T - shaped power divider - 51

[0031] Second T - shaped power divider - 52, coupling line - 53

[0032] Antenna ground - 6, narrow slit - 61

[0033] Wide slit - 62, wide slit - 63

[0034] Director - 7, dielectric plate - 8 Detailed implementation manners

[0035] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0036] In the present invention, orientations such as "upper", "lower", "front", "rear", etc. are all based on Figure 2 the view shown. The terms "first" and "second" are mainly used to distinguish different components, but do not specifically limit the components.

[0037] See Figures 1 - 6, the directionally radiating ultra-wideband radar differential antenna of this embodiment includes a dielectric plate 8, a differential port 1, a connecting probe 2, a balun transmission line 3, a balun ground 4, an antenna feeder 5 and an antenna ground 6. Among them, the differential port 1, the connecting probe 2, the balun transmission line 3, the balun ground 4 and the antenna ground 6 are all arranged on the dielectric plate 8. One end of the differential port 1 is connected to the balun transmission line 3, and the other end is connected to the balun ground 4 through the connecting probe 2. The connecting probe 2 is arranged through the dielectric plate 8. The antenna feeder 5 is arranged on the antenna ground 6 and is connected to the balun transmission line 3. Specifically, the antenna ground 6 includes a first element, a second element, a third element and a fourth element arranged side by side. The balun transmission line 3 feeds the first element, the second element, the third element and the fourth element through the antenna feeder 5. Preferably, the first element, the second element, the third element and the fourth element have the same structure and are all slot array antennas, and adjacent elements are isolated by an L-shaped slot 63. However, the present invention is not limited thereto. The above L-shaped slot 63 is formed by etching and has the effects of suppressing current, reducing the sidelobe level of the antenna and the coupling between elements, and its length is less than one-quarter of the wavelength in the medium. It should be noted that the dielectric plate 8 is a transparent plate, usually made of FR4 material, but not limited thereto, and it can also be made of any plate suitable for the conventional printed circuit board process.

[0038] See Figures 1 - 3 , the antenna feeder 5 includes a first T-shaped power divider 51, two second T-shaped power dividers 52 and four coupling lines 53. The two second T-shaped power dividers 52 are symmetrically arranged at the two output ports of the first T-shaped power divider 51. The input port of each second T-shaped power divider 52 is respectively connected to the corresponding output port of the first T-shaped power divider 51. A coupling line 53 is arranged at the output port of each second T-shaped power divider 52. The input port of the first T-shaped power divider 51 is connected to the balun transmission line 3. It should be noted that the input port of the first T-shaped power divider 51 and / or the second T-shaped power divider 52 has a transmission line width of 35 ohms, and its output port has a transmission line width of 50 ohms. It should be clear that there can be other more possibilities for the transmission line widths of the input ports and output ports of the first T-shaped power divider 51 and / or the second T-shaped power divider 52, and all can achieve the technical effects of the present invention.

[0039] Further, see Figure 4, the slot elements in the slot array antenna are composed of a wide slot 62 and a narrow slot 61 that are connected up and down to meet the bandwidth requirements of the ultra-wideband radar system. Specifically: the wide slot 62 is located at the upper part of the slot element, the narrow slot 61 is located at the lower part of the slot element, the total length of the narrow slot 61 and the wide slot 62 is one-quarter of the wavelength in the medium of the antenna center frequency, the length of the wide slot 62 is half of the length of the narrow slot 61, and the coupling line 53 is near the midpoint of the corresponding narrow slot 61. At the same time, among the four slot array antennas, a director 7 is correspondingly arranged above each wide slot 62 to improve the end-fire direction gain of the antenna. Preferably, the length of the director 7 is less than one-quarter of the wavelength in the medium of the antenna center frequency, and the perpendicular distance from the corresponding wide slot 62 is one-eighth of the wavelength in the medium of the antenna center frequency

[0040] To achieve good impedance matching, the length of the balun transmission line 3 is greater than half of the wavelength in the medium of the lowest operating frequency band of the antenna. The balun transmission line 3 is an exponentially tapered structure, with the narrow end having an impedance of 50 ohms and the wide end having an impedance of 100 ohms; at the same time, the balun ground 4 is also an exponentially tapered structure, and the width of the end connected to the connection probe 2 is the same as the width of the balun transmission line 3, and the width of the other end is 3 to 5 times the width of the balun transmission line 3

[0041] As a preferred embodiment of the present invention, the antenna ground 6 is composed of four antenna ground 6 modules spliced in sequence from left to right, and the first element, the second element, the third element, and the fourth element each correspond to one antenna ground 6 module. It should be noted that the antenna ground 6 can also be integrally formed, and the first element, the second element, the third element, and the fourth element are sequentially arranged from left to right on a whole piece of integrally formed antenna ground 6

[0042] In addition, it is worth mentioning that the differential port 1, the connection probe 2, the balun transmission line 3, the balun ground 4, the first T-shaped power divider 51, the second T-shaped power divider 52, the antenna ground 6, and the director 7 are all metal components, and generally are etched using conventional printed circuit board processes

[0043] In summary, the antenna of the present invention uses a four-element slot antenna array to achieve narrow-beam directional radiation in the horizontal direction. Specifically, the antenna is fed through the differential port 1 and undergoes impedance transformation from 100 ohms to 50 ohms through the balun transmission line 3 with an exponential taper structure. The 50-ohm port of the balun transmission line 3 uses two-stage "T-shaped" power division (the first T-shaped power divider 51 and the second T-shaped power divider 52) to achieve a one-to-four power division to feed four slot array antennas. The slot elements in the slot array antenna are composed of a wide slot 62 and a narrow slot 61 that are connected up and down. The wide slot 62 is located at the upper part of the slot element, and the narrow slot 61 is located at the lower part of the slot element. There is a director 7 above each wide slot 62 to enhance the end-fire direction gain of the antenna. An L-shaped slot 63 is etched between each element to suppress the current, reduce the side lobe level of the antenna, and the coupling between elements.

[0044] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A differential antenna for ultra-wideband radar with directional radiation, characterized in that, it includes a dielectric plate (8), a differential port (1), a connecting probe (2), a balun transmission line (3), a balun ground (4), an antenna feeder (5) and an antenna ground (6). The differential port (1), the connecting probe (2), the balun transmission line (3), the balun ground (4) and the antenna ground (6) are all arranged on the dielectric plate (8). One end of the differential port (1) is connected to the balun transmission line (3), and the other end is connected to the balun ground (4) through the connecting probe (2). The connecting probe (2) is arranged through the dielectric plate (8). The antenna feeder (5) is arranged on the antenna ground (6) and is connected to the balun transmission line (3). The antenna ground (6) includes a first array element, a second array element, a third array element and a fourth array element arranged side by side. The balun transmission line (3) feeds the first array element, the second array element, the third array element and the fourth array element through the antenna feeder (5). The first array element and / or the second array element and / or the third array element and / or the fourth array element is a slot array antenna. The slot elements in the slot array antenna are composed of a wide slot (62) and a narrow slot (61) that are connected up and down. The wide slot (62) is located in the upper part of the slot element, and the narrow slot (61) is located in the lower part of the slot element. A director (7) is correspondingly arranged above the wide slot (62) of the slot array antenna.

2. The differential antenna for ultra-wideband radar with directional radiation according to claim 1, characterized in that, the antenna feeder (5) includes a first T-shaped power divider (51), two second T-shaped power dividers (52) and four coupling lines (53). The two second T-shaped power dividers (52) are symmetrically arranged at the two output ports of the first T-shaped power divider (51). The input port of each second T-shaped power divider (52) is respectively connected to the corresponding output port of the first T-shaped power divider (51). A coupling line (53) is arranged at the output port of each second T-shaped power divider (52). The input port of the first T-shaped power divider (51) is connected to the balun transmission line (3). The input ports of the first T-shaped power divider (51) and / or the second T-shaped power dividers (52) have a transmission line width of 35 ohms, and their output ports have a transmission line width of 50 ohms.

3. The differential antenna for ultra-wideband radar with directional radiation according to claim 2, characterized in that, the total length of the narrow slot (61) and the wide slot (62) is one-quarter of the wavelength in the medium at the center frequency of the antenna. The length of the wide slot (62) is half of the length of the narrow slot (61). The coupling line (53) is near the midpoint of the corresponding narrow slot (61).

4. The differential antenna for ultra-wideband radar with directional radiation according to claim 1 or 3, characterized in that, the length of the director (7) is less than one-quarter of the wavelength in the medium at the center frequency of the antenna, and the perpendicular distance from the director to the corresponding wide slot (62) is one-eighth of the wavelength in the medium at the center frequency of the antenna.

5. The differentially-fed ultra-wideband radar antenna with directional radiation according to claim 1, characterized in that, the balun transmission line (3) is of an exponential tapered structure, with a narrow end having an impedance of 50 ohms and a wide end having an impedance of 100 ohms, and its length is greater than half of the wavelength in the medium at the lowest operating frequency band of the antenna; and / or, the balun ground (4) is of an exponential tapered structure, the width of the end connected to the connecting probe (2) is the same as that of the balun transmission line (3), and the width of the other end is 3 to 5 times the width of the balun transmission line (3).

6. The differentially-fed ultra-wideband radar antenna with directional radiation according to claim 1, characterized in that, the first element, the second element, the third element and the fourth element have the same structure, and adjacent elements among the first element, the second element, the third element and the fourth element are isolated by L-shaped slots (63).

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