A broadband tuned microstrip antenna

Abstract

The invention discloses a wide-band tuned microstrip antenna, in which four outer microstrips loaded with varactors and PIN diodes are closely and symmetrically adjacent to a central microstrip loaded with the varactor to form a symmetrical bifurcated unidirectional current, and the equivalent electrical length of the symmetrical bifurcated unidirectional current is tuned by combining symmetrically distributed PIN diodes and varactor diodes to realize a wide-band tuned edge-radiating microstrip antenna, and the characteristics of stable directional pattern, fast tuning, small size and low profile are taken into account.

Description

Technical Field

[0001] The invention relates to a microwave communication device, in particular to a wide-band tuning microstrip antenna. Background Art

[0002] Frequency tunable microstrip antennas can achieve dynamic tuning of the operating frequency of microstrip antennas. Combined with the characteristics of simple structure, easy design and integration, microstrip antennas are widely used in wireless systems such as radar and communication. Broadband tuned microstrip antennas refer to microstrip antennas with a wide tuning frequency range, that is, a single antenna can achieve dynamic switching of different frequencies within a wide frequency band, thereby avoiding the assembly of multiple antennas on a single device, which is conducive to reducing system complexity, volume and cost, and improving spectrum utilization and compatibility of antenna working conditions.

[0003] At present, there are four main ways to realize frequency-tunable microstrip antennas. The first is to stack a rotatable metasurface structure on top of a square microstrip patch. Due to the change in relative dielectric constant during rotation, the antenna operating frequency can be tuned, but the frequency tuning range is narrow and the response speed of mechanical tuning is slow. The second is to load variable capacitance diodes on the two open branches between the square microstrip patch and the ground to change the frequency of the radiation zero points on both sides of the antenna operating frequency band to achieve a continuously tuned frequency-tunable microstrip antenna, but the frequency tuning range is still narrow, and the size is relatively large and the profile is high. The third is to embed a slot line loaded with a PIN tube on the metal ground of the microstrip patch, and control the working switching of the microstrip antenna and the slot antenna through a switch to achieve discrete frequency reconfiguration. The frequency tuning range has increased, but it is still limited, and there is a problem of poor front-to-back comparison. The fourth method is to load a variable capacitance tube or switch directly on the microstrip patch, or to connect the microstrip patch with a short patch, and realize continuous frequency tuning by controlling the variable capacitance or switch, but there are problems such as narrow frequency tuning range, unstable radiation pattern, large size and high profile. Therefore, it is necessary to propose a new type of wide-band tuned microstrip antenna that can take into account the characteristics of wide-band tuning, stable radiation pattern, fast tuning, small size and low profile. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned prior art, a wide-band tuned microstrip antenna is proposed, which can take into account continuous frequency tuning in a wide frequency range, stable radiation pattern, fast tuning, small size and low profile.

[0005] Technical solution: A wideband tuned microstrip antenna, comprising a central microstrip loaded with a varactor and four outer microstrips loaded with a varactor and a PIN diode; the four outer microstrips are centrally symmetrically distributed around the central microstrip and coupled through a portion parallel to the central microstrip; the central microstrip operates in TM 01mode, coupled with the four outer microstrips, to form a symmetrical bifurcated unidirectional current with adjustable equivalent electrical length.

[0006] Furthermore, the central microstrip includes a central metal strip with a length of 0.24-0.28λ0, two varactor diodes C v1 is embedded in the central metal strip, and the distance between the embedding point and the two ends of the central metal strip is 0.02~0.06λ0, where λ0 is the free space wavelength corresponding to the highest frequency.

[0007] Furthermore, the outer microstrip includes an outer metal strip with a length of 0.28~0.32λ0, and the parallel length of the outer metal strip and the central metal strip is 0.1~0.12λ0; a PIN diode is embedded in the outer metal strip near the central metal strip, and the distance between the embedding point and the end close to the outer metal strip is 0.09~0.13λ0; a varactor diode C v2 is embedded in a position of the outer metal strip away from the central metal strip, and the distance between the embedding point and the end close to the outer metal strip is 0.04~0.08λ0.

[0008] Furthermore, when the PIN diodes are both in the on state, the varactor diodes C v1 and varactor diode C When v2 is greater than or equal to 7 pF, the symmetrical bifurcated unidirectional current obtains the longest equivalent current under impedance matching conditions, corresponding to the lowest frequency sideways radiation of the overall antenna; and the equivalent electrical length of the symmetrical bifurcated unidirectional current increases with the change of the varactor diode. C v1 and varactor diode C The capacitance of v2 decreases and shortens, and the operating frequency of the corresponding overall antenna side radiation increases; when the PIN diodes are all turned off, the variable capacitance diode C v1 and varactor diode C When v2 is less than or equal to 0.1 pF, the symmetrical bifurcated unidirectional current obtains the shortest equivalent current under impedance matching conditions, corresponding to the highest frequency sideways radiation of the overall antenna.

[0009] Beneficial effects: The existing frequency tunable microstrip antenna cannot take into account wideband tuning, stable directional pattern, fast tuning, small size and low profile. The present invention closely and symmetrically adjoins the four outer microstrips loaded by the varactor and the central microstrip loaded by the varactor to form a symmetrical bifurcated unidirectional current, and combines the equivalent electrical length tuning of the symmetrically distributed PIN diodes and varactor diodes to achieve a wideband tuned edge-radiating microstrip antenna, and can take into account the characteristics of stable directional pattern, fast tuning, small size and low profile.

[0010] Specifically, the varactor-loaded central microstrip consists of two symmetrically distributed varactor diodes and a central microstrip, working in TM 01 mode, the distance between the varactor diode and the two ends is between 0.02 and 0.06λ0, and its operating frequency changes with the bias voltage of the varactor diode. When combined with the four outer microstrips loaded by the varactor and the PIN diode, a symmetrical bifurcated unidirectional current with adjustable equivalent current length is formed as a whole.

[0011] The four outer microstrips loaded with the varactor and PIN diode are symmetrically and closely distributed around the central microstrip loaded with the varactor, and the parallel length of the two is between 0.1~0.12λ0, the distance between the PIN diode loading position and the inner end is between 0.09~0.13λ0, and the distance between the varactor loading position and the outer end is between 0.04~0.08λ0. Through symmetrical distribution and linkage tuning of the PIN diode and the varactor diode, stable edge radiation with wide-band tuning is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The three-dimensional structure diagram of the antenna when no DC bias network is loaded;

[0013] Figure 2 This is a schematic diagram of the top structure of the antenna when the DC bias network is loaded;

[0014] Figure 3 is a matching simulation curve of the antenna according to an embodiment of the present invention;

[0015] Figure 4 is a gain simulation curve of the antenna according to an embodiment of the present invention;

[0016] Figure 5 The antenna of the embodiment of the present invention E Face to face H Surface simulation radiation pattern, where (a) corresponds to 2.76 GHz, (b) corresponds to 3.3 GHz, and (c) corresponds to 4 GHz. DETAILED DESCRIPTION

[0017] The present invention will be further explained below in conjunction with the accompanying drawings.

[0018] like Figure 1 As shown, a wide-band tuned microstrip antenna includes a top metal layer 1, a first substrate layer 2, a middle metal layer 3, a second substrate layer 4, and a bottom metal layer 5, which are arranged in sequence from top to bottom, and also includes varactor diodes 601~606, PIN diodes 701~704 and DC blocking capacitors 801~804.

[0019] like Figure 1 , Figure 2As shown, the top metal layer 1 includes a central metal strip 101, four outer metal strips 102, and DC bias branches 103 to 108. The length of the central metal strip 101 is between 0.24 and 0.28λ0, where λ0 is the free space wavelength corresponding to the highest frequency in the frequency tuning range. The varactor diodes 603 and 604 are symmetrically embedded in the central metal strip 101 by slotting, and the distance between the embedding point and the two ends is between 0.02 and 0.06λ0.

[0020] The four outer metal strips 102 are distributed in pairs at the upper and lower parts of both sides of the central metal strip 101. The arrangement direction of each outer metal strip 102 is consistent with that of the central metal strip 101, and they are centrally symmetrically distributed about the geometric center point of the central metal strip 101. The lengths of the four outer metal strips 102 are consistent, all between 0.28 and 0.32λ0, and the parallel lengths of each outer metal strip 102 and the central metal strip 101 are between 0.1 and 0.12λ0, and they are coupled through the narrow gap between the parallel parts. The four PIN diodes 701 to 704 are respectively embedded in the positions of each outer metal strip 102 close to the central metal strip 101, and the distance between the embedding point and the inner end of the outer metal strip 102 is between 0.09 and 0.13λ0. The four varactor diodes 601, 602, 605, and 606 are also correspondingly embedded in each outer metal strip 102, and the distance between the embedding point and the outer end of the outer metal strip 102 is between 0.04 and 0.08λ0. The DC blocking capacitors 801 to 804 are respectively embedded in the four outer metal strips 102 by slotting, and are located between each varactor diode and each PIN diode. A group of DC bias branches 103 to 106 are respectively connected to each outer metal strip 102, wherein the DC bias branches 103 and 104 are used to provide a DC bias circuit for the varactor diode on the outer metal strip 102; the DC bias branches 105 and 106 are used to provide a DC bias circuit for the PIN diode. Two ends of the central metal strip 101 are respectively connected to a DC bias branch 107 , and the middle of the central metal strip 101 is connected to a DC bias branch 108 . The DC bias branches 107 and 108 are used to provide a DC bias loop for the varactor diodes 603 and 604 .

[0021] There is a rectangular groove 301 in the center of the middle metal layer 3, the groove length is between 0.08 and 0.12λ0, and the rectangular groove is located directly below the central metal strip 101. The bottom metal layer 5 is a feeding metal structure composed of a metal strip line 501, the length of which is between 0.4 and 0.44λ0, and is located directly below the rectangular groove 301.

[0022] In the above structure, the metal strip line 501, the second substrate layer 4, and the middle metal layer 3 form a microstrip feed line. The central metal strip 101, the varactor diodes 603, 604, the first substrate layer 2, and the middle metal layer 3 form a central microstrip loaded with a varactor. The four outer metal strips 102, the varactor diodes 601 / 602 / 605 / 606, the PIN diodes 701 / 702 / 703 / 704, the first substrate layer 2, and the middle metal layer 3 respectively form four outer microstrips loaded with varactors and PIN diodes.

[0023] For the antenna of the above structure, the signal is fed from the port to the microstrip feeder, and then coupled to the central microstrip loaded with the varactor through the rectangular slot 301, and then coupled to the four outer microstrips loaded with the varactor and PIN diode tube. Under the action of the overall structure including the DC bias branch and the DC blocking capacitor, a wide-band tuned microstrip antenna is formed. In this process, the central microstrip loaded with the varactor works in TM 01 The mode, when closely combined with the four outer microstrips loaded by the varactor and PIN diode, forms a symmetrical bifurcated unidirectional current. The varactor diodes 603 and 604 are marked as C v1, varactors 601-602, 605-606 are marked as C v2, PIN diodes 701~704 are marked as PIN. When the PIN diode is in the on state, the varactor diode C v1 and C When v2 is greater than or equal to 7 pF, the symmetrical bifurcated unidirectional current obtains the longest equivalent current under impedance matching conditions, corresponding to the lowest frequency sideways radiation of the overall antenna. Then, the equivalent electrical length of the symmetrical bifurcated unidirectional current increases with the varactor diode. C v1 and C The capacitance of v2 is reduced and shortened, and the operating frequency of the corresponding overall antenna side radiation increases. On this basis, the PIN diode is further turned off, and the varactor diode C v1 and C When v2 is less than or equal to 0.1 pF, the symmetrical bifurcated unidirectional current obtains the shortest equivalent current under impedance matching conditions, corresponding to the highest frequency side radiation of the overall antenna. Combining the above-mentioned coupled microstrip combination, PIN diode and varactor combination, continuous frequency reconfiguration in a large frequency range can be achieved, and the stability of the directional pattern, fast tuning, small size and low profile can be taken into account.

[0024] Compared with the best existing technology, the frequency-tuned microstrip antenna proposed in the present invention not only achieves wide-range frequency tuning, but also takes into account the characteristics of stable radiation pattern, fast tuning, small size and low profile. In this embodiment, the capacitance value of the varactor diodes 601-606 varies from 7 pF to 0.1 pF. The simulated matching response and gain response are shown in Figure 2. Figure 3 , Figure 4 As shown, continuous frequency tuning can be achieved in the frequency range of 2.76~4 GHz, that is, the relative tunable range can reach 44.9%. In this frequency tuning range, the gain of the antenna is between 1.5~3.9 dBi. Figure 5 The embodiment is shown in Figure 2 at 2.76 GHz, 3.3 GHz and 4 GHz. E Face to face H The simulated radiation pattern shows that the side radiation can be kept stable within this frequency range. E The half-power beamwidth is between 71° and 83.6°. E The half-power beam width is between 78.2° and 89.5°. E Face to face H The cross-polarization level of the antenna is low. The substrate used in this case is Rogers RO4003C, and the overall size of the antenna is only 0.65λ0*0.12λ0*0.017λ0.

[0025] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A broadband tuned microstrip antenna, characterized in that: It comprises a top metal layer (1), a first substrate layer (2), a middle metal layer (3), a second substrate layer (4), and a bottom metal layer (5) which are arranged in sequence from top to bottom; The top metal layer (1) comprises a central metal strip (101) loaded with a varactor, and four outer metal strips (102) loaded with a varactor and a PIN diode; the four outer metal strips (102) are centrally symmetrically distributed around the central metal strip (101), and are coupled via a portion parallel to the central metal strip (101); Each outer metal strip (102) is respectively connected to a group of DC bias branches, which are used to provide a DC bias loop for the varactor diode on the outer metal strip (102), and to provide a DC bias loop for the PIN diode on the outer metal strip (102); two ends of the central metal strip (101) are respectively connected to a DC bias branch, and the middle of the central metal strip (101) is connected to a DC bias branch, which is used to provide a DC bias loop for the varactor diode on the central metal strip (101); A rectangular groove (301) is present at the center of the middle metal layer (3), and the rectangular groove is located directly below the central metal strip (101); the bottom metal layer (5) is a feeding metal structure composed of metal strip lines (501), and is located directly below the rectangular groove (301); The metal strip line (501) and the second substrate layer (4) and the middle metal layer (3) form a microstrip feed line; the central metal strip (101) loaded with the varactor, the first substrate layer (2) and the middle metal layer (3) form a central microstrip loaded with the varactor; the four outer metal strips (102) loaded with the varactor and the PIN diode, the first substrate layer (2) and the middle metal layer (3) respectively form four outer microstrips loaded with the varactor and the PIN diode; The signal is fed from the port to the microstrip feed line, and then coupled to the central microstrip loaded with the varactor through the rectangular slot (301), and then coupled to the four outer microstrips loaded with the varactor and the PIN diode tube. Under the action of the overall structure including the DC bias branch and the DC blocking capacitor, a wide-band tuned microstrip antenna is formed; the central microstrip works in TM 01 mode, coupled with the four outer microstrips, to form a symmetrical bifurcated unidirectional current with adjustable equivalent electrical length.

2. The broadband tuned microstrip antenna according to claim 1, characterized in that: The central microstrip includes a central metal strip with a length of 0.24~0.28λ0, two varactor diodes C v1 is embedded in the central metal strip, and the distance between the embedding point and the two ends of the central metal strip is 0.02~0.06λ0, where λ0 is the free space wavelength corresponding to the highest frequency.

3. The broadband tuned microstrip antenna according to claim 2, characterized in that: The outer microstrip includes an outer metal strip with a length of 0.28~0.32λ0, and the parallel length of the outer metal strip and the central metal strip is 0.1~0.12λ0; a PIN diode is embedded in the outer metal strip near the central metal strip, and the distance between the embedding point and the end close to the outer metal strip is 0.09~0.13λ0; a varactor diode C v2 is embedded in a position of the outer metal strip away from the central metal strip, and the distance between the embedding point and the end close to the outer metal strip is 0.04~0.08λ0.

4. The broadband tuned microstrip antenna according to claim 3, characterized in that: When the PIN diodes are in the on state, the varactor diode C v1 and varactor diode C When v2 is greater than or equal to 7 pF, the symmetrical bifurcated unidirectional current obtains the longest equivalent current under impedance matching conditions, corresponding to the lowest frequency sideways radiation of the overall antenna; and the equivalent electrical length of the symmetrical bifurcated unidirectional current increases with the change of the varactor diode. C v1 and varactor diode C The capacitance of v2 decreases and shortens, and the operating frequency of the corresponding overall antenna side radiation increases; when the PIN diodes are all turned off, the variable capacitance diode C v1 and varactor diode C When v2 is less than or equal to 0.1 pF, the symmetrical bifurcated unidirectional current obtains the shortest equivalent current under impedance matching conditions, corresponding to the highest frequency sideways radiation of the overall antenna.

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