CN104143689A - Tri-Band Antenna for Bluetooth/RFID/WLAN/WiMAX - Google Patents

Abstract

The invention belongs to the technical field of microstrip antennas. In order to increase the bandwidth of the antenna and realize the multi-band design of the antenna, the technical solution adopted by the invention is that the tri-band antenna for Bluetooth/RFID/WLAN/WiMAX includes a grounding plate and a feed point , a radiation patch and a dielectric substrate, the radiation patch is composed of four pairwise symmetrical semicircular rings, a circular ring and two rectangular strips, and the circular ring is located in the middle of the area surrounded by the four semicircular rings. , the width of the strip line connecting the four semi-circular rings and the inner circular ring is narrower than the strip line from the feed point to the four semi-circular rings; the dielectric substrate is epoxy board FR4; An arched structure is arranged on the ground plate below the strip line, and a circular defect is arranged in the middle of the arched structure. The invention is mainly applied to the design and manufacture of the microstrip antenna.

Description

Tri-Band Antenna for Bluetooth/RFID/WLAN/WiMAX

technical field

The invention belongs to the technical field of microstrip antennas, in particular to a tri-band antenna for Bluetooth/RFID/WLAN/WiMAX.

technical background

Defected Ground Structure (DGS: Defected Ground Structure) is one of the latest developments in the microwave field. It is developed from the photonic bandgap structure (PBG). This structure changes the distribution of ground current by etching periodic or non-periodic patterns on the ground plane of transmission lines such as microstrip lines, thereby changing the frequency characteristics of transmission lines, suppressing harmonics, and increasing bandwidth. Defective ground structures are widely used in microwave circuit and antenna design. There have been many achievements at home and abroad on the research on the fact that the defect grounding structure can realize multiple frequency bands.

With the rapid development of wireless mobile communication systems towards miniaturization, multi-function and intelligence, antennas are also facing new requirements, namely miniaturization, multi-band, wide-band, etc. In recent years, there have been some single-frequency antennas suitable for different communication standards, but there are relatively few antenna designs suitable for Bluetooth, RFID, WLAN and WiMAX.

Contents of the invention

In order to overcome the deficiencies in the prior art, in order to increase the bandwidth of the antenna and realize the multi-band design of the antenna, the technical solution adopted by the present invention is that the tri-band antenna for Bluetooth/RFID/WLAN/WiMAX includes a grounding plate, a feed point, The radiation patch and the dielectric substrate, the radiation patch is composed of four pairwise symmetrical semicircular rings, a circular ring and two rectangular strips, the circular ring is located in the lower part of the area surrounded by the four semicircular rings, The width of the strip line connecting the four semi-circular rings and the inner circular ring is narrower than the strip line from the feed point to the four semi-circular rings; the dielectric substrate is epoxy board FR4; the strip line from the feed point to the four semi-circular rings An arched structure is arranged on the ground plate below the line, and a circular defect is arranged in the middle of the arched structure.

The width of the strip line connecting the four semicircular rings and the inner circular ring is 2 mm, the radius of the arched structure is 10 mm, and the radius of the circular defect is 1.9 mm.

The inner and outer radii of the four semicircles and the inner circle are: R1=8.5mm, R2=7.5mm, R3=4mm, R4=3mm, R5=4mm, R6=3mm; the four semicircles and the inner circle The length of the stripline connected by the ring is L1=5.5mm, the width is W1=2.0mm, the length and width of the stripline from the feeding point to the four semi-circular rings are Lf=13mm, Wf=2.6mm respectively, and the size of the rectangular grounding plate It is 6mm x 25.0mm.

Compared with prior art, technical characteristic and effect of the present invention:

The defective ground structure increases the bandwidth of the antenna, realizes multi-band design, has good matching characteristics, and the pattern characteristics of the antenna are relatively stable in all working frequency bands, and has good directivity.

Description of drawings

Figure 1. Block diagram of a tri-band antenna.

Figure 2. Antenna design process and the corresponding return loss characteristics of each antenna.

(a) Antenna design process; (b) S11 curves corresponding to three antennas.

Figure 3. Directional diagrams of the antenna on the E plane and the H plane at 2.45GHz, 3.5GHz, and 5.5GHz, respectively.

Detailed ways

The present invention designs a tri-frequency monopole antenna that can be used for Bluetooth/RFID/WLAN/WiMAX simultaneously by introducing a defective structure.

The antenna consists of a ground plane, a feed point, a radiating patch, and a dielectric substrate. The radiation patch is composed of four pairwise symmetrical semicircular rings, a circular ring and two rectangular strips; the dielectric substrate is epoxy board FR4, the relative permittivity εr = 4.4, and the dielectric loss is 0.02; the feed The method is microstrip line feeding, and the characteristic impedance is 50Ω;. The structural diagram of the antenna is shown in Figure 1.

The original design of the antenna is derived from antenna I, which only includes a flower-shaped radiation patch and a floor spliced by two identical four semi-circular rings, as shown in Figure 2(a), the radiation unit passes through the SMA connector After feeding, the current flows from the feeding point through the strip line to the top of the large semi-circular ring on the upper part of the radiation patch. The path length of the current flowing through is 52.25mm (about 0.42λ). At this time, the antenna only works in one frequency band and can only Basically cover the Bluetooth working frequency band.

Antenna II can excite another resonant frequency by adding a circular patch inside the four semi-circular rings, and the surface area of the antenna does not change. In order to obtain better matching characteristics, by calculation and comparison, the width of the strip line connecting the four semi-circular rings and the inner circular ring is 2 mm, which is narrower than the strip line connecting the feed point to the four semi-circular rings. At this time, the current flows from the feeding point through the strip line to the top of the inner ring. The path length of the current flowing is 31.06mm (about 0.34λ), which can still cover the Bluetooth working frequency band, and at the same time generate a second frequency band close to the WiMAX working frequency band. band. When the size of the antenna does not change, the first resonant frequency moves to the left, which is equivalent to reducing the size of the antenna.

In order to obtain the third working frequency band and improve the second working frequency band obtained above, an arched ground structure with a circular defect is adopted above the rectangular floor, the defect radius R8=1.9mm, and the size and position of the circular defect are in To a certain extent, it affects the resonant frequency and impedance bandwidth of the antenna. By etching a circular defect at a suitable position of the arched ground structure, the simulation found that the antenna has a third frequency band with a wider bandwidth and better matching, because the defect ground structure can filter out undesired frequencies. At this time, the current flows from the feed point through the strip line to the bottom of the lower semi-circular ring. The path length of the current flow is 18.5mm (about 0.33λ). Due to the defective ground structure, the frequency characteristic here is changed, thus obtaining the third frequency band. Finally, an antenna covering Bluetooth, WLAN and WiMAX operating frequency bands is obtained without increasing the overall volume.

The high-frequency simulation software HFSS is used to simulate and optimize the design of the antenna to obtain the best relationship between size and tuning.

The return loss is shown in Figure 2(b). It can be seen that the antenna I only works in a frequency band of 2.31-2.61GHz, and the resonance frequency is 2.44GHz. The impedance bandwidths of the antenna II are 2.27-2.48GHz and 3.18-3.39GHz respectively, and the center frequencies are 2.38GHz and 3.26GHz respectively. Antenna III provides three impedance bandwidths of 0.16GHz, 0.35GHz and 1.56GHz, the working frequency bands are 2.38-2.54GHz, 3.3-3.65GHZ and 4.85-6.41GHz respectively, and the center frequencies are 2.47GHz, 3.42GHz and 5.31GHz respectively. The return loss of the antenna at the resonant point is -19.1dB, -20.5dB and -21.1dB respectively, showing good matching characteristics of the antenna. Figure 3 is the radiation pattern of the antenna on the E(xoz) plane and H(yoz) plane at 2.45GHz, 3.5GHz and 5.5GHz, respectively. The antenna’s pattern characteristics are relatively stable in all operating frequency bands and have good directivity . To sum up, the defective ground structure increases the bandwidth of the antenna and realizes the multi-band design.

The present invention will be further described in detail below in conjunction with a specific embodiment.

The feeding method is microstrip line feeding, and the characteristic impedance is 50Ω

The size of the dielectric substrate is 38mm×25mm, and the height is 0.8mm. Figure 1 is a structural dimension diagram of a tri-band antenna (front and back). After HFSS optimization, the length of the rectangular connecting strip is L1=5.5mm, the width is W1=2.0mm, the length and width of the microstrip line are Lf=13mm, Wf=2.6mm, and the size of the rectangular floor is 6mm×25.0mm , wherein the arc radius R7=10mm, the defect radius R8=1.9mm, the radiation unit R1=8.5mm, R2=7.5mm, R3=4mm, R4=3mm, R5=4mm, R6=3mm.

Claims (3)

1. A tri-band antenna for bluetooth/RFID/WLAN/WiMAX is characterized in that it comprises a grounding plate, a feed point, a radiation patch and a dielectric substrate, and the radiation patch is composed of four pairs of symmetrical, sequentially connected It consists of a semi-circle, a circular ring and two rectangular strips. The circular ring is located in the lower part of the area surrounded by the four semi-circular rings. The striplines of the four semicircular rings should be narrow; the dielectric substrate is epoxy board FR4; there is an arched structure on the ground plate below the striplines from the feed point to the four semicircular rings, and a circular arc structure is arranged in the middle of the arched structure. defect. 2. the tri-band antenna for bluetooth/RFID/WLAN/WiMAX as claimed in claim 1, is characterized in that, the band line width that four semicircular rings and inner circular ring are connected is 2mm, arched structure radius 10mm, The radius of the circular defect is 1.9mm. 3. the tri-band antenna for bluetooth/RFID/WLAN/WiMAX as claimed in claim 1, is characterized in that, inside and outside radius of four semicircular rings and inner circular ring are respectively: R1=8.5mm, R2= 7.5mm, R3＝4mm, R4＝3mm, R5＝4mm, R6＝3mm; the length of the strip line connecting the four semicircular rings and the inner circular ring is L1＝5.5mm, the width is W1＝2.0mm, and the feeding point is The stripline length and width of the four semicircular rings are Lf=13mm, Wf=2.6mm respectively, and the size of the rectangular ground plate is 6mm×25.0mm.