CN206490172U - Super high frequency radio frequency recognizes antenna - Google Patents

Abstract

The utility model discloses an ultra-high frequency radio frequency identification antenna, which comprises a base plate, on which a lower base plate and an upper base plate are fixedly installed sequentially from bottom to top, and capacitive patches and radiation patches are respectively fixed on the upper and lower surfaces of the lower base plate. patch, the upper surface of the upper substrate is fixed with a parasitic patch, and a feeder line passes through the bottom plate and the lower substrate in sequence from bottom to top and connects with the capacitive patch. The capacitive patch, the radiation patch and the parasitic patch are respectively It is a rectangular structure with chamfered corners at opposite corners. The utility model uses a circularly polarized antenna and a microstrip structure. It is a circularly polarized antenna applied to an ultra-high frequency radio frequency identification system, which can cover the frequency range of 865-928MHz, and realizes the design goal of miniaturization and low loss. , through simulation and actual testing, the design requirements are met.

Description

UHF RFID Antenna

technical field

The utility model relates to the field of antennas, in particular to an ultra-high frequency radio frequency identification antenna.

Background technique

Radio frequency identification technology is also called radio frequency identification, which belongs to a kind of communication technology. It uses 1-100GHz microwave for short-distance identification communication, and uses radio signals to identify specific targets and read and write related data. There is no need to establish a mechanical system between the identification system and specific targets. Or optical contact, RFID technology has been widely used in the service industry, security applications and other fields.

The RFID system includes 3 basic parts: tags, readers and hosts. Tags provide object data, and readers collect information from tags and communicate with the system network. The radio frequency identification system mainly works in several frequency bands such as 125 kHz, 13.56 MHz, 433.92 MHz, 869MHz, 902-928 MHz, 2.45 GHz and 5.8 GHz.

The antenna is a key part in the radio frequency identification system, which enables the tag and the reader to exchange information directly, and the miniaturized and low-loss antenna is a growing trend.

At present, the existing radio frequency identification reader antennas have many different forms and structures, such as planar antennas, helical antennas, dipole antennas, etc. Most of them adopt linear polarization, which is prone to mismatching. The frequency range is not wide enough to fully meet the use of the ultra-high frequency range. In addition, miniaturized and low-loss antennas are a growing trend, and there is still room for improvement in existing antennas.

Microstrip antennas have been widely used due to their small size, light weight, low cost, and flexible feeding methods, but their narrow bandwidth limits their practical application.

Utility model content

The purpose of this utility model is to aim at the mismatching phenomenon easily caused by linear polarization in the prior art. The utility model provides an ultra-high frequency radio frequency identification antenna, which adopts circular polarization antenna and The circularly polarized antenna of the UHF RFID system can cover the frequency range of 865-928 MHz, and realize the design goal of miniaturization and low loss. Through simulation and actual test, the design requirements are met.

The technical scheme of the utility model is as follows:

An ultra-high frequency radio frequency identification antenna, including a base plate, is characterized in that: the base plate is fixedly installed with a lower base plate and an upper base plate sequentially from bottom to top, and the upper and lower surfaces of the lower base plate are respectively fixed with capacitive A patch and a radiation patch, the upper surface of the upper substrate is fixed with a parasitic patch, and a feeder line passes through the bottom plate and the lower substrate sequentially from bottom to top and is connected with the capacitive patch, the The capacitive patch, the radiation patch and the parasitic patch are rectangular structures respectively, and corners are cut at two opposite corners.

The UHF radio frequency identification antenna is characterized in that: the four corners of the lower base plate and the upper base plate are sequentially fixed on the base plate by pins respectively.

The UHF radio frequency identification antenna is characterized in that: the pins are respectively sleeved with supporting washers between the bottom plate and the lower base plate and between the lower base plate and the upper base plate.

The beneficial effects of the utility model:

1. The utility model is a microstrip antenna for a radio frequency identification system, which realizes single-point feeding circular polarization by cutting the corners of the rectangular patch;

2. The utility model adopts double-layer antenna and capacitive coupling feeding method to increase the bandwidth of the antenna, which can be applied to the ultra-high frequency field;

3. The radio frequency antenna of the present invention adopts FR4 plate, which has the characteristics of low manufacturing cost, simple and reliable structure, wide application range, strong adaptability, etc., and has a large bandwidth and good circular polarization characteristics, which can be widely used in the radio frequency identification system.

Description of drawings

Fig. 1 is a sectional view of the structure of the utility model.

Fig. 2 is a partial structure sectional view of the utility model.

Fig. 3 is a top view of the structure of the middle and lower substrate of the present invention.

Fig. 4 is a schematic structural diagram of the parasitic patch in the present invention.

Fig. 5 is a structural schematic diagram of the capacitive patch and the radiation patch of the present invention.

detailed description

Referring to the accompanying drawings, a UHF radio frequency identification antenna includes a base plate 1 on which a lower base plate 2 and an upper base plate 3 are fixedly installed sequentially from bottom to top, and the upper and lower surfaces of the lower base plate 1 are respectively fixed with capacitive The patch 5 and the radiation patch 6, the upper surface of the upper substrate 3 is fixed with a parasitic patch 4, and the feeder 7 passes through the bottom plate 1 and the lower substrate 2 sequentially from bottom to top and is connected with the capacitive patch 5, allowing The sexual patch 5 , the radiation patch 6 and the parasitic patch 4 are rectangular structures respectively, and corners are cut at two opposite corners.

In the utility model, the four corners of the lower base plate 2 and the upper base plate 3 are respectively fixed on the bottom plate 1 sequentially by pins 8 .

The pins 8 are respectively provided with supporting washers 9 between the base plate and the lower base plate 2 and between the lower base plate 2 and the upper base plate 3 .

Below in conjunction with accompanying drawing, the utility model is further described:

Referring to Figure 1-3, the size of the bottom plate 1 is 24×24mm, the size of the lower substrate 2 and the upper substrate 3 are both 20×20×1.5mm, and the FR4 board with a relative dielectric constant of 4.4 is selected as the dielectric substrate, and the lower substrate 2 The distance from the upper base plate 3 is adjusted and fixed at 1.55 mm by the height of the support washer 9 . The distance between the feed point of the feed line 7 and the center position of the lower substrate 2 is d = 4.45 mm.

There are two cut corners in the parasitic patch 4 , see Figure 4 for the size of the patch and the size of the cut corners.

There are two cut corners in the capacitive patch 5 and the radiation patch 6 , see FIG. 5 for the size of the patch and the size of the cut corners.

The structural dimensions of the antenna are determined by theoretical analysis and calculation of the antenna, simulated by the three-dimensional electromagnetic simulation software HFSS, and a set of ideal results obtained by continuously adjusting parameters.

The selection of dielectric substrate material is very important to the design of microstrip antenna, and has a great influence on the size and performance of the antenna. The thickness of the dielectric substrate affects the bandwidth, and a thicker substrate can increase the bandwidth. When the relative permittivity decreases, the binding of the dielectric substrate to the field decreases, the electromagnetic field radiation increases, and the bandwidth increases accordingly. However, this kind of board is generally expensive, and it is difficult to achieve high cost performance. The present invention uses cheap FR4 board as the dielectric substrate.

Circular polarization of the antenna: A circularly polarized wave is composed of two linearly polarized waves with equal amplitudes and a phase difference of ± 90°. The present invention uses a one-point feeding rectangular microstrip antenna to realize circular polarization. When the rectangular microstrip antenna adds a degenerate separation unit on the diagonal, the resonant frequency of the polarized orthogonal degenerate mode of the excitation is shifted. By continuously adjusting the size of the separation unit, the phase of one mode can be advanced by 45°, and the phase of the other mode can be behind by 45°, so that circularly polarized waves can be realized.

Bandwidth of the antenna: The microstrip antenna has limited its practical application due to its narrow bandwidth. In order to widen the bandwidth of the microstrip antenna and meet the target requirements, a double-layer antenna is used. The lower feeding layer antenna is the main patch, and a parasitic patch is added to the main patch. The main patch performs electromagnetic coupling on the parasitic patch. Feed, the resonant center frequencies of the two patch antennas are designed to be different, and the resonant bandwidths cross each other to broaden the overall bandwidth of the entire antenna. Of course, the introduction of this layer is mainly to expand the axial ratio bandwidth.

The quality factor Q of the microstrip antenna has a certain influence on the bandwidth, and it is necessary to reduce the Q value in order to obtain a larger bandwidth. After adopting the double-layer antenna, the thickness of the air dielectric substrate increases, the length of the coaxial feeding probe increases, and the inductance value of the probe increases accordingly. In order to reduce the inductance, the capacitive patch coupling feed is used to compensate, thereby reducing the Q value and increasing the bandwidth. The capacitor patch uses a rectangular thin copper sheet. By changing the side length of the patch to change the capacitance value of the patch, it can achieve a good match with the coaxial probe, thereby greatly widening the bandwidth of the antenna.

Antenna return loss and axial ratio simulation: The return loss and axial ratio simulation of the antenna shows that the S11 is less than -15 dB in the frequency range of 800-930MHz, which has a wide bandwidth and meets the design requirements. In the frequency range of 860 ~ 935MHz, the axial ratio of the antenna is less than 3 dB, which has good circular polarization characteristics. It can be seen from the gain diagram of the antenna that the antenna has the largest radiation in the direction of θ = 0°, and its maximum gain reaches 8.59 dBi, which shows that the antenna has good directivity and gain.

Claims (3)

1. An ultra-high frequency radio frequency identification antenna, comprising a base plate, is characterized in that: a lower base plate and an upper base plate are fixedly installed on the base plate from bottom to top successively, and the upper and lower surfaces of the lower base plate are respectively fixed with a capacitive patch and a radiation patch, the upper surface of the upper substrate is fixed with a parasitic patch, and a feeder line passes through the bottom plate and the lower substrate sequentially from bottom to top and is connected to the capacitive patch, The capacitive patch, the radiation patch and the parasitic patch are rectangular structures respectively, and corners are cut at two opposite corners. 2 . The UHF radio frequency identification antenna according to claim 1 , wherein the four corners of the lower substrate and the upper substrate are sequentially fixed on the bottom plate by pins. 3 . 3. The UHF radio frequency identification antenna according to claim 2, characterized in that: said pins are respectively sleeved with support washers between said base plate and lower base plate and between said lower base plate and upper base plate.