| With the continuous development of wireless communication technology,wireless communication system equipment has higher and higher requirements for antenna performance,and the requirement of multi-function,miniaturization,integration and high isolation of miniaturized vehicle-mounted multi-functional combined antenna is increasingly stringent.As an important transceiver in information system,the performance of antenna determines the quality of the whole wireless communication.In modern communication systems,omnidirectional radiation,large-capacity,multi-band MIMO and other antennas are increasingly favored by the society.Antennas not only need to meet the requirements of miniaturization and high performance,but also meet the requirements of high isolation and good stability.With the continuous advancement of communication technology,people's requirements for car performance are getting higher and higher.Among them,the miniaturized vehicle-mounted multifunctional combined antenna that plays the role of communication transceiver has aroused the research interest of researchers.The miniaturized vehicle-mounted multifunctional combined antenna installed in the car mainly includes radio antenna,mobile phone communication antenna,Bluetooth and WIFI antenna,GPS antenna,car networking antenna,etc.The most important part is 460 MHz omnidirectional radiation radio antenna,MIMO multi-band communication antenna,Bluetooth and WIFI dual band antenna.This article designs three miniaturized omni-radiation radio antennas that can be used in vehicle-mounted wireless communication systems and mobile communication terminal equipment.The antenna radiates omnidirectionally in the horizontal direction.The operating frequency is 460 MHz and the profile height requirements are less than 0.076 times of vacuum wavelengths.At the same time,the maximum gain is not less than 0dBi,the antenna structure must be easy to integrate with other communication equipment,and it must have good drop resistance.According to the design requirements,three new 460 MHz miniaturized omnidirectional radio antennas are proposed:(1)Normal mode helical antenna based on capacitive coupling feed: The helical antenna are reasonably designed to make it work in the normal mode in this paper,and the miniaturization design of the antenna is carried out by using the coupling feed capacitor and parallel plate capacitor loading technology.The optimized height size of the antenna is 0.064 times of vacuum wavelength,maintaining the high gain and high radiation efficiency of the antenna.The maximum gain of the horizontal omnidirectional radiation is about 2dBi;(2)Improved pyramid helical antenna based on capacitive coupling feed: In order to further reduce the profile height of the antenna and ensure the high-efficiency omnidirectional radiation in the horizontal direction of the antenna,this paper innovatively proposes a pyramid helical antenna based on capacitive coupling feed.The profile height of the antenna is only 0.018 times of the vacuum wavelength,and the maximum gain of omnidirectional radiation is about 1.39 dBi;(3)Miniaturized low-profile radial antenna based on capacitive coupling feed: Radial antennas have the characteristics of omnidirectional radiation and simple structure.This article innovatively introduces coupling feed capacitors and loading capacitors to realize the miniaturization design of 460 MHz radial antennas.The feasibility of the design method is verified by theoretical calculation,equivalent circuit analysis,simulation analysis and physical test.The section height of the antenna is only about 10 mm,the maximum gain is about 1.5dBi,and it is extremely resistant to drop and is easy to integrate into the complete communication system.The measured results show that the innovative antenna can meet the design requirements of the society and can be used in mass production.The MIMO multi-band vehicle-mounted communication antenna designed in this article covers most of the mobile phone communication frequency bands.The specific frequency bands include GSM850,GSM900,DCS,PCS,UMTS,LTE,5G communication sub-6GHz band,and the specific working frequency band is 824-960 MHz,1710-2170 MHz,2300-2690 MHz,3300-5000 MHz,and this MIMO multi-band communication antenna meets the requirements of miniaturization and isolation at the same time;the specific working bands of the Bluetooth and WIFI dual band antenna are 2.4-2.483 GHz and 5.725-5.850 GHz,it meets the requirements of low cost and high radiation performance.This article mainly proposes two innovative antenna structures for miniaturized vehicular communication antennas:(1)MIMO multi-band vehicle-mounted antenna: The antenna adopts a printed monopole antenna structure and introduces multiple slots to achieve multi-mode resonance.The antenna height is about 51.5mm.The simulated results show that the VSWR of the antenna is less than 4dB in 800-960 MHz band,3dB in 1500-5000 MHz band,and the maximum gain is not less than 5dBi,which meets the design requirements.Then,the MIMO communication antenna is designed,and its isolation is improved by slotting on the floor to meet the requirements.Finally,the MIMO communication antenna is processed and tested.The measured results show that the VSWR of the MIMO communication antenna is less than3 dB in 824-5000 MHz band,the maximum gain of the antenna is not less than 5dBi,the isolation of 824-960 MHz band is less than-6dB,and the isolation of 1710-5000 MHz band is less than-10 dB;(2)Bluetooth and WIFI dual band antenna: The printed monopole antenna structure is adopted,slotted and windowed on the floor.At the same time,the microstrip branch is introduced to adjust the position of resonant frequency points to form a dual-mode resonant state,which meets the requirements of 2.4GHz and 5.8GHz dual band operation of the antenna.The simulated results show that the VSWR of Bluetooth and WIFI dual band antenna in both bands is less than 3dB,the maximum gain is more than 3.5dBi,and the antenna size is small.It has high stability and meets the design requirements.It can give full play to the outstanding advantages of Bluetooth and WIFI short-range high-quality connection in the compact vehicle-mounted multifunctional combined antenna.In this paper,a variety of solutions are proposed for the miniaturized multifunctional combined antenna.Through the theoretical calculation,equivalent circuit analysis,simulation analysis and processing test,the feasibility of the scheme is verified,which provides a new design method and idea for 460 MHz omnidirectional radiation radio antenna,MIMO multi band communication antenna andBluetooth WIFI dual band antenna. |
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