Research On A Low Profile And Wideband Phased Array Antenna

The conventional array antennas can only radiate directional beam. With the introduction of some phase shifters in the feeding network, the array antennas can realize the spatial scanning of the radiation beam. Such array antennas are called phased array antenna. Phased array technology has been applied in radar, radio astronomy, weather forecasting, air traffic control, radio broadcasting, mobile wireless communication and other fields. In particular, with the development of 4G and the research of 5G, phased array technology in wireless communication field would have more employments.Nowadays, phased array antennas are often required to have a low profile and a wide band. Therefore, with the requirement of miniaturization and broadband, new research and design methods should be proposed.In this paper, a low profile with broadband phased array antenna is designed, which mainly includes:1. A novel planar single arm spiral antenna with low profile is designed. With a metal disc back loaded in the spiral arm, the input impedance of the antenna is regulated. When the height of the novel antenna is reduced to 0.119?₀, the antenna can obtain good performances over a wideband. The measured results show that the VSWR of the antenna is less than 1.45 with a relative bandwidth of 11%. The boresight gain is better than 7 d Bic over the working frequency band, which meet the requirements of the antenna element.2. A array antenna composed of twenty-four novel single arm spiral antennas is designed. The structure of the designed array antenna is streamlined, which can reduce the motion carrier. With the twenty-four holes in the reflector plate of the array antenna, the external conductors of the coaxial lines of all the antenna elements are separated from each other. So the current loop among the antenna elements, the reflector plate and the coaxial lines is removed, and then the mutual coupling between the elements is reduced. The simulated results of the beam scanning of the array antenna show that the boresight gain at the high and the low frequency are 19.3 d Bic and 18.8 d Bic, respectively. And the corresponding axial ratio is less than 3 d B. In the beam scanning angle domains?0°???360°,??65°?,the gain of the array antenna is better than 11.5d Bic.3 A compact microstrip power divider is designed to feed the twenty-four antenna elements. The structure of the power divider is very compact by using a ring power divider with a space rotation structure. At the same time, with the introduction of the microstrip line, the power divider can obtain a very low profile. The measured results show that the designed compact microstrip power divider obtains good transmission performances. Over the working frequency band, the reflection coefficient is lower than-22 d B. The transmission loss of the twenty-four branches at the high and the low frequency are less than 0.5 d B and 0.3 d B, respectively. The difference of the amplitude and the phase of the twenty-four output ports are 0.4 d B and 4 degree, respectively. And the isolation between any two output ports is better than 20 d B.4. The designed streamlined array antenna, compact microstrip power divider and the selected phase shifters are assembed and measured. The measured results show that the VSWR of the designed phased array antenna is lower than 1.6 with a relative bandwidth of 11%. The boresight gain at the high and the low frequency are 17.3 d Bic and17 d Bic, respectively. In the beam scanning angle domains?0°???360°,??65°?, the gain of the phased array antenna is better than 9 d Bic.