Phased Array Design Based On Negative Group Delay Network

Due to a tremendous growth in demand for the phased array radar,the phased array antenna with wideband and wide beam scanning range catches the attention of researchers.However,beam deviation appears to be significantly serious when antenna arrays operate in a wide band.To alleviate above limitation,this paper presents a design of real-time delay line with low delay,based on the advanced phase characteristic of the negative group delay network.The investigations are addressed as follows:1.Based on the principle of series-fed linear phased array,the aperture effect of the beam scanning array for wideband operation and corresponding solutions are studied.After simulation and analysis,the relationship between the delay of array element and the antenna beam direction is demonstrated,correcting the misunderstanding of delay phased array existing in some papers.And the real-time delay line based on the negative group delay is investigated,along with the index distribution and key technologies of the proposed delay phased array.2.Based on the negative group delay network of lumped structure,the real-time delay line with the gain of 3dB and the delay of 0ns is designed,covering the 1-1.5GHz frequency band.After the improvement of design method,the real-time delay line covering 2.6-4GHz is proposed based on the distribution structure,obtaining the gain of 0dB and the delay of 0.06 ns.The advanced design achieves less elements with flatter gain and delay.3.A switch-line delay phase shifter suitable for delay scanning phased array is proposed with RF switch ships and slow-wave lines.Compared to the meander line,the slow-wave line shows the advantages of low loss and compact size.A miniaturized tapered slot antenna is proposed by adopting elliptically radiating slot,with 50% shorter size than that of traditional structure.Periodic slots are loaded to improve the radiation characteristics at low frequency.The performance of 4-elements array is analyzed when wideband and wide beam scanning.4.The phased array with above modules is built and tested.The test result indicates that the phased array based on negative group delay network can realize squint-free beamforming in a wideband of 2.6-4GHz,which greatly eliminating the aperture effect.Arbitrary-angle beamforming in the range of-60°~60° can be achieved theoretically by adjusting the delay difference between ports with delay phased shifters.