Millimeter Wave Antenna Array Using Artificial Magnetic Conductor Structures Based On LTCC Technology

With the rapid development of modern wireless communication systems,millimeterwave antennas play an important role as the transmitting and receiving front end in the signal transmission chain.As communication frequencies continue to increase,antenna sizes are shrinking,allowing antennas to be integrated directly into chip packaging,providing millimeter-wave systems with low interconnection loss and high integration advantages.However,as the operating frequency of packaged antennas increases,the planar dimensions of the interconnection chips decrease,creating thermal pressure on high-power chips.Therefore,non-uniform antenna arrays with large inter-element spacing have become a solution for high-frequency packaged antenna arrays.The main research work of this paper can be summarized as follows:(1)Low-Temperature Co-Fired Ceramic technology,with its multilayer structure,has become a common processing method for high-integration packaged antennas.However,using ceramic materials with high relative permittivity as antenna substrate will lead to reduced operating bandwidth and decreased gain.To improve the performance of LTCC-based packaged antennas,this paper proposes the addition of an artificial magnetic conductor below the microstrip patch antenna to adjust the antenna’s input impedance,achieving good impedance matching over a wide frequency band.Simulation results show that the packaged antenna has a wide bandwidth in 66.90GHz-81.74 GHz and high gain,with the maximum normalized gain of 8.03 d Bi within the frequency range.(2)Sparse antenna arrays,as one form of non-uniform antenna arrays,reduce the number of elements and processing costs while achieving high-performance array synthesis.This paper proposes a dual-loop algorithm for low side-lobe array synthesis.Firstly,the generation rule for initial excitations is improved to increase the probability of setting the middle part of the excitation vector to 1 and the probability of setting the edge part to 0.Secondly,each initial excitation amplitude value undergoes multiple inner loop calculations,accumulating changes in the excitation amplitude to avoid premature convergence of the algorithm.Instead of using the sidelobe level corresponding to the excitation amplitudes before setting them to 0 or 1 as the fitness function,the sidelobe level corresponding to the excitation amplitudes after setting them to 0 or 1 is used to prevent result errors caused by forcibly changing the excitation amplitudes.These improvements give the proposed dual-loop algorithm good optimization capability and stability.(3)Regarding the difficulty of accurately and stably identifying the main lobe of a planar antenna array,this paper proposes a two-dimensional main lobe identification algorithm.The commonly used main lobe identification algorithms include linear search,power difference,and power descending methods.However,these methods are limited by the sampling method of the radiation pattern data and have poor sensitivity in identifying main lobe boundaries outside the vertical and horizontal directions.Based on the definition of the main lobe and sidelobe ranges,this paper uses the enclosed minimum value curve in the radiation pattern data that surrounds the main lobe as the main lobe boundary and applies a seed algorithm to fill it,enhancing the sensitivity of main lobe boundary identification in non-vertical and non-horizontal directions.This allows the proposed minimum value main lobe identification algorithm to be applicable to the identification of two-dimensional main lobes with complex planar projection shapes.