Research On The Key Technologies Of I-Q Vector Modulators

With the development of technology,the frequency used by modern microwave and millimeter-wave systems is getting higher and higher,the traditional intermediate frequency modulation technology is no longer applicable.Due to its ability to directly modulate RF signals,vector modulator(VM)is widely used in microwave and millimeter-wave systems such as space communication,RF cancellation,and phased array radar.I-Q vector modulator has become the most popular vector modulator because of its advantages including simple structure,high modulation accuracy and adjustable amplitude phase within 360°.In order to deeply study the key technologies of I-Q vector modulators,this topic starts with the principle of I-Q vector modulators,gives an overall analysis adout the main factors that affect the performance of vector modulators by simulation software,and then comprehensively compares the characteristics and differences between the two I-Q vector modulators structures.Based on this,two I-Q vector modulator MMICs b GaAs process are designed.One of them uses HiWafer PPA25 process,working in 26.5~40GHz,using a balanced structure.Firstly,the optimization scheme of pHEMT gate width was introduced.Then the differences between two biphasic amplitude modulators were verified and compared.After that,the overall layout debugging and MPSK modulation simulation were completed.The results show that the vector modulator has good amplitude and phase.RMS error.Subsequent cavity processing and QPSK modulation tests reflect the better orthogonality of this MMIC.This design fully embodies the advantages of high precision and large bandwidth of the balanced structure.The other one is a reflective I-Q vector modulator MMIC with two inputs and eight outputs,designed to meet the requirements of space communication.It is based on WIN PP1551 process and works in 27~31GHz.The circuit focuses on miniaturization,low cost,and high isolation between channels.The isolation between RF output ports has reached about 25dB.The topological structure of the vector modulator is improved.by adopting folded Lange coupler and Wilkinson power splitter.This makes the entire chip occupying an area of only 3.2×3.2 mm~2,highlighting the advantage of a small area of the reflective structure.This MMIC is a rare design that integrates multiple vector modulators on a single chip.