The Study Of W-band MMIC Balanced I-Q Vector Modulator

Due to the advantage of small size, light weight, high reliability, high stability,strongly anti-interference ability and good consistency of products’ performance,microwave and millimeter-wave monolithic integrated circuits (MMICs) are widelyused in millimeter wave systems, especially in the field of national defense and military.This paper first introduces the characteristics of MMIC technology, and its currentsituation and dynamic development at home and abroad.The high-performance vector modulator plays an increasingly important role inmany millimeter-wave systems, such as phased array radar, radar RF cancellationsystem and pre-distortion system. The research abroad on vector modulator began in1980s, is now quite mature, mainly through MMIC process, while domestic research isstarted lately, mainly through hybrid integration method. In this paper, two MMICs ofbalanced I-Q vector modulator have been designed; they are operating in the Ka-bandand W-band respectively. The design and test of the W-band vector modulator chip ispioneering in China.This paper first introduces the different types of vector modulator, points out theiradvantages and disadvantages. To fully exploit this circuit’s capacity to generateaccurate constellations at millimeter-wave frequencies, a generalized theoreticalanalysis of the I-Q vector modulator is presented. This is a comprehensive analysis ofthe topology and does not assume ideal components. Secondly, describes the designprocess of the I-Q vector modulator’ sub-circuits, including Lange coupler, Push-pullmodulator and in-phase combiner. In order to optimize modulators’ performance, rightsize of the pHEMT has been chosen, and then achieves good simulation results of thetwo I-Q vector modulators. All the designs are based on Win’s proven standard0.15umgate low noise pHEMT production process.In the final, a W-band Push-pull modulator MMIC is fabricated, The chipdimension is1.35mm×0.83mm. In order to test this chip, this paper uses a40GHzvector network analyzer to build a W-band automatic probe test platform through spreadspectrum technology. The test results show that this chip achieves good performance in amplitude modulation and phase modulation. After that, this paper analyses the test andsimulation results and proposes improvement program.