Study Of Ka-band I/Q Modulator

Heterojunction bipolar transistor (HBT) is one of the most important devices in millimeter wave and microwave applications, and GaAs HBT has better high frequency characteristics, insulation performance and higher current gain. In this paper, I/Q modulators were proposed based on Ka-band GaAs HBT device.Firstly, a I/Q modulator based on Ka-band mixer Gilbert cell structure is completed in which the degree of carrier suppression is about 27.7dB, and degree of sideband suppression is about 26.6dB.Secondly, reflection-type binary phase-shift keying and in-phase and quadrature modulator are reported which is the main work in this paper. A cold-mode HBT device model with varying bias conditions is proposed, which is suitable for millimeter-wave circuit design and simulation. The analysis and design for the reflection-type modulators are also presented which including the design of Ka-band Lange coupler and Ka-band Wilkinson power divider .The vector modulator carrier suppression of about 25.6dB, sideband suppression is about 27dB.Finally, the basis of the I/Q vector modulation circuit further proposed a new circuit structure, through the improvement of the original circuit does not affect the circuit functions in the premise of saving a lot of chip area, thus saving production costs.