D-band Broadband Mixer

In modern millimeter-wave communication system, the performance of the mixer has a significant impact on the receiver. The broad RF bandwidth of the broadband mixer can expand the working band of the receiver. Therefore, research on the broadband mixer is significant.Mixers can be divided into two categories: the fundamental and harmonic mixer. Compared with the harmonic mixer, the characteristics of the fundamental mixer, such as the conversion loss, are much more better. However, the millimeter-wave mixer works at a high frequency, which makes it’s difficult to develop the local-oscillator. So most of millimeter-wave mixers belong to harmonic mixer. With the improvement of the processing craft and design, local-oscillator has been realized in D-band frequency band. Therefore, researches on D-band low-loss fundamental wideband mixer become particularly important.D-band broadband integrated circuit mixer using a fin-line-suspended microstrip hybrid configuration is designed with UMS’s Schottky barrier diodes DBES105 a in this thesis. Finline and suspended microstrip make up a 180 degree knot which provides a well isolation between the RF and LO ports. The signal of RF passes through the waveguide-to-fin-line and RF-matching structure to the diode. The signal of LO passes through the waveguide-to-suspended microstrip to diode. The IF power is exported through a 5-order Chebyshev low-pass filter.The package of the diode has a tremendous effect on circuit performance at D band. After reviewing the information about the Schottky barrier diode modeling, a three dimension model is built up. In this model, an impedance boundary is used instead of the Schottky diode junction. A D-band fundamental wideband mixer is designed basis on the model. The simulation results are as follows: The return loss of RF port is greater than 10 dB in 110GHz~160GHz. The return loss of LO port is greater than 10 dB in 131GHz~148GHz. At the center frequency 140 GHz, the isolation between the LO and IF port is 21 dB.A D-band fundamental wideband mixer has been fabricated and tested. The LO frequency is 134 GHz with the power of 7.5mW. The conversion loss is less than 15 dB with the RF swept from 110GHz~155GHz. The conversion loss is less than 10 dB with the RF frequency from 115GHz~137GHz.