Wan-Joo Kim

A Transceiver Module for FMCW Radar Sensors Using 94-GHz Dot-Type Schottky Diode Mixer

In this study, we fabricated a 94-GHz transceiver module for a millimeter-wave (MMW) frequency modulation continuous wave (FMCW) radar sensor. The transceiver modules consist of a waveguide voltage-controlled oscillator (VCO) and Rx module using a single balanced mixer. We designed a mixer with a conversion loss of 6.4 dB, without using an amplifier. Also, the waveguide VCO consisted of an InP Gunn diode, a varactor diode, two bias posts with LPF, and a Magic Tee for the MMW radar transceiver. The fabricated VCO has a tuning range of 1280 MHz by a varactor bias of 0~20 V, 1.69% linearity range of 680 MHz, and current consumption of 154 to 157 mA. The completed module has a good conversion loss of 10.6 dB with an LO power of 11.4 dBm at 94 GHz. With this RF and LO input power, the conversion loss was maintained between 10.2-11.5 dB in the RF frequency range of 93.67-94.95 GHz.

A Novel 94-GHz MHEMT Resistive Mixer Using a Micromachined Ring Coupler

In this letter, we present a high performance 94-GHz millimeter-wave monolithic integrated circuit resistive mixer using a 70-nm metamorphic high electron mobility transistor (MHEMT) and micromachined ring coupler. A novel three-dimensional structure of a resistive mixer was proposed in this work, and the ring coupler with the surface micromachined dielectric-supported air-gap microstrip line structure was used for high local oscillator/radio frequency (LO-RF) isolation. Also, the LO-RF isolation was optimized through the simulation. The fabricated mixer has excellent LO-RF isolation, greater than 29 dB, in 2-GHz bandwidth of 93-95GHz. The good conversion loss of 8.9dB was measured at 94GHz. To our knowledge, compared to previously reported W-band mixers, the proposed MHEMT-based resistive mixer using a micromachined ring coupler has shown superior LO-RF isolation and conversion loss

W-band Waveguide-to-Coplanar Waveguide Transition for 94 GHz MIMIC applications

In this paper, we report our recent research works on the W-band waveguide-to-CPW transitions for various MIMIC applications. For this, the transitions operating in a frequency range of 85 ~ 100 GHz are designed, fabricated and characterized. The designed waveguide-to-CPW transition is optimized to achieve low loss by using an EM field solver of HFSS. From the measurement, an insertion of -2.2 dB and a return loss of -23.86 dB, respectively, were obtained at 94 GHz. The average insertion loss of waveguide-to-CPW back-to-back transition is -2.5 dB in a frequency range of 85 ~ 100 GHz.

Two-Element Conformal Antenna for Multi-GNSS Reception

This letter presents a two-element conformal antenna for receiving the global positioning system L1, L2, and GLONASS L1 signals for precision artillery applications. The antenna consists of two stub-loaded shorted conformal patches fed by coaxial cables and a stripline power combiner. The patch is realized on a cylindrical polymer substrate wrapped around an artillery fuze body. Two patches are placed 180° apart and combined to realize an omnidirectional pattern. The fabricated antenna shows good Global Navigation Satellite System signal receiving performance.

94GHz Single-balanced Diode Mixer for FMCW Radar applications

In this paper, we present a high performance 94 GHz MMIC diode mixer using a 100-nm metamorphic high electron mobility transistor (MHEMT) diode and coplanar waveguide (CPW) 3-dB tandem coupler. A novel single-balanced structure of MHEMT diode mixer was proposed in this work, and 3-dB tandem coupler with the air-bridge structure was used for broadband LO-RF isolation. The fabricated mixer has LO-RF isolation, greater than 19 dB, in 15 GHz bandwidth of 82-97 GHz. The good conversion loss of 14.8 dB was measured at 94 GHz.

A 94 GHz diode mixer for low LO power operation

For low LO power and broadband characteristics of the mixer, an antipodal fin-line to microstrip transition for operation in the 94 GHz frequency has been designed and characterized. Back to back transitions fabricated on soft substrates have been measured and simulated to verify their behavior. A single balanced fin-line mixer was designed and fabricated. In the mixer, a wideband fin-line to coplanar waveguide 180/spl deg/ balun and low pass filter were used. Conversion loss is less than 10 dB at LO power of 6 dBm.

Fabrication of GaAs Gunn diodes using trench method

We developed the improved fabrication technology using the trench method for a graded-gap injector GaAs Gunn diode to avoid the formation of cracks which are caused by the difference in the thermal expansion coefficients between the GaAs epi-layer and the gold integral heat sink. We observed the negative-differential-resistance in the fabricated Gunn diode. The process we developed facilitates further process and handling because of the integral heat sink with thickness of 60 mum. Also, the formation of cracks in GaAs epi-layer was reduced during ohmic alloy process because of the reduced stress between the epi-wafer and the gold integral heat sink.

94 GHz waveguide VCO using InP Gunn diode for FMCW radar applications

The 94 GHz waveguide VCO using InP Gunn diode was designed and fabricated. The fabricated VCO has excellent linearity of 1.7 % at 680 MHz bandwidth and power flatness of 0.68 dBm, respectively. The LPF is designed under -40 dB at 47 GHz and the resonator is designed for frequency generation at 47 GHz. From the measured results the fabricated waveguide VCO has excellent performances: the bandwidth is 1365 MHz at 93.98 ~ 95.345 GHz and the output power range is from 14.78 dBm to 15.46 dBm. The phase noise is under -100 dBc / Hz at 1 MHz offset.