Won-Young Uhm

A high performance V-band monolithic quadruple sub-harmonic mixer

In this paper, we present a high performance V-band quadruple sub-harmonic mixer monolithic circuit which is designed and fabricated for the millimeter wave down converter applications. While the typical sub-harmonic mixers use a half of fundamental frequency, we adopt a quarter of the fundamental frequency. The proposed circuit is based on sub-harmonic mixer with APDP (anti parallel diode pair). Upon the typical mixer design, additional stubs are placed with the modification of original stub length. And the 0.1 /spl mu/m pseudomorphic high electron mobility transistors (PHEMTs) providing better gain are positioned to each port. Used lumped elements at IF port, it provides selectivity of IF frequency, and increases isolation. Maximum conversion gain of 0.8 dB at a LO frequency of 14.5 GHz and at a RF frequency of 60.4 GHz is measured. Both LO-to-RF and LO-to-IF isolations are higher than 40 dB. These conversion gain results and isolation characteristic are the best performances reported among the quadruple sub-harmonic mixers operating in the V-band millimeter wave frequency thus far.

High performance Q-band subharmonic receiver chip set

A high conversion gain receiver chip set for Q-band millimeter-wave wireless communication systems is designed and fabricated by using 0.1 /spl mu/m GaAs-based pseudomorphic high electron mobility transistors (PHEMTs) and the coplanar waveguide (CPW) library. The fabricated receiver chip set consists of a subharmonic mixer circuit and a low noise amplifier. From the device characterization, the subharmonic mixer shows a maximum conversion gain of /spl sim/4.8 dB at an RF frequency of 40 GHz for a local oscillation (LO) power of 10 dBm at 17.5 GHz. The subharmonic mixer also exhibits a high degree of isolation characteristic of -35.8 dB for LO-to-IF and -40.5 dB for LO-to-RF, respectively, at a LO frequency of 17.5 GHz. The low noise amplifier shows a S/sub 21/ gain of /spl sim/25.6 dB at a RF frequency of 40 GHz. Due to the high performances of the circuits, the fabricated receiver chip set produces a high conversion gain of 30.4 dB for the Q-band application purpose.

Reduced Hybrid Ring Coupler Using Surface Micromachining Technology for 94-GHz MMIC Applications

In this study, we developed a reduced 94 GHz hybrid ring coupler on a GaAs substrate in order to demonstrate the possibility of the integration of various passive components and MMICs in the millimeter-wave range. To reduce the size of the hybrid ring coupler, we used multiple open stubs on the inside of the ring structure. The chip size of the reduced hybrid ring coupler with multiple open stubs was decreased by 62% compared with the area of the hybrid ring coupler without open stubs. Performance in terms of the loss, isolation, and phase difference characteristics exhibited no significant change after the use of the multiple open stubs on the inside of the ring structure. The reduced hybrid ring coupler showed excellent coupling loss of 3.87±0.33 dB and transmission loss of 3.77±0.72 dB in the measured frequency range of 90–100 GHz. The isolation and reflection were −48 dB and −32 dB at 94 GHz, respectively. The phase differences between two output ports were 180°±1° at 94 GHz.

Design of a 94-GHz Single Balanced Mixer Using Planar Schottky Diodes with a Nano-Dot Structure on a GaAs Substrate

In this paper, we develop a 94-㎓ single balanced mixer with low conversion loss using planar Schottky diodes on a GaAs substrate. The GaAs Schottky diode has a nanoscale anode with a T-shaped disk that can yield high cutoff frequency characteristics. The fabricated Schottky diode with an anode diameter of 500 ㎚ has a series resistance of 21 Ω, an ideality factor of 1.32, a junction capacitance of 8.03 fF, and a cutoff frequency of 944 GHz. Based on this technology, a 94-㎓ single balanced mixer was constructed. The fabricated mixer shows an average conversion loss of -7.58 ㏈ at an RF frequency of 92.5 ㎓ to 95 ㎓ and an IF frequency of 500 ㎒ with an LO power of 7 ㏈m. The RF-to-LO isolation characteristics were greater than -32 ㏈. These values are considered to be attributed to superior Schottky diode characteristics.

Development of Planar Schottky Diode on GaAs Substrate for Terahertz Applications

In this paper, we demonstrate the planar Schottky diode on GaAs substrate for terahertz applications. A nanoscale dot and T-shaped disk has been developed as the anode for terahertz Schottky diode. The low parasitic elements of the nanoscale anode with T-shaped disk yield high cutoff frequency characteristic. The fabricated Schottky diode with anode diameter of 500 nm has series resistance of 21 Ω, ideality factor of 1.32, junction capacitance of 8.03 fF, and cutoff frequency of 944 GHz.