We present an analysis of microstrip coupled lines (MCLs) used to improve the stability of a 60 GHz narrowband amplifier. The circuit has a 4-stage structure implementing MCLs instead of metal-insulator-metal (MIM) capacitors for the unconditional stability of the amplifier and yield enhancement. The stability parameter, U, is used to compare the stability of MCLs with that of MIM capacitors. Experimental results show that MCLs are more stable than MIM capacitors with the same capacitances as MCLs because the parasitic parallel resistances of MCLs are lower than those of MIM capacitors. Moreover, the bandwidth of an amplifier using MCLs is narrower than one using MIM capacitors because the parasitic series inductances of MCLs are higher than those of MIM capacitors.

We report on the fabrication of an AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) using a dielectric-defined process. This process was utilized to fabricate 0.12 μm × 100 µm T-gate PHEMTs. A two-step etch process was performed to define the gate footprint in the SiN_x. The SiN_x was etched either by dry etching alone or using a combination of wet and dry etching. The gate recessing was done in three steps: a wet etching for removal of the damaged surface layer, a dry etching for the narrow recess, and wet etching. A structure for the top of the T-gate consisting of a wide head part and a narrow lower layer part has been employed, taking advantage of the large cross-sectional area of the gate and its mechanically stable structure. From s-parameter data of up to 50 GHz, an extrapolated cut-off frequency of as high as 104 GHz was obtained. When comparing sample C (combination of wet and dry etching for the SiN_x) with sample A (dry etching for the SiN_x), we observed an 62.5% increase of the cut-off frequency. This is believed to be due to considerable decreases of the gate-source and gate-drain capacitances. This improvement in RF performance can be understood in terms of the decrease in parasitic capacitances, which is due to the use of the dielectric and the gate recess etching method.

This paper introduces the design and the implementation of the 60 GHz amplifier MMICs and the module for the 60 GHz WPAN system with a RoF (radio-over-fiber) link. The MMICs were designed using ETRI's 0.12 mum GaAs PHEMT 4-inch process. The MCLFs (microstrip coupled line filters) compared with the MIM (metal-insulator-metal) capacitors have greater stability and less effect by the variation of fabrication. The 60 GHz drive amplifier MMIC and the 60 GHz power amplifier MMIC were designed by 4-stage structures using the MCLFs instead of the MIM capacitors for unconditional stability of the amplifiers and yields enhancement. The fabricated 60 GHz drive amplifier (DA) MMIC achieves a small signal gain (S₂₁) of 22 dB, a gain flatness of 0.8 dB, an input reflection coefficient (S₁₁) of -12 ~ -9 dB and an output reflection coefficient (S₂₂) of -10 ~ -7 dB for 59.5 to 60.5 GHz. The fabricated 60 GHz power amplifier (PA) MMIC achieves an S₂₁ of 15 dB, a gain flatness of 0.04 dB, an S₁₁ of -12 dB, an S₂₂ of -12 ~ -11 dB and an output P_1dB of more than 14 dBm for 59.5 to 60.5 GHz. The chip sizes of the DA and the PA are 3.8 times 1.6 mm² and 3.7 times 1.6 mm ², respectively. The waveguide-typed module was implemented with a DA MMIC and a PA MMIC. And it performed an S₂₁ of 38 ~ 39 dB, a gain flatness of 1.2 dB, an S₁₁ of -29 ~ -26 dB, an S₂₂ of -16 ~ -14 dB and an output P_1dB of 12.3 ~ 14.3 dBm for 59.5 to 60.5 GHz. And the size of the module is 8.0 times 6.0 times 2.3 cm³

In this study, an E‐band low‐noise amplifier (LNA) monolithic microwave integrated circuit (MMIC) has been designed using silicon‐germanium 130‐nm bipolar complementary metal‐oxide‐semiconductor technology to suppress unwanted signal gain outside operating frequencies and improve the signal gain and noise figures at operating frequencies. The proposed impedance‐controllable filter has series (R_s) and parallel (R_p) resistors instead of a conventional inductor‐capacitor (L‐C) filter without any resistor in an interstage matching circuit. Using the impedance‐controllable filter instead of the conventional L‐C filter, the unwanted high signal gains of the designed E‐band LNA at frequencies of 54 GHz to 57 GHz are suppressed by 8 dB to 12 dB from 24 dB to 26 dB to 12 dB to 18 dB. The small‐signal gain S₂₁ at the operating frequencies of 70 GHz to 95 GHz are only decreased by 1.4 dB to 2.4 dB from 21.6 dB to 25.4 dB to 19.2 dB to 24.0 dB. The fabricated E‐band LNA MMIC with the proposed filter has a measured S₂₁ of 16 dB to 21 dB, input matching (S₁₁) of –14 dB to –5 dB, and output matching (S₂₂) of –19 dB to –4 dB at E‐band operating frequencies of 70 GHz to 95 GHz.

This paper describes the performance of a Ku-band 5-bit monolithic phase shifter with metal semiconductor field effect transistor (MESFET) switches and the implementation of a ceramic packaged phase shifter for phase array antennas. Using compensation resistors reduced the insertion loss variation of the phase shifter. Measurement of the 5-bit phase shifter with a monolithic microwave integrated circuit demonstrated a phase error of less than 7.5° root-mean-square (RMS) and an insertion loss variation of less than 0.9 dB RMS for 13 to 15 GHz. For all 32 states of the developed 5-bit phase shifter, the insertion losses were 8.2 ± 1.4 dB, the input return losses were higher than 7.7 dB, and the output return losses were higher than 6.8 dB for 13 to 15 GHz. The chip size of the 5-bit monolithic phase shifter with a digital circuit for controlling all five bits was 2.35 mm × 1.65 mm. The packaged phase shifter demonstrated a phase error of less than 11.3° RMS, measured insertion losses of 12.2 ± 2.2 dB, and an insertion loss variation of 1.0 dB RMS for 13 to 15 GHz. For all 32 states, the input return losses were higher than 5.0 dB and the output return losses were higher than 6.2 dB for 13 to 15 GHz. The size of the packaged phase shifter was 7.20 mm × 6.20 mm.