Ya-Fen Ge

Terahertz beam scanning offset Cassegrain reflector antenna

This paper presents a terahertz high-gain antenna which has a certain beam scanning capability and the antenna also has an offset Cassegrain reflector structure. Beam scanning method is analyzed by the theory of quasi-optics. Moreover, we elaborate critical analysis algorithm of the antenna. Simulation results show that, in the initial position, the gain of the antenna is 44.98dB, the half-power beam width is 1 degree and the side lobe level is -29.35dB. Beam scanning angle in the horizontal and vertical direction is within ±10° respectively, the gain and beam width vary within a reasonable range and the side lobe level is always lower than -20dB. In general, the antenna can be used for scanning terahertz imaging system.

Design of a 6–18 GHz UWB conformal antipodal Vivaldi antenna array

In this paper a conformal antipodal Vivaldi antenna array on a cylindrical surface for ultra-wideband (UWB) applications is proposed. The cylindrical antenna is mounted on the surface of the cylindrical object. The conformal antenna has good characteristics after a optimization for the geometry parameters of antenna. Vivaldi antenna array with four antenna on cylindrical surface can be designed with a UWB of several octaves, and with circularly polarization. Results show that the conformal Vivaldi antenna array can be a suitable choice for UWB and circularly polarization application on curved surface.

Double-Layer 90° corrugated terahertz horn antenna based on MEMS technology

A double-layer 90° corrugated terahertz (THz) horn antenna based on MEMS (Micro-electromechanical System) technology is proposed. This antenna is designed at the frequency range of 400GHz-500GHz. Through adding expansion aperture and chokes to the traditional structure, good antenna performance can be obtained. From the simulated result it shows a impedance bandwidth of 400-500GHz with input return loss less than 10dB. The radiation pattern shows good symmetric beamwidth and very low cross-polarization. The peak gain varies from 13.9dBi to 16.1dBi within the frequency band 400GHz-500GHz. Dry etching MEMS technology is suitable for design of this type of antenna.

Design of ultra-wideband printed log-periodic dipole antenna

An ultra-wideband low cross-polarization printed log-periodic dipole antenna (LPDA) is systematically investigated. The properties of the proposed antenna have been Simulated and optimized with electromagnetic simulation software FEKO 6.2. The antenna possess the operating bandwidth from 0.8GHz to 7.2GHz with the return loss less than -10dB, the cross-polarization and side lobe level are less than -30dB. The Gain of the antenna is greater than 8.25 dB during the operation bandwidth, and very good End-fire directivity is obtained.

0.5 THz integrated antipodal curvilinearly tapered slot antenna with circular polarization

A novel 0.5THz integrated antipodal curvilinearly tapered slot antenna(ACTSA) with circular polarization is introduced in this paper. The proposed antenna is fed by traditional waveguide and circular polarization is achieved by antipodal curvilinearly tapered slot structure. The antenna structure is well suitable designed by Micro-electromechanical systems (MEMS) technology. The proposed antenna is simulated and optimized by Finite Element Method. The simulation results show the antenna has a good performance, including impedance bandwidth (-20dB) of >20%, gain of >11.5dBi, axial ratio bandwidth of 12%, HPBW of 52° and 44° at φ=0° and φ=90°, SLL of -22.1dB and -13.4dB at φ=0° and φ=90°. Cross-polarization level is less than -20.5dB and front-back-ratio is 26.5dB.

Analysis and modeling of GaAs-based coupled microstrip lines

This paper describes one of the critical technologies of very high speed integrated circuits (VHSICs), the equivalent circuit model of the GaAs substrate based coupled microstrip lines. We present a method that extracts a frequency-dependent tabular RLGC model from mixed-mode S-parameters estimated by EM simulation (software HFSS). This paper shows that the using a conventional modal decomposition can extend a two-line method for a single transmission line to a two-line method for a symmetrical coupled pair. This method can be contributed to establish the component library and analyze crosstalk and delays for GaAs-based transmission lines used in VHSICs widely.

A low-power decibel-linear CMOS Automatic Gain Control

This paper presents an all CMOS decibel-linear Automatic Gain Control (AGC). This AGC achieves large dynamic range with low power consumption. By applying digital switches to change exponential approximation function, four dynamic ranges (62, 50, 33, 26 dB) are realized. This AGC is implemented in TSMC 0.18-μm CMOS RF process. Measurement results show that this AGC achieves 60 dB linear range with linearity error less than 1 dB. The whole circuit consumes 3.6 mA from 2-V supply.

A low-power-consumption linear-in-dB CMOS VGA

This paper presents a low-power and small-size variable gain amplifier (VGA) which consumes only 1.1mW and occupies only 132um × 59um in 0.18-um CMOS technology. The proposed circuit is implemented by Gilbert cells and an exponential function circuit for the dB linearity of the gain voltage. The gain of the VGA can be varied linearly in dB from -10dB to 50dB with respect to a control voltage from 0.2V to 0.85V. The operation frequency is only 10MHz, but the VGA maintains 3dB-bandwidth wider than 46MHz throughout its gain range. At the worst case, the amplitude of the output can be 300mV when THD is lower than -40dBc. The total simulation is based on TSMC 0.18um. Low power consumption is obtained owing to high transition frequency of the transistors in 0.18-um CMOS technology.

A 20MHz continuous-time Gm-C filter with source degeneration linearization technique

A fifth-order Gm-C low-pass filter, which employs source degeneration linearization technique, used in analog frontend anti-aliasing is presented. This filter was simulated in the TSMC 0.18-μm CMOS process design kit (PDK) with 5-fF/μm2 MIM capacitors. This simulated filter features corner frequency of 20MHz, power consumption less than 4mW, supply voltage of 2V, THD of 1% at 260mVpp. The total area of this design is less than 0.2mm2.

Design of Ka-band front end of fully polarized radiometer

A Ka-band front end of fully polarized microwave radiometer is designed, which consists of ortho-mode transducer (OMT) and multimode horn (MMH). The front end is analyzed using the finite element method. The simulation results show it has a good performance. The two ports isolation of the front end is larger than 53 dB, the gain of the front end is larger than 22.4 dBi, the sidelobe level is less than -24.9 dB and the VSWR in the bandwidth is lower than 1.2.