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A broadband travelling-wave modulator is proposed based on Si 2 N 2 O substrate with ridge structure. The structure is analyzed using finite element method. At 1.5 μm wavelength the modulator operates with a 3 dB optical bandwidth of 119.37 GHz, a half-wave driving voltage of 3.5 V, and characteristic impedance of 50.32 Ω. The results show that broad bandwidth and low half-wave voltage can be achieved simultaneously.

In this letter, a novel terahertz (THz) wave switch based on metamaterial is proposed and measured.On–off switching is based on a controllable resonance of the metamaterial by applying an external semiconductor laser to illuminate substrate. Experimentally, we demonstrate on–off response time speed and extinction ratio of the proposed THz wave switch is of 1 ms and 19.4 dB at 0.32 THz, respectively. The presented THz wave switch has a potential application to THz wave communication systems. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:276–278, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25751

A novel array antenna applied to WLAN communication system is proposed.The presented antenna provides frequency band from 2400 to 2480 MHz, realized in a commercial Teflon printed circuit board with a permittivity of 2.65 and a thickness of 0.7 mm. Both simulation and measurement are pretty matched and indicate that the proposed antenna achieves the maximum gains to be 15.90 dBi (E-plane) and 15.85 dBi (H-plane) at 2480 MHz band, respectively. The antenna performances and compact size of the proposed antenna are easy to be applied in the WLAN communication products. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1461–1463, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25229

A novel magnetically tunable left-handed material based on YIG/SRR was designed. Both theoretical analysis and calculation results show that the presented structure achieves a left-handed pass band in the THz frequency range.

We measured terahertz time-domain spectra of three kinds of nano-metal samples. The results show that the nano-metals have many distinct characteristic spectra between 0.2 and 2.6THz. THz-TDS can be used to analysis nano-metal.

A novel terahertz wave absorber is proposed. Theoretical results show that the absorber has a high absorptivity of 99.968% and a minimum reflectivity of 0.032% at frequency of 0.28THz. The absorption bandwidth is of 316.5GHz.

We design the terahertz wave filter based on microstrip structure. The experimental result shows that the terahertz wave filter has dual passband transmittance peak of 66.5% at 2.347THz and 60% at 2.76 THz.

Terahertz wave filter, a metal micro-structure, has been characterized by the mode-matching theory. The peak of the transmittance of is about 99.99% from 0.835THz to 1.161THz and 3dB bandwidth of 326GHz.

The terahertz time-domain spectra (THz-TDS) of four kinds of vegetable oils were measured in the frequency range extending from 0.2 to 1.5 THz. An iterative algorithm is employed to determine the parameter extraction for terahertz time-domain spectroscopy. The terahertz absorption spectra and refractive indices of four kinds of vegetable oils were analyzed. Compared with the existing data extraction algorithms, the novel iterative algorithm further enhances the accuracy of the parameter extraction for terahertz time-domain spectroscopy.

By using terahertz time domain spectroscopy (THz-TDS) system, the terahertz dielectric properties of various gallium arsenides were tested in the frequency range extending from 0.2 to 1.5 THz. The power absorption coefficient and refractive index of various resistivity gallium arsenides were measured and compared. The refractive index of the high resistivity and ultra-high resistivity GaAs are equal to be 6.53 and 5.9, respectively. The variation of the refractive index of the GaAs was less than 1%, ranging from 0.2 to 1.5THz, but the absorption coefficient of the ultra-high resistivity GaAs showed very different frequency-dependent behaviors, ranging from 0.02cm−1 to 2.21cm−1, within the investigated frequency range. The results show that the ultra-high resistivity GaAs will be a good candidate material for terahertz transmission waveguide.

In this paper, the proposed three-port power divider based on four stages cavity, which is different to the conventional power divider using coupled transmission line. The design and simulated results show that the novel power divider has a good performance, which are insert loss 4.77plusmn0.13 dB from 690 MHz to 2.5 GHz, and return loss less than -18 dB, respectively. In addition, the performances of the novel power divider are demonstrated experimentally. The measured results are good well with the simulated ones.

A compact RF coupler suitable for integrated microwave and millimetre wave applications has been proposed fabricated, and measured for the first time. The novel wideband RF coupler based on cavity offer coupling in the range of 3-10 dB over an ultra-wide frequency band from 700 MHz to 2.5 GHz. The performances of the proposed RF coupler are demonstrated by measured results, which are good agreement with the simulations.

A novel compact sub-terahertz wave switch based on photonic crystals is proposed. We have investigated the performance of the proposed sub-terahertz wave switch by using plane wave expansion and finite-difference time-domain method. The numerical results show that an excellent sub-terahertz wave switch at a frequency of 0.1THz is achieved. The proposed sub-terahertz wave switch has a high extinction ratio of -40dB, and small size of 6.811mm. It has a potential application to sub-terahertz wave communication systems.

A novel bandstop filter based on composite right/left-handed (CRLH) transmission line (TL) is proposed and studied. This designed bandstop filter provides low passband insertion loss, very sharp transitions at the edges of the stopband, large attenuation in the stopband, easy fabrication, and low cost. The performances of the proposed filter are demonstrated by simulation results.

A novel narrow-band bandpass filter using metamaterials is proposed. The filter is composed of cascaded four metamaterial unit cells. We study the properties of the device theoretically and experimentally. The measured results are presented and compared with the results simulated by a high-frequency structure simulator. It is observed that the measured results are good agreement with the simulated results. The proposed filter has narrow bandwidth, low insertion loss, compact dimensions, easy fabrication, and low cost.

Left-handed transmission lines (LHTLs) are used in this letter to design a novel Wilkinson power divider. In our design, the lumped L-C LHTLs (-lambda/4) is instead of the right-handed transmission lines which is used as branch arms of the conventional Wilkinson power divider. The simulated results show that the novel power divider has a wide bandwidth of return loss and isolation, and its size is 50% smaller than conventional Wilkinson power dividers. The novel Wilkinson power divider has many advantages over conventional power divider in e. g. the size, weight, simplicity, low insertion loss, bandwidth of isolation, and cost.

A new metamaterial unit cell is proposed. The metamaterial unit cell consists of microstrip gaps and via hole whose behavior is equivalent to the combination of series capacitors and shunt inductors respectively. A novel chamfered band is designed and fabricated using the presented metamaterial unit cell. The simulation and experiment results show the microwave characteristics of the proposed structure have advantageous over those of conventional chamfered band. The experiment and simulation results closely correspond to each other.

The coupling length and coupling ratio is defined as input and output respectively, which are used to train the neural network model. RBF neural network model is built for optical fiber direction coupler, which is in turn simulated and designed through the model. This method has the advantages of speediness, accuracy and reliability, which are identified by the design example. It can be used to design the other kind of optical passive device. This way is a novel design approach, which can save the cost of device design, decrease period of design and has a good prospect of application.

BP and RBF neural network methods have been used to design optical fiber temperature sensor probe used in medical treatment. Datum trained for neural network is gained from experiment and interpolation. This method has the characteristics of accuracy credibility and knowledge-aid design, which can save the device cost of design and decrease period of design. This way has a good prospect of application.

Artificial neural network model of coupling micro-strip line is built, and used in its analysis and design. With its good precision and effectiveness, the application of neural network has the advantages of reliability, accuracy, time saving, and knowledge aid design. In this paper, with the structure size of coupling micro-strip line defined as input samples and the odd and even mode characteristic impedance and the normalized wavelength defined as output samples, a kind of coupling micro-strip line is designed by the method. The results promise a good prospect of the application.

A sample realizable method for terahertz wave modulation is demonstrated experimentally by using optical controllable ultra-high resistivity silicon wafer. With modulated 100 mw of 808 nm CW light, a maximum of 21 dB terahertz attenuation was achieved with 0.2 kb/s of modulation speed. The experimental results show good agreement with the Drude-Lorentz model. Further work is underway to improve the modulation speed above Mb/s. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2825–2826, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24798