Micromachined V-band CMOS bandpass filter with 2 dB insertion loss

A low-insertion-loss V-band CMOS bandpass filter is demonstrated. The proposed filter architecture has the following features: the low-frequency transmission-zero (vz1) and the high-frequency transmission-zero (vz2) can be tuned by the series-feedback capacitor Cs and the parallelfeedback capacitor Cp, respectively. To reduce the substrate loss, the CMOS process compatible backside inductively-coupled-plasma (ICP) deep trench technology is used to selectively remove the silicon underneath the filter. After the ICP etching, this filter achieved insertion loss (1/S21) lower than 3 dB over the frequency range 52.5?76.8 GHz. The minimum insertion loss was 2 dB at 63.5 GHz, the best results reported for a V-band CMOS bandpass filter in the literature.     

Untuned low insertion loss surface leaky wave filter

The letter presents a broadband low insertion loss surface leaky wave filter using reflective multistrip couplers on an optimum cut and orientation of lithium niobate. The insertion loss has been reduced to 3?4 dB without any inductors for phase-shift networks or tuning, and the out-of-band rejection is about 23 dB. The fractional bandwidth is up to 2?5%. The out-of-band rejection can be reduced to 40 dB, when the IDTs are apodised.     

一种低插入损耗的180 GHz腔体滤波器

基于H形感性窗结构设计了一款低插入损耗的8阶波导腔太赫兹滤波器.经Ansoft HFSS对滤波器进行仿真优化后,滤波器采用传统的数控铣进行实物加工.测试结果表明:滤波器的中心频率位于179.1 GHz,1 dB相对带宽为8.7％.滤波器中心频率处的插入损耗为0.34 dB,回波损耗优于18.9 dB.所设计的太赫兹腔体...     

低损耗贴片式独块状介质滤波器的设计与制作

设计制作了一种低损耗、贴片式(SMD)独块状的八级介质滤波器。该滤波器采用切比雪夫响应的方法设计,利用εr为45的高Q值独块状微波陶瓷制作,谐振器之间使用电容和电容加载耦合。制备出了中心频率为897.5MHz、插入损耗小于2.5 dB的介质滤波器。测试结果表明,该滤波器满足800~1 500 MHz频率范围通讯基站要求。     

Design of a low loss SAW reflector filter with extremely widebandwidth for mobile communication systems

The design and performance of a low-loss surface acoustic wave (SAW) reflector filter are presented. The structure is a dual-track configuration incorporating two interdigital transducers (IDTs) and reflectors in each track. Extremely wide bandwidth can be obtained if chirped IDTs and reflectors are used. From the theoretical conditions for low-loss operation of the reflector filter, a design rule for the distances between the chirped components and for their lengths is derived. Because the transfer function of the filter is predominantly determined by the reflectors, a new synthesis method for chirped reflectors has been developed. For the design of the reflectors, phase-weighting and finger-width-weighting techniques were used to reduce passband distortions and improve the shape factor and stopband rejection. The filter has been fabricated on 128° YX-LiNbO₃ . The center frequency and fractional bandwidth are 200 MHz and 100%, respectively, the minimum insertion loss is 4 dB, a passband ripple is about 1 dB, and the stopband rejection is better than 35 dB     

Narrow-aperture SAW filter with both transducers finger-length-weighted

A 2.5 ?-aperture SAW filter has been designed and tested. The single-mode nature of the waveguiding filter allows finger-length-weighting to be distributed between input and output transducers according to a simple procedure. The resulting filter has a stopband rejection in excess of 50 dB.     

AlGaN/GaN high electron mobility transistors with selective area grown p-GaN gates

We report a selective area growth (SAG) method to define the p-GaN gate of AlGaN/GaN high electron mobility transistors (HEMTs) by metal-organic chemical vapor deposition. Compared with Schottky gate HEMTs, the SAG p-GaN gate HEMTs show more positive threshold voltage (V_th) and better gate control ability. The influence of Cp₂Mg flux of SAG p-GaN gate on the AlGaN/GaN HEMTs has also been studied. With the increasing Cp₂Mg from 0.16 μmol/min to 0.20 μmol/min, the V_th raises from -67 V to -37 V. The maximum transconductance of the SAG HEMT at a drain voltage of 10 V is 113.9 mS/mm while that value of the Schottky HEMT is 51.6 mS/mm. The SAG method paves a promising way for achieving p-GaN gate normally-off AlGaN/GaN HEMTs without dry etching damage.     

Tunable thin-film filter with low angle sensitivity

Conventional angle-tuned thin-film filters have serious angle sensitivity for their low spacer effective refractive index, and it is difficult to fabricate their angle control system. In this paper, we propose and fabricate a novel 100 GHz angle-tuned thin-film filter stack with low angle sensitivity, which uses the high refractive index material TiO2 as the spacer, and its incident angle can be expanded to 25°. Compared with the traditional Ta2O5-SiO2 thin-film filter stack, the novel stack has fewer layers. Using the polarization beam splitters and the half wave plates, the polarization sensitivity of the angle-tuned filter can also be suppressed. Simulation results and the experiments show that the thin-film filter with low angle sensitivity has an effective tuning range of 33 nm, which can cover the whole C-band, and its angle control system is easy to be fabricated.     

16-band integrated dynamic gain equalization filter with less than2.8-dB insertion loss

We demonstrate a low-loss 16-band dynamic gain equalization filter consisting of two perfectly sampled waveguide grating routers (WGRs) and an array of thermooptic attenuators. This integrated silica waveguide filter has <2.8-dB fiber-to-fiber insertion loss, <0.2-dB polarization-dependent loss at minimum attenuation and <0.7-dB at 10-dB extra attenuation, and <5.0-W electrical power consumption over the C-band. We also demonstrate a new technique for reducing the loss of WGRs     

8000-V 1000-A gate turn-off thyristor with low on-state voltage andlow switching loss

An 8 kV, 1 kA gate turn-off thyristor (GTO) that has been designed with a combination of a p-i-n structure and a ringed-anode short structure is discussed. The GTO has been fabricated using a diffusion and epitaxial buffer process. As a consequence, low on-state voltage and low switching loss have been achieved, solving the two major problems in high-voltage GTOs. The device's structure, the p-i-n base process, and the electrical characteristics of the GTO are described     

P 型氮化镓层生长压力对InGaN/GaN基发光二极管性能的影响

The advantages of In Ga N/Ga N light emitting diodes(LEDs) with p-Ga N grown under high pressures are studied.It is shown that the high growth pressure could lead to better electronic properties of p-Ga N layers due to the eliminated compensation effect.The contact resistivity of p-Ga N layers are decreased due to the reduced donor-like defects on the p-Ga N surface.The leakage current is also reduced,which may be induced by the better filling of V-defects with p-Ga N layers grown under high pressures.The LED efficiency thus could be enhanced with high pressure grown p-Ga N layers.     

Structural characterization of bulk GaN crystals grown under high hydrostatic pressure

This paper describes TEM characterization of bulk GaN crystals grown at 1500–1800Kin the form of plates from a solution of atomic nitrogen in liquid gallium under high nitrogen pressure (up to 20 kbars). The x-ray rocking curves for these crystals were in the range of 20–30 arc-sec. The plate thickness along thec axis was about 100 times smaller than the nonpolar growth directions. A substantial difference in material quality was observed on the opposite sides of the plates normal to thec direction. On one side the surface was atomically flat, while on the other side the surface was rough, with pyramidal features up to 100 nm high. The polarity of the crystals was determined using convergent-beam electron diffraction. The results showed that, regarding the long bond between Ga and N along the c-axis, Ga atoms were found to be closer to the flat side of the crystal, while N atoms were found to be closer to the rough side. Near the rough side, within 1/10 to 1/4 of the plate thickness, there was a high density of planar defects (stacking faults and dislocation loops decorated by Ga/void precipitates). A model explaining the defect formation is proposed.     

Optical-fibre tap with low insertion loss

We report a fibre-tapping element which uses part of the insertion loss of a fibre connector or splice as useful optical signal power. A tapping fraction of up to 70% has been measured with a total insertion loss of 0.22 dB.     

Low loss and high performance SAW filters for 800 MHz mobile telephone transceiver

Low loss surface acoustic wave (SAW) filters have been developed for use in the radio frequency circuits of the mobile telephone transceiver. Both the UHF (800 MHz) and VHF (90 MHz) band-pass filters have exhibited high performance, and the employment of the SAW filters has shown advantages in UHF/VHF circuit integration for mass production.     

低插损极窄带声表面波滤波器设计

利用集总参数等效电路模型计算了声表面波双模耦合谐振滤波器的频响．通过改变谐振器各个参量使滤波器指标满足要求．在ＳＴ石英基片上成功研制出中心频率２２８ＭＨｚ，△ｆ－３ｄＢ＝１５０ｋＨｚ，插损为３ｄＢ，阻带抑制小于－５０ｄＢ的铁路专用寻呼机用滤波器。理论计算与实验结果一致。     

New low-loss broadband SAW filter using unidirectional IDTs with U-shaped MSCs

A new low-loss broadband SAW filter is presented. A new configuration using one pair of electrically connected IDTs with an optimum number of fingers, as well as unidirectional IDTs with U-shaped MSCs, is described. Experimental results with bandwidth as wide as 10% and loss as low as 3 dB are achieved. Very accurate computer-aided design of a low-loss filter with MSCs is obtained.     

Amorphous-silicon thin-film transistors with very high field-effectmobility

The fabrication and performance of hydrogenated amorphous-silicon (a-Si:H) thin-film transistors (TFTs) with field-effect mobilities of 5.1 cm²/V-s are discussed. This is the highest field-effect mobility of this type of TFT reported to date. The device shows an on/off current ratio exceeding 10⁵ and a subthreshold swing of 0.5 V/decade     

Submicron AlGaN/GaN HEMTs with very high drain current density grown by plasma-assisted MBE on 6H-SiC

High electron mobility transistors (HEMTs) were fabricated from AlGaN/-GaN layers grown by plasma-assisted molecular beam epitaxy on semi-insulating 6H-SiC substrates. Room-temperature Hall effect measurements yielded a polarization-induced 2DEG sheet charge of 1.3/spl middot/10/sup 13/ cm/sup -2/ and a low-field mobility of 1300 cm/sup 2//V/spl middot/s. Submicron gates were defined with electron beam lithography using an optimized two-layer resist scheme. HEMT devices repeatedly yielded drain current densities up to 1798 mA/mm, and a maximum transconductance of 193 mS/mm. This is the highest drain current density in any AlGaN-GaN HEMT structure delivering significant microwave power reported thus far. Small-signal testing of 50-/spl mu/m wide devices revealed a current gain cutoff frequency f/sub T/ of 52 GHz, and a maximum frequency of oscillation f/sub max/ of 109 GHz. Output power densities of 5 W/mm at 2 GHz, and 4.9 W/mm at 7 GHz were recorded from 200-/spl mu/m wide unpassivated HEMTs with a load-pull setup under optimum matching conditions in class A device operation.     

High-Q SAW filter and submicron process technology for timingextraction in high bit rate optical communications system

A new surface acoustic wave (SAW) filter configuration that consists of 3λ/8-wide meander-type electrodes and 3λ/8-wide excitation electrodes on ST-cut quartz was designed for use in a 2.5-Gb/s optical communications system. New submicron process techniques using the phase shifting method as well as several types of resist were investigated to fabricate this filter. It had an insertion loss of less than 14 dB and a Q of about 700, and satisfied all required system specifications over a temperature range from 0 to 60°C