Dual-gate m.e.s.f.e.t. self-oscillating X-band mixers

GaAs dual-gate m.e.s.f.e.t.s have been successfully used as self-oscillating down-convertors in X-band. A single device replaces the preamplifier, mixer and local oscillator. The best conversion gain achieved by mixing from 10 GHz down to 1 GHz was 12 dB. The input (gate 1) to output (drain) port isolation amounted to 16 dB. Slug-tuner and `disc?-resonator circuits were tested and showed comparable gain and noise performance. Best d.s.b. noise figures of 5.5 dB could be realised at an i.f. of 1 GHz with an associated conversion gain of 4 dB.     

GaAs f.e.t. mixer operation with high intermediate frequencies

GaAs f.e.t. mixer operation is investigated at 6 GHz when the intermediate frequency is around 1 GHz. A 3 dB improvement in noise figure is measured, compared with 30 MHz i.f. operation. Other characteristics, such as conversion gain and dynamic range, are similar. Broadband operation is also investigated. With 0.5 ?m gate device, on s.s.b. noise figure of 5.6 dB is achieved with a conversion gain of 10 dB.     

Performance of selenium-ion-implanted GaAs f.e.t.s

Selenium-ion-implanted GaAs f.e.t.s have given minimum noise figures as low as 3·4 dB and maximum available gains of at least 10 dB at 10 GHz. The devices do not appear to suffer from short-term drift problems, and have greater device-characteristic uniformity and reproducibility than epitaxial f.e.t.s.     

Performance of self-oscillating GaAs m.e.s.f.e.t. mixers at X-band

A new mode of m.e.s.f.e.t. operation, the self-oscillating mixer is reported. Conversion gains of up to 2 dB at 10 GHz and noise figures as good as 15 dB have been demonstrated by using a simple circuit.     

Intentional side etching to achieve low-noise GaAs f.e.t.

A very-low-noise 0.5 ?m-gate GaAs f.e.t. is realised by using intentional side etching of an Au/Ti double layer as the Schottky-gate metal. At 12 GHz, the minimum noise figure is 2.1 dB, with 7.6 dB associated gain at a bias of VD = 4 V, ID= 10 mA. Maximum stable gain is 14 dB at VD = 4 V, ID = 30 mA.     

High-power pulsed and c.w. silicon double-drift IMPATT amplifiers at X-band

The letter presents some reflection-amplifier results for Si double-drift pulsed and c.w. IMPATTs. Peak r.f. powers of up to 11.6 and 16.5 W with instantaneous (?1 dB) bandwidths ~20% at gains >6 dB have been obtained at 10 GHz with 1- and 2-diode combinations when bias modulated with a pulsewidth of 4 ?s and p.r.f. of 1 kHz. A 2-diode c.w. combination has given a power of 7 W (c.w.) at 10.7 GHz with a gain of 6.5 dB and instantaneous (?1 dB) bandwidth of 400 MHz.     

170 GHz和340 GHz CSMRs滤波器选频网络研究

为了实现倍频器多谐波输出,满足系统多频率需求,同时减少成本,增加系统集成度,引入了改进紧凑型悬置微带谐振单元（Compact Suspended Microstrip Resonators（CSMRs））滤波器,主要研究并实现了170 GHz和340 GHz双频段分别输出。仿真中分别设计170 GHz和340 GHz探针,引入CSMRs低通滤波器增加170 GHz对高频段的隔离,减小波导高度,提高WR.2.8波导截止频率,增加对300 GHz以下频段抑制,为了测试其输出特性和网络损耗,设计170~340 GHz背靠背模块。仿真结果为低通CSMRs滤波器满足在20~180 GHz通带内反射系数小于-18 dB,在266~520 GHz阻带内抑制度大于20 dB,背靠背结构仿真170 GHz与340 GHz频段反射系数均小于-15 dB,端口隔离大于30 dB,表现出良好的选频特性。测试结果表明:在170 GHz端口通带为150~185 GHz,反射系数小于-10 dB,损耗大于1.2 dB;在340 GHz端口,通带为306~355 GHz,反射系数小于-10 dB,损耗2 dB,两端口隔离度大于10 dB,最好60 dB。     

数字硅MOSFET微波特性的研究

利用国内先进的 0 .6μm数字 Si-MOS工艺 ,设计了射频 MOSFET,并研究了其 DC和微波特性 :I-V曲线、S参数、噪声参数和输出功率。研究发现 ,数字电路用 Si MOSFET的频率响应较高 :频率为 1 GHz时功率增益可达 1 0 d B,2 GHz时为 8d B,4GHz时为 5 d B。 1 .8GHz时 ,1分贝压缩输出功率 1 2 .8d Bm,饱和输出功率可达 1 8d Bm,且最小噪声系数为 3 .5 d B。用提取的参数设计并研制了微波 Si MOSFET低噪声放大器 ,以验证MOS器件的微波性能。此放大器由两级级联而成 ,单电源供电 ,输入输出电容隔直。在频率 1 .7～ 2 .2 GHz的范围内 ,测得放大器增益 1 5± 0 .5 d B,噪声系数 N F<3 .8d B,1分贝压缩输出功率 1 2 d Bm;在频率 1 .5～ 2 .5 GHz的范围内 ,放大器增益大于 1 3 d B。     

热处理对羰基铁粉磁性能和吸波性能的影响

为了改善羰基铁粉的微观结构和吸波性能,对羰基铁粉吸收剂在氮气氛下进行了热处理,热处理温度为300℃,热处理时间为30 h,研究了羰基铁粉的磁性能和在2～18 GHz的吸波性能。以热处理前后羰基铁粉作为吸收剂制备了单层吸波涂层,涂层的厚度为1.2 mm时,热处理羰基铁粉吸波涂层在10.2～15.4 GHz反射率R小于-10 dB,反射率小于-10 dB的频宽为5.2 GHz,反射率小于-5 dB的频宽为10 GHz;最大吸收峰在12.8 GHz,反射率R为-22.68 dB。磁性能研究表明,热处理后随着矫顽力的增加,在2～18 GHz羰基铁粉的微波吸收峰向高频移动,而且吸收峰变宽,吸波性能得到大幅提高。     

A coplanar X-band AlGaN/GaN power amplifier MMIC on s.i. SiC substrate

This work presents a two-stage high-power amplifier monolithic microwave integrated circuit (MMIC) operating between 9 GHz and 11 GHz based on a fully integrated AlGaN/GaN high electron mobility transistor (HEMT) technology on s.i. SiC substrate and is suitable for radar applications. The MMIC device with a chip size of 4.5/spl times/3 mm/sup 2/ yields a linear gain of 20 dB and a maximum pulsed saturated output power of 13.4 W at 10 GHz equivalent to 3.3 W/mm at V/sub DS/=35V, 10% duty cycle, and a gain compression level of 5 dB. Further, dc reliability data are given for the MMIC HEMT technology.     

K-band f.e.t. amplifiers

Single-stage f.e.t. amplifiers operating in K-band have been constructed using the Varian VSX 9305 0.5 ?m-gate GaAs f.e.t. An amplifier gain of 9±1 dB was obtained over the frequency band 18.5?20.5 GHz and gain of 8±1 dB was observed from 23.0 to 26.0 GHz. An amplifier noise figure of 5.6 dB was measured at 24 GHz.     

Reflectivity of absorbers in 100-200 GHz range

Different types (pyramidal, convoluted, wedge, flat) of absorber panel made by several manufacturers have been measured at 107 and 183 GHz. These measurements revealed a rapid degradation of the quality of absorbers from 107 to 183 GHz: reflectivity increased nearly 10 dB. The best absorbers have reflectivities below -40 dB at 107 GHz and about -35 dB at 183 GHz.<>     

X and Ku band GaAs m.e.s.f.e.t.

A GaAs Schottky-barrier f.e.t. (m.e.s.f.e.t.) with a 1 ?m gate has been built, which is suitable for X band and Ku band applications. The unilateral power gain over the X band is above 9 dB and the noise figure is only 5 dB at 10 GHz.     

X-band performance of GaAs power f.e.t.s

The results of X-band measurements on GaAs power f.e.t.s are reported. These devices are fabricated with a simple planar process. Devices with output powers of 1 W or more at 9 GHz with 4 dB gain have been fabricated from more than a dozen slices. The highest output powers observed with 4 dB gain are 1.78 W at 9 GHz and 2.5 W at 8 GHz. Devices have been operated with 46% power-added efficiency at 8 GHz.     

100K uncooled GaAs m.e.s.f.e.t. amplifier as paramp replacement

The characterisation, design and realisation of a low noise GaAs m.e.s.f.e.t. amplifier to replace a narrow band parametric amplifier at 1.7 GHz is described. Special measurement and analytical techniques are necessary owing to the high reflection coefficients and conditional stability of the transistor, as well as the very low noise figures being measured. A single stage amplifier is realised with a noise figure of 1.25 dB and 13.5 dB associated gain at 1.7 GHz.     

Design of Dual‐Band MIMO Antenna with High Isolation for WLAN Mobile Terminal

In this paper, we propose a dual‐band multiple‐input multiple‐output (MIMO) antenna with high isolation for WLAN applications (2.45 GHz and 5.2 GHz). The proposed antenna is composed of a mobile communication terminal board, eight radiators, a coaxial feed line, and slots for isolation. The measured ?10 dB impedance bandwidths are 10.1% (2.35 GHz to 2.6 GHz) and 3.85% (5.1 GHz to 5.3 GHz) at each frequency band. The proposed four‐element MIMO antenna has an isolation of better than 35 dB at 2.45 GHz and 45 dB at 5.2 GHz between each element. The antenna gain is 3.2 dBi at 2.45 GHz and 4.2 dBi at 5.2 GHz.     

A low phase shift attenuator

A PIN diode attenuator with an average of 0.25°/dB phaseshift between 2.5 GHz and 5.3 GHz has been modelled and constructed. In particular the attenuator has similar phase at 0 dB and 12 dB of attenuation to within 0.5° over most of the band. The input match is better than 10 dB over the attenuation range of 0 to 10 dB     

GaAs f.e.t.s with silicon-implanted channels

Field-effect transistors with channel doping profiles fabricated by the implantation of silicon ions into high-resistivity vapour phase epitaxial GaAs have given noise figures of 2.9 dB with an associated gain of approximately 5 dB at 10 GHz. Similar measurements on F.E.T.S fabricated in an identical manner, except for the channel fabrication, where silicon ions were implanted directly into a Cr-doped semi-insulating GaAs substrate, have resulted in nose figures typically 1 dB higher.     

High-isolation CPW MEMS shunt switches. 1. Modeling

This paper, the first of two parts, presents an electromagnetic model for membrane microelectromechanical systems (MEMS) shunt switches for microwave/millimeter-wave applications. The up-state capacitance can be accurately modeled using three-dimensional static solvers, and full-wave solvers are used to predict the current distribution and inductance of the switch. The loss in the up-state position is equivalent to the coplanar waveguide line loss and is 0.01-0.02 dB at 10-30 GHz for a 2-μm-thick Au MEMS shunt switch. It is seen that the capacitance, inductance, and series resistance can be accurately extracted from DC-40 GHz S-parameter measurements. It is also shown that dramatic increase in the down-state isolation (20⁺ dB) can be achieved with the choice of the correct LC series resonant frequency of the switch. In part 2 of this paper, the equivalent capacitor-inductor-resistor model is used in the design of tuned high isolation switches at 10 and 30 GHz     

GaAs power m.e.s.f.e.t.s. with a graded recess structure

A new recess structure device was developed to improve the field distrubution and therfore the performance of GaAs power m.e.s.f.e.t.s. The linear gain and the output power were improved by 1?2 dB for this structure. The highest output powers obtained are 15 W with 4 dB associated gain at 6 GHz, and 4.3 W with 3 dB associated gain at 11 GHz.