Low-loss, high-voltage 6H-SiC epitaxial p-i-n diode

The p-i-n diodes were fabricated using 31 /spl mu/m thick n/sup -/- and p-type 6H-SiC epilayers grown by horizontal cold-wall chemical vapor deposition (CVD) with nitrogen and aluminum doping, respectively. The diode exhibited a very high breakdown voltage of 4.2 kV with a low on-resistance of 4.6 m/spl Omega/cm/sup 2/. This on-resistance is lower (by a factor of five) than that of a Si p-i-n diode with a similar breakdown voltage. The leakage current density was substantially lower even at high temperatures. The fabricated SiC p-i-n diode showed fast switching with a turn-off time of 0.18 /spl mu/s at 300 K. The carrier lifetime was estimated to be 0.64 /spl mu/s at 300 K, and more than 5.20 /spl mu/s at 500 K. Various characteristics of SiC p-i-n diodes which have an advantage of lower power dissipation owing to conductivity modulation were investigated.     

Photo-injection p-i-n diode switch for high-power RF switching

The high RF power-switching properties of the photo-injection p-i-n switch (PIPINS), an optically controlled RF switch, are investigated. Proper functioning of a PIPINS as a low insertion-loss RF switch requires that it operates as a photoconductor, where the photo-injected charge is much greater than the RF sweep out charge. Insertion loss using 650-mW optical power was <0.4 dB at RF (VHF-UHF) power in excess of 200 W, and devices successfully standoff 200-W incident RF power with the series isolation being determined by the device capacitance (e.g., 225 fF). PIPINS hot-switching measurements are reported for the first time, with output RF power up to 180 W at low duty cycle, rise times of 1 ps, and fall times for a series shunt switch of ≈2.5 μs. The RF power for hot switching a PIPINS is limited by a latch-on effect, which is dependent on a variety of parameters, including duty cycle and repetition period, consistent with thermally generated carriers contributing to the latch-on effect. The switching properties of PIPINS make them a candidate for high RF power applications such as reconfigurable antennas, where electromagnetic isolation of the switch and control lines are critical     

High-performance high-power analog phase shifter

A high average power, high figure of merit, X-band, ferrite loaded waveguide phase shifter has been developed. A zinc-doped magnesium manganese ferrite (4πMs=3000 gauss), in combination with a reduced cross-section rectangular waveguide, was used to achieve a figure of merit of 1000 degrees per decibel, which is better than any previously reported mode-free configuration.     

波导二极管移相器的设计

介绍了波导二极管移相器的设计原理和实现方法。运用矩形波导的传输理论,将加载线型移相单元插入矩形波导内,对波导内的24个加载线型移相单元进行调配组合实现五位地址数码控制移相器。实测结果表明该移相器移相范围大、插入损耗低、输入驻波小、转换时间快、移相精度高及耐高功率性好。     

Single PIN diode X-band phase shifter

A new design of microstrip phase shifter is described which uses only one PIN diode per bit of phase shift. Results are presented for a representative device which show good agreement between experimental and theoretical results at X-band. In particular, the device has been shown to yield a useful 20% bandwidth centred on 10 GHz.     

Low-loss low-confinement GaAs-AlGaAs DQW laser diode with opticaltrap layer for high-power operation

A low-confinement asymmetric GaAs-AlGaAs double-quantum-well molecular-beam-epitaxy grown laser diode structure with optical trap layer is characterized, The value of the internal absorption coefficient is as low as 1.4 cm^-1, while keeping the series resistance at values comparable cm with symmetrical quantum-well gradient index structures in the same material system. Uncoated devices show COD values of 35 mW/μm. If coated, this should scale to about 90 mW/μm. The threshold current density is about 1000 A/cm² for 2-mm-long devices and a considerable part of it is probably due to recombination in the optical trap layer. Fundamental mode operation is limited to 120-180 mW for 6.5-μm-wide ridge waveguide uncoated devices and to 200-300 mW for 13.5-μm-wide ones, because of thermal waveguiding effects. These values are measured under pulsed conditions, 10 μs/l ms     

A SiGe MMIC 6-bit PIN diode phase shifter

A 6-bit PIN diode phase shifter has been successfully demonstrated at microwave frequencies in a SiGe bipolar technology. A post-silicon polymer dielectric interconnect technology is implemented to achieve low loss microstrip structures on the silicon substrate. The monolithic microwave integrated circuit exhibits flat phase shift, low VSWR, and low insertion loss variation, over the 7- to 11-GHz band. This phase shifter demonstrates the feasibility of integrating SiGe technology into microwave systems.     

A p-i-n thermo-photovoltaic diode

The analysis, fabrication, and operation of a p-in photovoltaic cell that is suitable for use at the very high illumination intensities, which are encountered in a thermo-photovoltaic system, are presented. The device performance has been measured under pulse conditions to 790 W/cm²of incident radiation. The efficiency of operation is limited at very high illumination levels by an increase in the reflection coefficient. Open circuit voltages of 0.42 volts and short circuit currents in excess of 40 A/cm²of illuminated surface have been observed for germanium devices. Operating efficiencies at various incident light intensities are reported. The analysis includes an estimate of the effect of the electric field that occurs in the intrinsic region.     

A high-power PWM quadrature booster phase shifter based on amultimodule AC controller

Pulse-width-modulated (PWM) phase shifters allow the smooth control of power flow in a transmission line. This paper analyzes a PWM quadrature booster phase shifter based on a multimodule AC controller structure to attain high voltage levels and improve the harmonic spectrum. The modules are based on a three-phase PWM AC controller topology that employs only four force-commutated switches and is controlled by duty-cycle variation. The PWM technique is carrier based and the individual modules are gated through phase-shifted triangular carriers. As a result, harmonic cancellation takes place in the input current and output voltage. Low-order harmonics are therefore eliminated and the amplitude of remaining components reduced. An additional operating mode with negligible harmonic generation and step-like control is identified. The feasibility and advantages of the proposed phase shifter are demonstrated by means of a power system simulator     

Laser-activated p-i-n diode switch for RF application

Results obtained utilizing an optically activated RF switch in the 2-30-MHz range demonstrate the advantages in optically controlled high-power switches from HF to millimeter wave. Testing of a 0.25-mm-thick p-i-n device activated with 116-W peak optical power from a two-dimensional laser array in a 50-Ω system shows isolation between 20.8 and 49 dB, and an average insertion loss of 0.38 dB when measured between 2.5 and 30 MHz     

大功率激光二极管阵列光束整形技术

大功率激光二极管阵列相比于同等功率的激光器有着优越的高性能和可靠性,在军事、工业、医学、航空航天等领域有着广阔的应用前景.具体应用中,大功率激光二极管阵列的光束整形技术扮演着一个重要角色.丈中提出折反光束整形系统,把线光束整形为方形或者圆形,利用此系统把20mm线光束整形为5mm×5 mm的方形光斑,软件模拟结果证明设计方法的正确性和可行性.     

TRAPATT oscillations in a p-i-n avalanche diode

The characteristics of TRAPATT oscillations in a p-in diode are discussed and an approximate semi-analytical solution for the diode voltage waveform is derived when the diode current is a square wave. It is shown that a traveling avalanche zone is not necessary to generate a dense "trapped" plasma and that the boundary conditions prevent the trapped plasma from completely filling the depletion layer. Typical voltage waveforms and corresponding diode power, efficiency, and impedance at the fundamental and higher harmonics are presented. When the diode current is a square wave the diode does not necessarily exhibit a negative resistance at all higher harmonics. A computer program for TRAPATT oscillations in a p-i-n diode is described. Its running time is two or three orders of magnitude less than more exact time domain computer analyses. Typical results of diode power, dc to RF conversion efficiency, and required circuit impedances are presented for several different current waveforms which are composed of up to the seventh harmonic of a square wave and the first two harmonics of a half-wave sine wave. It is shown that high-efficiency oscillations are possible with diode currents composed of only the fundamental and one harmonic.     

Control circuit for ferrite phase shifter

A circuit is described that uses a digitally controlled variable-pulse-duration generator to determine the phase setting of a 9 GHz ferrite phase shifter to an accuracy of within ±4°. The circuit incorporates temperature compensation, test facilities and phase information stored in a read-only memory.     

p-i-n diode reverse-bias switching via inductive discharging

Reverse switching of high-power p-i-n diodes can be achieved by inductive discharge. In this type of switching there is a direct interaction between the energy-storing element and the p-i-n diodes, and the current and voltage waveforms follow somewhat different equations to those of a conventional driving circuit.     

L-band high power silicon p-i-n diode switch

An extremely high power silicon p-i-n diode switch was developed for operation over the 1255- to 1385-MHz frequency range. It was successfully tested at 4-MW peak power with 100-µs pulsewidth. and 2.5-MW peak and 100-kW average power with 200-µs pulsewidth in a balanced duplexer configuration.     

Woodpile EBG phase shifter

A phase shifter in an alumina woodpile electromagnetic bandgap (EBG) defect waveguide that operates at microwave frequencies is demonstrated. The phase shift is introduced by sequentially adding low dielectric constant rods to the voids directly above the defect waveguide. The addition of the extra rods creates selected phase delay without significantly affecting the transmission performance of the woodpile waveguide. Measured and computed results in Ku-band are presented to confirm the performance of the device     

Microbend fiber-optic phase shifter

The use of spatially periodic microbend transducers to produce phase shift in single-mode fibers has been investigaed. Phase shift of32deg/mum²of transducer displacement per centimeter of trans-3.7deg/mum². cm for a 1023-μm peroid. Phase shifts as large as 560°/cm of transducer length were obtained with the shorter period transducer. These results are compared with predictions based on coupled-mode theory.     

Monolithic surface-acoustic-wave phase shifter

A monolithic surface-acoustic-wave phase shifter is described. The device consists of a distributed Schottky-barrier varactor junction capable of varying the electrical boundary conditions seen by a surface acoustic wave propagating on a piezoelectric medium. Almost 180° of phase shift is achieved in 55 acoustic wavelengths of interaction region at 54 MHz.     

Laser diode high-power picosecond pulses

A Finnish research group from the University of Oulu has developed a new type of laser diode structure, which allows high-power picosecond optical pulses to be obtained as a result of the direct current pumping.This is a short news story only. Visit www.three-fives.com for the latest advanced semiconductor industry news.