Epitaxial lift-off GaAs HEMT's

An extensive study of epitaxial lift-off (ELO) Al_0.3Ga _0.7As/GaAs modulation doped heterostructure high electron mobility field-effect transistors (HEMT's) is presented. Effects of ELO on electron transport properties of two-dimensional electron gas at AlGaAs/GaAs interface are investigated. An ELO HEMT with 1.5 μm gate length had a maximum extrinsic transconductance g_m-max=125 mS/mm, a unity current gain cut-off frequency f_t=10.5 GHz, and a maximum frequency of oscillation f_max=12 GHz. Statistical distributions of maximum intrinsic transconductance of ELO HEMT's are presented and compared with their on-wafer counterparts. Stability of the ELO HEMT's has also been evaluated by continuous operation at room temperature under dc bias     

AlGaN/GaN/InGaN/GaN DH-HEMTs with an InGaN notch for enhanced carrier confinement

We report an AlGaN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) with high-mobility two-dimensional electron gas (2-DEG) and reduced buffer leakage. The device features a 3-nm thin In/sub x/Ga/sub 1-x/N(x=0.1) layer inserted into the conventional AlGaN/GaN HEMT structure. Assisted by the InGaN layers polarization field that is opposite to that in the AlGaN layer, an additional potential barrier is introduced between the 2-DEG channel and buffer, leading to enhanced carrier confinement and improved buffer isolation. For a sample grown on sapphire substrate with MOCVD-grown GaN buffer, a 2-DEG mobility of around 1300 cm/sup 2//V/spl middot/s and a sheet resistance of 420 /spl Omega//sq were obtained on this new DH-HEMT structure at room temperature. A peak transconductance of 230 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 14.5 GHz, and a peak power gain cutoff frequency (f/sub max/) of 45.4 GHz were achieved on a 1/spl times/100 /spl mu/m device. The off-state source-drain leakage current is as low as /spl sim/5 /spl mu/ A/mm at V/sub DS/=10 V. For the devices on sapphire substrate, maximum power density of 3.4 W/mm and PAE of 41% were obtained at 2 GHz.     

Broadband single- and double-balanced resistive HEMT monolithicmixers

A double-balanced (DB) 3-18 GHz and a single-balanced (SB) 2-16 GHz resistive HEMT monolithic mixer have been successfully developed. The DB mixer consists of a AlGaAs/InGaAs HEMT quad, an active LO balun, and two passive baluns for RF and IF. At 16 dBm LO power, this mixer achieves the conversion losses of 7.5-9 dB for 4-13 GHz RF and 7.5-11 dB for 3-18 GHz RF. The SB mixer consists of a pair of AlGaAs/InGaAs HEMT's, an active LO balun, a passive IF balun and a passive RF power divider. At 16 dBm LO power, this mixer achieves the conversion losses of 8-10 dB for 4-15 GHz RF and 8-11 dB for 2-16 GHz RF. The simulated conversion losses of both mixers are very much in agreement with the measured results. Also, the DB mixer achieves a third-order input intercept (IP₃) of +19.5 to +27.5 dBm for a 7-18 GHz RF and 1 GHz IF at a LO drive of 16 dBm while the SB mixer achieves an input IP ₃ of +20 to +28.5 dBm for 2 to 16 GHz RF and 1 GHz IF at a 16 dBm LO power. The bandwidth of the RF and LO frequencies are approximately 6:1 for the DB mixer and 8:1 for the SB mixer. The DB mixer of this work is believed to be the first reported DB resistive HEMT MMIC mixer covering such a broad bandwidth     

Optical mixing in epitaxial lift-off pseudomorphic HEMTs

In this letter, we present optical mixing in epitaxial lift-off (ELO) pseudomorphic HEMTs (PHEMTs) at difference frequencies in the microwave regime up to 22 GHz. The 3 μm gate length AlGaAs-InGaAs PHEMT's mere lifted off their host GaAs substrates and subsequently attached to quartz slides. It was observed that the ELO devices consistently resulted in stronger signals (~7 dB) than the non-ELO devices under frontside and backside illumination. This is attributed to improved optical coupling efficiency, a decrease in substrate leakage, and an illumination-induced back gating effect for the ELO films     

45 GHz active HEMT mixer

A low-noise 45 GHz mixer has been realised using a high electron mobility transistor (HEMT). This is the first reported active mixer above 30 GHz and the first reported HEMT mixer. The mixer exhibits 1.5 dB maximum gain at 4 dBm local oscillator (LO) power and 8.1 dB noise figure, including a 2.6 dB NF IF amplifier, at 2 dBm LO power.     

The Design of Low LO-Power 60-GHz CMOS Quadrature-Balanced Self-Switching Current-Mode Mixer

This letter describes the analysis and measurement of a complementary metal-oxide semiconductor (CMOS) quadrature-balanced current-mode mixer with a 90^deg branch-line hybrid coupler and self-switching current-mode devices. The proposed mixer, using 0.13 mum 1P8M CMOS technology, can downconvert a 60 GHz RF signal to a 2 GHz intermediate frequency (IF) signal, with a local-oscillator power of 0 dBm at 58 GHz. In the design, the mixer had a single-end conversion gain of 1 dB and an input-referred 1 dB compression point of 2 dBm. The LO-RF isolation of the mixer can achieve -37 dB while using 3 mA from a supply voltage of 1.2 V.     

宽中频CMOS下变频器单片

该文介绍了一种工作于毫米波频段的宽中频(IF)下变频器。该下变频器基于无源双平衡的设计架构,片上集成了射频(RF)和本振(LO)巴伦。为了优化无源下变频器的增益、带宽和隔离度性能,电路设计中引入了栅极感性化技术。测试结果表明,该下变频器的中频带宽覆盖0.5～12 GHz。在频率为30 GHz、幅度为4 dBm的LO信号驱动下,电路的变频增益为–8.5～–5.5 dB。当固定IF为0.5 GHz、LO幅度为4 dBm时,变频增益随25～45 GHz的RF信号在–7.9～–5.9 dB范围内变化,波动幅度为2 dB。LO-IF, LO-RF, RF-IF的隔离度测试结果分别优于42, 50, 43 dB。该下变频器芯片采用TSMC 90 nm CMOS工艺设计,芯片面积为0.4 mm2。     

A high-performance W-band uniplanar subharmonic mixer

A uniplanar subharmonic mixer has been implemented in coplanar waveguide (CPW) technology. The circuit is designed to operate at RF frequencies of 92-96 GHz, IF frequencies of 2-4 GHz, and LO frequencies of 45-46 GHz. Total circuit size excluding probe pads and transitions is less than 0.8 mm ×1.5 mm. The measured minimum single-sideband (SSB) conversion loss is 7.0 dB at an RF of 94 GHz, and represents state-of-the-art performance for a planar W-band subharmonic mixer. The mixer is broad-band with a SSB conversion loss of less than 10 dB over the 83-97-GHz measurement band. The measured LO-RF isolation is better than -40 dB for LO frequencies of 45-46 GHz. The double-sideband (DSB) noise temperature measured using the Y-factor method is 725 K at an LO frequency of 45.5 GHz and an IF frequency of 1.4 GHz. The measured data agrees well with the predicted performance using harmonic-balance analysis (HBA). Potential applications are millimeter-wave receivers for smart munition seekers and automotive-collision-avoidance radars     

Cryogenic cooling of mixers for millimeter and centimeter wavelengths

It is shown theoretically that cryogenically cooling a Schottky-barrier mixer only slightly increases the conversion loss while giving a considerable reduction in mixer noise. The d.c. bias and local oscillator drive must be appropriately scaled. Experimental results indicate that in conjunction with a cooled paramp IF amplifier, single-sideband (SSB) receiver noise temperatures of ~350 K at 85 GHz, and ~260 K at 33 GHz are presently obtainable-an improvement by a factor of 6 at 85 GHz and 4 at 33 GHz over current room-temperature mixer receivers. An unexplained source of noise within the diodes has been observed and if this can be eliminated a further factor of 2 improvement in noise temperature will be obtained.     

An experimental study of harmonic SIS mixing at 205-235 GHz

A 230-GHz subharmonically pumped waveguide mixer employing superconducting tunnel junctions has been developed. We present, in this paper, an experimental study of harmonic superconductor-insulator-superconductor (SIS) mixing at 230 GHz, focusing mainly on its noise behavior. The mixer has a double-tuned waveguide structure and employs an array of four 1.7-/spl mu/m/sup 2/ Nb-AlOx-Nb SIS junctions in series, with /spl omega/R/sub n/C/sub j//spl sim/3 at 230 GHz. Harmonic quantum mixing occurred over an experimental frequency range of 205-235 GHz (local oscillator: 112.5-117.5 GHz), exhibiting corresponding double sideband noise temperatures of lower than 150 K, with a lowest value of 75 K at /spl sim/230 GHz. The measured mixer noise is believed to be the lowest yet reported for a mixer using subharmonic-pump configuration at this frequency. A phenomenon that we attribute to the third harmonic SIS mixing has also been observed.     

An Active IF Balun for a Doubly Balanced Resistive Mixer

In this letter, we present a wideband active intermediate frequency (IF) balun for a doubly balanced resistive mixer implemented using a 0.5 mum GaAs pHEMT process. The 0.3 times 0.5 mm² IF balun was realized through a DC-coupled differential amplifier in order to extend IF frequency of the mixer to DC. The measured amplitude and phase imbalances were less than 1 dB and 5deg, respectively, from DC to 7 GHz. The output third order intercept (OIP3) and P1 dB of the IF balun were 18 dBm and 6 dBm, respectively at 1 GHz. The mixer with the IF balun is 1.7 times 1.8 mm² in size, has a conversion loss of 2 to 8 dB from 8 to 20 GHz RF frequency at a fixed IF of 1 kHz, which proves the mixer operates successfully at an IF frequency close to DC. The measured OIP3 were +10 to +15 dBm over the operating frequency with a DC power consumption of 370 mW.     

A 60-GHz uniplanar MMIC 4/spl times/ subharmonic mixer

A uniplanar GaAs monolithic microwave integrated circuit /spl times/4 subharmonic mixer (SHM) has been fabricated for 60-GHz-band applications using an antiparallel diode pair in finite ground coplanar (FGC) waveguide technology. This mixer is designed to operate at an RF of 58.5-60.5 GHz, an IF of 1.5-2.5 GHz, and an LO frequency of 14-14.5 GHz. FGC transmission-line structures used in the mixer implementation were fully characterized using full-wave electromagnetic simulations and on-wafer measurements. Of several mixer configurations tested, the best results show a maximum conversion loss of 13.2 dB over the specified frequency range with a minimum local-oscillator power of 3 dBm. The minimum upper sideband conversion loss is 11.3 dB at an RF of 58.5 GHz and an IF of 2.5 GHz. This represents excellent performance for a 4/spl times/ SHM operating at 60 GHz.     

180–425 GHz low noise SIS waveguide receivers employing tuned Nb/AIO x /Nb tunnel junctions

We report recent results on a 20% reduced height 270–425 GHz SIS waveguide receiver employing a 0.49 µm² Nb/AlO _x /Nb tunnel junction. A 50% operating bandwidth is achieved by using a RF compensated junction mounted in a two-tuner reduced height waveguide mixer block. The junction uses an “end-loaded” tuning stub with two quarter-wave transformer sections. We demonstrate that the receiver can be tuned to give 0–2 dB of conversion gain and 50–80% quantum efficiency over parts of it's operating range. The measured instantaneous bandwidth of the receiver is ≈ 25 GHz which ensures virtually perfect double sideband mixer response. Best noise temperatures are typically obtained with a mixer conversion loss of 0.5 to 1.5 dB giving uncorrected receiver and mixer noise temperatures of 50K and 42K respectively at 300 and 400 GHz. The measured double sideband receiver noise temperature is less than 100K from 270 GHz to 425 GHz with a best value of 48K at 376 GHz, within a factor of five of the quantum limit. The 270–425 GHz receiver has a full 1 GHz IF passband and has been successfully installed at the Caltech Submillimeter Observatory in Hawaii. Preliminary tests of a similar junction design in a full height 230 GHz mixer block indicate large conversion gain and receiver noise temperatures below 50K DSB from 200–300 GHz. Best operation is again achieved with the mixer tuned for 0.5–1.5 dB conversion loss which at 258 GHz resulted in receiver and mixer noise temperature of 34K and 27K respectively.     

Investigation of a heterodyne receiver with open structure mixer at 324 GHz and 693 GHz

The performance of a submillimeter heterodyne receiver using an HCOOH laser local oscillator and an open structure mixer with a Schottky barrier diode has been optimized for 693 GHz. Working at room temperature a single sideband (SSB) system noise temperature of 7,300 K, a mixer noise temperature of 6,100 K and a conversion loss of 12 dB has been achieved. The same receiver system has been investigated at 324 GHz using an HCOOD laser local oscillator yielding a noise temperature of 3,100 K (SSB), a mixer noise temperature of 2,400 K (SSB) and a conversion loss of 10 dB (SSB). An acousto-optical spectrometer has also been constructed, with 1024 channels and a channel-bandwidth of 250 kHz. The system NEP per channel was 2.5×10^?17 W/Hz^1/2 at 324 GHz and 5.0×10^?17 W/Hz^1/2 at 693 GHz.     

Cryogenic Millimeter-Wave Receiver Using Molecular Beam Epitaxy Diodes

A millimeter-wave cryogenic receiver has been built for the 60-90-GHz frequency band using GaAs mixer diodes prepared by molecuIar beam epitaxy (MBE). The diodes are mounted in a reduced-height image rejecting waveguide mixer which is followed by a cooled parametric amplifier at 4.5-5.0 GHz. At a temperature of 18 K the receiver has a total single-sideband (SSB) system temperature of 312 K at a frequency of 81 GHz. This is the lowest system temperature ever reported for a resistive mixer receiver. The low-noise operation of the mixer is seen to be a result of 1) the short-circuiting of the noise entering the image port and 2) an MBE mixer diode with a noise temperature which is consistent with the theoretical shot noise from the junction and the thermal noise from the series resistance.     

Low conversion-loss fourth subharmonic mixers incorporating CMRC for millimeter-wave applications

Low conversion-loss millimeter-wave fourth subharmonic (SH) mixer designs are proposed in this paper. A millimeter-wave (35 GHz) fourth SH mixer with four open/shorted stubs is designed and measured. The conversion loss is less than 15 dB within a 2.4-GHz bandwidth. The minimum loss is 11.5 dB at the center frequency. By replacing two of the shunt stubs with a dual-frequency in-line stub consisting of newly developed compact microstrip resonating cells (CMRCs), the performance of the SH mixer is improved significantly. At 35 GHz, the conversion loss of this new fourth SH mixer is as low as 6.1 dB with a 3-dB bandwidth of 6 GHz. The conversion loss in the whole Ka-band (26.5-40 GHz) is less than 16 dB. The proposed fourth SH mixer incorporating with CMRCs provides a low-cost high-performance solution for RF subsystem design.     

A Low-Voltage Broadband Feedforward-Linearized BJT Mixer

A low-voltage, feedforward-linearized bipolar mixer realizes an input$hboxIP_3$of$+$14.3 dBm and an input$hboxIP_2$of$+$54.5 dBm at 2.4 GHz. Conversion (power) gain over the 1–6GHz RF input range is 12.4$,pm,$0.35 dB, while the input$hboxIP_3$is 13.6$,pm,$1.8dBm over the same frequency range. The broadband mixer's RF input impedance varies from 60.3-j7.1 at 2.4 GHz to 57.4-j16.6$~Omega$at 5.8GHz. Measured SSB (50$Omega$) noise figure is 18.6 dB at 2.4 GHz. No on-chip inductors are used in the design, and the 0.14$hbox mm^2$(active area) mixer dissipates 7.2 mW from a (minimum) 1.2 V supply.     

A highly linear double balanced Schottky diode S-band mixer

A high-level double balanced SiC Schottky diode mixer in SiC monolithic microwave integrated circuit (MMIC) technology has been designed, processed and characterized. The mixer is a single ended in- and output circuit with coupled transformers as baluns to enable a compact design, resulting in a total area of 2.2/spl times/2.2mm/sup 2/. The mixer has a maximum IIP/sub 3/ of 38dBm and IIP/sub 2/ of 58dBm at 3.3GHz, and a typical P/sub 1 dB/ of 23dBm in the S-band. The minimum conversion loss was 12dBm at 2.4GHz. The high power operation of the mixer shows that SiC MMIC can perform well in high microwave radiation environments.     

Al0.3Ga0.7As/GaAs HEMT's under opticalillumination

Theoretical and experimental work for the DC and RF performance of depletion mode Al_0.3Ga_0.7As/GaAs HEMTs under optical illumination is presented. The photoconductive effect increasing the 2-DEG channel electron concentration and photovoltaic effect in the gate junction are considered. Optical tuning of a 2 GHz HEMT oscillator and optical control of the gain of a 2 to 6 GHz HEMT amplifier are presented and potential applications are described     

SEMICONDUCTOR-SUPERLATTICE FREQUENCY MIXER FOR DETECTION OF SUBMILLIMETER WAVES

We report on a GaAs/AlAs superlattice frequency mixer for detection of submillimeter waves. The mixer is based on the nonlinear miniband transport giving rise to domains excited under the action of a microwave field. We designed the mixer for broadband operation (300–600 GHz). For studying basic properties, we investigated the mixer as a harmonic mixer in 15^th order to detect radiation at a radio frequency (RF) near 300 GHz using local oscillator (LO) radiation of a frequency near 20 GHz. We reached a noise equivalent power (NEP) of about 10 fW/Hz. We also show that the use of the superlattice mixer together with a superlattice frequency multiplier allows to realize a superlattice-based free-space transmission line for submillimeter waves.