Schottky Diode Mixer Research Articles

Characteristics of GaAs Schottky Barrier Diode in Short Wavelength Far Infrared Region and the Application

The responsivity of a room-temperature GaAs Schottky barrier diode (SBD) mixer for 2.5 THz has been measured by using 14 far infrared laser lines in the frequency range of 1.6-6.3 THz. The SBD mixer has been detectable up to 6.3 THz. We have succeeded in the detection of two-color beat signals of simultaneously oscillated 5.2- and 6.3-THz CH3OD lasers by using the SBD mixer. As the application, it has been verified that the SBD mixer has been usable for beat frequency stabilization of the 5.2- and 6.3-THz CH3OD lasers of a two-color interferometer for fusion plasma diagnostics.

A Low VSWR 2SB Schottky Receiver

A novel high performance waveguide integrated sideband separating (2SB) Schottky receiver operating in the 320-360 GHz band is presented. The unique receiver design is based on a core of two subharmonic Schottky diode mixers with embedded LNA's with a minimum noise figure of 1.8 dB, fed by LO and RF quadrature hybrids. At room temperature, a typical receiver SSB noise temperature of 3000 K is measured over most of the band reaching a minimum of 2700 K, with only 4 mW of LO power. The sideband ratio (SBR) is typically below 15 dB over the whole band and the measured LO input return loss is typically below 15 dB broadband. High performance sideband separating Schottky receivers can now for the first time be considered for submillimeter wave systems enabling new types of instrument concepts.

Towards THz integrated photonics

The demonstration of an integrated terahertz transceiver featuring a quantum cascade laser and a Schottky diode mixer promises new applications for compact and convenient terahertz photonic instrumentation.

Terahertz inverse synthetic aperture radar (ISAR) imaging with a quantum cascade laser transmitter

A coherent transceiver using a THz quantum cascade (TQCL) laser as the transmitter and an optically pumped molecular laser as the local oscillator has been used, with a pair of Schottky diode mixers in the receiver and reference channels, to acquire high-resolution images of fully illuminated targets, including scale models and concealed objects. Phase stability of the received signal, sufficient to allow coherent image processing of the rotating target (in azimuth and elevation), was obtained by frequency-locking the TQCL to the free-running, highly stable optically pumped molecular laser. While the range to the target was limited by the available TQCL power (several hundred microwatts) and reasonably strong indoor atmospheric attenuation at 2.408 THz, the coherence length of the TQCL transmitter will allow coherent imaging over distances up to several hundred meters. Image data obtained with the system is presented.

Analysis on high frequency performance of THz GaAs Schottky mixer diode

In the THz frequency range,several new high effects will restrict diode high-frequency performance. With the thermionic emission theory and the tunnel theory,the high-frequency performance of epitaxial Schottky diodes is re-evaluated and the structure parameters are optimized with using the cut-off frequency as a figure of merit. The results show that when the operation frequency is higher than the plasma frequency,the diode is equivalent to a capacitance with losing the frequency mixing performance. With the increase of frequency,increasing the doping density of substrate can reduce the substrate plasma resonance effect. The plasma resonance frequency of epitaxial layer is an important factor but transit time effect must be considered. The higher operation frequency can be obtained through reducing the anode diameter and the epilayer thickness,and increasing the epilayer doping density. The results have an important reference value in developing the room temperature THz mixing diodes.

Spectral behavior of a terahertz quantum-cascade laser

In this paper, the spectral behavior of two terahertz (THz) quantum cascade lasers (QCLs) operating both pulsed and cw is characterized using a heterodyne technique. Both lasers emitting around 2.5 THz are combined onto a whisker contact Schottky diode mixer mounted in a corner cube reflector. The resulting difference frequency beatnote is recorded in both the time and frequency domain. From the frequency domain data, we measure the effective laser linewidth and the tuning rates as a function of both temperature and injection current and show that the current tuning behavior cannot be explained by temperature tuning mechanisms alone. From the time domain data, we characterize the intrapulse frequency tuning behavior, which limits the effective linewidth to approximately 5 MHz.

300 GHz transmission system

A 300 GHz transmission system, designed for terahertz communication channel modelling and propagation studies, is introduced. It consists of an autarkic transmitter and detector units based on Schottky diode mixer technology. The system performance is characterised with regard to link budget and noise. For demonstration, analogue video signals have been transmitted over distances of up to 22 m.

Terahertz local oscillator for the Microwave Limb Sounder on the Aura satellite

The Microwave Limb Sounder on the Aura satellite has a radiometer at 2.5 THz to perform global mapping of OH in the atmosphere. The OH radiometer utilizes two Schottky-diode mixers pumped by an optically pumped THz gas laser local oscillator. The laser was first turned on in space on July 22, 2004, and has performed without issue for more than 30 months. The specifications, design, and modeling of this 2.5 THz laser local oscillator are presented here, along with some of the important design validation and test results.

Advanced Microwave/Millimeter-Wave Imaging Technology

Millimeter wave technology advances have made possible active and passive millimeter wave imaging for av ariety of applications including advanced plasma diagnostics, radio astronomy, atmospheric radiometry, concealed weapon detection, all-weather aircraft landing, contraband goods detection, harbor navigation/surveillance in fog, highway traffi cm onitoring in fog, helicopter and automotive collision avoidance in fog, and environmental remote sensing data associated with weather, pollution, soil moisture, oil spill detection, and monitoring of forest fires, to name but a few. The primary focus of this paper is on technology advances which have made possible advanced imaging and visualization of magnetohydrodynamic (MHD) fluctuations and microturbulence in fusion plasmas. Topics of particular emphasis include frequency selective surfaces, planar Schottky diode mixer arrays, electronically controlled beam shaping/steering arrays, and high power millimeter wave local oscillator and probe sources. c

AN UNCOOLED VERY LOW NOISE SCHOTTKY DIODE RECEIVER FRONT-END FOR MIDDLE ATMOSPHERIC OZONE AND CARBON MONOXIDE MEASUREMENTS

The paper describes an uncooled front-end of the Schottky diode receiver system, which may be applied for observations of middle atmospheric ozone and carbon monoxide thermal emission lines at frequencies 110.8 GHz and 115.3 GHz, respectively. The mixer of the front-end has utilized high-quality Schottky diodes that allowed us to reduce the mixer conversion loss. The combination of the mixer and an ultra-low-noise IF amplifier in the one integrated unit has resulted in double-sideband (DSB) receiver noise temperature of 260 K at a local oscillator (LO) frequency of 113.05 GHz in the instantaneous IF band from 1.7 to 2.7 GHz. This is the lowest noise temperature ever reported for an uncooled ozone receiver system with Schottky diode mixers.

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.

A Very Low-Noise Integrated 3MM-Wave Schottky Diode Mixer and PHEMT IF Amplifier

An integrated 3mm-wave Schottky diode mixer and pseudomorphic high-electron-mobility transistor (PHEMT) IF amplifier with record noise performance at room temperature is described. The design has shown the room-temperature double-sideband (DSB) receiver noise temperature TRDSB of 190 K at 100 GHz due to a very low conversion loss in the full-height waveguide mixer and an ultra-low noise of the PHEMT IF amplifier. The receiver noise temperature has been reduced by a factor of 1.5 in comparison with the best previously reported 3mm-wave Schottky diode mixer receiver.

High Doping Density Schottky Diodes in the 3MM Wavelength Cryogenic Heterodyne Receiver

The paper describes a 3mm cryogenic mixer receiver using high doping density (“room-temperature”) Schottky diodes. The measured equivalent noise temperature Teq of the diodes is 109 K at 20 K, which is much higher than the Teq of the low doping density (“cryogenic”) diodes. In spite of this, the double-sideband (DSB) noise temperature of the cryogenic receiver developed is 55 K at 110 GHz, owing to the low conversion loss of the mixer and ultra-low noise of the PHEMT IF amplifier. This is the lowest noise temperature ever reported for a Schottky diode mixer receiver. The results obtained are useful for the development of submm receivers in which high doping density Schottky diodes are used.

Integrated silicon Schottky mixer diodes with cutoff frequencies above 1 THz

In this paper, fully monolithic integrated Schottky diodes on a high-resistivity (HR) silicon substrate with cutoff frequencies above 1 THz are presented. As HR silicon substrate, a common float-zone substrate was used. The necessity of an optimized layer design will be discussed. As it will be shown, cutoff frequencies above 1 THz are possible even for large area diodes with an optimized layer design, which provides the so-called MOTT operation. The demands for the layer design to realize MOTT operation and the resulting advantages for the component will be discussed in detail. The used fabrication process, which combines two separate standard processes, is explained briefly. The results of the electrical measurements and the achieved cutoff frequency will be summarized. To demonstrate a monolithic integration, the presented Schottky diodes have been manufactured in a process wherein RF microelectromechanical systems switches have been successfully produced. As a key application, a subharmonic mixer, with a 24-GHz RF signal and a 12-GHz local-oscillator signal, will be discussed.

Cryogenic 2 mm wave electron spin resonance spectrometer with application to atomic hydrogen gas below 100 mK

We describe a 128 GHz electron-spin-resonance spectrometer based on heterodyne detection with double frequency conversion utilizing cryogenic Schottky-diode mixers. Together with other mm-wave components installed into a dilution refrigerator cryostat, the mixers comprise a bridge operating at 1.5 K. A miniature Fabry–Perot resonator is used to detect samples of bulk and surface-adsorbed atomic hydrogen gas at temperatures below 100 mK. The sensitivity is 2×109 spins/Gauss at the excitation power of 20 pW.

Development and Study of a Planar Schottky-Diode Mixer for the 1.5-mm Waveband

We describe the design of a waveguide planar Schottky-diode mixer for frequencies of about 200 GHz and a measurement system for testing the mixer performance. A backward-wave oscillator with a frequency doubler was used as the local oscillator. The results of room-temperature measurements of the mixer conversion losses and noise temperature as functions of the frequency and power of the local oscillator are presented.

A Broad-Band Low-Noise Schottky Diode Full-Height Waveguide Mixer from 80 to 115 GHz

The RF matching problem in the input circuit of the mm-wavelength whisker contacted Schottky diode mixer is studied. The experimental results, obtained on the 3mm wavelength mixer mounts in the broad band of frequencies from 80 to 115 GHz are presented. It is shown that advantage in the receiver noise temperature may be realized by the use of a full-height instead of 1/4-reduced-height waveguide because of reduction loss in the mixer input circuit even beginning from the 3mm-wavelength. With a full-height waveguide mixer the double sideband (DSB) receiver noise temperature is 300 divided by 350K over the 85 to 110 GHz band. Input bandwidth of the fullheight waveguide mixer (cap delta fS/fSO greater than 30%) is equal to 1/2-and close to 1/4-reduced-height waveguide mixers.

Quantitative Millimetre Wavelength Spectrometry

Quantitative Millimetre Wavelength Spectrometry

High-Tc superconducting microbolometer for terahertz applications

Superconducting hot electron bolometer mixers are now a competitive alternative to Schottky diode mixers in the terahertz frequency range because of their ultra wideband (from millimeter waves to visible light), high conversion gain, and low intrinsic noise level. High Tc superconductor materials can be used to make hot electron bolometers and present some advantage in term of operating temperature and cooling. In this paper, we present first a model for the study of superconducting hot electron bolometers responsivity in direct detection mode, in order to establish a firm basis for the design of future THz mixers. Secondly, an original process to realize YBaCuO hot electron bolometer mixers will be described. Submicron YBaCuO superconducting structures are expitaxially sputter deposited on MgO substrates and patterned by using electron beam lithography in combination with optical lithography. Metal masks achieved by electron beam lithography are insuring a good bridge definition and protection during ion etching. Finally, detection experiments are being performed with a laser at 850 nm wavelength, in homodyne mode in order to prove the feasibility and potential performances of these devices.

High- Tc hot electron superconducting bolometer for terahertz applications

The emergence of superconducting nanotechnologies has raised a large interest in hot electron bolometers for terahertz applications, as a substitute to superconductor–insulator–superconductor or Schottky diode mixers. Emphasis is given there to high- T c YBa 2Cu 3O 7− δ (YBaCuO) nanobolometer thermal modelling to simulate the device performance in direct detection mode. This approach allows one to identify the significant cut-off frequencies accurately and establish the link between classical (macroscopic) and hot electron (microscopic) bolometric effects with respect to YBaCuO nanobridge geometrical parameters. The feedback phenomena arising from the bridge load impedance and self-heating effects are also shown to influence the frequency response significantly.