Diode Mixer Research Articles

4H-silicon carbide schottky barrier diodes for microwave applications

In this paper, physical models for vertical 4H-silicon carbide (4H-SiC) Schottky diodes are used to develop a design method, where a maximum cutoff frequency for a given punch-through is achieved. The models presented are also used to extract microwave simulator computer-aided design (CAD) models for the devices. A device process was developed and Schottky diodes were fabricated in-house. Characterization of the devices was performed and compared to the theoretical models with good agreement. A demonstrator singly balanced diode mixer was simulated using the developed models. The mixer was fabricated using the in-house developed diodes, and measurements on the mixer show good agreement with the CAD simulations. A conversion loss of 5.2 dB was achieved at 850 MHz, and an excellent IIP/sub 3/ of 31 dBm at 850-MHz RF was measured, at 30-dBm P/sub LO/. These results verify the enhanced properties of the SiC Schottky diode compared to other nonwide bandgap diodes.

Intermodulation-distortion performance of silicon-carbide schottky-barrier RF mixer diodes

This paper presents the fabrication and characterization of silicon carbide (SiC) Schottky-barrier mixer diodes of 25- and 50-/spl mu/m diameter on a conducting 4H-SiC wafer. The single-balanced mixer circuits with a diode in each arm (two diodes total) were tested at 200 MHz (VHF) and 1.5 GHz [global positioning system (GPS)]. The experiments show that the conversion loss/input third-order intercept point (IP3) are 8.0 dB/+25 dBm and 7.5 dB/+22 dBm at these frequencies, respectively. The measured second-order intercept point (IP2) over the VHF frequency band is +38 dBm. The above conversion-loss values are about the same as that of commercially available single-balanced mixers with silicon Schottky-barrier diodes. However, to achieve a comparable input IP3 performance with Si Schottky-barrier diodes, a more complex mixer design involving double-balanced mixers with two diodes in each arm of a quad (eight diodes total) is required. Applications include RF-based navigational instruments on board commercial/general aviation aircraft and GPSs.

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.

Compact single-chip W-band FMCW radar modules for commercial high-resolution sensor applications

Two compact single-chip 94-GHz frequency-modulated continuous-wave (FMCW) radar modules have been developed for high-resolution sensing under adverse conditions and environments. The first module contains a monolithic microwave integrated circuit (MMIC) consisting of a mechanically and electrically tunable voltage-controlled oscillator (VCO) with a buffer amplifier, 10-dB coupler, medium-power and a low-noise amplifier, balanced rat-race high electron-mobility transistor (HEMT) diode mixer, and a driver amplifier to increase the local-oscillator signal level. The overall chip-size of the FMCW radar MMIC is 2/spl times/3.5 mm/sup 2/. For use with a single transmit-receive antenna, a 94-GHz microstrip hexaferrite circulator was implemented in the module. The radar sensor achieved a tuning range of 1 GHz, an output signal power of 1.5 mW, and a conversion loss of 2 dB. The second FMCW radar sensor uses an MMIC consisting of a varactor-tuned VCO with injection port, very compact transmit and receive amplifiers, and a single-ended resistive mixer. To enable single-antenna operation, the external circulator was replaced by a combination of a Wilkinson divider and a Lange coupler integrated on the MMIC. The circuit features coplanar technology and cascode HEMTs for compact size and low cost. These techniques result in a particularly small overall chip-size of only 2/spl times/3 mm/sup 2/. The packaged 94-GHz FMCW radar module achieved a tuning range of 6 GHz, an output signal power of 1.5 mW, and a conversion loss of 5 dB. The RF performance of the radar module was successfully verified by real-time monitoring the time flow of a gas-assisted injection molding process.

The submillimeter wave astronomy satellite: instrument & mission description

The Submillimeter Wave Astronomy Satellite ( SWAS), launched in December 1998, is a NASA mission dedicated to the study of star formation through direct measurements of: (1) molecular cloud composition and chemistry; (2) the cooling mechanisms that facilitate cloud collapse; and, (3) the large-scale structure of the UV-illuminated cloud surfaces. To achieve these goals, SWAS is conducting pointed observations of dense ( n(H 2)>10 3 cm −3) molecular clouds throughout our Galaxy in either the ground-state or a low-lying transition of five astrophysically important species: H 2O, H 2 18O, O 2, CI, and 13CO. By observing these lines SWAS is: (1) testing long-standing theories that predict that these species are the dominant coolants of molecular clouds during the early stages of their collapse to form stars and planets; and (2) supplying previously missing information about the abundance of key species central to the chemical models of dense interstellar gas. SWAS carries two independent Schottky barrier diode mixers — passively cooled to ∼ 175 K — coupled to a 54 × 68-cm off-axis Cassegrain antenna. During its baseline three-year mission, SWAS is observing giant and dark cloud cores with the objective of detecting or setting a 3σ upper limit on the water and molecular oxygen abundance of 3 × 10 −6 (relative to H 2). In addition, advantage is being taken of SWAS's relatively large beamsize of 3.3 × 4.5 arcminutes at 553 GHz and 3.5 × 5.0 arcminutes at 490 GHz to obtain large-area (∼1° × 1°) maps of giant and dark clouds in the 13CO and CI lines. With the use of a 1.4 GHz bandwidth acousto-optical spectrometer, SWAS has the ability to simultaneously observe either the H 2O, O 2, CI, and 13CO lines or the H 2 18O, O 2, and CI lines with a velocity resolution ∼- 1 km s −1.

RF and IF ports matching circuit synthesis for a simultaneous conjugate-matched mixer using quasi-linear analysis

A quasi-linear two-port approach between RF and IF ports to design a simultaneous conjugate-matched mixer is presented in this paper. Conventionally, mixer design is treated as a nonlinear three-port device problem. Nonetheless, with the exception of the large-signal local oscillator (LO) that exists at the LO port, the input RF and output IF signals that exist at the RF and IF ports, respectively, are small signals. Consequently, mixers can be approximated as bilateral quasi-linear two-port circuits with a time-variant transfer function between the RF and IF ports, in which the LO port of the mixer is treated as part of the two-port network. With this approximation, it can be shown mathematically that the optimum source and load matching networks required for attaining simultaneous conjugate match at the RF and IF ports are actually time invariant, thus implying that it is possible to synthesize these optimum impedance values. This proposed mixer design technique, together with the equations derived, are verified with block-diagram simulation and experimental measurements of two 2.4-GHz RF/420-MHz IF double-balanced diode mixers.

Quantitative Millimetre Wavelength Spectrometry

Quantitative Millimetre Wavelength Spectrometry

A 78-114 GHz monolithic subharmonically pumped GaAs-based HEMT diode mixer

A W-band subharmonically pumped (SHP) diode mixer is designed for fixed LO frequency operation. It is fabricated on a 4-mil substrate using 0.15 /spl mu/m GaAs PHEMT MMIC process. The on-wafer measurement results show that the conversion loss is about 10 to 14 dB across the W band, as a 10 dBm 48 GHz LO signal is pumped. To our knowledge, this is the state-of-the-art result on low-conversion-loss wideband MMIC SHP diode mixer. The packaged module measurement shows a similar result. Both the simulation and measurement results are shown to be in good agreement.

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.

Arithmetic of 1/f noise in a phase locked loop

Frequency countings close to a phase locked zone in an electronic receiver show a 1/f power spectral density. The noise scaling versus the frequency deviation and the open loop gain are found from Adler’s model of the phase locked loop. This fully agrees with experiments performed at 5 MHz on a receiver with a Schottky diode mixer and a low pass filter. The 1/f amplitude and frequency noise due to the whole set of (sub)harmonics is explained from a nonlinear mapping, with a coupling coefficient related to the structure of prime numbers.

50 years development of the microwave mixer for heterodyne reception

A brief technical historical review of mixer development, in its application as the frequency down-converter for the microwave and millimeter-wave heterodyne receiver, provides the background to discussion of mixer design, technology, and performance characteristics. In general terms, today's mixers designs are based on the 1970s principles, but technology progress in the solid-state frequency-mixing element and associated integrated circuits has been significant, with exploitation of the monolithic potential. Performance advancements have mainly been in the increased frequency capabilities of the planar Schottky barrier diode mixer, broad application of the three terminal devices, and balun implementation.

Difference frequency injection linearisation technique for mixer systems

A mixer linearisation technique based on difference frequency injection has been proposed and experimentally presented in a system level approach. The system analysis and the effects of amplitude and phase sensitivity on its performance are described. The technique has been demonstrated with an L-band up-conversion double-balanced diode mixer and both simulation and experimental results achieved have shown that this technique can substantially reduce third-order intermodulation distortion.

New predistortion linearizer using low-frequency even-order intermodulation components

We present two types of new predistortion linearizers using low-frequency even-order components. One adopts an in-phase and quadrature balanced modulator as a generator of the third-order intermodulation (IM3) and fifth-order intermodulation (IM5) components and the other adopts a double-balanced diode mixer. Both types are very compact and could independently control the amplitudes and phases of the intermodulation (IM) components. We have analyzed the delay mismatch effect of these predistortion circuits. The result shows that the IM5 components are twice as sensitive than the third ones. Two types of predistorters are implemented and tested at the International Mobile Telecommunications-2000 band. Two tone test results show that the IM3 cancellation is about 23-25 dB and the IM5 is cancelled by about 12-20 dB for both cases. The adjacent channel power ratio is improved by over 11 dB at the broad-band CDMA signal with a chip rate of 4.096 Mc/s, and this improvement is maintained through a broad range of output power level.

DC and RF characteristics of MBE grown GaAs barrier diode

Schottky barriers are used extensively in high frequency switching, mixing and rectifying circuit for their good DC and RF characteristics. In this paper we report that devices measured in a double-balance mixer circuit show that the typical value of the DBS noise figure of the mixer diode is 6.1 dB at 89.5 GHz. Very good results were also observed in the 12.5, 8, 5 and 4 mm bands. However, the barrier height is virtually constant and the operation stability depends strongly on the metallurgy of the Schottky contact. In addition, properties of planar doped barrier (PDB) diodes with an n +/i/p +/i/n + configuration grown by molecular beam epitaxy (MBE) with precise control of the barrier height, were also studied. The results of artificial tailored I– V characteristics, junction capacitance and the detector application are also presented.

Design and characterisation of singly balancedsilicon carbide Schottky diode high-level mixer

A singly balanced silicon carbide Schottky diode mixer was designed and characterised. The mixer has a minimum conversion loss of 5.2 dB and a third-order intermodulation input intercept point of 31 dBm at 850 MHz.

A 492 GHz Submillimeter-Wave Receiver

A 492 GHz submillimeter receiver was designed for application to the POrtable Submillimeter Telescope (POST). The receiver includes a Schottky diode mixer, a phase-locked Gunn oscillator at 82.3 GHz coupled with multipliers (×2×3), and low-noise amplifiers. In this paper, the system configuration and performance will be introduced.

Application of millimeter-wave imaging system to LHD

Millimeter-wave imaging systems in the frequency range of 70–140 GHz have been developed for diagnostics of magnetically confined plasmas. The 70 GHz imaging system successfully measures time evolutions of both radial and axial profiles of line density and electron cyclotron emission (ECE) in a tandem mirror. The imaging system is being installed in Large Helical Device (LHD) at the National Institute for Fusion Science. In order to cover the frequency range of the second harmonic ECE on LHD, a new detector using monolithic microwave integrated circuit technology has been designed and fabricated. The detector consists of the integration of a receiving antenna, a down-converting mixer diode, and an intermediate frequency amplifier on a GaAs substrate chip. The heterodyne response up to 10 GHz was confirmed at 70–140 GHz. The optical system consisting of an ellipsoidal mirror and a flat mirror was designed by using a ray-tracing code and evaluated experimentally at 140 GHz.

Millimeter-wave imaging array development for microwave reflectometry and ECE imaging

Millimeter-wave imaging arrays employing slot bow-tie (SBT) antenna elements and GaAs Schottky diodes have previously been previously successfully developed and utilized in electron cyclotron emission imaging systems, which have proven to be an important new plasma diagnostic technique for measuring plasma electron temperature profiles and fluctuations. More recently, there has been interest in applying similar arrays for reflectrometric imaging. Here, the design of SBT antennas for proof-of-principle millimeter-wave imaging reflectometry receiver arrays for use on Torus Experiment for Technology Oriented Research is presented. These low-cost, 14-channel Schottky mixer diode arrays, designed at 85 GHz, have been developed for measuring plasma electron density fluctuation profiles, which are expected to solve the long standing issue of ambiguity in the interpretation of reflectometric data. The final layout of the array is shown, together with details and experimental results of single SBT antennas.

The [ITAL]Submillimeter Wave Astronomy Satellite[/ITAL]: Science Objectives and Instrument Description

The submillimeter wave astronomy satellite (SWAS) mission is dedicated to the investigation of star formation and interstellar chemistry. In order to perform the mission, SWAS will survey dense molecular clouds within the Milky Way Galaxy in either the ground state or a low-lying transition of five astrophysically-significant species: H2O, H2(18)O, O2, C I and (13)CO. The observation of these lines will: test theories that predict that these species are dominant coolants of molecular clouds during early stages of their collapse to form stars and planets, and supply information concerning the abundance of species central to the chemical models of dense interstellar gas. The SWAS will use two independent Schottky barrier diode mixers and a 53 x 68 sq cm, off-axis Cassegrain antenna.