Mixer Configuration Research Articles

Minimization of baseline disturbances in peptide mapping by means of principal-component multivariate visualization

Abstract Optimum method parameters for minimizing baseline disturbances in gradient HPLC peptide mapping were identified by the use of principal component mapping. Gradient baseline disturbances were attributed to differences in extinction coefficients between low concentrations of trifluoroacetic acid (0.1%, v/v) in water and in acetonitrile mobile phases. Method parameters that were investigated included (1) column differences, (2) trifluoroacetic acid concentration, (3) mobile phase mixer configuration and (4) detector wavelength. Items (1) and (3) were identified as the most significant method parameters.

Frequency stabilization of NRD waveguide gunn oscillator at 60 GHz

AbstractFrequency stability of a 60‐GHz nonradiative dielectric (NRD) waveguide InP Gunn diode oscillator has been improved based on the phase‐locked‐loop technique. All the millimeter wave circuit elements needed, including the directional coupler, circulator, and so on, have been fabricated by using the NRD waveguide and a new approach has been introduced for harmonic mixer configuration by combining an NRD waveguide and a laterally shielded coplanar transmission line. By means of this approach, the millimeter wave circuit can be contained in a compact housing of 4 cm × 6 cm in area. The stability of the oscillation frequency of the fabricated Gunn oscillator was 2.1 × 10−10 (13 Hz/60 GHz). Further, the phase noise was kept to a small value of ‐48 dBc/Hz. The present results confirm the applicability of the NRD waveguide in the 60‐GHz band.

CFD predictions of lobed mixer performance

A finite volume calculation procedure has been used to predict the flow and temperature mixing in a multilobed mixer/nozzle geometry. The method adopts a non-aligned mesh to solve the steady-state three-dimensional elliptic equations describing the flow within the lobes. The calculation of the downstream mixing duct is then coupled with the lobe flow predictions to allow for the prediction of the complete lobed mixer/nozzle system. The calculation method and some initial predictions have been presented in [1]. The basic model and an improved version of the method obtained by implementing a higher-order finite-difference scheme are employed in the present computations to assess numerical accuracy. A series of numerical parametric studies are then undertaken to investigate performance variations brought about by changes in mixer inflow conditions. Attention is focussed on the prediction of overall performance parameters such as mixing effectiveness and total pressure losses which are essential in engineering design studies. It is demonstrated that the CFD method used, is capable of providing accurate and useful information for design purposes, and flowfield/temperature distributions which are otherwise difficult and expensive to obtain. It forms an important new tool for the evaluation and optimisation of internal lobed mixer configurations.

100 GHz mixer vertically integrated (stacked) SIS junction array

A Vertically Integrated Array (stacked array) of single windowSIS junctions (VIA SIS), based on a stacked five layer structure of Nb-AlOx-Nb-AlOx-Nb, has been fabricated and tested in a quasi optical mixer configuration at 106 GHz. This particular VIA SIS design has two stacked junctions fabricated by standard tri-layer process employing photolithography, reactive ion and wet etching processes. A simple expression for calculating the specific capacitance of single and arrayed SIS junctions is suggested. Due to the absence of interconnection leads between the individual junctions and reduced overall capacitance, compared to a single SIS junction, has the VIA SIS good future prospects for use in submillimeter wave SIS mixers The VIA SIS may be regarded as a lumped rather than a distributed structure at least up to the gap frequency at 730 GHz for Nb. DC-IV measurements show high quality of the Individual SIS junctions and good reproducibility of the array parameters over the substrate area. The first VIA SIS mixer experiments yielded a receiver noise temperature of 95 K (DSB) at a LO frequency of 106 GHz.

Wide-bandwidth electron bolometric mixers: a 2DEG prototype and potential for low-noise THz receivers

A new type of electron bolometric (hot electron) mixer is presented. The authors have demonstrated a three-order-of-magnitude improvement in the bandwidth compared with previously known types of electron bolometric mixers, by using the two-dimensional electron gas (2DEG) medium at the hetero-interface between AlGaAs and GaAs. Both in-house, MOCVD-grown material and MBE material were tested with similar results. The conversion loss (L/sub c/) at 94 GHz is presently 18 dB for a mixer operating at 20 K, and calculations indicate that L/sub c/ can be decreased to about 10 dB in future devices. Calculated and measured curves of L/sub c/ versus P/sub Lo/ and I/sub DC/, respectively, agree well. It is argued that there the several different known configurations of electron bolometric mixers will all show wide bandwidth, and that these devices are likely to become important as low-noise terahertz receivers in the future.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Beam scanning microstrip arrays using diodes

The feasibility of using diodes in linear microstrip antenna arrays to facilitate electronic beam scanning is investigated. The first concept concerns a microstrip line loaded with varactor diodes serving the dual purpose of phase shifter and feeder for a linear travelling wave array. Theoretical and practical results provide antenna design data on the number and type of diodes, optimisation of the radiating elements and temperature effects. Likely noise figure degradation, transient beam scanning response, and the antenna construction are other design aspects discussed. An array at 7.5 GHz containing 24 varactor diodes demonstrates that some 20° of beam scan is achievable before the travelling wave action is disrupted, and confirms the usefulness of the concept for applications demanding modest beam scan range and a simple low cost construction. The second concept introduced is a novel microstrip patch element with embedded diode and polariser enabling mixer action to take place. The theoretical and practical design of this antenna mixer element, and its deployment in an eight element linear beam scanning array at 2.92 GHz, is presented. Other mixer configurations, using additional diodes offering superior suppression of spectral products, are noted and the possible influence of the polariser on interelement mutual coupling investigated. Computations and measurements show that coupling effects are not significantly increased and confirm the usefulness of the antenna mixer element concept in beam forming array applications where no premixer low noise amplification is demanded.

D-band subharmonic mixer with silicon planar doped barrier diodes

A subharmonically pumped finline mixer applying a silicon planar doped barrier diode has been developed for D-band frequencies. Diode processing and DC characteristics are discussed, and a circuit description is given. Excellent mixing properties (minimum conversion loss) of 10.8 dB) favor this mixer configuration for application in low-cost receivers operating at those RF bands (above 120 GHz) where fundamental low-noise, solid-state oscillators are not currently available. >

Monolithic integrated coherent receiver on InP substrate

The fabrication of a monolithic integrated coherent receiver with a wavelength-tunable DFB laser as local oscillator, a 3-dB waveguide directional coupler for mixing, and p-i-n photodiodes for detection is discussed. Optical heterodyne detection with a clear beat signal was experimentally observed using this monolithic integrated coherent receiver. Since an n-type substrate was used in this device, the two p-i-n photodiodes were not implemented in a balanced mixer configuration. Balanced mixing might be possible if the same structure were fabricated on a semi-insulating substrate. The results obtained suggest the possibility of applying this type of monolithic integrated coherent receiver to optical communication systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Three-dimensional inviscid flow in mixers. II - Analysis of turbofanforced mixers

A small disturbance formulation for the three-dimensional potential analysis of the inviscid flow over a turbofan forced mixer configuration in which the governing equations are reduced by means of a flux volume formulation along a Cartesian grid is presently extended to include the effects of power addition within the potential formulation. Calculations are presented for practical turbofan mixer designs, and comparison calculations are also given with measured surface pressure distributions and measured axial velocity profiles.

Efficient technique for solving nonlinear mixer pumping problem

An efficient technique for solving the nonlinear mixer pumping problem is described. The technique can be applied to mixer configurations where the impedance presented to the diode at the local oscillator frequency and its harmonics are known.

S- and X-Band GaAs FET Mixers with Thin-Film Lumped Elements (Short Paper)

The design and performance of 2- and 11-GHz band mixers with a single-gate GaAs FET are presented in this paper. A mixer configuration in which the load oscillator (LO) signal is applied to the source is used. Matching networks are constructed with thin-film lumped elements fabricated on alumina. An SSB noise figure of 6.2 dB, with an associated conversion gain of 10 dB, has been achieved at the 11-GHz band, and SSB noise figures of less than 6 dB and a conversion gain of more than 8 dB over a 40-percent bandwidth are obtained at the 2-GHz band.

Modes of operation in dual-gate MESFET mixers

The mechanisms of mixing in a dual-gate GaAs MESFET mixer are described. Based on a cascode DC model of the device, several modes of mixer operation are identified. It is shown that each single-gate MESFET in the cascode model can operate as a mixer or amplifier, depending on the DC bias conditions and mixer configuration.

A 31-GHz monolithic GaAs mixer/preamplifier circuit for receiver applications

The portion of a monolithic receiver containing integrated Schottky mixer diodes and MESFET'S with microstrip circuitry has been developed and tested at 31 GHz. This work is part of a program to establish the feasibility of monolithic receivers and transmitters at microwave and millimeter-wave frequencies. Receiver designs using high-cutoff frequency diodes in a mixer configuration followed by a MESFET amplifier are capable of operating from microwave through millimeter-wave frequencies. However, the fabrication of monolithic receiver designs requires the integration on the same wafer of devices with different material requirements. We have developed a compatible integration scheme which is fundamental to the fabrication of monolithic receivers at millimeter-wave frequencies. Fabrication and design considerations for the 31-GHz balanced mixer and IF preamplifier are described. Completed monolithic units typically exhibit a conversion gain of 4 dB from the signal frequency of 31 GHz to the IF frequency of 2 GHz. The associated noise figure is typically 11.5 dB.

Nonlinear-linear analysis of microwave mixer with any number of diodes

A theory is presented for analyzing mixers with any number of diodes. Both the nonlinear and linear steps of the analysis are included. The diodes are characterized by both nonlinear conductance and nonlinear capacitance. Any linear embedding network is allowed. It is assumed that both the parameters of the linear part of a mixer circuit and the parameters of the diodes are known. This general approach to microwave circuits with diodes, which is a qualitatively new problem in circuits analysis, allows to investigate any diode mixer with deep insight into its operation. A computer program has been developed to perform the analysis and all computations. The program has been utilized to analyze a crossbar mixer configuration which exhibits extremely encouraging performance. Some computed results are presented herein.

GaAs FET upconverter for TV tuner

The critical part of a broad-band TV tuner, i.e., the upcon-verter was fabricated with simple GaAs IC's. The results obtained were: 1) "Pure" frequency spectrum due to double balanced mixer configuration. 2) Constant conversion gain of 12 ± 2 dB over the entire TV band (50-900 MHz). 3) Good linearity for large signals: Suppression of third-order intermodulation >40 dB for typical bias. 4) Low noise figure (typically 8 dB). These data demonstrate the feasibility of a monolithically integrated single-range TV tuner on GaAs.

Influence of mixer diode reactances on noise figure and conversion loss

An analysis of Y and Z microwave mixers is presented, incorporating a Schottky-diode model with nonlinear resistance and reactance. The analysis suggests that Y mixers have satisfactory conversion loss and noise figure up to higher frequencies than Z mixers using the same type of diodes. A comparison of four mixer configurations is made.

Influence of mixer diode reactances on noise figure and conversion loss

An analysis of Y and Z microwave mixers is presented, incorporating a Schottky-diode model with nonlinear resistance and reactance. The analysis suggests that Y mixers have satisfactory conversion loss and noise figure up to higher frequencies than Z mixers using the same type of diodes. A comparison of four mixer configurations is made.

Low noise Schottky barrier diode mixers for wavelengths < 1 mm

Recent progress in realizing low noise Schottky diode mixers in the submillimetre region is reviewed. Schottky diodes built on epitaxial material must be carefully optimized through use of E-beam lithography to obtain lowest conversion loss in a particular frequency region. Satisfactory diplexing schemes exist and a number of promising mixer configurations have been developed. The principal problem is a lack of suitable tunable sources of local oscillator power.

Fundamental Limits on Conversion Loss of Double Sideband Resistive Mixers

Although the resistive mixer has been the subject of numerous studies, these have all dealt with specific cases for terminations at the higher order mixing products (idlers). This paper deals with the general case of the double sideband mixer, and demonstrates that when no energy is dissipated at the idler frequencies the fundamental limit on conversion loss is 3 dB, with the lost energy being equally divided between conversion to the image and reflection loss at the signal port. Also treated is the case where matched loads are presented to each idler. It is shown that, in this case, the theoretical limit on conversion loss is 3.92 dB (20 log pi/2), independent of the mixer configuration.

Effects of the Diode Junction Capacitance on the Conversion Loss of Microwave Mixers

The theory of the frequency down-converters, which use sinusoidally driven exponential junction diode, is reviewed here with the purpose of investigating the effects of the junction Capacitance on the conversion loss. The analysis deals With single-ended mixers, both in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</tex> configurations. Their performances are compared with those obtained from the same configurations of mixers using a purely resistive (PR) exponential diode, in cases of both short-circuited and open-circuited image frequency. This comparison shows that the junction capacitance modifies strongly the behavior of the single-ended mixer compared tothe case of purely resistive diodes. It is pointed out that, when the junction capacitance may not be neglected, and the image frequency is either open- or short-circuited, good performance can still be achieved from a sinusoidally driven <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</tex> mixer. On the contrary, the sinusoidally driven <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z</tex> mixer, which Operates better than the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</tex> mixer when the effect of the junction capacitance may be neglected, is strongly deteriorated, and it becomes worse than the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</tex> mixer.