A Study of W-Band Subharmonically Pumped Mixer

A W-band subharmonically pumped mixer with packaged Schottky diodes has been developed. The design and performance of this mixer are described in detail. A new method for measuring the embedding network parameters of the subharmonically pumped mixer has been developed and the measurement bas been carried out directly at 2f/sub LO/ and 2f/sub LO/+-f/sub if/. A special program for the analysis of the subharmonically pumped mixer has been developed, and computed results are given in comparison with measured results.     

Numerical Analysis of Subharmonic Mixers Using Accurate and Approximate Models

A full nonlinear numerical analysis technique is applied to subharmonically pumped mixer circuits where the two diodes are not identical. Results indicate that a slight imbalance in the diode parasitic parameters can significantly affect the mixer performance. A bilinear approximation of the Schottky-barrier diode characteristic is described, permitting accurate determination of the conversion loss peaks for millimeter-wave subharmonically pumped mixers. This approximation provides an analysis which requires significantly less computer time than a full nonlinear analysis.     

Measurements on a 215-GHz subharmonically pumped waveguide mixerusing planar back-to-back air-bridge Schottky diodes

This paper presents design and performance data for a 215-GHz subharmonically pumped waveguide mixer using an antiparallel-pair of planar air-bridge-type GaAs Schottky-barrier diodes. The waveguide design is a prototype for a 640-GHz system and uses split-block rectangular waveguide with a 2:1 width-to-height ratio throughout. The measured mixer noise and conversion loss are below that of the best reported whisker contacted or planar-diode mixers using the subharmonic-pump configuration at this frequency. In addition, the required local oscillator power is as low as 3 mW for the unbiased diode pair, and greater than 34 dB of LO noise suppression is observed. Separate sideband calibration, using a Fabry-Perot filter, indicates that the mixer can be tuned for true double sideband response at an intermediate frequency of 1.5 GHz. Microwave scale model measurements of the waveguide mount impedances are combined with a mixer nonlinear analysis computer program to predict the mixer performance as a function of anode diameter, anode finger inductance, and pad-to-pad fringing capacitance. The computed results are in qualitative agreement with measurements, and indicate that careful optimization of all three diode parameters is necessary to significantly improve the mixer performance     

Compact 28-GHz subharmonically pumped resistive mixer MMIC using a lumped-element high-pass/band-pass balun

This work reports a novel lump-element balun for use in a miniature monolithic subharmonically pumped resistive mixer (SPRM) microwave monolithic integrated circuit. The proposed balun is simply analogous to the traditional Marchand balun. The coupled transmission lines are replaced by lump elements, significantly reducing the size of the balun. This balun requires no complicated three-dimensional electromagnetic simulations, multilayers or suspended substrate techniques; therefore, the design parameters are easily calculated. A 2.4-GHz balun is demonstrated using printed circuit board technology. The measurements show that the outputs of balun with high-pass and band-pass responses, a 1-dB gain balance, and a 5/spl deg/ phase balance from 1.7 to 2.45 GHz. The balun was then applied in the design of a 28-GHz monolithic SPRM. The measured conversion loss of the mixer was less than 11dB at a radio frequency (RF) bandwidth of 27.5-28.5 GHz at a fixed 1 GHz IF, a local oscillator (LO)-RF isolation of over 35 dB, and a 1-dB compression point higher than 9 dBm. The chip area of the mixer is less than 2.0 mm/sup 2/.     

Metamorphic HEMT MMICs and Modules for Use in a High-Bandwidth 210 GHz Radar

In this paper, we present the development of advanced W-band and G-band millimeter-wave monolithic integrated circuits (MMICs) and modules for use in a high-resolution radar system operating at 210 GHz. A W-band frequency multiplier by six as well as a subharmonically pumped 210 GHz dual-gate field-effect transistor (FET) mixer and a 105 GHz power amplifier circuit have been successfully realized using our 0.1 mum InAlAs/InGaAs based depletion-type metamorphic high electron mobility transistor (mHEMT) technology in combination with grounded coplanar circuit topology (GCPW). Additionally, a 210 GHz low-noise amplifier MMIC was fabricated using our advanced 0.05 mum mHEMT technology. To package the circuits, a set of waveguide-to-microstrip transitions has been realized on 50 mum thick quartz substrates, covering the frequency range between 75 and 220 GHz. The presented millimeter-wave components were developed for use in a novel 210 GHz radar demonstrator COBRA-210, which delivers an instantaneous bandwidth of 8 GHz and an outstanding spatial resolution of 1.8 cm.     

Subharmonically Pumped Millimeter-Wave Mixers

The two-diode subharmonically pumped stripline mixer has a pair of diodes shunt mounted with opposite polarities in a stripline circuit between the signal and local oscillator inputs. The circuit has low noise and conversion loss and substantial AM local oscillator noise cancellation.The local oscillator frequency is about half the signal frequency. A novel diode chip, the notch-front diode, which has ohmic contacts on the chip faces adjacent the face containing the diode junctions, was developed for these circuits. The notch-front diode permits the low parasitic reactance of the waveguide diode mount to be achieved in stripline circuits. The best performance for a two-diode subharmonically pumped mixer with notch-front diodes was a 400 K mixer noise temperature, obtained at 98 GHz which is comparable to the best fundamental mixers in this frequency range. The performance over a 47-110-GHz frequency range for this circuit with commercial beam-lead diodes is also presented.     

The design and development of a 140GHz beam-lead diode subharmonically pumped mixer

The possibility of using beam-lead diodes in the design of a 140GHz subharmonically pumped mixer was investigated. An easily assembled, rugged mixer structure was developed which avoids the problems associated with present production techniques and reduces costs. The construction of the circuit developed makes it ideally suited to space and other environmentally demanding application. Computer analysis techniques were used to predict millimetre-wave performance and a large-scale low-frequency model was used to optimize the circuit. The millimetre-wave mixer was constructed using a circuit implemented on suspended substrate stripline. Results of millimetre-wave performance are presented.     

Noise and Loss in Balanced and Subharmonically Pumped Mixers: Part II--Application

The theory presented in Part I is applied here to some simple two-diode subharmonically pumped and balanced mixers. It is shown that the magnitude of the loop inductance (seen by currents circulating through the two diodes) affects the subharmonically pumped mixer much more strongly than the balanced mixer. The theory is also applied to the ideal two-diode mixer (balanced or subharmonically pumped) using exponential diodes with no series resistance and no nonlinear capacitance. It is shown that, like its single-diode counterpart, this mixer has a noise-equivalent lossy network whose physical temperature is eta T/2, where eta is the ideality factor of the exponential diodes. It follows that the ideal subharmonically pumped resistive mixer is not intrinsically less noisy than the ideal resistive fundamental mixer. This is not necessarily the case if parametric effects, due to nonlinear diode capacitance, are present.     

Analysis and Design of a Novel $times$4 Subharmonically Pumped Resistive HEMT Mixer

In this paper, a novel topology of an HEMT-based subharmonically pumped resistive mixer (SHPRM) is presented, i.e., the times4SHPRM. The presented topology requires only a quarter of the local oscillator (LO) frequency compared to a fundamentally pumped mixer (e.g., 15 instead of 60 GHz in a 60-GHz system). This reduction in required LO frequency provides a significant reduction in complexity of the overall radio front-end and reduces the dc power consumption as well as the occupied chip area. Thus, the times4SHPRM provides a significant cost reduction for a millimeter-wave system. Furthermore, the times4SHPRM can be used for both up- and down-conversion and it can be implemented in any field-effect transistor technology. The principle of the times4SHPRM is presented and wave analysis is applied in order to investigate the fundamental limitations of this mixer topology. For an evaluation of the times4SHPRM topology, three different monolithic microwave integrated circuits (MMICs) were designed and manufactured in the same MMIC metamorphic HEMT technology. Besides measured performance of the times4SHPRM, a traditional times2SHPRM and a single-ended resistive mixer were implemented and their performances are presented and compared. All of these MMICs operate with a 60-GHz RF frequency and employ LO signals close to 15, 30, and 60 GHz, respectively.     

High-order subharmonically pumped mixers using phased local oscillators

A high-order subharmonically pumped mixer architecture that utilizes multiple pairs of antiparallel diodes is described. A key component of the mixer architecture is a K-way power-divider/phase shifter that divides the local oscillator (LO) to multiple ports with equal magnitude and prescribed phase shifts. Undesired mixing products are eliminated through phase cancellation by symmetry rather than relying on intermediate idler circuits. As a proof-of-principle demonstration, an eighth-order mixer is implemented based on this approach and has shown a measured conversion loss of 8 dB at 8 GHz. The mixer architecture is suitable for applications in the millimeter and submillimeter-wave regions where high-frequency LOs are difficult to implement.     

A Planar Quasi-Optical Subharmonically Pumped Mixer Characterized by Isotropic Conversion Loss

By using a subharmonically pumped circuit in a quasi-optical planar mixer, we have found it possible to use an LO frequency of one-half the normaf value with little added circuit complexity. This circuit shows conversion loss as low as 8.6dB +- 2 dB at 14 GHz. Through the means of a newly defined quasi-optical mixer parameter called isotiopic conversion loss (L/sub iso/), we find that performance of the mixer system degrades less than 10 dB from an RF input of 14 GHz to 35 GHz, which is more than twice the designed RF frequency.     

A 78-114 GHz monolithic subharmonically pumped GaAs-based HEMTdiode 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 μm 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     

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.     

Low-parasitic, planar Schottky diodes for millimeter-waveintegrated circuits

The design and fabrication of air-bridged, ultra-low-capacitance Schottky barrier diodes are described. Mott diodes, for mixer applications, and varactor diodes, for use in frequency multipliers, have been produced simultaneously on epitaxial wafers grown by molecular beam epitaxy. Typical mixer diodes have a nominal anode contact area of 4 μm² and exhibit a total zero-bias capacitance of 4.0-4.5 fF (including a parasitic capacitance of approximately 1.0 fF) and a series resistance of 6-8 Ω. Diode chips have been incorporated in hybrid integrated circuit (MIC) mixers for 33-50 GHz and 75-110 GHz and an MIC frequency tripler for 90-140 GHz. Fully monolithic (MMIC) subharmonically pumped mixers for 75-110 GHz have also been fabricated and tested     

The Measured and Computed Performance of a 140--220 GHz Schottky Diode Mixer

In this paper, we compare the measured and theoretical performance of a room-temperature single-ended Schottky diode mixer in the WR-5 (140-220-GHz) waveguide band. Using the computer program GISSMIX, combined with measurements made on a 100X scale model of the WR-5 mixer, we have been able to predict the millimeter-wave mixer performance over a wide tuning range with unprecedented accuracy. In addition we have examined the sensitivity of the mixer performance to various diode and mount characteristics. Our rneasured conversion loss and mixer noise temperature, single sideband, are 5.7 dB and 750 K at 180 GHz, and 5.7 dB and 500 K at 150 GHz, which we believe to be the best reported for a room-temperature mixer at these frequencies.     

Millimeter-wave-band amplifier and mixer MMICs using a broad-band45° power divider/combiner

This paper demonstrates millimeter-wave-band amplifier and mixer monolithic microwave integrated circuits (MMIC's) using a broad-band 45° power divider/combiner. At first, we propose a broad-band 45° power divider/combiner, which combines a Wilkinson divider/combiner, 45° delay line, and 90° short stub. A coupling loss of 4.0±0.2 dB and a return loss and an isolation of more than 19 dB with 45±1° phase difference was obtained from 17 to 22 GHz for the fabricated K-band MMIC 45° power divider/combiner. Next, a parallel amplifier using the broad-band 45° power divider/combiner, which can be used in a power-combining circuit configuration requiring no isolator, is shown. Comparing the transmitter intermodulation generated in the parallel amplifier using the broad-band 45° power divider/combiner and that generated in the one using the conventional type, the broad-band suppression effect was confirmed. Finally, an application of the broad-band 45° power divider/combiner to a single-sideband (SSB) subharmonically pumped (SHP) mixer requiring no IF switch is shown. In an RF frequency range from 22.89 to 26.39 GHz, the fabricated K-band MMIC mixer achieved (for up-conversion) the good results of more than -13-dB conversion gain and more than 24-dB image-rejection ratio. These contribute significantly to the miniaturization of millimeter-wave communication equipment     

Noise and Loss in Balanced and Subharmonically Pumped Mixers: Part I--Theory

In this paper, the theory of noise and frequency conversion is developed for two-diode balanced and subharmonically pumped mixers. Expressions for the conversion loss, noise temperature, and input and output impedances are derived in a form suitable for numerical analysis. Schottky diodes are assumed, having nonlinear capacitance, series resistance (which may be frequency dependent due to skin effect), and shot and thermal noise. In Part II, the theory is applied to several practical examples, and computed results are given which show the very different effects of the loop inductance (between the diodes) in balanced and subharmonically pumped mixers. It is also shown that the ideal two-diode mixer using exponential diodes has a multiport noise-equivalent network (attenuator) similar to that of the ideal single-diode mixer.     

A Broad-Band Second-Harmonic Mixer Covering 76-106 GHz

A broad-band second-harmonic millimeter-wave mixer has been constructed. The circuit consists of a single unencapsulated Schottky-barrier diode and embedding network which includes a wave absorber in the IF output terminal. The conversion loss of the mixer is 14.6/spl plusmn/0.9 dB over a frequency range of 76-106 GHz. The mixer is pumped by a Iocal oscillator that is tuned over the range of 37.15-52.15 GHz. The IF is kept constant at 1.7 GHz. The new mixer looks attractive for use in broad-band millimeter-wave measuring equipment, such as spectrum analyzers.     

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.