A 1.3-THz Balanced Waveguide HEB Mixer for the APEX Telescope

In this paper, we report about the development, fabrication, and characterization of a balanced waveguide hot electron bolometer (HEB) receiver for the Atacama Pathfinder EXperiment telescope covering the frequency band of 1.25-1.39 THz. The receiver uses a quadrature balanced scheme and two HEB mixers, fabricated from 4- to 5-nm-thick NbN film deposited on crystalline quartz substrate with an MgO buffer layer in between. We employed a novel micromachining method to produce all-metal waveguide parts at submicrometer accuracy (the main-mode waveguide dimensions are 90 times 180 mum ). We present details on the mixer design and measurement results, including receiver noise performance, stability and ldquofirst-lightrdquo at the telescope site. The receiver yields a double-sideband noise temperature averaged over the RF band below 1200 K, and outstanding stability with a spectroscopic Allan time more than 200 s.     

Characterization of a quasi-optical NbN superconducting HEB mixer

In this paper, the performance of a quasi-optical NbN superconducting hot-electron bolometer (HEB) mixer, cryogenically cooled by a close-cycled 4-K refrigerator, is thoroughly investigated at 300, 500, and 850 GHz. The lowest receiver noise temperatures measured at the respective three frequencies are 1400, 900, and 1350 K, which can go down to 659, 413, and 529 K, respectively, after correcting the loss and associated noise contribution of the quasi-optical system before the measured superconducting HEB mixer. The stability of the quasi-optical superconducting HEB mixer is also investigated here. The Allan variance time measured with a local oscillator pumping at 500 GHz and an IF bandwidth of 110 MHz is 1.5 s at the dc-bias voltage exhibiting the lowest noise temperature and increases to 2.5 s at a dc bias twice that voltage.     

A Technology Demonstrator for 1.6–2.0 THz Waveguide HEB Receiver with a Novel Mixer Layout

In this paper, we present our studies on a technology demonstrator for a balanced waveguide hot-electron bolometer (HEB) mixer operating in the 1.6–2.0 THz band. The design employs a novel layout for the HEB mixer combining several key technologies: all-metal THz waveguide micromachining, ultra-thin NbN film deposition and a micromachining of a silicon-on-insulator (SOI) substrate to manufacture the HEB mixer. In this paper, we present a novel mixer layout that greatly facilitates handling and mounting of the mixer chip via self-aligning as well as provides easy electrical interfacing. In our opinion, this opens up a real prospective for building multi-pixel waveguide THz receivers. Such receivers could be of interest for SOFIA, possible follow up of the Herschel HIFI, and even for ground based telescopes yet over limited periods of time with extremely dry weather (PWV less than 0.1 mm).     

Low noise submillimeter SIS receiver with niobium nitride quasiparticle tunnel junctions

We have developed and tested a submillimeter waveguide SIS mixer with NbN-MgO-NbN quasiparticle tunnel junctions. The two junction array is integrated in a full NbN printed circuit. The NbN film critical temperature is 15 K and the junction gap voltage is 5 mV. The size of the junctions is 1.4 × 1.4 µm and Josephson critical current density is about 1.5 KA/cm² resulting in junction R_NωC product about 40. The inductive tuning circuit in NbN is integrated with each junction in two junction array. A single non contacting backshort was tuned at each frequency in the mixer block. At 306 GHz the minimum DSB receiver noise temperature is as low as 230 K. The sources of the receiver noise and of the limits of the NbN SIS submillimeter mixer improvement are discussed.     

A Tuning Circuit with Two Half-Wave Distributed Junctions for All-NbN SIS Mixers

A novel broadband tuning circuit composed of two low-current-density half-wave NbN/MgO/NbN tunnel junctions connected by a half-wave NbN/MgO/NbN microstrip line has been successfully tested in a quasi-optical mixer at frequencies above 700 GHz. The circuit had a designed center frequency of 870 GHz, was integrated in a center-fed twin-slot antenna, and was fed via a quarter-wave impedance transformer. Heterodyne measurments showed double-side-band receiver noise temperatures equivalent to 6-9 quanta from 675 to 810 GHz for a mixer with a current density of 6.7 kA/cm². The RF bandwidth was broader than that of a conventional mixer using a full-wave junction with the same current density.     

Phonon-cooled hot-electron bolometric mixer: overview of recent results

The paper presents an overview of recent results for NbN phonon-cooled hot electron bolometric (HEB) mixers. The noise temperature of the receivers based on both quasioptical and waveguide versions of HEB mixer has crossed the level of 1 K·GHz⁻¹ at 430 GHz (410 K) and 600–650 GHz (480 K) and is close to this level at 820 GHz (1100 K) and 900 GHz (980 K). The gain bandwidth measured for quasioptical HEB mixer at 620 GHz reached 4 GHz and the noise temperature bandwidth was almost 8 GHz. Local oscillator power requirements are about 1 μW for mixers made by photolithography and are about 100 nW for mixers made by e-beam lithography. The studies in terahertz receivers based on HEB superconducting mixers now present a dynamic, rapidly developing field.     

Quantum-noise theory for terahertz hot electron bolometer mixers

In this paper, we first review general quantum mechanical limits on the sensitivity of heterodyne receivers. The main aim of the paper is to explore the quantum-noise (QN) properties of hot electron bolometric (HEB) mixers. HEB mixers have a characteristic feature not found in other mixers: based on the "hot-spot" model, the conversion loss varies along the length dimension of the bolometer, and some sections of the bolometer are essentially passive, in which little frequency conversion occurs. We analyze a quantitative distributed quantum-noise model of the HEB mixer, making use of simulated hot-spot model data, that takes into account the continuous variation of the sensitivity along the bolometer bridge. An expression for the HEB receiver noise temperature, including optical input loss, is derived. We find that the predicted double-sideband receiver noise temperature agrees well with the available measured data (up to 5.3 THz). The results of our analysis suggest that QN and classical HEB noise contribute about equally at 3 THz, while at higher terahertz frequencies QN dominates. QN thus appears to show measurable effects in existing HEB mixers and will be even more important to take into account as HEB mixers continue to be developed for higher terahertz frequencies.     

Crystal Checker for Balanced Mixers

To achieve optimum performance from a microwave receiver that uses a balanced crystal mixer, matched pairs of crystals should be used. However depending on the reason for choosing the balanced mixer for a particular receiver, the crystal characteristics that should be matched and the degree of balance that is required vary considerably. The three principal reasons for using balanced mixers are: 1. To minimize noise figure by suppressing local-oscillator noise. 2. To suppress local-oscillator power radiation. 3. To reduce receiver sensitivity to certain spurious responses. For radar receivers, the first reason is the only important one, and fortunately it places the least stringent requirement on the degree of balance.     

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.     

Frequency-shifting submillimeter single-sideband receiver

A single sideband (SSB) receiver has been developed and implemented for use with a submillimeter sideband generator. While the sideband generator emits both an upper and lower sideband, and even some unshifted laser radiation, the receiver responds to only one sideband. The operator of the system can choose which sideband to receive. Rejection of the undesired signal is accomplished through selective frequency shifting coupled with the use of a commercially available single-sideband microwave mixer.     

A 1-THz superconducting hot-electron-bolometer receiver for astronomical observations

In this paper, we describe a superconducting hot-electron-bolometer mixer receiver developed to operate in atmospheric windows between 800-1300 GHz. The receiver uses a waveguide mixer element made of 3-4-nm-thick NbN film deposited over crystalline quartz. This mixer yields double-sideband receiver noise temperatures of 1000 K at around 1.0 THz, and 1600 K at 1.26 THz, at an IF of 3.0 GHz. The receiver was successfully tested in the laboratory using a gas cell as a spectral line test source. It is now in use on the Smithsonian Astrophysical Observatory terahertz test telescope in northern Chile.     

A New Microwave Radiometer Simultaneously Receiving Dual-Polarized Radiation

A new cost-effective microwave radiometer has been designed for simultaneously receiving both vertically and horizontally polarized thermal radiation, which are important signals for improving the capability of passive remote observations of geophysical phenomena. It is basically a Dicke-switched superheterodyne receiver whose both polarization channels share a single set of a reference noise source, a low-noise microwave amplifier, and a mixer with a local oscillator by adopting a scheme that both channels are slightly spaced in receiving frequency. A 15-GHz band radiometer has been built and tested for the verification of this scheme.     

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.     

Quasi-optical slot antenna SIS mixers

A quasi-optical SIS mixer designed for efficient radiation coupling is described. The mixer uses a twin-slot antenna which has the advantages of a good beam pattern and a low impedance. The radiation and impedance characteristics of the antenna were obtained from a moment-matched calculation. Tapered superconducting microstrip transmission lines are used to carry the radiation from the slot antennas to the tunnel junction. The effective impedance seen by the tunnel junction is quite low, about 4 Ω, which allows micron-size junctions to be used at 500 GHz. The mixers have been fabricated using Nb/Al-oxide/Nb tunnel junctions and a receiver noise temperature of 420 K (DSB) was measured at 490 GHz, which is the best yet obtained for a quasi-optical mixer at this frequency. The comparatively large junction area increases the mixer saturation power and allows strong suppression of noise from the Josephson effect by the application of a magnetic field of modest strength     

380GHz 辐射计前端关键技术研究

辐射计是一种用于测量物体热辐射的高灵敏度接收机,是被动微波遥感的主要工具。辐射计前端作为辐射计系 统的重要组成部分,其性能直接影响系统的指标。本文介绍一种380GHz 辐射计前端关键技术的设计,包括380GHz 分谐 波混频器及作为本振驱动的190GHz 三倍频器。其中380GHz 分谐波混频器在2.5~3.5GHz 中频输出频率范围内实测变频 损耗低于10dB,均值为9dB;等效噪声温度达到1300K,均值约为2000K。190GHz 三倍频器已完成仿真设计,在190GHz 频率点倍频效率大于25%,输出功率约18mW,在183~193GHz 的频带范围内,输出功率大于5mW。     

Quantum noise in heterodyne detection

A fully quantum mechanical theory of diode mixers which includes quantization of the external circuit is presented. We find that Tucker's theory for SIS mixer conversion efficiencies is correct, but that his expression for the measurement noise must be augmented by an amount corresponding to half a photon at every frequency to which the mixer responds. Noise in high quality SIS mixers is shown to be accurately described by the conceptually simpler photodiode mixer noise theory. The radiation coupling efficiency term, η, which appears in photodiode theory turns out to be the coupling efficiency between the signal source admittance and the admittance which the SIS presents to the LO. Our theory reduces to Caves' quantum linear amplifier formalism, and therefore predicts measurement noises bounded by the quantum lower limit ofhv/k_{B}. Predictions of performance versus frequency for SIS's are made. We predict that NbN SIS's will behave as nearly ideal photodiodes for frequencies as high as 3000 GHz.     

A 220 GHz Single-Chip Receiver MMIC With Integrated Antenna

This letter presents the design and characterization of a 220 GHz microstrip single-chip receiver monolithic microwave integrated circuit (MMIC) with an integrated antenna in a 0.1 mum GaAs metamorphic high electron mobility transistor technology. The receiver MMIC consists of a novel slot-square substrate lens feed antenna, a three-stage low noise amplifier, and a sub-harmonically pumped resistive mixer. The receiver MMIC is mounted on a 12 mm silicon substrate lens which focuses the radiation from the calibration loads to the on-chip antenna through an opening in the backside metallization of the MMIC. The double sideband noise figure of this quasioptical receiver is as low as 8.4 dB (1750 K) at 220 GHz including the losses in the antenna and in the lens. To the best of the authors' knowledge, this work demonstrates the highest integration level versus operating frequency for a MMIC ever published, regardless of technology.     

Low-Power 2.4-GHz Transceiver With Passive RX Front-End and 400-mV Supply

An ultra low power 2.4-GHz transceiver targeting wireless sensor network applications is presented. The receiver front-end is fully passive, utilizing an integrated resonant matching network to achieve voltage gain and interface directly to a passive mixer. The receiver achieves a 7-dB noise figure and -7.5-dBm IIP3 while consuming 330 muW from a 400-mV supply. The binary FSK transmitter delivers 300 muW to a balanced 50-Omega load with 30% overall efficiency and 45% power amplifier (PA) efficiency. Performance of the receiver topology is analyzed and simple expressions for the gain and noise figure of both the passive mixer and matching network are derived. An analysis of passive mixer input impedance reveals the potential to reject interferers at the mixer input with characteristics similar to an extremely high-Q parallel LC filter centered at the switching frequency     

A V-band quasi-optical GaAs HEMT monolithic integrated antenna and receiver front end

A single-chip monolithic integrated V-band folded-slot antenna with two Schottky-barrier diodes and a local oscillator source is developed as a quasi-optical receiver for the first time. The monolithic microwave integrated circuit consists of a voltage-controlled oscillator (VCO), a coplanar waveguide (CPW)-to-slotline transition, a low-pass filter, a folded-slot antenna, and a 180/spl deg/ single balanced mixer. The chip is fabricated based on the 0.15-/spl mu/m GaAs high electron-mobility transistor technology and the overall chip size is 3/spl times/1.5 mm/sup 2/. A finite-difference time-domain method solver is also developed for analyzing the embedded impedance characteristics of the folded-slot antenna to design the mixer. The chip is placed on an extended hemispherical silicon substrate lens to be a quasi-optical receiver. The performance of the receiver is verified by experimental measurements. The VCO has achieved a tuning range from 61.9 to 62.5 GHz and approximately 9.3-dBm output power. The CPW-to-slotline transition has bandwidth from 50 to 70 GHz. The mixer results in 15-dB single-sideband conversion loss and the receiving patterns of the IF power are also measured.     

Ku频段谐波混频器的研制

叙述了一种可用于Ku频段微波接收机的谐波混频器的原理、设计、仿真及实验结果.该混频器主要由Lange耦合器、输入、输出滤波器以及匹配网络等部分组成.实验结果表明,在14.00～14.25GHz的频率范围内变频损耗的实测曲线与仿真曲线基本吻合,带内幅度平坦度优于1dB,驻波比小于2.