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A wideband (30% relative bandwidth) correlation and detection module based on substrate-integrated waveguide (SIW) technology intended for a radio astronomy polarimeter is presented. The SIW circuit is a six-port network with two input ports that are correlated in two hybrid couplers and their corresponding output signals are routed to Schottky diode detectors, which are designed using microstrip technology and assembled within the same system. The designed SIW structure includes hybrid couplers, power dividers, a 90° phase shifter, and 90° bends, providing a real implementation of a functional system with improved bandwidth performance from 35 to 47 GHz. Experimental results are in concordance with simulations, and they validate the module operation for the proposed application. [ABSTRACT FROM AUTHOR]

Manufacture and in-service assessment of composite materials can be challenging since there is, yet, no standard method for testing them. Nevertheless, regular inspection is necessary to maintain the structural integrity. This paper describes a nondestructive, broadband noise mapping method that uses a millimeter-wave radiometer to detect defects in composite materials. The $W$ -band system is configured for transmission mode measurement in which an amplified photonic source illuminates a glass fiber reinforced polymer containing machined defects. A high sensitivity radiometer is used for imaging the sample. The radiometer consists of a Schottky diode-based frequency tripler and a fundamental mixer. [ABSTRACT FROM AUTHOR]

A multichannel radiometer frontend, which can improve the radiometer sensitivity and utilization of the frequency band dramatically, is proposed based on the principle of bandwidth synthetic technology. The multichannel radiometer, called multichannel bandwidth synthetic radiometer (MCBWSR), consists of multiple conventional radiometer channels, and the frequency bands of all the channels are synthesized by the bandwidth synthesizer before the detector. The synthesized bandwidth of the synthesizer can reach a maximum of the sum of all the bandwidths. The operating frequency can also be selected flexibly using the frequency conversion technology. An analysis of the sensitivity \Delta Tsyn of the MCBWSR is deduced in terms of the conventional single-channel radiometer sensitivity \Delta Ti . The relationship of sensitivity between the conventional single-channel radiometer and MCBWSR is validated using an RF simulator. To verify the analysis, three experiments are implemented on a direct detection radiometer, a heterodyne radiometer, and a dual-channel bandwidth synthetic radiometer (DCBWSR) receiver, respectively. The experimental results are presented, and the sensitivity among them is compared. These results indicate that the DCBWSR can improve the sensitivity by about 1/\sqrt 2 , which is consistent with the theoretically calculated results. Compared with the conventional radiometers, the MCBWSR has the advantages of higher sensitivity, lower power consumption, and integration. [ABSTRACT FROM AUTHOR]

A D-band SiGe HBT total power radiometer is reported with a peak responsivity of 28 MV/W, a noise equivalent power (NEP) of 14–18 \fW/Hz^1/2, and a temperature resolution better than 0.35 K for an integration time of 3.125 ms. The 1/f noise corner of the radiometer is lower than 200 Hz. Fabricated in a developmental technology with 270-GHz fT and 330-GHz fMAX, it includes a five-stage low-noise amplifier (LNA) with 4–7-GHz bandwidth and over 35 dB of gain centered at 165 GHz, along with a square-law detector with an NEP below 6 \pW/Hz^1/2 up to 170 GHz. An average system noise temperature of 1645 K is obtained using the Y-factor method and a noise bandwidth of 10 GHz calculated from the measured S21(f) characteristics of the radiometer. The reduced 1/f noise corner frequency in the presence of the amplifier, compared to that of the detector, appears to indicate that, unlike in III–V radiometers, LNA gain fluctuations are not a problem in SiGe HBT radiometers. The circuit consumes 95 mW and occupies \ 765\,\times\ 490∼\mu\ m^2. Wafer mapping of the radiometer sensitivity and of the amplifier gain was performed across different process splits. The mapping results demonstrate that the radiometer can be employed as a relatively simple and area-efficient transistor noise-measure monitor, useful in SiGe HBT vertical profile optimization. [ABSTRACT FROM AUTHOR]

Currently, graphene is a topic of very active research fields from science to potential applications. For various RF circuit applications, including low-noise amplifiers, the unique ambipolar nature of graphene field-effect-transistors can be utilized for high-performance frequency multipliers, mixers, and high-speed radiometers. Potential integration of graphene on silicon substrates with CMOS compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene MOSFETs to minimize parasitics and improve gate modulation efficiency in the channel with zero or a small bandgap. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antennas, where its success depends on the quality of materials. We also attempt to discuss future applications and challenges of graphene. [ABSTRACT FROM AUTHOR]

In this study, we report the results of short- and intermediate-term stability at L-band of an active cold load (ACL) realized with an SiGe heterojunction bipolar transistor. A noise injection radiometer has been developed to perform the measurements. A noise-equivalent delta temperature of less than 40 mK and a stability estimated to 30 mK during 90 s were obtained from Allan variance analysis. The results indicate that the variations of the ACL noise temperature correspond to the sensitivity of the measurement system. No drift was detected over one week of continuous characterization indicating that this kind of active load is very stable. [ABSTRACT FROM AUTHOR]

This paper describes the design and measurement of a wideband (W-band) passive radiometer chip developed in a standard 0.12-µm SiGe BiCMOS technology (IBM8HP, ƒt/ƒmax = 200/265 GHz). Design equations, simulations, and measurements are presented for a 94-GHz square-law detector and wideband low noise amplifier, and an 80-110-GHz single-pole double-throw switch. A total-power radiometer is presented, which can achieve a temperature resolution of ≈0.69 K (30-ms integration time) with periodic calibration or chopping above 10 kHz. A switched Dicke radiometer chip is also presented, which addresses the 1/ƒ noise of the total-power radiometer, and can achieve a temperature resolution of 0.83 K with a 30-ms integration time. This performance is comparable to current III-V imaging modules, and demonstrates, to our knowledge, the first implementation of a SiGe or CMOS W-band radiometer on a single chip. [ABSTRACT FROM AUTHOR]

Passive millimeter-wave systems have been used in the past to remotely map solid targets and to measure low-pressure spectral lines of stratospheric and interstellar gases; however, its application to pressure-broadened spectral line detection of industrial emissions is new. We developed a radiative transfer model to determine feasibility and system requirements for passive millimeter-wave spectral detection of terrestrial gases. We designed and built a Dicke-switched multispectral radiometer in the 146-154-GHz band to detect nitric oxide (NO), a prototypical gas of nuclear fuel processing operations. We first tested the spectral detection capability of the radiometer in the laboratory using a gas cell and then field tested it at the Nevada test site at a distance of 600 m from a stack that released hot plumes of NO and air. With features such as Dicke-switched integration, frequent online calibration, and spectral baseline subtraction, we demonstrated the feasibility of remote detection of terrestrial gases by a ground-based radiometer. [ABSTRACT FROM AUTHOR]

A monolithic load switching twist reflector (LSTR) has been built and tested for use in 94 GHz passive imaging cameras. In this paper, we describe the LSTR component, which switches between the dual roles of load comparison in a radiometer and reducing the length of the camera. Radiometric and quasioptical tests show that the array has an insertion loss of 0.25 dB and a switching ratio of >20 dB. This active array of p-i-n diodes can replace the mechanical choppers often used in load comparison. [ABSTRACT FROM AUTHOR]