Active load modules for W-band radiometer calibration

Weißbrodt, Ernst; Tessmann, A.; Schlechtweg, M.; Kallfass, Ingmar; Ambacher, O.

doi:10.1109/igarss.2012.6350708

Cited by 8 publications

(8 citation statements)

References 14 publications

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“…cov (v j (t j ) , T i (t i = t j )) = 0 (19) as v(t) = g(t)v (t) according to (10) in the article and it is assumed that no ambiguity present in the knowledge of T i 's. From Cases 1 and 2, one can conclude the generic expression for the covariance terms as follows: (13) In this appendix, the covariance terms in (7), i.e., cov(x m , x n ), where x's represent the voltages and temperatures in the calibration equation 4, are derived for AR(1) gain processes in the following cases.…”

Section: Appendix a Proof Of Equation (11)mentioning

confidence: 99%

Analysis of Nonstationary Radiometer Gain Using Ensemble Detection

Aksoy

Rajabi

Racette

et al. 2020

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Radiometer gain is generally a nonstationary random process, even though it is assumed to be strictly or weakly stationary. Since the radiometer gain signal cannot be observed independently, analysis of its nonstationary properties would be challenging. However, using the time series of postgain voltages to form an ensemble set, the radiometer gain may be characterized via radiometer calibration. In this article, the ensemble detection algorithm is presented by which the unknown radiometer gain can be analytically characterized when it is following a Gaussian model (as a strictly stationary process) or a 1st order autoregressive, AR(1) model (as a weakly stationary process). In addition, in a particular radiometer calibration scheme, the nonstationary gain can also be represented as either Gaussian or AR(1) process, and parameters of such an equivalent gain model can be retrieved. However, unlike stationary or weakly stationary gain, retrieved parameters of the Gaussian and AR(1) processes, which describe the nonstationary gain, highly depend on the calibration setup and timings. Index Terms-Autoregressive AR(1) model, ensemble detection, nonstationary radiometer gain, radiometer calibration. I. INTRODUCTION R ADIOMETERS are widely used to measure geophysical parameters to examine variations in the earth and planetary systems. These measurements typically need to be obtained over large temporal or spatial scales. However, enhanced radiometric accuracy and sensitivity are required in microwave radiometry, as an accurate radiometer facilitates the possibility of high-resolution contrasts in variations of physical parameters from the rest of the measured noise. For instance, the retrieval of geophysical parameters, such as precipitable water vapor, ocean surface salinity, wind measurements, and liquid and ice water paths require enhanced accuracy and finer resolution [1]-[5]. Thus, given the increasing importance of radiometer calibration in deriving greater geophysical information from Manuscript

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Section: Appendix a Proof Of Equation (11)mentioning

confidence: 99%

Analysis of Nonstationary Radiometer Gain Using Ensemble Detection

Aksoy

Rajabi

Racette

et al. 2020

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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“…Table 1 also shows an overview of the utilized transistor technologies for previous ACL designs. While InP HEMTs would be the technology of choice for lowest achievable noise temperature [7], GaAs mHEMTs are a lower cost alternative with equivalent performance [8, 13]. For this work, Fraunhofer IAFs in-house 50 nm mHEMT process was chosen.…”

Section: Metamorphic High Electron Mobility Transistor (Mhemt) Technomentioning

confidence: 99%

“…The transistors in both active loads are realized with a gate length of 2 × 15 µm. To verify the simulation approach, especially the noise prediction, the active loads were previously manufactured as stand-alone devices [13]. Except for the DC-routing, the cores of the active loads are identical to the ones seen in Fig.…”

Section: Circuit Designmentioning

confidence: 99%

W-band active loads and switching front-end MMICs for radiometer calibration

Weißbrodt

Schlechtweg

Ambacher

et al. 2013

Int. J. Microw. Wireless Technol.

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A millimeter-wave monolithic integrated circuit consisting of a W-band (75-100 GHz) single-pole-five-throw (SP5T) switch and multiple internal active and passive loads for radiometer calibration was designed and manufactured in a low noise 50 nm GaAs metamorphic high electron mobility transistor technology. This highly compact and integrated front-end device for radiometer systems is capable of ultra fast switching between two identical input ports (e.g. for polarimetric applications) and three internal calibration references. It allows an accurate multi-load calibration with noise temperatures between 220 and 1750 K at the output of the device. Compared to conventional calibration methods this marks a substantial advantage in terms of size, mass, power consumption, complexity, and repetition rate

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“…Low noise amplifiers based on high electron mobility transistors (HEMT) reach state-of-the-art low noise and high frequency performance [1,2,3]. While improvements in transistor technology reduce the achievable noise figure (Fmin) the input matching circuit of the amplifier still needs to present the optimum source impedance r OPT to the transistor in the fust stage of the amplifier to achieve noise figures as low as possible.…”

Section: Introductionmentioning

confidence: 99%