5thEngWorkshop Abstracts Final

5th RadioNet-FP7

Engineering Forum Workshop

Receiver Gain Stability

Osservatorio Astronomico di Cagliari

Cagliari, Italy

12 – 13 May 2011

5th Engineering Forum Workshop


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Agenda

12th May 2011

13.00 – 14:00 Lunch at the Hotel Regina Margherita

14.30 – Departure of the bus to SRT from the hotel Regina

15.30 – 17.30 Visit at the radio telescope site (SRT)

18.30 Arrival to the hotel

20.00 Dinner



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13th May 2011

09.00 – 09.30 Registration

09.30 – 09.40 Welcome and Introduction R. Keller (MPIfR, DE),

09.40– 10.20 Mechanisms of 1/f noise and Gain Instabilities in metamorphic HEMTS D. Bruch (IAF, DE)

10.30 – 11.00 Gain Fluctuations of Cryogenic Amplifiers J.D. Gallego Puyol (OAN, ES)

11.10 – 11.40 Coffee Break

11.40 – 12:10 Receiver chain: Typical Gain drift and instabilities and their causes S. Mariotti (INAF-IRA, IT)

12.15 – 12.55 Precision Continuum Receivers for Astrophysical Applications E. Wallack (NASA, USA)

13.05 – 14.30 Lunch

14.30 – 15.10 Stability of the IRAM receiver P. Serres (IRAM, FR)

15. 20 – 15.50 Added Phase Noise measurement for Local Oscillator distribution systems G. Bianchi (INAF-IRA, IT)

16.00 – 16.30 Coffee Break

16.30– 17.00 Using High performance LNAs with cost-effective HEMTs in Radio-Astronomy Receivers M. Bergano (Instituto de Telecomunicações, PT)

17.10 – 17.40 Low frequency noise measurements in direct detection radiometers E. Artal (Universidad de Cantabria, ES)

17.50 –18.00 Conclusions R. Keller (MPIfR, DE)



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Participants List

1. Artal Eduardo Universidad de Cantabria, Spain

2. Bergano Miguel Instituto Telecomunicaçõe, Portugal

3. Bianchi Germano INAF- IRA, Italy

4. Bolli Pietro INAF – OAC, Italy

5. Bruch Daniel IAF, Germany

6. Ciccognani Walter University of Rome Tor Vergata, Italy

7. Colangeli Sergio University of Rome Tor Vergata, Italy

8. Cremonini Andrea INAF IRA, Italy

9. Gallego Puyol Juan Daniel OAN, Spain

10. Gaudiomonte Francesco INAF OAC, Italy

11. Keller Reinhard MPIfR-Bonn, Germany

12. Kirves Petri Metsähovi, Finland

13. Lew Bartosz Nicolaus Copernicus University, Poland

14. Limiti Ernesto University of Rome Tor Vergata, Italy

15. Locci Daniele Universita di Cagliari, Italy

16. Mariotti Sergio INAF-IRA, Italy

17. Monni Marco Institute Astronomical Observatory of Cagliari, Italy

18. Navarrini Alessandro INAF-Cagliari Astronomy Observatory, Italy

19. Orfei Alessandro INAF IRA, Italy

20. Palombini Diego University of Rome Tor Vergata, Italy

21. Pinna Andrea Università di Cagliari, Italy

22. Pisanu Tonino INAF – OAC, Italy

23. Possenti Andrea INAF – Osservatorio di Cagliari, Italy

24. Patrice Serres IRAM, France

25. Serra Giampaolo SRT, Italy

26. Türk Senner MPIfR-Bonn, Germany

27. Valente Giuseppe INAF-OAC, Italy

28. Watts Galen NRAO, USA

29. Wollack Edward NAS - Goddard Space Flight Center, USA

30. Wilkinson Peter University of Manchester, United Kingdom



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ABSTRACTS



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Mechanisms of 1/f noise and Gain Instabilities in metamorphic HEMTS

Daniel Bruch; M. Seelmann-Eggebert Fraunhofer Institute for Applied Solid State Physics, Germany

E-Mail: [email protected]

Abstract

Due to their excellent noise and high frequency performance, High Electron Mobility Transistors (HEMTs) based on InP or GaAs are the devices of choice for radiometers in a large variety of frequency bands. Upon cooling to cryogenic temperatures the noise temperature further decreases substantially without a reduction of device functionality. Owing to these properties cutting edge receivers as required in radio astronomy are built from these devices. Major limitations of low noise amplifiers for radio astronomic applications are given by 1/f noise and gain instabilities. This presentation aims to correlate the well-known effect of empirically observed 1/f noise and gain instabilities with physical mechanisms and model concepts.



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Gain Fluctuations of Cryogenic Amplifiers.

Juan Daniel GALLEGO Observatorio Astronomico Naciona, Spain


Abstract

Cryogenic amplifiers used either in the front end (cmWave) or in the IF (mmWave) of Radio Astronomy receivers are known to be important contributors to the overall gain stability of the receiving system. In the past decades we have witnessed a remarkable evolution in transistor technology, increasing the cut-off frequency and lowering the noise temperatures of the devices. However, the reduction of the device dimensions and the use of sophisticated HEMT heterostructeres have resulted in an increase of the gain fluctuations. This talk will address several aspects related with this topic:

• Specification of gain fluctuation of cryogenic amplifiers in the time and frequency domain:

SNGF and Allan Variance • Limitations of the measurement systems and attainable sensitivity • Experience in recent projects: factors affecting gain stability and statistics.



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Receiver chain:

Typical Gain drift and instabilities and their causes.

Sergio Mariotti INAF - Ist. di Radioastronomia, Italy


Abstract

The talk will analyze the typical causes of power level drift of the whole receiving chain. An estimate of the amount of the drift will be shown by every part. It will be focused on the behaviour of the drift along the time scale and along the temperature. It will be showed, as some popular instability measurement methods can be insensitive in certain context.



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Precision Continuum Receivers for Astrophysical Application

Edward Wollack NASA Goddard Space Flight Center, USA


Abstract

Cryogenically cooled HEMT (High Electron Mobility Transistor) amplifiers find widespread use in radioastronomy receivers. In recent years, these devices have also been commonly employed in broadband receivers for precision measurements of the Cosmic Microwave Background (CMB) radiation. In this setting, the combination of ultra-low-noise and low-spectral-resolution observations reinforce the importance achieving suitable control over the device environment to achieve fundamentally limited receiver performance. The influence of the intrinsic amplifier stability at low frequencies on data quality (e.g., achievable noise and residual temporal correlations), observational and calibration strategies, as well as architectural mitigation approaches in this setting will be discussed. The implications of device level 1/f fluctuations reported in the literature on system performance will be reviewed.



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Stability of the IRAM receiver

Patrice Serres IRAM, France


Abstract

The presentation first deals with the importance of receiver stability for Astronomical observations. The measurement method of the stability of output power and phase will be discussed. Measurement results will be presented for the following receivers developed at IRAM: SIS ALMA Band 7 (275-370GHz), SIS EMIR and 3mm HEMT both installed on the Pico Veleta 30 m telescope. At last, we will discuss the two main causes of instabilities: the voltage fluctuations intrinsic to the power supplies and the temperature variations of the active devices.



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Added Phase Noise measurement for Local Oscillator distribution systems

Germano Bianchi 1, S. Mariotti 1, J. Morawietz 2

(1) INAF - IRA, Italy; (2) ASTRON (The Netherlands) E-Mail: [email protected]

Abstract

New generation radio telescopes will be composed of antenna arrays consisting Vivaldi aerials, parabolic dishes, dipoles or similar, connected to heterodyne receivers. This makes it possible to convert the radiofrequency signal to the baseband frequency. Therefore the system needs mixers and local oscillators (LOs). The LOs have to be distributed from a synthesizer to several mixers using amplifiers and power splitters. The drift as well the noise of both the amplitude and the phase of LOs will generate pointing noise, lack of correlation etc. In order to guarantee the synchronization of different signals received from the antennas, the stability of the phase is extremely important. For this reason, measurements of the phase noise have been performed. The most important property is the additive (residual) phase noise: it allows us to understand the real contribution of the amplifiers and power splitters to the systems phase noise. In order to determine the total contribution of the LO distribution chain, the absolute (total) phase noise and AM to PM conversion (phase modulation) have been measured.



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Using High performance LNAs with cost-effective HEMTs in Radio-Astronomy Receivers

Miguel Bergano

Instituto Telecomunicacoes, Portugal


Abstract

In the context of the Galactic Emission Mapping, a new receiver at 10 GHz is proposed. It will characterize the galactic foreground to the Cosmic Microwave Background Radiation. This is a 10 GHz super heterodyne polarimeter, using the latest RF technology with a 1 GHz bandwidth that feeds a digital correlator. This thesis proposal describes the strategy to be used in the implementation of a very fast digital back-end – 32 Gbps - based in a FPGA and in new interface techniques. An approach to novel design techniques of low noise amplifiers will be abroad.

The paper describes the project, implementation and test of a C-band (5GHz) Low Noise Amplifier (LNA) using new low noise Pseudomorphic High Electron Mobility Transistors (pHEMTS) from Avago. The amplifier was developed to be used as a cost effective solution in a receiver chain for Galactic Emission Mapping (GEM-P) project in Portugal with the objective of finding affordable solutions not requiring strong cryogenic operation, as is the case of massive projects like the Square Kilometer Array (SKA), in Earth Sensing projects and other niches like microwave reflectometry. The particular application and amplifier requirements are first introduced. Several commercially available low noise devices were selected and the noise performance simulated. An ultra-low noise pHEMT was used for an implementation that achieved a Noise Figure of 0.6 dB with 13 dB gain at 5 GHz. The design, simulation and measured results of the prototype are presented and discussed.



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Low frequency noise measurements in direct detection radiometers

E. Artal, B. Aja, J. Cagigas, J.L. Cano, L. de la Fuente, A. Pérez, E. Villa

Universidad de Cantabria, Santander, Spain E-Mail: [email protected]

Abstract Low frequency noise measurement methods based on signal analyzers or in a Lock-In Amplifier (LIA) system have been used to achieve high sensitivity tests of detected signals in millimeter wave (30 GHz) direct detection radiometers. A typical range for a low frequency noise test is from 100 mHz to 1 kHz, that is sufficient to measure the 1/f behavior at very low frequencies and the white noise flat spectral density at higher frequencies. The noise floor of the LIA system is typically about -200 dBm/Hz at 1 kHz, much lower than the noise floor of a signal analyzer of about -165 dBm/Hz at the same frequency. Broadband millimetre wave radiometers are commonly used in Cosmic Microwave Background radiotelescopes operating at 30 and 40 GHz bands, with bandwidths of the order of 20% or 30%. These receivers have very low noise cryo-amplifiers, followed by a back-end module at room temperature to provide further amplification, band pass filtering and direct detection to DC by Schottky diode detectors. Output detected signals are amplified by low noise video amplifiers prior to their acquisition and digital processing.

Added noise by all reception chain components is present at video amplifier output as a demodulated or detected noise. Low frequency noise power spectral density is extremely important in such direct detection radiometers, because the presence of 1/f behavior puts a limitation in the systematic effects, which are not possible to cancel by signal processing methods. Knee frequency of 1/f noise spectrum in a millimeter wave (30 GHz) radiometer can be around 10 or 20 Hz.

In the workshop a comparison between the measurement systems based on signal analyzers or in a Lock-In Amplifier system will be presented. As an example the figure on the left shows the power spectral density at the output of a direct conversion radiometer (30 GHz band). Red line: tested noise. Blue line: signal analyzer noise floor. Different contributions to the 1/f noise behavior from the different radiometer chain subsystems will be presented.

This work has been funded by the Spanish Ministerio de Ciencia e Innovación, under the Astronomy and Astrophysics Program, grant reference: AYA2010-21766-C03-03.



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POSTERS

A design tool developed for the design of LNA. Marco Monni

Astronomical Observatory of Cagliari, Italy E-Mail: [email protected]

Abstract In the design of microwave low noise amplifiers, the designer must satisfy different goals simultaneously: gain, bandwidth, noise, insertion and return loss. As the number of equations is usually larger than the number of unknowns becomes difficult to satisfy all the constraints at the same time. In order to find a good compromise then is necessary a large number of simulations and tests based on classical try and error procedure. The tool developed at O.A.C is based on generating a set of design charts (The Solution Space) that allow the designer to keep the view all the variables simultaneously and quickly see the boundaries within which it is possible to get a good compromise for the different design constraints .This general Algorithm is based on the S-parameters method then It is independent by both frequency range and technology used. The application of Space Solution Charts can be applied also to design of others microwave components also oscillators.

Methods and notices of gain stability of Metsähovi receivers

Petri Kirves Metsähovi Radio Observatory, Finland


5thEngWorkshop Abstracts Final

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