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Abstract-A new architecture of mutually coupled regenerative oscillators is presented. It has been used to design a lownoise high-frequency VCO capable of producing two output signals in quadrature with essentially identical properties. The phase relation between the quadrature outputs is frequency independent and extremely stable. A new way of coupling the regenerative oscillators is suggested in order to improve the frequency stability of the coupled oscillator system. Results obtained from a test chip have verified the viability of the new oscillator concept. The oscillator circuit has been realized in a medium-frequency (fT = 3 GHz) bipolar process. The tuning range extends to 500 MHz. At an oscillation frequency of 200 MHz, measured phase noise was -121 dBc/Hz at 1-MHz distance from the carrier.

Abstract-Recently new and interesting science drivers have emerged for very low frequency radio astronomy from 0.3 MHz to 30 MHz. However Earth bound radio observations at these wavelengths are severely hampered by ionospheric distortions, man made interference, solar flares and even complete reflection below 10 MHz. OL-FAR is Orbiting Low Frequency ARray, a project whose aim is to develop a detailed system concept for space based very low frequency large aperture radio interferometric array observing at these very long wavelengths. The OLFAR cluster could either orbit the moon, whilst sampling during the Earth-radio eclipse phase, or orbit the Earth-moon L2 point, sampling almost continuously or Earth-trailing and leading orbit. The aim of this paper is to present the technical requirements for OLFAR and first order estimates of data rates for space based radio astronomy based on the proposed scalable distributed correlator model. The OLFAR cluster will comprise of autonomous flight units, each of which is individually capable of inter satellite communication and down-link. The down-link data rate is heavily dependent on distance of the cluster from Earth and thus the deployment location of OLFAR, which are discussed.

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The past two decades have witnessed a renewed interest in low frequency radio astronomy, with a particular focus on frequencies above 30 MHz e.g., LOFAR (LOw Frequency ARray) in the Netherlands and its European extension ILT, the International LOFAR Telescope. However, at frequencies below 30 MHz, Earth-based observations are limited due to a combination of severe ionospheric distortions, almost full reflection of radio waves below 10 MHz, solar eruptions and the radio frequency interference (RFI) of human-made Email addresses: m.j.bentum@tue.nl (M.J. Bentum), m.k.verma@student.tudelft.nl (M.K. Verma), r.t.rajan@tudelft.nl (R.T. Rajan), boonstra@astron.nl (A.J. Boonstra), C.J.M.Verhoeven@tudelft.nl (C.J.M. Verhoeven), e.k.a.gill@tudelft.nl (E.K.A. Gill), a.j.vanderveen@tudelft.nl (A.J. van der Veen), h.falcke@astro.ru.nl (H. Falcke), m.kleinwolt@astro.ru.nl (M. Klein Wolt), b.monna@hyperiontechnologies.nl (B. Monna), s.engelen@hyperiontechnologies.nl (S. Engelen), j.rotteveel@isispace.nl (J. Rotteveel), lgurvits@jive.eu (L.I. Gurvits)

In this contribution we will provide an overview of the work that has been done on pulsar navigation and show a new direction in pulsar‐based navigation research. Up until now the focus has been on X‐ray pulsars, whereas our focus will be on the possibility of using radio pulsars. The radio frequency range has been neglected because the radio‐frequency pulses were assumed to be too weak to detect with antennas of a reasonable size. We will demonstrate that with a relatively small antenna radio pulses can be detected even on Earth. In our discussion we will make a comparison of pulsar navigation with GNSS and the differences are analyzed in a detailed discussion on both navigation methods.

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