R.H. Witvers

Low cost low noise phased-array feeding systems for SKA pathfinders

Developments in radio astronomy instrumentation drive the need for lower cost front-ends due to the large number of antennas and low noise amplifiers needed. This paper describes cost reduction techniques for the realization of antennas and low noise amplifiers in combination with a noise budget calculation for array systems in the absence of cryogenic cooling.

Noise characterization of ultra low noise differential amplifiers for next generation radiotelescopes

This paper describes the design of two ultra low noise amplifiers in a differential configuration for radioastronomy applications and the characterization of the noise performance with hot/cold-methods.

Achieving Wideband sub-1dB Noise Figure and High Gain with MOSFETs if Input Power Matching is not Required

A 0.18 mum CMOS low noise amplifier (LNA) achieves sub-1 dB noise figure over more than an octave of bandwidth without external noise matching components. It is designed for a future radio telescope, requiring millions of cheap LNAs mounted directly on phased array antenna elements. The short distance between antenna and LNA and low frequency below 2 GHz allows for using an LNA with reflective input impedance, increasing the gain with 6 dB. Without any matching network, very low noise figure is achieved over a wide bandwidth. At 90 mW power, sub-1 dB Noise is achieved for 50 Omega source impedance over a 0.8-1.8 GHz band without external coils, and S21>20 dB, OIP2>25 dBm and OIP3>15 dBm. Preliminary results with 150 Omega source impedance show noise temperatures as low as 25 K around 900 MHz.

Improved sensitivity of a low noise aperture array tile for the SKA

Aperture array technology is one of the candidate technologies for the 500 MHz to 1500 MHz frequency range of the SKA. The feasibility and low noise potential of aperture arrays have been demonstrated with small test systems before, e.g. with a 50 K system noise temperature, measured on a 1 m2 prototype tile in 2010. However, further reduction of the array noise temperature is essential to optimize the ratio of effective collecting area and system noise temperature. This is made possible by applying new, lower noise, technology to the LNA design. Thus the sensitivity requirement for the Mid Frequency Aperture Array of the SKA could be satisfied at lower cost. Results of a step by step approach to reduce the system noise temperature to below 40 K, giving at least 20% improvement, are presented.

State of the art MMIC InP LNA realizations and applications in FARADAY array receivers

Historically radio telescope have mostly consisted of large dishes with a single feed system at the focus. Recently there has been a trend towards multi-beam systems to make more efficient radio maps of the sky. Three teams, funded under the EU FARADAY project, have designed receiver arrays developed using the lattice-matched indium phosphide foundry process of NGC, California. Receiver architecture and measured results are described

Decade Wide Bandwidth Integrated Very Low Noise Amplifier

This paper describes the design, realization and characterization of an integrated Low Noise Amplifier (LNA) with a bandwidth from 0.4 to 8 GHz. A very good noise figure is achieved in this frequency band. The design uses a source impedance of 150 ohm in the contrary to the standard of 50 ohm. The load impedance is 50 ohm. The use of a non-50 input source impedance creates new possibilities for the design of the power and noise matching circuitry. A combination of a good power and noise match can be achieved for a very broad band, with a minimum of components. This concept requires a non-standard antenna (source) output impedance (150 ohm), which is for most antenna principles easier to realize then 50 ohm [1]. The LNA will be part of an active antenna phased array system, which should operate from 0.2 to 2 GHz [2].

A Wideband Low Noise Tile for the SKA Mid Frequency Aperture Array

Recent experimental results for the sensitivity of aperture arrays at room temperature show 40 K array noise temperatures over the frequency range from 1000 MHz to 1500 MHz. Further reduction of array noise temperature is important to comply with the SKA sensitivity requirements at affordable cost. Furthermore the frequency range should be extended to a lowest frequency of 500 MHz, in order to meet the bandwidth specification for the future SKA Mid Frequency Aperture Array. The work presented here builds on our earlier published results, obtained with aperture arrays for the frequency range from 1000 MHz to 1500 MHz. Noise measurements with a 2×2 array using newly designed broadband antenna/LNA modules, show a further reduction in noise temperature to 35 K and below for this frequency range. At the same time the new design has a much broader frequency response, down to 600 MHz, with an array noise temperature near 40 K. These noise measurements could be done despite the harsh RFI environment, of which the influence on the design will be discussed. The results of the presented noise measurements are state-of-the-art for a room temperature system in the 600-1500 MHz frequency range.

Integrated Active Antenna Noise Figure Characterization Using a Cryogenic Anechoic Noise Source

For the phased array concept of the next generation radio telescopes, the Square Kilometre Array (SKA), a large number of broadband, low noise amplifiers are necessary. The envisaged array antennas for SKA are printed circuit type antennas (Vivaldy, bunny ear) Smolders (1), which should be integrated with the first amplifier stages. To enable optimum performance over a decade bandwidth it is advantageous to directly match the antenna impedance to the required impedances for low noise matching and maximum power transfer of the active device, without an intermediate matching step to 50 ohm as is common for most microwave and RF systems. This paper describes the design, but more importantly the characterization, of the integrated active antenna. An accurate characterization of e.g. noise figure cannot be executed with standard equipment due to the non-50 ohm intermediate impedance levels. To overcome this problem, a hot/cold noise figure measurements has been developed for the complete active antenna.

Mid frequency aperture array technology developments for the SKA

This paper describes the technology developments of antenna arrays for the mid frequency instrument of the Square Kilometre Array radio telescope.

Front-End Integration Requirements for the Square Kilometre Array Radio Telescope

Integration technology is discussed for the realization of a square kilometre radio telescope and in particular the Low Noise Amplifier (LNA). Very low noise figures with a room temperature LNA of sub 0.2dB have been achieved with 70nm mHEMT technology.