Receiver architecture of the thousand-element array (THEA)

As part of the development of a new international radio-telescope SKA (Square Kilometre Array), an outdoor phasedarray prototype, the THousand Element Array (THEA), is being developed at NFRA. THEA is a phased array with 1024 active elements distributed on a regular grid over a surface of approximately 16 m2. The array is organised into 16 units denoted as tiles. THEA operates in the frequency band from 750 to 1500 MHz.\ud On a tile the signals from 64 antenna elements are converted into two independent RF beams. Two times 16 beams can be made simultaneously with full sensitivity by the real-time digital beam former of the THEA system. At the output of each tile the analog RF signal from a beam is converted into a 2 × 12-bit digital quadrature representation by a receiver system.\ud A double super-heterodyne architecture is used to mix the signal band of interest to an intermediate frequency of 210 MHz. The IF-signal is shifted to baseband by means of a partly digitally implemented I/Q mixer scheme. After a quadrature mixer stage, the I and Q signals are digitised by means of 12 bit A/D converters at 40 MS/s. Implementing a part of the mixing scheme digitally offers the flexibility to use different I/Q architectures, e.g. Hartley and Weaver mixer setups. This way the effect of RFI in different mixing architectures can be analyzed. After the digital processing, the samples are multiplexed, serialised and transported over fibres to the central adaptive digital beam former unit where the signals from all tiles are combined giving 32 beams.\ud This paper focuses on the design choices and the final implementation of the THEA system. In particular, the receiver architecture is addressed. A digital solution is presented, which enables switching between a Hartley and a Weaver based mixer scheme

Computation of finite array effects in the framework of the square kilometer array project

The Square Kilometer Array (SKA) is a very large radio telescope being planned by an international consortium. It would operate in a very broad frequency band and have a collecting area of one square kilometer. In order to achieve a good resolution, this area will be spread over a few tens of stations, located several tens or hundreds of kilometers apart. The Netherlands Foundation for Research in Astronomy (ASTRON) is studying the possibility of covering the mid-range frequencies (~0.2 to 2 GHz) with an instrument based on the phased-array technology. This technology presents the major advantages of avoiding mechanically moving structures and of enabling very flexible beamforming. One of the envisaged broadband antenna elements is the tapered slot antenna, also called Vivaldi antenna. The design of these antennas is based on infinite array models, which automatically include the mutual coupling effects. As each station will probably be made of a very large number of small arrays, it is important to know how these arrays will behave when they are truncated. We developed a computation scheme for arrays of antennas made of metallic fins. We justify the adopted approach, then details are given for the fast resolution of the resulting equation system. Finally, examples are shown for wide dipoles and comments are made about the extension to Vivaldi antenna

Multi-Mode Antennas for Ultra-Wide-Angle Scanning Millimeter-Wave Arrays

In this paper, a novel multi-mode millimeter-wave antenna array with enhanced scan range and reduced scan losses is presented. The individual array element consists of a differentially fed microstrip patch on top of which a cylindrical dielectric resonator is integrated. The radiation pattern of the antenna element can be reconfigured by changing the phase offset between the feeding ports of the patch and the dielectric resonator to excite two distinct radiating modes. With such a feature, the field of view can be divided into two different subspaces, with the first one covering the angular range from -75to 0and the second one from 0to +75. In a 1 × 16 linear array configuration, the achieved scan range extends from -75to 75along the horizontal plane with a maximal gain loss of 3 dB, which is better than the ideal cos θ0 behavior. The proposed design operates in the frequency range between 27 GHz and 29.5 GHz and, thanks to its wide-scan capabilities, constitutes an effective solution for upcoming 5G/6G millimeter-wave wireless communications

BiCMOS high-performance ICs : from DC to mm-wave

Progress with silicon and silicon germanium (SiGe) based BiCMOS technologies over the past few years has been very impressive. This enables the implementation of traditional microwave and emerging mm-wave applications in silicon. The paper gives an overview of several high-performance ICs that have been implemented in a state-of-the-art BiCMOS technology (QUBiC4). Examples of high-performance ICs are described ranging from basic building blocks for mobile applications to highly integrated receiver and transmitter ICs for applications up to the mm-wave range

BiCMOS high-performance ICs: From DC to mm-wave

Progress with silicon and silicon germanium (SiGe) based BiCMOS technologies over the past few years has been very impressive. This enables the implementation of traditional microwave and emerging mm-wave applications in silicon. The paper gives an overview of several high-performance ICs that have been implemented in a state-of-the-art BiCMOS technology (QUBiC4). Examples of high-performance ICs are described ranging from basic building blocks for mobile applications to highly integrated receiver and transmitter ICs for applications up to the mm-wave range