%0 Journal Article
%T Downconverting Module Architectures for High Performance Multipixel Cameras
%A Diego Palombini
%A Maciej Jankowski
%A Ernesto Limiti
%J International Journal of Microwave Science and Technology
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/586158
%X Multipixel cameras represent an emerging topology for arrays receivers, improving speed and accuracy of both security scanning systems and radioastronomical sky surveys by means of a matrix of phased elements. Difficulties in the generation and proper distribution to each pixel of the local oscillator signal still limit their use to frequency ranges below a few GHz or at least seriously affect the complexity of the implementable cameras. This work presents a full comparison between two possible system architectures, alternatively based on LO frequency multiplication or subharmonic mixing strategies, aiming to overcome the aforesaid limitations: design and performance of two compact test vehicles in MMIC technology, both operating in the Q-band frequency range with ultrabroadband IF section, are reported. 1. Introduction Array receivers have been adopted since the beginning of the 90¡¯s in radioastronomical applications [1] and, more recently, in security scanning systems, improving active and passive millimetre-wave imaging capabilities [2]. In radioastronomical applications, this kind of receivers is usually placed at the focus of a large radiotelescope antenna and it is mainly used to survey large areas in a more efficient way than single-pixel receivers. Array receivers can be roughly classified into three different types: focal plane arrays (FPAs), which incorporate distinct superheterodyne receivers performing a spectroscopic analysis of the incoming signal; bolometric arrays (BAs), achieving an integral measure of the total channel power; phased array feeds (PAFs) consisting of a matrix of receiving elements fed by the same local oscillator and then digitally combined [3]. Major research efforts are currently devoted to the latter receiver architecture, exhibiting two key advantages over conventional multibeam horn feeds: firstly it enables the radiotelescope to support many simultaneous beams on the sky, thus increasing the instrument speed; secondly, it offers the opportunity to properly shape the pattern of the feed array in order to match the optical configuration of the telescope [4]. The major drawback of a PAF, often limiting its use for frequency ranges above a few GHz, is however the necessary requirement of distributing the same LO signal to each pixel, without loss of synchronism between different paths; the research for new circuit topologies allowing to overcome this limitation represents the main purpose of this work. Possible strategies have the common feature of reducing the main local oscillator operating frequency, thus
%U http://www.hindawi.com/journals/ijmst/2013/586158/