P. de Paco

Very low-noise differential radiometer at 30 GHz for the PLANCK LFI

The PLANCK mission of the European Space Agency is devoted to produce sky maps of the cosmic microwave background radiation. The low-frequency instrument is a wide-band cryogenic microwave radiometer array operating at 30, 44, and 70 GHz. The design, test techniques, and performance of the complete differential radiometer at 30 GHz are presented. This elegant breadboard 30-GHz radiometer is composed of a front-end module (FEM) assembled at the Jodrell Bank Observatory, Cheshire, U.K., and a back-end module assembled at the Universidad de Cantabria, Cantabria, Spain, and Telecomunicacio/spl acute/, Universitat Polite/spl acute/cnica de Catalunya, Barcelona, Spain. The system noise temperature was excellent, mainly due to the very low noise performance of the FEM amplifiers, which achieved an average noise temperature of 9.4 K.

Mutual coupling effects on antenna radiation pattern: An experimental study applied to interferometric radiometers

Antenna pattern mismatches are one of the most important error sources in planned Earth-observation interferometric radiometers. From a low Earth orbit, the wide field of view, about ±30°, leads to the use of antennas with a large beam. In addition, antennas must be closely spaced to avoid, or at least minimize, aliasing effects in the formation of the synthetic brightness temperature images. The accuracy demanded of these systems requires the precise knowledge of all the antenna radiation voltage patterns (amplitude and phase), which may differ from their theoretical values due to mechanical and electrical tolerances in the manufacturing process and which can change due to the proximity of other structures, i.e., other antennas of the array or the mechanical support. Two approaches are found in the literature to interpret the impact of antenna mutual coupling on the performance of an interferometric radiometer: (1) a modification of the antenna voltage pattern and (2) a mixing of the cross correlations measured between the signals collected by the antennas. The main contribution of the present work is a detailed theoretical analysis of the impact of mutual coupling effects showing the equivalence between both approaches. Theoretical results are corroborated with a set of experimental measurements with two kinds of antennas. Theoretical and experimental results can be used in the design of the antennas of interferometric radiometers in order to predict the impact of mutual coupling on the systems performance and point out the importance of an accurate antenna pattern characterization.

LFI 30 and 44 GHz receivers Back-End Modules

The 30 and 44 GHz Back End Modules (BEM) for the Planck Low Frequency Instrument are broadband receivers (20% relative bandwidth) working at room temperature. The signals coming from the Front End Module are amplified, band pass filtered and finally converted to DC by a detector diode. Each receiver has two identical branches following the differential scheme of the Planck radiometers. The BEM design is based on MMIC Low Noise Amplifiers using GaAs P-HEMT devices, microstrip filters and Schottky diode detectors. Their manufacturing development has included elegant breadboard prototypes and finally qualification and flight model units. Electrical, mechanical and environmental tests were carried out for the characterization and verification of the manufactured BEMs. A description of the 30 and 44 GHz Back End Modules of Planck-LFI radiometers is given, with details of the tests done to determine their electrical and environmental performances. The electrical performances of the 30 and 44 GHz Back End Modules: frequency response, effective bandwidth, equivalent noise temperature, 1/f noise and linearity are presented.

Branch-Line Coupler Based on Edge-Coupled Parallel Lines With Improved Balanced Response

A conventional branch-line coupler is flat-balanced, in terms of magnitude and phase, in a narrow frequency band due to the quarter-wave length requirement in the transmission lines. In this paper, a novel branch-line structure is presented in order to overcome this limitation. Loading the horizontal transmission lines with a pair of open-end series stubs, the magnitude and phase balance becomes flatter in a wider frequency range. However, the proposed structure cannot be fabricated, for which an equivalent circuit using edge-coupled parallel lines has been used. The measurement of this device shows a relative bandwidth of 82.5% for 2 dB magnitude and 72% for plusmn5deg phase balance condition.

A Split-Ring-Resonator Loaded Monopole for Triple Band Applications

A monopole loaded with a split-ring resonator (SRR) will be presented for applications requiring efficient triple-band performance. The design is based on the principle of non-resonant traps and takes advantage of the dual-band behavior of the SRR. The mid-band frequency is mainly controlled by the dimensions of the monopole whereas the frequencies of the lower and upper bands are determined by the resonances of the SRR. As proof of concept, an antenna covering the universal 802.11 standard (2.4–2.5 GHz and 4.9–5.875 GHz) and the low band of the 802.15 standard (3.244–4.742 GHz) has been designed, fabricated and measured.

Dual-Band Mixer Using Composite Right/Left-Handed Transmission Lines

The concept of composite right left-handed transmission lines provides for one additional degree of freedom in realizing arbitrary dual-band frequency response devices. In this letter, an arbitrary dual-band operation mixer, based on the classical balanced mixer topology is proposed. The prototype demonstrates the mixer performance for a ratio of 2.5 between the two operation bands (860 MHz and 2,150 MHz). The conversion losses are better than 8.5 dB in both bands.

Closed-Form Expressions for the Design of BAW CRF Acoustic Inverters

A bulk acoustic wave coupled resonator filter is a device in which two thin film bulk acoustic wave resonators are stacked on top of each other separated by a set of passive layers which control the degree of acoustic interaction between resonators contributing to the conformation of the radiofrequency passband response. The set of passive layers implements an impedance inverter which has to fulfill the desired coupling value. The variation of the acoustic lengths of the coupling layers gives the degree of freedom to implement the desired inverter. In this work, a set of closed-form expressions are provided to obtain the coupling layers thicknesses without any time-consuming optimization procedure. The provided solution gives an explanation to the underlying fundamentals that take place in a successful optimization procedure.

Double-Ladder Filter Topology for a Dual-Band Transmission Response Based on Bulk Acoustic Wave Resonators

Filters based on bulk acoustic wave resonators present very good performance, small size and compatibility with IC technology. However, the traditional configurations present only one frequency transmission band. In this work, a configuration based on electrically coupled BAW resonators has been developed in order to obtain a dual-band response, where each of these bands can be allocated at a desired frequency. In order to validate the proposed topology, a filter response using measured resonators is shown.

Analysis Technique for Asymmetrically Coupled Resonator Structures

Asymmetrical acoustically coupled structures are present in several acoustic applications. Specifically when they are used in filter design, some configurations provide unexplored and special response characteristics with high selectivity and relatively wide bandwidths. The relationships between geometries, configurations, and response specifications do not rely on a direct link. In this work, a novel approach to the analysis of these structures is presented as well as a model of an asymmetrical bulk acoustic wave coupled resonator filter obtained from the analysis presented.

Design of Three-Pole Bulk Acoustic Wave Coupled Resonator Filters

The control of longitudinal coupling in bulk acoustic wave (BAW) resonators makes it possible to design multilayer coupled resonator filters (CRF) with a desired response. This paper presents the methodology to face this kind of designs with a set of closed-form expressions that allow to control the coupling between resonators, and to determine the structure geometry of a three-pole CRF. A network transformation from the Mason model to an equivalent electric circuit makes it possible to apply the insertion loss filter design method. An UMTS RF filter has been designed using the proposed methodology.