J. P. Pascual

The Quijote CMB Experiment

We present the current status of the QUIJOTE (Q-U-I JOint TEnerife) CMB Experiment, a new instrument which will start operations early in 2009 at Teide Observatory with the aim of characterizing the polarization of the CMB and other processes of galactic and extragalactic emission in the frequency range 10–30GHz and at large angular scales. QUIJOTE will be a valuable complement at low frequencies for the PLANCK mission, and will have the required sensitivity to detect a primordial gravitational-wave component if the tensor-to-scalar ratio is larger than r = 0.05.

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.

Harmonic-balance analysis and synthesis of coupled-oscillator arrays

A new harmonic-balance technique for the analysis and synthesis of coupled-oscillator systems with adjustable phase progression is presented here. It allows an accurate determination of the phase-shift versus the tuning elements, since detailed models are used for the individual oscillator circuits. It is also possible to impose the synchronization frequency at which the in-phase oscillation takes place and calculate the values of the tuning elements for a pre-fixed phase distribution. The phase noise of the system is analyzed through the carrier modulation approach. The phase-change rapidity versus a control voltage is analyzed through the envelope-transient method. A four-element oscillator array at 5 GHz has been designed through this method and experimentally characterized obtaining very good agreement with the simulation results.

Low-noise monolithic Ku-band VCO using pseudomorphic HEMT technology

A low-noise pseudomorphic HEMT Ku-band oscillator with varactor frequency tuning and voltage power control is reported. The circuit size, including the varactor and the pads for on-wafer testing, is less than 0.7 mm/sup 2/. On-wafer oscillator measurements show a frequency tuning bandwidth of 600 MHz centered at /spl sim/15.2 GHz and an output power up to 17 dBm with more than 15 dB of power control. Phase noise of -87 dBc/Hz at 100 kHz has been obtained, which is an excellent result for a fully monolithic integrated Ku-band voltage-controlled oscillator (VCO).

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.

Low-noise Ku-band MMIC balanced P-HEMT upconverter

An enhanced design methodology for a low-noise Ku-band monolithic balanced high electron mobility transistor (HEMT) upconverter and its performance are presented in this paper. The mixer topology consists of a common source/common gate HEMT pair that performs the mixing and balun functions. A detailed study has been done to establish the role of the transistor model elements in the performance of the mixer. Based on this study, a new analysis is proposed to optimize the operating point of the mixer in order to get a tradeoff between conversion gain and port isolations. To combine the LO and intermediate-frequency (IF) signals, active circuits were used, as well as a high-pass filter in order to improve the isolations. The circuit size, including the filter and the combiners, is 3 mm/sup 2/. On-wafer measurements show a conversion gain over 2.5 dB, with only 3 dBm of LO power. A LO/RF isolation over 27 dB was measured in the whole LO band. The LO/IF isolation is over 27 dB thanks to the low reverse gain of the combiner HEMTs. A single sideband noise figure of 7.3 dB has been obtained.

CHARACTERIZATION AND MODELING OF SCHOTTKY DIODES UP TO 110 GHZ FOR USE IN BOTH FLIP-CHIP AND WIRE-BONDED ASSEMBLED ENVIRONMENTS

This paper presents a wideband model, from Direct Current (DC) to W band, for a single Anode Schottky Diode based on a commercial VDI chip. Difierent measurements have been performed to obtain a complete large-signal equivalent circuit model suitable for the device under consideration up to 110GHz, and for its integration in planar circuits. The modeling has been done using a combination of DC measurements, capacitance measurements, and RF scattering measurements. The test structure for on-wafer S- parameter characterization has been developed to obtain an equivalent circuit for Coplanar to Microstrip (CPW-Microstrip) transitions, then verifled with 3D Electromagnetic (EM) tools and flnally used to de- embed device measurements from empirical data results in W band. 3D EM simulation of the diodes was used to initialize the parasitic parameters. Those signiflcant extrinsic elements were combined with the intrinsic elements. The results show that the proposed method is suitable to determine parameters of the diode model with an excellent flt with measurements. Using this model, the simulated performance for a number of diode structures has given accurate predictions up to 110GHz. Some anomalous phenomena such as parasitic resistance dependence on frequency have been found.

System Simulation of a Differential Radiometer Using Standard RF-Microwave Simulators

A complete radiometer simulation framework with special emphasis on high frequencies and switched system performance is proposed. The simulation procedures have been tested on a system configuration used in a branch of the 30-GHz Planck Radiometer, which detects radiation from the cosmic microwave background in a window with 20% relative bandwidth centered at 30 GHz. The goal of the article is not to obtain detailed conclusions about this radiometer in particular but to test the viability of proposed techniques in a realistic context. Basic RF performance of an ideal and a more realistic version of the radiometer is compared. Furthermore, the whole system simulation is implemented in the frequency domain and the time domain, on the same platform that is used to design separate microwave components, introducing realistic parameters for the high-frequency components, such us measured S parameters of the amplifiers and measured current-voltage characteristics of the detectors.

Applications of Pulsed-Waveform Oscillators in Different Operation Regimes

In this paper, following previous works, a pulsed-waveform oscillator is made up of a feedback loop containing an amplifier stage and a nonlinear transmission line. Efficient simulation techniques are applied for the correction of waveform nonidealities. A global stability analysis of the pulsed-waveform oscillator is performed, considering two relevant circuit parameters. All the possible oscillation modes are taken into account in this analysis, with the aim to guarantee operation in the desired mode only. The jitter in the pulsed waveform is quantified with a phase-noise analysis, and the uncommon form of variation of the phase-noise spectral density is understood with the aid of a semianalytical formulation. The injection-locked operation of the pulsed-waveform oscillator is also investigated, examining its robustness and possible advantages and applications. In particular, we will consider the injection-locked mode at a subharmonic frequency and analyze the resulting phase-noise spectrum, which will be compared with that of the free-running pulsed-waveform oscillator. The application as a frequency multiplier will be considered. The techniques have been applied to a prototype at 1 GHz with very good agreement with the measurement results.

Simple nonlinearity evaluation and modeling of low-noise amplifiers with application to radio astronomy receivers

This paper describes a comparative nonlinear analysis of low-noise amplifiers (LNAs) under different stimuli for use in astronomical applications. Wide-band Gaussian-noise input signals, together with the high values of gain required, make that figures of merit, such as the 1 dB compression (1 dBc) point of amplifiers, become crucial in the design process of radiometric receivers in order to guarantee the linearity in their nominal operation. The typical method to obtain the 1 dBc point is by using single-tone excitation signals to get the nonlinear amplitude to amplitude (AM-AM) characteristic but, as will be shown in the paper, in radiometers, the nature of the wide-band Gaussian-noise excitation signals makes the amplifiers present higher nonlinearity than when using single tone excitation signals. Therefore, in order to analyze the suitability of the LNAs nominal operation, the 1 dBc point has to be obtained, but using realistic excitation signals. In this work, an analytical study of compression effects in amplifiers due to excitation signals composed of several tones is reported. Moreover, LNA nonlinear characteristics, as AM-AM, total distortion, and power to distortion ratio, have been obtained by simulation and measurement with wide-band Gaussian-noise excitation signals. This kind of signal can be considered as a limit case of a multitone signal, when the number of tones is very high. The work is illustrated by means of the extraction of realistic nonlinear characteristics, through simulation and measurement, of a 31 GHz back-end module LNA used in the radiometer of the QUIJOTE (Q U I JOint TEnerife) CMB experiment.