Volume 66, Issue 11-12 - GEMIC 2012

This paper presents a study on the trade-off between the envelope's slew-rate and the drain efficiency when slower envelopes are considered to dynamically supply the power amplifier (PA). This paper discusses a method to limit the slew-rate (and consequently the bandwidth) of the signal's envelope. Moreover, since the envelope tracking (ET) technique using a slower version of the original envelope introduces nonlinear distortion, slow envelope dependent predistortion has to be also incorporated in the design of ET PAs. Experimental results showed that it is possible to find a compromise between the bandwidth and slew-rate reduction (necessary to cope with the specific envelope amplifier requirements) and the amount of drain efficiency degradation suffered due to the use of a slower version of the original envelope.

This paper presents the design and results of a four-antenna integrated receiver (RX) frontend in 0.25 µm SiGe BiCMOS. It performs antenna combining in the radio-frequency (RF) domain with IEEE 802.11a compliant signals. Therefore, the RF part of this integrated circuit (IC) includes four low noise amplifiers (LNAs), vector modulators (VMs) and a signal combiner. These circuits can weight the incoming C-band (5.6 GHz) signals in their I- and Q-components with an 8-bit resolution before superposition and downcoversion. The baseband (BB) part of the applied zero-IF architecture integrates an 8 th order switched-capacitor (SC) filter for channel selection and variable gain amplifiers (VGAs) for automatic gain control (AGC). Together with digital control logic the power consumption amounts to 350 mW at an area requirement of 7.5 mm 2 .

An investigation of GaN-HEMT based switching stages in hybrid switching amplifiers (HSA) for wide-bandwidth supply modulation of RF power amplifiers is presented. The HSA is designed for maximum 15 V supply voltage, 1 A supply current and 10 MHz bandwidth. GaN-HEMT switch designs with alternative gate drive circuitry are investigated with regard to power, efficiency and linearity under different load conditions using simulations and measurements of the fabricated circuits. The full HSA showed an efficiency of 49.7% for a WCDMA envelope. A modified switching stage with improved gate-drive circuitry shows 85% efficiency in a 15 V buck-converter test-circuit for a 10 V conversion at 1 MHz over a 15 Ω load.

A 4 × 4 reconfigurable switch matrix based on low temperature co-fired ceramic technology for Geo-stationary satellite mission at Ka-band downlink frequencies (17–22 GHz) is presented. In comparison to its predecessor, the new generation of switch-matrix features augmented functionality whilst an overall reduced size (40%). The distinguished characteristics include the shifting of matching networks from top-layer into the embedded layers of the multilayer ceramic stack and the elimination of two external peripherals required to digitally control the bipolar current sources of the PIN-diodes based switch integrated circuits. As an additional functionality, four passive transparent paths between corresponding input and output are integrated within the module, to exhibit rudimentary transmission through the module in case of on-board power failure.

We have developed a compact, high-performance, mechanically robust reconfigurable microwave switch matrix as well as peripheral components such as diode driver, voltage controlled oscillator, and power detector modules for satellite applications using the low temperature co-fired ceramics technology (LTCC) and hybrid integration of integrated circuits. In order to verify the technology for space applications, we combined these components to build a system that enables automated verification of the switch matrix in space, accounting for power consumption, mass, overall geometrical dimensions, and mechanical robustness. The system passed a full space qualification. During a one year On-Orbit-Verification (OOV) mission aboard the German test satellite TET-1 (technology evaluation carrier) launched on July 22, 2012, the correct operation and reliability of the entire switch matrix system and thereby the used technology will be demonstrated.

In this paper, we introduce a precise real-time 3D indoor localization concept using a combination of the MISAS (multilateral inverse synthetic aperture secondary radar) approach and SMCM (sequential Monte Carlo method). The synthetic aperture approach is a promising locating technique with effective multipath suppression. However, its practical use is restricted by the huge computational load of the reconstruction algorithms. We use a weighted-particle set – which we reduce subsequently by resampling – to represent the PDF (probability density function) instead of the highly complex, standard, grid-based approach. Simulation runs and experiments, carried out with a 5.8 GHz FMCW secondary radar system with a bandwidth of only 140 MHz, show that a robot TCP (tool center point) can be localized in 3D in the mm-range using a few hundred particles and operating in a dense multipath environment. This novel extension is a promising solution for real-time, 3D MISAS localization applications.

Detection of pedestrians in an urban environment is a highly sophisticated task. This paper presents a signal processing technique suitable for frequency-modulated continuous wave (FMCW) radar sensors using chirp sequence modulation, allowing observation of slow-moving objects with high resolution capability in range and velocity. Velocity resolution can be improved through auto-regressive linear prediction (AR-LP) without requiring a long chirp sequence duration. Furthermore, the influence of the frequency deviation used and velocity resolution will be shown in a scenario with two objects. An adaptive velocity resolution improvement will be presented to extract a characteristic micro-Doppler signature (µD-signature) of a slowly moving pedestrian, a car, and an inline-skater. This is verified by measurements at the carrier frequency of 77 GHz.

This paper presents a method for the moisture determination of small and irregularly shaped objects independent from their shape and orientation. The objects under test are illuminated by UWB-pulses and the scattered pulses are received by an array of antennas. A dedicated measurement set-up and time domain transmission instrument is proposed. The scattered pulses contain information about the geometric as well as the dielectric properties. In order to separate this information multivariate calibration is applied. The time domain data is therefore subjected to principal component regression, partial least squares regression and an artificial neural network. All calibration methods deliver excellent performance. The moisture content of the objects can be determined with an accuracy of prediction of 0.69% while the range of moisture is within about 5% to 24%.

Electromagnetic ultra-wideband (UWB) sensing and imaging provide perspectives for early-stage breast cancer detection. This paper deals with practical challenges of real measurements. We present an experimental setup for breast phantom trials based on M-sequence radar technology and short active dipole antennas. It combines short impulse responses, appropriate fidelity and very small antenna dimension and allows array construction with sufficient number of antennas around the breast. The basic approach and obtained imaging results are presented. Furthermore, in this extended paper version continuative development steps are described and measurement results reflecting specific performance aspects are discussed.