Bart Nauwelaers

Multilayer thin-film MCM-D for the integration of high-performance RF and microwave circuits

Thin-film multi-layer MCM-D technology using the system in a package concept is presented as a viable approach for the integration of high performance wireless front-end systems. Due to the high quality dielectrics and copper metallization, high quality transmission lines and inductors are available. This, together with the integrated passives design library containing scalable equivalent models for the inductors, capacitors, resistors, transmission lines and discontinuities, allows easy and accurate co-design between the passive and active devices. Examples of bandpass filters, power dividers, quadrature couplers, microwave feedthroughs, a DECT VCO and a 14 GHz LNA are given.

Mutual Coupling Reduction Between Planar Antennas by Using a Simple Microstrip U-Section

Mutual coupling is an inevitable phenomenon in multiantenna systems, usually reducing the system performance. Numerous works have focused on the reduction of this effect. The aim is maintaining the mutual coupling suppressing structure as simple as possible while having a high amount of mutual coupling reduction. This letter presents a novel structure suppressing the mutual coupling between nearby patches. It is composed of only a simple U-shaped microstrip, which reduces the mutual coupling considerably. The structure has been constructed and tested. The measurement results prove the high efficiency of this configuration.

Direct Extraction of the Non-Linear Model for Two-Port Devices from Vectorial Non-Linear Network Analyzer Measurements

Non-linear models for microwave and millimetre wave devices are commonly based on DC and S-parameter measurements, due to the absence of vectorial large-signal measurements in the past. At present, accurate prototype measurement systems are being developed, which implies that new non-linear modelling techniques can be explored. We will present a method that allows the direct extraction of the state-functions of a HEMT.

A wideband beamformer for a phased-array 60GHz receiver in 40nm digital CMOS

For high-data-rate wireless communication in the 7GHz band around 60GHz, the IEEE 802.15.3c standard [1] provides channels with a 0.88GHz bandwidth for the AV-OFDM mode. For the single-carrier modes, the ECMA 387 standard [2] foresees the possibility of bonding together adjacent channels, yielding higher data-rates. Radios for these 60GHz standards often use phased antenna arrays to relax the link budget. A phased-array receiver needs a variable phase shift on each antenna path and a combiner that sums the signals from the individual paths after phase shifting. The beamforming circuitry presented here handles 4 paths. It can operate both with one 0.88GHz channel and with bonding of two such channels. Phase shifts are realized with a resolution better than 20°. Bandwidth is high thanks to the use of current amplifiers with very low input impedance.

Wavelet packet based multicarrier modulation

A recent but already popular technique for broadband communications is multicarrier modulation, which divides the channel into several orthogonal, overlapping subchannels. Multicarrier modulation is normally implemented using a Fourier transform to create and detect the different subcarriers. This can be efficiently implemented using an (I)FFT. This transform however has the drawback that it uses a rectangular window, which creates rather high sidelobes. This leads to rather high interference when the channel impairments cannot be fully compensated. Looking at other transforms leads us to the wavelet transform, and more specifically the wavelet packet transform, which has more flexibility and due to the time-overlap can have much lower sidelobes. This article studies the implementation of these wavelet packets, and the effects this implementation has on the requirements imposed in the design of usable wavelets. It is shown that the restrictions imposed by the perfect reconstruction requirement necessitate the use of biorthogonal wavelets. This however influences the performance. Moreover, the frequency behaviour of the wavelet packet transform is not straightforward which limits the practical use of this transform in a multicarrier system.

An electrostatic fringing-field actuator (EFFA): application towards a low-complexity thin-film RF-MEMS technology

This paper presents a novel electrostatic actuator using fringing fields as the actuation mechanism, i.e. an electrostatic fringing-field actuator or EFFA. The novel device is produced on an insulating substrate in a simple two-mask process involving only one sacrificial layer and one metallization. To demonstrate the EFFA capabilities, we produced and characterized EFFAs in various technological implementations of remarkable simplicity. This simplicity allows a vast flexibility for the processing and as a result strongly eases the integration of the EFFAs into existing technologies. For the basic device, we report a non-de-embedded measured capacitance ratio of 1:3 and a lifetime of more than 107 cycles with 40 V bipolar actuation at 100 Hz in N2 atmosphere. Both the capacitance ratio and the C–V profile were tuned by modifying the technology, e.g. coating the substrate before processing the EFFAs and the design, e.g. switching from clamped-free to clamped–clamped devices. We finally report a complete RF-MEMS technology using the EFFAs as single actuators. Switchable and tunable LC tanks, phase shifters, series and shunt parallel-plate capacitors actuated as relays and capacitive relays are presented to demonstrate the possibilities of this technology.

A smart wearable textile array system for biomedical telemetry applications

A smart wearable textile array system (SWTAS) with direction of arrival (DoA) estimation and beamforming is proposed and developed for biomedical telemetry applications. This conformal system enables effective and continuous patient monitoring when combined with one or more health sensors, as information about the subjects health condition is received adaptively to guarantee link reliability. This operation is facilitated by a receiver front-end and a digital baseband beamforming network, which enables scalability and flexibility. The proposed SWTAS also features flexible antenna arrays made using textiles, which are arbitrarily located on a cylindrically shaped body phantom to ensure wide spatial DoA estimation capability. Besides being designed to suit on-body placement, the system performance is also characterized for on-body usage using a commercial body-emulating liquid, and placed at a realistic distance from the body, considering user clothing. Investigation indicated a good performance in the systems ±80° forward plane with a DoA accuracy of 3° . Finally, a practical evaluation is presented using two transmitters placed at distinct locations and distances. The system successfully estimated both DoAs and received the telemetry signals using beamforming.

A simple error correction method for two-port transmission parameter measurement

This letter presents a simple error correction method for two-port transmission parameter measurement. The method requires measuring only two nonreflecting transmission lines instead of a complete set of calibration standards (at least three) for error correction, it does not need an explicit solution of error coefficients. These two features make it simpler than any other methods. Error-corrected measurement results of a CPW discontinuity using the new method and the TRL method are in good agreement. The new method is useful in characterizing well-matched two-port devices or those whose reflection parameters are of little interest.

50-to-67GHz ESD-protected power amplifiers in digital 45nm LP CMOS

Research in recent years has shown that downscaled CMOS is a serious technology candidate to implement transceivers for high-data-rate wireless communication around 60GHz [1,2]. A low-cost implementation is the combination of the digital part with the transceiver onto a single chip. The complexity of the digital part demands a very advanced CMOS technology, such as 45nm low-power (LP) CMOS. Although this technology features a high maximum ƒT, above 200GHz, the back-end-of-line (BEOL) metallization layers are thinner than in less-advanced technology. This implies a lower quality factor for the passive components and a lower intrinsic ESD robustness due to a higher sheet resistance of the metal layers. These restrictions, together with the limited power capabilities of CMOS make the design of mm-wave power amplifiers (PAs) more challenging [3,4].

S‐parameter measurement based quasistatic large‐signal cold HEMT model for resistive mixer design

The nonlinear cold HEMT model generation procedure is described. It starts with the determination of the corresponding small-signal model by adapting the cold FET extraction approach for HEMTs. Then, the small-signal model is transformed to obtain a straightforward implementable, consistent small-signal cold HEMT model, suitable for resistive mixer design.