Maarten Strackx

Measuring material/tissue permittivity by UWB Time-domain Reflectometry techniques

A model for simulating reflections of ultrawideband (UWB) pulses in multilayered tissue structures, has been implemented and verified using commercially available software. The permittivity of the different layers was altered sequentially and the corresponding reflections have been analyzed. Building on these experiments, the use of pulsed UWB is envisaged for the in-vivo measurement of complex tissue permittivity, in a non invasive way. Eventually, we will apply this technique to radiotherapy, trying to correlate the changes in permittivity with the absorbed radiation dose. A measurement setup using Time-Domain Reflectometry (TDR) is proposed.

Ultra-wideband antipodal vivaldi antenna array with Wilkinson power divider feeding network

In this paper, a two element antipodal Vivaldi antenna array in combination with an ultra-wideband (UWB) Wilkinson power divider feeding network is presented. The antennas are placed in a stacked configuration to provide more gain and to limit cross talk between transmit and receive antennas in radar applications. Each part can be realized with standard planar technology. For a single antenna element, a comparison in performance is done between standard FR4 and a Rogers® RO3003 substrate. The antenna spacing is obtained using the parametric optimizer of CST MWS®. The performance of the power divider and the antenna array is analyzed by means of simulations and measurements.

Direct RF Subsampling Receivers Enabling Impulse-Based UWB Signals for Breast Cancer Detection

The implementation of a Direct RF subsampling receiver in CMOS is presented for the application of breast cancer detection using impulse-based ultrawideband (UWB) signals. Such a receiver inherently benefits from CMOS scaling since its speed-accuracy tradeoff depends only on technological process parameters. With a proper choice of antenna matching media, the current signal processing requested resolution could be translated into feasible hardware specifications. The track-and-hold (T/H) circuit is analyzed and implemented in a 40-nm chip since this block must cope with the full RF BW. An effective resolution BW of 5.5 GHz was measured with an accuracy of 6 b for rail-to-rail input signals. Second, a two-stage Miller compensated fully differential difference amplifier is discussed with low input parasitics (10 fF) to enable measurements without limiting the performance.

A 6-b UWB subsampling track & hold with 5.5-GHz ERBW in 40 nm CMOS

This paper presents an ultra wideband track and hold (T/H) circuit using direct RF subsampling for radar applications. The circuit enables digitization of the whole received UWB pulse instead of a sole distance measurement used in correlating receivers. In this way, more target information is acquired for further digital processing. Subsampling was applied to achieve a low power concumption of 1.4 mW which includes the T/H core and clock generator. The circuit operates on a rail-to-rail input using the bootstrapping technique. To avoid reliability issues caused by bootstrapping the sampling switch, bulk switching and precharge techniques are introduced. An effective resolution bandwidth of 5.5-GHz was measured with an accuracy of 6-b. The track and hold circuit has been implemented in 40 nm CMOS.

A 20Gbps 1.2GHz full-duplex integrated AFE in 28nm CMOS for copper access

A 28nm CMOS 1.2GHz full-duplex analog front end (AFE) is presented. The AFE can deliver 20Gbps of aggregate service across 50m of RG6 coax. The on-chip line driver, powered from a 7.2V supply and using core transistors, delivers 5.9Vptp differential to the line through the hybrid. A tunable capacitive hybrid circuit for full duplex operation is proposed for low noise performance and allows channel matching. A cancellation of 23.1dB on average is achieved across the full band. A 3-stage receiver with input over-voltage protection is capable of driving 50Ω differential loads. The chip occupies 0.28mm2 of active area and consumes 1.53W.

A 36.4dB SNDR @ 5GHz 1.25GS/s 7b 3.56mW single-channel SAR ADC in 28nm bulk CMOS

A 1.25GS/s 7b single-channel SAR ADC is presented with an SNDR/SFDR of 41.4dB/51dB at low frequencies, while the SNDR/SFDR at Nyquist are 40.1dB/52dB and remain still 36.4dB/50.1dB at 5GHz. The high input frequency linearity is enabled by a fast bootstrap circuit for the input switch, while the high sampling rate, the highest among recently published >34dB SNDR single-channel SAR ADCs is achieved by a Triple-Tail dynamic comparator and a Unit-Switch-Plus-Cap (USPC) DAC. The prototype ADC in 28nm CMOS consumes only 3.56mW from a 1V supply, leading to a Walden FoM of 34.4fJ/conv-step at Nyquist for a core chip area of 0.0071mm2.

Experimental validation of a compact model for EM reflection and transmission in multi-layered structures

A model for calculating the reflection and transmission of electromagnetic (EM) waves through multi-layered structures has been realized and experimentally verified. This model can be used in ultra-wideband (UWB) systems to determine the composition of a multi-layered structure. Both models (S11 and S21) are implemented using matlab and verified for common multi-layered structures with both commercially available CST design studio simulations and measurement results. The outputs of these models are further used to determine the minimum DR (dynamic range) of the receiver, needed to find the composition of the proposed structures.