Markus Robens

Continuous-Time Quadrature Bandpass Sigma-Delta Modulator for GPS/Galileo Low-If Receiver

In this paper, starting from theoretical considerations on the chosen architecture, chip design and measurement results are presented for a continuous-time quadrature bandpass sigma-delta (SigmaDelta) modulator for a combined GPS and Galileo low-IF receiver. The modulator chip was designed in a standard 0.25 mum CMOS technology. The designed CT quadrature bandpass SigmaDelta modulator has a power consumption of 20.5 mW with 1.8-V supply voltage, a dynamic range of 57.5 dB and 50.2 dB and a peak SNDR of 52.9 dB and 48.4 dB for GPS/Galileo, respectively. The core area of the chip is 0.37 times 0.54 mm2.

Differential Noise Figure De-Embedding: A Comparison of Available Approaches

A new matrix-based approach for de-embedding the noise figure of a differential device has been recently presented. In this paper, an enhancement to this method will be provided. The new method will be compared to state-of-the-art approaches. For comparison, measurements have been performed on an amplifier with distinct transfer characteristics. The respective integrated circuit is composed of two single-ended amplifiers placed in close proximity within the layout. Due to capacitive cross-couplings arising from this arrangement, the differential noise figure is degraded compared to the single-ended one, which indicates the requirement of differential excitation. For completion, measurements have also been performed on a differential device. A commercially available evaluation board has been used for this purpose and measurement results agree well with those specified by the manufacturer.

A Polyphase Filter Design for Continuous-Time Quadrature Bandpass Sigma–Delta Modulators

This paper presents a strategy for successful polyphase-filter design for continuous-time quadrature bandpass sigma-delta (SigmaDelta) modulators. Based on a low-pass filter with a chain of integrators with weighted capacitive feedforward summation (CICFF) topology - which is suited for implementation in low-power applications - analytical equations are derived. A new compensation scheme is proposed and implemented by cross-coupling additional resistors, without the necessity of extra-active components. Translation to intermediate frequency in second- and fourth-order polyphase filters with the proposed compensation scheme are compared to analytical considerations and simulation. Nonlinearities introduced by mismatch of feedforward coefficients and finite gain-bandwidth of amplifiers are considered.

Differential noise figure measurement: A matrix based approach

In this paper, a new matrix-based approach for differential noise figure measurement will be presented. Passive components used for embedding a differential device into a single ended test setup are characterized by their noise correlation matrices. Then, signal transfer via the component chain is described by chain matrices. Determining the output referred noise correlation matrix of the device under test this way, a noise figure can be denoted.

Sallen-Key polyphase filter design

Present wireless receiver designs often make use of low intermediate frequency structures for signal reception. These topologies frequently apply polyphase filters for noise and image signal attenuation. When using active-RC implementations of single pole or direct synthesis structures, the number of operational amplifiers and thus power consumption becomes high. To confine the latter, a Sallen-Key based polyphase filter is presented in this paper which reduces the amplifier amount by one half. Furthermore, the system theoretic method used for circuit design is shown. Results are verified by Cadence simulation.

UWB LNAs for ground penetrating radar

Two LNA topologies for use in UWB systems are examined and compared in this paper. Design specifications have been derived from a ground penetrating radar system which is the target application. Circuits have been designed to cover the frequency range from 3.1GHz to 10.6 GHz. The SiGe:C technology SGB25V of IHP Microelectronics is applied to enable volume production at low prices. For measurement purposes, input and output are matched to 5Ω.

Performance limitation by finite gbw in continuous-time quadrature bandpass sigma-delta modulators

Continuous-time quadrature bandpass sigma-delta modulators seriously suffer from finite gain bandwidth of the amplifiers they contain. In this paper, the performance limitation of the continuous-time quadrature bandpass sigma-delta modulator caused by finite gain bandwidth is presented. Finite gain bandwidth results in an unstable behavior of the complex integrators and a deviation from the center frequency. In order to improve stability of the complex integrator by finite GBW, it is desirable to employ a lossy integrator. The deviation from the center freqency affects the in-band noise power of the modulator. A compensation solution for reducing the deviation from the center frequency is proposed by means of transconductors at the amplifier inputs.

HaLoS – Integrated RF-Hardware Components for Ultra-Wideband Localization and Sensing

Ultra-Wideband (UWB) sensors exploit very weak electromagnetic waves within the lower microwave range for sounding the objects or processes of interest. The interaction of electromagnetic waves with matter provides interesting options to gain information from a great deal of different scenarios. To mention only a few, it enables the assessment of the state of building materials and constructions, the investigation of biological tissue, the detection and localization of persons buried by rubble after an earthquake or unauthorized people hidden behind walls, and much more [1]. The advantage of such methods consists in their non-destructive and continuously running measurement procedure which may work at high speed and in contactless fashion.

System simulation for M-sequence radar sensors

Capabilities of M-sequence radar front-ends have been shown in the past. For further system enhancement, specifications of constituent components can be re-aligned using system simulation. In this article, we want to present a system simulation setup for Agilents Advanced Design System (ADS) which allows us to assess the impact of individual components on typical radar parameters. The latter characterize the performance of the overall system and it is their optimization which is targeted. For this purpose, new ADS stars, i.e. components for the (timed) synchronous dataflow (TSDF) simulator, have been implemented. Appropriate antenna models have been identified from literature and the signal deformations they impose are clearly visible from the simulated impulse response. Thus, simulations help to determine the antenna type suitable for the application. Due to the multiple signal domain simulation ability of ADS Ptolemy, it can be switched from a pure model based simulation to a transient-TSDF co-simulation during the design process. Using an appropriate channel model, such simulations provide a good estimate of real system performance right in advance to the actual component implementation and they help to keep track of real components agreement with the predicted behavior. Thus, a fair amount of flexibility is added in the design process compared to the former real-circuit component based approach.

Capacitive crosscoupling biquad polyphase filter

In this paper, the design of biquad polyphase filters with capacitive crosscouplings is presented. Based on the elementary equation s → s - j wc, which describes the frequency shifting, system theoretic modeling is used for design. Some important observations simplifying the design process are denoted. The developed structures have been simulated in Cadence using operational amplifier models with adjustable gain and bandwidth. Results are compared to those of a Tow-Thomas polyphase filter with comparable sum capacitance but with an operational amplifier amount twice as high. By limiting the gain bandwidth product of the models to reasonable values it is shown that operational amplifier performance does not need to be improved and hence a reduced power consumption can be expected.