Markus Allén

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Software-defined radio technology is experiencing more and more attention in modern communication and radar systems. The main practical challenge in deploying such technology is related to achieving sufficient linearity and spurious-free dynamic range in the RF front-end, especially in low-cost mass-product devices. This paper focuses on the analysis and(More)
This article focuses on the in-phase/quadrature (I/Q) imbalance problem in quadrature ΣΔ modulators (QΣΔM). In the literature, such quadrature modulators have been seen as a promising possibility for software defined radio (SDR) receivers, but matching the quadrature circuits is an inevitable problem for this kind of systems. In this article, an analytic(More)
A quadrature Σ∆ analog-to-digital converter (ADC) is a promising solution for intermediate frequency digitizing software defined cognitive radio (CR) receivers because of, e.g., multiband capability and power efficiency. However, inherent coefficient mismatches between the in-phase and quadrature rails can severely damage the performance of such receiver by(More)
This article discusses the applicability of quadrature ΣΔ modulator (QΣΔM) based analog-to-digital (A/D) conversion in cognitive radio (CR) receivers. First, unavoidable in-phase/quadrature (I/Q) mismatch effects, limiting the dynamic range, are analyzed in closed-form in the case of a first-order modulator. In addition, using the derived analytical(More)
Reliable spectrum sensing ability is a key factor in cognitive radios. However, there are many aspects that impact the sensing reliability. One important aspect is impairments in the cognitive radio receiver hardware. Received signals tend to have high dynamic range which drives the receiver to the nonlinear zone. This may cause nonlinear distortion falling(More)
In this article, the design and analysis of sophisticated multi-band quadrature ΣΔ modulators (QΣΔM) are addressed, offering a high-performance and easily-reconfigurable solution for the analog-to-digital (A/D) interface of cognitive radio receivers. Based on spectrum sensing information, the multi-band principle stemming from(More)
Wideband radio receivers provide the flexibility desired in many communications applications and are the key element in cognitive radios and software-defined radios in general. However, multi-channel reception scenarios tend to have high dynamic range which set hard-to-reach requirements for receiver linearity. This paper proposes a calibration-based(More)
This paper studies the idea and performance of cyclostationary spectrum sensing in cognitive full-duplex radios, when secondary transmission and spectrum sensing are done simultaneously at the same channel. The paper starts by briefly introducing the ideas of cognitive full-duplex radio and the cyclostationary spectrum sensing in the presence of(More)
In this article, the design and implementation of mixed-signal frequency synthesis for wireless communications devices are addressed. The core of the synthesizer builds on digitally synthesized tunable low-frequency I/Q tone which is then shifted to the actual radio frequency range using I/Q modulation. An efficient real-time FPGA design of the digital(More)