A proof-of-concept superregenerative QPSK transceiver

In this paper we present a description and experimental verification of an HF-band proof-of-concept superregenerative transceiver for QPSK signals. We describe a simple implementation of an all-digital, FPGA-based, QPSK transmitter section. On the receiver side, the quench signal is generated in the same FPGA with a minimum of analog circuitry. As the main novelty, we present a simple synchronization scheme suitable for packetized transmissions.Peer ReviewedPostprint (author’s final draft

Superregeneration revisited: from principles to current applications

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Wireless communications play a central role in our modern connected lives; at the same time, they constitute a very broad and deep area of research. The elements that make wireless communications possible are a transmitter, which sends information through electromagnetic waves; a medium that is able to transport these waves; and, finally, a receiver, which extracts the information from the-usually very small-amount of energy it is able to collect from the medium.Peer ReviewedPostprint (author's final draft

Joint symbol and chip synchronization for a burst-mode-communication superregenerative MSK receiver

In this paper we describe a superregenerative (SR) MSK receiver able to operate in a burst-mode framework where synchronization is required for each packet. The receiver is based on an SR oscillator which provides samples of the incoming instantaneous phase trajectories. We develop a simple yet effective technique to achieve joint chip and symbol synchronization within the time limits of a suitable preamble. We develop some general results and focus on the case of the IEEE 802.15.4 MSK physical layer. We provide details on a VHDL implementation on an FPGA where the most complex digital processing block is an accumulator. Simulation and experimental results are provided to validate the described technique.Peer ReviewedPostprint (published version

Aplicaciones avanzadas del principio superregenerativo a comunicaciones por radiofrecuencia

There exists today an increasing demand for wireless devices which require low cost and minimum power consumption radiofrequency front-ends. Precisely, these are two remarkable characteristics of the superregenerative receiver (SR). In this thesis, we present some novel applications of the SR receiver which make use of both simple methods and simple implementations that fit perfectly with its main features. The superregenerative reception principle was presented for the first time in 1922, and it was initially used with analog amplitude modulations, such as voice communications. The same principle was spread to digital amplitude modulations in applications where data transmission was required. Moreover, it has also been used in frequency modulation reception through an FM-to-AM conversion mechanism, but due to the inherent characteristics of the receiver, it is only suitable with wide band modulations.In the latest few years, some SR receiver proposals for phase modulation detection have emerged. It has been demonstrated that, with this type of modulation, the resulting architecture might be even simpler than the traditional ones devoted to detect amplitude modulations. This thesis advances in this line and its main goal is to discover new possibilities of the SR receiver in angular modulation detection, which have been little exploited so far. With this aim, a variety of prototypes were designed and implemented for PSK modulations on the one hand and, on the other hand, for narrow band FSK modulations. More specificifically, the thesis describes a SR QPSK transceiver and a SR M-PSK transceiver. These transceivers make use of a digital phase detection technique that is very simple. In order to confirm the viability of the proposed idea, some implementations in the HF band operating at a symbol rate of 10 kHz were developed. Regarding frequency modulations, we present a SR receiver detection method suitable for the narrowband case. This method is based on the observation of the instantaneous phase once per symbol, so that we are able to detect the received frequency through the value of the detected phase. For this case two implementations are presented: a SR receiver for Sunde's FSK modulation, and a SR receiver for MSK modulation. By using the designed SR receiver for the MSK modulations as a starting point, a SR MSK transceiver compatible with the IEEE 802.15.4 standard is implemented. This standard defines the physical layer and the medium access control (MAC) layer used for low speed wireless personal area network, a field in which the SR receiver fits perfectly. Finally, we describe a synchronization method for SR MSK receivers at the symbol, chip and frame levels. This method is presented in a general way and it is able to sinchronize through any preamble satisfying some specific requirements. In particular, we describe an implementation that aims to synchronize IEEE 802.15.4 standard frames. Simplicity has been prioritized in all the presented designs and implementations in order to potentiate the characteristic low cost and low power consumption features of the SR receiver. Likewise, we prove that this kind of receiver is especially efficient in the detection of phase and narrowband frequency modulations.Actualmente existe una demanda creciente de dispositivos inalámbricos que requieren el uso de front-ends de radiofrecuencia de bajo coste y consumo de potencia reducido, requisitos en los que el receptor superregenerativo (SR) destaca de forma especial. En esta tesis, se presentan distintas aplicaciones novedosas del receptor SR con métodos e implementaciones simples en consonancia con sus principales prestaciones. El principio de recepción superregenerativo fue presentado en el año 1922, siendo utilizado en sus inicios para modulaciones analógicas de amplitud como, por ejemplo, comunicaciones de voz. El mismo principio fue extendido posteriormente a modulaciones de amplitud digitales en aplicaciones que requerían la transmisión de datos. Por otro lado, también se ha utilizado en la recepción de modulaciones de frecuencia, mediante un mecanismo de conversión de modulación de frecuencia a modulación de amplitud. Sin embargo, debido a las características intrínsecas del receptor, este solo resulta adecuado para modulaciones de banda ancha. En los últimos años, han surgido algunas propuestas de receptor SR para modulaciones de fase. Se ha demostrado que, con este tipo de modulaciones, la arquitectura resultante puede ser incluso más simple que las tradicionales para la detección de modulaciones de amplitud. Esta tesis avanza precisamente en esta línea y tiene como objetivo descubrir nuevas posibilidades de utilización del receptor SR en la detección de modulaciones angulares, poco explotadas hasta el momento en combinación con este tipo de receptor. Con este objetivo, se diseñan e implementan diversos prototipos para modulaciones de fase PSK, por un lado, y para modulaciones de frecuencia FSK de banda estrecha, por otro. Más concretamente, se describe un transceptor SR QPSK y un transceptor SR M-PSK. Estos transceptores se basan en una técnica de detección de fase digital de gran simplicidad. Se han realizado implementaciones en la banda de HF operando a una frecuencia de símbolo de 10 kHz, con el fin de demostrar la viabilidad del concepto propuesto. Con respecto a las modulaciones de frecuencia, se presenta un método de detección con receptor SR para el caso de banda estrecha. Este método se basa en observar la fase instantánea una vez por símbolo, consiguiendo detectar la frecuencia recibida a través del valor de la fase detectada. En este caso, se presentan dos implementaciones: un receptor SR para la modulación FSK de Sunde y un receptor SR para la modulación MSK. Utilizando el receptor SR para la modulación MSK diseñado como punto de partida, se implementa un transceptor SR MSK compatible con el estándar 802.15.4. Este estándar define la capa física y la capa de control de acceso al medio (MAC) para redes inalámbricas de área personal de baja velocidad, ámbito en el cual el receptor SR encaja a la perfección. Finalmente, se describe un método de sincronización para receptores SR MSK a nivel de símbolo, de chip y de trama. Este método se presenta de forma genérica, pudiéndose sincronizar con cualquier preámbulo que cumpla unas características determinadas. En particular, se describe una implementación que tiene como objetivo sincronizar tramas del estándar IEEE 802.15.4

Experimental investigation of RF fading channels and receiver detection

This thesis includes experimental investigation of Multiple Input Multiple Output (MIMO) Radio Frequency (RF) fading channels and detection of superregenerative receivers. Details of experiment design and hardware implementation, data acquisition and analysis, and results for both studies are chronicled into two papers. The first paper investigates the validity of the discrete time triply selective fading channel model for fixed mobile-to-mobile MIMO channels. A 2x2 MIMO-OFDM testbed using the Altera Stratix III EP3SL150F field programmable gate array (FPGA) DSP development kit is used for acquiring experimental data. Subsequent offline signal processing and analysis are done in MATLAB. The Channel Impulse Response (CIR) is estimated using the Time domain Least Squares (LS) method. The channel coefficient covariance matrix is decomposed into its Kronecker factors - the spatial correlation matrix, inter-tap correlation matrix, and temporal correlation matrix. This study verifies the theoretical hypothesis and simulation results. The second paper proposes a novel method for detection of the superregnerative RF receivers. The algorithm is based on active stimulation and correlation of long pseudonoise (PN) sequences. An experimental setup is established using the Universal Software Radio Peripheral (USRP) as the primary component. Simulation results show that the maximum length PN sequences exhibit the best correlation properties among different potential stimulation signals. Proposed method improves range and accuracy of detection as compared to the passive detection and power detection methods --Abstract, page iv

Signal and noise power spectra in superregenerative oscillators

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper presents a method to quantify noise in superregenerative oscillators. A frequency domain technique, originally intended to determine the signal response, can also be used to determine the noise response. This paper focuses on the procedure required to achieve this. Signal and noise spectra are obtained and their shape is compared. Finally, signal-to-noise ratio is computed for different quench signalsPeer ReviewedPostprint (author's final draft

Noise analysis of super-regenerative oscillators in linear and nonlinear modes

A rigorous analysis of noise effects in super-regenerative oscillators (SROs), operating in both linear and nonlinear modes, is presented. For operation in the linear mode, two different analysis methods are presented. One is based on the calculation of linear-time variant (LTV) transfer function with respect to the input signal and the noise sources. The second method is based on a compact semianalytical formulation of the pulsed oscillator under the effect of the quench signal. The compact formulation also enables the analysis of the SRO in the nonlinear mode. It constitutes a fully new mathematical description of SROs, with general applicability, as it is not restricted to a particular oscillator topology. It relies on a numerical nonlinear black-box model of the stand-alone free-running oscillator, extracted from harmonic-balance simulations. This model is introduced into an envelope-domain formulation of the SRO at the fundamental frequency. Both the method based on LTV transfer functions and the semianalytical formulation take into account the cyclostationary nature of the SRO response to the noise sources. In the nonlinear mode, the variances of the amplitude and phase are calculated linearizing the formulation of the pulsed steady-state solution. The particular time variation of the phase variance is explained in detail and related to the onset and extinction of the oscillation in the presence of an RF input signal. The new analysis methods have been validated with both independent circuit-level simulations and measurements.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under Project TEC2017-88242-C3-1-R

Envelope-domain analysis and modeling of super-regenerative oscillators

An envelope-domain methodology for the numerical modeling of super-regenerative oscillators (SROs) is presented. The main advantage is its generality of application to transistor-based oscillators with arbitrary topology. Initially, a stability analysis of the nonoscillatory steady-state solution, forced by the quench signal, is performed. It is based on the calculation of a linear-time-variant (LTV) transfer function, obtained by linearizing the circuit envelope-domain equations about the nonoscillatory regime. Under moderate quench frequencies, it will be possible to estimate the SRO normalized envelope and sensitivity function from the detected dominant pair of complex-conjugate poles. In the general case, the SRO oscillatory response is modeled with a numerical method, valid under linear operation with respect to the input signal. This is based on the calculation of the LTV impulse response from a time-frequency transfer function obtained under a small-signal sinusoidal excitation. The LTV impulse response enables a straightforward determination of the sensitivity time interval and time distance to the envelope maximum. An integral expression, in terms of the LTV transfer function, will provide the SRO response to any small-signal input with any arbitrarily carrier frequency and modulation. The methodology has been successfully validated through its application to an SRO at 2.7 GHz, which has been manufactured and measured.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under Research Project TEC2014-60283-C3-1-R and Research Project TEC2017-88242-C3-1-

Analysis of superregenerative oscillators in nonlinear mode

Superregenerative oscillators in a nonlinear mode are investigated in detail using methodologies based on envelope transient, complemented with additional algorithms. A maximum-detection technique is applied to obtain the input-power threshold for nonlinear operation under different implementations of the quench signal. A mapping procedure enables the prediction of hangover and self-oscillation effects. It is based on the detection of the sequence of local maxima in the envelope amplitude after the application of a single input pulse. Using a contour-intersection method, and depending on the analysis time interval, it is possible to quantify the hangover effects and obtain the oscillation boundary, in terms of any two significant parameters. Then, a compact time-variant behavioral model is derived, valid in the absence of hangover and self-oscillation effects. It consists of a single time-variant Volterra kernel and is applicable provided that the amplitude transitions occur outside the sensitivity interval. Various methodologies are tested in a practical FET-based oscillator at 2.7 GHz. The prototype has been manufactured and measured, obtaining good agreement with the analysis results.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under the research project TEC2017-88242-C3-1-R

Publicacions científiques de l'Escola Politècnica Superior d'Enginyeria de Manresa (EPSEM) curs 2013-2014

Aquest informe ha estat elaborat per la Biblioteca del Campus Universitari de Manresa amb l'objectiu de proveir les dades sobre la recerca a la memòria del curs 2013-2014 de l'Escola Politècnica Superior d'Enginyeria de Manresa (EPSEM). Inclou les publicacions del personal docent i investigador del centre durant el curs esmentat. s'han extret de Futur.upc.edu i s'han analitzat amb Scopus.Postprint (published version