Ultra-wideband Interference Research Articles

Routing Technique for Microwave Transmission Lines to Ensure UWB Interference Immunity

This article presents a novel routing technique for designing microwave transmission lines (TLs) that provide improved functionality. Unlike traditional practices, we propose locating two independent traces close to each other, resulting in strong electromagnetic coupling and potential unwanted crosstalk between traces. However, we show that the suggested routing schemes can significantly increase the ultra-wideband interference immunity of electrical circuits by using modal distortions and reflections, as demonstrated in our study of four prototypes of TLs in the form of serpentine and spiral designs with strong and weak coupling between pairs. To better predict and analyze the microwave behavior in such TLs, we used new simulation techniques based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$</tex-math> </inline-formula> -norms study. Our investigation of these TLs in a transverse electromagnetic cell in the frequency range from 10 MHz to 5.3 GHz showed a low level of radiated emissions. The results indicate that the serpentine scheme with strong coupling between pairs provides the best protection of two independent TLs against ultra-wideband interferences. Moreover, the used electrodynamic approach is in full agreement with the experimental study, further validating the effectiveness of the proposed routing technique.

Signal Integrity Analysis of the Structure with Single Modal Reservation Before and After Failures

To improve the reliability of radio electronic devices, engineers use redundancy of the most relevant circuits. The simplest and most common solution is classical cold redundancy in which the primary and redundant circuits are located far from each other. Meanwhile, locating the primary and redundant circuits close together makes it possible to use modal distortions to protect both circuits from unwanted ultra-wideband interference. This approach is known as modal redundancy or modal reservation (MR). This paper presents the results of signal integrity analysis for a structure with single MR before and after failures. It is shown that the bandwidth after failures changes. This affects the rate of data that can be excited to the input of the device without significant distortion of the useful signal. The authors used pseudorandom binary sequences with a data rate of 50 and 200 Mbps. It is experimentally shown that failures in the redundant circuit do not significantly degrade the quality of signal integrity in the bandwidth. Thus, the data-dependent jitter changes from 12 (before failures) to 19 ps (after the worst failure). In all investigated variants, the eye stays open; as a result, the bit error rate will be low. The mismatch of the redundant circuit has the largest effect on the noise amplitude. As a result, the signal-to-noise ratio decreases from 57 (before failures) to 28 (after the worst failure). To confirm the measurements, we performed electrodynamic simulations. Their results are in good agreement with the experimental data.

Моделирование и экспериментальное исследование четырехпроводной полосковой структуры с трехкратным модальным резервированием при отказах её элементов

The relevance of research on the rational use of redundancy by applying triple modal redundancy (MR) techniques to increase the resistance to ultra-wideband interference is highlighted. An experimental evaluation of the change in maximum voltage of decomposed pulses in a bilateral printed circuit board (PCB) with triple MR after failures has been performed. A special prototype of a double-sided PCB with triple MR with optimum parameters has been fabricated. SMD resistors were used as loads. At the far end of the redundant conductor of the PCB, a decomposition into 4 pulses at different input durations is shown. The maximum voltage changes before and after failures at input durations of 120 ps and 240 ps are 26.8% and 28%, respectively. The above comparison of the experimental and electrodynamic simulation results in the time and frequency domains showed their consistency. The maximum voltage and delay differences are 3.69 and 5.6 %, respectively.

Анализ и систематизация способов трассировки печатных проводников на основе симметричных структур с модальной фильтрацией

To improve the functional safety of radioelectronic equipment, a redundancy of its components, parts, and interconnections is used. In contrast to the widely used cold redundancy, the modal reservation (MR) technology protects nodes and interconnections from ultra-wideband interference (UWB) by modal distortions. There are several approaches and methods to ensure a multiple MR. These methods have different design features, electrical and mass-size characteristics, and scope of application. Of special interest are the structures with conductor symmetry along two planes that allow realizing triple MR with the same efficiency of UWB interference suppression for any circuit. This work aims to present a novel analysis and systematization of methods of multiple MR based on symmetrical structures. To solve this problem, we evaluated the technology effectiveness of eight MR methods, their operability, and efficiency. The authors performed an evaluation of decomposed pulses for each structure before and after failure using N-norms. It is found that all investigated structures with modal redundancy allow to significantly attenuate the ultrawideband pulse.

New Technique for Improving Modal Filter Performance by Using an Electromagnetic Absorber

This paper presents a novel technique for improving modal filter (MF) performance by using an electromagnetic absorber which shows a significant improvement in attenuation of ultra-wideband interference. The authors analyzed the effect of the absorber on the MF performance in suppressing conducted and radiated interferences (in the near and far fields). As an excitation, the authors used an ultra-wideband pulse of 155 ps (at 0.5 level) and then employed N-norms to estimate and characterize the decomposed pulses. It was experimentally demonstrated that the value of N1 decreased by a factor of 4.31, <i>N</i>₂ &#x2013; by a factor of 6.52, <i>N</i>₅ &#x2013; by a factor of 1.87. In terms of radiated interference in the near field, the improvement in attenuation of each norm achieved at least 2.81 times. The analysis of the characteristics in the far field showed that the use of the electromagnetic absorber allows reducing the transmission coefficient on average by 2.25 times at a distance of 1 m.

Using N-Norms for Analyzing Symmetric Protective Electrical Circuits with Triple Modal Reservation

The redundancy of functional blocks and critical assemblies in radio-electronic equipment is among the most widely used techniques for increasing reliability. Complex redundant systems raise the problem of electromagnetic compatibility (EMC). Ignoring EMC requirements can lead to partial or complete REE failures. In this paper, the authors analyze a noise-protective electrical circuit with triple modal reservation (a promising type of cold redundancy). A multilayer stripline is investigated, the conductors of which are symmetrically arranged relative to two planes. On account of the strong electromagnetic coupling, this protective circuit can decompose dangerous ultra-wideband (UWB) interference received at the input of the primary or redundant circuits into unipolar pulses of lower amplitude. Using this approach, due to the symmetry of the conductors, equal decomposition efficiency could be achieved. However, the effect of UWB interference at the input of one of the conductors produces bipolar pulses at the output of the other conductors. In this paper, the authors evaluate the dangers of unipolar and bipolar decomposed pulses and use modal analysis to mathematically determine the polarities and amplitudes of the decomposed pulses at all output nodes for a pseudo-matched structure. By using the quasistatic approach with and without losses, the time responses to a trapezoidal pulse with a total duration of 60 ps, which simulates UWB interference, are obtained. To confirm the results of modal analysis and quasistatic simulation, an experimental study is performed. Using a stroboscopic oscilloscope DSA 8300, the authors obtained a transient response to a step excitation. Then, taking the derivative, the response to a trapezoidal pulse with a total duration of 140 ps was obtained. To analyze the criticality of the decomposed pulses, N-norms are used. In the general case, it is shown that the UWB interference is decomposed into four pulses of lower amplitude. At the same time, the value of each N-norm indicates its significant attenuation. For example, the amplitude of the UWB pulse acting on the input of the reserved conductor decreases by 10.31–8.93 times. Such results numerically demonstrate the high efficiency of the suggested approach when it comes to protecting equipment against UWB interference. It is also shown that the probability of dielectric breakdown and damage to electronic components in redundant circuits is lower than in a primary circuit. This is due to the fact that the value of N3 in the redundant circuit is 2.38 times less than in the primary circuit. However, the results demonstrate that arcing is highly probable both in primary and redundant circuits. Finally, aspects of symmetry/asymmetry in the problem under investigation are emphasized.

Simulation of Interference Effects of UWB Pulse Signal to the GPS Receiver

Ultra-wideband (UWB) pulse signal has an extremely narrow pulse width and wide frequency bandwidth, which overlaps with the operating frequency band of Global Position System (GPS) receivers, posing a potential threat to their performance. In response to this problem, through mathematical analysis and software simulation, the effects of UWB pulse signal under time-hopping-pulse position modulation (TH-PPM) on the performance of GPS receivers were studied. First, the expression and waveform of the UWB pulse signal were analyzed in the time-frequency domain, and it is concluded that the pulse repetition frequency (PRF) mainly affects the discrete spectrum of the UWB signal and the TH code period mainly affects the continuous spectrum. On this basis, the simulation on the power spectral density (PSD) of GPS signal and UWB signal under different pulse parameters was represented, from which a conclusion can be drawn that the PRF is the main factor impacting the PSD of the GPS signal. Furthermore, this paper analyzed the degradation of GPS receiver equivalent carrier-to-noise ratio (C/N0) and C/A code demodulation bit error rate (BER) under UWB interference, which are the crucial evaluating indicators of GPS signal quality. Eventually, we theoretically calculated the minimum interference level of the UWB interference signal to the GPS receiver, providing a theoretical reference for reducing the interference effects of UWB pulse signal on the performance of GPS receivers.

A Robust Hyperbolic Tangent-Based Energy Detector With Gaussian and Non-Gaussian Noise Environments in Cognitive Radio System

Spectrum sensing is important for a cognitive radio (CR) system to protect primary users (PUs) from harmful interference. At present, most of the existing sensing schemes are proposed in Gaussian noise environments. Nevertheless, a CR system actually also suffers from non-Gaussian noise, such as man-made impulsive noise, ultrawideband interference and co-channel interference. In this article, to handle the degradation of detection performance in non-Gaussian impulsive noise environments, a robust spectrum sensing scheme named hyperbolic tangent-based energy detector (HT-ED) is proposed. The hyperbolic tangent function is applied to suppress the impulsive noise by the nonlinear behavior, but without restraining the normal noise by the linear behavior. This property enables the new method to achieve the good detection performance in both Gaussian and non-Gaussian noise environments. In addition, it is similar to an energy detector, the new detector does not need to know the characteristics of the PU's signal. The performance analysis of the proposed HT-ED scheme is also presented. The simulation results show the HT-ED is robust against impulsive noise, which is modeled as Laplace or α-stable noise. Moreover, the HT-ED provides a superior detection performance compared with the other existing relative methods in a wide range of non-Gaussian noise.

Evaluation of Electromagnetic Interference in Wireless Broadband Systems

Nowadays, the electromagnetic compatibility in radio frequency communication systems attracts a great attention as the wireless spectrum becomes overcrowded. A lot of wireless systems operate in the same bands or in the adjacent frequency ones. This operation results in an electromagnetic interference (EMI) among these systems. This EMI can degrade the performance of the wireless systems. Moreover, critical medical equipment, which is near to an electromagnetic radiation field, may be malfunction. A lot of studies handled the EMI phenomenon in radio systems. These studies range from the definition and the causes of the phenomenon to the development of suitable simulation tools for evaluating the EMI value. This paper handles the effect of the EMI existence on the performance of a broadband communication system in a complex radio environment. Moreover, this performance is clarified in a form of bit error rate. In addition, the complex radio environment is modeled as a summation of noise, narrow band interference (NBI), and ultra wide band interference (UWBI). The complete analysis model of a broadband radio system, which is interfered by a NBI and an UWBI, is carried out. Furthermore, the total interfering power is derived in a novel closed form formula. Finally, the performance of the system is simulated.

RESONATOR TYPE FOR THE CREATION OF A POTENTIALLY RECONFIGURABLE FILTERING BAND IN A UWB ANTENNA

In this letter, a novel frequency-reconfigurable monopole antenna with several switchable states including an ultra-wideband (UWB) state, filtering narrowband states, and a tunable filtering band state is presented. The antenna, which supports most applicable overlook narrowband frequencies between the 2-6 GHz, can be used in multiradio wireless systems. Moreover, the proposed antenna, which can avoid UWB interference and has narrowband functionality, has good potential for use in cognitive radio.

The Interference Impact of UWB Sensor on Mobile Station of 3G Mobile System

This paper presents the interference impact of Ultra Wide-Band (UWB) sensor using frequency of 3.5 GHz on 3G mobile system in Korea. The Minimum Coupling Loss (MCL) method and Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) were used to evaluate the interference impacts of UWB sensor on 3G mobile system. The minimum allowable distance between UWB interferer and the victim receiver is required 0.09 m in indoor environment; in the case of multiple UWB interferers in outdoor environment, the maximum allowable UWB transmitting Power Spectral Density (PSD) should be-93.1 dBm/MHz below to guarantee co-existence with 3G mobile system.

UWB Interference Probability on Wi-MAX Receiver (Case Study of Coexistence Issue)

The paper presents the effect of interference on coexistence issue of Ultra Wide-Band (UWB) and World Wide Interoperability for Microwave Access (Wi-MAX) operating at 3.5 GHz. Even though the transmitting power of UWB is very small (-41.6dBm) as compared to Wi-Max (33 dBm), since both systems share same band of frequencies, there is possibility of interference. An attempt is made to find the probability of interference of single UWB transmitter in indoor environment on Wi-MAX receiverfor three cases, Viz:Varying distance by moving away UWB transmitter from Victim Wi-MAX receiver.Varying distance between Wi-MAX transmitter and Victim Wi-MAX receiver.Varying UWB transmitting power.The probability of interference of multiple UWB transmitters is also observed. To evaluate the interference effects of UWB on Wi-MAX, Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) is used.

Adaptive L_p—Norm Spectrum Sensing for Cognitive Radio Networks

In cognitive radio (CR) systems, reliable spectrum sensing techniques are required in order to avoid interference to the primary users of the spectrum. Whereas most of the existing literature on spectrum sensing considers impairment by additive white Gaussian noise (AWGN) only, in practice, CRs also have to cope with various types of non-Gaussian noise such as man-made impulsive noise, co-channel interference, and ultra-wideband interference. In this paper, we propose an adaptive Lp-norm detector which does not require any a priori knowledge about the primary user signal and performs well for a wide range of circularly symmetric non-Gaussian noises with finite moments. We analyze the probabilities of false alarm and missed detection of the proposed detector in Rayleigh fading in the low signal-to-noise ratio regime and investigate its asymptotic performance if the number of samples available for spectrum sensing is large. Furthermore, we consider the deflection coefficient for optimization of the Lp-norm parameters and discuss its connection to the probabilities of false alarm and missed detection. Based on the deflection coefficient an adaptive algorithm for online optimization of the Lp-norm parameters is developed. Analytical and simulation results show that the proposed Lp-norm detector yields significant performance gains compared to conventional energy detection in non-Gaussian noise and approaches the performance of the locally optimal detector which requires knowledge of the noise distribution.

Maximum Likelihood Frequency Offset Estimation in Multiple Access Time-Hopping UWB

Frequency offset estimation for time-hopping (TH) ultra-wide-band (UWB) is addressed in the literature by relying on an AWGN assumption and by exploiting a periodic preamble appended to each packet. In this paper we generalize these techniques with two aims. First, we identify a solution which does not rely on any periodic structure, but can be implemented with a generic TH format. Second, we identify a solution which is robust to multiple access interference (MAI) by assuming a Gaussian mixture (GM) model for MAI. In fact, GMs have recently been identified as good descriptors of UWB interference, and they provide closed form and limited complexity results. With these ideas in mind, we build a data aided maximum likelihood (ML) estimator. The proposed ML solution shows quasi optimum performance in the Cramer-Rao bound sense, and proves to be robust in meaningful multiple user scenarios.

Performance analysis of 3G systems in presence of UWB interference

In this paper, the impact of the interference from multiple ultra wideband (UWB) transmitters to a 3rd-generation (3G) terminal is evaluated under UWB emission power limit regulations of federal communications commission (FCC), european telecommunications standards institute (ETSI) and Japan respectively. A three-dimensional interference model is presented where a discrete spatial distribution of UWB transmitters is considered. It is assumed that a mobile terminal and a large number of UWB devices exist in one room simultaneously. A parameter which characterizes the link budget degradation at the victim receiver is defined to measure the UWB interference to 3G systems. The maximum acceptable density of UWB transmitters and the minimum acceptable distance between UWB transmitters and the 3G terminal are analyzed under different link budget degradations. The simulation results demonstrate that the performance of time division-synchronous code division multiple access (TD-SCDMA) is the best, the one of code division multiple access 2000 (CDMA2000) is the worst and the one of wideband code division multiple access (WCDMA) lies between them in presence of UWB interference.

Performance and Optimization of Amplify-and-Forward Cooperative Diversity Systems in Generic Noise and Interference

Cooperative diversity systems have received significant attention recently as a distributed means of exploiting the inherent spatial diversity of wireless networks. In this paper, we consider a cooperative diversity system consisting of a source, a destination, and multiple single-hop amplify-and-forward relays, and provide a mathematical framework for the asymptotic analysis of this system in generic noise and interference for high signal-to-noise ratios. Assuming independent Rayleigh fading for all links in the network and orthogonal relay-destination channels, we obtain simple and elegant closed-form expressions for the asymptotic symbol and bit error rates valid for arbitrary linear modulation formats, arbitrary numbers of relays, and arbitrary types of noise and interference with finite moments including co-channel interference, ultra-wideband interference, impulsive ε-mixture noise, generalized Gaussian noise, and Gaussian noise. Furthermore, we exploit the derived analytical error rate expressions to develop power allocation, relay selection, and relay placement schemes that are asymptotically optimal in environments with generic noise and interference. In general, the power allocation problem results in a geometric program which can be solved efficiently numerically. For the special case of only one relay, we provide a closed-form result for the optimal power allocation. Simulation results confirm our analysis and illustrate that, in non-Gaussian noise, the proposed power allocation, relay selection, and relay placement schemes lead to large performance gains compared to their conventional counterparts optimized for Gaussian noise.

On the Evaluation of MB-OFDM UWB Interference Effects on a WiMAX Receiver

The European Commission has recently adopted specific power spectral density masks for ultra wideband (UWB) devices, with detect and avoid capabilities, for coexistence with licensed standards. Under these regulations, a novel approach for analyzing the UWB interference effects on the WiMAX downlink is provided in this paper by means of a novel theoretical computation of the bit error rate (BER), simulation results, and measurements in a conducted modality. New analytical BER expressions for both uncoded and coded WiMAX systems, impaired by a single multiband-OFDM (MB-OFDM) UWB interference signal, are obtained in this paper for a Rayleigh fading channel. The BER is expressed in terms of the characteristic function of the interference signal. The maximum permissible interference levels and the signal-to-interference (SIR) values, which allow the UWB interference effects to be considered negligible, are estimated in this paper from simulation and measurement results. The analysis considers a WiMAX receiver operating at its minimum sensitivity level. The BER, the symbol error probability (SEP), and the error vector magnitude (EVM) of the WiMAX link are the metrics employed to characterize the interference effects for both frequency hopping and nonfrequency hopping UWB interferers.

Impact of Ultra Wide Band emission on WiMAX systems at 2.5 and 3.5GHz

In this work, results of an analytical analysis to assess the effect of Ultra Wide Band (UWB) emissions on the Worldwide Interoperability for Microwave Access system (WiMAX) are presented. The WiMAX range is evaluated with and without the UWB interference. Free space propagation model is used to calculate the UWB signal power that interferes with WiMAX systems. It is shown that, for the case of single UWB transmitter, WiMAX system can easily tolerate UWB interference when the UWB EIRP is -83dBm/MHz or less for a distance between the UWB transmitter and the WiMAX receiver of 1m or higher at 3.5GHz frequency in order to have only 5% range reduction. To make this possible, multi band UWB should not transmit in the first and the second bands. This will have a detrimental effect on UWB technology. For 2.5GHz WiMAX, the range reduction will be 5% when the UWB EIRP is -87dBm/MHz.

Performance of BICM-SC and BICM-OFDM systems with diversity reception in non-gaussian noise and interference

In this paper, we present a general mathematical framework for performance analysis of single-carrier (SC) and orthogonal frequency division multiplexing (OFDM) systems employing popular bit-interleaved coded modulation (BICM) and multiple receive antennas. The proposed analysis is applicable to BICM systems impaired by general types of fading (including Rayleigh, Ricean, Nakagami-m, Nakagami-q, and Weibull fading) and general types of noise and interference with finite moments such as additive white Gaussian noise (AWGN), additive correlated Gaussian noise, Gaussian mixture noise, co-channel interference, narrowband interference, and ultra-wideband interference. We present an approximate upper bound for the bit error rate (BER) and an accurate closed-form approximation for the asymptotic BER at high signal-to-noise ratios for Viterbi decoding with the standard Euclidean distance branch metric. For the standard rate-1/2 convolutional code the proposed approximate upper bound and the asymptotic approximation become tight at BERs of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> and 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> , respectively. However, if the code is punctured to higher rates (e.g. 2/3 or 3/4), the asymptotic approximation also becomes tight at a BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> . Exploiting the asymptotic BER approximation we show that the diversity gain of BICM systems only depends on the free distance of the code, the type of fading, and the number of receive antennas but not on the type of noise. In contrast their coding gain strongly depends on the noise moments. Our asymptotic analysis shows that as long as the standard Euclidean distance branch metric is used for Viterbi decoding, BICM systems optimized for AWGN are also optimum for any other type of noise and interference with finite moments.

Performance of BICM-OFDM systems in UWB interference

In this paper, we develop an analytical framework for performance analysis of generic bit-interleaved coded modulation orthogonal frequency-division multiplexing (BICMOFDM) systems impaired by ultra-wideband (UWB) interference. For practical relevance we consider multi-band OFDM (MB-OFDM), direct-sequence UWB (DS-UWB), and impulseradio UWB (IR-UWB) interference formats following recent IEEE/ECMA standards or standard proposals. Besides the exact analysis we calculate the bit error rate (BER) for the case when the UWB interference is modeled as additional Gaussian noise. Our results show that in general the BER of the BICM-OFDM system strongly depends on the UWB format and the OFDM sub-carrier spacing. While the Gaussian approximation is very accurate for DS-UWB, it may severely overor underestimate the true BER for MB-OFDM and IR-UWB interference. Our analysis is applicable to e.g. IEEE 802.11 wireless local area networks (WLANs), IEEE 802.16 wireless access systems (WiMAX), and 4th generation mobile communication systems. Furthermore, since the ECMA MB-OFDM standard is also based on the BICM-OFDM concept, our analysis can also be used to evaluate the impact of other UWB signals on ECMA MB-OFDM UWB systems.