M‐ary Bi‐orthogonal Modulation UWB with Narrowband Interference Suppression Capability

An M‐ary bi‐orthogonal modulation scheme for ultra‐wideband (UWB) systems capable of narrowband interference (NBI) suppression is proposed in this letter. We utilize a set of bi‐orthogonal pulse series to achieve NBI suppression. Through analysis and simulation, we verify that the proposed scheme can suppress NBIs effectively.     

基于正交脉冲波形的高速超宽带通信系统

提出了基于小波函数的两个正交脉冲,其功率谱密度满足美国通信委员会(FCC)对UWB系统的频谱限制。在此基础上提出了使用脉冲波形的极性调制和正交脉冲波形的形状调制相结合的一种高速超宽带通信系统,可以同时传送多个比特信息提高传信率。     

Novel UWB Transceiver for WBAN Networks: A Study on AWGN Channels

A novel ultra‐wideband (UWB) transceiver structure is presented to be used in wireless body area networks (WBANs). In the proposed structure, a data channel and a control channel are combined into a single transmission signal. In the signal, a modulation method mixing pulse position modulation and pulse amplitude modulation is proposed. A mathematical framework calculating the power spectrum density of the proposed pulse‐based signal evaluates its coexistence with conventional radio systems. The transceiver structure is discussed, and the receiving performance is investigated in the additive white Gaussian noise channel. It is demonstrated that the proposed scheme is easier to match to the UWB emission mask than conventional UWB systems. The proposed scheme achieves the data rate requirement of WBAN; the logical control channel achieves better receiving performance than the logical data channel, which is useful for controlling and maintaining networks. The proposed scheme is also easy to implement.     

Design of an Ultra‐Wideband Antenna Using a Ring Resonator with a Notch Function

This paper describes an ultra‐wideband (UWB) antenna that uses a ring resonator concept. The proposed antenna can operate in the entire UWB, and the IEEE 802.11a frequency band can be rejected by inserting a notch stub into the ring resonator. The experiment results indicate that the measured impedance bandwidth of the proposed antenna is 17.5 GHz (2.5 GHz to at least 20 GHz). The proposed UWB antenna has omnidirectional radiation patterns with a gain variation of 3 dBi (1 dBi to 4 dBi).     

Polarization filtering for narrowband interference suppression in ultra‐wideband communications

To suppress narrowband interference (NBI) in an ultra‐wideband (UWB) communications environment, a null phase‐shift polarization (NPSP) filter is proposed. The proposed NPSP filter is a combination of a linear polarization‐vector transformer (PVT), a conventional single notch polarization (SNP) filter, and an amplitude and phase compensator (APC). The NBI, which has polarized states different from those of the UWB, can be suppressed completely and the UWB signal can be recovered without distortion if the polarized states can be estimated exactly. Analytical and simulation results indicate that the signal‐to‐interference ratio (SIR) can be improved effectively after NPSP filtering. The proposed NPSP filter can be implemented in a time‐hopping spread spectrum (TH‐SS) or a direct‐sequence spread spectrum (DS‐SS) UWB system. Copyright © 2007 John Wiley & Sons, Ltd.     

基于Hermite多项式的超宽带脉冲波形研究

基于Hermite多项式理论,给出了一种适合超宽带通信的窄脉冲函数,即修正的Hermite多项式.分析了脉冲形成因子和Hermite多项式的阶数对其脉冲波形及能量谱密度的影响.研究了跳时扩频脉冲位置调制的超宽带系统在加性高斯白噪声信道下使用该脉冲的系统性能.仿真结果表明,该系统中三阶修正Hermite多项式的性能要比其它阶好.     

Multiple access interference and multipath interference analysis of orthogonal complementary code‐based ultra‐wideband systems over multipath channels

In order to alleviate multiple access interference and multipath interference of ultra‐wideband (UWB) system, we propose the orthogonal complementary code (OCC)‐based direct‐sequence UWB system and offset‐stacking (OS)‐UWB system. OCC has perfect partial autocorrelation and cross‐correlation characteristics. With the application of OCC in UWB system, we can obtain better performance in multiple access interference and multipath interference. The proposed OS‐UWB structure can also achieve variable data rate transmission because of its innovative OS spreading technique. Theoretical analysis and simulation results show that the proposed UWB system can achieve excellent performance and outperform the unitary code‐based direct‐sequence UWB system. Copyright © 2013 John Wiley & Sons, Ltd.     

一种新型超宽带陷波天线的设计

提出了一种新型超宽带(UWB)陷波天线,该天线的结构由常规的圆形单极子天线演变而成。为获得超宽带特性,天线的辐射体被设计成渐变的笑脸形状。同时,通过在辐射贴片上开C形槽来实现陷波特性。合理选择C形槽的尺寸可有效去除超宽带频段内的无线局域网WLAN(5.150~5.825GHz)的干扰。仿真结果表明,天线在4.91~6.07GHz处形成了阻带特性(电压驻波比VSWR>2),天线结构新颖简单,适用于超宽带通信系统。     

DS‐PAM UWB System Using Non‐linear Chirp Waveform

We propose a direct‐sequence pulse‐amplitude modulation (DS‐PAM) ultra‐wideband (UWB) system which employs a non‐linear chirp waveform instead of the conventional Gaussian monocycle in this paper. In the approved frequency for UWB, there exist myriad narrowband interferers. Specifically, we focus on the mutual interference between UWB systems and 802.11a WLAN. This paper offers a method to suppress this inband narrowband interference by introducing a kind of non‐linear chirp waveform. Using the proposed non‐linear chirp waveform, the effects of one or more narrowband interference sources with different frequencies can be suppressed. System performance of UWB systems in the narrowband interference environment can be improved. Computer simulations with additive white Gaussian noise successfully demonstrate an increase in performance with the proposed system as compared to traditional linear chirp systems.     

A Compact UWB and Bluetooth Slot Antenna for MIMO/Diversity Applications

A novel compact pattern diversity slot antenna for ultra‐wideband (UWB) and Bluetooth applications is presented. This antenna consists of two modified coplanar waveguides that feed staircase‐shaped radiating elements, wherein two different fork‐like stubs are placed at the 45° axis. The measured results show that this proposed antenna operates from 2.3 GHz to 12.5 GHz, covering Bluetooth, WLAN, WiMAX, and UWB. The performance of radiation patterns and the corresponding envelope correlation coefficient prove this antenna is suitable for MIMO/diversity systems. Also, the antenna's compact size makes it a good candidate for portable devices.     

A Two‐Stage Radix‐4 Viterbi Decoder for Multiband OFDM UWB Systems

This letter presents a power efficient 64‐state Viterbi decoder (VD) employing a two‐stage radix‐4 add‐compare‐select architecture. A class of VD architectures is implemented, and their hardware complexity, maximum operating speed, and power consumption are compared. Implementation results show that the proposed VD architecture is suitable for multiband orthogonal frequency‐division multiplexing (MB‐OFDM) ultra‐wideband (UWB) systems, which can support the data rate of 480 Mbps even when implemented using 0.18‐μm CMOS technology.     

Controllable Band‐Notched Slot Antenna for UWB Communication Systems

We propose a slot antenna consisting of a rectangular slot on the ground plane, fed by a microstrip line with a rectangular‐ring‐shaped tuning stub that can be deployed in ultra‐wideband (UWB) communication systems to avoid interference with wireless local area network (WLAN) communication. Our antenna can achieve a single band‐notched property from the 5 GHz frequency to the 6 GHz frequency owing to a controllable band notch that uses L‐ and J‐shaped parasitic elements. The antenna characteristics can be modified to tune the band‐notched property (4 GHz to 5 GHz or 6 GHz to 7 GHz) and the bandwidth of the band notch (1 GHz to 2 GHz). Furthermore, the shifted notch with enhanced width of the band notch from 1 GHz to 1.5 GHz is described in this paper. The UWB slot antenna and L‐ and J‐shaped parasitic elements also provide the band‐rejection function for reference in the WiMAX (3.5 GHz) and WLAN (5 GHz to 6 GHz) regions of the spectrum. Experiment results evidence the return loss performance, radiation patterns, and antenna gains at different operational frequencies.     

Performance of DS‐UWB in MB‐OFDM and multi‐user interference over Nakagami‐m fading channels

The mutual interference between the two ultra wideband (UWB) technologies, which use the same frequency spectrum, will be a matter of concern in the near future. In this context, we present a performance analysis of direct‐sequence (DS) UWB communication in the presence of multiband orthogonal frequency division multiplexing (MB‐OFDM) UWB interfering transmissions. The channel fading is modeled according to Nakagami‐m distribution, and multi‐user interference is taken into account. The DS‐UWB system performance is evaluated in terms of bit error rate (BER). Specifically, using the characteristic function approach, an analytical expression for the average BER is derived conditioned on the channel impulse response. Numerical and simulation results are provided and compared for different coexistence scenarios. Copyright © 2011 John Wiley & Sons, Ltd.     

Antiphase Tones Across Transmitting Antennas: A Spectrum Sharing Technique for Cognitive CO-STFC MB-OFDM UWB System

This paper proposes a spectrum sharing technique for coexistence of multiband orthogonal frequency division multiplexing ultra wideband (UWB) system with other primary wireless services. Existing technique like tone nulling do not utilize subcarriers within victim band, hence affects the throughput of the system. The same nulling effect can be produced by applying antiphase tones across transmitting antennas and simultaneously utilizing the victim band to transmit the data. This scheme can be applied without any impact on the current specifications of the system. In this paper complex orthogonal space time frequency code is implemented to achieve diversity in multiple antenna system. UWB receiver processing is described for both victim and unprotected band. A less computationally complex active interference cancellation scheme is also applied to improve notch depth. The proposed scheme is implemented for fixed frequency interleaving operation and discussed for time frequency interleaving with special cases. The proposed scheme is very simple to implement and provide flexibility in terms of notch width and depth.     

Application of SVD on Suppression of IEEE 802.11a Interference in TH‐PAM UWB Systems

Interference from IEEE 802.11a systems affects ultra‐wideband (UWB) systems significantly. In this letter, we suggest a novel narrow‐band interference (NBI) suppression technique based on the singular value decomposition (SVD) algorithm in time‐hopping pulse amplitude modulation (TH‐PAM) UWB systems. The SVD algorithm is used to approximate the interference which then is subtracted from the received signals. In contrast to the conventional notch filter and rake receiver, our method is more effective and the receiver complexity can be greatly reduced.     

基于认知无线电的脉冲陷波UWB窄带干扰抑制

提出了一种基于认知无线电的自适应超宽带(UWB)窄带干扰抑制方法.为了使UWB对变化的干扰环境具有自适应调节能力,引入了认知无线电技术.通过频谱感知和认知引擎技术提取窄带干扰频谱特征作为陷波器的设计依据.以高斯脉冲为例,对陷波器的陷波性能进行检验.最后,就陷波前、后脉冲的通信性能进行比较.仿真结果表明:认知陷波脉冲具有...     

一种新的超宽带脉冲波形设计方法

首先介绍了UWB成形脉冲的算法,然后基于Hermite矩阵和Chirp信号得到了UWB的成形脉冲。在对Chirp脉冲的带宽、中心频率等性能参数比较分析的基础上,将若干个Chirp脉冲信号进行线性叠加,通过仿真结果表明,随之产生的脉冲信号不仅满足FCC对UWB脉冲信号辐射功率要求,而且其脉冲信号的频谱利用率也很高,同时还能有效抑制对其他窄带系统的干扰。     

Coexistence of OSCR‐Based IR‐UWB System with IEEE 802.11a WLAN

Impulse radio (IR) is a competitive candidate for ultra‐wideband (UWB) systems. In this letter, we evaluated the coexistence of an IR‐UWB system based on an orthogonal sinusoidal correlation receiver (OSCR) with an IEEE 802.11a WLAN through a detailed simulation. The coexistence performance of the two systems is characterized in terms of the receiver's bit‐error rates. Then, some approaches to interference mitigation are discussed.     

Improved Delay‐Locked Loop in a UWB Impulse Radio Time‐Hopping Spread‐Spectrum System

As ultra‐wideband impulse radio (UWB‐IR) uses short‐duration impulse signals of nanoseconds, even a small number of timing errors can cause a detrimental effect on system performance. A delay‐locked loop (DLL) is proposed to synchronize and reduce timing errors. The design of the DLL is vital for UWB systems. In this paper, an improved DLL is introduced to a UWB‐IR time‐hopping spread‐spectrum system. Instead of using only two central correlator branches as in a conventional DLL, the proposed system uses two additional correlator branches with different delay parameters and different weight parameters. The performance of the proposed schemes with the optimal parameters is compared with that of traditional schemes through simulation: the proposed four‐branch DLLs achieves less tracking jitter or a longer mean time to lose lock (MTLL) than the conventional two‐branch DLLs if proper parameters are chosen.     

On the Degradation of a UWB System Due to a Realistic TX‐RX Antenna System

The ultra‐wideband (UWB) signal radiation process in an antenna is different from that of a narrowband signal. In this paper, we study the degradation of the desired signal component according to the antenna structure and location of a receiver in a bipolar time‐hopping UWB system. And we propose a receiver structure with an adaptive template waveform generator to compensate for the degradation caused by a realistic TX‐RX antenna system.