高温超导微波器件在雷达接收机中的应用

高温超导微波器件具有极低损耗和极低噪声的优良特性。文中将低温前端与常规接收机前端进行了性能指标的对比，对超导微波器件主要是低温前端的应用进行分析。得出结论：超导器件的应用使得接收机的灵敏度与抗干扰性能等关键指标得到大幅度提高。     

高温超导滤波器子系统在CDMA网络中的应用

在无线网络的基站接收机前端使用高温超导滤波器子系统可以有效地降低终端发射功率,提高容量利用率,增加覆盖范围,减少呼叫失败率和掉话率,抑制系统外干扰,提高频谱资源利用率和降低建网成本.本文对cdma2000 1x网络中使用高温超导滤波器子系统所带来的这些优势从原理上进行分析和阐述,并且提出了高温超导滤波器子系统在未来实际应用中需要考虑的问题.     

250MHZ单边带接收机前端电路的设计与实现

为了有效地抑制各种干扰,提高甚高频单边带接收机性能,关键是有一个性能良好的前端电路.就这一问题,文章介绍了前端电路在甚高频单边带接收机中的作用和研制250MHZ单边带接收机前端电路的设计方法,同时给出了实验结果,结果表明各种干扰被有效地抑制了.     

高性能pin/HBT 集成光接收机前端设计

分析了pin/HBTOEIC跨阻光接收机前端设计中影响带宽和灵敏度的因素,并根据小信号等效电路推导了器件3dB带宽与反馈电阻、灵敏度及噪声电流的关系式。分析表明,这种集成方式的光接收机前端具有高速、高灵敏度的特性,在高速光通信系统(大于等于10Gbit/s)和波分复用系统中有广阔的应用前景。     

基于射频前端的动态频谱共享无线通信系统工作信道选择分析

由于有主用户信号的存在和部分射频器件具有不可消除的非线性特性,将在射频接收机前端中产生三阶交调等干扰信号。为了减小干扰信号的影响,从射频接收机前端的角度分析了主用户信号对动态频谱共享无线通信系统的干扰特性,得出了频谱共享无线通信系统工作信道的选择约束条件,遵循此约束条件可以降低干扰信号带来的负面影响,保障频谱共享无线通信系统的通信质量。最后,在UHF频段动态频谱共享无线通信系统中,实验验证了工作信道选择约束条件的有效性。     

一种简单的高温超导连续通带双工器设计

在双抛LaAlO3衬底上外延生长的钇系高温超导薄膜YBCO的基片上,设计并制作一个四级高温超导连续通带双工器（工作频率3.0～3.5GHz和3.5～4.0GHz）,与常规金属材料的双工器相比,体积减少3/4,插损减少2dB。在液氮温区77K时,测试结果为：通带内插损小于0.8dB,通带间带外抑制大于30dB通带中心频率。为近一步研制高温超导多工器提供了很好的借鉴,对将来高温超导信道化接收机系统的研究和设计具有重要的意义。     

宽带一体化接收前端技术的研究

本文构建了一个通用化、标准化、模块化的带射频接收前端,结合指标要求,进行了系统指标的规划及方案 的可行性论证,利用ADS 软件对其关键指标进行了仿真验证,阐述了宽带射端的设计方法及步骤。通过对各个功能模 块的设计、选择、及调试,最终在200MHz-3200MHz 的频率范围内,采用二次变频技术设计了一种超外差接收前端。 介绍了宽带射频前端系统仿真研究、接收机系统的方案选择、大动态范围接收机的实现接收机技术指标的计算与仿真 和发射机系统的设计与仿真。介绍了宽带一体化接收前端技术的系统设计与实现以及2～6GHz 通用接收机研究及关键 电路的设计与实验。     

高温超导微波器件在电子战接收机中的应用

高温超导微波器件同常规微波器件相比,具有非常明显的优势;本文回顾了高温超导微波器件的特点,探讨了电子战接收机对高温超导微波器件的应用要求及在系统中的应用可行性;开展了初步的应用试验,并提出了工程应用中需要解决的问题。     

跳频接收机中调谐高放电路的设计

论文根据开关电容阵调节电容带通滤波器的原理,设计出了能够快速跟踪调谐,并且具有较高灵敏度的快速调谐滤波器。为了保证跳频接收机信号抗干扰的能力,前端采用了两个窄带快速跟踪调谐滤波器,使得跳频接收机前端能够快速跟踪跳频变化从而改善接收机的信噪比,使跳频通信设备更加高效可靠。     

一种悬置带状线带通滤波器的设计方法

随着移动通信技术的高速发展,频率资源越来越匮乏,人们不得不在相近的频率载波上传输不同的信息.为防止不同信息之间相互干扰,插入损耗小、带外抑制度高的微型带通滤波器已成为通信接收机必不可少的关键模块.分析了Wi-Fi接收机的典型使用场景,提出了Wi Fi接收机前端带通滤波器的设计指标,采用先进设计系统(ADS)和HFSS软...     

基于相位声码器法的音乐信号正弦分量检测

设计和实现一种基于相位声码器的音乐信号正弦分量检测方法,该方法将STFT等效为一组均匀滤波器,将各正弦分量分离,并由各通道输出的相位变化率估计正弦分量的瞬时频率,然后通过寻找STFT通道中心频率与瞬时频率映射的定点进行正弦分量检测;同时,针对原始相位声码器的缺点,设计了一个多采样率、非均匀滤波器组对其进行改进。实验结果表明,该方法具有良好的瞬时频率跟踪性能,可作为音乐信号多音高估计的分析前端。     

Toward Wide-Band High-Resolution Analog-to-Digital Converters Using Hybrid Filter Bank Architecture

The paper presents the problem of design and simulation of a high-speed wide-band high-resolution analog-to-digital (ADC) converter working in a bandpass scenario. Such converters play a crucial role in software-defined radio and in cognitive radio technology. One way to circumvent the limits of today’s ADC technologies is to split the analog input signal into multiple components and then sample them with ADCs in parallel. The two main split approaches, time interleaved and frequency splitting, can be modeled using a filter bank paradigm, where each of these two architectures requires a specific analysis for its design. In this research, the frequency splitting approach was implemented with the use of a hybrid filter bank ADC, which requires an output digital filter bank perfectly matched to the input analog filter bank. To achieve this end, an analog transfer function, together with an assumption of strictly band-limited input signal, has been used to design the digital filter bank so far. In contrast, the author proposes dropping the band-limit assumption and shows that the out-of-band input signal has to be taken into account when designing a hybrid filter bank.     

FMT滤波器组设计与性能分析

研究了滤波多音调制（FMT）系统的综合／分析滤波器组,通过滤波器组多相分解推导了FMT系统接收端M路并行子信道准确重构条件。对FMT系统中低通原型滤波器进行了设计,并进行了比较,分析了由不同原型滤波器进行设计的滤波器组性能,并给出了FMT系统滤波器组的仿真结果。     

Low-Order IIR Filter Bank Design

The advantage of infinite-impulse response (IIR) filters over finite-impulse response (FIR) ones is that the former require a much lower order (much fewer multipliers and adders) to obtain the desired response specifications. However, in contrast with well-developed FIR filter bank design theory, there is no satisfactory methodology for IIR filter bank design. The well-known IIR filters are mostly derived by rather heuristic techniques, which work in only narrow design classes. The existing deterministic techniques usually lead to too high order IIR filters and thus cannot be practically used. In this paper, we propose a new method to solve the low-order IIR filter bank design, which is based on tractable linear-matrix inequality (LMI) optimization. Our focus is the quadrature mirror filter bank design, although other IIR filter related problems can be treated and solved in a similar way. The viability of our theoretical development is confirmed by extensive simulation.     

A High-Dynamic-Range Front End for an Upconversion Car-Radio Receiver

A monolithically integrated high-performance front end for an AM radio receiver is presented. Medium- and long-wave reception without any tuned-circuit alignments or band switches is made possible by using an intermediate frequency of 10.7 MHz, well above the maximum frequency to be received. Image- and oscillator-harmonics-related spurious responses are rejected by a simple low-pass filter. The upconversion concept puts high demands on the front-end circuits. A high intermodulation free dynamic range is realized by applying several unconventional and new circuit techniques. A low-noise low-distortion wide-band input amplifier with capacitive negative feedback realizes the required antenna match. The gain of this amplifier is automatically switched to a lower value in the vicinity of transmitters with high field strengths. A double-balanced mixer, driven by an oscillator employing a novel amplitude stabilization technique, provides the frequency conversion up to 10.7 MHz. Digital toning can be achieved very simply because only the local-oscillator frequency has to be varied. The dynamic range of this front end amounts to 130 dB. Field strengths up to about 20 and 200 mV/m can be handled without noticeable second- and third-order intermodulation, respectively.     

The analysis and design of two-dimensional nearly-orthogonal symmetric wavelet filter banks

The design and analysis of two-channel two-dimensional (2D) nonseparable nearly-orthogonal symmetric wavelet filter banks with quincunx decimation is studied. The basic idea is to impose multiple zeros at the aliasing frequency to a symmetric filter and minimize the deviation of the filter satisfying the orthogonal condition to obtain a nearly-orthogonal FIR filter bank. Since multiple zeros are imposed, a scaling function may be generated from the minimized filter. With this filter, a semi-orthogonal filter bank is constructed. Methods for analyzing the correlation of the semi-orthogonal filter banks are proposed. The integer translates of the wavelet and scaling function are nearly-orthogonal. The integer translates of the wavelet at different scale are completely orthogonal. The semi-orthogonal filter bank can be efficiently implemented using the corresponding nearly-orthogonal FIR filter bank.     

Design of wideband all-digital phase locked loops using multiratedigital filter banks

All-digital phase locked loops (DPLLs) have many advantages over analog loops. However, due to digital device limitations and costs, superwide PLLs with front-end bandwidths as high as one gigahertz are commonly implemented using analog parts. This article presents a new architecture that allows an all-digital implementation of superwide PLLs. The problem of operating digital components at high speed is avoided here (without reducing the front-end bandwidths) by inserting a multirate digital filter bank in front of the DPLL. The new design is shown to have steady-state and transient performance that is identical to a conventional DPLL     

Speech frame recognition based on less shift sensitive wavelet filter banks

The wavelet transform possesses multi-resolution property and high localization performance; hence, it can be optimized for speech recognition. In our previous work, we show that redundant wavelet filter bank parameters work better in speech recognition task, because they are much less shift sensitive than those of critically sampled discrete wavelet transform (DWT). In this paper, three types of wavelet representations are introduced, including features based on dual-tree complex wavelet transform (DT-CWT), perceptual dual-tree complex wavelet transform, and four-channel double-density discrete wavelet transform (FCDDDWT). Then, appropriate filter values for DT-CWT and FCDDDWT are proposed. The performances of the proposed wavelet representations are compared in a phoneme recognition task using special form of the time-delay neural networks. Performance evaluations confirm that dual-tree complex wavelet filter banks outperform conventional DWT in speech recognition systems. The proposed perceptual dual-tree complex wavelet filter bank results in up to approximately 9.82 % recognition rate increase, compared to the critically sampled two-channel wavelet filter bank.     

Sequence detection in nonlinear channels: a convenient alternative to analog predistortion

A new maximum-likelihood sequence detection receiver for spectrally efficient linear modulations on bandlimited bandpass nonlinear channels is proposed. The receiver is based on oversampling the received signal corrupted by noise and nonlinear distortion. Contrary to other solutions in the literature, in the proposed technique there is no need for a bank of matched filters, and the receiver front end reduces to a single lowpass filter. For a given peak power level, a performance gain can be achieved over more traditional approaches to transmission on nonlinear channels, such as those based on predistortion, if a moderate spectral expansion is allowed. To analyze the receiver performance, the concept of distance spectrum is employed, since the minimum distance alone cannot account for a reliable performance evaluation. Both analysis and simulation are carried out for realistic narrowband nonlinear channels, possibly employing reduced-state sequence detection. Appreciable gain margins are confirmed to be possible in these realistic cases.