Beamforming of Broad-Band Bandpass Plane Waves Using Polyphase 2-D FIR Trapezoidal Filters

A new discrete-domain method is proposed for the beamforming of temporally broad-band bandpass plane waves (PWs) using a real-coefficient 2-D spatio-temporal (ST) finite-impulse response (FIR) filter having a novel rectangularly symmetric double-trapezoidal-shaped passband. The arriving temporally broad-band-bandpass ST PWs are received by a 1-D uniformly distributed sensor array. The sensor signals are pre-filtered, down-shifted to the intermediate frequency (IF) band, low-pass filtered and synchronously sampled by the real IF tri-stage temporal sampler array, resulting in a real-valued 2-D sampled sequence. The beamforming operation is then carried out on this 2-D sampled sequence using the real-coefficient 2-D FIR double-trapezoidal filter. Arithmetic complexity in the hardware implementation of the 2-D FIR double-trapezoidal filter is significantly reduced by using an array of real-coefficient polyphase 1-D FIR filters. Experimental results have confirmed that this method is capable of enhancing the desired temporally broad-band-bandpass ST PWs according to their directions of arrival under severe co-channel interference.     

Electronically Tunable Microwave Bandpass Filters

Combline filters with novel input and output coupling networks which enable broad-band tuning to be achieved with minimum degradation in passband performance are discussed. Explicit design formulas for these filters are presented. Computer analysis of varactor tuned combine bandpass filters including the small signal varactor equivalent circuit is presented enabling filter performance to be easily evaluated. The design and experimental performance of a varactor tuned combline filter, realized in suspended substrate stripline is described. This filter toned from 3.2 GHz to 4.9 GHz exhibited low passband insertion loss and its performance was is close agreement with theoretical expectations.     

The Design and Applications of Highly Dispersive Acoustic Surface-Wave Filters

The development of a low-loss broad-band linear FM dispersive filter having a time-bandwidth (TB) product of 1000 is discussed. Two systems applications for highly dispersive linear FM filters--pulse compression RADAR and a microscan receiver--are discussed with emphasis on filter performance requirements. The principal factors which influence the design of surface-wave filters are reviewed and theoretical design procedures are outlined. The 1000:1 filters, which are implemented on strong-coupling YZ lithium niobate, typically meet the design goal of a 100-MHZ rectangular passband and have a CW insertion loss of less than 35 dB. Measured data are presented for the filter performance in a pulse-compression loop and in a prototype broad-band microscan (compressive) receiver.     

几种图像缩放算法的研究

时域内常用的几种图像缩放算法有：最近邻插值、线性插值、二次插值、三次插值、拉格朗日插值、高斯插值等,对这些算法的性能进行分析比较,综合通带、阻带及截止频率,最近邻插值和线性插值应该避免,高斯基函数（N较大者）具有较好性能;并且在频域内研究了二维可分离插值滤波器和不可分离插值滤波器,这两种方法以对通带和阻带的要求作为优化目标,以滤波器的结构为约束条件,将滤波器的设计转化为一个约束优化问题进行解决;实验结果表明二维不可分离插值滤波器的方法图像缩放后的效果最好。     

Design of a 2-pole LTCC filter for wireless communications

This letter outlines the designing and manufacture of a miniaturized bandpass filter realized by low-temperature cofired ceramic (LTCC) technology for wireless products. The bandpass filter with a central frequency of 1950 MHz and a 5% passband is designed as a three-dimensional (3-D) structure based on lumped components. The design technique based on cascading overall circuit into blocks and computer-aided design of electrical circuit is presented. Experimental measurements were compared with modeling. The insertion losses in the passband (100 MHz) were less than 2 dB and the attenuation more than 20 dB in the stopband. The area occupied by the filter is 6.6/spl times/6.6/spl times/0.836 mm/sup 3/ in plane.     

A broad-band tunable CMOS channel-select filter for a low-IFwireless receiver

This paper presents a broad-band bandpass filter (BPF) designed as a channel-select filter for wireless applications. It is implemented as a low-pass filter (LPF) in series with a high-pass filter (HPF) for lower power consumption compared to true BPF. Semiscaling of the filter nodes is superior in the wireless receiver over traditional full scaling. The HPF is built with low-pass feedback of an amplifier. The bandwidth is selectable from 625 kHz, 2.5 MHz, or 10 MHz. The filter stopband loss is more than 50 dB extending beyond 100 MHz, and passband ripple less than 2.5 dB. Fabricated in a 0.6-μm CMOS process, it provides a minimum input noise of 16 nV/√Hz noise with 22.5-dBm out-of-band IIP3, while draining an average 14 mA from 3.3 V     

Small Elliptic-Function Low-Pass Filters and Other Applications of Microwave C Sections

A type of elliptic-function low-pass filter that is easy to design and construct, has low passband loss, and is very compact is described. With simple scaling and a limited number of standard parts, a broad range of cutoff frequencies can be obtained. Experimental results are presented for three filters with cutoff frequencies of 0.75, 1.0, and 1.5 GHz. Each filter occupies a volume of about 0.5 in/sup 3/. A physical interpretation of the conventional scaling transformation S =S'/ /spl Omega//sub c/' is given for networks containing unit elements. Use of this transformation is shown to yield scaled networks containing microwave C sections rather than unit elements. Applications to broad-band impedance transformers are given and other possible applications are suggested.     

Compact and selective lowpass filter with spurious suppression

A novel coplanar-type compact and selective lowpass filter is proposed. It consists of a simple high-impedance transmission line loaded with capacitors. Spurs are completely suppressed, with an attenuation larger than 20 dB outside the passband. The return loss is greater than 16 dB in the passband and the attenuation slope is more than 500 dB/decade for a 0.6 /spl lambda/-long filter.     

Low-loss LTCC cavity filters using system-on-package technology at 60 GHz

In this paper, three-dimensional (3-D) integrated cavity resonators and filters consisting of via walls are demonstrated as a system-on-package compact solution for RF front-end modules at 60 GHz using low-temperature cofired ceramic (LTCC) technology. Slot excitation with a /spl lambda/g/4 open stub has been applied and evaluated in terms of experimental performance and fabrication accuracy and simplicity. The strongly coupled cavity resonator provides an insertion loss <0.84 dB, a return loss >20.6 dB over the passband (/spl sim/0.89 GHz), and a 3-dB bandwidth of approximately 1.5% (/spl sim/0.89 GHz), as well as a simple fabrication of the feeding structure (since it does not require to drill vias to implement the feeding structure). The design has been utilized to develop a 3-D low-loss three-pole bandpass filter for 60-GHz wireless local area network narrow-band (/spl sim/1 GHz) applications. This is the first demonstration entirely authenticated by measurement data for 60-GHz 3-D LTCC cavity filters. This filter exhibits an insertion loss of 2.14 dB at the center frequency of 58.7 GHz, a rejection >16.4 dB over the passband, and a 3-dB bandwidth approximately 1.38% (/spl sim/0.9 GHz).     

Two-dimensional perfect reconstruction FIR filter banks withtriangular supports

We present a theory and design of two-dimensional (2-D) perfect reconstruction (PR) filter banks (FBs) (PRFBs) in which the supports of the analysis and synthesis filters consist of two triangulars. The two-triangular FB can be realized by designing an appropriate 2-D complex prototype whose passband support is a triangle that is a half of a parallelepiped-shaped passband support defined by the sampling matrix. Then a complex prototype filter is modulated by the DFT, and each analysis filter is derived by taking the real part of the modulated output. We show that the two-triangular FB satisfies the condition of permissibility. A necessary and sufficient condition for 2-D PRFBs is derived. Moreover, we present a design method of the 2-D PRFB that minimizes the cost function consisting of the frequency constraint and PR condition. Finally, a design example is presented to confirm the validity of the proposed method     

A Speed-Optimized Systolic Array Processor Architecture for Spatio-Temporal 2-D IIR Broadband Beam Filters

For high-speed plane-wave filtering applications, real-time 2-D spatio-temporal linear-array broadband beam filters are required, operating at temporal frame rates in excess of hundreds of megahertz. The corresponding application specific VLSI circuits must have low critical-path latencies. A novel high-speed systolic array architecture for a first-order 2-D broadband frequency-planar spatio-temporal beam filter is proposed for this purpose and employs a field-programmable gate array (FPGA) circuit where the critical path latency is minimized by timing optimization of inter- and intra-parallel processor pipelines, together with 3-D look-ahead techniques. The method facilitates single-chip VLSI circuit implementations operating at real-time frame rates of several hundred megahertz.      

A 4-D Dual-Fan Filter Bank for Depth Filtering in Light Fields

A light field is a four-dimensional (4-D) representation of the light permeating a scene-it parameterizes light rays as a function of position and direction. Such a structure can be measured using a specialized camera and can be used to render novel views of the scene it represents. It has previously been shown that the light field model of a scene may be filtered for a single depth by employing frequency-planar filters. Here, we show how a light field may be selectively filtered for a range of depths by forming a 4-D frequency passband that surrounds the intersection of two 4-D fans. A newly proposed cascaded filter bank is shown to approximate this passband, and its effectiveness is demonstrated on two scenes, both of which contain occlusions. Results are compared with those previously obtained using 4-D frequency-planar filters     

Design of some 2-D filters through the transformation technique

The transformation technique is a powerful tool for designing 2-D FIR filters. However, it is not useful for the design of specially shaped filters with passband/stopband regions not centred around the origin. The authors extend this technique to design two types of filters. A notch filter has a stopband centred about a small region in the 2-D frequency plane. The authors propose an extension to the transformation technique with the windowing concept to achieve the design of notch filters. A directional filter has a passband extending fully along a straight line passing through the origin. The transformation technique is further extended to yield such directional filters. Design and application examples for both these filters are also presented     

Concerning the influence of housing dimensions on the response anddesign of microstrip filters with parallel-line couplings [HTS circuits]

In this paper, measured results obtained from a narrow-band microstrip filter are compared with computed responses obtained using two different classes of software for various assumed housing conditions. (Some results from filters with wider bandwidths are also cited.) Housing modes are found to have a potentially significant affect on the bandwidth of microwave filters that involve microstrip coupled lines, even though the housing resonant frequencies are much above the passband of the filter. When analyzing such filters using full-wave three-dimensional (3-D) or 3-D planar field solver programs, it is found to be necessary to accurately model the housing if high accuracy in the computed response is needed. For carrying out filter design by optimization, it is usually convenient to use faster programs that utilize a full-wave two-dimensional (2-D) field solver to obtain line parameters and then use transmission-line analysis for the third dimension. Such programs can introduce housing-mode errors since 2D full-wave analysis implies an infinitely long housing. Ways for getting around this problem are suggested, Physical explanations for the various effects observed are presented and are supported by computer studies of the natural frequencies of a coupled-line microstrip filter structure in the presence of various housing perturbations     

Design of zero-phase recursive 2-D variable filters with quadrantal symmetries

The digital filters with adjustable frequency-domain characteristics are called variable filters. Variable filters are useful in the applications where the filter characteristics are needed to be changeable during the course of signal processing. In such cases, if the existing traditional constant filter design techniques are applied to the design of new filters to satisfy the new desired characteristics when necessary, it will take a huge amount of design time. So it is desirable to have an efficient method which can fast obtain the new desired frequency-domain characteristics. Generally speaking, the frequency-domain characteristics of variable filters are determined by a set of spectral parameters such as cutoff frequency, transition bandwidth and passband width. Therefore, the characteristics of variable filters are the multi-dimensional (M-D) functions of such spectral parameters. This paper proposes an efficient technique which simplifies the difficult problem of designing a 2-D variable filter with quadrantally symmetric magnitude characteristics as the simple one that only needs the normal one-dimensional (1-D) constant digital filter designs and 1-D polynomial approximations. In applying such 2-D variable filters, only varying the part of 1-D polynomials can easily obtain new desired frequency-domain characteristics.     

A Novel Class of Generalized Chebyshev Low-Pass Prototype for Suspended Substrate Stripline Filters

A novel class of low-pass prototype filters having an equiripple passband response with three transmission zeros at infinity and the remainder at a finite real frequency is presented. The prototypes are synthesized using the alternating pole technique to obtain directly the even-mode or the odd-mode admittance and little accuracy is lost for prototypes up to degree 15. Tables of element values for commonly used specifications are included. The tables are useful for the design of TEM-mode microwave broad-band filters, diplexers, and multiplexers, particularly for a printed circuit form a realization. A design example of a low-pass microwave broad-band filter designed and constructed in suspended substrate stripline (SSS) configuration is given and experimental results are also presented.     

基于SBS的通带可变微波光子滤波器

提出并分析了一种大范围可调谐的通带可变微波光子滤波器。它基于受激布里渊散射(SBS)效应并使用2个调制器与1个光纤布喇格光栅生成泵浦信号。通过分别调节这2个调制器的调制频率,可得双通带滤波器和通带间隔可变的四通带滤波器,并实现滤波器中心频率的大范围连续可调谐,而在整个调谐过程中,滤波器的3dB带宽保持不变。仿真分析了不同调制信号对滤波器通带及中心频率的影响,以及滤波器的带宽与泵浦的功率和SBS增益介质长度的关系。     

基于折叠型SIR 谐振器的双通带滤波器设计

文中提出了一种基于折叠型SIR 谐振器的双通带频率可控的微带滤波器,它由SIR 谐振器特性结合 传输线理论实现。该滤波器设计为具有两个自由度,调节谐振器的导带宽度可以对两个通带之间的频率及其间隔 进行调节。文中还研究了调整谐振器导带长度对滤波器频率特性的影响。测试结果表明,该微带滤波器有两个通 带,其中心频率分别为2. 79 GHz 和3. 90 GHz,带内最小插入损耗分别为-0. 96 dB 和-3. 0 dB,带内最小回波损耗分 别为-42 dB 和-18 dB,相对带宽分别为5. 7%和6. 7%。仿真和测试结果的一致性证实了滤波器设计的有效性。     

Design of 2-D FIR Filters by a Feedback Neural Network

A Hopfield-type neural network for the design of 2-D FIR filters is proposed. The network is contrived to have an energy function that coincides with the sum-squared error of the approximation problem at hand and by ensuring that the energy is a monotonic decreasing function of time, the approximation problem can be solved. Two solutions are obtained. In the first the 2-D FIR filter is designed on the basis of a specified amplitude response and in the second a filter that has specified maximum passband and stopband errors is designed. The network has been simulated with HSPICE and design examples are included to show that this is an efficient way of solving the approximation problem for 2-D FIR filters. The neural network has high potential for implementation in analog VLSI and can, as a consequence, be used in real-time applications.     

A Mapping-Based Design for Nonsubsampled Hourglass Filter Banks in Arbitrary Dimensions

Multidimensional hourglass filter banks decompose the frequency spectrum of input signals into hourglass-shaped directional subbands, each aligned with one of the frequency axes. The directionality of the spectral partitioning makes these filter banks useful in separating the directional information in multidimensional signals. Despite the existence of various design techniques proposed for the 2-D case, to our best knowledge, the design of hourglass filter banks in 3-D and higher dimensions with finite impulse response (FIR) filters and perfect reconstruction has not been previously reported. In this paper, we propose a novel mapping-based design for the hourglass filter banks in arbitrary dimensions, featuring perfect reconstruction, FIR filters, efficient implementation using lifting/ladder structures, and a near-tight frame construction. The effectiveness of the proposed mapping- based design depends on the study of a set of conditions on the frequency supports of the mapping kernels. These conditions ensure that we can still get good frequency responses when the component filters used are nonideal. Among all feasible choices, we then propose an optimal specification for the mapping kernels, which leads to the simplest passband shapes and involves the fewest number of frequency variables. Finally, we illustrate the proposed techniques by a design example in 3-D, and an application in video denoising.