N-path filters in which the switched filters are not lowpass sections

It is shown that the generalised transfer function for switched networks, derived by Acampora, is only valid when the circuits being switched are filters whose transfer functions have negligible magnitude above half the switching frequency.     

New form of delayed N-path recursive digital filters

A new form of delay N-path recursive digital filter with transfer function expressed as a summation of N-delayed parallel recursive subfilters (each with a distinct denominator) is presented. This new filter is suitable for efficient systolic realisation and does not contain uncontrollable don't care bands. Use of the proposed filter for system modeling is demonstrated.<>     

Some comments on notch capability of N-path filters

The notch capability of the N-path filter is investigated experimentally for the simple bipolar-switching case. Verification of the predicted notch for multilevel switching is also presented.     

2-phase circulating shift register for switched-capacitor N-path filters

A novel circulating shift register for switched-capacitor N-path filters is presented. The configuration affords a means of increasing the allowable discharge time for the shift register capacitors and eliminates clock feedthrough at the signal frequency. The shift register employs a simple 2-phase clock signal for any number of paths.     

N通道调制器的研究

电信和音响系统的数字化导致了对高速高精度Ａ／Ｄ转换器的要求剧增，而ＶＬＳＩ技术的进展使得基于Σ△调制器的Ａ／Ｄ转换器成为满足这一需求的诱人的解决方法。文中提出了一种由Ｎ个独立的Σ△面调制器构成的Ｎ通道调制器，给出了其工作原理，讨论了其输出比特流信号的重构。计算机模拟结果显示出这一新型调制器能提供较好的速度与分辨率之间的折衷。     

差分时钟增益提高型N通道带通滤波器设计

针对传统N通道滤波器存在增益以及时钟的偶次谐波对滤波性能产生不利影响的问题,利用增益提高技术和差分时钟技术提出了一种增益提高型、时钟偶次谐波消除的N通道带通滤波器。在TSMC 90 nm工艺参数和1.2 V电源电压下对其进行Spectre模拟。结果表明,滤波器的增益高于9.8 dB,中心频率可调范围为0.2~2.2 GHz,S11>10 dB,IIP3>11 dB,阻带抑制为26 dB。电路结构简单,仅由反向器、开关和电容组成,且易于集成。     

Combined switched-capacitor FIR N-path filter using only grounded capacitors

A simple technique is presented that allows the unwanted sidebands of an N-path filter to be suppressed. The circuit realising this technique uses only grounded capacitors.     

Delayed N-path structure for high speed adaptive FIR digital filtering

A structure and its algorithm for high speed adaptive FIR digital filtering based on the delayed N-path concept is presented. Using N/sup 2/ processors, the throughput rate of the proposed filter can be N/sup 2/ times faster than that of the same filter realised directly using one such processor.<>     

基于N通道技术的带通Σ△A／D转换器

本文基于Ｎ通道技术，提出了一种新型的带通Σ△Ａ／Ｄ转换器，分析了其工作原理，并给出了性能的模拟结果。本文的思想对于带通Ａ／Ｄ转换系统的设计有明显价值。     

An integrated CMOS switched-capacitor bandpass filter based on N-path and frequency-sampling principles

A new combined switched-capacitor (SC) frequency-sampling N-path filter is presented, which allows the implementation of very narrow bandpass filters. The included frequency-sampling (FS) filter suppresses undesirable passbands of the SC N-path filter. The center frequency f/SUB m/ of the bandpass filter is identical to the circuit clock frequency f/SUB c/. Experimental results are presented for a CMOS SC frequency-sampling four-path filter with second-order filter cells, a center frequency of 1 kHz, and -3-dB passband bandwidth of 11.5 Hz.     

Method of reducing the f.m. threshold using a tracking N-path filter

A self-synchronised N-path filter is used to track the instantaneous incoming f.m. carrier. As a result of the narrow bandwidth, a marked reduction of the f.m. threshold, for all f.m. modulation indices, is achieved. The system is described briefly.     

Binomial filters

Binomial filters are simple and efficient structures based on the binomial coefficients for implementing Gaussian filtering. They do not require multipliers and can therefore be implemented efficiently in programmable hardware. There are many possible variations of the basic binomial filter structure, and they provide a wide range of space-time trade-offs; a number of these designs have been captured in a parametrised form and their features are compared. This technique can be used for multi-dimensional filtering, provided that the filter is separable. The numerical performance of binomial filters, and their implementation using field-programmable devices for an image processing application, are also discussed.     

Order filters

As a generalization of the median and rank filters [1]-[3], the concept of an order filter as a useful signal and image processing tool is introduced. This filter obtains a best estimate of the signal based on its order statistics. The optimal design of such a filter is illustrated in the context of the problem of envelope estimation. Other applications are also briefly mentioned.     

Multidimensional multirate filters derived from one dimensional filters

A method by which every multidimensional filter with parallelepiped passband can be designed and implemented efficiently, derived from an appropriate one dimensional filter, is presented. With this method, Nyquist constraint and zero-phase requirement can be satisfied easily. A design example is also given.<>     

Relationship between direct-coupled waveguide filters and evanescent-mode filters

A TEM-mode theory, recently advanced to explain the operation of evanescent-mode filters, is shown to be incorrect. The transition from conventional direct-coupled iris-type waveguide filters to evanescent-mode filters is shown qualitatively in two simple steps.     

Switched-capacitor filters

A novel technique for building active filters using switched-capacitor (SC) circuits is proposed. Principles of operation, methods of control, analysis, and design of a typical SC filter are presented. To assess its effectiveness, the technique is used to control input current harmonics in a phase-controlled converter. It is shown that a wide range of harmonics can be controlled using a single filter     

Binomial filters

Binomial filters are simple and efficient structures based on the binomial coefficients for implementing Gaussian filtering. They do not require multipliers and can therefore be implemented efficiently in programmable hardware. There are many possible variations of the basic binomial filter structure, and they provide a wide range of space-time trade-offs; a number of these designs have been captured in a parametrised form and their features are compared. This technique can be used for multi-dimensional filtering, provided that the filter is separable. The numerical performance of binomial filters, and their implementation using field-programmable devices for an image processing application, are also discussed.     

Self-tuned filters

A scheme for the tuning of filters is proposed. In it, filters are time-shared between a signal path and a tuning path, so that each filter in a system is individually tuned. An accurate system frequency response can thus be achieved which does not rely on tight matching between filters.     

Acoustic-surface-wave filters

Two examples of filters using Rayleigh waves, at the frequencies of 25 MHz and 150 MHz, are described. The shape, almost rectangular, of the frequency response is determined by drawing one transducer.