Tunable high-frequency Gm-C filters

We consider known, modified, and new transistor circuits for transconductors and some theory on their application in integrated tunable Gm-C or transconductor-eapacitor filters for high frequencies. The circuits are balanced and mostly complementary. They use bipolar (NPN and VPNP) and/or CMOS transistors. The low delay and low input capacitance of the newer circuits makes them particularly suitable for very high frequencies, in the hundreds of megahertz. The relatively high power efficiency and low noise lead to a low power consumption in combination with a high signal-to-noise ratio. Their simplicity results in a small chip area and hence in low cost. The partly new theory is on noise, sensitivities, quality factors, linearization, power and power efficiencies     

Frequency tuning technique for Gm-C filters

A frequency tuning technique based on an envelope locked loop is proposed for Gm-C filters. A degenerated integrator is used as the master circuit to eliminate the problems associated with the DC offset of the operational transconductance amplifier (OTA)     

基于多相滤波器的信道化接收机及其应用研究

本文主要研究了应用多相滤波技术的信道化接收机建模问题。在给定信道频谱划分方案下,推导了基于多相 滤波器的信道化接收机数学模型。并由此模型设计了一个四信道模拟系统。最后用仿真实验结果验证了模型的正确性。     

CMOS linear programmable transconductor suitable for adjustable Gm-C filters

A novel CMOS linear programmable transconductor is presented. It is based on a telescopic cascode operational transconductance amplifier with source degeneration implemented by means of highly linear tunable active resistors. The transconductor has been designed in a 0.5 mum CMOS technology featuring a third-order intermodulation (IM3) of -54.8 dB at 10 MHz for a 1 V_pp output voltage. Its feasibility for Gm-C filter design has been experimentally validated with a 1 MHz tunable third-order Chebyshev lowpass filter suitable for Bluetooth applications.     

A fast algorithm for polyphase quadrature filters

A fast algorithm for computing the polyphase quadrature filters (PQF), which are typically used in data reduction of audio and speech signals, enables the implementation of either a larger number of subbands or a better data reduction method, or both, in real-time applications. The algorithm, which was developed for use in a hidden channel approach, has been implemented on a Motorola 56001 (27 MHz), where the fast algorithm enables practical use of more than 32 subbands on audio signals. As the number of calculations for M subbands is reduced from approximately M² to M log₂(M), a 64-band analysis or synthesis filter requires only about 22% of the computation capacity compared with approximately 43470 with other algorithms     

A low-transconductance OTA with improved linearity suitable for low-frequency Gm-C filters

A fully differential operational transconductance amplifier is presented in this paper with enhanced linearity and low transconductance, suitable for low-frequency Gm-C filters. This paper also proposes a new common-mode feedback scheme that presents low sensitivity to large differential voltage swings at the OTA outputs. The proposed OTA was employed in the design of a fully-integrated Gm-C low-pass filter with a cutoff frequency of 30 kHz. The Gm-C filter was fabricated in a 0.35 μm CMOS technology and presented a THD at the output less than 1% for input signals with differential amplitudes up to 3.2 V.     

Low-voltage low-power Gm-C filters: a modified configuration for improving performance

In this paper, after addressing the effect of finite output impedance of Gm cells on the performance of Gm-C filters, a modified configuration suitable for low-voltage operation is presented. In the proposed architecture, to efficiently increase the output impedance, body-driven impedance boosting is employed. The circuit-level topology of Gm cells is modified in order to increase the output impedance with minimized power consumption. To show the effectiveness of the proposed scheme, a 0.9-V 5-th order Butterworth low-pass filter with 8 MHz cutoff frequency is designed and simulated in 90-nm CMOS technology. Employing the proposed technique, power consumption is reduced from 0.7 mW to 0.5 mW.     

CMOS mixers and polyphase filters for large image rejection

This paper presents an in-depth treatment of mixers and polyphase filters, and how they are used in rejecting the image in transmitters and receivers. A powerful phasor-based analysis is used to explain all common image-reject topologies and their limitations, and it is shown how this can replace complex trigonometric equations commonly found in the literature. Practical problems in design and layout that limit the performance of image-reject upconversion and downconversion mixers are identified, and solutions are presented or limits explained. This understanding is put to work in a low-IF CMOS wideband, low-IF downconversion circuit, which repeatedly rejects the image by 60 dB over the wide band of 3.5 to 20 MHz without trimming or calibration     

High speed and silicon-saving adaptive tuning system for high frequency Gm-C filters

In this paper, a novel adaptive tuning system used in Gm-C continuous time (CT) filters has been presented. The novelty of this method is the generation of quasi-gradient functions for the adaptive algorithm. By this method we have implemented the fully adaptive tuning algorithm on chip, and received more than 95% precision for the all characteristics of Gm-C filter. All the circuit level simulations and prototype fabrication have been done using 0.6 μ CMOS technology of AMS.     

DESIGN OF POLYPHASE WAVE DIGITAL FILTERS WITH APPROXIMATELY LINEAR PHASE

It is well known that IIR digital filters require quite fewer computations,comparedwith FIR filters,in order to meet stringent magnitude specifications when the phase distortioncan be tolerated.An approximately linear phase,however,can be also obtained with the IIRfilter by making use of a technique without increasing the complexity.Based on a certain numberof attenuation zeros in the pass band,a new approach is developed for the design of polyphasewave digital filters with exact magnitude responses and Chebyshev approximation of the desiredphase responses.The minimum number of attenuation zeros is estimated,and some examples areincluded.     

一种基于多相滤波的高效信道化算法研究及改进

本文对基于多相滤波技术的信道化算法做了仿真和优缺点分析.针对其存在盲区的问题,以降低抽取率为基础,对该算法进行了改进,建立了无盲区信道化接收机模型.并由此模型设计了四信道仿真系统,实验结果验证了模型的正确性.最后,在Tiger SHARCTS101上实现了改进算法,运行结果证明了算法的高效性.     

An improved design method based on polyphase components for digital FIR filters

This paper presents an efficient design of digital finite impulse response (FIR) filter, based on polyphase components and swarm optimisation techniques (SOTs). For this purpose, the design problem is formulated as mean square error between the actual response and ideal response in frequency domain using polyphase components of a prototype filter. To achieve more precise frequency response at some specified frequency, fractional derivative constraints (FDCs) have been applied, and optimal FDCs are computed using SOTs such as cuckoo search and modified cuckoo search algorithms. A comparative study of well-proved swarm optimisation, called particle swarm optimisation and artificial bee colony algorithm is made. The excellence of proposed method is evaluated using several important attributes of a filter. Comparative study evidences the excellence of proposed method for effective design of FIR filter.     

Minimum component high frequency Gm-C wavelet filters based on Maclaurin series and multiple loop feedback

A minimum component high frequency Gm-C wavelet filter structure is presented. A simple function from Maclaurin series approximation is used and the current-mode follow-the-leader feedback structure is employed. For the seventh-order Marr wavelet bandpass filter, the proposed implementation architecture contains only seven ideal Gm-C integrators for poles and one transconductor for zeros. A 100 MHz wavelet filter has been designed and simulated in 0.18 m CMOS and results show the feasibility of the proposed approach.     

Multirate digital filters, filter banks, polyphase networks, andapplications: a tutorial

The basic concepts and building blocks in multirate digital signal processing (DSP), including the digital polyphase representation, are reviewed. Recent progress, as reported by several authors in this area, is discussed. Several applications are described, including subband coding of waveforms, voice privacy systems, integral and fractional sampling rate conversion (such as in digital audio), digital crossover networks, and multirate coding of narrowband filter coefficients. The M-band quadrature mirror filter (QMF) bank is discussed in considerable detail, including an analysis of various errors and imperfections. Recent techniques for perfect signal reconstruction in such systems are reviewed. The connection between QMF banks and other related topics, such as block digital filtering and periodically time-varying systems, is examined in a pseudo-circulant-matrix framework. Unconventional applications of the polyphase concept are discussed     

Postpolarizer mismatch effects in waveguide radiating systems

Postpolarizer impedance mismatch effects are known to have a degrading influence on the performance of a circularly polarized waveguide radiating system. These effects are analyzed in this paper     

The effects of CCII non-idealities on voltage-mode active filters

In active filters, the performance of the active element plays an important role in the overall performance of the filter, besides the filter configuration itself. In this paper, we will investigate the effects of current conveyor non-idealities on a certain class of filters which consists of four current conveyors and seven nodes, and derive analytical expressions for the filter parameter deviations in terms of non-ideality terms. The results obtained apply to all filters under this class which are considerable in number. This will enable us to determine the requirements for the current conveyor non-ideality terms in order to obtain a specified filter performance. A comparable demonstration of the filter transfer functions for two example current conveyor circuits will be given. Simulations including three types of filters, namely, the bandpass, lowpass and highpass filters, confirm the analytical expressions obtained.     

P4多相码的性能评估

简要介绍了P4多相码的模糊函数、积累旁瓣电平等多项性能指标,详细分析了经过采样滑窗旁瓣抑制后P4多相码的多普勒性能,给出了脉压后主峰幅度及主副比随多普勒变化的MATLAB仿真结果,证明了采样滑窗旁瓣抑制方法的有效性,为工程应用提供了理论依据。     

A 5.2-GHz GaInP/GaAs HBT double-quadrature downconverter with polyphase filters for 40-dB image rejection

A 5.2-GHz 11-dB gain, IP/sub 1 dB/=-17 dBm and IIP/sub 3/=-10 dBm double-quadrature Gilbert downconversion mixer with polyphase filters is demonstrated by using GaInP/GaAs heterojunction bipolar transistor (HBT) technology. The image rejection ratio is better than 40 dB when LO=5.17 GHz and intermediate frequency (IF) is in the range of 15 MHz to 40 MHz. The Gilbert downconverter has four-stage RC-CR IF polyphase filters for image rejection. Polyphase filters are also used to generate local (LO) and radio frequency (RF) quadrature signals around 5 GHz in the double-quadrature downconverter because GaAs has accurate thin film resistors and the low parasitic semi-insulating substrate.     

基于多相码的MIMO雷达模糊函数

从MIMO雷达的特点出发,在双基地雷达模糊函数基础上,提出了MIMO雷达的模糊函数.MIMO雷达的模糊函数是各双基地雷达模糊函数的线性组合,并且双基地雷达的模糊函数是直角坐标系中目标速度和位置的函数.数值计算表明,MIMO雷达的模糊函数具有直接确定目标位置和速度的能力,并且模糊函数与参考点的选取无关,通过增加发射站和接收站的数目能够提高模糊函数的位置分辨率.     

Quantisation effects in second-order wave digital filters

A novel quantisation strategy is found for the second-order wave digital filter proposed by Verkroost so that the filter possesses near-optimal noise performance and only exhibits very low amplitude limit cycles under constant input conditions.