摘要:

The paper is concerned with the noise optimisation of filter sections. A systematic approach based on optimisation theory is taken, which makes use of the remaining freedom of choice of element values when the transfer-function coefficients are fixed. An algebraic and a computer-aided noise optimisation are described.

DOI:10.1049/ij-ecs.1977.0016

出版商:IEE    

年代:1977

数据来源: IET

摘要:

In the paper, the minimisation of the gain-sensitivity product (g.s.p.) for two important active-filter types that are finding widespread use in voiceband communication systems, in the form of hybrid-integrated filter building blocks, is considered. The first comprises a twin I for zero realisation: this is incorporated in the positive-feedback loop of a single operational amplifier and is referred to as the twin-T s.a.b.b. The known conditions for minimum g.s.p. for the twin-T s.a.b.b. are briefly recapitulated and expanded. The second comprises a differential scheme for zero realisation, and combines positive and negative feedback. It is referred to as the single-amplifier biquad (s.a.b.). The paper shows that the two circuits are closely related by the complementary transformation, and that conditions for minimum g.s.p. in both cases are identical

DOI:10.1049/ij-ecs.1977.0017

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The paper presents a way to analyse networks having the ideal op-amps for the most general case, i.e. for amplifiers with differential input and differential output; the way of analysis being based on the nodal voltage approach. The proposed method has been mathematically proved, and the deduced formulas make it possible to calculate the networks with ideal op-amps using computers. Examples of calculations have alsobeen given

DOI:10.1049/ij-ecs.1977.0018

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The design and performance of a recirculating delay-line correlator employing a charge-coupleddevice high-density digital memory are reported. The operation of the processor is demonstrated when arranged as a matched filter and spectrum analyser for typical sonar waveforms. The processor permits rapid evaluation of system performance with changes in signal parameters, and resutls are presented which simulatethe effects of target Doppler on linear frequency modulation and linear period modulation

DOI:10.1049/ij-ecs.1977.0019

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The canonical circuit introduced is an activeRCcircuit using a single operational amplifier, and its input admittance is composed of a frequency-dependent negative resistance (f.d.n.r.) in parallel with a resistor and a capacitor. The quality factor of the proposed circuit can be independently controlled by means of a single grounded resistor. Passive sensitivities and the effects of the nonideal op-amps are given. Applications of the parallel resonator in lowpass and bandpass filters are discussed. Finally, experimental results are presented

DOI:10.1049/ij-ecs.1977.0020

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The use of a Costas-type phase-locked loop in the demodulation of narrow-band carrier suppressed analogue speech modulation is considered and new results are obtained which define the limits of usefulness of the loop. Techniques are suggested which overcome these limitations and allow the loop to be used to coherently demodulate the suppressed carrier modulation

DOI:10.1049/ij-ecs.1977.0021

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The complete design of a highly selective bandpassRC-active filter is presented, where special attention is payed to the choice of the approximating function. By using multiple critical route equiripple (mucroer) polynomials, a substantial reduction in maximumQ-factor and variance of the attenuation is obtained. This fact allows the use of biquadratic building blocks with only one operational amplifier (o.a.) in a cascade connection, without the need of multiple-loop feedback techniques. Furthermore, a much smoother group delay is achieved. The price payed for all these advantages is a slight increase in the number of 2ndorder sections to be cascaded. In the realisation, the real-integrator multiple-feedback (r.i.m.f.) section has been employed for its low-cost, easy-tuning, and high-Qcapabilities. In the paper, the design and tuning procedure of this block are reported, together with the corresponding experimental results. Finally, a compensation technique of theQ-factor variability with the temperature is described and the experimental curves arc shown

DOI:10.1049/ij-ecs.1977.0022

出版商:IEE    

年代:1977

数据来源: IET

摘要:

A compatible single-sideband signal is one that permits distortion-free detection with an envelope detector and a lowpass filter. Previous work shows that it is possible to form this compatible signal using iterative preprocessing of the message waveform together with a Powers square-law s.s.b. transmitter. Weshow that the iterative preprocessing can be effectively replaced by a simple squaring circuit and lowpass filter, resulting in a low distortion system

DOI:10.1049/ij-ecs.1977.0023

出版商:IEE    

年代:1977

数据来源: IET