Active Filters for 1-MHz Power Circuits with Strct Input/Output Ripple Requirements

As the switching frequency of a dc-converter is raised from 100 kHz to 1 MHz, one would expect the energy storage elements of the circuit to be correspondingly reduced in size. If the circuit must meet input and output ripple requirements of the nature of MIL-STD-461B CEO3, however, the advantage of a higher switching frequency is significantly offset by the higher filter attenuation levels required. The use of active filters, in conjunction with minimal passive filters, to achieve the required ripple levels with a much smaller overall volume is discussed. Working active filters with gains in excess of 100 at 1 MHz are also presented.     

一种线性相位LC滤波器的设计

为解决滤波器带外抑制和通带内相位波动之间的矛盾,该文介绍了一种线性相位LC滤波器的设计方法,通过对滤波器传输零点特性进行分析,根据指标要求灵活设计电路拓扑结构和零点位置,采用内、外均衡电路级联网络两种方法,来实现具有高矩形、线性相位特性的滤波器。设计了中心频率21.4 MHz、0.5 dB带宽大于10 MHz、矩形系数(45 dB/0.5 dB)小于2、带内相位波动绝对值小于5°和中心频率1 300 MHz、1 dB带宽大于200 MHz、矩形系数(35 dB/1 dB)小于2、带内相位波动绝对值小于5°两款滤波器。该方法工程实用化强,便于调试和制作,可应用于幅相特性要求高的微波系统中,提高了系统性能指标。     

30-100-MHz NPN-only variable-gain class-AB instantaneous compandingfilters for 1.2-V applications

Two variations of a continuous-time instantaneous companding filter were integrated in a 25 GHz bipolar process. Their -3-dB frequencies are tunable in the ranges of 1-30 and 30-100 MHz. The DC gains are controllable up to 10 dB. The measured dynamic ranges for a 1% total harmonic distortion are 62.5 and 50 dB, for the 30 and 100 MHz filters, respectively. At maximum cutoff frequencies, the filters dissipate 6.5 mW from a 1.2 V supply     

Active GaAs MMIC band-pass filters with automatic frequency tuningand insertion loss control

This paper presents the design and measured performance of active tunable band-pass MMIC filters and matched MMIC control circuits, both fabricated using a standard 1-μm GaAs MESFET foundry process. The control circuits generate filter frequency-tuning and Q-control bias voltages by using a dual-loop master-slave control scheme. Separate 3-section filters cover 1.5-2.0 and 1.96-2.64-GHz bands with 3-dB bandwidths of 86±6 and 126±1.0 MHz, respectively. The control circuits automatically maintain the filter insertion loss to within ±0.5 dB over these tuning ranges, and regulate the center frequency and insertion loss to within better than ±1.2 MHz and ±0.3 dB over a temperature range of -50°C to +75°C     

Microwave active resonator band-pass filters in various mmic technologies

In this article, two topologies of L-C parallel active resonators are presented. These circuits are realized in MMIC technology, using three transistors which could be MESFET, hemt or HBT. The survey of these resonators shows the possibility, by controling the values of a resistor and/or a capacitor, on the one hand, to tune the resonance frequency of these circuits, and on the other hand, to cancel out their losses so as to obtain negative conductance. Compact, lossless and narrow-band filters are then implemented using previous active resonators. To date, the use of mesfet technology has reduced the synthesis of such active filters in S-band and at X-band low frequencies. Now, however, hemt and HBT technologies allow the extension of their implementation to the whole X-band. This survey is illustrated by the simulated response of a 10 GHz filter with a 500 MHz 3 dB bandwidth. The mmic technology is a 0.2 μm hemt one. The simulated performances of this filter achieve a mean transmission gain of 0. 5 dB, with a reflection loss higher than 10 dB at 10 GHz,     

Coupled-Magnetic Filters With Adaptive Inductance Cancellation

Conventional filter circuits suffer from a number of limitations, including performance degradation due to capacitor parasitic inductance and the size and cost of magnetic elements. Coupled-magnetic filters have been developed that provide increased filter order with a single magnetic component, but also suffer from parasitic inductance in the filter shunt path due to imperfectly-controlled coupling of the magnetics. In this paper, we introduce a new approach to coupled-magnetic filters that overcomes these limitations. Filter sensitivity to variations in coupling is overcome by adaptively tuning the magnetic circuit for minimum rms ripple performance with feedback based on the sensed filter output ripple. This active control enables much greater robustness to manufacturing and environmental variations than is possible in the conventional "zero-ripple" coupled-magnetic approach, while preserving its advantages. Moreover, the proposed technique also adaptively cancels the deleterious effects of capacitor parasitic inductance, thereby providing much higher filter performance than is achievable in conventional designs. The new technique is experimentally demonstrated in a dc-dc power converter application and is shown to provide high performance     

一种新型基片集成波导双模带通滤波器

综合基片集成波导和双模滤波器两种前沿技术,设计了一种新型微波带通滤波器结构,该滤波器结构简单,无载品质因数高达10 000。同时,通过使用凹型过渡方式,解决了基片集成波导与微带线的过渡问题,从而方便了滤波器和有源微波电路的集成。文章设计的滤波器中心频率在5.63 GHz,通过TE102和TE201两种模式耦合,产生一个传输零点,极大的改善了阻带效果。实验表明,通带内反射损耗S11优于25 dB,3 dB带宽达60 MHz。     

Ultralow-power GaAs MESFET MSI circuits using two-phase dynamic FETlogic

Two-phase dynamic FET logic (TDFL) gates are used in GaAs MESFET MSI circuits to implement very low power 4-b ripple carry adders and a variable modulus (2 to 31) prescaler. Operation of the adders is demonstrated at 500 MHz with an associated power dissipation of less than 1.0 mW and at 750 MHz with P_d=1.7 mW. The prescaler, which contains 166 TDFL gates and 79 static gates, is shown to operate up to 850 MHz with an associated power dissipation of 9.2 mW from its 1.0-V supply. The operation of the adders and prescalers demonstrates the use of three- and four-input TDFL gates and a completely dynamic TDFL XNOR gate. The TDFL gates in these circuits dissipate only from 14 to 20 nW/MHz     

Distributed biasing of differential RF circuits

A distributed balun is presented as an alternative to inductor-based biasing of active differential circuits. The new scheme has broad bandwidth with low loss and is suited to broad-band multifunctional RF and microwave circuits. Additionally, the distributed biasing circuit discriminates between differential and common-mode signals leading to high common-mode rejection. Measured gains, centered at 580 MHz, of a selected pseudodifferential amplifier using the new biasing circuit confirm the underlying theory.     

Low loss and high performance SAW filters for 800 MHz mobile telephone transceiver

Low loss surface acoustic wave (SAW) filters have been developed for use in the radio frequency circuits of the mobile telephone transceiver. Both the UHF (800 MHz) and VHF (90 MHz) band-pass filters have exhibited high performance, and the employment of the SAW filters has shown advantages in UHF/VHF circuit integration for mass production.     

基于基片集成波导(SIW)的双模带通滤波器

首先介绍了基片集成波导(SIW)这一新技术,并用表面电流理论解释了电磁波在SIW中的传输模式。同时,通过使用凹型过渡和接地共面波导过渡两种转换方式,解决了基片集成波导与微带线的过渡问题,从而解决了滤波器和有源微波电路的集成问题。文章用这两种过渡方式,分别设计了中心频率在5.63GHz和5.45GHz的双模带通滤波器。实验表明:这两种滤波器在通带内的反射损耗S11均优于-21dB,-3dB带宽都在50MHz以上。     

A Practical Tantalum Thin-Film Single-Sideband Demodulator Using RC Time-Varying and Active Networks

The thin-film circuit described in this paper is equivalent to a demodulator circuit containing an extremely selective filter ("sideband" filter). Such a filter would, in conventional form, require very high Q inductors or, as the Q requirement increases, the use of crystal or mechanical filters. At the frequency of operation of this circuit (1 MHz), demodulation with conventional filters would have to be accomplished in two or more stages so that the selectivity requirement can be decreased for each filter. Thin-film techniques restrict us to circuits using only resistors (R), capacitors (C), and added semiconductor devices (thin-film inductors are not considered here since their inductance values are too small). The current trend is to realize frequency selective networks (conventionally in LC form) as active RC networks. However, although the circuit described here incorporates such a network, the main selectivity requirement cannot be met by present-day active network techniques. The solution is found in the use of time-varying RC networks, i.e., by combining passive RC thin-film phase-shift networks with miniature transistors, used as electronic switches, in the form of so-called quadrature modulation circuits. The phase-shift networks, which in principle can be passive thin-film RC circuits, are in practice more easily realized as combinations of much simpler RC circuits with buffer amplifiers.     

Design tables for two active RC circuits realizing low-pass polyonimic filters

Realization of RC-active filters, as proposed by Sallen and Key, consists of cascade connection of suitable second- and first-order building blocks. The paper presents design tables for two active RC circuits realizing low-pass polyonimic filters. The functions realized are of second to eighth-order low-pass Butterworth, Chebyshev (with 0.1, 0.5, 1, 2 and 3 dB ripple) and Bessel variety. This method uses simple op-amp integrator blocks and can equally be applied to both continuous-time and switch-capacitor filter designs. The advantages of this method are: simple method of designing LP filters from second to eighth order using integrator blocks (e.g. MAX 274 and MAX 275); low sensitivity to component values; low spread in component values; good tuning; can tune parameter f ₁ (cutoff frequency). The disadvantages of this method are: no independent adjustment of the cutoff frequency and the Q-factor; fixed gain of unity.     

电磁寄生参数在高频SAW滤波器设计中的应用

在设计高频声表面波(SAW)滤波器的过程中,若只考虑封装壳和键合线的电磁寄生参数而忽略汇流条的电磁寄生参数,则SAW滤波器的实际性能易受汇流条寄生参数影响而出现通带波动和驻波增大等问题。该文拟用电声-电磁联合仿真方法设计高频SAW滤波器以解决汇流条寄生参数对SAW滤波器性能的影响。通过此方法研制的滤波器通带插入损耗小于1 dB,波动0.5 dB,通带内驻波最大值2.1,-1.5 dB带宽75.7 MHz,-3 dB带宽84 MHz (相对带宽为4.8%),-30 dB带宽112 MHz,BW_{-3 dB}/BW_{-30 dB}矩形系数1.33。包含封装壳、键合线及汇流条的寄生参数的理论仿真结果与实验测试结果吻合较好,表明了采用此模型设计高频SAW滤波器的可行性。     

Gain-sensitivity product-a figure of merit for hybrid-integrated filters using single operational amplifiers

It is shown that a different measure of performance must be used to evaluate hybrid-integrated active filters from that used to evaluate active filters in discrete form. Where sensitivity was previously found to be an adequate and useful measure for Q stability of discrete active filters, the gain-sensitivity product gives an accurate measure of Q stability for hybrid-integrated circuits. Where negative feedback filter schemes were found to be preferable with respect to Q stability when realized in discrete form, positive feedback schemes with their very much lower gain- sensitivity product may be preferable in hybrid-integrated filter circuits. In addition, they require low-gain amplifiers than can be used up to higher frequencies. Q-stability measurements of hybrid- integrated positive feedback, or Sallen-Key-type circuits, which were realized with tantalum thin-film resistors and capacitors combined with beam-leaded operational amplifier chips agree very accurately with the predictions derived from gain-sensitivity calculations.     

An active ripple filtering technique for improving common-mode inductor performance

Active ripple filtering is the replacement of large passive components in power filter circuits with smaller passive components and active control circuitry. This letter focuses on common-mode filters, where a large common-mode inductor (choke) is replaced by two smaller chokes and active op-amp control. The technique is appropriate when improved attenuation is required at relatively low frequencies and the high-frequency filtering requirements are easily met. Smaller chokes save significantly in material and winding costs. The technique is more advantageous if wire-wound chokes can be replaced by planar printed circuit board chokes. The use of the technique in an automotive electromagnetic interference (EMI) filter application is explored in detail.     

Secondary LC filter analysis and design techniques forcurrent-mode-controlled converters

Small-signal characteristics of current-mode-controlled PWM converters with a second-stage LC filter are analyzed. It is shown that a secondary filter can be designed to provide good attenuation of the switching ripple while maintaining adequate stability margins with capacitive loading. The resonant frequencies and damping coefficients of the second filter are derived, and design guidelines are given. It is shown that the current-loop gain of the buck converter is not affected by the addition of the second-stage filters when a small filter inductance is used. Three design examples are presented to demonstrate the use of analysis results. Two filter examples are designed for a buck converter. One of the second filters shows the problems that arise with a poor design. A third example is the design of a second-stage filter for a buck-boost converter. In each of the design examples, the small-signal analysis was performed using EASY5 software and the circuits were simulated using the state-space simulation program COSMIR     

一系列新的基于电流模式的二阶滤波器

本文提出了一种新的基于电流模式的二阶滤波器综合电路，适当选择电路元件，可综合出一系列电流模式二阶低通、高通和带通滤波电路，对其中部分电路进行了理论设计和灵敏度分析，结果表明本文提出的电路灵敏度低、增益可独立调节。计算机仿真结果证实了理论分析的正确性。     

Low-pass and high-pass filters using coaxial-type dielectric resonators

This paper proposes new low-pass and high-pass filters using coaxial-type dielectric resonators. The low-pass filter has a LC-type circuit structure and is composed of three inductances and two resonance circuits. The resonance circuits are the open-ended coaxial-type dielectric resonators whose length is λg/4. The high-pass filter has a CL-type circuit structure. Two high-pass filters are described, one of them is composed of three capacitances andtwo resonance circuits, the other is composed of five capacitances and four resonance circuits. The operating frequency range of the low-pass filter is 0.13–0.9 GHz and the cutoffency is 900 MHz, and the insertion loss is 0.3 dB. The corresponding quantities of the high-pass filter are 0.9–2.5 GHz, 900 MHz, and 0.3 dB, respectively.     

OXIL, A Versatile Bipolar VLSI Technology

A bipolar VLSI technology, for Oxide Isolated Logic (OXIL) circuits has been developed which combines high-frequency conventional down-transistors with inverted up-transistors which are fabricated in a common process on the same chip site. The up-transistor is especially designed to optimize I/sup 2/L circuits for high packing density, speed, and performance. High-pressure-steam oxide isolation and an up-diffused active base are combined to fabricate the up-transistor with f/sub t/ > 500 MHz and Beta = 100, which allows I/sup 2/L delays down to 3 ns at FO = 1 and 7 ns at FO = 6. The down-transistor is an oxide-isolated implanted-base transistor with an As emitter. It exhibits gains of 100-150 at f/sub t/ = 2 GHz and supports subnanosecond CML, high-current buffer circuitry, and linear interfacing.