1MHz/500kHz低噪声低通滤波器应用电路

ＬＴＣ１５６０１是一种１ＭＨｚ／５００ｋＨｚ五阶连续时间低噪声低通椭圆滤波器，适合用作抗混叠滤波器、平滑或再建滤波器以及通信滤波器等。在用于抗混叠场合时，应仔细地选择ＬＴＣ１５６０１的椭圆传递函数来实现选择性和瞬态响应之间的折衷方案。用引脚５选择...     

Δ∑调制器及其应用接口电路

ＡＤＳ１２０１是一种精密的、１３０ｄＢ动态范围、单一＋５Ｖ电源工作的Δ调制器。其差分输入对于直接连接转换器或低电平信号是理想的。用适当的数字滤波器和调制器速率，此器件可用于实现２４位模／数（Ａ／Ｄ）变换而没有误码。用１ｋＨｚ带宽数字滤波器在３２０ｋ...     

中等数据率无线通信的实用解决方案(下)

ＲＦ收发器设计 ＲＦ收发器的框图示于图２。系统的要求如下： １．频带９０２～９２８ＭＨｚ,低功率（＜０ｄＢｍ）传输,直接变换ＦＭ。 ２．数据率 ５７．６ｋｂｉｔｓ／Ｓ,全双工。 ３．数据译码／编码－ＡＭＩ。 ４峰值频偏－８０ｋＨｚ。 ５．ＲＦ带宽－３３０ｋＨｚ。 ６．信道数－５。 ７．信道间隔－５００ｋＨｚ。 ８．接收器第－ＩＦ频率－７３．７ＭＨｚ。 ９．接收器第二 ＩＦ频率－１０．７ＭＨｚ。 １０．基准频率一１１．２ＭＨｚ, ± １０ｐｐｍ,１００ｋＨｚ内部频率。 １１．收发信道δ－２１．９ＭＨｚ。 １２．系…     

星载低频机械滤波器

本文介绍了１０ｋＨｚ到３０ｋＨｚ低频段星载机械滤波器的特点，在研制过程中为保证高可靠性而采取的一系列措施和实际达到的电性能。     

声表面波调频振荡器

论述了声表面波调频振荡器的原理及设计方法，探讨了有关电路，并制作了中心频率３８０．８ＭＨｚ的声表面波调频振荡器。当调制信号频率区ＤＣ至８００ｋＨｚ变化，幅值为２．５Ｖ时，调频频偏大于５５０ｋＨｚ；当调制信号频率小于或等于２００ｋＨｚ，幅值为１．０Ｖ时，调频非线性失真小于３．５％。振荡器经过温度补偿，温度稳定性优于±１５０ｐｐｍ（－４０℃～＋５０℃）。     

低插损极窄带声表面波滤波器设计

利用集总参数等效电路模型计算了声表面波双模耦合谐振滤波器的频响．通过改变谐振器各个参量使滤波器指标满足要求．在ＳＴ石英基片上成功研制出中心频率２２８ＭＨｚ，△ｆ－３ｄＢ＝１５０ｋＨｚ，插损为３ｄＢ，阻带抑制小于－５０ｄＢ的铁路专用寻呼机用滤波器。理论计算与实验结果一致。     

铜蒸气激光泵浦掺钛蓝宝石激光器输出超过5．5W

铜蒸气激光泵浦掺钛蓝宝石激光器输出超过５．５Ｗ牛津大学和牛津激光公司已发展一种高平均功率、高重复频率铜蒸气激光泵浦掺钛蓝宝石激光器。这种激光器在６．５ｋＨｚ重复率和５５ｎｓ脉宽时平均输出５．５ＷＴＥＭ００模激光功率。泵浦激光器是带放大器的改进型Ｃｕ１...     

声表面波波导耦合双模谐振窄带滤波器

本文利用集总参数等效电路模型计算了声表面波波导耦合双模谐振窄带滤波器的频率响应。讨论了谐振器各设计参量对滤波器性能的影响。在Ｘ－１１２°ＹＬｉＴａＯ＿３基片上实验制作了中心频率１１４ＭＨｚ左右，Δｆ＿（－３ｄＢ）分别为７０ｋＨｚ和４０ｋＨｚ的二极和四极窄带滤波器。对二极滤波器，阻带抑制小于一３０ｄＢ；对四极滤波器，阻带抑制小于一５０ｄＢ；匹配后插损３ｄＢ。理论计算与实验结果一致。     

18位过采样∑△A／D变换器设计

本文介绍１８位精度音频（带宽２０ｋＨｚ）过采样∑△Ａ／Ｄ变换器．文中根据精度、阶数和过采样比关系，设计了４阶２－２结构∑△面调制器，在设计梳状抽频滤波器和波数字滤波器时分别应用了模数定理和硬件复用技术．在１．２μｍＣＭＯＳ工艺设计完成后，电路的结构和精度通过ＥＬＤＯ模拟器和Ｃ模拟器得到了验证．     

小型棒状曲振机械滤波器

本文介绍了１２５ｋＨｚ小型棒状曲振机械滤波器的设计及实际达到的性能。此种机械滤波器体积小，重量轻，在同类性能的滤波器中具有显著的优点。     

BNKLT无铅压电陶瓷梯形中频带通滤波器的研制

利用发明的[Bi0.5(Na1-x-yKxLiy)0.5]TiO3(BNKLT)系无铅压电陶瓷,采用全电极径向振动模式制作了插入损耗小于6 dB,阻带损耗大于30 dB,频率特性曲线平滑,并具有良好选择性的中频(IF=460 kHz)多节带通滤波器。与含铅压电陶瓷多节滤波器相比,BNKLT无铅压电陶瓷滤波器的特性有待进一步改进。     

A micropower fourth-order elliptical switched-capacitor low-pass filter

A micropower fourth-order elliptical switched-capacitor (SC) low-pass filter for biomedical applications has been designed and measured. The charge transfer error of an SC integrator using a transconductance amplifier is discussed. Also first-order noise and PSRR calculations are performed and compared with the results of simulations and measurements. The measurements show that by careful optimization of the gain bandwidth, slew rate, and gain of the amplifiers, high-performance low-power SC filters can be constructed. The cutoff frequency of the filter is 5 kHz, the ripple in the passband is 0.27 dB, and stopband rejection is 49 dB. The power consumption of the filter is 190 /spl mu/W with /spl plusmn/2.5-V power supplies. The dynamic range of the filter is 75 dB, and the total harmonic distortion over the whole passband range is below 0.25% for a 2-V/SUB pp/ input signal. The PSRR of the filter is above 40 dB at frequencies below 3 kHz.     

AN ANTI-ALIASING FILTER FOR ∑△ ADC

An anti-aliasing filter for ADCs using a combination of active RC and analog FIR filters is presented in this letter. The first order active RC filter is set at 100kHz to minimize the die size and variations of linear phase and gain in 0-4kHz passband. The 2-tap FIR filter provides more than -53dB attenuation at 2MHz 4kHz frequency range. The proposed filter achieved more than -76dB attenuation at sampling frequency with 0.01 phase linearity and 0.02dB gain variation within 0-4kHz bandwidth. The active die area of the fully differential filter is 0.17mm2 in 0.5um CMOS technology. The experimental and simulation results have been obtained and the feasibility of the proposed method is shown.     

MOS switched capacitor ladder filters

A new technique for designing precision, fully integrated, high-order filters using standard MOS technology is described. Switched capacitor integrators have been used to realize long time constants in small areas, and by interconnecting these integrators in a `leapfrog' configuration, monolithic high-order filters have been implemented with transfer functions that are very insensitive to component variations. Experimental results are presented for an NMOS fifth-order Chebyshev low-pass ladder filter with 0.1-dB passband ripple, a cutoff frequency of 3.4 kHz when clocked at 128 kHz, and a dynamic range of 83 dB. An efficient method for implementing transmission zeros is also presented, along with a complete design example, and additional experimental results for a third-order elliptic low-pass ladder filter which achieved 90-dB dynamic range, with a total power dissipation of 18 mW in a die area of 4400 mil/SUP 2/.     

AN ANTI-ALIASING FILTER FOR ∑△ ADC

An anti-aliasing filter for ∑△ ADCs using a combination of active RC and analog FIR filters is presented in this letter. The first order active RC filter is set at 100kHz to minimize the die size and variations of linear phase and gain in 0-4kHz passband. The 2-tap FIR filter provides more than -53dB attenuation at 2MHz ±4kHz frequency range. The proposed filter achieved more than -76dB attenuation at sampling frequency with ±0.01° phase linearity and ±0.02dB gain variation within 0-4kHz bandwidth. The active die area of the fully differential filter is 0.17mm2 in 0.5μm CMOS technology. The experimental and simulation results have been obtained and the feasibility of the proposed method is shown.     

Design of saw filters in SS-FDMA routers for mobile satellite systems

The present paper reports the design of a SAW filter bank consisting of 26 linear phase filters with bandwidths ranging from 60 to 2180 kHz, 0·5/40 dB transition width narrower than 30 kHz and stopband rejection as high as possible. Passbank amplitude and phase ripple limits are 1 dB and 4° peak-to-peak respectively. Three candidate filters of bandwidth 60 kHz, 400 kHz and 2·180 MHz were selected for detailed design, taking into account spurious effects such as acoustic regeneration and diffraction as well as technology limits. Since the physical length of a SAW filter—as any transversal (FIR) filter—is determined by (i) the required passband amplitude ripple, (ii) the stopband rejection level and (iii) the transition width, the steepness of the required passband-to-stop band transitions in these filters dictates their physical size to be unusually large, resulting in an overall size for each packaged filter of 360 × 38 × 17 mm, i.e. 14·2 × 1·5 × 0·7 inches. The electrical specifications are met by all but the 2180 kHz filter, whose shape factor, for a 30 kHz transition band, would be 1·027 : 1, beyond the state of the art. The filter bank has about 27 dB insertion loss per filter, plus roughly 14 dB (1 : 26) power split loss.     

A Mechanical Filter Channel Bank

The channel modem is encountered in carrier telephone systems in far greater quantities than any other equipment unit. Measures for improving the productivity with regard to this basic unit of equipment will thus be particularly effective. The newly developed channel modem uses mechanical filters for both the speech channel and the outband signaling. The channel filter has its passband at about 50 kHz and consists of 12 flexural vibrators with longitudinal coupling. Using the premodulation principle, only a single type of channel filter is required. Because of the simple setup of these mechanical filters, they are well-suited for automatic production. An improvement in the electrical characteristics is also achieved. The attenuation distortion in the passband of the loop-connected channel is within 1/10 of the International Telephone and Telegraph Consultative Committee (CCITT) tolerance scheme number 1 without any attenuation equalization. In addition, an essential size reduction has been accomplished. The customary bay volume will accommodate instead of the present 120 channels the channel modems for 600 voice circuits including power and carrier supplies.     

Self-contained charge-coupled split-electrode filters using a novel sensing technique

Self-contained single-chip charge-coupled split-electrode filters with 55 taps and a novel channel structure have been built with a double-level polysilicon NMOS process. Operating at a sample rate of 32 kHz, these devices provide a low-pass filter function with a passband from 0 to 3.2 kHz and a stopband above 4 kHz. The image charge on the sense electrodes is detected with a novel sensing circuit employing two on-chip operational amplifiers, one of which suppresses the common-mode signal on the two sense buses while the other one integrates the difference signal. In addition, the chips carry antialiasing prefilters, a correlated double sample-and-hold circuit to minimize reset noise and to restore the output signal, and all the necessary peripheral logic and biasing circuitry so that the devices can be operated from a single master clock and two power supplies of +12 and -5 V, respectively.     

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.     

Synthesis of filters with minimum integrated power-loss ratio in the passband

The synthesis of filters with minimum integrated power-loss ratio in the passband is reported. The experimental results obtained with the passband filters realised at microwave frequencies are discussed.