微波单片有源滤波器负阻电路的实现方法

论述了用于微波单片有源滤波器负阻电路的实现方法，给出了三种由单管ＦＥＴ构成的负阻电路，以及用ＭＭＩＣ工艺能够实现的矩形螺旋电感与ＦＥＴ实现的负阻电路，并对电路进行了详细的分析与计算机模拟，分析与模拟结果显示用单管ＦＥＴ实现的负阻电路结构简单，在谐振频率点，最大负阻值可达几千欧姆，而且，综合出的负阻电路完全可以用现有的ＭＭＩＣ工艺实现，为进一步设计微波有源滤波器打下了良好的基础。     

负电阻及其应用

负电阻是一种满足欧姆定律的有源元件,它具有中和正电阻的作用。本文讨论了负电阻实现电路及其应用要点,给出了负电阻在负阻抗缓冲器、高输入阻抗放大器以及LC振荡电路中的应用。上述分析结果可供讲授电路课程和开设电路实验的教师参考。     

负电阻及其串并联电路连接

负电阻不是实际存在的电路器件,但它可以通过运放和其它电路元件来实现。本文给出了负电阻的实现方法,讨论了负电阻和负电阻的串并联连接以及负电阻和正电阻的串并联连接,给出了运算放大器工作于线性区的条件。在存在负电阻的电阻串并联等效变换中,负电阻的处理方法与正电阻一致。     

用雪崩三极管电路生成高压负脉冲技术研究

雪崩效应因为能在极短时间内输出极大电流,常被用来设计高压脉冲电路。分析了利用雪崩三极管电路生成高压正脉冲的实现方案,并提出了改进的设计,接着分析了脉冲输出过程中负载回路的电流流向,通过改变信号输出点,设计了输出高压负脉冲的电路。电路输出的脉冲幅度达到了-200V,前沿约3.2ns。与相似结构的正脉冲电路相比,性能略有降低。同时对性能下降的原因进行了分析。     

基于多级不对称耦合器负群延时电路研究

提出了一种基于多级不对称耦合器结构的负群延时电路。通过合理设置耦合器的耦合系数,可以在多节耦合线耦合器的耦合端得到带宽较宽的负群延时效果,和采用集总电阻、电容元器件构成的带阻结构的传统负群延时电路相比,该电路设计全部采用分布式耦合微带线实现,集成化程度高,插入损耗小、可应用于更高的频段。此电路结构可广泛用于功率放大器前端,用以提高放大器的效率。     

连续小波变换开关电流电路的实现

提出了一种用开关电流电路实现连续小波变换的方法,将连续小波变换转化为用带通滤波器组对信号进行处理,并用开关电流电路实现该带通滤波器组.文章采用基于第二代开关电流技术的带通滤波器组实现了8通道的Marr小波.仿真结果表明该滤波器组具有恒Q值,且每个带通滤波器的中心频率与理论值大致相符,从而证实了该方法的可行性.     

基于PSpice的电路优化设计方法的研究与应用

提出了一种将PSpice的参数扫描分析和优化分析结合起来对电路进行最优化设计的新方法．即先用参数扫描分析实现电路的次优化设计．再用优化分析实现电路的最优化设计。给出了应用该方法实现带通滤波器电路最优化设计的流程和仿真结果，实验结果表明滤波器电路的最优化设计不仅能完全满足性能指标的要求，而且还可以降低优化迭代运算和仿真执行的次数，提高优化设计的效率和准确性，同时也验证了该方法对电路进行最优化设计是有效和可行的。     

应用于匹配网络的负阻抗变换器研究

根据非福斯特电路的负阻抗变换特性,研究了有源宽带匹配网络。采用晶体管设计负阻抗变换器(NIC),结合传输矩阵对电路进行了分析。通过仿真和实验测试实现了在10～100MHz频率范围内的负电抗变换,其中20～60MHz频率范围内转换效率大于90%,测试结果与模拟结果基本一致,验证了负阻抗变换器的可行性和有效性。利用该电路结构能够对电小天线进行宽带匹配,提高天线的工作带宽和辐射性能。     

电小天线匹配网络中负阻抗变换器的研究

根据非福斯特电路的负阻抗变换特性,研究了有源宽带匹配网络。采用晶体管设计负阻抗变换器,结合传输矩阵对网络电路进行了分析。通过仿真和实验实现了在10~100 MHz的负电抗变换。结果表明,该电路20~60MHz转换效率大于90%,测试结果与模拟结果基本一致,验证了负阻抗变换器的可行性和有效性。利用该电路结构能够对电小天线进行宽带匹配,提高天线的工作带宽和辐射性能。     

基于LTCC技术的带通滤波器分析与设计

文章介绍了一种中心频率为2.45GHz的LTCC多层带通滤波器的设计方法。利用二阶耦合谐振带通滤波器的原型,通过一种分析合成带通滤波器的方法,将原型电路等效为4个L型匹配电路,设定其中两个匹配品质因子,经过推导并进行参数值取舍后,即可得到原型电路中所有元件的合成公式以及电路中各器件的参数值。利用三维电磁场仿真软件HFSS建立模型,可以将电磁模拟结果与电路仿真结果较好地吻合。最后采用标准LTCC工艺实现出尺寸为3.6mm×2.9mm×1.1mm的带通滤波器。     

非等长微带SIR平行耦合带通滤波器的设计

本文提出应用非等长微带SIR（阶梯阻抗谐振器）构成平行耦合带通滤波电路的设计方法。它保持等长SIR滤波电路能够有效抑制高次谐波的特点，又增加了设计的灵活性。本文同时给出应用级联矩阵计算这种滤波电路工作衰减的公式．可以方便地分析宽范围的频率响应。     

A generalization of nonuniform bandpass sampling

Nth-order nonuniform sampling is described for generalized bandpass signal frequency position, bandwidth, sampling rate, frequency-shift and phase-shift. A bandpass extension to the Nyquist criterion is derived, showing that restrictions on bandpass frequency position for odd orders of nonuniform sampling tend to zero as N tends to infinity. Bandpass interpolants based on the sinc function are derived for the generalized Nth-order sampled bandpass signals. It is shown that, for minimum (Nyquist) rate sampling, these interpolants are comprised of N bandpass filters, each with independent phase. The number of bandpass filters comprising the interpolant is found to decrease as the sample rate increases. The advantage of describing Nth-order sampling as the Nth replication and uniform sampling of a signal is demonstrated. Finally, digital implementation of the Nth-order bandpass sampling interpolants is discussed. It is established that it is not practicable to attempt to perform nonuniform bandpass sampling at the theoretical minimum rate, where the interpolation is to be performed digitally     

A Time-Based Bandpass ADC Using Time-Interleaved Voltage-Controlled Oscillators

In this paper, a bandpass analog-to-digital converter (ADC) based on time-interleaved oversampled ADC is introduced. Unlike previous delta–sigma bandpass ADCs that require accurate digital-to-analog converters and high-speed analog circuits, the proposed architecture provides bandpass function by time-interleaving first-order voltage-controlled-oscillator (VCO)-based ADCs. The use of VCO-based ADC has the advantage that its resolution is determined by the time resolution rather than the voltage resolution, thus making it attractive for future low-voltage CMOS processes. The performance of the proposed ADC is theoretically analyzed and simulated in ideal condition, as well as in nonideal condition, in the presence of nonlinearity, sampling clock jitter, and mismatch.      

傅里叶变换轮廓术中带通滤波器窗口参数的自动选取方法

频域带通滤波器是傅里叶变换轮廓术(FTP)中的一个重要环节。考虑到FTP系统光学结构和相关参数的变化,本文提出了一种FTP轮廓术中带通滤波器窗口参数的自动选取方法。该方法只利用一帧变形条纹图,对变形条纹图像的傅里叶频谱进行数值微分,粗略找到基频中心的初始位置;然后,利用图像直方图和阈值分割技术处理傅里叶频谱,获取带通滤波器的中心频率和带宽,实现频域滤波的自动化处理。该方法能自动适应FTP系统光学结构和相关参数的变化,使傅里叶变换轮廓术发挥其动态测量的优势,在三维光学测量工程应用中有较大实用价值。计算机模拟实验和实测结果均验证了本文方法的有效性。      

一种新型微带Hairpin带通滤波器的设计

通过在Hairp in滤波器的非相邻谐振间并联一段长度为λ0/2奇数倍的微带线使得在滤波器的通带两侧产生一对传输零点,构成一种新的微带Hairp in带通滤波器。该类滤波器的设计避免了交叉耦合带通滤波器求解耦合系数的复杂过程。最后给出了该类型滤波器的设计实例,仿真、测试结果证实了设计方法的正确性。     

Identification of cubically nonlinear systems excited by bandpass inputs

Identification of cubically nonlinear systems excited by bandpass inputs using discrete-time samples of the input and output signals is investigated. When excited by a bandpass signal, a nonlinear system may generate an output signal which occupies multiple frequency bands. Therefore, although the input signal can be bandpass sampled without causing aliasing by following the well known bandpass sampling theorem, the output signal must obey more sophisticated bandpass sampling criteria to avoid aliasing. Specifically, when a cubically nonlinear system is excited by a bandpass input signal whose highest frequency is larger than three times its bandwidth, a proper bandpass sampling frequency without causing aliasing in the sampled output signal must be at least 18 times the bandwidth of the input signal. First, a method for identifying the cubically nonlinear system using properly bandpass sampled data is developed. Then, a novel method is proposed, which allows identification of the cubically nonlinear system using data sampled at about twice the bandwidth of the input signal, even though aliasing exists in the sampled output under these circumstances. Compared to conventional methods, the proposed methods have the advantage of requiring a lower sampling rate. This makes the proposed methods highly appreciated in situations where high-speed sampling is unattainable.     

A novel method for down-conversion of multiple bandpass signals

Simultaneous down-conversion of multiple band-pass signals is desirable for a number of wireless applications. Bandpass sampling technique can be used for this purpose, but it is difficult to implement and has several drawbacks. In this paper we propose a novel front-end technique to directly down-convert multiple frequency- division multiplexed (FDM) signals separated by certain minimum frequency. A special downconversion function is derived to achieve simultaneous downconversion of the received signals. The technique requires simpler bandpass filters and the ADC has a baseband input as compared to bandpass sampling, which imposes strict requirements on bandpass filters and requires an ADC which can handle RF inputs. The performance of the method has been evaluated by simulating a BPSK receiver employing this technique.     

微带SIR带通滤波电路寄生通带的分析

本文分析微带SIR（阶梯阻抗谐振器）带通滤波电路的寄生通带问题。这种滤波器的特点是其寄生响应时以通过阻抗比K进行控制，因而增进了谐波抑制性能。SIR可以采用等电长度或非等电长度。等电长度SIR滤波电路的第三寄生通带的带宽来零，然而，非等电长度SIR滤波电路却增加了设计的灵活性，分析与探讨微带SIR滤波电路的寄生带通问题，对于合理设计与应用这种滤波电路是有益的。     

基于1 bit时间调制技术的功率控制方法

针对传统数控衰减器结构复杂、控制信号路数多的问题,提出了一种基于1 bit时间调制技术的功率控制方法. 通过对1 bit移相器0°和180°两种状态占空比的调节,该方法可以有效实现对输入信号基波功率的动态控制,利用带通滤波器抑制多余谐波后其可具备数控衰减器的功能. 还进一步讨论了调制信号时间精度对不同衰减量和不同调制频率的约束. 仿真和实验结果验证了所提功率控制方法的有效性. 相比于传统数字控制衰减器级联网络和多路控制信号的结构,本文方法只需一个调制模块和两路控制信号即可实现多种衰减状态可调的功能,因此具备结构简单的优势.     

High-selectivity grounded capacitor bandpass/low-pass filters using the operational amplifier pole

Using the single-pole model of the operational amplifier (OA) a grounded capacitor network has been analyzed to yield either a bandpass or a low-pass function by adjustment of a single resistor. The bandpass/low-pass filters are suitable for high selectivity applications at extended frequency ranges with the advantage of independent adjustment of pole-frequency, pole-Q factor, and midband/passband transmission gain. The network has low sensitivity to all the circuit parameters. The experimental results are quite in agreement with the analysis.