b*******2
发帖数: 2121 | 1 本来想自己做一个,发现效果不好,bandwidth不够窄,noise太大;
后来网上找了些IC chip filter,竟然都没有卖的,厂家也不做了..
基本要求:
bandpass filter, as narrow as possible, center freq about 1kHz, 最好可调.
发现基本都没人卖这个freqency的了.
请达人推荐一个可用的啊!
泪流满面包子答谢! |
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d*******n
发帖数: 369 | 2 For MP1 and MP2, 假设input frame is 512 samples. after it is fed into 32个
bandpass PQMF filter， the output is 512 spectral components grouped into 32
banks or 512 time-domain samples?
Since the input is time-domain samples, the output of the bandpass filters
should be also time-domain samples, right? If so, quantizer will take the
output of the bandpass filters as input but the quantizer needs the input to be spectral components!!! I didn't see an FFT between the filter bank and the quantizer that |
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a**i
发帖数: 419 | 3 不是特别懂。但我理解这是用bandpass filter的响应来代替spectral components。
理论上它们携带的信息是等效的。
32
to be spectral components!!! I didn't see an FFT between the filter bank and
the quantizer that transforms the time-domain samples to frequency domain.
Confused??
time-domain input samples transformed to frequency via the bandpass filters?
bandpass filters so they are transformed to the frequency domain by the MDCT |
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a*q
发帖数: 2109 | 4 Dichroic Mirror和bandpass filter是干不同的事情的。Dichroic Mirror是用来把激
发光和荧光分开的，但是Dichroic Mirror不能完全挡住从样品反射和散射回来的激发
光（大概能挡住99％，剩下的1％足以完全超出荧光信号了），所以必需再加Bandpass
Filter（好的只能透过10^-7的激发光）。
基本上绝大多数商用机器都可以做这四种颜色，要看买的时候装了哪些激发激光（或者
用汞灯），买了哪些滤色片了。具体实现的方法有很多，一个经典的方案叫做Sedat
Filter Set（根据UCSF John Sedat的要求设计的）。这个方案用了一个四通道
Dichroic Mirror（反射上面说的每四个激发波长而且透射所有四个荧光波长），然后
有四组激发滤色片和荧光带通滤色片，可以依次对四个波长顺序成像。
http://www.chroma.com/product/complete-filter-sets/widefield-mi
在Confocal上，四个PMT同时检测是没有什么问题的，这样要是用上面的四通道
Dichroic Mirro... 阅读全帖 |
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b*******2
发帖数: 2121 | 5 我就知道个digikey..
本来想自己做个bandpass filter,搞半天不太好用,准备买一个比较合适.
想买个LTC1164-8 - Ultraselective, Low Power 8th Order Elliptic Bandpass
Filter.
digikey 没得卖了, 不知道还有哪些网站可买的?
谢谢 |
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o*b
发帖数: 70 | 6 是关于digital signal processing的问题，我专业是PE，对于我有点困难：
现在有一路模拟 750V 直流电压信号（包含360hz 和 720hz的电压谐波）被ADC转换，
由于硬件原因，这个ADC转换的采样必须是variable time step oversampling，也就是
说得到的Digital信号的time step是变化的。现在我需要在这样的digital信号后面加
一个bandpass filter。长话短说: 需要设计一个bandpass filter来处理这个time
step变化的digital信号。
请问你有没有接触过类似的带宽滤波器？能不能推荐一些相关文献？
谢谢。 |
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o*b
发帖数: 70 | 7 Actually this is the DC bus voltage for a six switches voltage source
inverter which drives a motor
The objective of designing the digital bandpass filter is to get the 360 Hz
and 720 Hz component voltages, respectively. Once the magnitude of the 360/
720 Hz component exceeds a certain voltage value, the processor will act to
achieve some protective functions.
I didn't pay much attention to the time varying characteristics, I just
assumed that the output of the ADC is a fast change digital (beca... 阅读全帖 |
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b*******e
发帖数: 88 | 8 If you are interested, please email your C.V to z*****[email protected]
#######################################################################
RF DSP Inc. is a VC funded startup located in Irvine, California. We are
still brand new but already entered into joint development with a large
company who is a leader in our target market. You will be working closely
with engineers from this large company.
We are looking for high caliber and experienced engineers with deep
understanding of wireless communica... 阅读全帖 |
|
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n*****a
发帖数: 313 | 10 Review for journal papers
Key words: CMOS Bandpass Tunable Filter Design, FIR Filters on FPGA, OPAMP
design
contact: send your background information to e******[email protected]
Based on your qualification, I will assign the manuscripts to you. |
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U*****a
发帖数: 60 | 11 applied bandpass filter already! |
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a*****y
发帖数: 269 | 12 不是太懂摄影, 不知道有没有便宜的相机,可以在镜头前面加上25mm 的bandpass
filter的?
用来作scientific purpose. 最好相机可以通过USB与计算机连接
多谢 |
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b*s
发帖数: 82482 | 13 单色CCD用的啥filter？ bandpass? 光谱波段分细了就直接上imaging spectrometer了
……
其中有几张是用冷冻单色CCD拍的，颜色是用RGB filter来合成的。我这个CCD不是液氮
冷却的，是电磁TE冷却，可以比环境温度低30摄氏度 |
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r********g
发帖数: 868 | 14 想用带通滤波器处理数据，具体怎么用请牛牛指点下。
我有采样频率为1GHz的一组数据（8192个采样点），带通滤波器是这样写的
fd = fdesign.bandpass(200000000,210000000,390000000,400000000,60,1,60,
1000000000);
filt = design(fd);
fdata = filter(filt,data);
上面滤波器的参数是没有归一化的，210MHz～390MHz的通带，1GHz的采样频率。data直
接就是采集的数据。这样处理过的数据应该是不对的。
具体应该怎么做呢？请指教
谢谢 |
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g***s
发帖数: 733 | 15 谢谢，你说不可以是指前面的filter会把后面的信号滤掉？我不用dichroic用bandpass
级联行么？
不过不管什么方法，包括你说得专门仪器，是不是都会有一个荧光光谱overlap的问题
？overlap部分的信号就没办法分开吧，会有crosstalk，我查了一下常用label的光谱
，好像如果同时三个或更多，大多会有很强的重叠，如果滤掉重叠部分，光强就太弱了。 |
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g***s
发帖数: 733 | 16 多谢，那每个荧光是不是要用bandpass filter而非dichroic mirror来分离，因为要同
时滤掉长波长和短波长的激发光背景？
有哪个商用机器可以做这个么？想了解一下内部构造。谢谢。 |
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e*r
发帖数: 1121 | 18 我需要一个0.001hz -- 10 hz bandpass filter sampling rate 50sps
matlab 的butterworth filter 不stable,总给错的结果,我也试了先low pass,再hi-
pass,仍染不稳定,改成0.005-10hz就可以了.
大家能推荐以下如和解决这个问题么?非常感激! |
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f*****0
发帖数: 489 | 19 "That is measured by passing the amplifier output through a bandpass filter
with passband of 0.1Hz to 10Hz or 0.01Hz to 10Hz. Yes, we do use an analog
filters to do that. it works fine at this low frequency. go to take a look
at some datasheets: http://focus.ti.com/lit/ds/symlink/opa2244.pdf"
I scanned through the datasheet quickly but failed to see the superduper
filter you referrenced. and would love to see how it is constructed.
so where is it on that datasheet?
"I am not very smart."
that's |
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f*****0
发帖数: 489 | 20 "That is non-sense! For many OpAmps and Instumentation Amplifiers, one
important specification is noise between 0.1Hz to 10Hz, or 0.01Hz to 10Hz.
That is measured by passing the amplifier output through a bandpass filter
with passband of 0.1Hz to 10Hz or 0.01Hz to 10Hz. Yes, we do use an analog
filters to do that. it works fine at this low frequency. go to take a look
at some datasheets: http://focus.ti.com/lit/ds/symlink/opa2244.pdf"
sorry for being persistent but where did the opa2244 datashee |
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p*****r
发帖数: 525 | 21 1. FIR 和 IIR filter FIXEDPOINT IMPLEMENTATION
哪种对Quantization noise 增加， 为什么？ 答案是IIR， 原因？
2. ANALGUE CIRCUIT了有很多INTEGRATOR， 能不能直接用 1/(1-Z^(-1)) 代替， 为什
么？
两个连着的INTEGRATOR， 1/(1-Z^(-1)) -> 1/(1-Z^(-1)) , 能直接实现吗？ 为什
么不能？
3. Bandpass signal， 比如carrier = 1GHZ, 带宽比如200KHz. 不考虑其他的BLOCK
signal, adjaceng interferer. 能不能用直接200KHZ sample rate, decretize. 用
NYQUIST定理， 理论上是没有ALIAS的。 为什么不能直接用 200KHZ 采样？
3. Complex MIXER
PLL信号 exp(j*w_c*t + c*sin(w_m*t)), c and w_m 都很小， 远小于 w_c, 频谱是
真么样的，如果PLL信号frequenc |
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g******u
发帖数: 3060 | 22 Why don't you go to Linear's website and search some filter building blocks?
like LTC1060, LTC1061 etc, I think you can easy configure it to be 1khz band
pass, and can go up to 6th order or so. |
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b*******2
发帖数: 2121 | 23 恩,这几个我都在linear website request sample了. 在等待shipping 中.
可是感觉还是有点达不到我需要的要求.希望会work吧..
我需要bandwidth 非常非常的narrow.
我最开始找的是LTC1164-8, 50dB Attenuation at ±4% of Center Frequency. 这是
我最想要的. 可是linear 网站上没有卖的了,其他网站也没看到,好像不生产了.
不知道还有没有其他推荐?
多谢
blocks?
band |
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g******u
发帖数: 3060 | 24 you can still cascade a few 1160 or so to make a higher order one with
narrow bandwidth.
What you should do is call a Linear's guy asking the replacement for that
1164 chip. |
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g*z
发帖数: 124 | 25 If the freq is just 1khz, why don't u sample with a sound card and do what
ever DSP u can do in the digital world? |
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c****o
发帖数: 49 | 26 IIR or FIR? I can help you with it. contact me via c****[email protected] |
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c****o
发帖数: 49 | 27 what happens is ur filter is operating on high sample rate, so coefs will
not converge... filter taps = (80/22)*fs/f_transition. conclusion is, boy u
need to do sth smart |
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H***F
发帖数: 2501 | 29 这就绝对了。bandpass类型的放大器，5级都没问题
lz 赶紧跳，记得当年上课教授说过，amp最多三级，四级放大根本不现实，没法stable |
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b*******e
发帖数: 88 | 30 If you are interested, please email your C.V to z*****[email protected]
#################################################################
RF DSP Inc. is a VC funded startup located in Irvine, California. We are
still brand new but already entered into joint development with a large
company who is a leader in our target market. You will be working closely
with engineers from this large company. We can't release the name of this
company due to NDA.
We are looking for high caliber and experienced enginee... 阅读全帖 |
|
a***k
发帖数: 1038 | 31 随便找个UV bandpass filter 就是了。最便宜的是那种掺杂的紫外玻璃，整个紫外区
都是透明，但肉眼看起来就是黑色的。
不吸收。
透明的太阳眼镜，对紫外线的吸收在99.9%以上。大多数透明塑料，对紫外线的吸收也
极高。
收的黑色的物体是可能存在的。不过正常的材料，往往对紫外线吸收都更强，所以这种
对紫外线不吸收的黑色的材料，我老还没见过。哪位要是知道，不妨告诉我一声，我老
发200个伪币作谢。 |
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