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Questions tagged [filter]

A filter selectively processes input signals in frequency- or time-domain.

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4answers
35 views

Is there a standard definition of LPF stop band starting point in terms of dB attenuation

Below illustrates a LP filter bands: I can say that the transition band starts at -3dB. But the transition band ends at some point and there the stop band starts. In this example it is -70dB they ...
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3answers
37 views

Pulse distortion low pass filter and group delay

What is really meant by pulse distortion? I have come across several paragraphs which mentions the cause of the pulse distortion is group delay. But doesn't a LP filter still distort a pulse even ...
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1answer
48 views

Regards Band Pass Filter with AmpOp

I've tried to solve this contest question regards the band pass filter (find the frequency at low-pass and high-pass filters) the picture below: My attempt: I consider that the first stage is 2 low-...
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2answers
74 views

Why won't my IIR filter work?

I have a cascaded IIR filter that has a sampling frequency of 1kHz and consist of a highpass filter with a cutoff frequency of 0.8Hz and a lowpass filter with a cutoff frequency of 5Hz. I have ...
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2answers
144 views

Understanding the exact meaning of dB/decade in a Bode plot

To make the question clear I will ask this with an example. Let's say we have a LP filter with a -3dB attenuation at cutoff frequency of 1kHz. And lets say we are given the steepness of the filter as ...
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0answers
20 views

Realizing a prototype filter in ADS or any other simulator

I'm trying to design a stub-filter, and I'm stuck on realizing the filter design using Richard's transformations and Kuroda identities. I'm building a 5th order Chebyshev LP-filter for 2.6 GHz pass-...
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2answers
80 views

How can implement a low pass filter with this PWM signal? (Deadstop Fan won't start error)

I want to low pass the signal to the fans in this circuit. PWM frequency is 35khz and I calculated that I would need C = 10 µF and R = 10 Ω But no matter how I place my capacitor and resistor, ...
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1answer
34 views

Cascaded RC Bandpass filter loading problem?

So I calculated the Highpass stage output impedance to be 22kohm and the input impedance of the Lowpass stage is 430kohm when f=5khz, still in the output I am getting half of my supply voltage despite ...
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1answer
102 views

How to generate this kind of filter?

I've been trying to understand this exercise proposed by my teacher. He asked us to find a combination of 2 ideal filters to generate a filter within the conditions of the image below. (That means, ...
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1answer
60 views

There is no math for adding the functions of two parallel filters. Or is it?

I want to add two "parallel" functions. Each of them describes the frequency response of that individual filter. Put in other words, I want to see what the frequency response looks like when the two ...
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0answers
22 views

RC bandpass filter using two port network parameters?

So my assignment is about exploring two port networks and the use of the 4 parameters, now one of the tasks is to design a bandpass filter with cascaded high pass and low pass filters, now I am really ...
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3answers
51 views

Minimizing reflection coefficient of a low-pass filter

I'm trying to figure out (with not a lot of success) as to what I need to consider when I want to minimize reflection coefficient below a certain point. I'm trying to design a low-pass shunt stub ...
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1answer
39 views

Why Deliyannis bandpass filter with high Q does not have the expected transfer function bode plot

What i need is to design a delyiannis band-pass filter with Q enhancement technique. The theoretical analysis of this technique is referred here in pages 107-112. For those who don't know how to ...
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0answers
21 views

Noise reduction and signal affect in IIR filter

I have found two equations which describe affect on signal and noise when using IIR filter: For signal: For noise: Can someone explain how to get these equations?
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3answers
77 views

Confused with voltage doubler circuit

This is how the book explains the process: Let me consider the first 90° of the input, the capacitor charges up to the peak voltage less the diode drop of D1, D1 is forward biased and D2 is reverse ...
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1answer
74 views

Purpose of high pass filter for AC Mains?

I wanted to ask what the purpose of the high pass filter does in the below circuit. Is it necessary?
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0answers
51 views

phase shift in LRC circuit

I need to use a L-R-C tank in my design and I'm having trouble with the calculations. And I think it is because of the phase shift I didn't take into account. Here you can see there is a differential ...
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2answers
72 views

Can't achieve the goals in designing and simulating Resonator circuit

Goals I need to design resonant parallel circuit and simulate it with LTSpice so that it match with the design requirements correctly. Requirements Source Impedance \$R_s = 100\ \Omega\$ Load ...
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4answers
150 views

Circuit inverts at high frequency and is unity at low frequency

Does anyone recognize this op amp setup? I've figured that at low frequencies C1 is as short circuit, putting the +ve and -ve inputs to \$V_{in}\$ and at high frequencies it will be as open circuit ...
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1answer
53 views

designing Low-Pass Transmission Line Stub Filter

I'm trying to design a Low-Pass transmission line stub filter, and I have a few question regarding it. I'm rather new to RF-circuit design, so please bear with me. If my desired specs include the ...
1
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1answer
23 views

Vdc in ripple factor

V_p(rect) is the rectified unfiltered peak voltage V_r(pp) is the peak-to-peak voltage after filtering by a capacitor Here is a picture: V_r(pp) is given by the expression: Which I have no problem ...
2
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3answers
162 views

32.768kHz crystal making audible noise

I am doing a project to record and log the voltages of an 8 cell lithium battery. The project is based on an STM32 microcontroller, and logging is done on an SD card. I have made the first version of ...
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2answers
62 views

Amplifier and Low Pass filter not responding after few minutes of correct output?

I am trying to design an amplifier and low pass filter circuit for a piezo sensor. My frequency of interest is .3 Hz to 5 Hz, for first stage I have used charge amplifier and the subsequent 3 stages ...
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3answers
100 views

High pass filter for electret mic to mobile phone

I’m currently working on making a lavalier microphone for use with my phone and gopro camera. I know these types of microphones are readily available and can be purchased fairly cheap, but where would ...
2
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2answers
121 views

Differential Equation of RC Low Pass Filter

I'm trying to analyse the following circuit to find the differential equation describing the relationship between \$V_{in}(t)\$ and \$V(t)\$: Where \$C_1 = 2uF\$, \$C_2= 1uF\$ and \$R_1=R_2=1k\Omega\$...
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2answers
106 views

How to detect a partial discharge in a noisy signal?

I am working on a competition where we are required to detect partial discharges in given signals. Each signal represents a measurement of some power-line voltage. I know that partial discharges ...
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1answer
33 views

Stuck with matching input signal to an active filter

I’m stuck at a point when trying to use this filter or a similar one from the same family. To illustrate the matter I have drawn the below two diagrams. Below F represents the filter. My aim was to ...
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1answer
70 views

RLC Low-Pass Filter with MATLAB

I'm trying to refresh my knowledge on RLC filters, and I'm using MATLAB to model it. Given an RLC circuit with the elements in series, taking the output at the capacitor should result in a 2nd-order ...
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1answer
45 views

Parallel RLC bandpass filter Bandwidth incorrect

I have been trying to create a bandpass filter with the cut-off frequency at \$\mathrm{200Hz}\$ and \$\mathrm{4800Hz}\$ I have managed to get the centre frequency to \$\mathrm{2500Hz}\$. The bandwidth ...
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1answer
58 views

Passive band-pass filter conceptual analysis

I'm trying to chain a high-pass filter and a low-pass passive filter together to form a band pass filter to illustrate how you can combine filters together, but I'm having issues trying to understand ...
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1answer
60 views

Moving summing block before integrator

I wanted to move the summing operation (+10) that I perform before the integrator block as shown below: (MODEL-1) I check in this wikibook page - https://en.wikibooks.org/wiki/Control_Systems/...
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1answer
60 views

Signed and unsigned numbers in verilog

I understand the concept of fixed point and multiplying signed with unsigned by sign extension the unsigned number with 1 bit of '0' so it will be signed always positive number, But my question If I ...
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3answers
141 views

Teaching about LC filters

I'm preparing to teach some people regarding filters, and I'm confused regarding the use of the LC-filter circuit, specifically the circuit below: simulate this circuit – Schematic created ...
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0answers
52 views

Hobby Project - Signal Frequency detector

Context: I have taken on a little side hobby project to learn by making a circuit which should be able to only go high when it sense an acoustic signal with a frequency around 40kHz. To do this I will ...
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1answer
89 views

Multiplying signed to unsigned binary numbers in verilog

How can I multiply a signed number to unsigned number in verilog for example: a = 6'b111111 ; //which is means -1 as it is signed b = 6'b111111 ; //which is means 63 as it is unsigned I want the ...
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1answer
59 views

Questions about a design for an SMPS post regulator filter circuit?

For minimizing SMPS ripple and especially noise, I’m trying to make a small interface which is a post regulator cascaded after an LC filter. I have come across some papers related to this topic and ...
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0answers
24 views

Calculating low-pass filter prototype specifications

So I'm just wondering what I need to figure out before I can actually calculate anything here, (only considering the a-part now)? I understand that 2.5 GHz should be 3dB and 3.75 GHz should have 25 dB ...
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1answer
45 views

Low Pass filter

I am making a Sallen-Key topology second order low pass filter with 10Hx cutoff frequency: I am using the LM248 op amp. The resistor and capacitor values are specified in the drawing. However, when I ...
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2answers
44 views

What does an internal or external loop filter do for this clock IC?

For the CDCE62005 clock generator IC, what does the internal or external loop filter accomplish? Thanks in advance for any input. Page 44 of datasheet, and pages 1-2 and 6 or the eval board user ...
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1answer
42 views

How to obtain the steady state response of the sampled periodic signal data?

Below the green plot Vin is 5Hz sine voltage signal from a function generator output sampled at 12kHz sampling rate: The blue plot Vout is the processed/filtered data by using the following code in ...
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2answers
107 views

Emitter follower and input impedance

I'm designing an active bandpass filter (using only BJTs, voltage sources, resistors and capacitors) with the following properties: Corner frequencies \$8 ~ \text{kHz}\$ and \$800 ~ \text{kHz}\$ (...
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0answers
83 views

Noise floor raising at high RF input power after filtering

I have a USRP b205mini with AD9364 transceiver. When it receives a very high RX input of about -5 dBm at different frequencies, not in the original RX range, the noise level raises slightly. The RX is ...
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2answers
560 views

Difference between Antenna and Filter

In RF front-ends the diagram shows an antenna followed by a band-pass filter. I am also working on a project involving a micro-strip patch antenna followed by a dual-band band-pass microwave filter. ...
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1answer
39 views

Twin notch filter working

Can someone please explain to me in depth as to how this twin notch circuit is working. Also is what is the formula for finding the notch frequency because some sites give the answer as (1/2×pi×RC) ...
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0answers
55 views

PWM signal to sine wave

I generated a PWM from Arduino and everything is fine, all was left was to filter the signal to obtain the sine wave, but to my surprise, I didn't have to... which I find wierd. I use soundcard ...
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6answers
601 views

RC Lowpass Filter between Amplifier and ADC input

I have sensors (pyranometers that consist of thermopiles and measure sun irradiation) that ouput a low voltage signal so I need to amplify them using an instrumentation amplifier. I have chosen the ...
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0answers
78 views

What happens if we give two tones to an sigma-delta ADC?

I have been working with Sigma delta ADC, where I generally use a single tone input and then check its spectrum at the output for the SNR, which is similar to as shown below: (just an example) I am ...
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0answers
25 views

Bandstop FIR Filter in Matlab

I have a problem here and I'd like some opinions. So, I need to design a Bandstop FIR filter and find its impulse response & frequency response in Matlab. I was thinking that, for the impulse ...
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2answers
52 views

Sallen-Key - how opamp input bias current changes cutoff frequency?

As in the title: what exactly is the impact of input bias current in Sallen-Key topology, for example the one below: I read that it can matter significantly, however I did not find anything more on ...
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1answer
57 views

How to find the transfer function of this first order active filter?

Going through Design with Operational Amplifiers and Analog Integrated Cricuits, in Chapter 3, problem 3.4 I am asked: The circuit of Fig. P3.4 is a noninverting differentiator. (a) Derive ...