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Questions tagged [band-pass]

Bandpass is an adjective that describes a type of filter or filtering process; it is to be distinguished from passband, which refers to the actual portion of affected spectrum. Hence, one might say "A dual bandpass filter has two passbands." A bandpass signal is a signal containing a band of frequencies not adjacent to zero frequency, such as a signal that comes out of a bandpass filter.

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Why is superheterodyning better than direct conversion?

What is the advantage of having the extra stage of IF, extra local oscillator and extra filtering stage and amplification. It just seems like more work and circuitry. Surely the direct conversion to ...
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“Top coupling” in VHF bandpass filter

I am looking at a filter design in the ARRL handbook for radio communications. It is a bandpass filter designed to pass 144Mhz with a bandwidth of around 12Mhz. The solid line represents a shield to ...
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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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Designing a circuit from a transfer function

I have this transfer function of a bandpass filter with 2 poles and 2 zeros: $$ H(s)= 10^{-0.8} \frac{\left( \dfrac{s}{10} +1 \right) \left( \dfrac{s}{100.000} +1 \right)} {\left( \dfrac{s}{100} +1 \...
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Picking the right opamp

I've been designing some active bandpass filters and, while in simulations it works great with ideal op amps, I'm not sure how to go about picking an op amp from a distributor. Obviously there are an ...
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288 views

Twin-T filter decay rate (drum circuit)

I'm building a Twin-T active bandpass filter as shown on this schematic: simulate this circuit – Schematic created using CircuitLab My aim is to build a simple drum-like synthesizer that ...
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Order of the filter

I can't seem to figure out the order of the filter. With the knowledge i have, "The order of the filter depends on how much change there is in the (20x)dB/decade in the amplitude response." If it ...
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294 views

Designing 4th order Butterworth Multiple feedback bandpass filter

I'm trying to design a 4th order Butterworth bandpass filter using Multiple feedback topology. The design requirements I am trying to achieve for this filter are; Q factor = 10, Av = 11, fc = 100kHz ,...
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Why is center frequency of a bandpass filter is given by the geometric average of the two cutoff frequencies?

In electronic communication systems, there is a concept called center frequency. A bandpass filter has upper cutoff and lower cutoff frequencies. Center frequency supposed to be in the middle of these....
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Are these two circuits the same?

Are these rwo circuits the same considering the right hand sides of them where it is parallel for the C&R and C&L(meaning the way i should obtain the frequency response? And for the longer ...
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Parametric Equalizer with State Variable Filter

I'm new to this forum but hope to get some answers to a project I'm working on. I'm trying to build an parametric equalizer with several bands (5 Bass-Bands, 3 Middle-Bands, 3 High-Bands). In the ...
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Band Pass Filter for musical note separation

I have a school project that i need to separate musical notes with filters at least i thought that i can do it with band pass filter, here are the results These are the resistor and capacitor values ...
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Pole/Zero plot is the same for passive and active (w/ gain) bandpass filter, why?

I have designed an active inverting bandpass filter, and when comparing its pole zero plot to a passive bandpass fitler with the same cutoff frequencys, the pole zero plot is exactly the same, even ...
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Analysing a band pass sallen key filter

I'm trying to understand the transfer function of the band pass sallen key filter, which looks like: With the following circuit: How can I analyse it to get the transfer function? Thanks for any ...
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Filter for radio receivers

I am in need of an intermediate frequency (IF filter) for somewhere around 200 Khz as intermediate frequency. However, I know just the bare minimum of filter design ( learnt all that a couple of days ...
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LTSpice Transconductance Amplifier Simulation

I'm trying to simulate a band-pass transconductance amplifier in LTSpice, which looks like this: I used the recommendations of this post - https://electronics.stackexchange.com/a/278870/87695 - and ...
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Sallen-key second order bandpass filter low frequency response

I have designed a Sallen-Key bandpass filter with a centre frequency of 5000 Hz, a Q factor of 2 and an H0 of 5. I am trying to figure out why it responds as seen here to square wave with a ...
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Do narrow-band single-chip bandpass filters for audio frequencies exist?

I am looking for a single-chip implementation of a bandpass filter for audio frequencies, but unsure if they even exist. All the filters I've seen seem to be at least in hundred KHz range. So my ...
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Low capacitance value capacitors in LC bandpass filter

I am going to try to build a Butterworth LC bandpass filter. However, using some online calculators result in some very low value capacitors (sub-1pF). I am thinking that the performance will not be ...
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Why is the input reflection signal very weak?

I built a PCB filter in Class "Band-pass" with center frequency of 2.4 GHz. The board has two SMA's (input 1 & output 2). S(1,2) looks like this: The frequency is good, However, the attenuation ...
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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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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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Designing a Band Pass Filter

I need a band pass filter that only accepts frequencies from 1000 to 1400 Hz and then toggles the transistor. It has to work from .1 Vpp to 1 Vpp and rejects anything else. I have been testing this ...
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Active band pass filter that looks like a sallen–Key topology filter

I was using the Analog Devices design Wizzard in order to design a band pass filter with theese characteristics: Gain : 23 dB Passband: -3dB at 15 KHz Stopband: -40dB at 40 KHz The filter has 4 ...
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Band Pass Filter Equivalent Components

I am designing a very simple first-order RC band pass filter with cutoff frequencies \$f_l = 0.5 MHz\$ and \$f_h = 4.5MHz\$. I have it pictured below (I'm using 5Spice): This filter acts the way I ...
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Fourth-order bandpass filter Bessel - I can not solve the final part (math accounts)

With the previous gain function you calculated, design a Bessel fourth-order bandpass filter with center frequency \$f0 = 10 kHz\$ and bandwidth \$Bf = f0/10\$. I did the calculations with the ...
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Problems with implementation of a band-stop filter on an MCU (dsPIC) using fixed-point arithmetic

I'm trying to implement a band-stop (notch) filter on a microcontroller dsPIC33EP64GS506 to filter out a 100 Hz component from ...
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Band-pass filter doesn't work

simulate this circuit – Schematic created using CircuitLab I designed this as it would pass frequencies between 400-600 Hz. But it passes every single frequency anyway. What is the problem?
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663 views

Second Order Bandpass Filter vs Second Order High Pass and Low Pass in Series

Is using a second order bandpass filter less effective than using a second order high pass filter and a second order low pass filter one after the other? I tried a bandpass filter to filter out ...
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651 views

Advice on 4th-Order Bandpass Filter

I am trying to design a 4th-Order bandpass filter with the following specifications; centre frequency 30 MHz, bandwidth 5 MHz and of course minimising loss. I present my current design below which I ...
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213 views

Single ended active bandpass filter

I've designed an active bandpass filter based on the one described in this article http://www.bu.edu/eng/courses/ek307/documents/ActiveFilterNotes.pdf (section 13.3.4). However, I want to use a single ...
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AC voltage through a capacitor

I've built a band pass filter to detect speed using a radar motion detector (IPM-165 http://nic.ath.cx/PDF/sensors/radar/CDM324-doppler/InnoSenT/InnoSenT_application_note_III_11_06.pdf). Using PSpice ...
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Grounding oscilloscope probe effects

I have built an active band-pass filter on a breadboard with the use of an MC33078p op amp. Gain is 32 on paper. When I apply the AC signal to the circuit, 18.1mV P-P and 660kHz, the oscilloscope ...
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Filter-Amplifier circuit for Low Voltage I/P circuitry

I'm designing my first ever circuit for a hobby project. I've a sensor that outputs in mV (1 to 2) and a controller with ADC. The ADC is 16 bits, VDDA = 3.0 V, Temp = 25 °C, fADCK = 1.0 MHz. Since the ...
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Band pass filter implementation using 741 op amp

My assignment for a school project on Circuit Theory, is to construct a Band Pass Filter at least 3rd order with a stop band around 20kHz. First things first, I need to design the circuit. I have to ...
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Completely different circuit response with 1000kΩ than with 1MΩ resistance

I have the following circuit (a band-pass filter) and I cannot understand what's the difference of a 1000kΩ resistance to a 1MΩ as seen here: With R223 = 1000k, my circuit outputs the expected ...
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LCR circuit with squarewave input: Why does the output take a decreasing amplitude through each cycle?

I understand a square-wave will be made up of a sum of sine waves in the form $$\frac{1}{n}sin(nf_0)$$ So when a squarewave is input to a LCR circut designed to be a bandpass filter, it will ...
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Digitally selectable filter

I have asked a similar question but I did not get an answer, as it was too specific. So I will build on it but make it a bit more broad spectrum. I would like to make a digitally selectable BPF using ...
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Tradeoffs for creating higher order butterworth filters

I am working on a bandpass filter to filter the output from a hydrophone. This is my first time designing a filter and using a cookbook from TI, I built a 4th order Butterworth filter with two partial ...
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Transfer function of a bandpass

i was doing some homework and one thing I had to do was to derivate the transfer function of a given bandPass. I have done it myself but i dont know if it is correct nor if i followed the right path / ...
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Can a filter change the frequency of the input signal?

I am given a square wave with Vmin = 0V and Vmax=5V , T(period)=8ms and duty cycle 25%. I am asked to find the properties(low cutoff , high cutoff , bandwidth) of a band pass filter that will make the ...
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1answer
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How could I design a circuit for a solar panel so that it only produces output from a red laser?

I'm designing a little laser tag system with some arduino's as a little project for Christmas break and I'm having trouble figuring out how to make my solar panel receive information from my laser ...
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Ultrasonic transducer actual bandwidth for filtering

I have a pair of ultrasonic transducers with a "Thick Resonant frequency" of 975 kHz ±30kHz according to the data sheet. I did a frequency sweep test where I could see that they performed best at a ...
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Butterworth bandpass - higher roll-off than expected

I am looking into filters, and i am using FilterLab and MATLAB's Filter designer. I know that i need to make a bandpass filter, with a roll-off of about 48 dB/octave. This is quite high, and i would ...
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Impedance calculation

How can I calculate this band-pass filter input impedance? I know from the datasheet that the Ri and the R0 of the ampop are 2M\$\Omega\$ and 75 \$\Omega\$ and the Gain at the central frequency is 30 ...
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What bandpass Q factor do I want for 12dB/octave roll off?

Sorry for what may be a dumb question. I'm used to thinking about low and high pass filters in terms of db/octave (e.g. 6db for passive RC filter). Whats the equivalent Q factor for a bandpass ...
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Bandpass Filter Attenuation?

I'm trying to split an audio signal into 5 channels, letting 5 different ranges through each filter (low, mids, highs, etc..). What I'm finding is that each bandpass filter has different levels of ...
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Determining cut offs frequencies of band-pass filter

I have an RC network as follows: simulate this circuit – Schematic created using CircuitLab As far as I can tell, this has the transfer characteristic: $$ \begin{align} \frac{V_{out}}{V_{in}}=...
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How do I create a working bandpass filter in LTSpice?

I am attempting to create a bandpass filter in LTSpice. I am fairly new to the program, which is probably contributing to my difficulties. The filter I am creating needs to have a center frequency of ...
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Band pass filter , component values

The input of the band pass filter is 30Khz triangular wave of 1Vpp. I want the band pass filter to allow 27k-33k Hz . I have used these values based on the formulas I found online for this band pass ...