# Questions tagged [filter]

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

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### FIR Lattice Filters

In DSP, sometimes the so-called Lattice Filters are use, having a structure like on this picture: I wonder what the advantages of the Lattice structure are, compared to other FIR filter types and ...
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### Inverter EMI filter design

I'm designing an inverter with a switching frequency range of 10-40kHz. The inverter will run off of a DC power supply at a relatively low voltage (30-80VDC) and low power (~100W) for motor control ...
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### Is my IIR implementation (in C) correct for this difference equation?

I recently started developing a digital regulator for a DCM boost (Digital regulator for DCM Boost - How does it relate to duty cycle?) And I've implemented the difference the following controller in ...
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### 100kHz active filter design

I am designing a basic 100kHz active bandpass filter using opamps (LF353). I am only interested in receiving the 100kHz frequency (might drift a few kHz) from my input signal. I have used a basic ...
117 views

### LTI system: can I infer the system is causal based only on the transfer function without the ROC?

Suppose we have an linear time-invariant (LTI) system which acts on discrete signals. Suppose someone tells us the transfer function is: $$H(z) = \frac{1}{z-2},$$ but doesn't specify the ROC. Now the ...
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### Square vs Round Air-core Inductors for RF filters: When would you use one vs. the other?

The Kyocera AS-series Square Core Inductors boast that "the unique square cross section of the air core inductor provides better performance, and offers manufacturing advantages over toroidal ...
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### How to subtract gravity from raw acceleration of an MPU9250 - 9DOF IMU

I'm working with an MPU9250 and using the Madgwick Filter. For what I know I need to subtract the GRAVITY from my X, Y, Z Acceleration values, basically, some kind of gravity compensation to get ...
307 views

### Designing an audio amplifier, problems with bandpass filter

I am trying to build a Audio amplifier for a university project, I think that most of my circuit is done but I have an issue with my filter as my sine signal is not symmetrical after filtering to ...
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### DDS reconstruction filter after amplifier?

I need a clean sine wave from 10 kHz to 2 MHz as an excitation source for an eddy current probe. The sine wave will be generated by an AD9833 DDS with a clock frequency of 25 MHz. As a reconstruction ...
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### AD9361: how to compute datarate and configure filters

I will use AD9361 as a transmitter of a modulated baseband signal. The modulated baseband signal is implemented in FPGA/SDK. AD9361 has real-time bandwidth of 56MHz but we have maximum 61.44 MSPS data ...
• 31
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### Sanity check on this DAC reconstruction filter design

I've altered a reconstruction filter circuit to use the LTC728XT instead of the AD8608 op-amp used in the example circuit below. Is anyone able to see any issues with my attempt? This is being used as ...
116 views

I'm studying filter. I saw the filter in book. Therefore, I designed the circuit in the LTSpice for understanding the circuit. However, I do not clearly understand whether the filter is bandpass or ...
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### Digital filters that can be applied to both static and dynamic measurements

Is there a digital filter that can be applied to both static and dynamic measurements WITHOUT changing the parameters of the digital filter? For example I made a temperature measuring device that can ...
160 views

### LC filter synthesis, given transfer function (by expressing driving point impedance as continued fraction)

I want to know how to synthesise a passive LC circuit to implement an arbitrary known transfer function. (I understand that not all functions are suitable, so let's assume $T(s)$ is a positive real ...
234 views

### How would you design a power divider with 50-Ohm unbalanced input and 4x 100-Ohm balanced output impedances to send RF down a CAT6 cable?

A CAT6 cable has 4 balanced pairs, each at 100 Ohm. I'm wondering if I can make a 50-Ohm coax unbalanced input and split the power to 4x 100-Ohm balanced output (and then merge it back together the ...
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### RC Debounce: Is there a benefit to placing the capacitor in parallel with the switch?

I've always seen RC debounce circuits drawn wire the capacitor tied to the same potential as the switch. E.g. if the switch is high-side, the cap is high-side if the switch is low-side, the cap is ...
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### Series variable resistance with NPN transistor

i'm trying to build a symple voltage controlled low pass filter and in the design they ask for a transconductance amplifier (which works as a series resistance in the R C pair for the passive low pass)...
56 views

### Circuit operation

I have the below input protection and filter circuit. I want to understand how it works. Can someone tell me the purpose of R0101 and D0102 and D0104? As far as my understanding level, when the ...
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### Experimental tips RC second order circuit

I'm implementing a RC second order filter in the lab. My results were quite good, but of course not exactly equal to the simulation and theoretical prediction. I'm trying to understand why this is ...
• 1,403
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### Why is the prewarping not working as it should?

Just playing around with the 'c2d' command from matlab and trying to convert a continuous 2nd - order lowpass Butterworth function to a digital one which has the specs of Fc = 20e3Hz and Fs = 44....
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I have an ADC circuit which uses AD7689. The inputs of the ADC are driven by LT6010 opamp, and have a low pass filter . All 8 channels of the ADC (AD7689) have the same driving circuit. Every other ...
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### Problem understanding transfer functions of second order filters

The transfer function of any second order filter can be found by analyzing the circuit using the Laplace transform. For example the transfer function of a second order low pass passive RLC filter ...
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### How to amplify the output of a digital low pass filter?

I have used the transfer function of a RC low pass filter to design a IIR Digital low pass filter. $$H(s)= \frac{1}{sRC+1} ;First \space order$$ H(s)= \...
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### What is this LC circuit for?

I was looking through an STM32 development board schematic and found a circuit I don't understand. The circuit is a ferrite bead (120 Ohms at 100MHz) in parallel with 4 100nF capacitors. This is ...
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### Strange leak problem in simple tone control circuit

I built the following circuit (physically): V1 is my audio signal and the circuit is a simple tone and volume control. When both the volume and the tone pot are turned all the way down (so each wiper ...
139 views

### Can a Capacitance Multiplier be used with high voltage outputs?

I am designing an SMPS which two output voltages of 5kV and 2.5kV. My transformer is split into four equal sections, each feeding a FB multiplier, connected in series to form the final voltages. ...
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### Reed Switch False Activations

I have a DIY weather station connected to a Davis Rain Collector (6463). The device is connected to the mains in my barn (separate 100 amp leg from the house). On that same mains I have 2 high powered ...
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### How to remove DC power supply noise while load is active?

I'm using a breadboard power supply to power up two STM32F103, two Hall flow sensors, one IC555, and one 16x2 LCD with backlight. While everything is connected I have alot of noise in the system which ...
279 views

### Buffer amplifier/filter type circuit

The circuit I designed is a buffer amplifier type design intended to take two channels of audio input from a passive monitor controller, send to either the resistor circuit or low-pass filter (as seen ...
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### Parasitic Passbands in distributed filters

it is known that if we realize a filter (for instance a low pass filter) by using distributed elements (transmission lines), there will be some parasitic passbands (which moreover show a behaviour ...
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### 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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### RC filter - compute output as a function of input for generating waveform

I'm not so deeply into the theory about all this, I may use strange terminology... If I put a square wave through a simple lowpass RC filter, the output will be a sort of "rounded sawtooth", well not ...
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### Using SPICE to model dV/dt filter for inverter motor drives

I am starting to learn LTSPICE to create model where I can test various passive filter topologies for inverter drives where the output PWM has very short rise times and high switching frequency. I ...
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### I need to calculate the average power spectral density after passing packets through a butterworth filter using MATLAB

I am trying to generate 100 packets(row vectors each of size 8192) of random bits(1,-1),filter them using butterworth filter and then plot their average power spectral density. I have to do this using ...
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### Coupling vs Decoupling filter / Filter in-the-signal-path vs filter on-the-signal-path

I'm looking at designing an active analog filter module to be used/reused in my designs. Correct me if I'm wrong, but you can design a filter that is in the signal path that has the same frequency ...
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### Controlling the current through a Diode Bridge VCF

I'm investigating different analog low pass filter circuits and came across this Yamaha patent which ingeniously utilizes a diode bridge as a variable resistor. It takes some reading but in short: ...
1 vote
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### Bandpass Amplifier

This is my frequency response , the point is if i change the capacitor values C1 and C4 my signal distorts on the second lobe in time domain and gain curve is not flat in the range. MY bandwidth is in ...
1 vote
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### Transistor specs in the capacitance multiplier

I'm working on a constant current power supply and as a first step designed the following rectifier with a filter. I know the bottom rectifier is inactive, but with couple of switches the circuit ...
1 vote
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### Input Filter for Current Sense Amplifier - ODrive

Out of curiosity, can anyone explain to me why the input filters for the current sense amplifiers in the old ODrive schematics are unbalanced (i.e., the external resistor is only on the negative CSA ...
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1 vote
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### Incorrect cutoff frequency using two Sallen-Key filters to build a bandstop filter

I'm currently having trouble troubleshooting my answer. I have to make a bandstop filter that has a cutoff frequency of 100 rad/s, and 10^6 rad/s using two Sallen-Key filters. I made the low and high ...
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1 vote
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### Switch Mode Power Supply / GPS - Filtering+Shielding

I'm working on my first RF PCB, for GPS/ GNSS and am particularly concerned about Noise/ Interference. Hopefully someone can shed some light, or point me toward a similar thread? It's worth noting ...
1 vote
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### Interdigital filter ground connection on PCB

I have used an online designer utility for my 5 GHz to 6 GHz RF output filter, on the schematic it generated it had shown ground attach points, but I am not sure if I designed ground connections and ...
1 vote