Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

while designing the filter(low pass filter)

Status
Not open for further replies.
2

24+

Junior Member level 2
Joined
Feb 18, 2010
Messages
20
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
India
Activity points
1,422
while designing the filter(low pass filter) , which one is better means active filter(using opamps) or passive filter (only r and c ). which filter is better and accurate for filtering with out noise...
 

24+ said:
while designing the filter(low pass filter) , which one is better means active filter(using opamps) or passive filter (only r and c ). which filter is better and accurate for filtering with out noise...
Click to expand...

The answer depends on the requirements to the filter:
filter order (damping requirements), bandwidth (corner frequency), gain yes/no, tuning capabilities yes/no, .....

Please, be more specific.
 

The answer depends on the requirements to the filter:
filter order (damping requirements), bandwidth (corner frequency), gain yes/no, tuning capabilities yes/no, .....

Please, be more specific.[/quote]

i want the envelope of the 40khz signal which is transmitted from tx. before transmitting, i have given that to low pass filter so that can have its envelope.see the attachment..
 

I like passive filters but use more active filters. The reason is that passive filters can prove expensive or require "impossible" components. For your application I would use an active filter.

However, a low pass filter will not give you the signal you show - what you need is a peak detect circuit or AM demodulator, if I understand your requirements correctly. In its simplest form, that can just be a diode, capacitor and resistor. You will still want some filtering before that (40kHz bandpass I would have thought) but then you will still have a 40kHz signal, not the square wave you draw. The AM demodulator will produce the square wave, although with some well rounded corners.

Keith.
 

Mr. Keith,
I am agree with your solution but got a curiosity. Is there some other way to do Amplitude modulation than using filters?
As for this problem, I think active filter would be an better option as passive filter may reduce the signal level and information could be lost.

Regards,
Umesh
 

Umesh,

Search the internet for amplitude modulation/demodulation. The is a synchronous technique where the incoming signal is multiplied by the received signal but I have never used it.
It would still involve filtering though.

Keith
 

Thanks Keith,
I got some. it is interesting to see the use of SPDT to multiply the signals.

Umesh
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top