SouthPark
Newbie level 6
Microwave Office 2010 - FM discriminator (demodulator) question
Hi folks! I'm just observing FM demodulation using Microwave Office (2009/2010 version), and I'm just trying to observe how well a very typical FM system really is against added noise.
I've got this simple setup (microwave office .emp file) attached, and I'm actually getting some results. But I've also got a couple of simple questions for any Microwave Office users with similar area of interest.
In my system, I use the FM_discriminator (FM_DSCRM from the MWO library) as the demodulator device. And I use a noise source to add noise to my FM signal (in order to study what will happen when the noisy FM signal eventually goes through this demodulator).
When I observe the bare output of the FM discriminator block (ie output of the FM_DSCRM block), I see a very noisy demodulated time-domain signal. This is when I'm using 0 dBm noise power for my noise source. So I decided to add a low-pass filter to the output of the FM_discriminator (ie the demodulator block). And I find that the output of the filter is quite a clean waveform (the recovered signal is 10 kHz, which matches the 10 kHz baseband/message signal).
I would really love to know whether or not the filter that I added is actually needed, or is the very noisy signal directly at the ouput of the FM_discriminator due to something that I've done wrong with my setup? I was thinking that if my filter is not supposed to be added, then the noisy output of the FM_DSCRM block doesn't really allow me to see any noise suppression quality of an FM system.
For this simple FM demodulator project - I'm only attempting to observe the ability of an FM system to deal with (suppress) noise. Can anybody tell me if I'm doing the 'wrong' thing by adding that extraneous filter after the FM_discriminator module? I see that when this filter is included, then I get a clean demodulated signal. But without that filter, I get a really noisy signal. Any nice recommendations?
Thanks very much in advance for any help!!
Hi folks! I'm just observing FM demodulation using Microwave Office (2009/2010 version), and I'm just trying to observe how well a very typical FM system really is against added noise.
I've got this simple setup (microwave office .emp file) attached, and I'm actually getting some results. But I've also got a couple of simple questions for any Microwave Office users with similar area of interest.
In my system, I use the FM_discriminator (FM_DSCRM from the MWO library) as the demodulator device. And I use a noise source to add noise to my FM signal (in order to study what will happen when the noisy FM signal eventually goes through this demodulator).
When I observe the bare output of the FM discriminator block (ie output of the FM_DSCRM block), I see a very noisy demodulated time-domain signal. This is when I'm using 0 dBm noise power for my noise source. So I decided to add a low-pass filter to the output of the FM_discriminator (ie the demodulator block). And I find that the output of the filter is quite a clean waveform (the recovered signal is 10 kHz, which matches the 10 kHz baseband/message signal).
I would really love to know whether or not the filter that I added is actually needed, or is the very noisy signal directly at the ouput of the FM_discriminator due to something that I've done wrong with my setup? I was thinking that if my filter is not supposed to be added, then the noisy output of the FM_DSCRM block doesn't really allow me to see any noise suppression quality of an FM system.
For this simple FM demodulator project - I'm only attempting to observe the ability of an FM system to deal with (suppress) noise. Can anybody tell me if I'm doing the 'wrong' thing by adding that extraneous filter after the FM_discriminator module? I see that when this filter is included, then I get a clean demodulated signal. But without that filter, I get a really noisy signal. Any nice recommendations?
Thanks very much in advance for any help!!
Attachments
Last edited: