Power line modem BELL 202

Thread Starter

mmuj

Joined Dec 15, 2009
11
Hi

I have just started working on a power line modem design using BELL 202 modulation (FSK 1200/2200 Hz marks space signal).

There are quite a few design examples available from different chip manufacturers, e.g. TI, ON Semi etc. but all of these use CENELEC bands (starting from 9kHz, different modulation like OFDM, PSK variants etc.) but my project requirement is to use only BELL 202 standard signaling (it is imposed by the customer).

There are few chips available for phone line and HART network BELL 202 modem but I can not find any for power line application. Using HART or phone line modem chip will have problem with power line noise and have no mechanism to deal with zero cross detection (used in power line modem to synchronize with 50/60Hz).

If anyone know about off the shelf chip to handle modulation for power line application or any idea to deal with the project basic requirement of FSK BELL 202 modulation.


Thanks in advance.

mmuj
 

Papabravo

Joined Feb 24, 2006
13,926
Power lines are pretty much guaranteed to make a really crappy transmission medium, and the way the power grid is constructed makes it really hard to transmit a signal over any appreciable distance. When BPL in the US fell apart for it's obvious disadvantages that pretty much ended the market for custom modem chips. I'm not saying they don't exist, but I've never seen one and can't imagine why anybody would want one, with ubiquitous broadband and wireless available over several different media types.
 
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Thread Starter

mmuj

Joined Dec 15, 2009
11
Thanks Papabravo

I am thinking of modifying AFE031 reference design for 600V by changing coupling transformer and capacitors etc. I haven't found anything which suggest that low frequency transmission could be a problem using AFE031. All the graphs are showing 10kHz upward but frequency response is a straight line on 10kHz which indicates that there is no build in high pass filter. Although external band pass filter need to adjusted.

I have been working on it and so far i can see that software modem (e.g. MSP430) + AFE031 + modified Mains coupling circuit will do it. Any suggestion?

Regards,

M Mujahid
 

Papabravo

Joined Feb 24, 2006
13,926
Thanks Papabravo

I am thinking of modifying AFE031 reference design for 600V by changing coupling transformer and capacitors etc. ....
Is this reference design you are referring to the same as Figure 49. in the datasheet?
Which method of connecting the transmitter chain are you considering?
 

Papabravo

Joined Feb 24, 2006
13,926
Yes, it is figure49.

I will do some maths and use custom made transformer for my design.
You misunderstood my question. The datasheet shows different way of connecting the transmitter chain. One of the ways uses a Digital to Analog Converter(DAC). Is that the method you are using?
 
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