04-06-2019, 10:46 PM
Hi Frank, hi Jeffrey,
this looks like an interesting project! I just thought about the modulator and had this idea:
A - Generate a modulated vision signal in the IF frequency domain i.e. around 39-45MHz directly in the FPGA
B - Pass this through a vestigial sideband filter.
C - Generate a selectable frequency with the FPGA to be mixed with the VSB signal from step B. This would determine the output channel.
D - Generate a channel dependent DC output voltage. This would be used to control a tracking filter that is needed to filter out the mirror image frequency from step C leaving only the desired VSB signal.
As a VSB filter an SAW filter could be used. Even if this were a filter intended for a different TV System it would be possible to use it as long as the vision carrier in the IF domain was placed in a position to allow only 1.25MHz of the undesired Sideband to pass through.
Just an idea although this would involve some RF circuitry...
Cheers
Semir
this looks like an interesting project! I just thought about the modulator and had this idea:
A - Generate a modulated vision signal in the IF frequency domain i.e. around 39-45MHz directly in the FPGA
B - Pass this through a vestigial sideband filter.
C - Generate a selectable frequency with the FPGA to be mixed with the VSB signal from step B. This would determine the output channel.
D - Generate a channel dependent DC output voltage. This would be used to control a tracking filter that is needed to filter out the mirror image frequency from step C leaving only the desired VSB signal.
As a VSB filter an SAW filter could be used. Even if this were a filter intended for a different TV System it would be possible to use it as long as the vision carrier in the IF domain was placed in a position to allow only 1.25MHz of the undesired Sideband to pass through.
Just an idea although this would involve some RF circuitry...
Cheers
Semir
