Home |
Search |
Today's Posts |
|
#1
|
|||
|
|||
"Hans Summers" wrote in message news:bmj291
Interesting ideas Len. I guess the idea of an all-digital spectrum analyser is similar to that of an all-digital HF amateur radio tranceiver. It can be done but at the current state of the art, it's a difficult proposal for the hobbyist and certainly difficult to obtain the same level of performance as the equivalent analogue device for the same amount of cost and/or effort. I have a PC-based oscilloscope that does something pretty close. It digitizes at the rate of 4ns per sample (taking 8bit samples unfortunately) and generates an FFT display of magnitude/power spectrum/power density). I think it is feasible to use an analogue RF front end under computer control, the a PC controlling the VCO and sampling the logarithmic output. In essence just replacing the oscilloscope as the display system. I guess, it is not necessary to PC control the VCO. Sweep generators are easy to come by. probably, if there is a way to feed the sweep into the PC to generate the X-axis, then that might be a better alternative. - farhan |
#2
|
|||
|
|||
I think it is feasible to use an analogue RF front end under computer control, the a PC controlling the VCO and sampling the logarithmic output. In essence just replacing the oscilloscope as the display system. I guess, it is not necessary to PC control the VCO. Sweep generators are easy to come by. probably, if there is a way to feed the sweep into the PC to generate the X-axis, then that might be a better alternative. Having the PC control the VCO via a digital-to-analogue converter gives the PC a lot of control over the sweep rate etc. You could then control the sweep rate, and zoom in on areas of your choice, via the PC rather than analogue controls. But either way would work fine. You can feed the sweep into the PC with a simple analogue-to-digital converter no problem. Hans |
#3
|
|||
|
|||
I think it is feasible to use an analogue RF front end under computer control, the a PC controlling the VCO and sampling the logarithmic output. In essence just replacing the oscilloscope as the display system. I guess, it is not necessary to PC control the VCO. Sweep generators are easy to come by. probably, if there is a way to feed the sweep into the PC to generate the X-axis, then that might be a better alternative. Having the PC control the VCO via a digital-to-analogue converter gives the PC a lot of control over the sweep rate etc. You could then control the sweep rate, and zoom in on areas of your choice, via the PC rather than analogue controls. But either way would work fine. You can feed the sweep into the PC with a simple analogue-to-digital converter no problem. Hans |
#4
|
|||
|
|||
This is a very interesting discussion
I have thought about doing this in the past, but have never been brave enough! What about a scheme like: Input - attenuator - LO/mixer-LPF/if amp -Direct coversionLO/Mixer - switchable LPF to say 150KHz - Log det (broadband)- ADC - software /PC For a 100MHz sweep you would probably need 300KHz bandwidth max which would be achieved by a 150KHz DSB receiver. You could go higher than 100MHz as the first IF - use ring diode mixer to a helical filter as the roofing filter I would be interested in a cooperative project Richard Ashhar Farhan wrote: "Hans Summers" wrote in message news:bmj291 Interesting ideas Len. I guess the idea of an all-digital spectrum analyser is similar to that of an all-digital HF amateur radio tranceiver. It can be done but at the current state of the art, it's a difficult proposal for the hobbyist and certainly difficult to obtain the same level of performance as the equivalent analogue device for the same amount of cost and/or effort. I have a PC-based oscilloscope that does something pretty close. It digitizes at the rate of 4ns per sample (taking 8bit samples unfortunately) and generates an FFT display of magnitude/power spectrum/power density). I think it is feasible to use an analogue RF front end under computer control, the a PC controlling the VCO and sampling the logarithmic output. In essence just replacing the oscilloscope as the display system. I guess, it is not necessary to PC control the VCO. Sweep generators are easy to come by. probably, if there is a way to feed the sweep into the PC to generate the X-axis, then that might be a better alternative. - farhan |
#5
|
|||
|
|||
This is a very interesting discussion
I have thought about doing this in the past, but have never been brave enough! What about a scheme like: Input - attenuator - LO/mixer-LPF/if amp -Direct coversionLO/Mixer - switchable LPF to say 150KHz - Log det (broadband)- ADC - software /PC For a 100MHz sweep you would probably need 300KHz bandwidth max which would be achieved by a 150KHz DSB receiver. You could go higher than 100MHz as the first IF - use ring diode mixer to a helical filter as the roofing filter I would be interested in a cooperative project Richard Ashhar Farhan wrote: "Hans Summers" wrote in message news:bmj291 Interesting ideas Len. I guess the idea of an all-digital spectrum analyser is similar to that of an all-digital HF amateur radio tranceiver. It can be done but at the current state of the art, it's a difficult proposal for the hobbyist and certainly difficult to obtain the same level of performance as the equivalent analogue device for the same amount of cost and/or effort. I have a PC-based oscilloscope that does something pretty close. It digitizes at the rate of 4ns per sample (taking 8bit samples unfortunately) and generates an FFT display of magnitude/power spectrum/power density). I think it is feasible to use an analogue RF front end under computer control, the a PC controlling the VCO and sampling the logarithmic output. In essence just replacing the oscilloscope as the display system. I guess, it is not necessary to PC control the VCO. Sweep generators are easy to come by. probably, if there is a way to feed the sweep into the PC to generate the X-axis, then that might be a better alternative. - farhan |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Spectrum Analyser CRT drive problem | Homebrew |