A
Adam S
I had the following idea for a home built vector network analyzer project.
The block diagram is shown below. Essentially channels A and B are mixed
down to separate 1kHz IF and sampled with a stereo 24bit DACE for the
PC. Phase and magnitude of the resulting 1kHz signals are then
calculated with DSP methods.
f1-f0 = 1kHz as f0 sweeps from 0 to 20MHz.
I know there will be problems as f0 gets close to 1kHz and again at near
0Hz, due to SA602 not being an ideal mixer.
Anyone think concept won't work ?
To PC
*
|
-------
------ |FT245BM|
ch A ----- | | | |
o----|SA602|---| 2kHz |------. |USB I/O|
|mixer| | LPF | | -------
----- ------ | |
| LO | |
| ------ -------
o----. |24bit | | AVR |
| | | ADC |---| |
| | |stereo| | uC |
| | ------ -------
| | ------ | |
ch B ----- | | | | |
o----|SA602|-----| 2kHz |----' |
|mixer| | | LPF | |
----- | ------ |
| |
| |
| ------ ------ |
f1| | | |AD9834| |
'--| 20MHz|---| DDS |-----o
| LPF | | | |
------ ------ |
|
/| ------ ------ |
SIG / | f0| | |AD9834| |
OUT__/ |--------| 20MHz|----| DDS |----'
f0 \ | | LPF | | |
\ | ------ ------
\|
BUFFER
[view in monospaced characters]
The block diagram is shown below. Essentially channels A and B are mixed
down to separate 1kHz IF and sampled with a stereo 24bit DACE for the
PC. Phase and magnitude of the resulting 1kHz signals are then
calculated with DSP methods.
f1-f0 = 1kHz as f0 sweeps from 0 to 20MHz.
I know there will be problems as f0 gets close to 1kHz and again at near
0Hz, due to SA602 not being an ideal mixer.
Anyone think concept won't work ?
To PC
*
|
-------
------ |FT245BM|
ch A ----- | | | |
o----|SA602|---| 2kHz |------. |USB I/O|
|mixer| | LPF | | -------
----- ------ | |
| LO | |
| ------ -------
o----. |24bit | | AVR |
| | | ADC |---| |
| | |stereo| | uC |
| | ------ -------
| | ------ | |
ch B ----- | | | | |
o----|SA602|-----| 2kHz |----' |
|mixer| | | LPF | |
----- | ------ |
| |
| |
| ------ ------ |
f1| | | |AD9834| |
'--| 20MHz|---| DDS |-----o
| LPF | | | |
------ ------ |
|
/| ------ ------ |
SIG / | f0| | |AD9834| |
OUT__/ |--------| 20MHz|----| DDS |----'
f0 \ | | LPF | | |
\ | ------ ------
\|
BUFFER
[view in monospaced characters]