Hi! Dear Miguel,
In continuation with my earlier inputs, here are few more inputs/comments/discussions around potential automated "Impedance measurement system' which can measure for 100KHz-20/30MHz sweep.
I'm attaching here:
1.complete measurements done by impedance analyser on DUT/Load/network. This excel file has 3 sheets in it containing details measured for low sample, medium sample, and high sample over freq range, 100KHz-10MHz due to instrument limitations. I have tried to separate swing of 'Z', 'theta', 'C', 'D', and 'G' and is given in third sheet. (check excel attachment). So this time I'm providing you exact load variations as desired by you in most recent post of yours. attachment 1
2. I'm attaching research article showing system structure, Fig.5. using I-V method of impedance measurement. This scheme according to article works satisfactorily for 100KHz-20MHz (refer Fig.1. Impedance measurement methods characterization). attachment 2
Query:
Referring attachment 2, system structure for I-V method of impedance measurement, can you comment on use of DDS's (9834's) capability of supplying required excitation signal. I guess for a 6K-46M ohms impedance swing, 15-20 nAmp current should serve the purpose considering 3mA @0.8 V compliance limits of AD9834's output. Can you comment if DDS will act as a perfect excitation source say, constant current source by attenuating its o/p current to comply with 0.8V o/p limit before applying it to load. This will avoid use of dedicated constant current source circuit.
As can be seen from Fig.5. of attachment 2, DDS is used followed by LPF and attenuator.
The reference signal to ad8302 then will be picked from point 'Ug' (Fig.5., attachment2) with attenuator inserted in the path to match ad8302 i/p levels.
The response signal/across load as shown will be also used after attenuating to match ad8302 i/p levels..
The above two signals, reference and response signals will be fed to ad8302 i/ps.
The o/p of ad8302, VMAG and VPHS will be sampled by two channel, 10 bit simultaneous ADC for digitization.
I would imagine the VMAG o/p to be equivalent of 'Z'-magnitude and VPHS as a theta. That means I'm obtaining. polar form of complex impedance measured for the load/network/DUT under measurement right??
Above is my plan of implementation. Can you thoroughly guide considering new inputs and exact values of impedance, theta, cap, dissipation, conductance variations for the practical implementation using ad9834, ad8302,LPF, buffers, ATTENUATORS, ADC's components.
Looking forward to your thorough and detailed guidance.
Thanks and sincere regards,
Sorry, attachment 2 can't be sent as a attached files. Please find weblink instead: http://vddb.library.lt/fedora/get/LT-eLABa-0001:J.04~2007~ISSN_1392-1215.N_4_76.PG_59-62/DS.002.1.01.ARTIC
Dr.Babankumar