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Continuous time sigma delta in simulink

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vrs007

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continuous time sigma delta

Hi all,
I am trying to implement a 3rd order CTSDM in simulink....I have implemented them in the discrete domain...but I donno how to do it in simulink for the CT domain...any help??
If anyone has a sample CTSDM simulink(.mdl) file...plz upload it here...
I know tht the sampling is done after the loop filter and before the quantizer but how to implement it??

Thanks,
Regards,
ravi
 

gevy

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simulink continuous-time

The SD toolbox is a toolbox created to simulate at behavioral level (within Simulink environment) Switched Capacitor (SC) Sigma-Delta modulators. All of the most important non-idealities are included, such as sampling jitter, kT/C noise, internal ADC/DAC parameters (mismatch and non-linearity) and operational amplifier parameters (white noise, 1/f noise, finite dc gain, finite bandwidth, slew rate and saturation voltages). Moreover, the SD toolbox provides blocks and scripts for postprocessing the simulation results in order to obtain power spectral densities, signal-to-noise ratio (SNR) and effective number of bits (ENOB).

http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=7589&objectType=file
 

vrs007

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continuous time sigma delta toolbox

Thx for the reply...but how is the sampling implemented for the CT modulator...do we have a clocked quantizer...clocked at sampling rate??
 

northeast1

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continuous-time sigma-delta

vrs007 said:
Hi all,
I am trying to implement a 3rd order CTSDM in simulink....I have implemented them in the discrete domain...but I donno how to do it in simulink for the CT domain...any help??
If anyone has a sample CTSDM simulink(.mdl) file...plz upload it here...
I know tht the sampling is done after the loop filter and before the quantizer but how to implement it??

Thanks,
Regards,
ravi

The SC realization is still a decrete method, no CT.
 

vrs007

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.mdl sigma delta

northeast1 said:
The SC realization is still a decrete method, no CT.
Yes,but I am not yet into the ckt level implementation...my doubt is...in a CT-SDM the sampling is dne after the loop filter unlike the DT-SDM where the input is sampled directly outside the loop itself...so how do we implement this sampling for CT...is there a "sampling" block in simulink or can I just use a quantizer or loop filter with a specified sampling period??
 

jowong1

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continuous-time sigma delta model

Hi, I dont have the SD Toolbox in my version of Matlab in school....is there any way to model continuous time DSM using regular transfer functions and gain and quantizer block? I am trying to model a bandpass DSM...i have done so in discrete time but cannot get it to work in continuous time....the PSD gives me a spike even when i am having no sinusoidal input.

Thanks
 

nijMcnij

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third oreder ct sigma delta

vrs007, use a zero order hold from the discrete library infront of your quantizer, and repalce the discrete integrators with ct integrators from the continuous time library.
 

    vrs007

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mkenobi

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omid shoaei continuous time sigma delta

CT sigma delta can be modeled as a discrete time system since S/H operation is done inside the feedback loop. I suggest you to take a glance at Omid Shoaei's PhD thesis. As far as I know there is no public release sigma-delta toolbox for continuous-time. You have to come up with your own model.
 

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