Comments for Circuit Design

Comment on Asymmetric chopping for improved IM3 | A dead-end research topic? by Poojan Wagh

Poojan Wagh — Fri, 19 Mar 2010 03:10:53 +0000

I finally got around to reading your paper, Kevin. Well done. Any way you can generalize it to something other than constant-amplitude tones?

Comment on The benefits of differential circuits by Arshad Iqbal

Arshad Iqbal — Tue, 23 Feb 2010 18:15:06 +0000

I completely agree with Mark’s statement. CMRR is the single most important criteria that makes the differential circuits stand out. If a circuit can correctly operate at lower SNR, single ended circuits would be fine. Differential circuits also impose upon layout to be symmetrical especially the difference sensing amplifiers and noise coupling or noise shielding structures.

Comment on Slope/Integrating ADC in Matlab Simulink by PoojanWagh

PoojanWagh — Tue, 16 Feb 2010 05:46:47 +0000

Hi, Krishna.

What you’ve stated isn’t fully specified. You say the input is 11.3 MHz, but what’s the output (or signal bandwidth)? What format is the input (PCM, floating point)?
When you say 16-bit, do you mean quantization noise, or aliasing, or both?
I can help you with a procedure, but I don’t have Simulink, so I can’t really give you an end solution.

Comment on Example Simulink model & scripts for continuous-time sigma-delta ADC by PoojanWagh

PoojanWagh — Tue, 16 Feb 2010 05:41:55 +0000

Hi, Daniyal. The ADC I have is a very specific type of ADC: a signma-delta ADC (and a continuous-time one at that). It is pretty complicated. If you’re building a controller, I’d suggest a Nyquist ADC. Sigma-Delta’s themselves include a feedback loop. Adding a feedback loop around the ADC amounts to having two interacting loops to stabilize. Not an easy task.

Anyway, I’ll attempt to answer your questions:
1. Mainly because it wasn’t germain to what I’m trying to model. You would need a decimation filter, but that’s done in the digital domain and is predictable and relatively easy to design.
2. Yes. This amounts to having a higher resolution and will only make things better. However, if you have a 12-bit quantizer to begin with, you might not need a sigma-delta (certainly not a continuous-time one).
3. This is difficult. The gains are sort of trial-and-error to keep the loop stabilized. There are some attempts to predict what they should be, but most people use them as starting points for their trial-and-error.
4. The output of the ADC shouldn’t have any additional delay. The integrators in the simulink model are there to form an error amplifier. The delays they introduce are taken into account when looking at loop stability. So, the integrators introduce some (ideal) delay that should be accounted for when designing your feedback loop.

I get the strong impression that what you want isn’t really a continuous-time sigma-delta, but rather some sort of PWM controller that involves an ADC. If you’re still interested, email poojanwagh at this domain and I’ll take a look at it.

Comment on Slope/Integrating ADC in Matlab Simulink by krishna kumar

krishna kumar — Thu, 28 Jan 2010 02:52:10 +0000

I am looking for matlab and simulink code for decimation filter.
The input to the decimation filter is bitstream 11.3Mhz and output should be 16bit at Nyquist rate. Please help me with the code. I have not designed it before.
Thanks,
K.K

Comment on Example Simulink model & scripts for continuous-time sigma-delta ADC by amitv singh tajput

amitv singh tajput — Thu, 07 Jan 2010 06:26:58 +0000

i m also working on that we can share our view

Comment on Example Simulink model & scripts for continuous-time sigma-delta ADC by Daniyal

Daniyal — Tue, 22 Dec 2009 16:59:26 +0000

I have some question if u’d be kind enough. I must say I am new to ADC’s, we have an ADC with our machine tools controller but we don’t know anything about it except for its sampling frequency and resolution (12-13) bits. So since we were modelling the whole controller so we needed to simulate an approximate model of the ADC as well. Anyways.
1- Why the your ADC does not have any filtering and decimation at the output ?
2- Can i replace your ’sign’ block with a 12 bit quantizer ?.
3- Wha about the Gain in the integrators block ? I mean can we actually compute them or just arbirary.
4- Our ADC does not have any delays at its output (since it will actually destroy the whole controller). So these simulink integrators, do they have substancial delays ?

Comment on Example Simulink model & scripts for continuous-time sigma-delta ADC by PoojanWagh

PoojanWagh — Sun, 20 Dec 2009 06:58:18 +0000

What specifically are you confused about? Do you have the simulink output (sampled digital words) in a matlab variable (vector)? If so, it should be pretty easy.

Comment on Example Simulink model & scripts for continuous-time sigma-delta ADC by krishna

krishna — Thu, 17 Dec 2009 12:50:38 +0000

hii there,
I am doing project on delta sigma ADC for gsm receiver …. i have developed a simulink model and now i should develop a code that runs the FFT for the model that i have develped i am a bit confused in developing the related code for the model that i have developed ..could u please help me in developing the FFT code for the model that i had build……..

Comment on The Binary Number System – Part 2: Binary Weighting by spencer

spencer — Thu, 10 Dec 2009 00:31:28 +0000

to pralie: i’m a child (i’m 12 years old) and i can use binary easily…then again i am a freakin genius…my iq is 146