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Simulators >> System Simulators >> Bandpass sampling
https://designers-guide.org/forum/YaBB.pl?num=1238705966

Message started by Mahyar on Apr 2^nd, 2009, 1:59pm

Title: Bandpass sampling
Post by Mahyar on Apr 2^nd, 2009, 1:59pm

Hi guys,

For my master thesis I need to model and design a uniform quadrature bandpass sampling (UQBS) circuit. Do you have any good reference. specially for modeling the system in MATLAB and implementation.

regards,
M

Title: Re: Bandpass sampling
Post by pancho_hideboo on Apr 11^th, 2009, 3:50am

Mahyar wrote on Apr 2^nd, 2009, 1:59pm:

For my master thesis I need to model and design a uniform quadrature bandpass sampling (UQBS) circuit.
Do you have any good reference. specially for modeling the system in MATLAB and implementation.

What is UQBS ?
What is different from conventional qudrature bandpass sampling ?
Uniform sampling is common although theoretically non-uniform sampling is possible.

Your sampling is nyquist-sampling(over sampling) or under-sampling of bandpass signal ?

Title: Re: Bandpass sampling
Post by Mahyar on Apr 11^th, 2009, 5:03am

UQBPS is the uniform quadrature bandpass sampling which is the same as conventional quadrature bandpass sampling but since it is uniform it is easier to be realized as the implementation point of view. For sure it is an under sampling system since it wants to be a solution for software defined radio and the aim is to relax the requirements on ADC e.g high sampling rate.

At the moment I have two basic questions to ask:

1- How to express and show a single sideband bandpass signal in MATLAB.

2- I have the transfer function of a complex FIR filter and the coefficients but I don't know how to express it in MATLAB and see its response to my single sideband signal.

Thanks,
Mahyar

Title: Re: Bandpass sampling
Post by pancho_hideboo on Apr 11^th, 2009, 5:21am

MATLAB are different from Simulink.
Do you intend to mean MATLAB not Simulink ?

The followings are general notes.

- Use correct terminologies.
- Warnigns are different from Errors.
- ADS is not name of simulator.
- There is no tool which name is Cadence.
- All gains in Direct Plot of Cadence ADE are "right", "true" and "practical" voltage gain.
- MATLAB are different from Simulink.

- Learn measurements using actual instruments. Not "EDA Tool Play".

Mahyar wrote on Apr 11^th, 2009, 5:03am:

1- How to express and show a single sideband bandpass signal in MATLAB.
2- I have the transfer function of a complex FIR filter and the coefficients but I don't know how to express it in MATLAB and see its response to my single sideband signal.

Which of model in the followings do you use ?
(1)Real RF Signal, (I(t)+j*Q(t))*exp(j*omega0*t)
(2)Equivalent Lowpass Representation of RF Signal, {I(t)+j*Q(t), omega0}

http://www.designers-guide.org/Forum/YaBB.pl?num=1233929450/1#1

In your case, you have to use (1).

Attached figure is a conventional quadrature bandpass signal sampling using a single sampler.
Here you can't get I and Q at same time. Time difference of Ts always exists.

See the followings.
http://en.wikipedia.org/wiki/Digital_down_converter
page.14-16 of http://cp.literature.agilent.com/litweb/pdf/5989-9003EN.pdf
http://www.mathworks.com/applications/dsp_comm/demos.html?file=/products/demos/shipping/filterdesign/ddcfilterchaindemo.html#1
http://www.altera.com/support/examples/dsp-builder/exm-digital-down-conv-cic-fir.html

Which do you use single or dual sampler ?

What effects do you want to focus on in modeling quadrature sampler using Simulink ?
Multiple folding noise ?
Effect of Sampling Jitter in under-sampling system ?
If you only have interest on complex FIR, you don't have to model quadrature sampling at all.
Just create analytic signal representation of real signal.

Also see http://www.designers-guide.org/Forum/YaBB.pl?num=1207225157