Phase rotation

On Oct 2, 1:10&#4294967295;pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
> >On Oct 2, 12:27=A0pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
> >> >On Oct 2, 11:31=3DA0am, "cpshah99" <cpsha...@rediffmail.com> wrote:
> >> >> >On Oct 2, 8:50=3D3DA0am, julius <juli...@gmail.com> wrote:
> >> >> >> On Oct 2, 8:38 am, John <sampson...@gmail.com> wrote:
>
> >> >> >> > For the simple case, just multiply your transmitted signal by
> >> >> exp(jwt)
> >> >> >> > where w is the Doppler offset frequency (rad/sec).
>
> >> >> >> > John
>
> >> >> >> That's correct for baseband. =3D3DA0For passband it's a bit more
> >> involve=3D
> >> >d,
> >> >> >> what
> >> >> >> is needed is a frequency shift of a real-valued signal.
> =3D3DA0It's
> >> >> >> sufficient to use
> >> >> >> a real-valued mixer and a filter to reject the extraneous images
> in
> >> >> >> the
> >> >> >> frequency domain.
>
> >> >> >> Julius
>
> >> >> >You are correct, but I think the OP specified phase rotation at
> >> >> >baseband anyway.
>
> >> >> >John
>
> >> >> %%%%
>
> >> >> Hello
>
> >> >> Thanks a lot John and Julius.
>
> >> >> I would like to read more about this topic. Can u please suggest
> any
> >> >> starting point.
>
> >> >> One day julius had said, synchronisation is really tough topic...i
> >> have
> >> >> realised that....so I am going step by step....first phase
> >> synchronisatio=3D
> >> >n
> >> >> and then time synchronisation.....
>
> >> >> and in the abover eqn exp(jwt), how i put value of 't', i knw it is
> >> silly
> >> >> que but please tell me.
>
> >> >> Thanks a lot.
>
> >> >> Regards,
>
> >> >> Chintan
>
> >> >t is a time vector. It goes from 0 to your last sample instant, with
> a
> >> >spacing of one over your sample rate.
>
> >> >For example, in Matlab you could do this:
>
> >> >Fs=3D3D1e6;
> >> >w=3D3D2*pi*1e3;
> >> >t=3D3D[0:Fs-1]/Fs;
> >> >osc=3D3Dexp(j*w*t);
>
> >> >John
>
> >> %%%%
>
> >> Hi John
>
> >> Thanks a lot.
>
> >> But I am just using one sample per symbol.
>
> >> so if my tx signal is 100 symbols then
>
> t=3D[0:length(msg-1)]./length(msg)
>
>
>
> >> is that correct?
>
> >Not quite. the -1 should be outside the parens (typo?). The
> >denominator should equal the sample rate ( same as symbol rate in your
> >case).
>
> >John
>
> %%%%
>
> Sorry for the typo. for my qpsk modulation, is this correct:
>
> msg=(sign(randn(1,100))+j*sign(randn(1,100)))/sqrt(2); % qpsk symbols
> t=[0:length(msg)-1]./100;
> op=msg.*exp(2*pi*1*t); % doppler of 1 Hz
>
> and how do I do for multipath channels, i.e. multipath and also all the
> path has got phase rotation.
>
> I can apply individual phase rotation and after adding proper delay, add
> them together.

Depends on your sampling rate.... and you're missing a 'j' like John
said.

>On Oct 2, 1:10=A0pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
>> >On Oct 2, 12:27=3DA0pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
>> >> >On Oct 2, 11:31=3D3DA0am, "cpshah99" <cpsha...@rediffmail.com>
wrote:
>> >> >> >On Oct 2, 8:50=3D3D3DA0am, julius <juli...@gmail.com> wrote:
>> >> >> >> On Oct 2, 8:38 am, John <sampson...@gmail.com> wrote:
>>
>> >> >> >> > For the simple case, just multiply your transmitted signal
by
>> >> >> exp(jwt)
>> >> >> >> > where w is the Doppler offset frequency (rad/sec).
>>
>> >> >> >> > John
>>
>> >> >> >> That's correct for baseband. =3D3D3DA0For passband it's a bit
mo=
>re
>> >> involve=3D3D
>> >> >d,
>> >> >> >> what
>> >> >> >> is needed is a frequency shift of a real-valued signal.
>> =3D3D3DA0It's
>> >> >> >> sufficient to use
>> >> >> >> a real-valued mixer and a filter to reject the extraneous
images
>> in
>> >> >> >> the
>> >> >> >> frequency domain.
>>
>> >> >> >> Julius
>>
>> >> >> >You are correct, but I think the OP specified phase rotation at
>> >> >> >baseband anyway.
>>
>> >> >> >John
>>
>> >> >> %%%%
>>
>> >> >> Hello
>>
>> >> >> Thanks a lot John and Julius.
>>
>> >> >> I would like to read more about this topic. Can u please suggest
>> any
>> >> >> starting point.
>>
>> >> >> One day julius had said, synchronisation is really tough
topic...i
>> >> have
>> >> >> realised that....so I am going step by step....first phase
>> >> synchronisatio=3D3D
>> >> >n
>> >> >> and then time synchronisation.....
>>
>> >> >> and in the abover eqn exp(jwt), how i put value of 't', i knw it
is
>> >> silly
>> >> >> que but please tell me.
>>
>> >> >> Thanks a lot.
>>
>> >> >> Regards,
>>
>> >> >> Chintan
>>
>> >> >t is a time vector. It goes from 0 to your last sample instant,
with
>> a
>> >> >spacing of one over your sample rate.
>>
>> >> >For example, in Matlab you could do this:
>>
>> >> >Fs=3D3D3D1e6;
>> >> >w=3D3D3D2*pi*1e3;
>> >> >t=3D3D3D[0:Fs-1]/Fs;
>> >> >osc=3D3D3Dexp(j*w*t);
>>
>> >> >John
>>
>> >> %%%%
>>
>> >> Hi John
>>
>> >> Thanks a lot.
>>
>> >> But I am just using one sample per symbol.
>>
>> >> so if my tx signal is 100 symbols then
>>
>> t=3D3D[0:length(msg-1)]./length(msg)
>>
>>
>>
>> >> is that correct?
>>
>> >Not quite. the -1 should be outside the parens (typo?). The
>> >denominator should equal the sample rate ( same as symbol rate in
your
>> >case).
>>
>> >John
>>
>> %%%%
>>
>> Sorry for the typo. for my qpsk modulation, is this correct:
>>
>> msg=3D(sign(randn(1,100))+j*sign(randn(1,100)))/sqrt(2); % qpsk
symbols
>> t=3D[0:length(msg)-1]./100;
>> op=3Dmsg.*exp(2*pi*1*t); % doppler of 1 Hz
>>
>> and how do I do for multipath channels, i.e. multipath and also all
the
>> path has got phase rotation.
>>
>> I can apply individual phase rotation and after adding proper delay,
add
>> them together.
>
>Depends on your sampling rate.... and you're missing a 'j' like John
>said.
>
%%%%%%

I am sorry...i missed that 'j'......

and if u can explain abt what depends on sampling rate?

thanks...

On Oct 2, 3:29&#4294967295;pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
> >On Oct 2, 1:10=A0pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
> >> >On Oct 2, 12:27=3DA0pm, "cpshah99" <cpsha...@rediffmail.com> wrote:
> >> >> >On Oct 2, 11:31=3D3DA0am, "cpshah99" <cpsha...@rediffmail.com>
> wrote:
> >> >> >> >On Oct 2, 8:50=3D3D3DA0am, julius <juli...@gmail.com> wrote:
> >> >> >> >> On Oct 2, 8:38 am, John <sampson...@gmail.com> wrote:
>
> >> >> >> >> > For the simple case, just multiply your transmitted signal
> by
> >> >> >> exp(jwt)
> >> >> >> >> > where w is the Doppler offset frequency (rad/sec).
>
> >> >> >> >> > John
>
> >> >> >> >> That's correct for baseband. =3D3D3DA0For passband it's a bit
> mo=
> >re
> >> >> involve=3D3D
> >> >> >d,
> >> >> >> >> what
> >> >> >> >> is needed is a frequency shift of a real-valued signal.
> >> =3D3D3DA0It's
> >> >> >> >> sufficient to use
> >> >> >> >> a real-valued mixer and a filter to reject the extraneous
> images
> >> in
> >> >> >> >> the
> >> >> >> >> frequency domain.
>
> >> >> >> >> Julius
>
> >> >> >> >You are correct, but I think the OP specified phase rotation at
> >> >> >> >baseband anyway.
>
> >> >> >> >John
>
> >> >> >> %%%%
>
> >> >> >> Hello
>
> >> >> >> Thanks a lot John and Julius.
>
> >> >> >> I would like to read more about this topic. Can u please suggest
> >> any
> >> >> >> starting point.
>
> >> >> >> One day julius had said, synchronisation is really tough
> topic...i
> >> >> have
> >> >> >> realised that....so I am going step by step....first phase
> >> >> synchronisatio=3D3D
> >> >> >n
> >> >> >> and then time synchronisation.....
>
> >> >> >> and in the abover eqn exp(jwt), how i put value of 't', i knw it
> is
> >> >> silly
> >> >> >> que but please tell me.
>
> >> >> >> Thanks a lot.
>
> >> >> >> Regards,
>
> >> >> >> Chintan
>
> >> >> >t is a time vector. It goes from 0 to your last sample instant,
> with
> >> a
> >> >> >spacing of one over your sample rate.
>
> >> >> >For example, in Matlab you could do this:
>
> >> >> >Fs=3D3D3D1e6;
> >> >> >w=3D3D3D2*pi*1e3;
> >> >> >t=3D3D3D[0:Fs-1]/Fs;
> >> >> >osc=3D3D3Dexp(j*w*t);
>
> >> >> >John
>
> >> >> %%%%
>
> >> >> Hi John
>
> >> >> Thanks a lot.
>
> >> >> But I am just using one sample per symbol.
>
> >> >> so if my tx signal is 100 symbols then
>
> >> t=3D3D[0:length(msg-1)]./length(msg)
>
> >> >> is that correct?
>
> >> >Not quite. the -1 should be outside the parens (typo?). The
> >> >denominator should equal the sample rate ( same as symbol rate in
> your
> >> >case).
>
> >> >John
>
> >> %%%%
>
> >> Sorry for the typo. for my qpsk modulation, is this correct:
>
> >> msg=3D(sign(randn(1,100))+j*sign(randn(1,100)))/sqrt(2); % qpsk
> symbols
> >> t=3D[0:length(msg)-1]./100;
> >> op=3Dmsg.*exp(2*pi*1*t); % doppler of 1 Hz
>
> >> and how do I do for multipath channels, i.e. multipath and also all
> the
> >> path has got phase rotation.
>
> >> I can apply individual phase rotation and after adding proper delay,
> add
> >> them together.
>
> >Depends on your sampling rate.... and you're missing a 'j' like John
> >said.
>
> %%%%%%
>
> I am sorry...i missed that 'j'......
>
> and if u can explain abt what depends on sampling rate?
>
> thanks...

Sigh. The phase increment of the complex oscillator depends on the
sample rate (Fs). For a one Hz Doppler, you want rotation of 2*pi
radians per second. Therefore the phase increment is 2*pi/Fs and the
phase vector is 2*pi*[0,1,2,...]/Fs.

John

>Sigh. The phase increment of the complex oscillator depends on the
>sample rate (Fs). For a one Hz Doppler, you want rotation of 2*pi
>radians per second. Therefore the phase increment is 2*pi/Fs and the
>phase vector is 2*pi*[0,1,2,...]/Fs.
>
>John
>
%%%

Hi John

Thanks a lot.

One last favour. Can u suggest me some good book on this or something
where i can read abt this?

On Oct 3, 5:53&#4294967295;am, "cpshah99" <cpsha...@rediffmail.com> wrote:
> >Sigh. The phase increment of the complex oscillator depends on the
> >sample rate (Fs). For a one Hz Doppler, you want rotation of 2*pi
> >radians per second. Therefore the phase increment is 2*pi/Fs and the
> >phase vector is 2*pi*[0,1,2,...]/Fs.
>
> >John
>
> %%%
>
> Hi John
>
> Thanks a lot.
>
> One last favour. Can u suggest me some good book on this or something
> where i can read abt this?

I don't know of a specific reference. Any introductory DSP book should
give you enough background to understand how to generate sines and
cosines.

John