Reply by Vladimir Vassilevsky●January 26, 20042004-01-26
rider wrote:
>
> > >
> > > |PASS-BAND|--------------BASE-BAND----------------------|
> > >
> > > fs ------ fs ------ fs fb ------ fb -------
> > > r(nTs)--->|DEMOD|----| MF |---/---| EQUZ |---|SLICER |--->
> > > ------ ------ ^ --- |- ------- |
> > > ^ | | |
> > > | | `-----<---------`
> > > ------ ------
> > > | CR | | STR |
> > > ------ ------
> > >
> > >
>
> Hi Vladimir!
> Thanks for your reply. If I do use the above arrangement for my
> receiver, What kind of STR technique should i use? I have heard of
> various techniques, like Early/Late gate, Gardner etc.
I would use the simplest zero crossing STR for BPSK.
Here is a good book on CR/STR algorithms:
"Digital Communication Receivers : Synchronization, Channel Estimation"
Heinrich Meyr; Marc Moeneclaey; Stefan Fechtel
Vladimir Vassilevsky
DSP Consultant
http://www.abvolt.com
Hi Vladimir!
Thanks for your reply. If I do use the above arrangement for my
receiver, What kind of STR technique should i use? I have heard of
various techniques, like Early/Late gate, Gardner etc. As far as i
understood, Gardner algorithm requires STR in passband(i.e. it tries
to lock to fs not fb) and it requires 2 samples per symbol ( i have
fs=8fb) and some interpolator.
1)Is Gardner algortihm applicable in base-band as shown in my figure?
2)If i can use Gardner algorithm as above, the I already have fs=8fb,
so do i need to interpolate?
3)Where can i find a suitable resource for Gardner algorithm?
Regards
Rider
Thanks
Reply by Vladimir Vassilevsky●January 25, 20042004-01-25
rider wrote:
>
> Hi!
>
> For an all digital BPSK receiver, If I place the Equalizer in
> baseband,
There is no practical need in EQ for BPSK.
> then what could be its exactloaction: Is the following
> arrangement acceptable?
>
> |PASS-BAND|--------------BASE-BAND----------------------|
>
> fs ------ fs ------ fs fb ------ fb -------
> r(nTs)--->|DEMOD|----| MF |---/---| EQUZ |---|SLICER |--->
> ------ ------ ^ --- |- ------- |
> ^ | | |
> | | `-----<---------`
> ------ ------
> | CR | | STR |
> ------ ------
>
> Where:
> r(nTs)= Received pass-band Digital Samples at freq fs=1/Ts
> fs = Sampling Frequency
> fb = BPSK SYMBOL rate (bit rate) , fs >= 2.fb , fb=1/Tb , Tb=
> symbol/bit rate
> DMOD= Mix with recovered carrier and LPF, operating freq=fs
> CR= COSTAS LOOP CARRIER RECOVERY
> MF=Root Raised Cosine Filter, operating at fs
> STR= Symbol Timing recovery
> EQUZ= Symbol Spaced Equalizer, operating at fb
> SLICER= Hard decisions +/-1 V
Since your BPSK is RRC filtered prior to transmission, you should remove
RRC filter from the receiver or use square root filters both in receiver
and transmitter.
> 1) Is this arrangement acceptable as one possible form of a BPSK
> receiver?
Why not? This arrangement is as good as any other.
> 2) Since Equalizer is operating at Bit/Symbol rate fb, it is called a
> Symbol rate equalizer. What if I want to use a FSE (Fractionally
> Spaced Equalizer)? Say Tb/2 spaced(that Equalizer will give output at
> rate fb=1/Tb). Where should i place it? Before the MF ?
Anywhere. It does not matter.
> What would the
> position of STR in that case(The output of FSE would already have
> deimated to fb, so how to implement the STR)?
In this case if the EQ is N-spaced then the STR should recover
N*Bitrate.
> Do i have to move STR in
> pass-band?
You don't have to. That is just the matter of convenience.
Hi!
For an all digital BPSK receiver, If I place the Equalizer in
baseband, then what could be its exactloaction: Is the following
arrangement acceptable?
|PASS-BAND|--------------BASE-BAND----------------------|
fs ------ fs ------ fs fb ------ fb -------
r(nTs)--->|DEMOD|----| MF |---/---| EQUZ |---|SLICER |--->
------ ------ ^ --- |- ------- |
^ | | |
| | `-----<---------`
------ ------
| CR | | STR |
------ ------
Where:
r(nTs)= Received pass-band Digital Samples at freq fs=1/Ts
fs = Sampling Frequency
fb = BPSK SYMBOL rate (bit rate) , fs >= 2.fb , fb=1/Tb , Tb=
symbol/bit rate
DMOD= Mix with recovered carrier and LPF, operating freq=fs
CR= COSTAS LOOP CARRIER RECOVERY
MF=Root Raised Cosine Filter, operating at fs
STR= Symbol Timing recovery
EQUZ= Symbol Spaced Equalizer, operating at fb
SLICER= Hard decisions +/-1 V
1) Is this arrangement acceptable as one possible form of a BPSK
receiver?
2) Since Equalizer is operating at Bit/Symbol rate fb, it is called a
Symbol rate equalizer. What if I want to use a FSE (Fractionally
Spaced Equalizer)? Say Tb/2 spaced(that Equalizer will give output at
rate fb=1/Tb). Where should i place it? Before the MF ? What would the
position of STR in that case(The output of FSE would already have
deimated to fb, so how to implement the STR)? Do i have to move STR in
pass-band?
Regards
Rider