On Apr 25, 10:07�pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> John wrote:
> > On Apr 25, 8:28 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
> >>I was trying to design a bandlimited pseudorandom signal with constant
> >>envelope for radar/sonar and like applications. I.e. frequency
> >>modulation with smoothed transitions. The problem is closely related to
> >>CPM for data transmission, however the optimization criteria are not
> >>quite the same. In particular, it turns out that optimal value for
> >>normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
> >>Another observation: the binary CPM signal with BT ~ 0.3 and �h ~ 0.8
> >>makes for the best possible (?) rectangular spectrum shape, however its
> >>autocorrelation properties are worse then optimal.
> > BTW, I came to the conclusion on a prior project that CPM cannot have
> > impulse-like autocorrelation.
>
> Can you clarify?
> I am getting the main autocorrelation lobe just like it supposed to be
> according to the bandwidth, however there is a second lobe at ~ -7dB, a
> third at -20..-30 dB and so on till it gets to the autocorrelation floor.
>
> > For my project I switched to SQPSK with
> > a PN sequence (different on I and Q) and accepted suboptimal peak/avg
> > ratio in exchange for ideal autocorrelation.
>
> I thought about it. With or without offset, filtered QPSK has near
> gaussian amplitude distribution. It is not very obvious if better
> autocorrelation will compensate for PAPR.
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
>
>
>
> > John
>
> > John
If you can live with the spectrum of class C amp driven with a non-
constant env signal such as square-pulse offset QPSK, then I would
think the autocorrelation and tx efficiency will be quite good. If the
spectrum is unacceptable then you can either back off the transmit
power (very costly), reduce the symbol rate (longer transmit time), or
change the waveform to something with autocorrelation sidelobes such
as CPM. It would take some experimentation or a good simulation to
figure out which is better from an end-to-end link budget standpoint.
John
John
Reply by cfelton●April 27, 20102010-04-27
>
>Could you suggest a good reading on this matter?
>
On Apr 25, 8:28�pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> I was trying to design a bandlimited pseudorandom signal with constant
> envelope for radar/sonar and like applications. I.e. frequency
> modulation with smoothed transitions. The problem is closely related to
> CPM for data transmission, however the optimization criteria are not
> quite the same. In particular, it turns out that optimal value for
> normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
> Another observation: the binary CPM signal with BT ~ 0.3 and �h ~ 0.8
> makes for the best possible (?) rectangular spectrum shape, however its
> autocorrelation properties are worse then optimal.
>
> Could you suggest a good reading on this matter?
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
Reply by Vladimir Vassilevsky●April 26, 20102010-04-26
Steve Pope wrote:
> Vladimir Vassilevsky <nospam@nowhere.com> wrote:
>
>
>>I was trying to design a bandlimited pseudorandom signal with constant
>>envelope for radar/sonar and like applications. I.e. frequency
>>modulation with smoothed transitions. The problem is closely related to
>>CPM for data transmission, however the optimization criteria are not
>>quite the same. In particular, it turns out that optimal value for
>>normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
>>Another observation: the binary CPM signal with BT ~ 0.3 and h ~ 0.8
>>makes for the best possible (?) rectangular spectrum shape, however its
>>autocorrelation properties are worse then optimal.
>>
>>Could you suggest a good reading on this matter?
>
>
> I have no idea as to literature, but I likewise have had
> trouble sometimes receiving an h = 0.5 signal as well as
> I would like or would have expected, and had to push to
> a higher value of h.
>
> I assume it's simply because I don't know the best algorithms
> for what I'm trying to do.
For partial response CPM, the value of h somewhat higher then 0.5 makes
for lower autocorrelation floor. The difference could be ~1..2dB. The
intuitive explanation is if you choose h higher then 0.5, then the
"average" signal is going to be closer to h=0.5 .
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
Reply by Vladimir Vassilevsky●April 25, 20102010-04-25
John wrote:
> On Apr 25, 8:28 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
>
>>I was trying to design a bandlimited pseudorandom signal with constant
>>envelope for radar/sonar and like applications. I.e. frequency
>>modulation with smoothed transitions. The problem is closely related to
>>CPM for data transmission, however the optimization criteria are not
>>quite the same. In particular, it turns out that optimal value for
>>normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
>>Another observation: the binary CPM signal with BT ~ 0.3 and h ~ 0.8
>>makes for the best possible (?) rectangular spectrum shape, however its
>>autocorrelation properties are worse then optimal.
> BTW, I came to the conclusion on a prior project that CPM cannot have
> impulse-like autocorrelation.
Can you clarify?
I am getting the main autocorrelation lobe just like it supposed to be
according to the bandwidth, however there is a second lobe at ~ -7dB, a
third at -20..-30 dB and so on till it gets to the autocorrelation floor.
> For my project I switched to SQPSK with
> a PN sequence (different on I and Q) and accepted suboptimal peak/avg
> ratio in exchange for ideal autocorrelation.
I thought about it. With or without offset, filtered QPSK has near
gaussian amplitude distribution. It is not very obvious if better
autocorrelation will compensate for PAPR.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
>
> John
>
> John
Reply by Steve Pope●April 25, 20102010-04-25
Vladimir Vassilevsky <nospam@nowhere.com> wrote:
>I was trying to design a bandlimited pseudorandom signal with constant
>envelope for radar/sonar and like applications. I.e. frequency
>modulation with smoothed transitions. The problem is closely related to
>CPM for data transmission, however the optimization criteria are not
>quite the same. In particular, it turns out that optimal value for
>normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
>Another observation: the binary CPM signal with BT ~ 0.3 and h ~ 0.8
>makes for the best possible (?) rectangular spectrum shape, however its
>autocorrelation properties are worse then optimal.
>
>Could you suggest a good reading on this matter?
I have no idea as to literature, but I likewise have had
trouble sometimes receiving an h = 0.5 signal as well as
I would like or would have expected, and had to push to
a higher value of h.
I assume it's simply because I don't know the best algorithms
for what I'm trying to do.
Steve
Reply by John●April 25, 20102010-04-25
On Apr 25, 8:28�pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> I was trying to design a bandlimited pseudorandom signal with constant
> envelope for radar/sonar and like applications. I.e. frequency
> modulation with smoothed transitions. The problem is closely related to
> CPM for data transmission, however the optimization criteria are not
> quite the same. In particular, it turns out that optimal value for
> normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
> Another observation: the binary CPM signal with BT ~ 0.3 and �h ~ 0.8
> makes for the best possible (?) rectangular spectrum shape, however its
> autocorrelation properties are worse then optimal.
>
> Could you suggest a good reading on this matter?
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
BTW, I came to the conclusion on a prior project that CPM cannot have
impulse-like autocorrelation. For my project I switched to SQPSK with
a PN sequence (different on I and Q) and accepted suboptimal peak/avg
ratio in exchange for ideal autocorrelation.
John
John
Reply by John●April 25, 20102010-04-25
On Apr 25, 8:28�pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote:
> I was trying to design a bandlimited pseudorandom signal with constant
> envelope for radar/sonar and like applications. I.e. frequency
> modulation with smoothed transitions. The problem is closely related to
> CPM for data transmission, however the optimization criteria are not
> quite the same. In particular, it turns out that optimal value for
> normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
> Another observation: the binary CPM signal with BT ~ 0.3 and �h ~ 0.8
> makes for the best possible (?) rectangular spectrum shape, however its
> autocorrelation properties are worse then optimal.
>
> Could you suggest a good reading on this matter?
>
> Vladimir Vassilevsky
> DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
Reply by Vladimir Vassilevsky●April 25, 20102010-04-25
I was trying to design a bandlimited pseudorandom signal with constant
envelope for radar/sonar and like applications. I.e. frequency
modulation with smoothed transitions. The problem is closely related to
CPM for data transmission, however the optimization criteria are not
quite the same. In particular, it turns out that optimal value for
normalized deviation is higher then 0.5, optimal h ~0.6..0.7.
Another observation: the binary CPM signal with BT ~ 0.3 and h ~ 0.8
makes for the best possible (?) rectangular spectrum shape, however its
autocorrelation properties are worse then optimal.
Could you suggest a good reading on this matter?
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com