Eric Jacobsen wrote:
> On Thu, 21 Feb 2008 02:35:33 -0800 (PST), Bob <[email protected]>
> wrote:
>
>> On 21 Feb, 08:14, c...@claysturner.com wrote:
>>> On Feb 20, 4:38 pm, Bob <sten...@yahoo.com> wrote:
>>>
>>>
>>>
>>>
>>>
>>>> On 20 Feb, 20:41, Mark <makol...@yahoo.com> wrote:
>>>>>> So now I see something,,,notice the small peak to the left of the
>>>>>> cursor on the second and fourth traces. Should this not be the same as
>>>>>> the peaks beside it?
>>>>> remember you are looking at the RRC filter..which is only 1/2 the
>>>>> picture
>>>>> pass this output though another RRC filter so that you have the full
>>>>> RC filter and you will see what the receiver sees...
>>>>> the Rx and Tx have matched filters and the NYquist filter is both of
>>>>> them in cascade,
>>>>> you are looking 1/2 way through the cascade..
>>>>> Mark
>>>> Hi Mark,
>>>> The pulses you see on the first link is what happens when I pass the
>>>> data through the RRC on the TX link. On the demod side links 2 and 3
>>>> are when the data from the modulator is passed through idential RRCs.
>>>> So, in effect I already have the RC response at the receiver. But is
>>>> it correct...that's what I would like to know?
>>>> Bob- Hide quoted text -
>>>> - Show quoted text -
>>> Hello Bob,
>>>
>>> The feeding of pulses into the RRC filter (via convolution) assumes
>>> your pulses become Kronecker deltas. Don't feed rectangular pulses,
>>> instead feed spikes into the RRC filter. Then after going through two
>>> of these in sucession, you will see a nice looking signal. You are
>>> currenly getting a bunch of ringing resulting from the rectangular
>>> pulse's response comingled (convolved) with the RRC's response. For
>>> simplifying the testing, just try an RC filter and look at its output.
>>> Two RRCs convolved is an RC. Try it!
>>>
>>> IHTH,
>>>
>>> Clay- Hide quoted text -
>>>
>>> - Show quoted text -
>> Hi Clay,
>>
>> I did already try it. I fed the output of one RRC into another and
>> you're correct...I did get a nice RC pulse output.
>> In the test case, this was done for spikes well seperated. However,
>> for real test data, I don't have much choice as I have strings of 1's
>> and in most cases very few 0's between them. In this case, what are my
>> options?
>>
>> Regards
>> Bob
>
> I haven't looked at your latest plots, but I'm a little confused by
> your last statement. How many samples per symbol are there going
> into the transmit RRC filter? If the answer is one, then you don't
> have to worry about the rectangular symbol problem. If the answer is
> more than one, then only one of those samples per symbol should be
> non-zero if you want to avoid an additional sinx/x response in the
> filtering.

That really cuts down on the compute too. Isn't it nice when the right
approach is actually the lowest compute one. :-)

Steve