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<div class="moz-cite-prefix">Hi Andrey,<br>
<br>
Plots are looking good. Just for your information, we reduced Ichp
to 400uA to reduce close to integer i.e. fractional spurs which
you may have not seen yet but they are there. These have noting to
do with GPS module on UmTRX board neither with LMS chip, it is
just PLL nature. Please be aware of this while comparing different
loop filters, especially different Ichp values, ...<br>
<br>
Best regards, Srdjan<br>
<br>
On 23/07/2012 19:44, Andrey Sviyazov wrote:<br>
</div>
<blockquote
cite="mid:CAE9ARExcvQ55a=8PiNnzmGdBvbDnGOn+_rAugXmmVkdsGDrWjg@mail.gmail.com"
type="cite">Hi Srdjan.
<div><br>
</div>
<div>
<div>Today I found why noises and spurs are really happens in
UmTRXv1.</div>
<div><br>
</div>
<div>1) Only full disabling (no power) GPS module can kill all
near spurs.</div>
<div>2) To get good noises the next changes are required:</div>
<div>- replace choke L6 by capacitor 10nF..0.1uF.</div>
<div>- remove C45.</div>
<div><br>
</div>
<div>I've assembled 100kHz loop filter with the next components:</div>
<div>C82 = 100pF, C83=1500pF, C84=33pF, R106=2.2k, R109=3.3k.</div>
<div><br>
</div>
<div>Result without GPS for IChP=0.4mA and due to several XO
attached here.</div>
<div>Also attached comparison of 50kHz/100kHz loop filters with
optimal IChp 1.2mA/0.4mA but with GPS module (no antenna).</div>
</div>
<div>So, now we need to measure integrated LO noise (degrees) to
understand which filter and IChP better.</div>
<div><br>
</div>
<div>Best regards,
<div>Andrey Sviyazov.</div>
<br>
<br>
<br>
<br>
<div class="gmail_quote">2012/7/23 Srdjan Milenkovic <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:s.milenkovic@limemicro.com" target="_blank">s.milenkovic@limemicro.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Hi Andrey,<br>
<br>
Below is the loop filter for 100kHz loop bandwidth,
26MHz reference clock, 400uA charge pump current. It has
been tested and should give you around -90dBc/Hz
plateau.<br>
<br>
<img moz-do-not-send="true" alt="" height="225"
width="423"><br>
<br>
<table style="border-collapse:collapse;width:434pt"
border="0" cellpadding="0" cellspacing="0" width="577">
<colgroup><col style="width:80pt" width="106"><col
style="width:83pt" width="110"><col
style="width:80pt" width="106"><col
style="width:90pt" width="120"><col
style="width:101pt" width="135"></colgroup><tbody>
<tr style="min-height:22.5pt" height="30">
<td style="min-height:22.5pt;width:80pt"
height="30" width="106">C1</td>
<td style="width:83pt" width="110">R2</td>
<td style="border-left:none;width:80pt"
width="106">C2</td>
<td style="border-left:none;width:90pt"
width="120">R3</td>
<td style="border-left:none;width:101pt"
width="135">C3</td>
</tr>
</tbody>
</table>
<table style="border-collapse:collapse;width:434pt"
border="0" cellpadding="0" cellspacing="0" width="577">
<colgroup><col style="width:80pt" width="106"><col
style="width:83pt" width="110"><col
style="width:80pt" width="106"><col
style="width:90pt" width="120"><col
style="width:101pt" width="135"></colgroup><tbody>
<tr style="min-height:22.5pt" height="30">
<td style="min-height:22.5pt;width:80pt"
height="30" width="106">9.01E-11</td>
<td style="width:83pt" width="110">2.46E+03</td>
<td style="border-left:none;width:80pt"
width="106">1.42E-09</td>
<td style="border-left:none;width:90pt"
width="120">3280.93</td>
<td style="border-left:none;width:101pt"
width="135">2.56E-11</td>
</tr>
</tbody>
</table>
<br>
<br>
Loop filter components for 10kHz bandwidth, 26MHz
reference clock, 400uA charge pump current are below:<br>
<br>
<table style="border-collapse:collapse;width:434pt"
border="0" cellpadding="0" cellspacing="0" width="577">
<colgroup><col style="width:80pt" width="106"><col
style="width:83pt" width="110"><col
style="width:80pt" width="106"><col
style="width:90pt" width="120"><col
style="width:101pt" width="135"></colgroup><tbody>
<tr style="min-height:22.5pt" height="30">
<td style="min-height:22.5pt;width:80pt"
height="30" width="106">C1</td>
<td style="width:83pt" width="110">R2</td>
<td style="border-left:none;width:80pt"
width="106">C2</td>
<td style="border-left:none;width:90pt"
width="120">R3</td>
<td style="border-left:none;width:101pt"
width="135">C3</td>
</tr>
</tbody>
</table>
<table style="border-collapse:collapse;width:434pt"
border="0" cellpadding="0" cellspacing="0" width="577">
<colgroup><col style="width:80pt" width="106"><col
style="width:83pt" width="110"><col
style="width:80pt" width="106"><col
style="width:90pt" width="120"><col
style="width:101pt" width="135"></colgroup><tbody>
<tr style="min-height:22.5pt" height="30">
<td style="min-height:22.5pt;width:80pt"
height="30" width="106">9.01E-09</td>
<td style="width:83pt" width="110">2.46E+02</td>
<td style="border-left:none;width:80pt"
width="106">1.42E-07</td>
<td style="border-left:none;width:90pt"
width="120">328.09</td>
<td style="border-left:none;width:101pt"
width="135">2.56E-09</td>
</tr>
</tbody>
</table>
<br>
There should not be any issue with loop stability even
with 10kHz filter. However, PLL settling time is
increased so you have to slow down VCOCAP auto-tune.<br>
<br>
I would recommend to use 100kHz filter.<br>
<br>
Regards, Srdjan
<div>
<div class="h5"><br>
<br>
<div> </div>
On 22/07/2012 20:53, Andrey Sviyazov wrote:<br>
</div>
</div>
</div>
<div>
<div class="h5">
<blockquote type="cite">Hi Srdjan.
<div><br>
First of all thank you for support.<br>
<br>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>We do not have register dump. However,
Lime GUI project file used in this
experiment is attached. You can use GUI
File->Open Project option to import it.
I see Ichp and Ichp offset currents are
different from defaults but these still do
not justify 5-12dB worse PN in your
reports. You can give it a try though
before changing TCXCO.<br>
</div>
</div>
</blockquote>
<div><br>
</div>
<div>We will try to adjust Ichp and offset first
off all. Thank you for hint.</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div><font color="#ff0000"><b>Test
Description:</b><br>
</font>
<ul>
<li><font color="#ff0000">DC MAX applied
through analogue inputs, DACs off</font></li>
</ul>
</div>
</div>
</blockquote>
<div>It is quite important detail too.</div>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>
<ul>
</ul>
<ul>
<li><font color="#ff0000">TXVGA1 and
TXVGA2 at max gain</font></li>
</ul>
</div>
</div>
</blockquote>
<div>Similar.</div>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>
<ul>
</ul>
<ul>
<li><font color="#ff0000">Loop filter
redesigned for 100kHz loop bandwidth
and 40MHz reference</font></li>
</ul>
</div>
</div>
</blockquote>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>
<ul>
<li><font color="#ff0000">Icp and Icp
offset optimized at 25 deg. Same set
up used at all other temperatures</font></li>
</ul>
</div>
</div>
</blockquote>
<div>Please inform us values of components for
100kHz BW filter.</div>
<div>But we are forced to use one clock 26MHz
for all because of target price.</div>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>
<ul>
</ul>
<ul>
<li><font color="#ff0000">Cap code and
VCO picked up by PLL tune routine</font></li>
</ul>
</div>
</div>
</blockquote>
<div>I implemented 10kHz BW filter for PLL and
found that frequency locking become unstable
because of calculated VCOCAP value a bit lower
then required (too high capacity).</div>
<div>If VCOCAP incremented manualy (after
auto-tuned) then no any problems.</div>
<div>What do you think about it.</div>
<div>And could you please inform me values for
10 kHz BW filter, just to compare with my
calculations.</div>
<div><br>
</div>
<div>Best regards,
<div>Andrey Sviyazov.</div>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
</div>
</blockquote>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</blockquote>
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