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 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 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><u></u><u></u>
<u></u><u></u></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>