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Entry  Mon Mar 5 20:31:33 2012, Koji, Update, LSC, 22/110MHz path for POP 
    Reply  Tue Mar 6 22:23:04 2012, Koji, Update, LSC, 22/110MHz path for POP 
       Reply  Wed Mar 7 15:56:36 2012, Koji, Update, LSC, 22/110MHz path for POP RFseparator.pngimpedance.pdftransmission.pdf
          Reply  Wed Feb 27 20:50:41 2013, Manasa, Update, LSC, 22/110MHz path for POP POP.png
             Reply  Tue Apr 2 23:14:02 2013, rana, Update, LSC, 22/110MHz path for POP 
Message ID: 6374     Entry time: Wed Mar 7 15:56:36 2012     In reply to: 6366     Reply to this: 8192
Author: Koji 
Type: Update 
Category: LSC 
Subject: 22/110MHz path for POP 

The RF separator installed comprises of the Minicircuits filters cascaded as in the figure below.
This has one input and 4 output ports for 11, 22, 30-60, and 110MHz signal.
As seen in this entry #6167, we have 22 and 110MHz signals together with 11, 44, 66MHz signals.
They may be demodulated via a harmonic characteristic of the mixers. (Remeber mixers are not multipliers.)


 Of course the big concern is the impedance matching for those signals as usual.
The 2nd attachment shows measured impedance of the circuits with all of the ports terminated.
From the complex impedance, we can calculate the reflection coefficient. The 44 and 110MHz
components look correctly matched while the others seems largely reflected.
This certainly is not a nice situation, as the reflection can make the amplifier next to the PD unhappy
(although the reflected power is tiny in our case).

In our case more eminent problem is that the amplitude of the 22MHz signal can vary depending on the cable length by
factor of 10 in amplitude. (c.f. VSWR on the 2nd attachment.)

The transmission to each port was measured. The separation of the signals looks good. But the attenuation of the
targetted signals (i.e. insertion losses) are qulitatively consistent with the impedance. Again these losses are depend
on the cable length.



Attachment 2: impedance.pdf  63 kB  | Hide | Hide all
Attachment 3: transmission.pdf  54 kB  | Hide | Hide all
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