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Author Topic: Impedance Matching  (Read 2239 times)

Offline rdpzycho

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Impedance Matching
« on: August 28, 2008, 08:57:14 PM »
question sa mga RF engineers at mahilig sa RF.

'yung device kasi 50 ohms ang impedance tapos 75 ohms 'yung coax. kailangan ko ng wideband matching (halos DC to 1GHz ;D), resistive network 'yung una kong design (L-pad) dahil pinaka-simple (at pinakamura ;D). based sa mga texts, insertion loss nung resistive network 5.7dB lumalabas. kapag hindi ako nagmatch 0.177dB naman ang mismatch loss. is it really worth to match the impedances kahit na halos 1/4 na lang ang matitira sa akin sa resistive network o ok na 'yung mismatched at 0.177dB mismatch loss and VSWR of 1.5:1?

pwede ko pa rin namang i-consider ang LC matching, pero mukhang mababa naman na 'yung VSWR at mismatch loss. sa ngayon lalagyan ko lang muna ng provision para sa L-network kung sakali mang ima-match ko.
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Impedance Matching
« on: August 28, 2008, 08:57:14 PM »

Offline ef - el - ay - pee

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Re: Impedance Matching
« Reply #1 on: August 28, 2008, 11:21:38 PM »
mukhang maliit lang naman ang mismatch loss...pwede na po siguro
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Re: Impedance Matching
« Reply #1 on: August 28, 2008, 11:21:38 PM »

Offline rdpzycho

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Re: Impedance Matching
« Reply #2 on: August 28, 2008, 11:31:41 PM »
'yun din nga iniisip ko. hehehe.
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‎"Divide each difficulty into as many parts as is feasible and necessary to resolve it."
- Rene Descartes

"For every difficult problem there is always a simple answer and most of them are wrong."
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Re: Impedance Matching
« Reply #2 on: August 28, 2008, 11:31:41 PM »

Offline ef - el - ay - pee

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Re: Impedance Matching
« Reply #3 on: August 28, 2008, 11:34:19 PM »
kung di naman po kayo nasasayangan sa power ok na yun, di po ba maximum  power transfer lang naman ang purpose natin sa matching, di naman po siguro ganun kasignificant ang heat na maproproduce ng untransfered energy due to mismatch...
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Re: Impedance Matching
« Reply #3 on: August 28, 2008, 11:34:19 PM »

Offline rdpzycho

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Re: Impedance Matching
« Reply #4 on: August 28, 2008, 11:41:13 PM »
maliit lang 'yun. nasa -20dBm lang 'yung signal ko. ;D
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Re: Impedance Matching
« Reply #4 on: August 28, 2008, 11:41:13 PM »

Offline ef - el - ay - pee

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Re: Impedance Matching
« Reply #5 on: August 28, 2008, 11:44:44 PM »
pero di ko po kasi alam ang long term effects ng mismatch, pero since mababa lang...teka research muna ako...
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Offline rdpzycho

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Re: Impedance Matching
« Reply #6 on: August 28, 2008, 11:51:38 PM »
'yan din ang concern ko, puro theory at concepts lang kasi ang alam ko pagdating sa matataas na frequency, in practice wala akong alam kung ok na bang palagpasin 'yun. theoretically kasi mababa naman parehas ang mismatch loss at VSWR (sa ibang device pwedeng 4:1 ang VSWR at acceptable pa rin).

isa ko pang problema, walang Network Analyzer sa office. kapa kapa lang. ;D
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‎"Divide each difficulty into as many parts as is feasible and necessary to resolve it."
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Offline ef - el - ay - pee

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Re: Impedance Matching
« Reply #7 on: August 28, 2008, 11:59:41 PM »
pupugak pugak rin ang VNA dito, at di ko pa natry ang mismatch, well sana ma try ko to hahaha
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Offline paranz

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Re: Impedance Matching
« Reply #8 on: August 29, 2008, 12:01:45 AM »
OT: how much ba ang VNA ngayun? yung pinakamura..
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Offline ef - el - ay - pee

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Re: Impedance Matching
« Reply #9 on: August 29, 2008, 01:46:53 AM »
ewan, matagal nang nilalait ng electronix yung HP naming VNA,kelangan na daw palitan, kasi nagbebenta sila ng VNA na 2M ang isa...nagdemo sila sa amin as if naman kami ang may K bumili, strategy is that ma-amaze kami para mapilitan ang lab head namin na i-endorse sa Admin na bumili nito, o well...
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Offline gie62

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Re: Impedance Matching
« Reply #10 on: September 07, 2008, 07:33:16 PM »
sir, meron namang 50 ohms na coax, dapat ba talagang 75 ohms ang coax na gagamitin? 1.5:1 na vswr ok naman ito, pero mas maganda kung kaya pang ibaba. ang long term effect ng mataas ang vswr ay masisira ang rf amp. ng device. ano ba gamit ng device mo sir?
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Offline rdpzycho

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Re: Impedance Matching
« Reply #11 on: September 07, 2008, 09:27:40 PM »
75 ohm coax kasi 'yung panggagalingan ('yun ang ipro-provide nila, ayaw nilang magpalit sa 50 ohm coax).

50 ohm input nung LNA, medyo mababa naman input kapag mineasure, nasa -70 to -80 dBm siguro.
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Re: Impedance Matching
« Reply #12 on: September 07, 2008, 09:53:11 PM »

Okay naman ata yan na mismatch, kasi mas malaki yong coax imp kay sa device saka min lang ang VSWR, matanong ko lang RX at TX ba ang device mo?
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Offline rdpzycho

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Re: Impedance Matching
« Reply #13 on: September 07, 2008, 09:57:21 PM »
ang mangyayari, ipapasok 'yung device sa pagitan nung 75 ohm coax. wideband input kaya hindi ko magamitan ng reactive matching (medyo maraming passives kapag pinilit kong gamitan ng reactive match 'yung buong band), resistive lang ang simpleng design. tapos ilalabas ko ulit papunta sa 75 ohm coax. wala na akong problem sa output, medyo mas madali i-match.
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Offline zer0w1ng

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Re: Impedance Matching
« Reply #14 on: September 08, 2008, 08:53:23 AM »
A 1:1.5 wideband transformer will do.
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Offline gie62

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Re: Impedance Matching
« Reply #15 on: September 08, 2008, 10:30:05 AM »
sir sa CATV ba ang paggagamitan ng device? yung mini circuits device(MAR-X) mukhang sakto dyan sa project mo. sir kung nadadalian ka sa output matching, yun din ang gamitin mo sa input. reverse mo lang yung input output. kailangan mo talagang imatch yan kasi ang hina ng signal input mo, baka humina pa yan dahil sa mismatch..
 
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Offline rdpzycho

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Re: Impedance Matching
« Reply #16 on: September 09, 2008, 12:30:23 AM »
'yung output ko kasi narrowband na kaya madali ang matching. thanks.

meron akong amp din from mini circuits ERA-x. 'yun kasi 'yung medyo marami.

sa ngayon, wind muna ako ng transformer para sa experiments. ;D
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Re: Impedance Matching
« Reply #17 on: September 12, 2008, 12:55:06 PM »
Hello Sir,

Are you still a student?

Supplier ako ng RF test equipments maybe we could cater to your needs based on your budget

We have SPA na handheld and we also have VNA na 2 ports


www.rohde-schwarz.com


Key Facts
 


The tracking generator extends the R&S FSH3

Frequency range 100 kHz to 3 GHz
High level accuracy: 0.5 dB typ
Displayed average noise level typ. -114 dBm (RBW 1KHz)
Resolution bandwidths 1kHz to 1 MHz, 1 and 3 steps
Wide range of detectors : sample, max/min peak , auto peak, RMS
Tracking Generator from 5 MHz to 3 GHz



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Offline rdpzycho

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Re: Impedance Matching
« Reply #18 on: September 12, 2008, 08:48:08 PM »
nope. commercial project.
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‎"Divide each difficulty into as many parts as is feasible and necessary to resolve it."
- Rene Descartes

"For every difficult problem there is always a simple answer and most of them are wrong."
- Clayton Paul

Philippine Electronics Forum

Re: Impedance Matching
« Reply #18 on: September 12, 2008, 08:48:08 PM »
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