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Need some pointers on building UHF/microwave 50 ohm termination/power splitter
Hi all,
I need a couple of accessories to enable me to make some phase measurements with my HP network analyzer. I'd thought I could pick these up on ebay easily enough, but note the lack of availably with surprise and dismay. I need to therefore contrive two precision parts: Firstly, 50 ohm load that's essentially non-reactive up to 1.3Ghz. Power handling only need be a few tens of miliwatts. N-type connection. Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type connections, again flat up to 1.3Ghz. No switching needed, thankfully. If I can't source these parts elsewhere, how feasible is it to make them up and can anyone point me to any designs on the web that might fit the bill? I'm aware that the introduction of any stray reactances into the devices will render all subsequent measurements invalid so I need to get these parts right. At least 1.3Ghz capability should be achievable for a hobbyist with care. Thanks, P. -- "What is now proved was once only imagin'd" - William Blake |
Need some pointers on building UHF/microwave 50 ohm termination/power splitter
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Need some pointers on building UHF/microwave 50 ohm termination/power splitter
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Need some pointers on building UHF/microwave 50 ohm termination/powersplitter
http://www.minicircuits.com/
Have a range of splitters and loads. Paul Burridge wrote: Hi all, I need a couple of accessories to enable me to make some phase measurements with my HP network analyzer. I'd thought I could pick these up on ebay easily enough, but note the lack of availably with surprise and dismay. I need to therefore contrive two precision parts: Firstly, 50 ohm load that's essentially non-reactive up to 1.3Ghz. Power handling only need be a few tens of miliwatts. N-type connection. Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type connections, again flat up to 1.3Ghz. No switching needed, thankfully. If I can't source these parts elsewhere, how feasible is it to make them up and can anyone point me to any designs on the web that might fit the bill? I'm aware that the introduction of any stray reactances into the devices will render all subsequent measurements invalid so I need to get these parts right. At least 1.3Ghz capability should be achievable for a hobbyist with care. Thanks, P. -- Kind Regards David Huisman General Manager ----------------------------------------------------------------------- ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work (Telemetry, Control, Monitoring, Security, HVAC ...) A.C.N. 107 441 869 Website : http://www.orbitcoms.com PO Box 4474 Lakehaven NSW 2263, AUSTRALIA Phone: 61-2-4393-3627 Fax : 61-2-4393-3685 Mobile: 61-413-715-986 |
Need some pointers on building UHF/microwave 50 ohm termination/power splitter
Paul Burridge wrote:
Hi all, I need a couple of accessories to enable me to make some phase measurements with my HP network analyzer. I'd thought I could pick these up on ebay easily enough, but note the lack of availably with surprise and dismay. I need to therefore contrive two precision parts: Firstly, 50 ohm load that's essentially non-reactive up to 1.3Ghz. Power handling only need be a few tens of miliwatts. N-type connection. Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type connections, again flat up to 1.3Ghz. No switching needed, thankfully. If I can't source these parts elsewhere, how feasible is it to make them up and can anyone point me to any designs on the web that might fit the bill? I'm aware that the introduction of any stray reactances into the devices will render all subsequent measurements invalid so I need to get these parts right. At least 1.3Ghz capability should be achievable for a hobbyist with care. Thanks, P. You can make a pretty good 50 Ohm termination with a PCB-mounting SMA connector. Cut off the centre pin of the PCB-end of the connector leaving 0.5mm or less protruding (careful of your eyes, the pin can go shooting off pretty fast, it's hard metal), and then solder two 0.1% 100 Ohm 0603 resistors between the centre pin and the outer (ground) part of the connector. The resistors should be diametrically opposite. I made one with 1% resistors and got the following: s11 -30dB up to 6GHx and s11 -47dB up to 500MHz It helps to tweak how flat you lie the resistors on the teflon at the back of the connector, but without a working VNA you just have to accept what you get. If you want a termination with a N connector, then you could use a really good adapter with the SMA termination I mentioned above, or work out something similar with a N connector however I have never tried that since I mostly use SMA anyway. I think a very accurate / flat power divider would be fairly hard to make well unless you can get boards made with microwave substrates. If you can work out your measurement setup such that the flatness etc of the divider is not so important, then that would help. There's a guy in the UK selling a one input two output type power divider with N connectors and a 50 Ohm N termination on e-bay at the moment if that helps you. Chris |
Need some pointers on building UHF/microwave 50 ohm termination/power splitter
Chris Jones wrote: Paul Burridge wrote: Hi all, I need a couple of accessories to enable me to make some phase measurements with my HP network analyzer. I'd thought I could pick these up on ebay easily enough, but note the lack of availably with surprise and dismay. I need to therefore contrive two precision parts: Firstly, 50 ohm load that's essentially non-reactive up to 1.3Ghz. Power handling only need be a few tens of miliwatts. N-type connection. Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type connections, again flat up to 1.3Ghz. No switching needed, thankfully. If I can't source these parts elsewhere, how feasible is it to make them up and can anyone point me to any designs on the web that might fit the bill? I'm aware that the introduction of any stray reactances into the devices will render all subsequent measurements invalid so I need to get these parts right. At least 1.3Ghz capability should be achievable for a hobbyist with care. Thanks, P. You can make a pretty good 50 Ohm termination with a PCB-mounting SMA connector. Cut off the centre pin of the PCB-end of the connector leaving 0.5mm or less protruding (careful of your eyes, the pin can go shooting off pretty fast, it's hard metal), and then solder two 0.1% 100 Ohm 0603 resistors between the centre pin and the outer (ground) part of the connector. The resistors should be diametrically opposite. I made one with 1% resistors and got the following: s11 -30dB up to 6GHx and s11 -47dB up to 500MHz It helps to tweak how flat you lie the resistors on the teflon at the back of the connector, but without a working VNA you just have to accept what you get. If you want a termination with a N connector, then you could use a really good adapter with the SMA termination I mentioned above, or work out something similar with a N connector however I have never tried that since I mostly use SMA anyway. I think a very accurate / flat power divider would be fairly hard to make well unless you can get boards made with microwave substrates. If you can work out your measurement setup such that the flatness etc of the divider is not so important, then that would help. Two SMD 100R resistors in parallel is good; six 300R resistors spread symmetrically around the centre pin would be better (if you can fit them in). You can buy 50R terminating resistors on a circular alumina substrate with a hole in the middle, where the conducting pat runs from the (metalised) rim of the inner hole to the (metalised) circumference. Finding them isn't easy, but they do offer the theoretical minimum of inductance. You should be able make a pretty accurate and flat power divider in a metal box between two bulk-head-mounted coax sockets by stringing together 0603 or 0805 0.1% SMD resistors with bits of 22swg wire in a neat and symmetrical birds nest. A fiddly job, and you'd probably want to use continuous solder seams to seal the box when you were finished to avoid creating a slot antena or two. The 0.1% SMD resistors are available off the shelf from Farnell - IIRR you have buy them in multiples of five, but they aren't that expensive and if want to built a low-inductance symmetrical structure you need to put three or four resistors in parallel (six would be nicer, but you'd need to be a Jim Williams level artist with the soldering iron to keep it neat). -- Bill Sloman, Nijmegen |
Need some pointers on building UHF/microwave 50 ohm termination/power splitter
On Fri, 06 Jan 2006 22:58:52 +0100, Paul Burridge
k wrote: Hi all, I need a couple of accessories to enable me to make some phase measurements with my HP network analyzer. I'd thought I could pick these up on ebay easily enough, but note the lack of availably with surprise and dismay. I need to therefore contrive two precision parts: Firstly, 50 ohm load that's essentially non-reactive up to 1.3Ghz. Power handling only need be a few tens of miliwatts. N-type connection. http://cgi.ebay.com/HP-909A-50-Ohm-C...QQcmdZViewItem Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type connections, again flat up to 1.3Ghz. No switching needed, thankfully. I must ask, what is the purpose of this? |
Need some pointers on building UHF/microwave 50 ohm termination/power splitter
Chris Jones wrote in
: Paul Burridge wrote: Hi all, I need a couple of accessories to enable me to make some phase measurements with my HP network analyzer. I'd thought I could pick these up on ebay easily enough, but note the lack of availably with surprise and dismay. I need to therefore contrive two precision parts: Firstly, 50 ohm load that's essentially non-reactive up to 1.3Ghz. Power handling only need be a few tens of miliwatts. N-type connection. Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type connections, again flat up to 1.3Ghz. No switching needed, thankfully. If I can't source these parts elsewhere, how feasible is it to make them up and can anyone point me to any designs on the web that might fit the bill? I'm aware that the introduction of any stray reactances into the devices will render all subsequent measurements invalid so I need to get these parts right. At least 1.3Ghz capability should be achievable for a hobbyist with care. Thanks, P. You can make a pretty good 50 Ohm termination with a PCB-mounting SMA connector. Cut off the centre pin of the PCB-end of the connector leaving 0.5mm or less protruding (careful of your eyes, the pin can go shooting off pretty fast, it's hard metal), and then solder two 0.1% 100 Ohm 0603 resistors between the centre pin and the outer (ground) part of the connector. The resistors should be diametrically opposite. I made one with 1% resistors and got the following: s11 -30dB up to 6GHx and s11 -47dB up to 500MHz It helps to tweak how flat you lie the resistors on the teflon at the back of the connector, but without a working VNA you just have to accept what you get. If you want a termination with a N connector, then you could use a really good adapter with the SMA termination I mentioned above, or work out something similar with a N connector however I have never tried that since I mostly use SMA anyway. I think a very accurate / flat power divider would be fairly hard to make well unless you can get boards made with microwave substrates. If you can work out your measurement setup such that the flatness etc of the divider is not so important, then that would help. There's a guy in the UK selling a one input two output type power divider with N connectors and a 50 Ohm N termination on e-bay at the moment if that helps you. Chris A two-output splitter,IIRC,uses 3 25 ohm resistors in a Y config. Use a double-sided PCB for the ground plane between the three N connectors. -- Jim Yanik jyanik at kua.net |
Need some pointers on building UHF/microwave 50 ohm termination/power splitter
On Fri, 06 Jan 2006 19:40:27 -0700, Wes Stewart
wrote: http://cgi.ebay.com/HP-909A-50-Ohm-C...QQcmdZViewItem Thanks, Wes. I'll keep an eye on it. Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type connections, again flat up to 1.3Ghz. No switching needed, thankfully. I must ask, what is the purpose of this? The (thumping great) service manual that came with this VNA gives various levels of tests that can be performed oneself prior sending the thing away for calibration. The power splitter together with a few other basic items enables the analyzer to 'check itself' for fundamental operating fitness. I'm eager to get measurin' stuff, but need to establish some basic, satisfactory level of accuracy first. Being just a hobbyist, I don't require any absolute standard, thankfully!! -- "What is now proved was once only imagin'd" - William Blake |
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