Broadband coaxial power splitter


John Lemay
 

Curiosity got the better of me, and I ordered a broadband two way power
splitter on eBay. It's specified as being useable from 800 to 2500MHz, and
I've confirmed that it has a decent (but not brilliant) return loss over
that bandwidth.

The attached picture shows the power splitter de-constructed. The inner line
is stepped, each section being about 42mm long and the pin to pin length is
175mm. A quick and dirty measurement and calculation shows the impedance of
each section will be 48, 40, 32 and 28 ohms.

Can anyone give me a simple explanation of how this splitter works ?

Many thanks

John


Andy G4JNT
 

What's the return loss of one of the two output ports with the others terminated?
And the isolation between them?





On Fri, 11 Jun 2021 at 08:12, John Lemay <john@...> wrote:
Curiosity got the better of me, and I ordered a broadband two way power
splitter on eBay. It's specified as being useable from 800 to 2500MHz, and
I've confirmed that it has a decent (but not brilliant) return loss over
that bandwidth.

The attached picture shows the power splitter de-constructed. The inner line
is stepped, each section being about 42mm long and the pin to pin length is
175mm. A quick and dirty measurement and calculation shows the impedance of
each section will be 48, 40, 32 and 28 ohms.

Can anyone give me a simple explanation of how this splitter works ?

Many thanks

John







Andy G4JNT
 

Meant to continue, because it looks like a version of:

Each 50Ω output port transformed by a bit of tapered line (*)  to some intermediate value, then paralleled giving half the new impedance.  That parallel equivalent impedance then transformed to 50Ω via the main tapered (*) line

(*) Tapered line approximated by steps.    An infinitely long true taper would match over a wide bandwidth.   A finite taper over a narrower BW, limited by it's length.

Very hand wavy over-guess of how it works.



On Fri, 11 Jun 2021 at 08:18, Andy Talbot <andy.g4jnt@...> wrote:
What's the return loss of one of the two output ports with the others terminated?
And the isolation between them?





On Fri, 11 Jun 2021 at 08:12, John Lemay <john@...> wrote:
Curiosity got the better of me, and I ordered a broadband two way power
splitter on eBay. It's specified as being useable from 800 to 2500MHz, and
I've confirmed that it has a decent (but not brilliant) return loss over
that bandwidth.

The attached picture shows the power splitter de-constructed. The inner line
is stepped, each section being about 42mm long and the pin to pin length is
175mm. A quick and dirty measurement and calculation shows the impedance of
each section will be 48, 40, 32 and 28 ohms.

Can anyone give me a simple explanation of how this splitter works ?

Many thanks

John







KENT BRITAIN
 

Yes, I also have several of those and they really do have a good impedance match over a broad range of frequencies. One way to get your impedance transformation is with a tapered line.  A transmission line that slowly tapers from Impedance 1 to impedance 2.    It ends up being a lot longer than a quarter wave, but does work well.  
Easy to do on PCB stripline, but I have done it with coax grinding away part of the shield. 
You show this line tapering from 50 Ohm to 25 Ohms where the two 50 Ohm lines meet in parallel.   Kent

On Friday, June 11, 2021, 02:12:25 AM CDT, John Lemay <john@...> wrote:


Curiosity got the better of me, and I ordered a broadband two way power
splitter on eBay. It's specified as being useable from 800 to 2500MHz, and
I've confirmed that it has a decent (but not brilliant) return loss over
that bandwidth.

The attached picture shows the power splitter de-constructed. The inner line
is stepped, each section being about 42mm long and the pin to pin length is
175mm. A quick and dirty measurement and calculation shows the impedance of
each section will be 48, 40, 32 and 28 ohms.

Can anyone give me a simple explanation of how this splitter works ?

Many thanks

John







KENT BRITAIN
 

John, they also make a 3 way and a 4 way version of that power divider. 
And while a Wilkison power divider has isolation between the output ports,
this design does not. Kent



On Friday, June 11, 2021, 02:12:25 AM CDT, John Lemay <john@...> wrote:


Curiosity got the better of me, and I ordered a broadband two way power
splitter on eBay. It's specified as being useable from 800 to 2500MHz, and
I've confirmed that it has a decent (but not brilliant) return loss over
that bandwidth.

The attached picture shows the power splitter de-constructed. The inner line
is stepped, each section being about 42mm long and the pin to pin length is
175mm. A quick and dirty measurement and calculation shows the impedance of
each section will be 48, 40, 32 and 28 ohms.

Can anyone give me a simple explanation of how this splitter works ?

Many thanks

John







John Lemay
 

Andy and Kent

 

Many thanks for your explanation about how the broadband splitter works – very helpful.

 

Further measurements:-

 

Connected in the conventional manner, looking at S11 on the common port, the RL is better than 20dB from 725 to 2670MHz, and better than 30dB from 970 to 1925MHz.

 

Looking into an output port with the others terminated, the RL is 6dB and is essentially flat to 3000MHz.

 

The isolation between the output ports with the input terminated is circa 6dB, with a dB or so of ripple.

 

Construction is interesting – the outer and inner components are each a single piece casting, either aluminium or something of similar mass. The N connectors were screwed in pretty tight but there is no gasket and no evidence of sealant.

 

Regards

 

John G4ZTR

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 11 June 2021 08:19
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Broadband coaxial power splitter

 

What's the return loss of one of the two output ports with the others terminated?

And the isolation between them?

 

 

 

 

 

On Fri, 11 Jun 2021 at 08:12, John Lemay <john@...> wrote:

Curiosity got the better of me, and I ordered a broadband two way power
splitter on eBay. It's specified as being useable from 800 to 2500MHz, and
I've confirmed that it has a decent (but not brilliant) return loss over
that bandwidth.

The attached picture shows the power splitter de-constructed. The inner line
is stepped, each section being about 42mm long and the pin to pin length is
175mm. A quick and dirty measurement and calculation shows the impedance of
each section will be 48, 40, 32 and 28 ohms.

Can anyone give me a simple explanation of how this splitter works ?

Many thanks

John






KENT BRITAIN
 

John, and they can get even more extreme

There is a TV CH 2,  54-60 MHz station near here with a 15 bay array.

The power divider contains a 7 way and an 8 way version of that power divider.

The input section of those two dividers are tapered to act like a 2 way splitter.
Never have found out if that two way is configured to be an unequal divider or 
someone just said it's no big deal and installed it as is.  Kent



On Friday, June 11, 2021, 07:56:07 AM CDT, John Lemay <john@...> wrote:


Andy and Kent

 

Many thanks for your explanation about how the broadband splitter works – very helpful.

 

Further measurements:-

 

Connected in the conventional manner, looking at S11 on the common port, the RL is better than 20dB from 725 to 2670MHz, and better than 30dB from 970 to 1925MHz.

 

Looking into an output port with the others terminated, the RL is 6dB and is essentially flat to 3000MHz.

 

The isolation between the output ports with the input terminated is circa 6dB, with a dB or so of ripple.

 

Construction is interesting – the outer and inner components are each a single piece casting, either aluminium or something of similar mass. The N connectors were screwed in pretty tight but there is no gasket and no evidence of sealant.

 

Regards

 

John G4ZTR

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Andy G4JNT
Sent: 11 June 2021 08:19
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Broadband coaxial power splitter

 

What's the return loss of one of the two output ports with the others terminated?

And the isolation between them?

 

 

 

 

 

On Fri, 11 Jun 2021 at 08:12, John Lemay <john@...> wrote:

Curiosity got the better of me, and I ordered a broadband two way power
splitter on eBay. It's specified as being useable from 800 to 2500MHz, and
I've confirmed that it has a decent (but not brilliant) return loss over
that bandwidth.

The attached picture shows the power splitter de-constructed. The inner line
is stepped, each section being about 42mm long and the pin to pin length is
175mm. A quick and dirty measurement and calculation shows the impedance of
each section will be 48, 40, 32 and 28 ohms.

Can anyone give me a simple explanation of how this splitter works ?

Many thanks

John