RadioBanter - View Single Post

April 24th 05, 10:07 AM

In article .com,
wrote:

I don't want to start another flame war. Byu your commnents in this
gorup for at least the last 4 years you have shown a good deal of
knowledge about RF.

Your position on transformer vs resitive hybrids confusses me. Based
on what I have read, transformer hybrids have 3 dB less loss then
resitive ones. From your firm stance it is clear that you disagree.
Since I respect your opinion I am interested on why you disagree.

Trying to move this to Email to avoid wasting space and because I
doubt if 1 SWL in 1000 care about this.

email r2000swl AT (replace with shift 2) hotmail dot com

Sorry for the mangled address but Google even hides email addresses
in the text of messages.

We can have differing opinions on politics and religion but this is
technical factual information and it's not a waste of space if it is on
topic.

The resistors in the divider don't connect to ground or the circuit
return so they don't consume power. They connect between the signal
paths and are an impedance matching network so that the input looks like
50 ohms to the signal source with two 50 ohm loads on the output ports
of the splitter, which are in parallel. Without the impedance matching
the power splitter would look like 25 ohms and a large reflection would
take place.

The insertion loss is usually in fractions of a dB due to the fact that
they are not perfect resistors and that the path through the divider is
not a perfectly continuous 50 ohm impedance path. Any deviation in a
signal paths impedance causes a power reflection back toward the signal
source and so is a power loss. This extra loss is usually less than 1 dB.

An insertion loss figure of merit is usually 1.5dB for anything in the
signal path.

Some manufactures specify their parts in division of power (3dB) and
some in voltage (6dB) in the case of a 1 to 2 splitter. In a 1 to 2
splitter that means that the power will be 3dBm less at either output
port than the input port and that the voltage swing with be 6dBV less at
either output port than the input port.

The insertion loss will be the extra loss over the power division loss
(3dBm or 6dBV) that is understood as the power division function.

I looked around on the net and did not come up much but here are some
links to applications notes on the Mini-circuits web site. They use
transformers in their splitters. You can compare their insertion loss
figures with the much wider bandwidth microwave resistive splitters on
other companies web sites.

Power splitter and combiners:

Understanding power splitters
http://www.minicircuits.com/appnote/psc2-2.pdf

Frequently asked questions
http://www.minicircuits.com/appnote/pwr2-4.pdf

--
Telamon
Ventura, California