matching network definition

Can anyone tell me as I'm confused with matching network

In the datasheet, it stated that the component is internally matched to 50 ohms on all RF port, what does it mean? do I still need to do matching network?

From my understand: Matching is done to match the source and load impedance so to obtain the maximum power transfer to the load.
To connect a two different amplifier, does the source refers to the first amplifier(output) and the load connects to the second amplifier(input)? Please enlighten me

Thanks

If the datasheet says "the device is internally matched", it does not need an extra matching circuit.Double check that Input or Output is matched or both.
In general case, internally matched devices do not work in wide-band due to single frequency matched circuit.Take this caution into account..
Because if you intend to work in a wide-band, the device may fall.I do not like-personally-internally matched devices because their matching metrics are generally poor.But I don't know which component will you attempt to use...

Hi Big Boss,

Thank you for reply.

I need to connect a driver amplifier and a power amplifier for part of the communication system and connects to an antenna.
As checked from ADS software, the driver amplifier show it's impedance for S11 is 43.4+j*4.4 and S22 is 46.8-j*4.9, does it consider matched?
As for power amplifier, the S11 and S22 parameter is far off away from 50ohm and I have already done the matching network, just that if the driver amplifier also need to match then how am I suppose to connect both matching network?

Can you draw picture of how it should be connected in ADS of matching....sorry I cannot visualize it

Thanks in advance

If those impedances are given @ frequency of interest, they are pretty good.No need to matching circuit.

Thanks Big Boss,
by the way, do you know how to design a dual frequency patch antenna that works on 2.0GHz and 2.2GHz ?

Knowing that an impedance matching is needed for a patch antenna, but I have no idea how ADS can be done and how to put the matching network from ADS to HFSS. Can guide me (with drawing if possible).

Thanks

-I don't have sufficient knowledge about antennas..
-HFSS is a EM simulator, so transferring matching circuit from ADS to HFSS is is not possible because EM simulators cannot do circuit simulations.
-Obtain s-parameters of the antenna from HFSS and transfer these s-parameters into ADS and do your circuit simulations there..

In the datasheet the port impedance must be defined, otherwise it is impossible to use the chip. Most time people talks about "impedance matching", they actually mean matching to system impedance (50 OHM or 75 OHM). If you would connect several chips together, for example a low-pass filter after an LNA, then you may need to make sure the output impedance of the LNA is close to 50 OHM. Then the filter design could be easier by using standard prototype filter.

In your example you want to connect two amplifier together, you may don't care what is the actual source/load impedance, you just need them to be conjugate-matched to obtain the maximum gain.

While if the amplifier output is to feed another machine far away, a long connection cable is needed. In this case you must match your output impedance to the cable impedance (usually either 50 or 75 ohm). In this case the impedance is still conjugate-matched and the power loss is minimized. That is the why the IC manufacturer must specify the RF port impedance (most time they specify it as returnloss). Sometimes the output port returnloss may not so good, then you need to insert an impedance matching network to get "closer" to the system impedance of the front connectors (SMA, type-F, BNC...).

it's means that it does not need the matching network.

If your both amplifiers are internally matched to 50ohm, u can connect them together without any matching network.

Your point is mostly correct. Nevertheless in the real world I would add an impedance matching network in the middle as backup.

The first reason is that "match to 50 Ohm" is just the target in theory, the actual impedance may be 35-j*10 Ohm, or 40+j*20 Ohm. Also the impedance may be a function of frequency.

The second reason is there always some parasite effect in PCB which may distort the impedance.

So in my practice, I always add an impedance matching network in the prototype board. If the test results are excellent, everybody is happy. While most time we are not that luck. Tuning the circuit is necessary. Then the impedance matching network gives us the stage to play.