Please help with front-end matching for best sensitivity using RFSim99.
I'm now trying to match Max2644 LNA with LT5534 Power Detector using RFSim99 software. Max2644 comes with s2p file and LT5534 comes with s1p file.
so, the diagram of the receiver looks like this --> Port1 + Max2644 + LT5534 + Port2
I hope that Max2644 can increase the sensitivity by at least 16 dB but not sure if it would be as I thought. RF input range of LT5534 is from -63dBm to -3 dBm. By putting Max2644 in front and a proper matching lump in between, can it help improve the sensitivity of my circuit to at least -63-16 = -79 dBm ?
I'm trying to use the 'auto match' function in RFSim99 but found that it can only match with reference to Port1 and Port2. Now, I don't need any matching for Port2 as LT5534 gives out DC output. I need it to match the part in front of Max2644 and the part between Max2644 and LT5534 for me but can't do so. Could any expert here explain me why pleaseee.
Lastly, it would be grateful if you could tell me any recipe for the 'matching for best sensitivity' please. Right now, I'm still a little bit confused between 'best gain' and 'best NF' really. And the result of manual matching using Smith Chart is not always in line with the result of 'Auto-Matching' facility in RFSim99.
Thank you so much for your kind help.
Pete
PS. sorry for my english. it needs a bit of brush-up.
It will work, and for sure you get better sensitivity using an LNA at the front end.
The problem is that MAX2644 needs external matching networks, and in this way the bandwidth of the LNA would be relative narrow.
You can use one of the low-noise MMICs from Minicircuits which are wideband and have 50 ohms input/output (don't need matching networks).
Mini-Circuits
Thank you for your suggestion. This will be very useful for this project and also my other projects as well.
However, I'm still confused when you said it doesn't need a matching circuit, especially when it is designed for wideband application like this.
For example, if i want to use it at 2 GHz then the matching circuit would be needed to match the S11 at 2GHz, wouldn't it. From the information of the LNA you sent me, SAV-581+ seems to suit my job well. And if I assutmed that there is no need for the matching circuit at the input of the IC, what about between the SAV-581+ and LT5534 ? Do I need to use Smith Chart to find the matching between S22 of SAV-581+ to S11 of LT5534 ?
Your help is much appreciated.
Pete
Those MMICs due to their internal configuration have 50 ohms input/output impedance and doesn't need external matching.
As is shown in the LT5534 datasheet the input has various reactive impedance vs frequency, but the test measurements were done using just a series DC blocking cap and a shunt 47 ohms resistor.
So using this configuration can connect the MMIC to the detector without any matching network.
If you use the detector for one frequency can put a simple LC matching network, perheaps increasing the sensitivity of the detector with few dB's.
I guess you need config as: port1+LNA+coupler+port2, and coupler to detector.
So the LNA gain should be -63-(-79)+coupler loss, say the coupler loss is 20dB, so the LNA gain is 36dB, and you should consider the NF.
hello..... i need to know where to get the spice model for Max2644? pl help... i need the simulation model for it...