RFID 13.56Mhz power amp design

Hi all. I wish I had found this forum a little sooner.
I'm trying to design a RF power amplifier to work at 13.56Mhz. I'm trying to amplify the transmit power from a Texas Instrument TRF7960 reader IC. I want an output power of 8 Watts to power up an antenna that I have built. Reason for this much power is we want to be able to achieve a read range of 1meter. I'm stuck on the power ampflier. Whatever i've designed is not giving me any gain. but a loss. I have simulated my design and it gives me a gain of 9, however when built on a breadboard I'm not getting what is desired.
Some input would be appreciated.attached is a design schematic
thanks.

By design, the amplifier output power is limited to a few mW. Fortunately this assures survival of the 2N2222 which won't be able to deliver the said 8W output, at least not in a linear PA.
If I remember right, a 13.56MHz PA has been discussed some weeks ago at EDAboard, I suggest to search a bit more thoroughly.
When extending RFID operation volume, the respective regulations for maximum far field should be observed (if a legal application is intended).
As another remark: A 13.56 MHz "antenna" should be regarded rather as an inductive coupler. It is used in a resonant circuit and the input power is mainly consumed by resistive losses. With a suitable coupler design, it's not necessary to dissipate several watts for a 1 m range to my opinion.

okay. i built that amp on PCB and it works... but i'm not getting the desired gain i need. I'm thinking that i need to design a different, smaller antenna for this to work. i'll look into inductive coupler as mentioned.

In your actual prototype did you install bypass capacitor(s) to power supply?

Nope. The schematic above is exactly what I built
Hey all. I'm a little stumped on how to perform impedance matching between the antenna and the amplifier. The antenna i built was built to spec and had an impedance of 50 ohms.Now i know i must match it with my transmit signal but i don't know what components to use. unfortunately i don't have a network analyzer to give me the specific real and imaginary values.
i've attached a block diagram of what i have.
the capacitive coupling block is what is tuning the antenna for 50 ohms.
thanks for the help.

You need to install bypass capacitor of 4700pF. You may tune your matching circuit without network analyzer with FM receiver. Put receiver at the distance that provide light coupling to the transmitter and then tune matching circuit until you get the best signal from receiver. Reduce coupling when signal become strong.

the bypass cap is used to kill off the AC going back to the supply ?i'll give that a try. I'll have to check and see if i can get a FM receiver for 13.56mhz.
thanks.

Sorry, I mistakenly told you about FM receiver. Your application is 13.56MHz. Bypass capacitor for this frequency must be 470000pF or 470nF. You need receiver for this frequency not FM. Or you can use field meter which is just a resonant tank, tuned to desired frequency and piece of wire as antenna. Connect simple amplitude detector to this tank and you have a field meter. Place it at the distance when coupling to the transmitter is minimal and tune your matching circuit. Reduce the coupling when signal becomes stronger. This is old and well proven method for tuning homemade RF circuits.

humm. i was thinking of using a spectrum analzyer, which can detect 13.56mhz frequency. Use a pi-network to impedance matching of the transmitter to the antenna. the only problem is with the pi-network I dunno what values to start with... should they be variable caps and inductors ?
I'm pretty sure my antenna is tuned to the proper 13.56mhz because when i hook up a frequency generator to it the spectrum analyzer picks it up. The problem i'm having is when i hook up a transmitter that sends 13.56mhz to a amplifier, there is an impedance mismatch between the output of the amp with the tunning circuit of the antenna.
thanks for the input.

When you told that you have no network analyzer I decided that you have no access to RF test equipment. If you have it you may use spectrum analyzer instead of receiver or field meter. Moreover, you may build PI or T match circuit with adjustable caps and coil (there are a lot of coils with roller contact) and tune your matching circuit. Then just measure obtained Cs and L. Another way is to use the magazines of C and L if you have them in your lab. 13.56 MHz is not so high frequency, so it is possible to connect such devices without disturbing the circuit.
If you want to check how well your antenna is tuned try to change the frequency of signal generator and watch antenna response with spectrum analyzer. You will see where your antenna has maximum efficiency. Turn on MAX HOLD and you will see the plot of antenna gain vs. frequency.
If you know the impedance of transmitter and antenna send the numbers to me and I will return a few possible matching circuits to you.

Reader IC manufacturers, e.g. Philips/NXP have data sheets and application notes that discusses antenna matching. Knowing the L and R of your coupler coil, you are able to calculate a matching circuit and necessary input power to achieve a certain field strength at the tag location.

If your project is not your own but for the company, it probably make sense to buy impedance analyzer or one port network analyzer. I bought MFJ-259B impedance analyzer for my home lab only for $260. This analyzer can work from 1.8 to 170 NHz. Later I saw on the Internet one port network analyzers. The price from $400 to $1400 and they were looking well. It may be good alternative to very expensive VNA.

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