topic Re: AFT05MS031 for wide band application 30-512MHz in NXP Designs

AFT05MS031 for wide band application 30-512MHz

gs_sureshkumar — Sat, 11 Jan 2020 07:13:41 GMT

I would like to used this device in 30-512MHz Broad band application. I look our for reference design.

Not able to install Microwave office and ADS models forwideband application simulation. ATF05003 3W device is used as driver.

Re: AFT05MS031 for wide band application 30-512MHz

LPP — Fri, 17 Jan 2020 11:32:12 GMT

>Not able to install Microwave office and ADS models for wideband application simulation.

Try to solve this problem. Using ADS/AWR simulation is the most reliable way to design RF amplifier.

>I would like to used this device in 30-512MHz Broad band application.

Unfortunately, we have no a ready for use design for your application.

This device has low input and output impedances (typical 1.5 Ohm source and 3 Ohm output) and it will require broadband matching circuits to cover the target frequency band. NXP broadband reference designs for AFT05MS031 provide 3 LC stages to achieve 20% bandwidth.

LC impedance matching will require more stages to implement 30-512MHz bandwidth. This approach is not reasonable if more than octave bandwidth is required. General solution is to use broadband transmission line transformers. AFT05MS031 will need impedance 16:1 transformation at input and output.

Useful links, amplifies with TL impedance matching:
http://www.polyfet.com/HFE0503_Leong.pdf
https://www.ampleon.com/documents/application-note/AN10858.pdf

Note. AFT05MS031 design for 30-512MHz is difficult to implement because of it's low source/load impedances. It would be much easier to implement broadband amplifier using a device that has higher source/load impedances (closer to 50 Ohm).

It is possible if using 50V or 65V supply devices. For example, MRFE6VS25N, MRFX035 or MRFE6VP100H.

Have a great day,

Pavel
TIC

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Re: AFT05MS031 for wide band application 30-512MHz

gs_sureshkumar — Fri, 17 Jan 2020 12:25:37 GMT

I agree low source and load impedance, it is difficult to design in my restricted size.
It is not possible to use high voltage devices as the system is battery operated.
Is there any other devices would like to recommend with 12V supply for this application.
Let me check in detail on the application notes shared and workout a solution.

Re: AFT05MS031 for wide band application 30-512MHz

LPP — Mon, 20 Jan 2020 09:25:36 GMT

NXP offers a portfolio for RF Mobile Radio. These devices are optimized to provide full performance at 7.5-13.6V supply.
https://www.nxp.com/products/rf/rf-power/rf-mobile-radio:RF-MOBILE-RADIO#/

Have in mind that optimal load impedance is Rload = (VDD-V_sat)^2/(2*P_load). So, if you need to achieve high power at low supply voltage, the optimal load impedance must be low. For example, 30W @ 12.5V,V_sat=0.1*VDD -> Rload = 2.1 Ohm. In the case of 50V device, optimal load will be 16 times more!

So, RF mobile devices (==low VDD) would have low load impedance and thus they could be difficult to build broadband (more than octave) amplifier.

What is your application? Typical mobile radio uses narrow bands to communicate. Common approach is to implement amplifier with a set of band tuned impedance matching and filter circuits.

Have a great day,

Pavel
TIC

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