How to control PA output power linearly?

[easyads]

pa output power

I am design a blutooth PA with output power 4dBm. But the output power must be controled from -30dBm to 4dBm.
1. How can power control be realized? Someome says that using an voltage attenuator to attenuate the input rf signal is an good method. How can an attenuator be realized in cmos or bipolar porocess, could you give the schematic?

2. PA output power control can also realized by changing biasing current or voltage.
But this method can not obtain good linearity. How about this method?
Best Regards

 

[rficd]

pa output power control

you can obtain linear PA by 1)feedback 2)dynamic power supply.

 

[BigBoss]

By moving the biasing current of the amplifier will give a gain control but it won't be linear and will create distortion at low level bias currents.

The best way is to use attenuator by switching resistor values ( series or parallel) by aid of MOS transistors.

So, by this way, a very accurate attenuation values can be obtained.

Look at that datasheet and be inspired from them..
https://www.hittite.com/product_info/product_specs/attenuators/hmc542lp4.pdf

 

[DDavid]

Hi,

Check it for control power!



I put schematic my inside!

David

 

[hr_rezaee]

Hi
see doherty amps
regards

 

[easyads]

DDavid, I can not open your website to see your schematic. could you please post your schematic again?