How to measure the power efficiency of RF power amplifier

[pengboy]

hello,

I am tying to measure the power efficiency of a RF power amplifier.

what kind equipment should I use for measuring the power from RF input and output?

How to measure the power from the DC supply?

Thanks a lot!!!

 

[flatulent]

two methods

The power from the DC supply is current times voltage. Measureing the RF power is more difficult. You can use directly reading devices. Bird makes some meters. You can also use rf power meters by agilent and others.

You can also use a spectrum analyzer if you have a high power capacity attenuator or a directional coupler.

If you are short of instruments, you can put the dummy load in an insulated vat of water and measure the rate of temperature rise. If you assume all the power goes into heating the water and none escapes, you use the thermal capacity of water, and the rate of temperature rise.

 

[eladg]

Re: How to measure the power efficiency of RF power amplifie

hello,

I am tying to measure the power efficiency of a RF power amplifier.

what kind equipment should I use for measuring the power from RF input and output?

How to measure the power from the DC supply?

Thanks a lot!!!

eff = power out /(power in +power dc) *100
u need coupler to measure the power in and power meter
u need power meter (and att as requre)
and u need current meter and voltmeter

 

[pengboy]

Re: How to measure the power efficiency of RF power amplifie

hello,

I am tying to measure the power efficiency of a RF power amplifier.

what kind equipment should I use for measuring the power from RF input and output?

How to measure the power from the DC supply?

Thanks a lot!!!

eff = power out /(power in +power dc) *100
u need coupler to measure the power in and power meter
u need power meter (and att as requre)
and u need current meter and voltmeter

Hello,

What I don't uderstand is:

The current from the DC supply is also varying with a RF fundamental frequency. what kind current meter should i use?

power dc= Vdc*Idc

how to extract the Idc from the current mesurements.
Will the DC current meter gives the average current automaticly?

Thanks a lot

 

[Borber]

To measure DC power from power supply you need ordinary multimeter or two of them. One to measure DC voltage and second to measure average current from power supply if it hasn't them build in. They measure average values, you do not need any extractions. I suppose your amplifier has properly filtered supply voltage and supply voltage source has low DC resistance. At the same time you should measure output rf power. I do not know what kind of amplifier you have and can not answer you why is supply current changing with operating frequency. It could be because the gain is changing with frequency.

 

[flatulent]

bypass capacitors

The bypass capacitor on the collector or drain circuit of you amplifier supplies the pulses of current drawn by the transistor on each cycle. The capacitor is large enough that the voltage does not decline much from this. The power supply supplies the charge drained off by the transistor, but at a continuous rate. It is this continuous rate (current) your current meter will measure.

 

[eladg]

Re: How to measure the power efficiency of RF power amplifie

hello,

I am tying to measure the power efficiency of a RF power amplifier.

what kind equipment should I use for measuring the power from RF input and output?

How to measure the power from the DC supply?

Thanks a lot!!!

eff = power out /(power in +power dc) *100
u need coupler to measure the power in and power meter
u need power meter (and att as requre)
and u need current meter and voltmeter

Hello,

What I don't uderstand is:

The current from the DC supply is also varying with a RF fundamental frequency. what kind current meter should i use?

power dc= Vdc*Idc

how to extract the Idc from the current mesurements.
Will the DC current meter gives the average current automaticly?

Thanks a lot

to be on the safe side u can put big cap, and measure the curent that go into the cap, (the cap will do the average )