Power amplifier type to decide
I have a BPSK/QPSK type signal from a transmitter. Carrier frequency is 400 MHz and data rate is 1 Mbps. The BPSK/QPSK signal is to be transmitted to a remote receiver. What type of power amplifier should I use as the output stage?
You can go for Class D PA as it gives very high efficiency for phase modulated signals.
Thank you for the quick reply.
You mean to use non-linear or switching power amplifier for the BPSK signal? I am not really fluent with RF PAs, but I have some questions, will the phase information at the input of the PA be same as at its output? Is ACPR related to the non-linearity of a PA. If it is, then I cant spill to much power in adjacent channels... A non-linear PA will not do then, please give me your thoughts...
The phase information in the output will be same as that of the input with a constant delay for all the frequencies in the band of interest.
ACPR is related to the intermadulation components (IM3 and so on) of the PA and not to the 2nd or higher harmonics. Hence, you should still design the PA for good IM3 numbers. Yes, you need to keep it up to the ACPR linearity specifications. But, you can do so with a class D PA too.
Thanks for the insights.
So do I need to add linearization techniques to the class D amplifier to increase its linearity ?
Yeah, you can add techniques such as Predistortion, feed forward linearization etc. to improve the intermodulation linearity of the PA, if the intrinsic linearity performance of the PA is not good enough.
Hello AMS012,
I did a circuit just using a resonant circuit to see if phase information is restored in a LC tank and this is what I found. I am attaching the circuit. The BPSK signal is generated by multiplying a 100 MHz sine wave with a (+1V, -1V) varying 1 MHz pulse wave. 1st waveform is output of the multiplier, 2nd is voltage across capacitor, unfortunately the phase information is not maintained.
Shouldn't you be resonating parallely at about 100MHz?