Interstage filtering between FM RF amps?
 

My question is whether I need interstage filtering between two 900MHz
saturated amplifiers in an FM (FSK) transmitter. One stage is the driver
amplifier outputting about +15dBm, and the other stage is the PA, outputting
+30dBm. I want to keep parts count and insertion losses down, but do I need
such filtering to keep mixing products to a minimum, or is the standard TX
output bandpass filter all that I need in an FM system?

Many Thanks!

Mike

On 16 Sep 2003 00:47:01 GMT, (ForNewsPost) wrote:


My question is whether I need interstage filtering between two 900MHz
saturated amplifiers in an FM (FSK) transmitter. One stage is the driver
amplifier outputting about +15dBm, and the other stage is the PA, outputting
+30dBm. I want to keep parts count and insertion losses down, but do I need
such filtering to keep mixing products to a minimum, or is the standard TX
output bandpass filter all that I need in an FM system?

What "mixing products"? The signal into the driver should be fairly
clean of unwanteds - if it isn't, that's a problem to be fixed in the
exciter.

I'd personally use interstage impedance matching with just a low-pass
which is often inherent in the matching circuit.

On 16 Sep 2003 00:47:01 GMT, (ForNewsPost) wrote:


My question is whether I need interstage filtering between two 900MHz
saturated amplifiers in an FM (FSK) transmitter. One stage is the driver
amplifier outputting about +15dBm, and the other stage is the PA, outputting
+30dBm. I want to keep parts count and insertion losses down, but do I need
such filtering to keep mixing products to a minimum, or is the standard TX
output bandpass filter all that I need in an FM system?

What "mixing products"? The signal into the driver should be fairly
clean of unwanteds - if it isn't, that's a problem to be fixed in the
exciter.

I'd personally use interstage impedance matching with just a low-pass
which is often inherent in the matching circuit.