MRI board performance and application

AN4016

14/17

Doc ID 022523 Rev 1

4

MRI board performance and application

The power amplifier has been measured on two different RF scalar test benches: RF Power

Lab. in STM Catania (Italy) and RF Power Lab. in STM Quakertown (USA): the

measurements are in good agreement (+ / -0.15 dB max. error). The test includes a 2

kW/CW attenuator and a pulsed RF generator with high power amplifier driver to manage

large signals at RF input (20 W min.) with good harmonic rejection (-30 dBc).

Figure 9.

Gain and IRL frequency response

Figure 9 shows the large signal gain frequency response of the amplifier, as well as the

input return loss, while Figure 10 shows the gain compression curve and the drain efficiency

curve Vs output power at 123 MHz (Idq = 200 mA and Vds = 100 V) and RF pulse width=1

msec, duty cycle=10%. The maximum efficiency is 60% @ 2.2 kW of output power.

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

5

7

9

11

13

15

17

19

21

23

25

105

110

115

120

125

130

135

PULSED WIDTH= 1msec, DUTYCYCLE =10%

Vds=100 VDC, Idq=2 x 100 mA

Gain

IRL

STAC244B

AM10225V1