AN 074 Rev E

17 / 24

19-November-2002

Applications Note No. 074

Silicon Discretes

An advantage of either the stand-alone BGA430

or BGA430 + BGB540 I.F. Amp solution is the

exceptionally low noise figure provided.

The

complete amplifier with the gain-sloping high

pass filter has a noise figure of well under 3 dB.

A plot of measured noise figure for one complete

unit may be viewed in Appendix C on page 23.

Depending on the gain and noise figure

performance of the LNB’s Low Noise Amplifier

and Mixer sections, the excellent noise figure of

the I.F. amplifier presented here could provide

additional design margin for receiver sensitivity,

and possibly enable the use of lower cost

approaches for the LNA and mixer stages.

Conclusion

The BGA430 and BGB540 both provide a cost-

effective and flexible solution for today’s price-

sensitive Direct Broadcast Satellite LNB I.F.

Amplifier designs. A simple, low-cost approach

was shown for achieving a positive gain slope in

a 950 – 2150 MHz I.F. Amplifier. The BGA430

used as a stand-alone I.F. Amplifier requires

only 3 external components, and the complete,

gain-sloped I.F. Amplifier using both BGA430

and BGB540 with an interstage high pass filter

allows the LNB designer to compensate for

overall LNB gain roll-off in the Intermediate

Frequency

range,

where

gain

roll-off

compensation is easier and less costly to

achieve than at the 12 GHz RF input frequency

range.

Additional output power may be had

from the BGA430 by running it up to a maximum

of +6.5 volts. The exceptionally low noise figure

of the I.F. Amplifier presented – under 3 dB –

may help the LNB designer achieve additional

sensitivity margin for his or her product.

The

Applications

Board

shown

in

this

Applications Note is available from Infineon

Technologies.

References

[1]

Mass, Stephen A.

“Microwave Mixers”,

Second Edition. Artech House, 1993. (General

reference is on mixers, including the use of

FETs as active or resistive mixers).

[2] Mass, Stephen A. “The RF and Microwave

Design Cookbook”, First Edition, Artech House,

1998. ISBN 0890069735. Another reference on

mixers, including single-device FET mixers.

[3] Eagleware Corporation, 653 Pinnacle Court,

Norcross,

GA

30071

USA.

Tel:

Eagleware software suite GENESYS Version 8

was used in all simulation, synthesis, and PC

board CAD file generation done for the circuit

described in this Applications Note.

Performance Plots of complete LNB I.F. Amplifier, and Appendixes A – C begin on the following page.