AN 074 Rev E

13 / 24

19-November-2002

Applications Note No. 074

Silicon Discretes

Figure 20. Insertion loss of 30.4 meter / 100 foot section of 75 ohm coaxial cable. Measurement

system impedance is 50 ohms. Gain slope for this section is -3.55 dB / GHz.

CH1

S 21

log MAG

1 dB/

REF -9 dB

START 900.000 000 MHz

STOP 2 200.000 000 MHz

Cor

Avg

8

Smo

Del

PRm

REFERENCE VALUE

-9 dB

31 Jul 2002 10:33:48

1

2

3

2_:-11.134 dB

1 450.000 000 MHz

1_:-9.281 dB

950 MHz

3_:-13.537 dB

2.15 GHz

Table 3. Return Loss & Insertion Loss vs.

Frequency, 15.2 m / 50 ft and 30.4 m / 100 ft

sections of 75 ohm coaxial cable.

Cable

Length

m / ft

Parameter

Frequency, MHz

950

1450

2150

15.2 / 50

Input Return Loss, dB

17.1

19.6

14.9

15.2 / 50

Insertion Loss, dB

-4.1

-4.9

-6.0

30.4 / 100

Input Return Loss, dB

18.7

19.2

16.0

30.4 / 100

Insertion Loss, dB

-9.3

-11.1

-13.5

7. Complete Gain-Sloped LNB I.F. Amplifier

with both BGA430 & BGB540 MMICs

The basic approach taken for the complete I.F.

Amp was to create a positive gain slope (gain

increases with increasing frequency) via use of a

simple, low-cost High Pass Filter (HPF) between

the BGA430 and BGB540 MMICs. The HPF

between the two MMICs has the effect of

reducing the overall amplifier gain below the

filter’s cutoff frequency, allowing one to achieve

a positive gain slope.

Please refer to the

Schematic Diagram, Figure 8 on page 6. Shunt

inductor L1 and series capacitor C4 form a high-

pass filter with a 3 dB corner frequency near

1860 MHz. Computer simulation in Eagleware’s

synthesis tools, permitted fast and easy design

optimization for the best overall amplifier gain

response. To give the reader an idea of the

interstage high pass filter’s shape, please refer

to Figure 21 on the next page. This is a plot of

simulated filter insertion loss and return loss

which was exported from GENESYS.