RF2461PCBA-41X datasheet(6/12 Pages) RFMD

6 / 12 page

8-108

RF2461

Rev B6 060925

Application Schematic

VCC1

100 pF

33 nF

16 nH

4.3 nH

IF SEL

100 pF

VCC1

100 pF

Ω μstrip

620

4 pF

100 pF

0.1

μF

VCC1

22 k

47 k

3.3 nH

LNA GAIN

MIX GAIN

VCC2

VCC1

NOTE:

Microstrip Inductor, Z

0 = 50 Ω, L = 102 mils

suggested compared values.

Ω*

Filter

33 nF

47 nH

Filter

IF+

IF-

Filter

IF2+

IF2-

LO IN

LNA IN

7.5 nH

Ω μstrip

L=130 mils

W=12 mils

0=50 Ω

ENABLE

IP SET

*This resistor improves NF and IIP3 for

CC = 3.0 V.

BYPASS

See

Note 4

See

Note 5

See

Note 3

See

Note 1

See

Note 6

See

Note 8

See

Note 8

See

Note 8

See

Note 8

See

Note 7

See Note 2

See Note 8

See

Note 10

See Note 11

See

Note 9

NOTES:

1. DC blocking capacitor.

2. LNA emitter degenerator. As the value of inductance is increased, the gain will decrease, and the IIP3 will increase.

3. Mixer preamp degeneration inductor. As the value of inductance is increased, the gain will decrease, and the IIP3 will increase.

4. An external resistor connected to this pin sets the current of the preamp and the mixer. Higher resistance to ground results in lower current. See chart at end of datasheet.

5. An external resistor connected to this pin sets the current of the LNA when IPSET is high. Higher resistance to ground results in lower current. See chart at end of datasheet.

6. Mixer input matching inductor.

7. LO input matching resistor.

8. Bypass capacitor.

9. LNA output matching and bias choke.

10. For stability of the LNA.

11. LNA input and output matching.

12. Low pass path to ground for two-tone beat frequency for optimum IIP3 of LNA.

See Note 11

See Note 12

See Note 8

Output Interface Network

L1, C1, and R form a current combiner which performs

a differential to single-ended conversion at the IF fre-

quency and sets the output impedance. In most cases,

the resonance frequency is independent of R and can

be set according to the following equation:

Where CEQ is the equivalent stray capacitance and

capacitance looking into pins 11 and 12. An average

value to use for CEQ is 2.5pF to 3pF.

R can then be used to set the output impedance

according to the following equation:

where ROUT is the desired output impedance and RP is

the parasitic equivalent parallel resistance of L1.

C1 should be chosen as high as possible (not greater

than 15pF), while maintaining an RP of L1 that allows

for the desired ROUT.

L2 and C2 serve dual purposes. L2 serves as an out-

put bias choke, and C2 serves as a series DC block.

In addition, L2 and C2 may be chosen to form an

impedance matching network if the input impedance of

the IF filter is not equal to ROUT. Otherwise, L2 is cho-

sen to be large, and C2 is chosen to be large if a DC

path to ground is present in the IF filter, or omitted if the

filter is DC blocked.

π L1

(C1 + C

EQ)

IF =

R =

4 R

OUT

- 1

()

-1

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