9

LT5525

5525f

APPLICATIO S I FOR ATIO

single-ended drive, though differential drive can be used if

desired. The LO input is internally matched to 50Ω. A

simplified schematic for the LO input is shown in Figure 7.

Measured return loss is shown in Figure 8.

If the LO source has a DC voltage present, then a coupling

capacitor should be used in series with the LO input pin

due to the internal resistive match.

The LO port input impedance and reflection coefficient

(S11) versus frequency are shown in Table 2. The listed

Table 2. Single-Ended LO Input Impedance

FREQUENCY

INPUT

REFLECTION COEFFICIENT

(MHz)

IMPEDANCE

MAG

ANGLE

100

93.1 – j121

0.686

–30

250

55.8 – j54

0.457

–57

500

47.7 – j28

0.276

–79

1000

42.3 – j14

0.171

–110

1500

38.5 – j9.3

0.166

–135

2000

35.8 – j7.8

0.187

–146

2500

34.8 – j7.8

0.281

–148

3000

34.2 – j8.7

0.214

–149

IF Output Port

A simplified schematic of the IF output circuit is shown in

nected to the collectors of the mixer switching transistors.

Both pins must be biased at the supply voltage, which can

be applied through the center-tap of a transformer or

Figure 7. LO Input Schematic

Figure 9. IF Output with External Matching

Figure 8. LO Input Return Loss

Figure 5. Wideband RF Input Matching

Figure 6. RF Input Return Loss Using

Wideband Matching Network

2

L3

1.5nH

C5

4.7pF

LT5525

5525 F05

3

RF FREQUENCY (MHz)

500

–30

–25

–20

–15

–10

–5

0

1000

1500

2000

2500

5525 F06

3000

SERIES 1.5nH

AND 4.7pF

NO EXTERNAL

RF MATCHING

14

480Ω

20pF

20pF

50Ω

LT5525

5525 F07

15

54Ω

FREQUENCY (MHz)

0

–20

–15

–10

–5

0

500

1000

1500

2000

5525 F08

2500

3000

10

11

575Ω

C3

5525 F09

L3

T2

4:1

L2

0.7pF

LT5525