LT5520EUF データシートの表示（PDF） - Linear Technology

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LT5520EUF

1.3GHz to 2.3GHz High Linearity Upconverting Mixer

Linear Technology 

LT5520

APPLICATIO S I FOR ATIO

100Ω

C1

0.1%

18mA

T1

2

IFIN

4:1

50Ω

C3

VCC

3

C2

100Ω

18mA

0.1% LT5520

5520 F03

Figure 3. IF Input with External Matching

LOIN

50Ω

LO+

14

5pF

220Ω

VCC

85Ω

15 LO–

LT5520

5pF 220Ω

5520 F04

Figure 4. LO Input Circuit

Table 1 lists the differential IF input impedance and reflec-

tion coefficient for several frequencies. A 4:1 balun can be

used to transform the impedance up to about 50Ω.

Table 1. IF Input Differential Impedance

Frequency

(MHz)

Differential Input

Impedance

Differential S11

Mag

Angle

10

10.1 + j0.117

0.663

180

44

10.1 + j0.476

0.663

179

70

10.1 + j0.751

0.663

178

140

10.2 + j1.47

0.663

177

170

10.2 + j1.78

0.663

176

240

10.2 + j2.53

0.663

174

360

10.2 + j3.81

0.663

171

500

10.2 + j5.31

0.663

167

LO Input Port

The simplified circuit for the LO buffer input is shown in

Figure 4. The LO buffer amplifier consists of high-speed

limiting differential amplifiers, optimized to drive the mixer

quad for high linearity. The LO+ and LO– ports can be

driven differentially; however, they are intended to be

driven by a single-ended source. An internal resistor

connected across the LO+ and LO– inputs provides a

broadband 50Ω impedance match. Because of the resis-

tive match, a DC voltage at the LO input is not recom-

mended. If the LO signal source output is not AC coupled,

then a DC blocking capacitor should be used at the LO

input.

Though the LO input is internally 50Ω matched, there may

be some cases, particularly at higher frequencies or with

different source impedances, where a further optimized

match is desired. Table 2 includes the single -ended input

impedance and reflection coefficient vs frequency for the

LO input for use in such cases.

Table 2. Single-Ended LO Input Impedance

Frequency

(MHz)

Input

Impedance

S11

Mag

Angle

1300

62.8 – j9.14

0.139

– 30.9

1500

62.2 – j11.4

0.148

– 37.1

1700

61.5 – j13.4

0.157

– 42.4

1900

60.0 – j15.2

0.164

– 48.9

2100

58.4 – j16.9

0.172

– 54.7

2300

56.5 – j17.9

0.176

– 60.4

2500

54.9 – j18.8

0.182

– 65.1

2700

53.7 – j18.8

0.182

– 68.5

RF Output Port

An internal RF transformer, shown in Figure 5, reduces the

mixer-core impedance to provide an impedance of 50Ω

across the RF + and RF – pins. The LT5520 is designed and

tested with the outputs configured for single-ended opera-

tion, as shown in the Figure 5; however, the outputs can be

used differentially as well. A center-tap in the transformer

provides the DC connection to the mixer core and the

transformer provides DC isolation at the RF output. The

RF+ and RF– pins are connected together through the

secondary windings of the transformer, thus a DC voltage

should not be applied across these pins.

5520f

7

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