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LTC5588-1

55881fb

Table 5. LOM Port Input Impedance vs Frequency for EN = Low

and PLOM = 10dBm (LOP Terminated with 50Ω AC to Ground)

FREQUENCY

(GHz)

LOM INPUT

IMPEDANCE

REFLECTION COEFFICIENT

MAG

ANGLE

0.2

92-j61

0.48

–32.1

0.25

83-j55

0.444

–36.9

0.3

75-j50

0.414

–42

0.4

66-j39

0.345

–49.3

0.5

60-j32

0.293

–57.4

0.6

56-j27

0.251

–63.2

0.7

53-j23

0.225

–71.2

0.8

50-j20

0.199

–78.8

0.9

48-j19

0.191

–86.6

1.0

46-j17

0.18

–93.6

1.2

42-j15

0.181

–108

1.4

40-j14

0.192

–117

1.6

38-j14

0.205

–123

1.8

37-j13

0.211

–127

2.0

36-j12

0.212

–132

2.5

35-j7.5

0.202

–150

3.0

31-j2.2

0.244

–172

3.5

27+j1.3

0.31

175

4.0

24+j2.7

0.363

171

4.5

22+j4.4

0.389

166

5.0

20+j6.8

0.433

160

5.5

18+j8.5

0.479

157

6.0

16+j9.5

0.525

154

APPLICATIONS INFORMATION

FREQUENCY (MHz)

200

–20

–10

600

55881 F04

–30

–40

300

400

500

RF PORT, EN = HIGH,

C7 = 4.7nH, C8 = 33pF

RF PORT, EN = LOW,

C7 = 4.7nH, C8 = 33pF

RF PORT, EN = HIGH,

C7 = 2.7nH, C8 = 10pF

RF PORT, EN = LOW,

C7 = 2.7nH, C8 = 10pF

LO PORT, EN = HIGH,

USING B0310J50100A00

LO PORT, EN = LOW,

USING B0310J50100A00

Figure 4. RF and LO Port Return Loss vs Frequency for Low Band

Match (See Figure 8)

RF FREQUENCY (MHz)

200

–6

–4

600

55881 F05

–8

–10

300

400

500

–2

3.3V, 85°C

3.3V, 25°C

3.15V, 25°C

3.45V, 25°C

3.3V, –40°C

Figure 5. Low Band Voltage Gain vs RF Frequency

Using Figure 4 Matching

The third harmonic content of the LO can degrade image

rejection severely, it is recommended to keep the 3rd-order

harmonic of the LO signal lower than the desirable image

rejectionminus6dB.Althoughthesecondharmoniccontent

of the LO is less sensitive, it can still be significant. The

large-signal noise figure can be improved with higher LO

input power. However, if the LO input power is too large to

cause the internal LO signal clipping in the phase-shifter

section, the image rejection can be degraded rapidly.

This clipping point depends on the supply voltage, LO

frequency, temperature and single ended vs differential LO

drive. At fLO = 2140MHz, VCC = 3.3V, T = 25°C and single-

ended LO drive, this clipping point is at about 16.7dBm.

For 3.15V it lowers to 16.1dBm. For differential drive it is

about 21.6dBm.

The differential LO port input impedance for EN = High

and PLO = 10dBm is given in Table 6.

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