LTC5586 datasheet(20/34 Pages) LINER

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LTC5586

5586fa

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Figure 5. RF Input Return Loss

–5

–10

–15

–20

–25

–30

–35

RF FREQUENCY (GHz)

RFA, RFA SELECTED

RFB, RFB SELECTED

RFA, RFB SELECTED

RFB, RFA SELECTED

5586 F05

C2 = 0.3pF

TC = 25°C

–5

–10

–15

–20

–25

–30

RF FREQUENCY (GHz)

RFA, RFA SELECTED

C2 = 4.7pF

TC = 25°C

5586 F06

Figure 6. RF Input Return Loss with C2 = 4.7pF

As shown in Figure 5, the RF input ports are well matched

with return loss greater than 10dB over the frequency

range of 500MHz to 6GHz with a 0.3pF capacitor on C2.

The RF pins can be externally matched over the 300MHz

to 500MHz frequency range by changing C2 to 4.7pF.

Figure 6 shows the RF input return loss with C2 set to

4.7pF. Table 2 shows the impedance and input reflec-

tion coefficient for the RF input with C2 = 0.3pF. The

input transmission line length is de-embedded from the

measurement.

Table 2. RF Input Impedance

FREQUENCY

(MHz)

INPUT IMPEDANCE (Ω)

S11

MAG

ANGLE (°)

300

24.9 + j27.6

0.468

112.0

400

39.1 + j37.3

0.403

83.5

500

60.1 + j36.9

0.330

56.2

700

77.4 – j1.9

0.215

–3.2

1000

43.7 – j19.2

0.211

–96.7

1500

27.2 – j2.1

0.297

–173.2

2000

29.6 + j14.5

0.310

134.4

2500

39.3 + j26.0

0.303

96.0

3000

48.9 + j23.1

0.228

79.9

3500

52.4 + j19.2

0.185

72.3

4000

60.5 + j8.2

0.120

33.8

4500

69.2 + j15.0

0.202

30.8

5000

82.4 + j11.5

0.259

14.6

5500

71.2 – j8.6

0.188

–18.0

6000

46.8 – j13.1

0.138

–96.1

LO Input Port

The demodulator’s LO input interface is shown in Figure 7.

The input consists of a programmable input match and a

high precision quadrature phase shifter which generates

0° and 90° phase shifted LO signals for the LO buffer

amplifiers to drive the I/Q mixers. DC blocking capacitors

are required on the LOP and LOM inputs. When using a

LTC5586

5586 F07

0.3pF

1000pF

0.3pF

49.9

1000pF

MATCH

ADJUST

0º

90º

GND

LOM

INPUT

(MATCHED)

LOP

VCC

Figure 7. Simplified Schematic of the LO Inputs

with Single-Ended Drive

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