AD8341 Просмотр технического описания (PDF) - Analog Devices

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AD8341

1.5 GHz to 2.4 GHz RF Vector Modulator

Analog Devices 

REF LVL

MARKER 1 [T1 ]

–18.47dBm

–12dBm

1.95999900GHz

–12

0.3dB OFFSET

1

–20

–30

RBW 30kHz

VBW 100kHz

SWT 500ms

RF ATT 0dB

UNIT dBm

1 [T1]

–18.47dBm

1.95999900GHz

A

CH PWR

–4.06dBm

ACP UP

–77.64dBm

ACP LOW

–76.66dBm

–40

1AVG

–50

1RM

–60

–70

–80

–90

–100

C11

C11

C0

C0

CU1 CU1

–112

CENTER 1.96Hz

1MHz/

SPAN 10MHz

Figure 35. Output Spectrum, 1960 MHz, Single-Carrier CDMA2000

Test Model at −4 dBm, VBBI = VBBQ = 0.353 V, Adjacent Channel Power

Measured at ±2.25 MHz Carrier Offset in 1 MHz BW Input Signal Filtered

Using a Cavity Tuned Filter (Pass Band = 6.8 MHz)

Holding the differential I and Q control voltages steady at

0.353 V, input power was swept. Figure 36 shows variation in

spurious content, again measured at ±2.25 MHz carrier offset in

a 1 MHz bandwidth, as defined by the 3GPP2 specification.

–70

–72

–74

–76

–78

–80

–82

–84

–86

–88

–90

–20 –18 –16 –14 –12 –10 –8 –6 –4 –2 0

OUTPUT POWER (dBm)

Figure 36. Adjacent Channel Power vs. Output Power,

CDMA2000 Single Carrier @ 1960 MHz; ACP Measured at

±2.25 MHz Carrier Offset (1 MHz BW); VBBI = VBBQ = 0.353 V

With a fixed input power of 2.4 dBm, the output power was

again swept by exercising the I and Q inputs. VBBI and VBBQ were

kept equal and were swept from 100 mV to 500 mV. The result-

ing output power and ACP are shown in Figure 37.

AD8341

0

–60

–5

–65

–10

–70

–15

–75

–20

–80

–25

–85

–30

0

0.1

0.2

0.3

0.4

IQ CONTROL VOLTAGE

–90

0.5

Figure 37. Output Power and ACP vs. I and Q Control Voltages,

CDMA2000 Test Model, VBBI = VBBQ, ACP Measured at

±2.25 MHz Carrier Offset in 1 MHz BW

Figure 37 shows that for a fixed input power, the ACP (measured in

dBm) tracks the output power as the gain is changed.

WCDMA APPLICATION

Figure 38 shows a plot of the output spectrum of the AD8341

transmitting a single-carrier WCDMA signal (Test Model 1-64

at 2140 MHz). The carrier power is approximately −9 dBm. The

differential I and Q control voltages are both equal to 0.353 V,

that is, the vector is sitting on the unit circle at 45°. At this

power level, an adjacent channel power ratio of −61 dBc is

achieved. The alternate channel power ratio of −72 dBc is

dominated by the noise floor of the AD8341.

REF LVL

MARKER 1 [T1 ]

–28.39dBm

–24 –24dBm

2.14050000GHz

OFFSET 1dB

–30

–40

–50

–60

RBW 30kHz

RF ATT 0dB

VBW 300kHz

SWT 1s

UNIT dBm

1

1 [T1]

–28.39dBm

CH PWR

2.14050000GHz

–8.95dBm

A

ACP UP

–60.78dB

ACP LOW

–60.82dB

ALT1 UP

–72.67dB

ALT1 LOW

–72.66dB

1RM

–70

–80

–90

C12

C12

–100

–110

C11

–120

–124

CENTER 2.14GHz

C0

C0

C11

CU1

2.5MHz/

CU2

CU1

SPAN 25MHz

Figure 38. AD8341 Single-Carrier WCDMA Spectrum at 2140 MHz

Figure 39 shows how ACPR and noise vary with varying input

power (differential I and Q control voltages are held at 0.353 V).

At high power levels, both adjacent and alternate channel power

ratios increase sharply. As output power drops, adjacent and

alternate channel power ratios both reach minimums before the

measurement becomes dominated by the noise floor of the

AD8341. At this point, adjacent and alternate channel power

ratios become approximately equal.

Rev. 0 | Page 15 of 20

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