High-Dynamic-Range, Direct Up-/Downconversion

750MHz to 1200MHz Quadrature Mod/Demod

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11

R2, and R3. Tables 1 and 2 outline the performance

trade-offs that can be expected for various combina-

tions of these bias resistors. As noted within the tables,

the performance trade-offs may be more pronounced

for different operating frequencies. Contact the factory

for additional details.

Layout Considerations

A properly designed PC board is an essential part of

any RF/microwave circuit. Keep RF signal lines as short

as possible to reduce losses, radiation, and induc-

tance. For the best performance, route the ground pin

traces directly to the exposed pad under the package.

The PC board exposed paddle MUST be connected to

the ground plane of the PC board. It is suggested that

multiple vias be used to connect this pad to the lower-

level ground planes. This method provides a good

RF/thermal conduction path for the device. Solder the

exposed pad on the bottom of the device package to

the PC board. The MAX2021 evaluation kit can be used

as a reference for board layout. Gerber files are avail-

able upon request at www.maxim-ic.com.

Power-Supply Bypassing

Proper voltage-supply bypassing is essential for high-

frequency circuit stability. Bypass all VCC_ pins with

33pF and 0.1µF capacitors placed as close to the pins

as possible. The smallest capacitor should be placed

closest to the device.

To achieve optimum performance, use good voltage-

supply layout techniques. The MAX2021 has several RF

processing stages that use the various VCC_ pins, and

while they have on-chip decoupling, off-chip interaction

between them may degrade gain, linearity, carrier sup-

pression, and output power-control range. Excessive

coupling between stages may degrade stability.

Exposed Pad RF/Thermal Considerations

The EP of the MAX2021’s 36-pin thin QFN-EP package

provides a low thermal-resistance path to the die. It is

important that the PC board on which the IC is mounted

be designed to conduct heat from this contact. In addi-

tion, the EP provides a low-inductance RF ground path

for the device.

The exposed paddle (EP) MUST be soldered to a

ground plane on the PC board either directly or through

an array of plated via holes. An array of 9 vias, in a 3 x

3 array, is suggested. Soldering the pad to ground is

critical for efficient heat transfer. Use a solid ground

plane wherever possible.

LO FREQ

(MHz)

RF FREQ

(MHz)

R1

(

Ω

Ω

Ω

Ω)

R2

(

Ω

Ω

Ω

Ω)

R3

(

Ω

Ω

Ω

Ω)

(mA)

OIP3

(dBm)

LO LEAK

(dBm)

IMAGE REJ

(dBc)

OIP2

(dBm)

420

620

330

271

19.6

-32.1

23.9

50.5

453

665

360

253

21.9

-32.7

34.0

51.0

499

698

402

229

18.9

-33.7

30.0

52.6

549

806

464

205

15.7

-34.4

23.7

46.0

800

801.8

650

1000

550

173

13.6

-34.2

23.3

32.3

420

620

330

271

20.7

-31.4

43.4

54.0

453

665

360

253

21.6

-31.6

42.4

55.4

499

698

402

229

20.6

-31.8

42.7

59.8

549

806

464

205

19.0

-31.9

40.3

50.7

900

901.8

650

1000

550

173

14.9

-30.5

25.0

34.6

420

620

330

271

22.4

-32.8

39.3

55.5

453

665

360

253

22.2

-33.2

39.1

56.3

499

698

402

229

19.9

-33.8

43.5

55.0

549

806

464

205

17.6

-34.8

40.5

51.4

1000

1001.8

650

1000

550

173

14.6

-33.9

36.8

32.8

Table 1. Typical Performance Trade-Offs as a Function of Current Draw—Modulator Mode