Specifications and information are subject to change without notice

WJ Communications, Inc • Phone 1-800-WJ1-4401 • FAX: 408-577-6621 • e-mail: sales@wj.com • Web site: www.wj.com

Page 2 of 4 April 2007

CV110-1A

Cellular-band High Linearity Downconverter

Device Architecture / Application Circuit Information

Typical Downconverter Performance Chain Analysis

Cumulative Performance

Stage

Gain

(dB)

Output

P1dB

(dBm)

Output

IP3

(dBm)

NF

(dB)

Current

(mA)

Gain

(dB)

Output

P1dB

(dBm)

Output

IP3

(dBm)

NF

(dB)

RF Amplifier

13.5

21

40.0

3.5

150

13.5

21.0

40.0

3.5

RF Filter

-1.5

---

---

1.5

---

12.0

19.5

38.5

3.5

MMIC Mixer

-9.0

8

23.0

9.8

60

3.0

6.1

22.1

4.5

IF Amplifier

19.0

22

39.1

2.5

150

22.0

20.3

37.0

5.0

CV110-1A

Cumulative Performance

360

22.0

20.3

37.0

5.0

CV110-1A: The application circuit can be broken up into four main

functions as denoted in the colored dotted areas above: RF/IF diplexing

(purple), amplifier matching (green), filtering (red), and dc biasing

(blue). There are various placeholders for chip components in the circuit

schematic so that a common PCB can be used for all WJ single-branch

converters. Additional placeholders for other optional functions such as

filtering are also included.

RF / IF Amplifier Matching:

The RF amplifier requires a shunt

matching element for optimal gain and input return loss performance.

The IF amplifier requires matching elements to optimize the

performance of the amplifier to the desired IF center frequency. Since

IF bandwidths are typically on the order of 5 to 10%, a simple two

element matching network, in the form of either a high-pass or low-pass

filter structure, is sufficient to match the MMIC IF amplifier over these

narrow bandwidths.

Proper component values for other IF center

frequencies

can

be

provided

by

emailing

to

applications.engineering@wj.com.

the image frequencies and achieve the best noise figure performance

with the downconverter. The bandpass filter, implemented with a SAW

filter on the application circuit, allows for the suppression of noise from

the image frequency. It is permissible to not use a filter and use a 2 dB

pad with R6, R7, and R16 instead with slightly degraded noise figure

performance. Standard WJ evaluation boards will have the 2 dB pad in

place.

signal impinges on the switching elements of the mixer; the interaction

with these switches produces a signal at the IF frequency. The two

signals (RF and IF) are directed to the appropriate ports by the external

diplexer. A four-element diplexer is used in the circuit implementation

(L8 and C2 are not used). Pin 5 contains the IF signal and allows the

signal to be transferred to pin 25 for the convenience of PCB layouts.

DC biasing:

DC bias must be provided for the RF, LO and IF

amplifiers in the converter. R1 sets the operating current for the last

stage of the LO amplifier and is chosen to optimize the mixer LO drive

level. Proper RF chokes and bypass capacitors are chosen for proper

amplifier biasing at the intended frequency of operation. The “+5 V” dc

bias should be supplied directly from a voltage regulator.

IF Amplifier Matching

Frequency (MHz)

40

50

75

100

125

130

L7 (nH)

470

430

150

150

120

120

C17 (pF)

24

15

22

10

8.2

6.8

R8 (ohms)

4.7

4.7

3.3

2.2

2.2

2.2

L4 (nH)

470

240

330

330

330

330

1

2

3

4

5

6

7

21

20

19

18

17

16

15

28

27

26

25

24

23

22

8

9

10

11

12

13

14

IF Amp

RF Amp

LO Driver Amp

IF OUT

GND

N/C

GND

BIAS

GND

LO IN

RF OUT

GND

N/C

GND

IF THRU

GND

RF/IF

RF/IF

IF Feedthru

Path

LO

Printed Circuit Board Material:

.014” FR-4, 4 layers, .062” total thickness

RF Amp Bias

IF Amp Bias

LO Amp Bias

LO Amp Bias

RF Bandpass Filter /

Attenuator Pad

RF Amp Matching

IF Amp Matching

RF / IF Diplexer

(used for cellular versions only)