900MHz Image-Reject Receiver

with Transmit Mixer

_______________________________________________________________________________________

9

17

16

15

18

19

21

1000pF

VARACTORS:

ALPHA SMV1299-004

OR EQUIVALENT

WHEN USING DIFFERENTIAL

SOURCE, REMOVE RESISTORS

AND REPLACE CAPACITORS WITH

SHORTS. FOR SINGLE-ENDED

SOURCE, DRIVE ONLY MODULATOR

AS SHOWN IN

TRANSMITTER SECTION.

RECEIVE IF OUTPUT (330

Ω)

27

23

26

3

20

22

1

28

RECEIVE

RF INPUT

TRANSMIT

RF OUTPUT

5

9

7

6

0.01

µF

47pF

0.1µF

2

47pF

47pF

0.1µF

8.2nH

12nH

22nH

18nH

47pF

47pF

47pF

8

11

0.01µF

47pF

0.01µF

VCO TANK COMPONENTS

FOR 915MHz RF FREQUENCY

47pF

14

0.01µF

47pF

RXIN

TXOUT

GND

GND

GND

CAP2

GND

CAP1

TXON

RXON

VCOON

DIV1

MOD

PREOUT

TXON

RXON

VCOON

DIV1

MOD

TO PLL

GND

RXOUT

100nH

GND

PREGND

47pF

24

25

VCO

ADJUST

C3

1k

47k

47pF

1k

C2

C26

R6

R7

10k

10k

L3

TANK

MODULATOR INPUT

12

0.01

µF*

TXIN

MODULATOR INPUT

13

0.01

µF*

TXIN

LNAGAIN

LNAGAIN

4

47pF

10

MAX2424

MAX2426

TANK

*

MAX2424

MAX2426

DEVICE

10

20

R6, R7

(

Ω)

2.0

4.0

C26

(pF)

6.8

3.3

L3

(nH)

3.3

8.0

C2, C3

(pF)

Figure 1. Typical Operating Circuit