ADF4206BRUZ-R7 datasheet(20/24 Pages) AD

20 / 24 page

ADF4206/ADF4208

Rev. A | Page 20 of 24

APPLICATIONS SECTION

LOCAL OSCILLATOR FOR GSM HANDSET

RECEIVER

Figure 33 shows the ADF4208 used in a classic superheterodyne

receiver to provide the required local oscillators (LOs).

In this circuit, the reference input signal is applied to the circuit

at OSCIN and is generated by a 10 MHz crystal oscillator. This is

a low cost solution. For better performance over temperature, a

TCXO (temperature controlled crystal oscillator) can be used

instead.

To have a channel spacing of 200 kHz (the GSM standard),

the reference input must be divided by 50 using the on-chip

reference counter.

The RF output frequency range is 1050 MHz to 1086 MHz. Loop

filter component values are chosen so that the loop bandwidth is

20 kHz. The synthesizer is set up for a charge pump current of

4.375 mA and the VCO sensitivity is 15.6 MHz/V.

The IF output is fixed at 125 MHz. The IF loop bandwidth is

chosen to be 20 kHz with a channel spacing of 200 kHz. Loop

filter component values are chosen accordingly.

OSCOUT

MUXOUT

ADF4208

VP2

VDD2 VDD1VP1

CPRF1

RF2IN

RF1IN

OSCIN

CLK

DATA

DECOUPLING CAPACITORS (22µF/10pF) ON VDD, VP OF

THE ADF4208, AND ON VCC OF THE VCOs HAVE BEEN

OMITTED FROM THE DIAGRAM TO AID CLARITY.

VCO190-125T

VCC

CPRF2

VCC

100pF

18Ω

100pF

IFOUT

100pF

51Ω

30pF

10MHz

18kΩ

1.3nF

13nF

2.7kΩ

620pF

3.3kΩ

VDD

100pF

18Ω

RFOUT

100pF 18Ω

18Ω

100pF

51Ω

LOCK DETECT

30pF

VCO190-1068U

Figure 32. GSM Handset Receiver Local Oscillator Using the ADF4208

ADF4206BRUZ-R7 Datasheet(PDF) 20 Page - Analog Devices

ADF4206BRUZ-R7 Datasheet(HTML) 20 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Datasheet Download

Link URL