ADF4602BCPZ datasheet(19/36 Pages) AD

19 / 36 page

ADF4602

Rev. 0 | Page 19 of 36

GAIN CONTROL

HIGH BAND LNA 1

HIGH BAND LNA 2

LOW BAND LNA

RxGAIN[6:0]

VCMSEL

RxEN[1:0]

LNA

ACTIVE FILTER CHANGES

MIXER

TRANSCONDUCTANCE

0dB TO 18dB

3 × 6dB STEPS

VGA

–6dB TO +18dB

24 × 1dB STEPS

0dB TO 18dB

3 × 6dB STEPS

0dB TO 18dB

3 × 6dB STEPS

18dB TO 30dB (WCDMA)

27dB TO 39dB (CDMA)

2 × 6dB STEPS

RXHB2RF

RXBBI

RXBBIB

RXBBQ

RXBBQB

RXHB1RF

RXLBRF

LPF

BPF

DAC

RXBW_TOGGLE

ADC

LPF

PROGRAMMABLE OFFSET

CONTROL

÷2 OR

÷4

Figure 37. Receiver Block Diagram

LNAs

The ADF4602 contains three tunable RF front ends suitable for

all major 3GPP frequency bands. Two are suitable for high band

operation in the region 1700 MHz to 2170 MHz. One is suitable

for operation from 824 MHz to 960 MHz. Thus, the three

integrated LNAs offer the designer the opportunity to create

multiband and regional specific variants with no additional

components.

LNA power control and internal band switching is fully

controlled by the serial interface.

The ADF4602 LNAs are designed for 50 Ω single-ended inputs,

thus further simplifying the front-end design and providing

easy matching with minimal components. Typically, a two-

component match is required: a series and shunt inductor.

Within the LNA, the signal is converted to a differential path

for signal processing in subsequent blocks within the receive

signal chain.

Interstage RF filtering is fully integrated, ensuring that external

out-of-band blockers are suitably attenuated prior to the mixer

stages. The LNA characteristic is designed to provide additional

filtering at the transmitter frequency offset.

The LNAs are enabled by programming bits rxbs[1:0] in

operation, and HB2 should be used for UMTS Band 2 operation.

Mixers

High linearity quadrature mixer circuits are used to convert the

RF signal to baseband in-phase and quadrature components.

Although not shown in Figure 37, two mixer sections exist: one

optimized for the high band LNA outputs and one optimized

for the low band. The high band and low band mixer outputs

are combined and then driven directly into the first stage of the

baseband low-pass filter, which also acts to reduce the level of

the largest blocking signals, prior to baseband amplification.

Quadrature drive is provided to the mixers from the receiver

synthesizer section by the VCO transport system, which includes

a programmable divider, so that the same VCO is used for both

high and low bands. Excellent 90° quadrature phase and

amplitude match are achieved by careful design and layout of

the mixers and VCO transport circuits.

Baseband Section

The ADF4602 baseband section is a distributed gain and filter

function designed to provide a maximum of 54 dB gain with

60 dB gain control range. Through careful design, pass band

ripple, group delay, signal loss, and power consumption are

kept to a minimum. Filter calibration is performed during the

manufacturing process, resulting in a high degree of accuracy

and ease of use.

Three baseband filters are available on the ADF4602, as shown

in Table 5. Bits rxbw_toggle[2:0] are used to select the mode of

operation. The seventh order WCDMA filter with 1.92 MHz

cutoff ensures that good attenuation of the adjacent channel should

be used to meet blocking/adjacent channel selection specifications

in femtocell applications. The GSM filter has a 100 kHz cut-off

and is intended for use as a monitoring receiver in a home base

station. The fifth order WCDMA filter provides less attenuation

of the adjacent channel, so it should not be used in femtocell

applications.

The I and Q channels can be internally swapped, thus allowing

optimum PCB routing between radio and analog baseband.

This is achieved using the swapi and swapq bits.

Table 5. Receive Baseband Filter Modes

Mode

Filter Cutoff Frequency (fC)

Seventh Order WCDMA

1.92 MHz

Fifth Order WCDMA

1.92 MHz

GSM

100 kHz

ADF4602BCPZ Datasheet(PDF) 19 Page - Analog Devices

ADF4602BCPZ Datasheet(HTML) 19 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 25 26 27 28 29 30 31 32 33 34 35 36

Datasheet Download

Link URL