MICRF002 Просмотр технического описания (PDF) - Micrel

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MICRF002

300-440MHz QwikRadio® ASK Receiver

Micrel 

Micrel, Inc.

MICRF002/RF022

Functional Diagram

CAGC

CAGC

ANT

VDD

VSS

RF

Amp

fRX

fLO

fIF IF

Amp

Synthesizer

5th Order

Band-Pass Filter

430kHz

IF

Amp

AGC

Control

Peak

Detector

2nd Order

Programmable

Low-Pass Filter

Switched-

Capacitor

Resistor

RSC

Compa-

rator

UHF Downconverter

OOK Demodulator

DO

CTH

CTH

SEL0

SEL1

SWEN

SHUT

REFOSC

fT

Cystal

or

Ceramic

Resonator

MICRF002

Control

Logic

Reference

Oscillator

Reference and Control

Figure 1. MICRF002 Block Diagram

Resettable

Counter

Wakeup

WAKEB

Application Information and Functional

Description

Refer to Figure 1 “MICRF002 Block Diagram”. Identified in

the block diagram are the four sections of the IC: UHF

Downconverter, OOK Demodulator, Reference and

Control, and Wakeup. Also shown in the figure are two

capacitors (CTH, CAGC) and one timing component,

usually a crystal or ceramic resonator. With the exception

of a supply decoupling capacitor, and antenna impedance

matching network, these are the only external components

needed by the MICRF002 to assemble a complete UHF

receiver.

For optimal performance is highly recommended that the

MICRF002 is impedance matched to the antenna, the

matching network will add an additional two or three

components.

Four control inputs are shown in the block diagram: SEL0,

SEL1, SWEN, and SHUT. Using these logic inputs, the

user can control the operating mode and selectable

features of the IC. These inputs are CMOS compatible, and

are internally pulled-up. IF Bandpass Filter Roll-off

response of the IF Filter is 5th order, while the demodulator

data filter exhibits a 2nd order response.

July 2008

Design Steps

The following steps are the basic design steps for using the

MICRF002 receiver:

1. Select the operating mode (sweep or fixed)

2. Select the reference oscillator

3. Select the CTH capacitor

4. Select the CAGC capacitor

5. Select the demodulator filter bandwidth

Step 1: Selecting the Operating Mode

Fixed-Mode Operation

For applications where the transmit frequency is accurately

set (that is, applications where a SAW or crystal-based

transmitter is used) the MICRF002 may be configured as a

standard superheterodyne receiver (fixed mode). In fixed-

mode operation the RF bandwidth is narrower making the

receiver less susceptible to interfering signals. Fixed mode

is selected by connecting SWEN to ground.

Sweep-Mode Operation

When used in conjunction with low-cost L-C transmitters

the MICRF002 should be configured in sweep-mode. In

sweep-mode, while the topology is still superheterodyne,

the LO (local oscillator) is swept over a range of

frequencies at rates greater than the data rate. This

technique effectively increases the RF bandwidth of the

7

M9999-070808

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