MICRF002BM データシートの表示（PDF） - Micrel

部品番号

コンポーネント説明

メーカー

MICRF002BM

300-440MHz QwikRadio™ASK Receiver

Micrel 

MICRF002/RF022

Functional Diagram

Micrel

CAGC

CAGC

ANT

VDD

VSS

RF

Amp

f RX

fLO

fIF IF

Amp

Programmable

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

Control

Logic

Resettable

Counter

WAKEB

REFOSC

Cystal

or

Ceramic

Resonator

fT

MICRF002

Reference

Oscillator

Reference and Control

Figure 1. MICRF002 Block Diagram

Wakeup

Applications 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 match-

ing 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.

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 in-

creases the RF bandwidth of the MICRF002, allowing the

device to operate in applications where significant transmit-

ter-receiver frequency misalignment may exist. The transmit

frequency may vary up to ±0.5% over initial tolerance, aging,

and temperature. In sweep-mode a band approximately

1.5% around the nominal transmit frequency is captured. The

transmitter may drift up to ±0.5% without the need to retune

the receiver and without impacting system performance.

The swept-LO technique does not affect the IF bandwidth,

therefore noise performance is not degraded relative to fixed

mode. The IF bandwidth is 430kHz whether the device is

operating in fixed or sweep-mode.

Due to limitations imposed by the LO sweeping process, the

upper limit on data rate in sweep mode is approximately

5.0kbps.

Similar performance is not currently available with crystal-

based superheterodyne receivers which can operate only

with SAW- or crystal-based transmitters.

March 2003

7

MICRF002/RF022

Share Link: