QwikRadio

tm

5

June 1998

MICRF001

MICRF001

Micrel

Block Diagram

Functional Description

The block diagram illustrates the basic structure of the

MICRF001.

Identified in the figure are the three principal

functional blocks of the IC, namely (1) UHF Downconverter,

(2) OOK Demodulator, and (3) Reference and Control. Also

shown in the figure are two capacitors (CTH, CAGC) and

one timing component (CR), usually a ceramic resonator.

With the exception of a supply decoupling capacitor, these

are all the external components needed with the MICRF001

to construct a complete UHF receiver. Three control inputs

are shown in the block diagram, SEL0, SEL1 and SWEN.

Through these logic inputs the user can control the operating

mode and programmable functions of the IC. These inputs

are CMOS compatible, and are pulled-up on the IC.

The

inputs SEL0, SEL1 control the Demodulator filter bandwidth

in four binary steps from approximately 0.6kHz to 4.8kHz,

and the user must select the bandwidth appropriate to his

needs.

The SWEN pin allows the device to be configured in either its

normal (SWP) operating mode, or in standard (FIXED)

superheterodyne receiver mode. SWP operation is selected

when SWEN is HIGH, and is the default mode for the IC. An

example of SWP operation would be where the MICRF001

must operate with LC-based transmitters, whose transmit

frequency may vary up to

± 0.5% over initial tolerance, aging,

and temperature.

In this (patent-pending) mode, the LO

frequency is varied in a prescribed fashion which results in

downconversion of all signals in a band 2-3% around the

transmit frequency.

So the Transmitter may drift up to

±

0.5% without the need to retune the Receiver, and without

impacting system performance.

Such performance is not

achieved

with

currently

available

crystal-based

superheterodyne receivers, which can operate only with

SAW or crystal based transmitters.

[Note: A range penalty will occur in installations where there

exists a competing signal of sufficient strength in this small

frequency band of 2-3%. This penalty also exists with super-

regenerative type receivers, as their RF bandwidth is also

generally 2-3%. So any application for a super-regenerative

receiver is also an application for the MICRF001.]