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PROGRAMMABLE PEAK DETECT FITTING

IP.com Disclosure Number: IPCOM000008984D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Jul-29
Document File: 4 page(s) / 123K

Motorola

Related People

Yuval Ben-Zion: AUTHOR [+3]

Abstract

In many applications, such as communication systems, the received analog signal is analyzed in order to determine its peak and its decision levels for converting it into digital signal.

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Page 1 of 4

@ MOTOROLA

Technical Developments

PROGRAMMABLE PEAK DETECT FITTING

by Yuval Ben-Zion, Moti Cohen and llan Zehngut

INTRODUCTION

In many applications, such as communication systems, the received analog signal is analyzed in order to determine its peak and its decision levels for converting it into digital signal.

Most of the circuits today derive the decision levels from the received signal peaks by dividing it with a constant. In tbis circuit the threshold levels are software controlled.

PROBLEM(S) TO BE SOLVED

Most of the circuits today derive the decision levels from the received signal peaks by dividing it with a constant.

In this way we get constant decision levels but there are problems with constant decision levels:

Using PWM technique allows setting the threshold levels in high resolution independent on the analog components precision.

l

l A very low cost implementation requiring only analog mux and few resistors.

Refer to Figure 1 on Page 113.

The circuit has 3 inputs and 2 outputs:

IN1 - The input Positive Peak.

IN2 - A square wave signal with progran- mable duty cycle.

IN3 - The input Negative Peak.

OUT1 - The fitted Positive Peak signal. OUT2 The fitted Negative Peak signal.

DETAILED DESCRIPTION

Refer to Figure 2 for circuit description.

When the PWM signal is in its high level the switch conducts and when the PWM signal is in its low level the switch is cut off.

As a result the R2 resistor is connected or dis- connected depending on the PWM signal.

When the PWM signal is at high logic level and R2 conducts, the following relations exist:

In systems where there are more than one type of modem, the decision levels are a compromise between the different types of modems (otherwise more hardware is needed).

l

l

When there is noise in the channel, the peak level of the received signal is higher and as a conse- quence the decision levels are higher in the presence of noise.

PROPOSED SOLUTION TO THE PROBLEM(S)

This application has the following advantages:

Vourl = Gain x (Vid - Vin2) + Vin2 ; VouR = Gain x (Vin2 - Vinl) + Vinl

The threshold levels are software controlled, eliminating the need...