Browse Prior Art Database

PHASE COMPARATOR FOR THREE LEVEL DIRECT FM MODEM

IP.com Disclosure Number: IPCOM000008979D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Jul-29
Document File: 5 page(s) / 171K

Publishing Venue

Motorola

Related People

Ben Zion Yuval: AUTHOR [+3]

Abstract

This paper describes a Digital Phase comparator that is implemented by digital means and relies on all the information of the received signal to create accurate recovered clock phase adjustment.

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At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

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m MOTOROLA Technical Developments

PHASE COMPARATOR FOR THREE LEVEL DIRECT FM MODEM

by Ben Zion Yuval, llan Zehngut and Mordechay Cohen

ABSTRACT

  This paper describes a Digital Phase comparator that is implemented by digital means and relies on all the information of the received signal to create accurate recovered clock phase adjustment.

INTRODUCTION

  This paper describes a Digital Phase comparator that is implemented by digital means and which relies on all the information of the received signal to create accurate recovered clock phase adjustment.

THE PROBLEM TO BE SOLVED

  The problem to be solved is how to obtain accu- rate phase difference information from an analog received signal.

  Current known technology compares the recov- ered clock and received signal and gives an estimate, of or partial information, on the phase difference.

   The Phase Comparator described here gives accurate information, every clock cycle, about the phase difference between the received signal and the optimal Receive clock.

PROPOSED SOLUTION

  The Phase Comparator is implemented by digital technology, which takes into account any possible state of phase difference between the recovered clock and the received signal and gives as a result an accurate error detection signal, once every clock period. The Phase Comparator described here is used in a three level Direct FM Modem which is able to transmit/receive data via radio.

   The Direct FM modulator transmits a signal in which "0" is converted to maximum/minimum lev- els and "1" is converted,,to a middle level. The sig- nal is shaped to produCe a band-limited signal to accommodate radio link distortions.

  At the receiver side @e clock is recovered by uti- lizing maximum information about the clock embed- ded in the receive signal: This yields accurate infor- mation regarding the phase difference between the received signal and the ,ideal received clock every clock cycle.

IMPLEMENTATION

  The received analog signal (Rx) is converted into a digital signal (D) which can take two values. The conversion takes place according to the rule:

Peak +

(i) A signal level between -

and penk-

- is converted to '0'.

2

, (ii) A signal level above Fand below peak-is converted to '1'.

2

2

0 !"lotMo4 Inc. 1999 106 January 1999

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@ MOTOROLA

Technical Developments

Figure 1 describes the signals at the receiver side:

DD

CLK

-T-

Fig. 1

The received clock is recovered by a digital/analog PLL where the main part is the phase comparator. This arrangement is shown in Figure 2:

    D mhe receive.3 Digilnl signno

CLK <Th-loc*)

Fig. 2

107 January 1999

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0 M

MOTOROLA Technical Developments

The Phase Comparator is comprised of a counter which counts up to l/2 T, state macine.

  The combination of the s...