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SIMPLE METHOD OF MONITORING RECEIVER PERFORMANCE

IP.com Disclosure Number: IPCOM000007626D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-10
Document File: 2 page(s) / 126K

Publishing Venue

Motorola

Related People

Simon Pike: AUTHOR

Abstract

Whenever a reliable radio communication sys- tem is required, it is important to be able to moni- tor the performance of all elements of the system, including the antennas and their feeders. For the transmitter, this may be easily accomplished by meas- uring the forward and reflected power to the trans- mitter antenna. However, for the receiver, there is no easy way of measuring the performance of the receiver without interrupting the communication.

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0 M M-ROLA

Technical Developments

SIMPLE METHOD OF MONITORING RECEIVER PERFORMANCE

by Simon Pike

because the field strength ofthe signal at the receiver antenna is not known. However, the aspect of receiver performance which is most important to monitor is the slow degradation of individual components in the receiver chain. Causes of slow degradation include:

-Ingress ofwater into feeders. -Corrosion of connectors, -Degradation ofamplifier performance.

  These will generally affect only one branch of a diversity receiver (or will affect both branches at dif- ferent rates). It is therefore possible to identify a deg- radation in the performance of a diversity receiver by monitoring the ratio of received signal power.

  It is possible for both branches of a receiver to fail simultaneously. However, a simultaneous fail- ure in both branches will probably be due to a cata- strophic failure of a common part of the receiver, such as a power supply, This can be detected by monitoring DC voltages and currents within the receiver, or by test routines in software. It is also necessary that the measurement of power ratio between the branches does not drifl; this will not happen if the power measurement occurs in the dig- ital domain, e.g. within the equalizer of a digital communication system.

INTRODUCTION

  Whenever a reliable radio communication sys- tem is required, it is important to be able to moni- tor the performance of all elements of the system, including the antennas and their feeders. For the transmitter, this may be easily accomplished by meas- uring the forward and reflected power to the trans- mitter antenna. However, for the receiver, there is no easy way of measuring the performance of the receiver without interrupting the communication.

  This paper proposes a simple way in which the performance of a receiver which uses diversity may be monitored, without requiring any extra hardware.

DIVERSITY RECEPTION

  In diversity reception, the receiver has two (or occasionally more) antenna inputs. There are three basic types ofdiversity reception:

1) Equal Ratio Combining; the signals from the antennas are summed and fed into a single receiver,

  2) Switched Combining; the power of the sig- nals received by each antenna is measured within the receiver, and the strongest is selected for demodulation.

  3) Maximal Ratio Combining; the receiver con- tains separate branches for each antenna, feeding a common demodulator. The demodulation process depends on the power ofthe signal in each branch.

  It is an inherent part of switched and maximal ratio combining that the power of the signal received by each branch is measured.

THE MEASUREMENT AVERAGING PERIOD

  In order to avoid false reporting of faults, the measurement of ratio of power must be averaged over a longer period than other causes of relative power variation. The most probable causes of rela- tive power variation at a base station of a cellular radio system are listed below:

  1) Raleigh F...