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RF LOOPBACK CIRCUIT FACILITATES REMOTE BER TESTING OF BASE STATION

IP.com Disclosure Number: IPCOM000009072D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-06
Document File: 2 page(s) / 105K

Publishing Venue

Motorola

Related People

Bruce Barlow: AUTHOR [+2]

Abstract

A circuit architecture is presented to facilitate the remote testing of the collocated transmit and receive circuitry in a base station. The loopback circuitry is inactive during normal base station operation and can be activated when self-testing is required. Both bit error rate (BER) and packet error rate (PER) testing are possible with this cir- cuit architecture.

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MO7VROLA Technical Developments

RF LOOPBACK CIRCUIT FACILITATES REMOTE BER TESTING OF BASE STATION

by Bruce Barlow and Sean Mercer

  A circuit architecture is presented to facilitate the remote testing of the collocated transmit and receive circuitry in a base station. The loopback circuitry is inactive during normal base station operation and can be activated when self-testing is required. Both bit error rate (BER) and packet error rate (PER) testing are possible with this cir- cuit architecture.

INTRODUCTION

  A base station can include collocated transmitter and receiver circuitry. Remote evaluation of the base station hardware is desirable to minimize site visits by service personnel. This is possible with an RF loopback circuit where a sample of the transmit signal is translated to the receiver frequency, inject- ed to the receiver, decoded and then compared with the original transmitted signal. The results of a bit error rate (BER) test thus implemented can be con- veyed to the remotely located test personnel. No specialized test equipment is required to perform the loopback test.

SIMPLIFIED LOOPBACK ClRCUlT ARCHlTECTLRE

  The loopback circuit architecture will be described with reference to the block diagram shown in Figure 1. The embodiment in Figure 1 can be used to test a base station with two receivers used for diversity reception. The loopback circuit can, however, be used in applications where only a single receiver is deployed.

  The loopback circuit includes a switchable local oscillator. The loopback circuitry, including the local oscillator, would be turned off during normal operation of the base station. The loopback test would be invoked with the base station set 'to oper-

ate in a service mode. The local oscillator can be disabled during normal base station operation by turning off its DC power supply.

  The transmitter DSP chip sends a test data pat- tern to the RF modulator circuit. The signal is mod- ulated onto the transmitter carrier signal and ampli- fied by the RF power amplifier. The transmitter would usually be set to operate in a software con- trolled, low power transmit mode for the duration of the test. To test as much of the transmit chain as possible...