MARCONI 6970 Ops 电路图.pdf
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1、Operating Manual i RF POWER METER 6970 IFR Ltd. 2000 No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, or recorded by any information storage or retrieval system, without permission in writing by IFR Ltd. Printed in t
2、he UK Manual part no. 46882-182 Issue 12 23 February 2000 RadioFans.CN 收音机爱 好者资料库 46882-182 App-A-1 Appendix A POWER MEASUREMENT ERROR ANALYSIS CONTENTS Page INTRODUCTION.A-1 ERROR SOURCES.A-1 Instrumentation Error.A-1 Mismatch Error.A-1 Power reference uncertainty .A-2 Calculating measurement uncer
3、tainty.A-2 Typical uncertainty calculations.A-3 INTRODUCTION The 6970 uses the customary technique of power measurement of a sensor element at the power source with a remote signal processing unit. By using a microcontroller and digital signal processing techniques, sensor correction, calibration an
4、d zeroing factors can be used to give the best enhancement of measurement accuracy. RF power measurements are never free from uncertainties. These can be due to instrumentation error, mismatch uncertainty and sensor calibration uncertainty. Significant measurement errors are possible unless these un
5、certainties are reduced to a minimum. ERROR SOURCES Instrumentation Error The instrumentation error comes from component tolerances and calibration uncertainty of the power meter. The total instrumentation accuracy of 6970 is typically 0.5 %. Mismatch Error Large uncertainties can arise from either
6、sensor or source mismatches. The first effect of these mismatches is to cause a transmission loss, i.e. the sensor does not receive the maximum available power from the source. The second effect is multiple reflections occurring between the source and the sensor causing unpredictable transmission lo
7、sses. RadioFans.CN 收音机爱 好者资料库 POWER MEASUREMENT ERROR ANALYSIS App-A-2 46882-182 Power reference uncertainty When the power reference is used to calibrate the power meter and the power sensor together, the accuracy of the reference oscillator becomes part of the overall measurement uncertainty. Calc
8、ulating measurement uncertainty For a source and load having complex reflection coefficients of S and L respectively, the ratio of transmitted power to maximum available power is as follows:- P PO SL SL L = 1 2 1 2 1 2 This has a maximum of: () 1 2 1 2 1 2 SL SL and a minimum of: () 1 2 1 2 1 2 + SL
9、 SL Uncertainty is usually quoted as a percentage uncertainty. From the previous formula:- Positive uncertainty () =+ 1001 2 1 SL % Negative uncertainty () = 1001 2 1 SL % The positive and negative uncertainties are essentially the same for low reflection coefficients, but as the reflection coeffici
10、ents increase the positive uncertainty increases more rapidly than the negative uncertainty. If the source and load matches are quoted as VSWRs then they may be converted to reflection coefficients by the following simple formula:- = + S S 1 1 where S is the VSWR If the reflection coefficients are s
11、mall, typically less than 0.15, the positive and negative uncertainties can be taken to be equal and the uncertainty can be approximated by:- Percentage uncertainty =200 SL RadioFans.CN 收音机爱 好者资料库 POWER MEASUREMENT ERROR ANALYSIS 46882-182 App-A-3 Typical uncertainty calculations (1) Calculate the m
12、ismatch uncertainty for a source reflection coefficient of 0.33 and a sensor reflection coefficient of 0.05. Positive uncertainty = 100 (1 + 0.33 0.05) 2 1) = 100 (1 + 0.0165) 2 1) = 100 (1.0333 1) = 3.33% Negative uncertainty = 100 (1 - 0.33 0.05) 2 1) = 100 (1 - 0.0165) 2 1) = 100 (0.9673 1) = 3.2
13、7% (2) Calculate the uncertainties for the source VSWR of 1.3:1 and a sensor VSWR of 1.05:1. The VSWRs must first be turned in to reflection coefficients. S = + = 1 3 1 1 3 1 0 3 2 3 0 130 . . . . . L = + = 1 05 1 1 05 1 0 05 2 05 0 024 . . . . . As both the source and sensor reflection coefficients
14、 are low we can apply the approximation formula described previously. Percentage uncertainty = 200 0.13 0.024 = 0.624% ii 46882-182 CONTENTS PRECAUTIONS Chapter 1 GENERAL INFORMATION Chapter 2 INSTALLATION Chapter 3 OPERATION Chapter 4 TECHNICAL DESCRIPTION Chapter 5 ACCEPTANCE TESTING Appendix A PO
15、WER MEASUREMENT ERROR ANALYSIS INDEX 46882-182 iii PRECAUTIONS WARNINGS, CAUTIONS and NOTES These terms have specific meanings in this manual: WARNINGS contain information to prevent personal injury. CAUTIONS contain information to prevent damage to the equipment. Notes contain important general inf
16、ormation. HAZARD SYMBOLS The meaning of hazard symbols appearing on the equipment is as follows: Symbol Nature of hazard Toxic hazard Class II supply Static sensitive component GENERAL CONDITIONS OF USE This product is designed and tested to comply with the requirements of IEC/EN61010-1 Safety requi
17、rements for electronic measuring apparatus, for Class III hand-held equipment and is for use in a pollution degree 2 environment. The equipment is designed to operate from an installation Category I supply. Equipment should be protected from the ingress of liquids and precipitation such as rain, sno
18、w, etc. When moving the instrument from a cold to a hot environment, it is important to allow the temperature of the instrument to stabilise before it is connected to the supply to avoid condensation forming. The instrument must only be operated within the environmental conditions specified in Chapt
19、er 1, Performance Data. This product is not approved for use in hazardous atmospheres or medical applications. If the equipment is to be used in a safety-related application, e.g. avionics or military applications, the suitability of the product must be assessed and approved for use by a competent p
20、erson. WARNING - TOXIC HAZARDS Some of the components used in this equipment may include resins and other materials which give off toxic fumes if incinerated. Take appropriate precautions, therefore, in the disposal of these items. iv 46882-182 WARNING - NICKEL CADMIUM A Nickel-cadmium battery is us
21、ed in this equipment. Do not crush or otherwise mutilate, as corrosive electrolyte can be released. Do not incinerate as they may explode or release toxic fumes. WARNING - POWER ADAPTER The supplied power adapter has been designed and tested in accordance with BS EN 60950 (IEC 950) Safety of informa
22、tion technology equipment, including electrical business equipment, and meets the SELV requirements of products with low voltage DC supply inputs. The adapter conforms with IEC safety Class II incorporating double insulation in its construction, and does not require a protective ground connection. N
23、o user serviceable parts are contained within the adapter and no attempt should be made to open the case. Where a supply lead is fitted to adapters incorporating an integrally fused plug ensure that the fuse rating is commensurate with the current requirements of the adapter. See under Performance d
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