The Crest Factor in DVB-T (OFDM) Transmitter Systems and Its Influence on the Dimensioning of Power Components
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WILL the REAL MAXIMUM SPL PLEASE STAND UP? Measured Maximum SPL Vs Calculated Maximum SPL and How Not to Be Fooled
WILL THE REAL MAXIMUM SPL PLEASE STAND UP? Measured Maximum SPL vs Calculated Maximum SPL and how not to be fooled Introduction When purchasing powered loudspeakers, most customers compare three key specifications: price, power and maximum SPL. Unfortunately, this can be like comparing apples and oranges. For the Maximum SPL number in particular, each manufacturer often has its own way of reporting the specification. There are various methods a manufacturer can employ and each tends to choose the one that makes a particular product look the best. Unfortunately for the customer, this makes comparing two products on paper very difficult. In this document, Mackie will do the following to shed some light on this issue: • Compare and contrast two common ways of reporting the maximum SPL of a powered loudspeaker. • Conduct a case study comparing the Mackie HD series loudspeakers with similar models from a key competitor to illustrate these differences. • Provide common practices for the customer to follow, allowing them to see through the hype and help them choose the best loudspeaker for their specific needs. The two most common ways of reporting maximum SPL for a loudspeaker are a Calculated Maximum SPL and a Measured Maximum SPL. These names are given here to simplify comparison; other manufacturers may use different terminology. Calculated Maximum SPL The Calculated Maximum SPL is a purely theoretical specification. The manufacturer uses the known power of their amplifier and the known sensitivity of the transducer to mathematically calculate the maximum SPL they can produce in a particular loudspeaker. For example, a compression driver’s peak sensitivity may be 110 dB at 1W at 1 meter. -
Maintenance of Remote Communication Facility (Rcf)
ORDER rlll,, J MAINTENANCE OF REMOTE commucf~TIoN FACILITY (RCF) EQUIPMENTS OCTOBER 16, 1989 U.S. DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION AbMINISTRATION Distribution: Selected Airway Facilities Field Initiated By: ASM- 156 and Regional Offices, ZAF-600 10/16/89 6580.5 FOREWORD 1. PURPOSE. direction authorized by the Systems Maintenance Service. This handbook provides guidance and prescribes techni- Referenceslocated in the chapters of this handbook entitled cal standardsand tolerances,and proceduresapplicable to the Standardsand Tolerances,Periodic Maintenance, and Main- maintenance and inspection of remote communication tenance Procedures shall indicate to the user whether this facility (RCF) equipment. It also provides information on handbook and/or the equipment instruction books shall be special methodsand techniquesthat will enablemaintenance consulted for a particular standard,key inspection element or personnel to achieve optimum performancefrom the equip- performance parameter, performance check, maintenance ment. This information augmentsinformation available in in- task, or maintenanceprocedure. struction books and other handbooks, and complements b. Order 6032.1A, Modifications to Ground Facilities, Order 6000.15A, General Maintenance Handbook for Air- Systems,and Equipment in the National Airspace System, way Facilities. contains comprehensivepolicy and direction concerning the development, authorization, implementation, and recording 2. DISTRIBUTION. of modifications to facilities, systems,andequipment in com- This directive is distributed to selectedoffices and services missioned status. It supersedesall instructions published in within Washington headquarters,the FAA Technical Center, earlier editions of maintenance technical handbooksand re- the Mike Monroney Aeronautical Center, regional Airway lated directives . Facilities divisions, and Airway Facilities field offices having the following facilities/equipment: AFSS, ARTCC, ATCT, 6. FORMS LISTING. EARTS, FSS, MAPS, RAPCO, TRACO, IFST, RCAG, RCO, RTR, and SSO. -
Frequency Based Fatigue
Frequency Based Fatigue Professor Darrell F. Socie Mechanical Engineering University of Illinois at Urbana-Champaign © 2001 Darrell Socie, All Rights Reserved Deterministic versus Random Deterministic – from past measurements the future position of a satellite can be predicted with reasonable accuracy Random – from past measurements the future position of a car can only be described in terms of probability and statistical averages AAR Seminar © 2001 Darrell Socie, All Rights Reserved 1 of 57 Time Domain Bracket.sif-Strain_c56 750 Strain (ustrain) -750 Time (Secs) AAR Seminar © 2001 Darrell Socie, All Rights Reserved 2 of 57 Frequency Domain ap_000.sif-Strain_b43 102 101 100 Strain (ustrain) 10-1 0 20 40 60 80 100 120 140 Frequency (Hz) AAR Seminar © 2001 Darrell Socie, All Rights Reserved 3 of 57 Statistics of Time Histories ! Mean or Expected Value ! Variance / Standard Deviation ! Coefficient of Variation ! Root Mean Square ! Kurtosis ! Skewness ! Crest Factor ! Irregularity Factor AAR Seminar © 2001 Darrell Socie, All Rights Reserved 4 of 57 Mean or Expected Value Central tendency of the data N ∑ x i = Mean = µ = x = E()X = i 1 x N AAR Seminar © 2001 Darrell Socie, All Rights Reserved 5 of 57 Variance / Standard Deviation Dispersion of the data N − 2 ∑( xi x ) Var()X = i =1 N Standard deviation σ = x Var( X ) AAR Seminar © 2001 Darrell Socie, All Rights Reserved 6 of 57 Coefficient of Variation σ COV = x µ x Useful to compare different dispersions µ =10 µ = 100 σ =1 σ =10 COV = 0.1 COV = 0.1 AAR Seminar © 2001 Darrell Socie, All Rights Reserved 7 of 57 Root Mean Square N 2 ∑ x i = RMS = i 1 N The rms is equal to the standard deviation when the mean is 0 AAR Seminar © 2001 Darrell Socie, All Rights Reserved 8 of 57 Skewness Skewness is a measure of the asymmetry of the data around the sample mean. -
Sound Quality of Audio Systems
Acoustical Measurement of Sound System Equipment according IEC 60268-21 符合IEC 60268-21的音響系統聲學測量設備 KLIPPEL- live a series of webinars presented by Wolfgang Klippel KLIPPEL-live #5: Maximum SPL – a number becomes important , 1 Previous Sessions 1. Modern audio equipment needs output based testing 2. Standard acoustical tests performed in normal rooms 3. Drawing meaningful conclusions from 3D output measurement 4. Simulated standard condition at an evaluation point 5. Maximum SPL – giving this value meaning 6. Selecting measurements with high diagnostic value 7. Amplitude Compression – less output at higher amplitudes 8. Harmonic Distortion Measurements – best practice 9. Intermodulation Distortion – music is more than a single tone 10.Impulsive distortion - rub&buzz, abnormal behavior, defects 11.Benchmarking of audio products under standard conditions 12.Auralization of signal distortion – perceptual evaluation 13.Setting meaningful tolerances for signal distortion Acoustical14.testingRatingof a modernthe maximum active audio deviceSPL value for a product 1st Session15.2nd SessionSmart speaker testing with wireless audio input 3rd Session 4th Session KLIPPEL-live #5: Maximum SPL – a number becomes important , 2 Ask Klippel First Question: 在沒有復雜的測試箱或基於近場/遠場測量設置的測試箱的情況下,品檢上是否有一個好的解決方案。 Is there a good solution for on-line QC without complex testing box or testing chamber based on near field / far field measurement setting. Response WK: 否,對於傳感器和小型系統(例如智能手機),因為屏蔽環境噪聲非常有用。 NO, for transducers and small system (e.g. smart phones) because the shielding against ambient noise is very useful. 是的,較大的系統(條形音箱,專業設備,電視……)需要不同的解決方式 Yes, larger systems (sound bars, professional equipment, TVs …) need a different solution considering the following points: • 進行近場測量(與環境噪聲相比,SNR更高,SPL更高) Performing a near-field measurement (better SNR, higher SPL compared to ambient noise) • 在終端測試處使用圍繞測試站的吸收牆。 圍繞組裝線建造測試環境的最佳解決方案。 Using absorbing walls around the test station at the end of line. -
Citizens' Band (CB) Radio Spectrum Use – Information and Operation
Citizens’ Band Radio equipment– information and operation Citizens’ Band (CB) radio spectrum use – information and operation Of 364 Guidance Publication date: March 2018 Citizens’ Band Radio equipment– information and operation Contents Section Page 1 Regulatory and equipment information 1 2 Frequently asked questions 5 3 CB operating practice 8 Citizens’ Band Radio equipment– information and operation Section 1 Regulatory and equipment information Citizens’ Band (‘CB’) radio 1.1 Citizens’ Band (‘CB’) radio operates in the 27 MHz band. It is a short-range radio service for both hobby and business use. It is designed to be used without the need for technical qualifications. However, its use must not cause interference to other radio users. Consequently, only radios meeting certain specific requirements may be used. These are described below. How Ofcom authorises the use of CB radio 1.2 Ofcom seeks to reduce regulation, where possible. In 2006, we therefore made exemption regulations1, removing the need for a person to hold a licence to operate CB radio equipment using Angle Modulation (FM/PM). 1.3 In 2014, Ofcom made further exemption regulations2, which permitted the operation of CB radio equipment using two additional modes of Amplitude Modulation (AM) - Double Side Band (DSB) and Single Side Band (SSB). This followed an international agreement3 made in 2011.”. 1.4 CB users share spectrum in a frequency band used by the Ministry of Defence (MOD). CB users must therefore accept incoming interference caused by use of this spectrum by the MOD. 1.5 CB radio equipment must be operated on a 'non-interference’ basis. -
Recommendation ITU-R V.573-4
Rec. ITU-R V.573-5 1 RECOMMENDATION ITU-R V.573-5* Radiocommunication vocabulary (1978-1982-1986-1990-2000-2007) Scope This Recommendation provides the main vocabulary reference, giving synonymous terms in three languages and the associated definitions. It includes terms given in Article 1 of the Radio Regulations (RR) and extends the list to technical terms defined in texts of the ITU-R. The ITU Radiocommunication Assembly, considering a) that Article 1 of the Radio Regulations (RR) contains the definitions of terms for regulatory purposes; b) that the Radiocommunication Study Groups have a need to establish new and amended definitions for technical terms that do not appear in RR Article 1 or that are so defined as to be unsuitable for Radiocommunication Study Group purposes; c) that it would be desirable for some of these terms and definitions established by the Radiocommunication Study Groups to be more widely used within the ITU-R, recommends that the terms listed in RR Article 1 and in Annex 1 below should be used as far as possible with the meaning ascribed to them in the corresponding definition. NOTE 1 – Study Groups are invited, where there is a difficulty in using any of the terms with the meaning given in the corresponding definition, to forward to the Coordination Committee for Vocabulary (CCV) a proposal for revision or alternative application, accompanied by substantiating argument. NOTE 2 – A number of terms in this Recommendation appear also in RR Article 1 with a different definition. These terms are identified by (RR . ., MOD) or (RR . .(MOD)) if the modifications consist only of editorial changes. -
Amateur Radio Notes
Ham Radio – General Exam – Study Notes Frequency: 300/meter = MHz or 300/MHz = meters Dipole Antenna: ½ Wave dipole antennas = 468/Frequency Silicon – Seven letters = diode threshold of .07v Geranium – 3x3 letters = diode threshold of .03v NAND and ZERO both four letters QRQ = Quicker QRS = Slower QRV = ReceiVe CapACitors pass AC inDuCtors pass DC Fifteen amp fuse for Fourteen gauge wire Twenty amp fuse for Twelve gauge wire AC frequencies increases: – Coil springs higher (reactance increases) - Capacitor holds back (reactance decreases) AM – Product Detector Audio – Discriminator BFO – Product Detector Heterodyne receiver - Mixer Balanced Modulator + Mixer - Filter 20m Data band – 14.070 – 14.100 LC Oscillator – Tank Circuit CW Bandwidth = 150 Hz SBB Bandwidth = 2,300 Hz FM Bandwidth = +/- 5KHz or +/- 15 KHz Ohm’s Law: E/I*R Unit Measures Power Law: P/E*I Amp Current E – Voltage in Volts Farad Capacitance I – Current in Amps Henry Inductance R – Resistance in Ohms Hertz Frequency P – Power in Watts Ohm Resistance Series Parallel Watt Power Resistor Add Less Volt Voltage Inductor Add Less Capacitor Less Add Designation Frequency Wavelength ELF extremely low frequency 3Hz to 30Hz 100'000km to 10'000 km SLF superlow frequency 30Hz to 300Hz 10'000km to 1'000km ULF ultralow frequency 300Hz to 3000Hz 1'000km to 100km VLF very low frequency 3kHz to 30kHz 100km to 10km LF low frequency 30kHz to 300kHz 10km to 1km MF medium frequency 300kHz to 3000kHz 1km to 100m HF high frequency 3MHz to 30MHz 100m to 10m VHF very high frequency 30MHz to 300MHz -
Bachelor Thesis
BACHELOR THESIS Perceived Sound Quality of Dynamic Range Reduced and Loudness Normalized Popular Music Jakob Lalér Bachelor of Arts Audio Engineering Luleå University of Technology Department of Business, Administration, Technology and Social Sciences Perceived sound quality of dynamic range reduced and loudness normalized popular music Lalér Jakob Lalér Jakob 1 S0038F ABSTRACT The lack of a standardized method for controlling perceived loudness within the music industry has been a contributory cause to the level increases that emerged in popular music at the beginning of the 1990s. As a consequence, discussions about what constitutes sound quality have been raised. This paper investigates to what extent dynamic range reduction affects perceived sound quality of popular music when loudness normalized in accordance with ITU-R BS. 1770-2. The results show that perceived sound quality was not affected by as much as -9 dB of average gain reduction. Lalér Jakob 2 S0038F TABLE OF CONTENTS ABSTRACT...........................................................................................................................................2 INTRODUCTION...................................................................................................................................4 Aim, Objectives and Limitations............................................................................................................4 Background..........................................................................................................................................4 -
DC Input” the Original Way to Lay Down the Maximum Permitted Power Was in Terms of “DC Input” to the Final Stage
The G4EGQ RAE COURSE Lesson 13Pt2 Transmitter RF Measurements Moving on from “DC input” The original way to lay down the maximum permitted power was in terms of “DC input” to the final stage. This also made the assumption that the final valve or transistor would not exceed certain operating efficiencies (Class A 50%; Class B 66.6% and Class C 80%) The above transmitter is being operated at the “old fashioned limit” of 150 watts DC input. It is either a FM or CW (key down) transmitter. [FM= frequency modulated; CW = carrier wave (Morse)] More precise measurements can now be made using a calibrated oscilloscope. It shows the transmitter connected to a 100Ω dummy load. The oscilloscope is displaying the RF waveform by connecting it across the dummy load. The display shows the carrier wave. Being FM or CW (with the key held down) is has constant amplitude. The RF power out from the transmitter is 100 Watts. This results in 1 Amp flowing through the 100Ω dummy load resistor. The RF voltage across this dummy load, as indicated by the oscilloscope, is 100 volts. Amplitude modulation The 100 watt carrier is then fully amplitude modulated.(100%) by a sine wave audio tone. The resultant RF output is displayed on the oscilloscope. The radio frequency is very high compared with the audio frequency and the individual RF cycles may merge into each other on the screen and just appear as a green “modulation envelope”. The carrier now varies between zero and twice the amplitude of the original (unmodulated) carrier. -
A Review of Feature Extraction Methods in Vibration-Based Condition Monitoring and Its Application for Degradation Trend Estimation of Low-Speed Slew Bearing
machines Review A Review of Feature Extraction Methods in Vibration-Based Condition Monitoring and Its Application for Degradation Trend Estimation of Low-Speed Slew Bearing Wahyu Caesarendra 1,2 ID and Tegoeh Tjahjowidodo 3,* ID 1 Mechanical Engineering Department, Diponegoro University, Semarang 50275, Indonesia; [email protected] 2 School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia 3 School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore * Correspondence: [email protected] Received: 9 August 2017; Accepted: 19 September 2017; Published: 27 September 2017 Abstract: This paper presents an empirical study of feature extraction methods for the application of low-speed slew bearing condition monitoring. The aim of the study is to find the proper features that represent the degradation condition of slew bearing rotating at very low speed (≈1 r/min) with naturally defect. The literature study of existing research, related to feature extraction methods or algorithms in a wide range of applications such as vibration analysis, time series analysis and bio-medical signal processing, is discussed. Some features are applied in vibration slew bearing data acquired from laboratory tests. The selected features such as impulse factor, margin factor, approximate entropy and largest Lyapunov exponent (LLE) show obvious changes in bearing condition from normal condition to final failure. Keywords: vibration-based condition monitoring; feature extraction; low-speed slew bearing 1. Introduction Slew bearings are large roller element bearings that are used in heavy industries such as mining and steel milling. They are particularly used in turntables, cranes, cranes, rotatable trolleys, excavators, reclaimers, stackers, swing shovels and ladle cars [1]. -
Crest Factors of Complementary-Sequence-Based Multicode MC-CDMA Signals Byoung-Jo Choi and Lajos Hanzo
1114 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 2, NO. 6, NOVEMBER 2003 Crest Factors of Complementary-Sequence-Based Multicode MC-CDMA Signals Byoung-Jo Choi and Lajos Hanzo Abstract—The crest factor properties of binary phase-shift be bounded by 4 dB upon carefully selecting the code sets keying modulated two- and four-code assisted multicarrier and upon employing high-rate crest-factor reduction coding, code-division multiple-access (MC-CDMA) employing comple- provided that the number of simultaneously used codes is mentary-sequence-based spreading sequences are characterized. More specifically, a complementary-sequence pair, a comple- higher than or equal to four. When is less than four, the mentary-sequence-based subcomplementary code pair, and a MC-CDMA signals employing orthogonal Gold (OGold) Sivaswamy’s complementary code set are studied. It was found codes, Frank codes [8], and Zadoff–Chu codes [10], [11] that the corresponding crest factors are bounded by 3 dB, which resulted in considerably lower crest factors. Even though corresponds to the crest factor of a single sine wave. This low crest Zadoff–Chu codes indeed do produce an ideal crest factor of factor resulted in a lower power loss and a lower out-of-band power spectrum due to clipping when the time-domain signal was less than 3 dB in the context of single-code MC-CDMA, the subjected to a typical nonlinear power amplifier, in comparison to crest factor values of neither Zadoff–Chu codes, Frank codes, those of Walsh code and orthogonal Gold code-spread MC-CDMA nor those of OGold codes are bounded by 3 dB in the context of signals. -
An Efficient Hardware Implementation of the Peak Cancellation Crest Factor Reduction Algorithm
DEGREE PROJECT IN INFORMATION AND COMMUNICATION TECHNOLOGY, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2016 An efficient Hardware implementation of the Peak Cancellation Crest Factor Reduction Algorithm MATTEO BERNINI KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF INFORMATION AND COMMUNICATION TECHNOLOGY An efficient Hardware implementation of the Peak Cancellation Crest Factor Reduction Algorithm MATTEO BERNINI Master’s Thesis at KTH Information and Communication Technology Supervisor: Shafqat Ullah Examiner: Johnny Öberg TRITA-ICT-EX-2016:187 Abstract An important component of the cost of a radio base station comes from to the Power Am- plifier driving the array of antennas. The cost can be split in Capital and Operational expenditure, due to the high design and realization costs and low energy efficiency of the Power Amplifier respectively. Both these cost components are related to the Crest Factor of the input signal. In order to reduce both costs, it would be possible to lower the average power level of the transmitting signal, whereas in order to obtain a more efficient transmis- sion, a more energized signal would allow the receiver to better distinguish the message from the noise and interferences. These opposed needs motivate the research and development of solutions aiming at reducing the excursion of the signal without the need of sacrificing its average power level. One of the algorithms addressing this problem is the Peak Cancellation Crest Factor Reduction. This work documents the design of a hardware implementation of such method, targeting a possible future ASIC for Ericsson AB. SystemVerilog is the Hardware Description Language used for both the design and the verification of the project, together with a MATLAB model used for both exploring some design choices and to val- idate the design against the output of the simulation.