Lesson 28 Electronic Signal Sources.ppt
- 1. Lesson 28 Signal Sources Unit 10 Electronic Instruments & Measurements
- 2. 25/2/3 2 Lesson 28 Signal Sources • Backgrounds • Text tour • Language in use – Vocabulary
- 3. 25/2/3 3 • Terminology – Oscilloscope – An oscilloscope, previously called an oscillograph, and informally known as a scope or o-scope, CRO (for cathode-ray oscilloscope), or DSO (for the more modern digital storage oscilloscope), is a type of electronic test instrument that allows observation of varying signal voltages, usually as a two- dimensional plot of one or more signals as a function of time. – Other signals (such as sound or vibration) can be converted to voltages and displayed. Backgrounds
- 4. Logic analyzer A logic analyzer is an electronic instrument that captures and displays multiple signals from a digital system or digital circuit. A logic analyzer may convert the captured data into timing diagrams, protocol decodes, state machine traces, assembly language, or may correlate assembly with source-level software. 25/2/3 4
- 5. Troubleshooting • Troubleshooting is a form of problem solving, often applied to repair failed products or processes. It is a logical, systematic search for the source of a problem in order to solve it, and make the product or process operational again. • Troubleshooting is needed to identify the symptoms. Determining the most likely cause is a process of elimination—eliminating potential causes of a problem. 25/2/3 5
- 6. DMM: Digital Multimeter • A multimeter or a multitester, also known as a VOM (volt- ohm-milliammeter), is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage, current, and resistance. 25/2/3 6
- 7. 25/2/3 7 • Arbitrary waveform Generator – An arbitrary waveform generator (AWG) is a piece of electronic test equipment used to generate electrical waveforms. These waveforms can be either repetitive or single-shot (once only) in which case some kind of triggering source is required (internal or external). • AFG:Arbitrary Function Generator – A function generator is usually a piece of electronic test equipment or software used to generate different types of electrical waveforms over a wide range of frequencies.
- 8. 25/2/3 8 Text tour • Outline – The Complete Measurement System – What is a Signal Source? – Types of Digital Signal Sources – Signal Generation Techniques – Basic Signal Source Applications – Signal Source Hardware Architecture: The Arbitrary Waveform Generator
- 9. 25/2/3 9 The Complete Measurement System • An acquisition instrument (use to locate) – an oscilloscope – a logic analyser • A stimulus instrument (use to detect the changes) – The signal source or signal generator, is the stimulus The signal source or signal generator, is the stimulus source source that pairs with an acquisition instrument to that pairs with an acquisition instrument to create the two elements of a complete measurement create the two elements of a complete measurement solution. solution.
- 10. 25/2/3 10 What is a Signal Source? • A signal source is nothing less than the cornerstone of almost any instrumentation setup used in hardware design, debug, or evaluation projects . – It is a key engineering tool. – It is an essential troubleshooting aid for the technician. – It is a surrogate for an automotive ignition pulse, a heart pacemaker, or a guided missile’s gyro output. – Second only to the global DMM, signal sources are perhaps the most universal class of electronic test instruments . An ignition system generates a spark or heats an electrode to a high temperature to ignite/combust a fuel-air mixture in spark ignition internal combustion engines oil-fired and gas- fired boilers, rocket engines, etc.
- 11. 25/2/3 11 Types of Digital Signal Sources • AWG: AWG can produce any waveform you can imagine. You can use a variety of methods - from mathematical formulae to “drawing” the waveform - to create the needed output.
- 12. 25/2/3 12 Types of Digital Signal Sources • AFG: Typically this instrument offers fewer waveform variations, but with excellent stability and fast response to frequency changes. If the UUT requires the classic “sine and square” waveforms and the ability to switch almost instantly between two frequencies, the AFG is the right tool. An additional virtue is the AFG’s low cost, which makes it very attractive for applications that do not require an AWG’s versatility. * UUT: Unit Under Test
- 13. 25/2/3 13 Types of Digital Signal Sources • DG (Data/Pattern Generators): This third type of signal source meets the special stimulus needs of digital devices that require long, continuous streams of binary data, with specific information content and timing characteristics.
- 14. 25/2/3 14 Signal Generation Techniques • Simulation: “Building” an event or sequence of events, based on a specific waveform definition (often from a simulator or a library of waveforms) • Replication: Capturing an existing signal on an oscilloscope and sending it to the signal source for reproduction • Substitution: Creating and/or modifying a defined signal to substitute for a signal from unavailable circuitry
- 15. 25/2/3 15 Signal Generation Techniques Figure 10.1 Signal sources can use standard, user-created, or captured waveforms, adding impairments where necessary for special test applications GPIB = General Purpose Interface Bus
- 16. 25/2/3 16 Basic Signal Source Applications Verification • Analyzing Digital Modulation Wireless equipment designers developing new transmitter and receiver hardware must simulate baseband I&Q signals– with and without impairments/defect–to verify conformance/standard with emerging and proprietary wireless standards. Some high-performance arbitrary waveform generators can provide the needed low-distortion, high-resolution signals at rates up to 1 gigabit per second (1 Gbps), with two independent channels, one for the“I”phase and one for the“Q”phase.
- 17. 25/2/3 17 Basic Signal Source Applications characterization • Testing D/A and A/D Converters Newly-developed digital-to-analog converters (DAC) and analog-to-digital converters (ADC) must be exhaustively tested to determine their limits of linearity, monotonicity, and distortion. A state-of-the-art AWG can generate simultaneous, in-phase analog and digital signals to drive such devices at speeds up to 1 Gbps.
- 18. 25/2/3 18 Basic Signal Source Applications stress/margin test • Stressing Communication Receivers Engineers working with serial data stream architectures need to stress their devices with impairments, particularly jitter and timing violations. Advanced signal sources save the engineer untold hours of calculation by providing efficient built-in jitter editing and generation tools. These instruments can shift critical signal edges as little as 0.3 ps.
- 19. 25/2/3 19 Signal Source Hardware Architecture The Arbitrary Waveform Generator • Fundamentally, an AWG is a sophisticated “playback” system that delivers waveforms based on stored digital data that describes constantly changing voltage levels of AC signal. • Digital sampling • A simplified block diagram of an AWG
- 20. 25/2/3 20 Signal Source Hardware Architecture The Arbitrary Waveform Generator Figure 10.2: AWGs use stored digital samples to construct a waveform.
- 21. 25/2/3 21 Signal Source Hardware Architecture The Arbitrary Waveform Generator Figure 10.3 AWG block diagram (simplified)
- 22. AWG Advantages • More cycles of the desired waveform can be stored – minimize number of endpoints (last memory location). • More waveform detail can be stored – to store edges and transients of high frequency complex waveforms & reproduce complex RF waveforms. 25/2/3 22
- 23. 25/2/3 23 • Vocabulary – Acquisition stimulus margin evaluation ancillary brief Language in use
- 25. 25/2/3 25 Acquisition in dictionary • The act of acquiring. e.g. an asset bought or obtained • Something acquired, especially an addition to an established category or group. • The process of locating a satellite, guided missile, or moving target so that its track or orbit can be determined.
- 26. 25/2/3 26 Acquisition in text • An acquisition instrument – usually an oscilloscope or logic analyser–is probably the first thing that comes to mind when you think about making electronic measurements.
- 27. 25/2/3 27 Acquisition in use • aircraft target acquisition • high-speed data acquisition • language acquisition • technique acquisition
- 28. 25/2/3 28 Stimulus in dictionary • Detectable change in the internal or external environment. • Something causing or regarded as causing a response. • An agent, an action, or a condition that elicits or accelerates a physiological or psychological activity or response.
- 29. 25/2/3 29 Stimulus in text • The toolset for digital design characterization differs from its counterpart in analog/mixed signal design, but both must include stimulus instruments and acquisition instruments. The signal source, or signal generator, is the stimulus source that pairs with an acquisition instrument to create the two elements of a complete measurement solution.
- 30. 25/2/3 30 Stimulus in use • under the stimulus of this hope • Light is a stimulus to growth in plants.
- 31. 25/2/3 31 Margin in dictionary • An edge and the area immediately adjacent to it; a border. • The blank space bordering the written or printed area on a page. • A limit in a condition or process, beyond or below which something is no longer possible or acceptable: – the margin of reality – has crossed the margin of civilized behavior.
- 32. 25/2/3 32 Margin in text • To cite another example, engineers must characterize their emerging designs to ensure that the new hardware meets design specifications across the full range of operation and beyond. This is known as margin or limit testing.
- 33. 25/2/3 33 Margin in use • low level noise margin • magnitude margin • noise margin • nominal margin • peak margin
- 34. 25/2/3 34 Evaluation in dictionary • A process to determine whether or not an item of hardware or software can perform a particular required function or to determine which of two or more items can perform the function best. • A process to reduce an expression to its simplest form or a single value.
- 35. 25/2/3 35 Evaluation in text • A signal source is nothing less than the cornerstone of almost any instrumentation setup used in hardware design, debug, or evaluation projects
- 36. 25/2/3 36 Evaluation in use • accomplishment evaluation • hazard evaluation • loss evaluation • evaluation of determinants
- 37. 25/2/3 37 Ancillary in dictionary • Subordinate: • Auxiliary; helping: • Something, such as a workbook, that is subordinate to something else, such as a textbook.
- 38. 25/2/3 38 Ancillary in text • It can be very difficult to design an instrumentation-quality signal generator, and of course, the time spent designing ancillary test equipment is a costly distraction from the project itself.
- 39. 25/2/3 39 Brief in dictionary • Short in time, duration, length, or extent. • Succinct; concise: • Curt; abrupt.
- 40. 25/2/3 40 Brief in text • Similarly, these fast AWGs with deep memory can generate very brief digital pulses and transients.
- 41. 25/2/3 41 Brief in use • in brief • make brief of • brief and to the point