1.Oscilloscope. 2.Block diagram of Oscilloscope. 3.Types of Oscilloscope. 4.Applications of Oscilloscope. 5.Signal generator. 6. Types of signal generator. 7. Frequency synthesizer. 8.Analyzer. 9.Types of analyzer

1.Oscilloscope.
2.Block diagram of Oscilloscope.
3.Types of Oscilloscope.
4.Applications of Oscilloscope.
5.Signal generator.
6. Types of signal generator.
7. Frequency synthesizer.
8.Analyzer.
9.Types of analyzer

1. Outeline: 1.Oscilloscope. 2.Block diagram of Oscilloscope. 3.Types of Oscilloscope. 4.Applications of Oscilloscope. 5.Signal generator. 6. Types of signal generator. 7. Frequency synthesizer. 8.Analyzer. 9.Types of analyzer.

2. Oscilloscope An oscilloscope (usually called a scope) is a visual voltmeter with a timer(clock) that shows when a voltage changes. An analog scope uses a cathod ray tube(CRT) similar to a television screen to display voltage patterns. The oscilloscope depends on the movement of electron beam,which is then mode visible by allowing the beam to impinge on a phosphor surface, which produces a visible spot.

3. Basic block diagram of Oscilloscpe

4. The function of each block of CRO is mentioned below. Vertical Amplifier − It amplifies the input signal, which is to be displayed on the screen of CRT. Delay Line − It provides some amount of delay to the signal, which is obtained at the output of vertical amplifier. This delayed signal is then applied to vertical deflection plates of CRT. Trigger Circuit − It produces a triggering signal in order to synchronize both horizontal and vertical deflections of electron beam. Time base Generator − It produces a sawtooth signal, which is useful for horizontal deflection of electron beam. Horizontal Amplifier − It amplifies the sawtooth signal and then connects it to the horizontal deflection plates of CRT.

5. Power supply − It produces both high and low voltages. The negative high voltage and positive low voltage are applied to CRT and other circuits respectively. Cathode Ray Tube (CRT) − It is the major important block of CRO and mainly consists of four parts. Those are electron gun, vertical deflection plates, horizontal deflection plates and fluorescent screen. The electron beam, which is produced by an electron gun gets deflected in both vertical and horizontal directions by a pair of vertical deflection plates and a pair of horizontal deflection plates respectively. Finally, the deflected beam will appear as a spot on the fluorescent screen. In this way, CRO will display the applied input signal on the screen of CRT. So, we can analyse the signals in time domain by using CRO.

6. Types of Oscilloscope: There are some types of Oscilloscope: 1.Analog Oscilloscope. 2.Digital storage Oscilloscope. 3.Digital Phosphor Oscilloscope. 4.Digital Sampling Oscilloscope. Analog Oscilloscope : An analog oscilloscope directly displays the signal picked up by a probe and essentially trace it on the screen. Storage capabilities allow the waveform to be displayed for extended periods of type rather than decay immediately. Where analog oscilloscopes really come into their own is in dealing with analog signals and transient effects. Audio and analog video work are great fits for the capabilities of an analog oscilloscope which can also handle low-speed digital signals.

7. Digital storage oscilloscope: Digital storage oscilloscopes can capture transient events and store them for analysis, archival, printing, or other processing. They have permanent storage for recording signals and they can be offloaded to other media for storage and analysis on a computer. Digital storage oscilloscopes cannot display the level of intensity of a real-time signal, unlike an analog oscilloscope. Single shot events can be captured through the use of triggers which can be set manually or automatically depending on the oscilloscope. Digital storage oscilloscopes are the workhorses of real-world digital design where four or more signals are analyzed simultaneously.

8. Digital Phosphor Oscilloscope For higher speed digital signal capture and analysis, Digital phosphor oscilloscopes trump standard digital storage oscilloscopes. Digital phosphor oscilloscopes use a parallel processing ADC solution that delivers much higher sampling rates than traditional digital storage oscilloscopes. This sampling rate enables a signal visualization performance level that has the appearance of real-time. Digital phosphor oscilloscopes duplicate the effect of phosphorus by storing a database of the values of the repeating waveforms and increasing the intensity on the display where the waveforms overlap. Like an analog oscilloscope, a digital phosphor scope can reveal transients by displaying the intensity level, but it can still miss transients that happen outside of the data capture window and its update rate.

9. Digital sampling oscilloscope: Digital sampling oscilloscopes have a slightly different input technique that other oscilloscopes and trades off a much higher bandwidth for a lower dynamic range. The input is not attenuated or amplified so the oscilloscope must be able to handle the full range of the input signal, which is generally limited to about 1-volt peak-to-peak. Digital sampling oscilloscopes only work on repetitive signals and will not help capture transients beyond their normal sampling rate. On the other hand, digital sampling oscilloscopes can capture signals that are an order of magnitude faster than other types of oscilloscopes, with bandwidths exceeding 80 GHz.

10. Applications of Oscilloscope: 1.Dc voltage measurment. 2.Measurment of the voltage between two points on the waveform. 3.Elimination of undesired signal components. 4.Time measurment. 5.Time difference measurment. 6.Pulse width measurment. 7.Phase difference measurement. 8.Frequency measurment. 9.Relative mesurment. 10.Applications of X-Y operations.

11. Signal generator The signal generator is used to provide known test conditions for the performance evaluation of various electronic systems and for replacing missing signals in systems being analyzed for repair. Characteristics: 1. The frequency of the signal should be well known and stable. 2.The amplitude should be controllable from very small to relatively large values. 3.The signal should be free of distortion.

12. Types of signal generator: Looking at what a signal generator is, it will be seen that there are many different types of signal generator: Function generator. Pulse generator. Arbitrary waveform generator. Audio signal generator. RF signal generator. Vector signal generator.

13. Function Generator:

14. A frequency control network used here whose frequency is controlled by the variation in the magnitude of current. The current sources 1 and 2 drives the integrator.By using Function Generator, we can have a wide variety of waveforms whose frequency changes from 0.01 Hz to 100 KHz. The two current sources are regulated by the frequency controlled voltage. A constant current is supplied to the integrator by current supply source 1. Due to this, the voltage of the integrator rises linearly with respect to time. This linear rise is according to the output signal voltage equation:eq1 Any increase or decrease in the current will resultantly increase or decrease the slope of the voltage at the output and thus controls the frequency. The Voltage Comparator Multi-vibrator present here cause variation in the state of the integrator output voltage at a previously determined maximum level. Due to this change of state, the current supply from source 1 cuts off and switches to supply source 2. A reverse current is supplied to the integrator by current source 2. This reverse current cause drops in the output of integrator linearly with time. As before this time also, when the output attains a predetermined level, the comparator again changes its state and switches to current supply source 1. Thus we will have a triangular wave at the output of the integrator whose frequency depends on current by the supply sources as we can see in the block diagram shown above. A square wave signal is obtained at the output of the comparator. The resistance diode network employed in the circuit changes the slope of that triangular wave with distortion less than 1%. The output amplifier thus helps to provide two waves at the output simultaneously. This captured signal can be displayed by using an oscilloscope.

15. Pulse generator: As the name suggests, the pulse generator is a form of signal generator that creates pulses. These signal generators are often in the form of logic pulse generators that can produce pulses with variable delays and some even offer variable rise and fall times. Pulses are often needed when testing various digital, and sometimes analogue circuits. The ability to generate pulses enables circuits to be triggered, or pulses trains to be sent to a device to provide the required stimulus.

16. Arbitrary waveform generator: The arbitrary waveform generator is a type of signal generator that creates very sophisticated waveforms that can be specified by the user. These waveforms can be almost any shape and can be entered in a variety of ways, even extending to specifying points on the waveform. Essentially an arbitrary waveform generator can be thought of as a very sophisticated function generator. Being considerably more complex, arbitrary waveform generators are more expensive than function generators, and often their bandwidth is more limited because of the techniques required in generating the signals. Audio signal generator: As the name implies this type of signal generator is used for audio applications. Signal generators such as these run over the audio range, typically from about 20 Hz to 20 kHz and more, and are often used as sine wave generators. They are often used in audio measurements of frequency response and for distortion measurements. As a result they must have a very flat response and also very low levels of harmonic distortion.

17. RF signal generator: An RF signal generator may use a variety of methods to generate the signal. Analogue signal generator types used free running oscillators, although some used frequency locked loop techniques to improve stability. However most RF signal generators use frequency synthesizers to provide the stability and accuracy needed. Both phase locked loop and direct digital synthesis techniques may be used. The RF signal generators often have the capability to add modulation to the waveform. Lower end ones may be able to add AM or FM, but high end RF signal generators may be able to add modulation formats OFDM, CDMA, etc . . so they can be used for testing cellular and wireless systems.

18. Vector signal generator: The vector signal generator is a type of RF signal generator that generates RF signals with complex modulation formats such as QPSK, QAM, etc. Vector signal generators tend to be used for the testing of modern data communications systems, everything from Wi-Fi to 4G, 5G mobile telecommunications systems and many other connectivity solutions that used advanced waveforms. As these waveforms use modulation schemes and waveforms that use phase information, a vector signal generator is often needed.

19. Frequency synthesizer A frequency synthesizer is an electronic circuit that generates a range of frequencies from a single reference frequency. Frequency synthesizers are used in many modern devices such as radio receivers, televisions, mobile telephones, radiotelephones, walkie-talkies, CB radios, cable television converter boxes satellite receivers, and GPS systems. Frequency synthesized signal generator: The phase-locked loop(indirect method) makes the frequency correction based on a fase measurement.Five main component: 1. The VCO or voltage controlled oscillator. 2.The programmable divider. 3.The phase detector. 4.The phase reference. 5.The loop filter.

20. Voltage controlled oscillator: The source of the output frequency and has the ability to be tuned electronically; usually by applying a variable voltage. For a phase-locked-loop frequency synthesizer the signal source will be considered a voltage controlled device. The programmable divider: A logic element that divides the frequency of VCO by an integer that can be entered via programming switches, a microprocessor, or other method. The phase detector: Provides an analog output that is a function of the phase angle between the two inputs, which in case of a frequency synthesizer is the reference source and the output of the programmable divider.

21. Reference source: A very accurate and stable frequency source, which is typically a quartz crystal oscillator. The accuracy of the entire synthesizer is dependent on the accuracy of the reference source. The crystal oscillator operates in region of 1 to 10MHz and that frequency is divided down using digital counters to provide the necessary clock and reference frequency synthesizer. Loop filter: An analog filter and is required to assure stable and noise free operation of the synthesizer.

22. Analyzer: The fools that can evaluate the amount of distortion under the topic of signal and spectrum analysis. Types of analyzer: Analyzer mainly two types: 1.Wave analyzer. 2.Spectrum analyzer. Wave analyzer: An instrument designed to measure the relative amplitudes of single frequency components in a complex or distorted waveform. Acts as a frequency selective voltmeter which is tuned to the frequency of one signal component while rejecting all the other signal component.Now we disscuss about different types of wave analyzer:

23. Frequency-selective wave analyzer

24. The Frequency Selective Wave Analyzer consists of a very narrow pass-band filter section which can be tuned to a particular frequency within the audible frequency range (20 Hz — 20 kHz). The block diagram of a wave analyzer is as shown in Fig. 9.1(b).Frequency Selective Wave Analyzer The complex wave to be analyzed is passed through an adjustable attenuator which serves as a range multiplier and permits a large range of signal amplitudes to be analyzed without loading the amplifier.The output of the attenuator is then fed to a selective amplifier, which amplifies the selected frequency. The driver amplifier applies the attenuated input signal to a high-Q active filter. This high-Q filter is a low pass filter which allows the frequency which is selected to pass and reject all others. The magnitude of this selected frequency is indicated by the meter and the filter section identifies the frequency of the component. The filter circuit consists of a cascaded RC resonant circuit and amplifiers. For selecting the frequency range, the capacitors generally used are of the closed tolerance polystyrene type and the resistances used are precision potentiometers. The capacitors are used for range changing and the potentiometer is used to change the frequency within the selected pass-band, Hence this wave analyzer is also called a Frequency selective voltmeter.The entire AF range is covered in decade steps by switching capacitors in the RC section.The selected signal output from the final amplifier stage is applied to the meter circuit and to an untuned buffer amplifier. The main function of the buffer amplifier is to drive output devices, such as recorders or electronics counters.The meter has several voltage ranges as well as decibel scales marked on it. It is driven by an average reading rectifier type detector.

25. The wave analyzer must have extremely low input distortion, undetectable by the analyzer itself. The bandwidth of the instrument is very narrow, typically about 1% of the selective band given by the following response characteristics. (Fig. 9.2).

26. Heterodyne wave analyzer

27. Spectrum analyzer VHF spectrum analyzer covering the range from 10KHz to 300MHz. Similar to an up converting superhytrodyne receiver.

28. The input signal to be analyzed is heterodyned to a higher intermediate frequency by an internal local oscillator. The input signal enters the instrument through a probe connector that contains a unity gain isolation amplifier. After proper attenuation, the input signal is heterodyned in the mixer stage with the signal from a local oscilaator. Tthe output of the mixer forms an intermediate frequency that is uniformly amplified by the 30MHz If amplifier. This amplified IF signal is than mixed again with a 30MHz crystal oscillator signal , which result in information centered on a zero frequency. An active filter with controlled bandwith and symmetrical slops of 72 db per octave than passes the selected component to the meter amplifier and detector circuit. The output from the meter detector can be read of a decibed calibrated scale or may be applied to a recording device.

29. The input of the spectrum analyzer is first converted to an IF higher than the highst input frquency. As with evrey super hetrodyne, the input image must be removed ,which in this case represents the band of frequencies from 600 to 100 MHz which can easilly be removed with a low pass filter. In addition to removing the image , the input lowpass filter should also attenuate any signals at the first IF of 400 MHz. The frequency of the first local oscillolator is swept electronically usually using varactor diods in a manner similar to the sweep generator.