Guide Wavelength Measurements Essay Example for Free

Guide Wavelength Measurements EssayThe relationship between the wavelength in free space and the guide wavelength. Furthermore, this sample will be a way in which to gain experience in utilise varied types of laboratory communications equipment. Introduction What is wavelength? Wavelength of a sinusoidal wave is the distance between identical points in the adjacent cycles of a waveform signal.Wavelength is ordinarily designated by the Greek letter lambda (? )Wavelength is inversely correlated to oftenness (figure 1. 1), therefore the exalteder the frequency of the signal, the shorter the wavelength. vp Is the phase velocity f is the frequency vp Is the phase velocity f is the frequency ?=vpf Figure 1. 1 What is a wave guide? Figure 1. 2 A wave guide is a special form of transmission line consisting of a rectangular (figure 1. 2) or cylindrical metallic element tube or pipe, through which electromagnetic waves be propagated in microwave and RF communications. It s commonl y used in microwave communications, broadcasting, and radar installations.A wave guide must have a authoritative minimum dia measure relative to the wavelength of the signal and therefore are practical only for signals of extremely high frequency. Consequently below such frequencies, waveguides are useless as electrical transmission lines. An electromagnetic arena can propagate along a waveguide in various ways. Two common modes are known as transverse-magnetic (TM) and transverse-electric (TE). In TM mode, the magnetic lines of flux are perpendicular to the axis of the waveguide.In TE mode, the electric lines of flux are perpendicular to the axis of the waveguide. Either mode can reserve low loss and high efficiency as long as the interior of the waveguide is kept clean and dry. Some disadvantages are * The high cost, since the material used is special alloy (copper and silver). * It is not practicable to pass DC currents along with your RF signal. * The volume and mass part icularly are at set down frequencies. Although there is quite a few disadvantages the fact that you can transmit extremely high altitude powers and very low loss outweighs it.Furthermore the Silver plating used on the inside walls of the waveguide decreases the resistance loss making the copper and aluminium waveguides even more efficient. Experimental notes The experiment necessitate to be conducted to obtain the value of the guide wavelength and thereafter calculate the wave dimension and observe whether it matches the initial result that was greenbackd. The initial result measured was the value.Cut-off wavelength for the wave guide mode being propagate ? o = Wavelength in free space g = Guide wavelength, known as delta g The equation to measure ? o is already present as it is given by free-space. Although the cut-off wavelength can be calculated by rearranging the formula in figure 1. 1, the experiment will be used to further confirm this numerical formula. What we will acqui re is a range of guide wavelengths throughout the experiment in order to find out the Cut-off wavelength. Where is the cut-off wavelength for the waveguide mode being propagated? The dominant mode is being propagated in the rectangular waveguide (figure 1. 2) which substance where (a) is the internal broad dimension of the rectangular waveguide.Block diagram microwave oven signal source Isolator preset attenuator Wave meter Short circuit Calibrated attenuator Tuned SWR amplifier + meter stand wave detector Microwave signal source Isolator Preset attenuator Wave meter Short circuit Calibrated attenuator Tuned SWR amplifier + meter Standing wave detector Microwave signal source This device is the signal generator where you get 8 to 12 gigacycle per second. It is extremely expensive equipment and costs in the region of ? 20,000. This is due to the fact that we are traffic with high frequency signals and not with normal radio waves.Isolator By terminating one port, a circulator bec omes an isolator, which contains the property for competency to flow in one direction only. It samples some of the forward wave power and couples it to a set cavity wave meter for measuring the oscillator frequency. Preset attenuator Attenuators are essential building blocks when developing ladder stations for applications Attenuators are devices used to adjust signal levels which helps to stop the reflected power from reaching the oscillator, control resistance mismatch and to isolate circuit stages. Wave meterAny device for measuring the free-space wavelengths (or frequencies) of microwaves usually make of a cavity resonator whose dimensions can be varied until resonance with the microwaves is achieved. The determination is often do indirectly, by measuring the frequency of the wave. Calibrated attenuator The calibrator changes the value if it gets too high. Attenuators are manufactured with high-accuracy calibration, and for utmost precision. They acquirable in standard wav eguide were each attenuator is calibrated at the frequency specified at the clipping of order. Standing wave detectorStanding wave detector detects radio frequency signals along a transmission line or in a waveguide and changes it into a DC voltage for the originator that the waveguide cannot transmit DC currents along with the RF signal. Tuned SWR amplifier + meter Thestanding wave ratiometermeasures theSWR (standing-wave-ratio)which is the ratio of the bountifulness of a partial standing wave at a maximum to the amplitude at a minimum in a transmission line. This is an item ofradioequipment used to checker the quality of the match between theantennaand thetransmission line.Procedure 1. Set up the microwave bench, as indicated. 2. Read the basic instructions for the microwave bench and then obtain oscillations at 8. 5 GHz from the microwave signal source. 3. If it is possible, maximize the deflection on the SWR-meter by using the method outlined in the basic instructions. 4. Me asure the frequency, f, using the wave meter. Calculate the free space wavelength, ? o , by using ? o = c/f where c = 2. 997? 1010 cm s-1. 5. Move the standing wave detector (SWD) investigate along the slotted line and watch the SWR-meter.