Found 993 Articles for Electronics & Electrical

For establishing a reliable wireless communication link, a wireless design engineer must operate at optimum levels of performance deciding parameters such as transmission power, transmission bandwidth, antenna gain and so on. Not all the parameters that affect the performance of a wireless link are under the control of a design engineer.Not all performance related parameters are under the control of the designChannel noises, adjacent channel interference, fading- to name a few, are not under the control of the design engineer. Therefore, the designer must tune or adjust the parameters that could be controlled so as to achieve the maximum utilization ... Read More

A wireless link budget, in general, estimates the possible losses that will be encountered by the signal being transmitted and adjustments are made on the design parameters to combat the effects of such losses. EIRP is commonly used in wireless link budget calculations to specify the power level required for transmission.How would you define Effective Isotropic Radiated Power (EIRP)?As the name suggests, the EIRP takes power transmitted by an isotropic source as the reference. EIRP combines the power of the transmitting antenna and its gain. EIRP is expressed as the product of the power of the transmitting antenna and its ... Read More

A composite signal is composed of several frequency components. Each frequency component corresponds to a signal. Such signals of different frequencies put togetherforms a composite signal. Different signal frequencies present in the signal respond differently to the channel noise conditions. Power spectral density specifies the power levels of the frequency components present in a signal. It is denoted as PSD inshort. The PSD specifies the power of various frequencies present in the signal and we can determine the range of power over which the signal frequencies are operating at. Essentially, the PSD profile is a plot of the power over ... Read More

This article presents some of the numerical problems on SNR.Question 1At the transmitter, the signal power is 23 mW. The input SNR is 40 dB. The channel offers 3 dB attenuation to the signal and the output noise is thrice the input noise level. Determine the SNR at the output.Soln − $SNR_{i/p}=\frac{S_{i/p}}{N_{i/p}}$Calculation Of Output Power LevelAn attenuation of 3 dB equals halving the input transmission power. If the ratio of two quantities on the linear scale is 1/2, it translates to -3 dB on the dB scale which is indicated as attenuation. So, the output signal power is 23mW/2 =11.5 mW.Calculation ... Read More

The ‘Signal-to-Noise’ ratio or, SNR (in short), is a metric that describes the signal performance in the presence of wireless channel noise (interference). In the linear scale, the SNR is the ratio of the signal power to the noise power. The wireless channel is never noise-free.There always exist noise floors that the signal must combat to reach the receiver successfully. At the receiver, we, therefore, not only receive the transmitted signal. We have a noisy or, noise added version of the transmitted signal.Below is an example of SNRExpression for SNR$$SNR=\frac{Signal\:Power}{Noise\:Power}$$$$SNR(dB)=10log_{10}(\frac{Signal\:Power}{Noise\:Power})$$Key Properties of SNRSignal to Noise ratio in short is called ... Read More

Let us understand the significance of path loss by solving some numericals.Example 1 − Problem SolutionFor a microwave terrestrial-based line-of-sight communication operating at 10 GHz, what is the maximum faithful coverage distance that the signal could make before requiring a repeater? The following details are provided −Signal transmission power = 27.78 dBWTransmit antenna gain = 18 dBiReceive antenna gain = 20 dBiSignal transmission bandwidth = 4 MHz2- sided Noise power spectral density = 10-10 W/HzSolution − We are provided with the following data −ParameterValuePt30 dBW = 1000 WGt35 dBi = 3162.22Gr35 dBi = 3162.22f10 GHzB4 MHzN0/210-10 W/HzWe know that the channel ... Read More

Usually, the wireless channel is noisy. We can’t have a noise-free communication. We often use the AWGN (Additive White Gaussian Noise) model for interpretation of the channel noise. Noise is assumed to get added to the signal and at the receiver; we have a signal that carries both the data and the noise. It is important that signal level at the receiver is reasonably above the noise floor so that the detector can faithfully detect and decode the signal data.Apart from noise, losses in the atmosphere can also distort the transmitted signal. Some of the common losses taken into consideration ... Read More

In this section, we will solve some problems on wireless channel noise based on the white noise model.Example Problem 1A white noise has a 2-sided power spectral density of 6 kW/MHz. It is passed through a low pass filter having a bandwidth of 1 kHz. Compute the output noise power.Solution −The 2-sided power spectral density is 6 kW/MHz. The power spectral density is usually represented in W/Hz.$$\frac{6kW}{MHz}=\frac{6000W}{1000000Hz}=\frac{0.006W}{Hz}=\frac{N_{0}}{2}$$The 2-sided power spectral density N0/2 is 0.006W/Hz. Therefore, N0 = 0.012W/Hz.The noise power is expressed as the product of the noise power spectral density and the noise bandwidth.$$N_{p}=N_{0}.BW$$$$N_{p}=\frac{0.012W}{Hz}.1kHz=12W$$The noise power of the given ... Read More

What is Wireless Channel Noise?It is not possible to have any wireless communication system/link with absolutely zero noise level. Noise is additive and hence at the receiver, we have the signal that contains both the transmitted data and noise. The most commonly used noise model is the Additive White Gaussian Noise (AWGN). The noise follows Gaussian distribution with zero mean.What are the effects of channel noise?The channel noise could distort the original user data signal.If the channel noise is too high, it will bring down the Signal-to-Noise Ratio (SNR) of the signal as a result of which the receiver might not be ... Read More

Let us look at some numerical on amplifiers to get a better grip of the theoretical understanding.The ratio of output to input voltage of an amplifier is 20. Compute the voltage gain.Solution − The voltage ratio is given as 20. We need to convert this linear ratio into logarithmic ratio to arrive at the solution.$$Voltage\:gain(dB)=20log_{10}(20)\sim\:26dB$$The positive voltage gain indicates that the output power is greater than the input power.What does amplification in power by 3 dB indicate?Solution − Let the output power be ‘y’ and input power be ‘x’. Representing this as an equation, we have$$3dB=10log_{10}(\frac{y}{x})$$$$log_{10}(\frac{y}{x})=0.3dB\Rightarrow\:\frac{y}{x}=10^{0.3}\sim\:2$$Thus, the output power is twice the ... Read More