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Satellites
Published in Mohammad Razani, Commercial Space Technologies and Applications, 2018
Co-channel interference occurs if external interference from other transmitters (e.g., terrestrial microwave transmitters) is at the same frequency as the signal of interest. Interference that is near the frequency of the signal is called adjacent channel interference. Co-channel interference may be caused by either of the following: harmonics from a different type of system unintentional radiators signals from a similar system that are some distance away (frequency reuse). In each case, the interference is received within the operating bandwidth of the receiver. Unlike thermal noise, co-channel interference cannot be reduced by simply increasing carrier power because increasing the carrier power at one nominal bandwidth increases the likelihood of interference with the carriers that are adjacent in frequency to the wanted carrier.
Noise and Interference
Published in Michel Daoud Yacoub, Foundations of Mobile Radio Engineering, 2019
Adjacent-channel interference (as well as the additive noise) is a well-known problem of communication systems. However, its importance in cellular systems has been accentuated due to the spectrum efficiency improvement “neurosis.” Adjacent-channel interference can be minimized by (1) improving the modulation techniques, (2) improving the filtering quality of the equipment, and (3) allowing some guard channels between channels allocated to each cell. By far, the biggest problem of all is cochannel interference, an intrinsic issue of the cellular network. We will dedicate the rest of this section to describing the method of combatting this kind of interference.
AM Considerations
Published in David P. Maxson, The IBOC Handbook, 2007
Transmission impairments affecting the digital IBOC signal also can contribute to interference with reception of the analog host and interference with the reception of stations on other channels. A distorted digital signal can impose an irritating noise in the received program material of the analog host. Impairments can also increase out-of-band and spurious emissions, creating what may appear as “adjacent-channel interference” to other stations, when it is in fact unwanted emissions falling on the necessary bandwidth of another signal.
A Committee Machine Neural Network for Dynamic and its Inverse Modeling of Distortions and Impairments in Wireless Transmitters
Published in IETE Journal of Research, 2023
Manoj Bhatt, Meenakshi Rawat, Sanjay Mathur
For efficient use of HPA, HPA should be operated in high-power region near saturation, which severely distorts the information signal. Due to non-linearity there always exists an elemental tradeoff between the linearity and the efficacy of the HPA. For power-efficient transmission, the HPA linearity must be sacrificed. On the other hand for distortion-free transmission, power efficiency is sacrificed. These nonlinear distortions become more vulnerable when communication system demands high data rate transmission, achieved using Bandwidth-efficient modulation techniques, for instance, Quadrature Amplitude Modulation (QAM) or multicarrier signals in orthogonal frequency division multiplexing (OFDM) [1] having large envelope fluctuation or high peak-to-average power ratio (PAPR). The nonlinearity of HPA produces two types of distortions, harmonic (in-band) and intermodulation (out-of-band spectral regrowth). The harmonic distortion degrades the quality of the signal increasing the bit error rate [1,2], and deteriorating the performance of the system in the operating band. The other distortion leads to adjacent channel interference [2], leading to the failure of other communication systems operating in the adjoining frequency bands and violations of the out-of-band emission restrictions mandated by regulatory bodies. These two distortions can be observed as squeezing and twisting in the constellation of the transmitted signal.
Wavelet OFDM-Based Non-orthogonal Multiple Access Downlink Transceiver for Future Radio Access
Published in IETE Technical Review, 2018
It shows that due to the application of wavelets for wave shaping, our system gets better resistance against adjacent channel interference as compared to the conventional method. The conventional method uses DFT filters, which have low sideband attenuation. Thus, it requires more bandwidth to achieve the same data rate, and inclusion of CP worsens it further. On the other hand, wavelet-based system gives a much better result because of tight filters with better stop band attenuation. Our system can perform even better if wavelets decomposition level is further increased. It is clearly exemplified through Figure 5 that PSD of signal from W-NOMA is not a flat rectangular window; in fact, it is highly dependent on signals’ waveforms.
Halve dumbbell shaped DGS tapered ring antenna for dual-band notch characteristics
Published in Electromagnetics, 2018
A. Kamalaveni, M. Ganesh Madhan
A CPW-fed tapered rectangular ring dual band antenna with DGS structure has been designed, fabricated for the required bands of operation. Moreover, the required dual band has been achieved from the wideband antenna by notching unwanted frequencies using DS-DGS structures etched on the ground plane. Measurement results confirms that the proposed antenna has two independent rejection bands and 1.8 GHz and 3.5 GHz operating bands with the gain of 2.4 dB and 3.5 dB, respectively, and provides notching bandwidth of 2.4–2.8 GHz and 4–5.2 GHz which is wider than the reported antennas. Further, the proposed and rejection technique may find application in UWB antennas to overcome adjacent channel interference problems.