Bandwidth (signal processing)

About: Bandwidth (signal processing) is a research topic. Over the lifetime, 48550 publications have been published within this topic receiving 600741 citations. The topic is also known as: Bandwidth (signal processing) & bandwidth.

Band-Limited Volterra Series-Based Digital Predistortion for Wideband RF Power Amplifiers

Abstract: The continuously increasing demand for wide bandwidth creates great difficulties in employing digital predistortion (DPD) for radio frequency (RF) power amplifiers (PAs) in future ultra-wideband systems because the existing DPD system requires multiple times the input signal bandwidth in the transmitter and receiver chain, which is sometimes almost impossible to implement in practice. In this paper, we present a novel band-limited digital predistortion technique in which a band-limiting function is inserted into the general Volterra operators in the DPD model to control the signal bandwidth under modeling, which logically transforms the general Volterra series-based model into a band-limited version. This new approach eliminates the system bandwidth constraints of the conventional DPD techniques, and it allows users to arbitrarily choose the bandwidth to be linearized in the PA output according to the system requirement without sacrificing performance, which makes the DPD system design much more flexible and feasible. In order to validate this idea, a high-power LDMOS Doherty PA excited by various wideband signals, including 100-MHz long-term evolution advanced signals, was tested. Experimental results showed that excellent linearization performance can be obtained by employing the proposed approach. Furthermore, this technique can be applied to other linear-in-parameter models. In future ultra-wideband systems, this new technique can significantly improve system performance and reduce DPD implementation cost.

Optical sinc-shaped Nyquist pulses of exceptional quality

Abstract: Sinc-shaped Nyquist pulses possess a rectangular spectrum, enabling data to be encoded in a minimum spectral bandwidth and satisfying by essence the Nyquist criterion of zero inter-symbol interference (ISI). This property makes them very attractive for communication systems since data transmission rates can be maximized while the bandwidth usage is minimized. However, most of the pulse-shaping methods reported so far have remained rather complex and none has led to ideal sinc pulses. Here a method to produce sinc-shaped Nyquist pulses of very high quality is proposed based on the direct synthesis of a rectangular-shaped and phase-locked frequency comb. The method is highly flexible and can be easily integrated in communication systems, potentially offering a substantial increase in data transmission rates. Further, the high quality and wide tunability of the reported sinc-shaped pulses can also bring benefits to many other fields, such as microwave photonics, light storage and all-optical sampling.

No-switching quantum key distribution using broadband modulated coherent light

Abstract: We realize an end-to-end no-switching quantum key distribution protocol using continuous-wave coherent light. We encode weak broadband Gaussian modulations onto the amplitude and phase quadratures of light beams. Our no-switching protocol achieves high secret key rate via a post-selection protocol that utilizes both quadrature information simultaneously. We establish a secret key rate of 25 Mbits/s for a lossless channel and 1 kbit/s for 90% channel loss, per 17 MHz of detected bandwidth, assuming individual Gaussian eavesdropping attacks. Since our scheme is truly broadband, it can potentially deliver orders of magnitude higher key rates by extending the encoding bandwidth with higher-end telecommunication technology.

Electronic mode stirring for reverberation chambers

Abstract: A modal analysis and a uniform-field approximation are presented for the fields in an idealized two-dimensional, rectangular cavity excited by an electric line source. The model is used to evaluate the effectiveness of frequency stirring, an alternative to mechanical stirring in reverberation chamber immunity measurements. Numerical results indicate that good field uniformity (standard deviation less than 1 dB) can be obtained with a bandwidth of 10 MHz at a center frequency of 4 GHz. The bandwidth requirement is determined primarily by the number of modes excited, and higher frequencies can achieve the same field uniformity with a smaller bandwidth because of the higher mode density. Cavity excitation by two single-frequency sources is also analyzed. >

Underwater Acoustic Communications: Design Considerations on the Physical Layer

Abstract: Acoustic propagation is characterized by three major factors: attenuation that depends on the signal frequency, multipath propagation, and low speed of sound (1500 m/s). The channel has a sparse impulse response, where each physical path acts as a time-varying low-pass filter, and motion introduces additional Doppler spreading and shifting. Because propagation is best supported at low frequencies, acoustic communication systems are inherently wideband. The way in which these facts influence the design of signal processing methods is considered for single-carrier and multi-carrier systems. Moreover, the facts that the available bandwidth and transmission power depend heavily on the distance, and that channel latency is high, bear important implications on the design of network architectures and related protocols.