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Design of a Low-Power Dual-Mode MUX-Based Transmitter for Biomedical Applications
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
The PLL phase noise (Sθ_PLL) measured at the transmitter output (at a frequency of fvco/2; when ΣΔ–PR is disabled) is shown in Figure 4.33. This figure also shows the measured and estimated total transmitter output noises (Sθ) when ΣΔ–PR is activated. It is observed that the close-in phase noise is dominated by the PLL, while the phase noise at higher offset frequencies (i.e., larger than 10- MHz offset) is mainly contributed by the ΣΔ–modulation noise (Sθ_ΣΔ). The measured total transmitter noise between 100-kHz and 10-MHz offset frequency is higher than that estimated by simulation. Further investigation of this discrepancy reveals that this is attributed to the resampling operation in the ΣΔ–PR. As described in Section 4.7.1, the resampling circuit is added for the purposes of timing alignment. However, this resampling operation deteriorates the noise-shaping characteristics of the ΣΔ–MOD2, resulting in higher noise. When the random modulation data are applied to the ΣΔ–MOD2 input, the magnitude of these spurious tones is lowered and has less impact on the modulation quality. Figure 4.34 shows the measured modulation spectrum of 6-Mbps FSK signal.
Compressive Sensing Fundamentals
Published in Moeness Amin, Compressive Sensing for Urban Radar, 2017
Several other architectures have been proposed for collecting compressive measurements by combining elementary operations such as modulation, filtering, multiplexing, and low-rate sampling. The random demodulator (RD) involves multiplying the incoming signal by a PRBS, lowpass filtering the result, and collecting low-rate samples of the output [113]. The resulting Φ matrix has a banded structure and, with high probability, will satisfy the RIP with respect to the sparsity basis Ψ=FN [169]. The random-modulation preintegrator (RMPI) is essentially a multichannel implementation of the RD [51,185]. These devices can be used not only to capture spectrally sparse signals but also to capture signals with a sparse time–frequency profile. A hardware implementation [186] of the RMPI has been validated using a 13 × sub-Nyquist measurement rate to capture radar pulse parameters in an instantaneous bandwidth spanning 100 MHz to 2.5 GHz. The compressive mutliplexer (CMUX) is another multichannel architecture [159]. The CMUX involves breaking the signal into bands, randomly modulating each band, and adding the bands back together before sampling with a single analog-to-digital converter (ADC). The resulting Φ matrix can be shown to satisfy the RIP for signals with sparse multichannel spectra (see [159] for details). The modulated wideband converter (MWC) is based on an acquisition strategy known as Xampling [131,132]. A hardware prototype described in [132] can be used for digitizing signals with up to a 2 GHz Nyquist rate (having 120 MHz total of noncontiguous spectral content) at an average sample rate of just 280 Msps.
High-Efficiency Power Amplifiers
Published in Choi Jung Han, Iniewski Krzysztof, High-Speed and Lower Power Technologies, 2018
Guillermo Velasco-Quesada, Herminio Martínez‑García, Alfonso Conesa-Roca
Pulse-width modulation (PWM) in the most common technique used for the control of class-D amplifiers, but it is not the only one possible. In order to mitigate possible EMI emissions, alternative modulation schemes can be used. Some possibilities are schemes based on pulse-density modulation (PDM), random modulation technique and click modulation technique.
Conducted Electromagnetic Interference Spectral Peak Mitigation in Luo-Converter Using FPGA-Based Chaotic PWM Technique
Published in Electric Power Components and Systems, 2019
Sudhakar Natarajan, Pydikalva Padmavathi, Jyotheeswara Reddy Kalvakurthi, Thanikanti Sudhakar Babu, Vigna K. Ramachandaramurthy, Sanjeevikumar Padmanaban
Chaotic PWM technique is the newly proposed random method which has the features of both spread spectrum and pseudo randomness [17]. In this technique PWM frequency varies chaotically and hence energy is distributed evenly into entire frequency spectrum. Also, it involves pseudo-random modulation which appears to be random but it is deterministic in nature. It generates random outputs which will produce in a sequence and also it can also repeat in a cycle.