Noise in RF Systems

Simrock, Stefan; Zhang, Geng

doi:10.1007/978-3-030-94419-3_6

Cited by 3 publications

(6 citation statements)

References 14 publications

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“…The main source of noise in the measurement results is the measurement chain noise, including ADC, down-conversion mixer, the LO and CLK generator as well as the RF pick up cables. The phase noise added by the measurement chain can be estimated by measuring the RF reference signal with the same RF detector and the amplitude noise can be estimated by terminating the RF detector input with a matched load [15]. The estimation of the measurement chain noise is shown in figure 12(b) and it shows that the short-term amplitude jitter of the measurement chain is 0.002%, and the phase stability is 0.0067 • .…”

Section: The Short Time Stabilitymentioning

confidence: 99%

Development of a digital low-level RF system for the STCF

Xie,

Xiong,

Zhang

et al. 2024

J. Inst.

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With the development of particle physics, higher requirements are put forward for the brightness and energy of the collider. A new collider — the Super Tau-Charm Facility (STCF) — is under study in China. To meet the high acquirement of the quality of the beam, a digital low-level RF (LLRF) system that achieves high stability plays a critical role as a part of the microwave system of Linacs. This paper introduces the design of a digital LLRF system that works in the S-band (2856 MHz) as required by Linacs of the STCF. The system architecture and hardware design as well as the control algorithms and software design are discussed and tested. The system includes a signal source, a frequency synthesis system and an IF signal processor. The phase noise of the signal source is as low as 20.3 fs, and the low-level IF signal processor adopts amplitude and phase control by a PI-type controller. They jointly realize ultra-low phase noise signal output. The table experiments show that the short-term amplitude and phase stability of the system is better than 0.01% and 0.01°, respectively. The beam experiments show that the closed-loop phase stability in the cavity is about 0.1°. The results prove that the LLRF system meets the requirement of the STCF.

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Section: The Short Time Stabilitymentioning

confidence: 99%

Development of a digital low-level RF system for the STCF

Xie,

Xiong,

Zhang

et al. 2024

J. Inst.

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“…The gain distributions of these components severely influence the subsequent signal demodulation. The noise figure theory is an effective way at optimizing the influence of gain control because it establishes the relationship between gain distribution and signal quality [26]. Thus, the gain control strategy in "Part A" can be optimized as long as "Part A" is abstracted as the form of "Part B".…”

Section: Modeling Of Gain Control In Asr Systemsmentioning

confidence: 99%

“…The following will first introduce the noise figure theory and then demonstrate how to abstract a general model of the gain control strategy from diverse ASR systems in practice. Noise figure precisely reflects the influence of the components' cascaded gain and distortion on the signal chain quality [26]. Specifically, noise figure represents the degradation of the signal to noise ratio (SNR) when a signal goes through a device [26,29].…”

Section: Modeling Of Gain Control In Asr Systemsmentioning

confidence: 99%

“…(1) The gain of −3 dB is divided as −1 dB, −1 dB, and −1 dB on "Block A", "Block B", and "Block C", respectively; (2) The gain of −3 dB is divided as −2 dB, −1 dB, and 0 dB on "Block A", "Block B", and "Block C" respectively; (3) The gain of −3 dB is only performed on "Block C". From the perspective of noise, theories in [26] show that the noises caused by gain control can indirectly affect the accuracy of recognition by distorting the features of speech signals. However, even for a fixed gain value, different gain control strategies correspond to different noise levels, distorting the features of speech signals to different degrees.…”

Section: Introductionmentioning

confidence: 99%

“…This paper proposes an optimal gain control strategy named the maximized original signal transmission (MOST) to minimize the adverse effect of noises induced by gain control on ASR. The gain control strategy within the ASR system can be optimized, since it has been shown that the performances of similar systems, such as RF systems, can be significantly improved by modifying the gain structures [26,29]. Firstly, the gain control strategy's influence on the speech signal quality is analyzed by establishing a general model of the ASR system's gain control strategy.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Automatic Speech Recognition Performance Improvement for Mandarin Based on Optimizing Gain Control Strategy

Wang

Wei

Zhang

et al. 2022

Sensors

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Automatic speech recognition (ASR) is an essential technique of human–computer interactions; gain control is a commonly used operation in ASR. However, inappropriate gain control strategies can lead to an increase in the word error rate (WER) of ASR. As there is a current lack of sufficient theoretical analyses and proof of the relationship between gain control and WER, various unconstrained gain control strategies have been adopted on realistic ASR systems, and the optimal gain control with respect to the lowest WER, is rarely achieved. A gain control strategy named maximized original signal transmission (MOST) is proposed in this study to minimize the adverse impact of gain control on ASR systems. First, by modeling the gain control strategy, the quantitative relationship between the gain control strategy and the ASR performance was established using the noise figure index. Second, through an analysis of the quantitative relationship, an optimal MOST gain control strategy with minimal performance degradation was theoretically deduced. Finally, comprehensive comparative experiments on a Mandarin dataset show that the proposed MOST gain control strategy can significantly reduce the WER of the experimental ASR system, with a 10% mean absolute WER reduction at −9 dB gain.

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The design of LLRF system for STCF storage ring

Xiong,

Wang,

Liang

et al. 2024

Mod. Phys. Lett. A

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The Super Tau Charm Facility (STCF) is a new generation of high brightness electron–positron collider planned by China, designed to achieve a center of mass collision energy is 2–7[Formula: see text]GeV and a peak brightness is 0.5–[Formula: see text][Formula: see text]cm[Formula: see text]s[Formula: see text]. The digital low-level RF control system (LLRF), as the essential equipment of the storage ring RF system, is usually responsible for maintaining the stability of the cavity field. This paper presents the design scheme of LLRF for cavity in STCF storage ring, which mainly includes the hardware structure and software design of the system. We perform simulation analysis on the STCF RF system to evaluate the influence of delay and control parameters on the stability of the system and the influence of control parameters on the suppression of two kinds of noise. Desktop testing on the existing prototype demonstrates that the adopted direct-sampling architecture introduces less phase drift compared to the down-conversion architecture. Under the direct-sampling architecture, non-IQ demodulation offers better SNR and stability in both amplitude and phase. Specifically, direct-sampling in non-IQ mode achieves open-loop RMS short-term stability of 0.019% for amplitude and 0.021∘ for phase. Long-term stability in the closed-loop setting measures 0.027% for amplitude and 0.024∘ for phase.

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Noise in RF Systems

Cited by 3 publications

References 14 publications

Development of a digital low-level RF system for the STCF

Development of a digital low-level RF system for the STCF

Automatic Speech Recognition Performance Improvement for Mandarin Based on Optimizing Gain Control Strategy

The design of LLRF system for STCF storage ring

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