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Advances in CMOS SSPM Detectors
Published in Krzysztof Iniewski, Biological and Medical Sensor Technologies, 2017
James F. Christian, Kanai S. Shah, Michael R. Squillante
The gain of the PMT depends on the number of dynodes and the bias. PMTs typically provide gains on the order of 106. Although the gain can be decreased by lowering the bias, there is a practical lower limit, which constrains their use as low or unity gain detectors. The photocathode and initial gain stage represents a critical step and a major factor in determining the signal and noise performance. Equation 13.6 shows the relative multiplication noise expected as a function of the gain for each stage in the PMT, where 〈m1〉 represents the average number of photoelectrons emitted by the photocathode. The excess noise factor for PMTs is typically ∼1.2:
Frequency Synthesis for Multiband Wireless Networks
Published in Krzysztof Iniewski, Wireless Technologies, 2017
John W. M. Rogers, Foster F. Dai, Calvin Plett
Fractional-N synthesizers often include ∑Δ modulators to shift the spurious components to a higher frequency band, where the loop filter can filter randomized spurs. In a ∑Δ fractional-N synthesizer, the average loop divisor value corresponds to the desired output frequency, and the instantaneous divisor value is dithered around the correct value by the ∑Δ modulator. The ∑Δ noise shaping can be modeled as a linear gain stage with an additive quantization noise source, which is shaped by a high-pass transfer function. Hence, the quantization error component at the synthesizer output is composed of mostly high-frequency noise that can be filtered by the PLL [21]. A block diagram of a typical ∑Δ modulator that is widely used in synthesizer applications is shown in Figure 15.6 [3]. This three-loop ∑Δ topology is called a multi-stage noise shaping (MASH) 1-1-1 structure because it is a cascaded ∑Δ structure with three first-order loops. Each of the three loops is identical. The input of the second loop is taken from the quantized error Eq1 of the first loop, whereas the input of the third loop is taken from the quantized error Eq2 of the second loop. Thus, only the first loop has a constant input, which is the fractional portion of the desired rational divide number ·F(z), i.e., the fine tune word. The integer part of the frequency word I(z), the coarse tune word, is added at the output of the three-loop ∑Δ modulator. Thus, Ndiv(z) = I(z) + F(z) is the time sequence used to control the integer-restricted divider ratios. The modulator is clocked at the divider output frequency, reflecting the sampled nature of the circuit.
CMOS Image Sensors
Published in Junichi Nakamura, Image Sensors and Signal Processing for Digital Still Cameras, 2017
The analog processing in CMOS image sensors is divided into column parallel and serial segments. Usually, the noise suppression circuit is implemented in column parallel. An analog programmable gain stage and an ADC stage follow the noise suppression circuit. Gain settings of the programmable gain amplifier (PGA) determine the camera’s ISO speed and are controlled so that the input range of the ADC is effectively utilized.
A Low Power CMOS UWB LNA with Dual-band Notch Filter Using Forward Body Biasing
Published in IETE Journal of Research, 2020
Maryam Babasafari, Mostafa Yargholi
The federal communications commission (FCCs) ruling in February 2002 in the USA has approved the standard of ultra-wideband (UWB) technology to use a large bandwidth of 7.5 GHz from 3.1 to 10.6 GHz for commercial applications [1]. This standard provides low complexity, high data rate, low cost, low power dissipation, and high-security wireless telecommunication which can used for short-range purposes. The most important reasons for quick growth in the designing of these circuits are request of these modules for medical imaging systems, wireless personal area networks (WPAN), ground and vehicular penetrating radars, and sensor nodes for wireless networks [2]. Literatures illustrate that an UWB system can effectively transmit information at a rate of 110 Mbps at a distance of 10 m [3]. Recently, high speed and high data rate wireless communication are interested in the portable device and equipment. For example, data rates of 54 and 11 Mbps at an operation frequency of 2.4 GHz are attracted in the IEEE 802.11g and 802.11b standard, respectively. However, the operation frequency of 5.7/5.2 GHz is established in the IEEE 802.11a to avoid from interfering and crowding at 2.4 GHz. Thus, an UWB system is considered except for 2.4, 5.2, and 5.7 GHz. The CMOS technology is a suitable select for the implementation of low band UWB system when considering the hardware cost, time to market, and the level of difficulty [4,5]. The low noise amplifier (LNA) is the first gain stage of a receiver. It must satisfy numerous specifications at the same time, which makes its design and implementation challenging. The signals coming from the receiver antenna are very small; therefore, signal amplification is required before feeding it into the mixer. This procedure sets the requirement of a certain gain to the LNA. The received signal should has a certain Signal to Noise Ratio (SNR) to allow suitable detection. Consequently, the noise which added via the LNA circuit should be reduced as much as possible. A large interference signal or blocker can happen at the input of the LNA. The modules should be appropriately linear to have a logical signal reception. For mobile and portable applications, moderate power dissipation is another restriction. Until now, published CMOS-based wideband amplifiers are implemented in numerous topologies [6]. In this paper, we proposed a cascode configuration that improves the input-output reverse isolation and the frequency response of the CMOS UWB LNA utilizing input stage common source (CS), input passive filtering structures, and forward body biasing technique for the wideband applications. In addition, a dual-band notch filter (with active inductors) is employed after the LNA core to frequency attenuation purposes. furthermore, a notch filter eliminates the WLAN interferers from 2.4 to 10.2 GHz frequency bands.