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Operazionnie ysiliteli ,ZAP/AZP & (продолжение)
milstar: 1941: First (vacuum tube) op-amp An op-amp, defined as a general-purpose, DC-coupled, high gain, inverting feedback amplifier, is first found in US Patent 2,401,779 "Summing Amplifier" filed by Karl D. Swartzel Jr. of Bell labs in 1941. This design used three vacuum tubes to achieve a gain of 90dB and operated on voltage rails of ±350V. ###################################################### It had a single inverting input rather than differential inverting and non-inverting inputs, as are common in today's op-amps. Throughout World War II, Swartzel's design proved its value by being liberally used in the M9 artillery director designed at Bell Labs. ######################################################################### This artillery director worked with the SCR584 radar system to achieve extraordinary hit rates (near 90%) that ####################################################################### would not have been possible otherwise.[3] ########################### http://en.wikipedia.org/wiki/Operational_amplifier
milstar: ANALOG FILTERSSTANDARD RESPONSES8.27 such as Williams's (see Reference 2), provide tabulated filter values. These tables classify the filter by where the C denotes Cauer. Elliptical filters are sometime referred to as Cauer filters after the network theorist Wilhelm Cauer. Maximally Flat Delay with Chebyshev Stop Band Bessel type (Bessel, linear phase with equiripple error and transitional) filters give excellent transient behavior, but less than ideal frequency discrimination. Elliptical filters give better frequency discrimination, but degraded transient response. A maximally flat delay with Chebyshev stop band filter takes a Bessel type function and adds transmission zeros. The constant delay properties of the Bessel type filter in the pass band are maintained, and the stop band attenuation is significantly improved. The step response exhibits no overshoot or ringing, and the impulse response is clean, with essentially no oscillatory behavior. Constant group delay properties extend well into the stop band for increasing n. As with the elliptical filter, numeric evaluation is difficult. Williams’s book (see Reference 2) tabulates passive prototypes normalized component values.
milstar: Figure 8.84: Resistor Comparison Chart Figure 8.85: Capacitor Comparison Char CAPACITOR COMPARISON CHART https://www.analog.com/media/en/training-seminars/design-handbooks/Basic-Linear-Design/Chapter8.pdf
milstar: ADC aperture jitter combines with the sampling clock jitterin an rms manner to further degrade the SNR. https://www.analog.com/media/cn/training-seminars/design-handbooks/3689418379346Section5.pdf To explore this further, Figure 1 illustrates a high level overview of a typical current X-band radar system. Within this system, two analog mixing stages are typically utilized. The first stage mixes the pulsed radar return to a frequency of around 1 GHz and the second to an IF in the region of 100 MHz to 200 MHz to enable sampling of the signal using a 200 MSPS or lower ADC, to a resolution of 12 bits or higher. https://www.analog.com/en/technical-articles/the-demand-for-digital.html#
milstar: https://www.analog.com/en/technical-articles/28-nm-adcs-enable-next-gen-electronic-warfare-rec-sys.html A spur analysis using the Keysight Genesys tool can be used to quickly come to the same conclusion. Figure 4 is from the WhatIF frequency planning tool. Figure 4 shows the WhatIF frequency planning tool, where it is set to a 10 GHz operating band, 1 GHz instantaneous bandwidth, high-side LO selection, and a search for up to fifth-order spurious. Spur free zones are illustrated in green and, in this case, fall in the 2nd Nyquist zone of a 3 GSPS ADC.
milstar: RF sampling: Learning more about latency In this post, I’m going to discuss latency in an analog-to-digital converter (ADC). Latency is the time it takes for a signal to travel from point A to point B. In an ADC, latency is how long it takes from the time that an analog input is applied to the time that the digital output word becomes available. Why is latency important? Regardless of the application, latency is a key specification as it determines the response time. For example, data acquisition systems used in military applications are sensitive to the absolute latency, with lower being better. On the other hand, a known latency or deterministic latency is a key requirement for newer techniques like beam forming that is being adopted to improve sensitivity and selectivity in cellular communications systems. Usually expressed in sampling clock cycles, latency naturally includes the time it takes for the ADC core to do the conversion. Conversion time is dependent on the ADC architecture; in a pipelined ADC, latency will depend on the number of internal stages in the pipeline, as opposed to successive-approximation register (SAR) converters that start transmitting the digital-output word within one or two clock periods. https://e2e.ti.com/blogs_/b/analogwire/archive/2017/02/09/rf-sampling-learning-more-about-latency
milstar: Secrecy is an important aspect of military operations. To reduce the probability of intercept or detection, a radar transmission’s form and magnitude is designed in many cases to spread energy over the widest possible frequency range. Low Probability of Intercept (LPI) and Low Probability of Detection (LPD) are classes of radar systems that possess certain performance characteristics that make them nearly undetectable by today’s modern intercept receivers. LPI features prevent the radar from tripping alarm systems or passive radar-detection equipment. To provide resistance to jamming, systems can be architected by intelligently randomizing and spreading the radar pulses over a wide band so there will only be a very small signal on any one band, an approach known as Direct Sequence Spread Spectrum (DS-SS), as seen in Figure 2. Frequency Hop Spread Spectrum (FH-SS) also provides some protection against full band jamming. In these cases, the wide transmission signal consumes bandwidth that is in excess of what is actually needed for the raw signal of interest. Therefore, a wider receiver bandwidth is needed to continue to advance system capability. https://militaryembedded.com/radar-ew/rf-and-microwave/bandwidth-king-aerospace-defense-applications One of the most important factors for success in an LPI system is to use the widest signal transmission bandwidth possible to disguise complex waveforms as noise. This technique conversely provides a higher-order challenge for intercept receiver systems that seek to detect and decipher these wideband signals. Therefore, while LPI and LPD are improved, radar transceiver complexity is increased by mandating a system that can capture the entire transmission bandwidth at once. The ability of an ADC to simultaneously digitize 500 MHz, 1,000 MHz, and even larger chunks of spectrum bandwidth in a single Nyquist band helps provide a means to tackle this system challenge. Moving these bands higher in frequency beyond the first Nyquist of the ADC can be even more valuable. Today’s wideband ADCs offer systems potential for multiple wide Nyquist bands within an undersampling mode of operation. However, using a high order ADC Nyquist band to sample requires strict front-end anti-alias filtering and frequency planning to preventing spectral energy from leaking into other Nyquist zones. ########################################## It also ensures that unwanted harmonics and other lower frequency signals do not fall into the band of interest after it is folded down to the first Nyquist. The bandpass filter (BPF) upstream of the ADC must been designed to filter out unwanted signals and noise that are not near the nominal bandwidth of interest. Since a direct sampling technique folds the signal energy from each zone back into the first Nyquist, there is no way to accurately discriminate the source of the content. As a result, rogue energy can appear in the first Nyquist zone, which will degrade signal-to-noise ratio (SNR) and spurious free dynamic range (SFDR). Spectral issues can potentially plague government and military applications, both for sensing and communications. Wideband communications and sensing systems require extremely high-speed data converters. GSPS ADCs from Analog such as the AD9234, AD9680, and AD9625 not only offer high sample rates for a wider instantaneous bandwidth, but also the ability to sample high frequency inputs above the first Nyquist.
milstar: http://www.panoradio-sdr.de/sdr-hardware/analog-frontend/
milstar: Minimum Detectable Signal (MDS) The minimum receivable power (Pemin) for a given receiver is important because the minimum receivable power is one of the factors which determine the maximum range performance of the radar. The sensitivity level MDS has got a value of 10 -13 Watts ( -100 dBm) for a typical radar receiver. для полосы в 1 герц предел -173.9db в режиме поиска минимум 1 megaherz=60 db , предел -113.9db All receivers are designed for a certain sensitivity level based on requirements. One would not design a receiver with more sensitivity than required because it limits the receiver bandwidth and will require the receiver to process signals it is not interested in. In general, while processing signals, the higher the power level at which the sensitivity is set, the fewer the number of false alarms which will be processed. Simultaneously, the probability of detection of a “good” (low-noise) signal will be decreased. Bandwith One of the most important factor is receiver noise. Every receiver adds a certain amount of noise to its input signal, and radar receiver is no exception. Even with very careful design, noise due to thermal motion of electrons in resistive components is unavoidable. The amount of such thermal noise is proportional to receiver bandwidth. Therefore, bandwidth reduction is a possible solution to the problem of receiver noise. However, if the bandwidth is made too small the receiver does not amplify and process signal echoes properly. A compromise is required. In practice, the receiver bandwidth of a pulse radar is normally close to the reciprocal of the pulse duration. For example, radar using 1 µs pulses may be expected to have a bandwidth of about 1 Mhz. Dynamic Range The receiver system must amplify the received signal without distortion. If a large clutter signal sends the system into saturation, the result is a modification to the spectrum of the signal. This change in spectral content reduces the ability of the signal processor to carry out Doppler processing and degrades the MTI improvement factor. Furthermore, if the receiver enters saturation, then there can be a delay before target detection is restored. In principle, the dynamic range of the receiver must exceed the total range of signal strength from noise level up to the largest clutter signal. In practice dynamic ranges of 80 dB’s or so meets system requirements. The clutter power confirms this requirement as it averages: Rain clutter up to 55 dB Angels to 70 dB Sea clutter to 75 dB Ground clutter to 90 dB. https://www.radartutorial.eu/09.receivers/rx04.en.html
milstar: https://www.phys.hawaii.edu/~anita/new/papers/militaryHandbook/rcvr_sen.pdf RECEIVER SENSITIVITY / NOISE
milstar: АО «ВЗПП-С» (г. Воронеж) Новые российские ПЛИС ПЛИС 5578ТС084 (АЕНВ.431260.422ТУ) предназначена для замены зарубежных микросхем EP3C16 фирмы Altera. Выпускается в 144-выводном металлокерамическом планарном корпусе МК 4248.144–1. · ПЛИС 5578ТС094 (АЕНВ.431260.423ТУ) предназначена для замены зарубежных микросхем EP3C25 фирмы Altera. Выпускается в 304-выводном металлокерамическом планарном корпусе МК 4251.304–2. Основные характеристики новых ПЛИС приведены в таблице. К 2020 году предприятие планирует выпуск новой ПЛИС 5578ТС064 (АЕНВ.431260.402ТУ), предназначенной для замены зарубежных микросхем EP3C55 фирмы Altera: https://www.soel.ru/novosti/2019/novye_rossiyskie_plis/ http://www.vzpp-s.ru/about.htm http://www.vzpp-s.ru/production/catalog.pdf
milstar: https://www.ti.com/lit/an/slaa824/slaa824.pdf SpursAnalysisin the RF SamplingADC
milstar: https://www.ti.com/lit/an/slyt738/slyt738.pdf
milstar: https://niir.ru/produkciya-i-uslugi/nasha-produkciya/bortovaya-apparatura-dlya-kosmicheskix-apparatov-svyazi-i-veshhaniya/maloshumyashhie-usiliteli/ Малошумящие усилители
milstar: The receiver had two down-conversion stages from the S-Band range input (2.7 GHz to 3.7 GHz) to 75 MHz for operation in the second Nyquist zone using a 14-bit ADC sampled at 100MHz. The second Nyquist zone was chosen as a good compromise between ADC frequency response and ease of anti-aliasing filtering. It also enables a frequency plan with better spurious performance. The instantaneous receiver bandwidth was about 15 MHz, set by an anti-aliasing filter placed at the ADC input. https://ieeexplore.ieee.org/document/4250284
milstar: Table IV shows only measured results and allows the following evaluation of the effect of the ADC on the analog segment of the receive chain: The ADC used sets the ST-SFDR performance of the receiver and does not have a significant effect on TT-SFDR, which is noticeably dominant. The ADC increases the system noise figure by design, depending on the gain configuration. The ADC affects the output SNR significantly. The maximum output signal is limited by the ADC saturation, which is well below the saturation (OTOI −10 dB) of the analog portion of the receiver.
milstar: https://www.d.umn.edu/~ihayee/Teaching/ee5765/ece5765_chapter_4_5.pdf Quadrature Amplitude Demodulation
milstar: http://web.mit.edu/6.02/www/f2006/handouts/Lec9.pdf Impact of Phase Misalignment in Receiver Local Oscillator
milstar: Квадратурную (quadrature) модуляцию осуществляют путем передачи по каналу связи в одной и той же полосе частот двух модулированных сигналов, несущие колебания которых ортогональны и квадратурны (их частоты равны, а фазы сдвинуты на 90°, что и поясняет смысл слова «квадратурный»). Временные диаграммы, поясняющие квадратурную модуляцию, Ранее были проанализированы случаи, когда амплитуда и начальная фаза несущего гармонического колебания подвергались модуляции по отдельности. Однако если изменять эти два параметра одновременно, то можно будет передавать сразу два сигнала, модулированных по амплитуде Uu(t) и фазе у(?) Такую модуляцию следовало бы назвать просто амплитудно-фазовой и, очевидно, аналоговой. Однако два модулирующих сигнала модулируют совершенно разные параметры несущего колебания — амплитуду и фазу. https://studme.org/171323/tehnika/kvadraturnaya_modulyatsiya
milstar: Как видно из этого уравнения, фаза сигнала может регулироваться изменением амплитуд I и Q. Итак, цифровую модуляцию несущего сигнала можно осуществить путём изменения амплитуды двух смешиваемых сигналов. Ниже показана блок-схема технических средств, необходимых для генерации сигнала. Блок квадратурного модулятора (Quadrature Modulator) предназначен для смешивания I и Q компонент исходного сигнала (Baseband) с сигналами гетеродина (local oscillator), и дальнейшего сложения друг с другом. Отметим, что фазы сигналов гетеродина также смещены на 90° относительно друг друга. http://media.ls.urfu.ru/510/1322/2969/
milstar: I-Q Quadrature Generator https://www.eecg.utoronto.ca/~kphang/papers/2001/dong_IQphase.pdf
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