Ôîðóì » Äèñêóññèè » Operazionnie ysiliteli ,ZAP/AZP & (ïðîäîëæåíèå) » Îòâåòèòü
Operazionnie ysiliteli ,ZAP/AZP & (ïðîäîëæåíèå)
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: Figure 4 shows an application which combines oversampling and undersampling. The signal of interest has a bandwidth BW and is centered around a carrier frequency fc. The sampling frequency can be much less than fc and is chosen such that the signal of interest is centered in its Nyquist zone. Analog and digital filtering removes the noise outside the signal bandwidth of interest, and therefore results in process gain per Eq. 10. Figure 4: Undersampling and Oversampling Combined Results in Process Gain https://www.analog.com/media/en/training-seminars/tutorials/MT-001.pdf
milstar: https://www.analog.com/media/en/technical-documentation/data-sheets/AD6688.pdf RF Diversity and 1.2 GHz Bandwidth Observation Receiver 895$ https://www.analog.com/media/en/technical-documentation/data-sheets/AD6674.pdf 385 MHz BW IF Diversity Receiver
milstar: http://www-users.york.ac.uk/~dajp1/Introductions/GSW_Noise_and_IP3_in_Receivers.pdf 200 khz noise reciever noise 9.45 db ,s/n 6 db -121+9.45+6= -105.55 db If we didn’t know what minimum signal-to-noise ratio was required for acceptable performance, all we could do is consider the sensitivity to be the minimum detectable signal MDS), which is the input signal that gives an output signal power equal to the output noise power. Using this definition, the sensitivity would be 6 dB less, at –111.55 dBm.
milstar: then you might think that this would give the entire receiver a very low IP3, since the signal would be so large at this stage. However, if the image filter just before this amplifier gets rid of all the signals except the wanted signal, then there aren’t any other signals left to produce any intermodulation products, and the IP3 of this component can be neglected. http://www-users.york.ac.uk/~dajp1/Introductions/GSW_Noise_and_IP3_in_Receivers.pdf
milstar: Communications: Mars Curiosity is equipped with significant telecommunication redundancy by several means: an X band transmitter and receiver that can communicate directly with Earth, Curiosity can communicate with Earth directly at speeds up to 32 kbit/s https://mars.jpl.nasa.gov/msl/mission/communicationwithearth/data/ Data Rates/Returns The data rate direct-to-Earth varies from about 500 bits per second to 32,000 bits per second
milstar: http://www.arrl.org/files/file/QEX_Next_Issue/Jul-Aug_2013/QEX_7_13_Horrabin.pdf
milstar: Do you need more than one SSB BW Filter? Best if Roofing & DSP bandwidths are equal. More selectivity up front is always desirable. Better shape factor than depending of last IF only. Omni-VII the 455 kHz filters really help total selectivity. Orion & K3 both offer a 1.8 kHz roofing filter. Reduces load on DSP ! Just not as dramatic improvement as on CW http://www.sherweng.com/documents/NC0B-Contest-U-2008-9.pdf
milstar: It is not possible to offer CW bandwidth Roofing Filters at VHF frequencies. It all comes down to fractional bandwidth. A 500-Hz filter at 5 MHz is like a 1-kHz filter at 10 MHz, or a 2 kHz filter at 20 MHz or a 4 kHz filter at 40 MHz & an 8 kHz filter at 80 MHz. FTdx-9000 IF = 40 MHz, 3-kHz reasonable. FT-2000 IF = 70 MHz, “3 kHz” = 7 kHz wide The Orion II and the K3 roofing filters are in the 8 to 9 MHz range, similar to the R-4C at 5 MHz. Narrow filters are no problem here http://www.sherweng.com/documents/NC0B-Contest-U-2008-9.pdf
milstar: https://www.analog.com/media/en/reference-design-documentation/design-notes/DSOL44.pdf
milstar: https://www.aanda.org/articles/aa/pdf/2010/02/aa13335-09.pdf SFDR 112 dbc ltc2208 until 30 mhz
milstar: For example, an rms clock jitter of 200 femtoseconds limits an ADC’s SNR performance to no better than 70 dB at 250 MHz. However, a 1 GHz input signal would need an rms clock jitter of 50 femtoseconds or better to achieve the same SNR performance of 70 dB. https://www.analog.com/en/technical-articles/noise-spectral-density.html
milstar: A high-speed analog-to-digital converter (ADC) typically has the largest noise figure of all components in the receiver signal chain. Its contribution to the system noise figure can be reduced greatly by adding more gain (with a low noise figure) upfront using low-noise amplifiers (LNAs). However, this method cannot be used in a blocking scenario. In the presence of a large in-band interferer or jammer that can’t be filtered out, the gain in the signal chain must be reduced in order to avoid saturation of the ADC input. Therefore, the only way to really improve the receiver noise figure is to improve the noise floor by using a data converter with a better signal-to-noise ratio (SNR), as shown in the example https://www.microwavejournal.com/ext/resources/whitepapers/2015/May-2015/HS-ADC-never-has-enough-SNR_FINAL.pdf?1522090117
milstar: ADS54j60 1 GSPS NSD -158.1 dbfs NF -19.5 db https://www.microwavejournal.com/ext/resources/whitepapers/2015/May-2015/HS-ADC-never-has-enough-SNR_FINAL.pdf?1522090117
milstar: http://www.ti.com/lit/an/slyt090/slyt090.pdf
milstar: An example of a superheterodyne receiver frequency plan for X-band is shown in Figure 2. In this receiver, it is desired to receive between 8 GHz and 12 GHz with a 200 MHz bandwidth. The desired spectrum mixes with a tunable local oscillator (LO) to generate an IF at 5.4 GHz. The 5.4 GHz IF then mixes with a 5 GHz LO to produce the final 400 MHz IF. The final IF ranges from 300 MHz to 500 MHz, which is a frequency range where many ADCs can perform well. https://www.analog.com/en/technical-articles/x-and-ku-band-small-form-factor-radio-design.html# high side injection 200 mhz BW lo1 13.4 ghz -17.4 ghz 1IF 5.4 ghz +-100 mhz 5.3 ghz -5.5 ghz 2 IF 400 mhz +- 100 mhz 300-500 mhz rf x band 8-12 ghz
milstar: https://www.analog.com/media/en/technical-documentation/data-sheets/AD9371.pdf https://www.analog.com/media/en/technical-documentation/application-notes/AN-1354.pdf https://www.analog.com/en/analog-dialogue/articles/where-zero-if-wins.html
milstar: The IMD curve in Figure 3 is divided into three regions. For low level input signals, the IMD products remain relatively constant regardless of signal level. This implies that as the input signal increases 1 dB, the ratio of the signal to the IMD level will increase 1 dB also. When the input signal is within a few dB of the ADC full-scale range, the IMD may start to increase (but it might not in a very well-designed ADC). The exact level at which this occurs is dependent on the particular ADC under consideration—some ADCs may not exhibit significant increases in the IMD products over their full input range, however most will. As the input signal continues to increase beyond full-scale, the ADC should function acts as an ideal limiter, and the IMD products become very large. For these reasons, the 2nd and 3rd order IMD intercept points are not specified for ADCs. It should be noted that essentially the same arguments apply to DACs. In either case, the single- or multi-tone SFDR specification is the most accepted way to measure data converter distortion. https://www.analog.com/media/en/training-seminars/tutorials/MT-012.pdf
milstar: https://www.armms.org/media/uploads/what-are-the-dynamic-range--limits-of-rf-adcs.pdf
milstar: Paralleling Amplifiers Improves Signal-to-Noise Performance The benefits of adding amplifiers in parallel are improved SNR and lower voltage noise density. For N amplifiers in parallel, the amplifier noise power is reduced by N and the input referred voltage noise density is reduced by √N. Put another way, each time the number of amplifiers is doubled, the amplifier noise power decreases by 2 and the amplifier's input referred voltage noise density decreases by √2. Note that paralleling amplifiers can only reduce the uncorrelated noise added by the amplifiers; it cannot reduce the noise due to other external noise sources (ex. resistors, sensors, other signal conditioning components, etc. In the two parallel amplifier circuit above, the LT6020's input voltage noise density is reduced from 45nV/√Hz to 32nV/√Hz. The circuit below reveals how the input noise density is reduced for N amplifiers with the LT1028 ultralow 0.85nV/√Hz noise density, precision amplifier.
milstar: https://www.analog.com/en/analog-dialogue/articles/multichannel-a-d-converters.html#
ïîëíàÿ âåðñèÿ ñòðàíèöû