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NTSC Analog Television
Published in Skip Pizzi, Graham A. Jones, A Broadcast Engineering Tutorial for Non-Engineers, 2014
A simplified block diagram of an analog television receiver, usually known as a TV set, is shown in Figure 15.3. An antenna picks up the over-the-air radio waves and feeds the radio frequency signal to the first stage of the receiver, where the RF tuner amplifies the weak signal and selects the desired broadcast channel. This signal is then converted to a lower intermediate frequency (IF) which is further amplified and then demodulated in the detector stage, reversing the amplitude modulation process described in Chapter 7. This recreates the composite NTSC video signal and FM sound signal. The composite video decoder separates the luminance and chrominance signals and demodulates the chrominance into two color difference signals. By adding and subtracting the luminance and color difference values, the receiver produces the separate red, green, and blue signals. These RGB analog video signals are amplified to drive the display device (e.g., a cathode ray tube, or an LCD or plasma flat panel display) to produce the red, green, and blue parts of the picture, which are transmitted line-by-line and frame-by-frame. The human eye then combines the red, green, and blue images together to see a complete, full-color picture.
Electronic systems
Published in Joe Cieszynski, David Fox, Electronics for Service Engineers, 2012
Having built systems to transmit both AM and FM signals the receivers for these systems need to be examined. There are a variety of systems which can be constructed for use on either of these two systems. The most common arrangement uses the supersonic heterodyne principle commonly called a superhet. It has a very simple fundamental principle which is that, irrespective of the RF frequency a user tunes to, the incoming RF signal will be changed to a common frequency before amplification. This new frequency is called the intermediate frequency and abbreviated to the term IF. Before examining the superhet receiver it is worth looking at the simple design of a tuned radio frequency receiver or TRF. This type of receiver can be used for either AM or FM reception provided the appropriate type of demodulator is used. A basic block diagram is shown in Figure 13.30.
Transmitters and receivers
Published in Mike Tooley, David Wyatt, Aircraft Communications and Navigation Systems, 2017
The output of the RF amplifier stage is applied to the mixer stage. This stage combines the RF signal with the signal derived from the local oscillator (LO) stage in order to produce a signal at the intermediate frequency (IF). It is worth noting that the output signal produced by the mixer actually contains a number of signal components, including the sum and difference of the signal and local oscillator frequencies as well as the original signals plus harmonic components. The wanted signal (i.e. that which corresponds to the IF) is passed (usually by some form of filter— see page 58) to the IF amplifier stage. This stage provides amplification as well as a high degree of selectivity.
A reconfigurable wireless superheterodyne receiver for multi-standard communication systems
Published in International Journal of Electronics, 2023
Qing Wang, Yongle Wu, Yue Qi, Weimin Wang
At present, there are many mainstream wireless receiver architectures for communication equipment. Such as superheterodyne receiver architecture (Dan et al., 2019), zero intermediate frequency (zero-IF) receiver architecture (T. Wang et al., 2019), and low intermediate frequency (low-IF) receiver architecture (Zhang et al., 2018). Among them, the superheterodyne receiver architecture is widely used in wireless communication systems. The superheterodyne receiver has many advantages, such as excellent frequency selection characteristics, good interference suppression, and a large dynamic range. The zero-IF receiver is simple and easily integrated, but noise and linearity are not as good as the superheterodyne receiver. The cost of the low-IF receiver is high because it needs a high-performance Analog-to-Digital Converter. According to our design requirements, we finally choose the superheterodyne structure to form the proposed receiver.
Noise model of the cryogenic nuclear magnetic resonance spectroscopy system's receiving chain
Published in Automatika, 2022
Petar Kolar, Lovro Blažok, Dario Bojanjac
The basic diagram of the cryogenic NMR spectroscopy system, used in condensed matter physics, can be seen in Figure 1. This system has two modes of operation: the transmitting (Tx) mode and the receiving (Rx) mode. During the Tx mode, high-power pulses (up to the order of a kW) are generated by a signal generator inside the spectrometer (this instrument will soon prove to be the main part of this NMR spectroscopy system) in order to excite the sample's nuclei. These pulses are then amplified by a power amplifier and transmitted to the probe's coil via the duplexer. There, they generate a magnetic field that excites the nuclei of the sample under measurement. This is the end of the Tx mode and the system ”switches” to the Rx mode. The response signal of the sample has a very low magnitude (sometimes even down to the order of an fW), so it needs to be amplified before arriving at the spectrometer's receiver. This amplification is achieved by a low-noise NMR preamplifier. In the spectrometer, the received signal is firstly down-converted to an intermediate frequency and then further amplified by a variable-gain amplifier, which allows amplitude optimization before analogue-to-digital (A/D) conversion. After the detection and A/D conversion, the signal gets post-processed digitally, using different methods, such as time averaging of multiple measurement results and digital filtering. Finally, such a signal is then displayed on the spectrometer screen [6,7].
Design of IF-RF-Based Heterodyne Transmitter Using Current Steering DAC with 5.4 GHz Spur-Free Bandwidth
Published in IETE Journal of Research, 2022
Abhishek Kumar, Santosh Kumar Gupta, Vijaya Bhadauria
Figure 1 shows the block diagram of a heterodyne transmitter using a conventional approach. The output signal, RFout, is given by [11]: The 3-bit input data (Dre and Dim), first mix with an intermediate frequency (ωif) to obtain IFout, which further mix with local oscillator frequency (ωlo) to get RFout. The input data is mixed with IF and LO frequency to give the up-converted output signal at only if . If, , the mixing of the message with IF and LO frequency does not take place at a desired frequency and hence heterodyne transmitter suffers from random frequency shifts based on input data. So, using Equation (1) reduces to: The spectrum of the conventional heterodyne transmitter is shown in Figure 2, with its constellation diagram shown in Figure 3. The spectrum results in mixing product at the desired frequency when Dre = Dim.