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Signal Simulators and Emulators
Published in Felix Alberto Farret, Marcelo Godoy Simões, Danilo Iglesias Brandão, Electronic Instrumentation for Distributed Generation and Power Processes, 2017
Felix Alberto Farret, Marcelo Godoy Simões, Danilo Iglesias Brandão
Phase-locked loops (PLLs) are circuits for tracking the phase of a local signal generator with the phase of an external signal oscillator, regardless of the size or format of both. That is, the local signal and internal signal generated are based on the information contained in the external signal: zero crossings or frequency. The quality of the local oscillator is responsible for the quality of the signal generated by instrumentation and other applications. There are many examples of the uses of these circuits in the literature, such as to control the harmonic content of signals, control the reception of radio signals, and control and drive the power devices. The following text discusses the most common types of PLLs [5–9].
Distortion and Modulation Effects in RF Power Amplifiers
Published in Abdullah Eroglu, Linear and Switch-Mode RF Power Amplifiers, 2017
Figure 8.2 shows the block diagram of an ideal quadrature modulator. In practice, the I and Q signals could be generated digitally from a Field-Programmable Gate Array (FPGA) device and Digital-to-Analog Converter (DAC) combination. Low-pass filters would also be necessary to eliminate the aliasing effect of the digitally generated I and Q signals. The local oscillator (LO) could be created from a phase-locked loop (PLL) or some other tunable CW source. The signal at the output of the mixer on I and Q paths can be expressed as
L
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
local oscillator (1) an oscillator or circuit that produces a periodic signal whose function is to be utilized in the demodulation of a received radio signal. This periodic signal is typically a sinusoid and the oscillator is typically located in a radio receiver. The tuning of the radio to a given channel, or station, typically involves the tuning of the local oscillator. The local oscillator is part of the radio frequency (RF) front end of a radio receiver and is an important component in a heterodyne receiver.
Novel Quadrature Voltage-Controlled Oscillator Using Capacitor Coupling
Published in IETE Journal of Research, 2018
With the fast increasing of short-range and personal wireless communication systems, the demand of low-power, small-size, low-cost, and high-performance radio frequency (RF) transceiver systems are increasing rapidly in recent years. Voltage-controlled oscillator (VCO) is the key building block of wireless transceiver [1,2], and it provides the local oscillation (LO) signal for the wireless communication systems to realize the spectrum shifting of the useful signals.