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Wireless Communications

Understanding Noise – Part 4: Noise Factor, Noise Figure & Noise Temperature

Previous posts in this series: Understanding Noise – Part 1: Defining Noise Understanding Noise – Part 2: Sources of Noise Understanding Noise – Part 3: Noise Spectral Density Digital communication systems require received signals to be filtered and amplified before they can be demodulated and passed to the analog to digital converter.  Similarly, transmitted signals […]

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Sampling

One of the most commonly misunderstood aspects of signal processing is the Nyquist-Shannon Sampling Theorem.  It has been noted before that many engineers misunderstand the theorem, selecting sampling frequencies that are often too low, causing errors in systems design.   An understanding of the underlying theory behind signal sampling is also useful to the communications engineer […]

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Passband Signals

The term Passband signal in the current context refers to the modulated signal that results from a baseband signal modulating a carrier wave.  Passband signals have some interesting characteristics that we will cover by referring to the diagrams below. (Disclaimer: illustrative purposes only). Properties of Passband Signals Shifted Frequency Response The complete frequency response (including […]

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Filters

Signal filtering plays a fundamental role in electronics and communications.  Filters modify specific frequency components of time-domain signals and are used as a tool for signal quality improvement, information recovery and frequency separation [1].  Filters are a fundamental frequency domain tool and as a component in electronic circuits and digital signal processing allow us to: […]

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Baseband Signals

The difference between the baseband signal and the passband signal in communications is really quite a simple one.  The baseband signal refers to any signal that has not modulated a carrier waveform. NOTE:  The use of the verb “modulated” there may made you think twice.  If so, you are not alone.  I always used to […]

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Fourier Transform

The Frequency Domain Many physical objects have a frequency range over which they perform most of their work.  Your ears for instance, can generally only hear frequencies between 20Hz and 20 kHz.  Your own voice when speaking normally, concentrates most power in the range of 500 to 2000Hz.  You can think of these as the […]

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