Experiment 3 Frequency Modulation ECE 4117 Telecommunications Laboratory – Fall 2012 Purpose In this lab, the concept Frequency Modulation (FM) is investigated. Implementation of FM is primarily done through the use of GNU Radio and the USRP. Both transmission and receiving is investigated. Introduction In communication, modulation is the process of varying one or more properties of a frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted, called the baseband. A modulator is used to modify a carrier to the baseband signal’s parameter (frequency, amplitude, phase, etc.) in accordance signal. Figure 1: Block diagram of modulating a signal There are three types of basic modulation (analog and digital), amplitude (AM), (FM), and phase modulation. The latter two are similar and belong to the class of modulation known as angle modulation. For this lab, we will cover FM. Frequency Modulation (FM) modulates a carrier signal by varying the frequency of carrier signal with respect to the message signal. Over time, the frequency would be varied by an arbitrary factor multiplied the current amplitude of the message signal at that point in time. Since this is the case, the maximum frequency change in the carrier signal is proportional to the maximum amplitude of the message signal. Below we see a general layout of a message signal and the modulated carrier signal Figure 2: Audio Signal and Frequency Modulation
Experiment 3 Frequency Modulation ECE 4117 – Telecommunications Laboratory Fall 2012 Purpose In this lab, the concept Frequency Modulation (FM) is investigated. Implementation of FM is primarily done through the use of GNU Radio and the USRP. Both transmission and receiving is investigated. Introduction In communication, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted, called the baseband. A modulator is used to modify a carrier signal’s parameter (frequency, amplitude, phase, etc.) in accordance to the baseband signal. Figure 1: Block diagram of modulating a signal There are three types of basic modulation (analog and digital), amplitude (AM), frequency (FM), and phase modulation. The latter two are similar and belong to the class of modulation known as angle modulation. For this lab, we will cover FM. Frequency Modulation (FM) modulates a carrier signal by varying the frequency of carrier signal with respect to the message signal. Over time, the frequency would be varied by an arbitrary factor multiplied the current amplitude of the message signal at that point in time. Since this is the case, the maximum frequency change in the carrier signal is proportional to the maximum amplitude of the message signal. Below we see a general layout of a message signal and the modulated carrier signal Figure 2: Audio Signal and Frequency Modulation
Experiment%203_fm.docx