Pulse-frequency modulation

About: Pulse-frequency modulation is a research topic. Over the lifetime, 4151 publications have been published within this topic receiving 53039 citations. The topic is also known as: PFM.

Analysis of different modulation techniques for multilevel inverters

Abstract: Analysis of different modulation techniques for multilevel inverter is discussed. To control the multilevel inverters, different modulation techniques have been used. Amongst them multi carrier Sine Pulse Width Modulation (SPWM) techniques are widely used for different multilevel inverter topologies. These modulation techniques are derived from the conventional two level inverter SPWM technique. Different modulation techniques are compared on the basis of the output THD, utilization of DC link voltages and common mode voltage. The detailed analysis of modulation techniques are shown on the basis of the output THD offered by the five level Neutral Point Clamped or Diode Clamped (NPC) inverter.

Design and implementation of visible light communication system using pulse width modulation

Abstract: Visible Light Communication (VLC) is a relatively new technology which could potentially be complementary to the existing radio frequency communication system. VLC allows lamp or other kinds of light source not only used as illumination, but also as a data transmission at the same time. Single carrier modulation technique is suitable to be applied on VLC that does not require high-speed data transfer. In this paper, we proposed a visible light communication scheme using pulse width modulation (PWM) technique in transmitting data for running text application. To evaluate the PWM accuracy, experiments were conducted based on different parameters such as PWM frequency, transmitter-receiver distance, and the receiver's angle of view. Furthermore, we also measured the point-to-point communication system performance which resulted in 920 bps data transfer rate and 10−4 bit error rate (BER) without affecting the lighting function.

Amplitude-modulated noise: the detection of modulation versus the detection of modulation rate.

Abstract: Modulation threshold, that is, the modulation depth required to discriminate a sample of amplitude‐modulated (AM) noise from a sample of unmodulated noise, was measured as a function of modulation rate (16–320 Hz), modulator waveform (sine or square), and the bandwidth of the AM noise (0.5–8.0 kHz). Modulation threshold increases monotonically with modulation rate, sine‐wave thresholds are greater than square‐wave thresholds, and threshold rises as the bandwith of the AM stimulus decreases. These effects all support the use of some form of energy detection model to explain modulation threshold. The modulation thresholds were compared with pitch thresholds gathered under precisely the same conditions. Pitch threshold or, alternatively, rate threshold was taken to be the modulation depth required to decide which of two samples had the higher modulation rate; the rate difference was 20%—just over three semitones. In the region above about 70 Hz, rate threshold is essentially a constant multiple of modulation threshold, indicating that the primary constraint on rate threshold is the audibility of the modulation. Below 70 Hz, rate and modulation threshold diverge; it is argued that the limit on rate threshold in this region is probably the length of the correlation required to extract the periodicity.

EMI reduction of power converters by way of controlled randomized modulation of oscillating signals

Abstract: A switching control circuit for a switching power converter utilizes an oscillating signal that causes reduced electromagnetic interference by the power converter by way of modulating the frequency of the oscillating signal within a specified frequency range. An output voltage monitor circuit monitors the output voltage of the power converter, thus producing an output voltage monitor signal. Also, a randomized signal generator creates a randomized signal, which is then used to drive a frequency range converter that is employed to produce a frequency modulation signal. The current state of the frequency modulation signal is based on the current state of the randomized signal, with the frequency range converter limiting the current state of the frequency modulation signal so that the oscillating signal will only operate within the specified frequency range. A variable frequency oscillator then generates the oscillating signal whose frequency is based on the current state of the frequency modulation signal. A comparator then compares the oscillating signal with the output voltage monitor signal to produce a switch control signal, which is then employed to control a switching element of the power converter.