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.

Wireless transmission apparatus, polar modulation transmission apparatus, and wireless communication apparatus

Abstract: A wireless transmission apparatus of multi-mode operation with superior power efficiency is provided. Switches ( 115 and 117 ) are switched over in such a manner that a modulation signal outputted from a wireless GSM/EDGE (UB) signal formation circuit ( 101 - 3 ) of a high-frequency signal processing circuit ( 101 ) is outputted to a high-frequency power amplifier ( 104 ) at the time of output of a GSM modulation signal, and is outputted to a high-frequency amplifier ( 105 ) at the time of output of an EDGE modulation signal. As a result, the EDGE modulation signal is power amplified using a high-frequency power amplifier ( 105 ) for an UMTS modulation signal use that is compatible with regards to the EDGE modulation signal and the maximum output power and presence or absence of envelope fluctuation. It is therefore possible to amplify the EDGE modulation scheme wireless signal with high efficiency.

Detection of combined frequency and amplitude modulation

Abstract: Zwicker [Acustica 6, 356–381 (1956)] proposed that amplitude modulation (AM) and frequency modulation (FM) are coded by a common mechanism. To test this, the detection of simultaneously occurring AM and FM is discussed. In a two‐alternative forced‐choice task, thresholds for detecting AM alone were determined. Then, thresholds for detecting FM were determined for stimuli which had a fixed amount of AM in the signal interval only. The amount of AM was always less than the threshold for detecting AM alone. The FM thresholds depended significantly on the magnitude of the coexisting AM. For low modulation rates (4, 16, and 64 Hz), the FM thresholds did not depend on the relative phase of modulation for the FM and AM. For a high modulation rate (256 Hz) strong effects of modulator phase were observed, which can be explained by assuming that detection of modulation at high frequencies is based on detection of the lower sideband in the modulated signal’s spectrum. In a second experiment, psychometric functions w...

Concise modulation strategies for four-leg voltage source inverters

Abstract: Continuous and discontinuous pulse-width modulation (PWM) schemes and a novel space vector modulation methodology are proposed in this paper for four-leg DC-AC inverters. Using a space vector definition that includes the zero sequence voltage component and partitioning the feasible sixteen modes into two separate sets-one set having zero sequence voltages with positive magnitudes and the other set with the zero sequence voltages with negative magnitudes-the novel space vector implementation technique is determined as also the discontinuous carrier based PWM scheme. For the continuous carrier based PWM scheme, the indeterminate defining output voltage equations expressed in terms of the existence functions of the switching devices are solved using an optimization technique. The modulation schemes determined are shown by experimental results to synthesis any desirable balanced or unbalanced three-phase voltage sets when operating in the linear modulation region.

Digital Pulsewidth Modulation Technique for a Synchronous Buck DC/DC Converter to Reduce Switching Frequency

Abstract: It has been shown that the resolution of a digital pulsewidth modulator (DPWM) can be dramatically increased by either constant on-time modulation control or constant off-time modulation control as compared to that for constant frequency modulation. However, the switching frequency increases dramatically for the constant on/off-time modulation method under heavy/light load conditions, respectively. The increase of switching frequency results in more switching losses and requires a higher performance controller. The objective of this paper is to propose a new digital pulsewidth modulation (PWM) technique with constant on/off-time control for a synchronous buck dc/dc converter in order to reduce the switching frequency and switching losses. Moreover, the switching frequency can be limited to a certain range. Experimental results of the proposed new digital PWM technique are presented for confirmation. It will be shown that the proposed technique can significantly reduce the switching frequency of the converter, thereby improving DPWM resolution and the efficiency.

FM-CW laser radar system

Abstract: A scanning laser radar system utilizing a frequency modulated (fm)-continuous wave (cw) beam to coherently detect echo signal returns from an object in a predetermined region. The frequency of the beam is repeatedly changed as a function of time to produce a symmetrical triangular-shaped frequency modulated waveform. The echo signals received are frequency shifted, as a function of range and Doppler shift, from the signal being transmitted at that time. The frequency shift is detected by homodyning a portion of the instantaneous transmitted signal with the received echo signal to produce an output signal having a frequency which is substantially constant during a portion of the frequency modulation period. The constant frequency portion of the output signal is related to the range and Doppler speed of the target. Target information such as range, Doppler speed, intensity and angle information are derived by processing the output signal. The signal to noise ratio of the output signal is improved by using a frequency modulation period greater than the scanning time across an arc of a size equal to a predetermined multiple of the beamwidth because with such relationship the time duration of the constant amplitude portion of the output signal is increased. Further, with such arrangement, because of the relatively long modulation period, the ambiguity in detection of the range to the target is reduced. The system is particularly useful in terrain following or obstacle avoidance applications.