All articles starting with F
15,892 articles
Frequency offset estimation
Frequency offset estimation is a signal processing method in digital communications that measures the carrier frequency offset between a transmitter's and receiver's oscillators so it can be corrected before demodulation.
Frequency response
Frequency response, also called the frequency response function, is the description of how a linear system alters the magnitude and phase of sinusoidal inputs as frequency varies.
Frequency reuse
Frequency reuse is the use of the same radio channels in different areas separated enough that co-channel interference is not objectionable, a core element of the cellular concept.
Frequency selective surface
A frequency selective surface (FSS) is a planar periodic array of metallic patches or apertures on a dielectric substrate that transmits or reflects waves depending on frequency.
Frequency signal injection
Frequency signal injection is a sensorless control technique that superimposes a high-frequency signal on a motor drive to estimate rotor position without a sensor, working even at standstill.
Frequency spinal cord stimulation
Frequency spinal cord stimulation (SCS) is a neuromodulation therapy that delivers tonic electrical pulses to the spinal cord to relieve chronic, intractable pain of the trunk and limbs.
Frequency stability
Frequency stability is a power system's ability to maintain steady frequency after a severe generation-load imbalance, like losing a large generator, and restore it to nominal value.
Frequency synthesis
Frequency synthesis is an electronic design technique that generates signals at desired frequencies from one or more reference oscillators, using phase-locked loops, direct digital synthesis, and related loop-based architectures.
Frequency synthesizer
A frequency synthesizer is an electronic circuit that generates a range of frequencies from a single stable reference, used in radios, televisions, and GPS systems.
Frequency Therapeutics
Frequency Therapeutics was a Massachusetts clinical-stage biotechnology company, founded in 2014, that developed progenitor cell activation therapies for hearing loss before merging into Korro Bio in 2023.
Frequency-bin entanglement
Frequency-bin entanglement is a form of quantum entanglement where photon pairs share correlations across discrete frequency bins rather than polarization or paths, used for fiber-based quantum key distribution.
Frequency-comb spectroscopy
Frequency-comb spectroscopy uses a laser frequency comb, a spectrum of precisely known equidistant lines, as the light source for broadband, high-resolution measurement of atomic and molecular spectra.
Frequency-dependent squeezing
Frequency-dependent squeezing is a quantum-optics technique that rotates the squeezing angle of injected squeezed light with frequency to cut quantum noise across a gravitational-wave detector's whole band.
Frequency-dependent squeezing in gravitational-wave detectors
Frequency-dependent squeezing is a quantum-optical technique used in LIGO and Virgo that reduces both shot noise at high frequencies and radiation pressure noise at low frequencies.
Frequency-division multiple access
Frequency-division multiple access (FDMA) divides the radio spectrum into non-overlapping frequency slots, one per user, and was the first multiple access technique in satellite communications.
Frequency-division multiplexing
Frequency-division multiplexing (FDM) is a technique that carries multiple independent signals over one shared medium by assigning each its own frequency band, separated by guard bands.
Frequency-domain equalization
Frequency-domain equalization is a receiver technique that compensates for inter-symbol interference using FFT-based processing instead of long time-domain filters, with single-carrier FDE comparable to OFDM.
Frequency-domain equalizer
A frequency-domain equalizer (FDE) is a receiver technique that compensates for intersymbol interference by equalizing each FFT-transformed block of samples, one coefficient per frequency bin.
Frequency-hopping spread spectrum
Frequency-hopping spread spectrum (FHSS) is a radio transmission method whose carrier hops rapidly among many channels in a pseudorandom sequence known to both transmitter and receiver.
Frequency-locked loop
A frequency-locked loop (FLL) is a feedback control circuit that adjusts a variable-frequency oscillator until its output frequency matches a reference signal, controlling frequency only, not phase.
Frequency-modulated continuous-wave
Frequency-modulated continuous-wave (FMCW) LiDAR is a coherent laser ranging technique that sweeps a continuous laser's frequency, measuring both distance and velocity from the beat signal.
Frequency-modulated continuous-wave radar
Frequency-modulated continuous-wave radar, or FMCW radar, sweeps the transmitted frequency and derives range from the beat frequency with the echo, with simultaneous transmission giving Doppler velocity.
Frequency-modulation atomic force microscopy
Frequency-modulation atomic force microscopy (FM-AFM) is a dynamic AFM mode, introduced in 1991, that measures tip-sample forces through resonance-frequency shifts and achieves true atomic resolution in vacuum and liquid.
Frequency-resolved optical gating
Frequency-resolved optical gating (FROG) is an ultrafast optics technique that measures the full intensity and phase of an ultrashort laser pulse, replacing rough autocorrelation estimates with complete characterization.
Frequency-shift keying
Frequency-shift keying (FSK) is a digital modulation scheme in which bits are sent as discrete frequency shifts of a carrier, used in modems, GSM, Caller ID, and Bluetooth.
Frequent episodic tension-type headache
Frequent episodic tension-type headache (ICHD-3 2.2) is a primary headache with bilateral, pressing, mild-to-moderate attacks on 1-14 days/month for >3 months; treated with simple analgesics and, if disabling, preventives such as amitriptyline.
Frequent menstrual bleeding
Frequent menstrual bleeding (frequent menses, ICD-11 GA20.10) is a FIGO-defined abnormal uterine bleeding symptom: cycles shorter than 24 days, more than four episodes in 90 days, usually from ovulatory dysfunction.
Frequent micturition
Frequent micturition (urinary frequency, ICD-11 MF50.0) is urinating many times day or night in normal or small volumes, unlike polyuria (>3 L/day); common causes include UTI, BPH, incontinence, calculi, and overactive bladder.
Frequent-flyer program
A frequent-flyer program (FFP), or flyer miles, is an airline loyalty scheme where passengers earn points for travel and purchases, redeemable for flights, upgrades, and rewards.
Frequentis
Frequentis is an Austrian technology company founded in Vienna in 1947 that develops communication and information systems for safety-critical control centers in air traffic management, public safety, and transport.