249 results about "Frequency agility" patented technology

A waveform adaptive transmitter that conditions and/or modulates the phase, frequency, bandwidth, amplitude and/or attenuation of ultra-wideband (UWB) pulses. The transmitter confines or band-limits UWB signals within spectral limits for use in communication, positioning, and/or radar applications. One embodiment comprises a low-level UWB source (e.g., an impulse generator or time-gated oscillator (fixed or voltage-controlled)), a waveform adapter (e.g., digital or analog filter, pulse shaper, and/or voltage variable attenuator), a power amplifier, and an antenna to radiate a band-limited and/or modulated UWB or wideband signals. In a special case where the oscillator has zero frequency and outputs a DC bias, a low-level impulse generator impulse-excites a bandpass filter to produce an UWB signal having an adjustable center frequency and desired bandwidth based on a characteristic of the filter. In another embodiment, a low-level impulse signal is approximated by a time-gated continuous-wave oscillator to produce an extremely wide bandwidth pulse with deterministic center frequency and bandwidth characteristics. The UWB signal may be modulated to carry multi-megabit per second digital data, or may be used in object detection or for ranging applications. Activation of the power amplifier may be time-gated in cadence with the UWB source thereby to reduce inter-pulse power consumption. The UWB transmitter is capable of extremely high pulse repetition frequencies (PRFs) and data rates in the hundreds of megabits per second or more, frequency agility on a pulse-to-pulse basis allowing frequency hopping if desired, and extensibility from below HF to millimeter wave frequencies.

A Frequency Agile Electrically Small Tactical AM Broadcast Band Antenna System (NC#098978) comprising a transmitter, antenna, plurality of mast wires and configurable tophat assembly. The transmitter is designed to transmit radio frequency signals. The antenna tuning unit is operatively coupled to the transmitter and designed to tune the apparatus to a desired frequency. The plurality of mast wires operatively is coupled to the antenna tuning unit and designed to receive and output radio frequency signals. The configurable tophat assembly is operatively coupled to the plurality of mast wires. The configurable tophat assembly comprises a tophat disc comprising a conductive material, a plurality of tophat wires comprising a conductor material and a plurality of tophat jumpers designed to help configure said plurality of tophat wires to different lengths by providing electrical open and electrical short states.

The invention discloses a vehicle-mounted millimeter-wave radar moving target recognizer. The vehicle-mounted millimeter-wave radar moving target recognizer is characterized in that the recognizer is a frequency synthesizer; a frequency agility continuous signal is modulated into a pulse signal and then is processed into a millimeter-wave signal by up-conversion; after being amplified by a power amplifier, the millimeter-wave signal is transmitted out; an antenna receives a radar echo signal back to a circulator and then the signal is transmitted into a frequency mixer; a high-frequency echo pulse and constant-amplitude high-frequency voltage generated by a high-stability local oscillator are mixed and the signal is reduced to a middle frequency and then is processed by a middle-frequency amplifier; the middle-frequency signal is directly sampled by an A/D (Analogue/Digital) conversion module; after being sampled, echo signals of a whole pulse string are stored into a storage unit; and information of targets, such as quantity, speed and direction, is measured by a signal processing unit and then is transmitted to an alarm executing unit. With the adoption of the structure, the vehicle-mounted millimeter-wave radar moving target recognizer has the advantages that 1 the distance measuring precision and the angle measuring precision of a moving target are improved; and 2 excessive hardware does not need to be added and the production cost is lower.

A distributed block frequency converter that combines multiple channel signals into a combined radio frequency (RF) signal suitable for transport via selected media. The converter includes combiners that each combine at least two channel signals into a combined channel signal, an up-converter synthesizer that generates an up-converter local oscillator (LO) signal, up-converter mixers that each mix a combined channel signal with the up-converter LO signal to provide a corresponding intermediate frequency (IF) signal, bandpass filters that each filter an IF signal, down-converter synthesizers, down-converter mixers that each mix a down-converter LO signal with a corresponding filtered signal to provide a corresponding RF signal, and an RF combiner that combines the RF signals into a single RF signal. The down-converter synthesizers are adjustable to achieve frequency agility on a block by block basis.

A frequency agile cable modem termination system which is configured to receive cable TV or other broadband signals on a frequency allocated basis. Cable TV headend may receive cable TV modem or other signals via optical/electrical converters and other links, and route those signals through a frequency multiplexer to divide individual feeds into separated frequency slots. The cable modem termination system may then have receivers tuned to individual slots allocated to data feeds, such as Internet, video, telephony or other sources, and route those sources over the Internet. Upon a failure condition within any given receiver or other component, a backup cable modem termination system, connected to the same common bus as the main or active system, may be rapidly activated by having backup receivers contained in that unit tuned to appropriate frequencies to pick up the signals within the corresponding band. Reliability and robustness is increased, and cabling requirements are decreased.

The present invention provides a method and an apparatus for controlling a Q-factor for a filter. The method comprises stabilizing an active feedback to provide a variable feedback in a filter, varying the active feedback based on an input signal to the filter, and producing a desired Q-factor for the filter at a first frequency band, in response to the variable feedback. The method further comprises reconfiguring a center frequency and a bandwidth of the filter based on a channel bandwidth of the input signal to the filter to adjust the Q-factor for the filter in response to a second frequency band different than the first frequency band. By reconfiguring a center frequency and a bandwidth of a filter, the Q-factor for the filter, such as a flexible or reconfigurable filter, may be controlled across a multiplicity of frequency band signals. Using software, for example, a common signal path may be provided for the multiplicity of frequency band signals within a frequency agile radio of a base station by tuning the radio based on a variable feedback through realization of a negative parallel resistance. Thus, tuneability of the Q-factor may provide frequency agile radios that include flexible or reconfigurable filters in a base station to serve different frequency bands without changing hardware. In this way, significant savings associated with frequency agility may be obtained.

Systems and methods are disclosed for an electronically adjustable signal filter system, which comprises, in some embodiments, a first filter coupled to an antenna coupling network and a second filter, a power amplifier coupled to the first filter, an antenna connected to an antenna coupling network, a pilot tone generator coupled to the first filter, and a first signal source connected to the power amplifier and first filter. In some embodiments, the power amplifier amplifies the first signal, the first filter places a notch into the first signal transmitted to the antenna coupling network, the antenna coupling network combines the first signal and a second signal received from the antenna and transmits a third signal to the second filter.

A bandwidth usage control methodology uses the clear channel detection and frequency agile functionality of a spectral reuse transceiver to effectively ‘aggregate’ disjoint user channels into an overall bandwidth, the spectral extent of which is at least sufficient to meet a high bandwidth requirement (such as, but not limited to the transmission of data/video), that cannot be realized by a conventional, single channel radio.

A system and method to efficiently use a plurality of ‘receivers’ to monitor a larger plurality of ‘sources’ for audio content. Upon identifying that a source is active, one of the plural receivers is assigned to convey the content to a destination. All other receivers are prevented from monitoring that specific source for the duration of its activity, but continue to monitor the remaining sources. ‘Source’ includes any source of information containing audio content. ‘Receiver’ includes any device capable of selectively conveying such content, including physical switches, hardware or software multiplexers, microphones, radio receivers, or any other means of obtaining such content.

Cooperating mobiles (ground vehicles, aircraft) are located and identified by Multilateration and Automatic Dependent Surveillance-Broadcast (ADS-B) techniques using the frequency band and the format of the Secondary Surveillance Radar (SSR) signals in high traffic situations. Standard messages, transmitted by the mobile on the downlink channel, i.e. to a set of fixed receiving stations, and including the identification code, permit the location of the mobile by multiple time measurements (Multilateration) from a subset of the set of fixed receiving stations; when the message contains the position (GPS and, later, Galileo datum) the mobile may be located with the ADS-B when in view even of a few stations or of a single station. In order to overcome the problem that arises with high traffic, i.e. the superimposition of signals, called garbling.

The invention discloses a velocity ambiguity resolving method based on a coherent frequency agile radar. Through the method, the problem that target detection is not accurate due to distance-velocityambiguity in pulse radar system signal processing is solved. According to the implementation method, a radar pulse echo signal is received; a baseband pulse echo signal sampling matrix is obtained; pulse compression is performed; a radar Doppler vector group is constructed; Doppler offset frequency is determined, and the velocity of a motion target is calculated; velocity ambiguity resolving is performed on the radar pulse echo signal; and target detection is performed through sparse recovery. According to the method, the accurate velocity of the motion target is calculated through the Dopplervector group, velocity phase compensation is performed on the radar pulse echo signal to realize velocity ambiguity resolving, and the target is detected through sparse recovery. The method is low ininterception and resistant to interference, the velocity of the motion target can be accurately calculated, complexity is low, and the problem of distance-velocity ambiguity in pulse radar system signal processing can be solved. The method is applied to the field of radar target detection.

The present invention is a hybrid RF-digital signal processor-based filter for multiband radio architectures, systems capable of spectrum re-farming and software defined radios It performs low-loss frequency agile multiple notch filtering at RF where a large dynamic range exists at a filter input between signals in a stopband and passband It is a frequency dependent signal attenuation apparatus having two paths connected together by directional couplers The first path comprising a component such as a delay component or duplexer The second path comprising, in series, a down converter, a digital filter, an up converter, and a bandstop filter At the output of a power amplifier, the invention can be used to attenuate spurs, or noise within bands with strict emission constraints At the input of a low noise amplifier, the invention can be used to attenuate blockers and transmitter noise outside of the receiver passband.

The invention discloses a broadband receiving digital waveform formation method based on dechirp processing and two-time time delays. A DDS is designed by use of a polyphase processing technology in an FPGA, by use of two double-accumulators and a CORDIC algorithm, digital band-based signals of broadband chirp signals are generated, and then interpolation filtering upconversion digital-to-analog conversion is carried out; a digital time delay filer is designed; by use of externally input reference clock signals and frequency agility local oscillator signals, first and second local oscillator signals are generated; an antenna array receives radar echo signals and performs frequency mixing filtering with the first local oscillator signals and the second local oscillator signals through amplitude-limiting amplification; and synthesizing is carried out after digital time delay processing on the signals in a frequency domain so as to form a receiving digital wave beam. According to the invention, by use of phase control and continuously variable digital time delay control, broadband dechirp local oscillator signals are generated, and receiving waveform formation control of broadband signals is realized.