52 results about "Maximum usable frequency" patented technology

The invention relates to an aircraft target detection method under a radar scanning mode in wind turbine clutter background. The method includes the following steps that: radar multi-scanning data of wind turbine clutter are obtained through utilizing apriori information, and the maximum Doppler frequency of wind turbine blades is estimated according to the data; super resolution technology is introduced for the obtained radar scanning data, so that frequency resolution can be improved; Hough transform is performed on radar echo data which have been subjected to super resolution processing, so that whether the wind turbine blades are vertical to radar beams can be detected, if the wind turbine blades are vertical to the radar beams, whether an aircraft target exists is further detected, otherwise, the possible Doppler frequencies of the tips of the wind turbine blades and the aircraft are estimated through utilizing the power spectrum of the radar echoes which have been subjected to the super resolution processing; the possible Doppler frequencies are compared with the calculated value of the Doppler frequency of the tips of the wind turbine blades; and whether the aircraft target exists in a range gate can be judged according to a comparison result. With the method of the invention adopted, a situation in which only wind turbine clutter exist and a situation in which aircraft and wind turbine clutter co-exists can be distinguished, and aircraft target detection under wind turbine clutter background with any blade initial angle can be realized.

In a CDMA transmission power control system for controlling reverse transmission power of reverse transmission power for a mobile station, a Doppler frequency detector (50) detects a maximum Doppler frequency using a pilot symbol extracted from a desired transmission data signal per transmission power control period. When the maximum Doppler frequency is smaller than a Doppler frequency threshold, the system performs a closed loop control in a cycle of the transmission power control period. On the other hand, when the maximum Doppler frequency is larger than the Doppler frequency threshold, the system performs the closed loop control in a cycle of N times the transmission power control period in appearance.

The invention relates to a device for predicting the maximum usable frequency (MUF) of a short-wave communication, comprising a user input module, an environmental model module, a space distribution module for establishing a refractive index according to a magnetoionic theory, a ray tracking characteristic calculation module and a predicated maximum usable frequency expansion module; the calculation method for predicting the maximum usable frequency of the short-wave communication comprises the seven steps of: 1. confirming an initial value of a ray equation; 2. establishing electronic concentration distribution by utilizing international feference ionosphere (IRI); 3. introducing a geomagnetic field model of International geomagnetic reference field (IGRF) and establishing a function relation; 4. solving a differential equation; 5. extracting ray parameters that reach the ground; 6. screening ray tracking results; and 7. selecting 85 percent of MUF as the frequency used by the short-wave communication. The invention solves the method for acquiring form parameters of the ionized layer model and establishes the electronic concentration distribution over the position according to longitudes and latitudes at any time and place. The invention has wide practical value and application prospects in the technical field of short-wave communications.

Method for designing a converted mode (PS or SP) seismic survey to accomplish specified vertical and lateral resolution objectives at target depth. An equation (181) is provided for determining the minimum bandwidth required for a desired vertical resolution at a selected scattering angle, as a function of incident and reflected wave velocities, one of which is the P-wave velocity and the other is the S-wave velocity. A second equation (182) is provided for determining migration acceptance angle from the desired vertical and lateral resolutions. Source and receiver apertures may then be determined by ray tracing. Finally, a third equation (183) is provided for the maximum bin size to avoid aliasing, given the migration acceptance angle and a maximum frequency needed to achieve the bandwidth requirement. Source and receiver spacing may then be based on the maximum bin size.

There are provided an inspection device, an inspection method, and an inspection program for accurately inspecting a minute structure having a movable portion by using a simple method. A test sound wave is inputted and frequency characteristic of a sensor output voltage amplitude responding to the input of the test sound wave is analyzed. The maximum frequency and the minimum frequency of the device is calculated from estimated use conditions and it is judged whether it is possible to detect a desired characteristic in the frequency band. More specifically, the device is judged to be good or bad depending whether the response characteristic in a predetermined frequency band exceeds the minimum characteristic level as a threshold value.

The invention discloses a synchronization self-adaptation short-wave communication frequency-selecting method based on ionized layer data. The synchronization self-adaptation short-wave communication frequency-selecting method based on the ionized layer data comprises the step one that the maximum usable frequency of a channel is obtained by utilizing the ionized layer data according to short-wave communication link timing, wherein the ionized layer data comprise real-time observational data, historical data and the like; the step two that the range of usable frequency is determined according to the maximum usable frequency and by combining communication efficiency and/or duration of passable frequency; the step three that the range of the usable frequency is sent to a synchronization self-adaptation short-wave communication system; the step four that the synchronization self-adaptation short-wave communication system obtains the optimum usable frequency by scanning the range of usable frequency in a synchronization self-adaptation frequency-selecting mode, and then communication can be carried out. The synchronization self-adaptation short-wave communication frequency-selecting method based on the ionized layer data can overcome the defect in the prior art that the efficiency is low or it is difficult to obtain the optimum usable frequency due to the fact that channel information needs to be set in advance, and can efficiently select the optimum communication frequency. Thus, the synchronization self-adaptation short-wave communication frequency-selecting method based on the ionized layer data has an obvious effect on improvement of comprehension effectiveness of short-wave data communication.

The invention relates to an LED display enabling signal control system. High-frequency display enabling signals in display enabling signals are overlapped in low-frequency display enabling signals to be together transmitted, the transmission frequency is greatly reduced, the low-frequency display enabling signals adopt a carrier similar mode to transmit high-frequency display enabling signals, influences by transmission frequency limitation between LED display units do not exist, signals whose frequency does not exceed the transmission frequency limitation can be used between the LED display units to transmit display data of higher frequency or a lower gray level, and thus, the LED display system refreshing rate is improved. A frequency dividing circuit is used for separating the high-frequency display enabling signals and the low-frequency display enabling signals which are overlapped together before, recovery of the high-frequency display enabling signals and the low-frequency display enabling signals in the LED display unit can be realized, and in the maximum clock frequency of a crystal oscillator adopted by the LED display system, the minimum output disabling width can be adjusted randomly, and a higher display refreshing rate and a higher gray level can be realized.

The invention discloses a portable wireless snore monitoring system. The system comprises an upper computer and a lower computer which are in wireless communication; the lower computer comprises a collecting device and is used for collecting snore data; the upper computer comprises a data analysis device and is used for obtaining the snore data in a wireless communication mode and analyzing a snore signal to obtain the maximum snoring amplitude, and the maximum snoring frequency per 30 min, amplitude distribution, the total number of snoring, the number of snoring per hour and parameters of the number of meeting a sleep apnea syndrome and can judge severity of snoring and whether a lesion occurs or not. According to the technical scheme, the portable wireless snore monitoring system has the advantages of being low in cost, easy to operate, easy to use, friendly to human and machine and suitable for measurement in an environment of sleeping at home.

The invention discloses a maximum usable frequency calculating method for shortwave links during ionospheric storms. The method comprises the steps that 1 five high-quality oblique links are preferably nationwide and are used as background links; 2 fof2, foE and M(3000)F2 factors of vertical survey data of 14 radio wave observing stations in China are used; 3 three vertical survey data and the oblique link maximum usable frequency MUF data of the midpoint of five background links during historical ionospheric storms are acquired; and 4 the vertical survey data, which are interpolated in the step 3, of the midpoint of the links during ionospheric storms are used as the input in the ITU-R P533 recommended calculation formula of the maximum usable frequency of shortwaves. According to the maximum usable frequency calculating method for shortwave links during ionospheric storms, the maximum usable frequency of shortwave links during ionospheric storms is acquired; and based on the ITU-R P.533 recommended shortwave link maximum usable frequency calculating formula, the ionospheric state information during ionospheric storms is combined to establish the maximum usable frequency calculating method suitable for shortwave links during ionospheric storms.

The invention discloses a time domain measuring method of linear modulation frequency signal frequency characteristic parameters. The method includes; performing waveform shaping and level conversionon a measured linear frequency modulation signal by employing a high-speed comparator, and then inputting the shaped and converted digital square wave signal to a field programmable gate array (FPGA)for calculation and measurement; in the FPGA, performing time interpolation on a clock signal by employing an on-chip phase-locked loop of the FPGA, counting the digital square wave signal and a reference clock signal through a counter, performing parameter fitting by employing the least squares method, and obtaining an average frequency value of the measured linear frequency modulation signal ina basic time slice interval; and then obtaining an instantaneous frequency expression of the measured linear frequency modulation signal through a least-squares fitting mode according to the average frequency value obtained by a series of measurements so that parameters including the sweeping frequency rate, the maximum frequency and the minimum frequency are calculated.

The maximum frequency and the minimum frequency are extracted from frequencies corresponding to respective axle speeds. The minimum frequency is subtracted from the maximum frequency to achieve a first frequency deviation, and also the first frequency deviation is input as a primary delay system to achieve a second frequency deviation. Furthermore, the second frequency deviation is subtracted from the first frequency deviation to achieve an idle running detection setting deviation, and also an idle running detection set value for judging the idle running of the wheels at the frequency level is achieved. The idle running frequency deviation and the idle running detection set value are compared with each other to output an idle running detection signal, and also a torque correction amount of an AC electric motor is calculated on the basis of the idle running detection signal.

The invention provides a transceiver circuit for communication that enhances the operation frequency of a synchronous digital circuit up to the maximum frequency of a flip-flop and inhibits the occurrence of jitters.

A clock signal synchronized with data at f1/n Hz is converted by a multiplier so that the signal has a frequency of “n” times so as to use the clock signal for triggering a flip-flop the operation frequency of which is f1 b/s in the synchronous digital circuit. The multiplier is arranged in the vicinity of the flip-flop triggered by the clock signal of f1 Hz so as to avoid the effect of the deterioration of the operation frequency by interconnect capacitance.

The maximum operation frequency of the transceiver circuit determined based upon the operating frequency of the synchronous digital circuit can be enhanced up to the maximum operation frequency of the flip-flop. As a margin can be produced in designing a frequency band of a clock signal processing circuit, the reduction of power consumption, the reduction of phase noise and the extension of a control frequency range can be realized.

The present invention is directed to data communication. More specifically, embodiments of the present invention provide a method for acquiring sampling frequency by sweeping through a predetermined frequency range, performing data sampling at different frequencies within the predetermined frequency range, and determining a target frequency for sampling data based on a maximum early peak frequency and a maximum late peak frequency. There are other embodiments as well.

In the course of the channel presetting process, the central frequency is set by a step of 1 MHz within the range from the minimum frequency in the VHF band channel plan to the maximum frequency of the VHF band adopted in the place of destination for the scheduled shipment of the TV broadcast receivers, attempts are made to detect broadcast signals by changing frequency within a range of 1.5 MHz to the high frequency side and 0.5 MHz to the low frequency side from the central frequency, and the frequencies of the detected broadcast signals are stored in the semiconductor memory.

The invention discloses a frequency expansion device and a radio frequency system. The frequency expansion device comprises a straight-through channel for receiving and outputting a first radio frequency input signal of a first frequency band and a spread-spectrum channel for receiving a second radio frequency input signal of a second frequency band and outputting a spread-spectrum signal of a third frequency band, the maximum frequency of the third frequency band being greater than the maximum frequency of the first frequency band. By setting the frequencies of the first radio frequency inputsignal and the second radio frequency input signal to be smaller than the set frequency, attenuation of the spread spectrum signal output from the frequency spreading device can be reduced. At the same time, the spread spectrum channel in the frequency spreading device can spread the second radio frequency input signal in the second frequency band, so that the spread spectrum channel in the frequency spreading device can output the spread spectrum signal in the third frequency band, thereby increasing the frequency range of the spread spectrum signal output by the frequency spreading device.