269 results about "Error vector magnitude" patented technology

An apparatus and a method for reducing an error vector magnitude in an orthogonal frequency division multiplexing (OFDM) receiver. The method includes the steps of inputting a receiving symbol including a guard interval and an effective symbol interval following the guard interval, in which a front portion of the guard interval and a rear portion of the effective symbol interval have windowing intervals corresponding to windowing of a transmitter, and replacing a signal of the rear windowing interval with a signal of an interval between the front windowing interval and the effective symbol interval, thereby outputting a signal of the effective symbol interval, which substitutes for a signal of the rear windowing interval, to a fast Fourier transform (FFT) section.

To provide the quality and reliability of a fiber optic link over a wireless link, network nodes in accordance with the present invention include a link quality management unit, which controls multiple transmission parameters of a wireless interface in response variable link conditions. For example, the link quality management unit of one embodiment of the present invention controls transmission power, modulation, and error correction. In general, a receiving network node provides feedback to a transmitting network node. Thus, in many embodiments of the present invention, the link quality management unit includes a signal quality detector, which measures a signal quality value, such as bit error rate, signal to noise ratio, or error vector magnitude. The measured signal quality is transmitted back to the transmitting node so that appropriate changes can be made to the transmission parameters.

A linear compensation system of a digital TV relay or other apparatus preferably includes a transmitting unit configured to modulate a data to an intermediate frequency (IF) signal, up convert the IF signal to an RF signal, and amplify the RF signal to a predetermined level using a high power amplifier (HPA). The system also includes a linear compensation unit to preferably directly vary a step size of an adaptive equalizer according to whether a signal-to-noise ratio (SNR) or an error vector magnitude (EVM) for an output signal of the HPA satisfies an advanced television systems committee (ATSC) or other standard. The linear compensation unit is thus configured to output an improved linear compensation coefficient to a modulator of the transmitting unit.

A downconverter and upconverter are provided which can obtain a satisfactory image rejection ratio in a low-Intermediate Frequency (IF) scheme while reducing power consumption, and can improve Error Vector Magnitude (EVM) in a zero-IF scheme. A complex-coefficient transversal filter rejects one side of a positive or negative frequency, and converts a Radio Frequency (RF) signal to a complex RF signal configured by real and imaginary parts. A local oscillator outputs a complex local signal in which a set frequency is set as a center frequency. A full-complex mixer, connected to the complex-coefficient transversal filter and the local oscillator, perform a frequency conversion process by multiplying a complex signal output from the complex-coefficient transversal filter and the complex local signal output from the local oscillator, and outputs a complex signal of a frequency separated by the set frequency from a frequency of the RF signal.

A novel and useful apparatus for and method of predistortion compensation of device (e.g., transistor) mismatch in a digital power amplifier (DPA). The device mismatch predistortion mechanism of the present invention addresses the problem of matching between two types of binary weighted transistors, whereby mismatched transistors cause degradation in wideband noise. The invention provides a digital predistortion mechanism which functions to pre-distort the mismatch ratio based on a data table calculated a priori enabling a polar transmitter to meet output spectrum and error vector magnitude (EVM) requirements of the particular modern wideband wireless standard, such as GSM, 3G WCDMA, etc.

Aspects of a method and system for minimizing effects of transmitter impairments in multiple input multiple output (MIMO) beamforming communication systems are presented. In one aspect of a system for minimizing effects of transmitter impairments, a MIMO transmitter may enable nulling of transmitter-induced noise by adjusting at least a portion of a plurality of signals transmitted based on a transmitter error vector magnitude (EVM). The transmitter may enable transmission of the plurality of signals subsequent to the nulling. In another aspect of a system for minimizing effects of transmitter impairments a MIMO receiver may enable nulling of transmitter-induced noise contained in a plurality of received signals based on a transmitter EVM. Each of the plurality of received signals may include information contained in a plurality of spatial streams. The receiver may enable detecting estimated values for the information contained in the plurality of spatial streams based on the nulling.

Systematic transmit IQ phase and amplitude imbalances in the transmit chain of a wireless local area network (WLAN) cause a corresponding systematic shift in the roots of a constellation diagram. Additional random phase noise in the transmit chain will cause a further Gaussian distribution of points in the constellation diagram about the systematically shifted roots. This random distribution represents a true error vector magnitude (EVM). By transmitting a known training sequence through the transmit chain, which it is known will be shifted to all of the systematically shifted roots in the constellation diagram, the Gaussian spread around those shifted roots can be analysed to determine the true EVM.

Apparatus and methods configure digital predistortion linearizers for power amplification of bandlimited signals using non-linear amplifiers. The predistorter is configured to achieve both crest factor reduction (CFR) and predistortion for linearization. One embodiment advantageously reduces processing requirements conventionally associated with CFR by considering only the in-band component, that is, the information bearing component, of the desired signal to be reproduced for those cases in which the mitigation of in-band error vector magnitude (EVM) is preferred over the reduction of spurious out-of-band emissions.

A novel and useful apparatus for and method of reducing phase and amplitude modulation bandwidth in polar transmitters. The bandwidth reduction mechanism of the present invention effectively reduces the phase modulation bandwidth of the polar modulation performed in the transmitter by modifying the zero-crossing trajectories in the IQ domain. This significantly reduces the phase modulation bandwidth while still meeting the output spectrum and error vector magnitude (EVM) requirements of the particular modern wideband wireless standard, such as 3G WCDMA, etc. The mechanism detects a zero crossing or a near zero crossing within a predetermined threshold of the origin and an offset vector is generated that when added to the input TX IQ data, shifts the trajectory to avoid the origin thus reducing the resultant polar modulation amplitude and phase bandwidth.

A device and method for adjusting transmit power in a wireless communication device. The wireless communication device comprises a transmitter having a power amplifier, wherein the amplifier may introduce distortion into the transmit signal. The method may periodically determine an error vector magnitude (EVM) level in the transmitter of the wireless communication device. The EVM level may be determined based on differences between an ideal transmit signal without amplification, and an actual transmit signal with amplification. The method may then adjust one or more transmit gain settings of at least one gain stage of the wireless device based on the measured EVM level in the transmitter. In one embodiment, as the EVM increases, indicating that more distortion is being introduced, the method may reduce the gain settings of the gain stage(s) to reduce this distortion. If the EVM decreases, the method may increase the gain of the gain stage(s).

A downconverter and upconverter are provided which can obtain a sufficient image rejection ratio in a low-Intermediate Frequency (IF) scheme while reducing power consumption and can suppress Error Vector Magnitude (EVM)-related degradation in a zero-IF scheme. A complex-coefficient transversal filter rejects one side of a positive or negative frequency, and converts a Radio Frequency (RF) signal to a complex RF signal configured by real and imaginary parts. A local oscillator outputs a real local signal with a set frequency. A half-complex mixer, connected to the complex-coefficient transversal filter and the local oscillator, performs a frequency conversion process by multiplying the complex RF signal output from the complex-coefficient transversal filter and the real local signal output from the local oscillator, and outputs a complex signal of a frequency separated by the set frequency from a frequency of the RF signal.

Systems and methods are provided for aligning amplitude and phase signals in a polar receiver. A receiver generates digital amplitude and phase signals representing the amplitude and phase of a modulated input signal. At least one of the digital signals is filtered using a fractional delay filter with a variable delay. The delay of the fractional delay filter is adjusted to align the amplitude and phase signals. In some embodiments, an error vector magnitude is determined by comparing in-phase and quadrature values of the signal with values corresponding to a constellation point, and the delay is adjusted based on the error vector magnitude. The fractional delay filter may be a finite impulse response filter with coefficients stored in a lookup table that correspond to different delays.

A method for estimating the error vector magnitude (EVM) of an OFDM signal comprises the steps of obtaining a multi-tone EVM of a separate multi-tone signal, and using the multi-tone EVM to estimate the OFDM EVM. The multi-tone signal is designed to have carriers that occupy a small fraction of OFDM bins, and its EVM is estimated from the ratio of sums of full bin energies and empty bin energies.

Embodiments of methods, transmitters, and computer program products are provided for transmitting a signal by adjusting a delay between an amplitude component of the signal and a phase component of the signal based on the transmission power. Error vector magnitude and adjacent channel power ratio are two common criteria used in evaluating transmitter performance. By adjusting the delay between the amplitude component of the transmitted signal and the phase component of the transmitted signal, the error vector magnitude and/or the adjacent channel power ratio may be reduced. The particular delay value that provides the best error vector magnitude performance and/or adjacent channel power ratio performance may differ based on the transmission power level. Therefore, the delay value is adjusted based on the transmission power.

The embodiment of the invention provides a design method for a cascade filter, which comprises the following steps of: determining the interpolation times N of the filter; calculating the filter coefficient of a programmable finite impulse response (PFIR) filter, and obtaining a design scheme of a cascade combined filter of PFIR and cascaded integrator comb (CIC) filters; and when the interpolation times of the cascade combined filter of the PFIR and CIC filters does not reach the predetermined times, designing a half band (HB) filter, so that the filter performance of the cascade combined filter of the PFIR and CIC filters and the HB filter meets the interpolation times requirement of a system, and the design of the PFIR filter is realized by adopting a multistage design scheme. According to the embodiment provided by the invention, by adopting the design device for the multistage filter, the order of the designed filter is in a realizable range of the FPGA, and the indexes such as interpolation times of signals, error vector magnitude (EVM), adjacent channel power ratio (ACPR) and the like can meet the protocol requirement. Moreover, according to the technical scheme provided bythe invention, the resource consumption of the filter is also lower than that of the design method for the traditional filter, and the use of FPGA hardware resources can be effectively reduced.

A method and apparatus for automated correlation of digital modulation impairment is described. The technique obtains soft decision data (116, 2502) and extracts signal space location information of sufficient resolution to distinguish different types of impairment to a digitally modulated signal. The technique applies an error vector magnitude mask (117, 502) and determines the signal-to-noise ratio of the digitally modulated signal. The technique applies impairment masks (118, 2504) and provides a characterization (119) of impairment affecting the digitally modulated signal (112). The technique determines a subset of the soft decision data (116, 2502) that falls within the impairment masks (118, 2505) and calculates correlation weights (2506). The technique may be used to identify, isolate, and classify different types of impairment. Given sufficient data collection, sources of impairments may be determined precisely.

The invention is suitable for the field of TD-SCDMA communication, and provides a method for adaptively adjusting CFR threshold and a radio frequency zooming system. The method comprises the following steps that: A, capturing a downlink time slot signal from signals fed back to digital pre-distortion (DPD) from power amplification; B, analyzing and calculating an output index of the power amplification from the time slot signal, wherein the index at least comprises an error vector magnitude (EVM); and C, judging whether the index meets the preset standard, and if so, returning and carrying out the step A, otherwise, according to the preset stepping, adjusting the CFR threshold and returning to carry out the step A. The method can detect the index of the PA output signal in real time by utilizing a feedback loop of the DPD, and adaptively adjusts the CFR threshold according to the index to achieve the optimization of the power amplification performance.

Devices and methods for correcting for start-up transients in integrated power amplifiers are disclosed. A delay element is arranged to produce a delay waveform signal that is responsive to an input voltage signal. A transconductance element has an input that receives the delay waveform signal and is arranged to provide an output boost current that is based on the delay waveform signal and a gain of the transconductance element. A reference element provides an output bias current that is responsive to a static reference current and the boost current. A bias element has an input that receives the bias current and is arranged to provide a bias control output. A power amplifier is responsive to the bias control output and is arranged to provide an amplified power output. In some examples, the boost current is adjusted based on a supply voltage and an input power of the power amplifier.

A method and a device for reducing a signal peak value are adapted to solve a problem that overall performance of a system is significantly degraded caused by allocating a same weight to each sub-carrier so as to averagely distribute a peak clipping noise to each sub-carrier. The method includes: receiving a signal (21); and performing a peak clipping processing on the received signal by using a peak clipping signal (25). The peak clipping signal is formed according to a peak clipping weight factor and the received signal, or according to a frequency domain error vector magnitude (EVM) and the received signal. In the method, a weight of each sub-carrier is set according to the peak clipping weight factor or the frequency domain EVM during the peak clipping processing, thereby improving the overall performance of the system.

The embodiment of the invention discloses a receiver and an image suppression method thereof; after the receiver is electrified, a reference signal is input into a down link; the reference signal is processed by the down link and then is processed by an up link, and in-phase/quadrature (I/Q) data is obtained; the autocorrelation, the cross-correlation, the summing and averaging and an image correction coefficient of the obtained I/Q data are sequentially calculated, and the image correction coefficient is obtained; and the reference signal is finally cut off. Consequently, when in normal communication, after a radio frequency signal is processed by the up link, an image can be corrected according to the image correction coefficient. The method is particularly applicable to a homodyne receiver; the reference signal is preferred to be a white noise signal; and after primary image correction of an uplink homodyne modulator, the radio frequency signal carries out secondary image correction according to the image correction coefficient. Finally, the image can be corrected to -70dbm, and the error vector amplitude, in-band stray, sensitivity and other indicators of a system are improved.

The invention discloses a digital signal error vector magnitude testing method, a digital signal error vector magnitude testing device and a digital signal error vector magnitude testing system, wherein the digital signal error vector magnitude testing method includes the following steps: filtering down-sampled digital signals to obtain digital signals to be tested; obtaining standard modulation signals corresponding to the digital signals to be tested; according to the standard modulation signals and the digital signals to be tested, determining the error vector magnitude deviation of each symbol of the digital signals to be tested, and according to the error vector magnitude deviation of each symbol and the standard modulation signals, determining error vector magnitude. Since the embodiment of the invention integrates the test and calculation of error vector magnitude, the efficiency of obtaining error vector magnitude can be increased.