Telefonaktiebolaget Lm Ericsson (publ)

Spendim Dalipi

Richard Hellberg

Mark William Wyville

Mats Klingberg

Lars Johan Thorebäck

Tony Fonden

Jin Ellgardt

Yi-Pin Eric Wang

Yutao Sui

Asbjörn Grövlen

Jim Svensson

Dominique Everaere

Johan Thorebäck

Haiying Cao

Kenneth Sandberg

Per Landin

Tony Fondén

Stefan Hamrin

Tobias Johansson

Mats Gan Klingberg

Asbjörn GRÖVLEN

Tony FONDÉN

Systems and methods for handling cancellation of a Passive Intermodulation (PIM) signal are provided. The network device has access to and controls one or more transmitters and one or more receivers. The network device applies a determined PIM model to a transmitted signal from each transmitter of the network device, to obtain a modelled signal. The PIM model comprises a forward path model for each transmitter to the PIM source, a common non-linear model of the PIM signal from the PIM source being applied to a combined signal comprising the signals from each transmitter modelled by the forward path model, and a linear reflective path model from the PIM source to each of the receivers of the network device for a received PIM signal. The network device further subtracts the modelled signal from a received signal on each of the receivers of the network device.

Network device and method therein for handling passive intermodulation signals in a wireless communications network

There is provided mechanisms for PIM removal in an antenna system. A method is performed by a controller of the antenna codebook based beamforming, which transmission radio chains of the antenna system that cause a signal received by receiver radio chains of the antenna system to be impacted by PIM. These transmission radio chains are identified based on which codeword in the codebook is used for the beamforming. The method comprises determining a correction signal by subjecting the signals only as transmitted by the identified transmission radio chains to a model of the PIM. The method comprises removing PIM from the signal received by the receiver radio chains by subtracting the correction signal from the signal received by the receiver radio chains.

Removal of passive intermodulation in antenna systems

A method and a transmitter arrangement for cancelling cross talk and correcting power amplifier (PA) distortion for a transmitter branch of a multiple-input multiple-output (MIMO) configuration having multiple branches. The method comprises combining an original baseband input signal of a first MIMO transmitter branch with a crosstalk output signal generated from two or more signals associated with two or more respective MIMO branches, the two or more signals used as input to, and processed by, a crosstalk model. The method further comprises processing the combined signal to generate an output signal in order to minimize the error of the original baseband input signal caused by the crosstalk and/or PA distortion.

Low complexity MIMO digital pre-distortion

A wideband carrier (e.g., LTE carrier) is shifted up or down in frequency, within an allocated frequency band, by an integer multiple of the channel raster spacing (e.g., 100 KHz). This reduces the size of the guard band on one side of the carrier, and expands the guard band on the other side. A narrowband carrier (e.g., NB-IoT carrier) is then deployed within the expanded guard band, at or near a frequency such that the transmission is orthogonal to the wideband carrier transmissions, such as by using a shared N frequency grid spacing (e.g. at 100 KHz spacing, and using 15 KHz subcarriers). The narrowband carrier thus maintains orthogonality with the wideband carrier, but has 'room' within the expanded guard band to both transmit on a frequency close to the frequency grid spacing, and to boost transmit power (e.g., by 6 dB), while remaining within the spectral mask. The shifted wideband carrier is transparent to wideband UEs, as the frequency shift is an integer multiple of the channel raster spacing.

Narrowband service deployment in wideband carrier guard-band

Systems and methods for suppressing transmitter noise in a receive band of a co-located receiver that are suitable for wideband applications are disclosed. In one embodiment, a transmitter is configured to upconvert and amplify a digital transmit signal to provide an analog radio frequency transmit signal at an output of the transmitter that includes a desired signal in a transmit band of the transmitter and transmitter noise in a receive band of a main receiver. The main receiver is configured to amplify, downconvert, and digitize an analog radio frequency receive signal to provide a digital receive signal. The digital feedforward transmit noise cancellation subsystem is configured to process the digital transmit signal to generate a digital transmitter noise cancellation signal that is representative of the transmitter noise in the receive band and is subtracted from the digital receive signal to thereby provide a compensated digital receive signal.

Digital suppression of transmitter intermodulation in receiver

A method and apparatus for compensating for nonlinearities in a non-linear device for manipulating a signal is described. Shortly before an initial discrete power increase is applied to the device, a first pre-distortion function is generated on the basis of a first set of DPD parameters and applied to the signal before it reaches the device. A predetermined time period after the initial power increase, the first pre-distortion function stops being applied to the signal, and a second pre-distortion function is generated on the basis of a second set of DPD parameters and applied to the signal. Shortly before a subsequent discrete power increase is applied to the device, the first pre-distortion function is generated on the basis of the first set of DPD parameters and applied to the signal.

Digital predistortion of non-linear devices

A method for compensating signal distortions in multiple transmitting branches entering a composite amplifier.

Method for compensating signal distortions in composite amplifiers

A radio frequency transmitter comprises an amplifier, an antenna port, an isolator adapted to isolate an output of the amplifier from an interfering signal of the antenna port, a linearization loop and a transmission line comprising a first part (coupling a signal source to an input of the amplifier), a second part (coupling the output of the amplifier to an input of the isolator) and a third part (coupling an output of the isolator to the antenna port). The linearization loop is adapted to reduce non-linearity of the isolator and comprises a first directional coupler coupled to the third part of the transmission line, a loop impedance, and at least one further linearization loop element adapted to adjust a linearization signal and to feed the adjusted linearization signal to the transmission line. The radio frequency transmitter also comprises an interference reducing circuit adapted to reduce an influence of the interfering signal on the linearization loop. The circuit comprises a variable gain and phase shifter, and second and third directional couplers. The variable gain and phase shifter is coupled to the third part of the transmission line via the second directional coupler, which extracts a compensation signal from the transmission line, and is adapted to adjust amplitude and phase of the compensation signal based on the amplitude and phase of the interfering signal passing through the loop impedance. The third directional coupler couples the variable gain and phase shifter to the loop feed line and feeds the adjusted compensation signal thereto.

Circuit and method for interference reduction

A method for compensating signal distortions in multiple transmitting branches () entering a composite amplifier (). According to the invention the method comprises the steps of: &#x2014;providing (S) one or more input signals (x) to the composite amplifier. &#x2014;observing (S) an output signal (z) from the composite amplifier () for each provided input signal; &#x2014;deriving (S) an error in each output signal (z) by comparing the output signal with an ideal output signal, said error being caused by said signal distortions; &#x2014;deriving (S) the individual contribution from each transmitting branch () to the error by utilizing a composite amplifier model, said composite amplifier model comprising information about the contribution from each constituent amplifier () to the output signal for each provided input signal: &#x2014;compensating the signal distortions in the transmitting branches () accordingly.

An IQ-modulator pre-distorter includes an iteratively updated digital filter (gQ, gQ) for filtering one of the branches of an IQ-signal to compensate for IQ-modulator generated amplitude errors. An iteratively updated digital filter (cQI, cQI), cross-connected from one of the branches to the other branch, filters one of the components of an IQ-signal to compensate for IQ-modulator generated inter-modulation between the branches. Iteratively updated compensators (dcI, dcQ) counteract IQ-modulator generated offset errors.

IQ-modulator pre-distortion

A power amplifier pre-distorter is formed by a FIR filter structure which includes an individual look-up table for each filter tap, where each look-up table represents a sample polynomial in a variable representing signal amplitude, and means for selecting, from each filter tap look-up table, a filter coefficient that depends on the amplitude of corresponding complex signal value to be multiplied by the filter tap. A training method for such a pre-distorter sets (S) the entries of table Tand Tto predetermined values. Then it measures and stores (S) a batch of input signals x and feedback signals y. New estimates of Tand Tare determined (S) using an iteration of a least mean square based iterative procedure. Then it is tested (S) whether the tables have converged. If the tables have converged, the current estimates are provided as the final tables. Otherwise another iteration (S-S) of the least mean square procedure is performed.

Power amplifier pre-distorter training

To generate a high-power modulated radio frequency signal Sfrom an input low or medium frequency information signal S, the information signal is pulse-shaped in a quantifier to form a digital signal Shaving discrete signal values. The digital signal is processed in a switching unit comprising switches for each signal value, in radio frequency wave generators for each switch generating carrier waves of radio frequency, and in control circuits for each switch to control the opening and closing thereof. When a switch is closed, its associated generator is connected to the output line of the switching unit, and when it is opened, the generator is disconnected therefrom. In the switching unit, a switched radio frequency signal Scarrying the information of the input signal is formed by opening and closing the switches when the digital signal adopts or does not adopt, respectively, the signal value associated with the respective switch. The switching is thus controlled by the signal values of the digital signal. The switched signal on the output line of the switching unit is filtered by a filter for achieving the high-power, modulated, radio frequency signal S.

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