A radio receiver comprises a local oscillator arrangement and a controller. The local oscillator arrangement is arranged to provide a signal for down-conversion of radio frequency signal to an intermediate frequency or a baseband frequency in the radio receiver, and the local oscillator arrangement is capable of selectably providing multiple frequency generation qualities. The controller is arranged to estimate a tolerable frequency generation quality for the current operation of the radio receiver or determine whether the current operation of the radio receiver is satisfactory in sense of a currently provided frequency generation quality, and based on the estimation or determination adjust frequency generation quality of the local oscillator arrangement by selecting one of the multiple frequency generation qualities. A radio arrangement, a method and a computer program are also disclosed.

A method for determining amplitude and phase correction coefficients for one or more signal processing paths across a frequency band of interest is provided. The method comprises transforming an input test signal from the time domain to the frequency domain to obtain an input magnitude spectrum and an input phase spectrum for the/each signal processing path. It further comprises transforming an/each respective output test signal from the time domain to the frequency domain to obtain an output magnitude spectrum and an output phase spectrum for the/each signal processing path. It also comprises comparing the/each input magnitude spectrum with its respective output magnitude spectrum to determine an amplitude correction coefficient for the/each signal processing path and/or comparing the/each input phase spectrum with its respective output phase spectrum, to determine a phase correction coefficient for the or each signal processing path.

Embodiments of the present disclosure provide a method, apparatus and computer program products for DC offset degradation. A method implemented in a massive multi-input multi-output (MIMO) system, which comprises a plurality of receiver branches, includes receiving a radio frequency (RF) signal in the plurality of receive branches. The method further includes configuring different local frequencies of a plurality of local oscillators respectively in the plurality of receiver branches according to a carrier frequency of the RF signal, to enable direct current (DC) offsets in the plurality of receiver branches to be distinguishable from each other in frequency.

Embodiments of the present disclosure provide a method, apparatus and computer program products for DC offset degradation. A method implemented in a massive multi-input multi-output (MIMO) system, which comprises a plurality of receiver branches, includes receiving a radio frequency (RF) signal in the plurality of receive branches. The method further includes configuring different local frequencies of a plurality of local oscillators respectively in the plurality of receiver branches according to a carrier frequency of the RF signal, to enable direct current (DC) offsets in the plurality of receiver branches to be distinguishable from each other in frequency.

There is provided a demodulator that makes it possible to reduce or avoid deterioration in demodulation performance due to nonlinearity of input amplitude-frequency characteristics of a variable capacitive element included in an analog control signal input section of a frequency variable oscillator, while suppressing an influence of noise. The demodulator includes: a low-resolution A/D converter that performs analog-digital conversion of a first phase difference signal, which represents a phase difference between a digitally modulated modulation signal and an oscillation signal, with a resolution lower than at least a resolution of a digital demodulation signal, which is a final output, to generate a second phase difference signal that is digital; a low-resolution D/A converter that performs digital-analog conversion of the second phase difference signal to generate a third phase difference signal that is analog; an analog subtractor that subtracts the third phase difference signal from the first phase difference signal to generate a first control signal; an ADPLL that generates a second control signal on the basis of a reference signal and the oscillation signal; and an FVO that generates the oscillation signal on the basis of the first control signal and the second control signal.

This envelope-detecting circuit comprises: a first multiplier able to multiply a first example of a signal received on an input port by itself, a modifier able to modify the amplitude of the power spectrum, of a second example of the signal received on the input port, at the frequency f.sub.c without modifying the amplitude of this power spectrum in a useful frequency band, a second multiplier able to multiply the modified signal by itself, a subtractor able to subtract from each other the signals delivered by the multipliers, a filter able to remove frequency components higher than or equal to 2f.sub.c in a signal obtained from the signal delivered by the subtractor, this filter being able to deliver the result of this filtering on an output connected to an output port of the envelope-detecting circuit.

This envelope-detecting circuit comprises: a first multiplier able to multiply a first example of a signal received on an input port by itself, a modifier able to modify the amplitude of the power spectrum, of a second example of the signal received on the input port, at the frequency f.sub.c without modifying the amplitude of this power spectrum in a useful frequency band, a second multiplier able to multiply the modified signal by itself, a subtractor able to subtract from each other the signals delivered by the multipliers, a filter able to remove frequency components higher than or equal to 2f.sub.c in a signal obtained from the signal delivered by the subtractor, this filter being able to deliver the result of this filtering on an output connected to an output port of the envelope-detecting circuit.

Disclosed herein are related to systems and methods for correcting non-linearity due to duty cycle error. In one aspect, a system includes a mixer configured to up-convert transmission (Tx) data, a coefficient calibrator configured to select a target value of a coefficient based on a measurement of an interference signal due to non-linearity of the mixer, and an interference canceller coupled to the coefficient calibrator and the mixer. In some embodiments, the interference canceller is configured to generate compensated Tx data based on the Tx data and the selected target value of the coefficient and provide the compensated Tx data to the mixer. In some embodiments, the compensated Tx data corrects for the non-linearity of the mixer.

A system for hybrid modulation and demodulation includes a transmitter and a receiver. The transmitter is configured to receive a hybrid signal of a space-ground link system (SGLS), including a first component and a second component; perform a double sideband (DSB) modulation on the first component using a carrier frequency to obtain a first waveform; perform a single sideband (SSB) modulation on the second component using the carrier frequency to obtain a second waveform; mix the first waveform and the second waveform to generate a hybrid waveform; and transmit the hybrid waveform. The receiver is configured to receive the hybrid waveform; determine the carrier frequency; separate the first waveform and the second waveform; perform a DSB demodulation on the first waveform to obtain a first demodulated signal; and perform an SSB demodulation on the second waveform to obtain a second demodulated signal.

A system for hybrid modulation and demodulation includes a transmitter and a receiver. The transmitter is configured to receive a hybrid signal of a space-ground link system (SGLS), including a first component and a second component; perform a double sideband (DSB) modulation on the first component using a carrier frequency to obtain a first waveform; perform a single sideband (SSB) modulation on the second component using the carrier frequency to obtain a second waveform; mix the first waveform and the second waveform to generate a hybrid waveform; and transmit the hybrid waveform. The receiver is configured to receive the hybrid waveform; determine the carrier frequency; separate the first waveform and the second waveform; perform a DSB demodulation on the first waveform to obtain a first demodulated signal; and perform an SSB demodulation on the second waveform to obtain a second demodulated signal.