The guard-space reference disclosed herein is a signal transmitted in the guard spaces separating message data intervals, and configured to reveal amplitude noise or phase noise or both, using 5G or 6G technology. For example, the transmitter can transmit an I-branch with a predetermined amplitude level, and an orthogonal Q branch with zero amplitude, in the guard space. The receiver can measure the received amplitude and phase of the guard-space reference, subtract the initial amplitude and phase, and thereby measure both phase noise and amplitude noise. The receiver can then subtract the measured amplitude and phase effects from the message data, thereby negating both phase noise and amplitude noise. Guard-space references disclosed herein can preserve the inter-subcarrier orthogonality, inter-symbol separation, and signal circularity advantages of prior art, while additionally providing both amplitude noise and phase noise mitigation. Examples are suitable for wireless standards.

The disclosure relates to an IQ mismatch correction module for a radio receiver, the IQ mismatch correction module comprising: an input terminal configured to receive an input signal; an output terminal configured to provide a filtered output signal; a mismatch detection module comprising: one or more bandpass filters configured to receive, from the input terminal or output terminal, a bandpass input signal and to pass a plurality of sub-bands of the bandpass input signal to provide respective bandpass filtered signals; one or more amplitude and phase mismatch detectors configured to determine amplitude and phase mismatch coefficients based on the bandpass filtered signals from the plurality of sub-bands; a transformation unit configured to apply a transformation to the amplitude and phase mismatch coefficients to provide correction filter coefficients for the plurality of sub-bands; and a filter module configured to: receive the filter coefficients for the plurality of sub-bands from the mismatch detection module; and filter the input signal in accordance with the received filter coefficients to provide the filtered output signal.

Multiphase signal generation circuitry receives input signals that are out-of-phase with one another by a quadrature delay (e.g., 90°), and generates output signals that are out-of-phase with one another by half of the quadrature delay. A first input signal may be provided to a first delay circuitry, which is then input to a first phase interpolator. The first delay circuitry is also input to second delay circuitry, which also generates an output that is input to the first phase interpolator. The first phase interpolator outputs a first output signal. The second delay circuitry is input to third delay circuitry, which in turn is input to a second phase interpolator with a second input signal that is out-of-phase with the first input signal by the quadrature delay. The second phase interpolator outputs a second output signal that is out-of-phase with the first output signal by the half of the quadrature delay.

A method of compensating for IQ mismatch (IQMM) in a transceiver may include sending first and second signals from a transmit path through a loopback path, using a phase shifter to introduce a phase shift in at least one of the first and second signals, to obtain first and second signals received by a receive path, using the first and second signals received by the receive path to obtain joint estimates of transmit and receive IQMM, at least in part, by estimating the phase shift, and compensating for IQMM using the estimates of IQMM. Using the first and second signals received by the receive path to obtain estimates of the IQMM may include processing the first and second signals received by the receive path as a function of one or more frequency-dependent IQMM parameters.

A method and an apparatus for satellite laser broadband demodulation are provided. The method includes: setting a residual carrier to a carrier acquisition range of a receiver, pulling the residual carrier to an MHz level by adjusting a frequency of a local oscillator laser, and obtaining a precise carrier frequency according to an accurate frequency acquisition, such that the residual carrier enters a fast acquisition band of a carrier tracking phase-locked loop. After carrier acquisition is achieved, carrier tracking and data recovery processing are performed. According to the present disclosure, signal equalization of an ultra-high bandwidth/ultra-high bit rate can be implemented, and carrier acquisition, tracking, and demodulation are quickly achieved for a modulation signal in a high dynamic range.

The disclosure relates to technology for compensating for I/Q imbalance. An apparatus includes I-path circuitry having a first analog filter configured to filter an I-path signal and Q-path circuitry having a second analog filter configured to filter a Q-path signal. An I/Q imbalance compensation circuit of the apparatus is configured to process digital versions of the I-path signal and the Q-path signal to compensate for mismatch between the I-path circuitry and the Q-path circuitry. A first circuit of the apparatus is configured to apply a coarse adjustment to at least one of the first analog filter or the second analog filter to reduce an initial mismatch between the I-path circuitry and the Q-path circuitry. The first circuit is configured to operate the I/Q imbalance compensation circuit to compensate for a residual mismatch between the I-path circuitry and the Q-path circuitry with the coarse adjustment applied.

Techniques are presented to improve the accuracy of and reduce the time required for calibration of an in-phase/quadrature (I/Q) transmission circuit. A measurement receiver measures the I/Q mismatch, where an RF phase shift is introduced to distinguish between the transmitter and measurement receiver I/Q mismatches. Rather than assuming an amount of introduced phase shift, a measurement is used to estimate the phase shift. This phase estimate is then used to determine and correct the I/Q mismatch in the transmitter and measurement receiver. An iterative process can be used to improve the I/Q correction factors. Using simple signal processing to measure the phase shift during calibration and to perform the image calibration calculations, the phase shifter requirements can be significantly relaxed, resulting in faster design time and reduced design area/cost. This approach results in reduced calibration time, thus contributing to reduced factory production time and enabling faster live mode image calibration.

In one embodiment, an apparatus includes a baseband circuit to generate a plurality of subcarriers of a complex sample of a message to be transmitted, and a compensation circuit coupled to the baseband circuit, the compensation circuit to compensate for IQ mismatch. The compensation circuit may include: a calibration circuit to determine, using a tone signal, gain correction values and phase correction values for a subset of the plurality of subcarriers; and a correction circuit to apply the gain correction values and the phase correction values to the plurality of subcarriers to compensate for the IQ mismatch.

An in-phase and quadrature mismatch compensator for a quadrature transmitter includes a delay element, a complex-valued filter and an adder. The delay element receives an input transmit signal and outputs a delayed transmit signal. The complex-valued filter receives the input transmit signal and outputs a selected part of a filtered output transmit signal. The adder adds the delayed transmit signal and the selected part of the filtered output transmit signal and outputs a pre-compensated transmit signal. In one embodiment, the selected part of the filtered output transmit signal includes the real part of the complex-valued output transmit signal. In another embodiment, the selected part of the filtered output transmit signal includes the imaginary part of the complex-valued output transmit signal. Two transmit real-valued compensators are also disclosed that combine the in-phase and quadrature signals before being filtered.

Multiphase signal generation circuitry receives input signals that are out-of-phase with one another by a quadrature delay (e.g., 90°), and generates output signals that are out-of-phase with one another by half of the quadrature delay. A first input signal may be provided to a first delay circuitry, which is then input to a first phase interpolator. The first delay circuitry is also input to second delay circuitry, which also generates an output that is input to the first phase interpolator. The first phase interpolator outputs a first output signal. The second delay circuitry is input to third delay circuitry, which in turn is input to a second phase interpolator with a second input signal that is out-of-phase with the first input signal by the quadrature delay. The second phase interpolator outputs a second output signal that is out-of-phase with the first output signal by the half of the quadrature delay.