Contents
What is IQ phase imbalance?
imbalance is a performance-limiting issue in the design of direct conversion receivers, also known as zero intermediate frequency (IF) or homodyne receivers. Such a design translates the received radio frequency (RF, or pass-band) signal directly from the carrier frequency ( ) to baseband using only one mixing stage.
What is quadrature error correction?
The non-ideal filter response comes from filtering in components in the signal path of theTRx. In order to fulfil the requirements on the in-band filter response equalization can be used and the most common method to lower the QEs is to use time-domain Quadrature Error Correction (QEC).
What is amplitude imbalance?
As discussed earlier, the signal is split into an in-phase component and a quadrature component. The “splitting” is achieved by phase shifting the LO output or RF signal by 90° in the quadrature arm. Variations in amplitudes between the IQ signal result in amplitude imbalance, further corrupting the incoming signal.
What is IQ skew?
When a signal contains Quadrature skew, the error could be reported as IQ Gain Imbalance if the signal generator has a mapping that is different from the VSA receiver. IQ Gain Imbalance is characterized by a gain difference between I and Q channels.
What is quadrature error?
With a Quadrature Error, the rectangular off-axis stretch is rotated onto the ideal I/Q axes yielding IQ Gain Imbalance. Likewise, the same 45° rotation converts an on-axis rectangular stretch into an off-axis stretch interpreted as Quadrature Error.
What causes a phase imbalance?
A phase unbalance may be caused by unstable utility supply, unbalanced transformer bank, unevenly distributed single-phase loads on the same power system, or unidentified single-phase to ground faults.
What are i Q signals?
I/Q signaling refers to the use of two sinusoids that have the same frequency and a relative phase shift of 90°. Amplitude, phase, and frequency modulation can be performed by summing amplitude-modulated I/Q signals. Quadrature modulation refers to modulation that involves I/Q signals.
What is IQ calibration?
In order to calibrate the IQ mismatch, a calibration loop is built in the RF chip, which is composed of a square power detector and a band-pass filter. There are two operation modes controlled by the digital baseband for the calibration loop: the calibration mode and the shutdown mode.
How is base band signal affected by IQ imbalance?
In an OFDM system, the base-band signal consists of several sub-carriers. Complex-conjugating the base-band signal of the kth sub-carrier carrying data is the sub-carrier spacing. Equivalently, the received base-band OFDM signal under the imbalance also introduces Inter Carrier Interference (ICI) from the adjacent carrier or sub-carrier.
How does an IQ imbalance occur in the oscillator?
IQ imbalances occur due to mismatches between the parallel sections of the receiver chain dealing with the in-phase (I) and quadrature (Q) signal paths. The local oscillator (LO) generates a sinewave, and a copy of that sinewave that is delayed by 90 degrees.
Which is better time domain or frequency domain for IQ imbalance?
IQ imbalance compensation. The frequency domain compensated signal at the ith symbol and the kth subcarrier Nevertheless, in reality, the time-domain compensation is less preferred because it introduces larger latency between IQ imbalance estimation and compensation.