242 results about "Phase imbalance" patented technology

A method for correcting gain imbalance error, phase imbalance error and DC offset errors in a transmitter having an OFDM-based I / Q modulator is disclosed. The method employs a compensator prior to the I / Q-modulator to compensate for the gain and phase imbalance and DC offset. The compensator is efficiently updated with the estimated values of gain and phase imbalance and DC offsets obtained by performing the DFT operation in the digital baseband domain while sending a pair of orthogonal test tones to the modulator's inputs from a digital baseband chip, then down converting the RF modulated signal through a nonlinear device and a bandpass filter to a baseband signal, and finally sampling it using an A / D. The delay mismatch, which is mainly generated by lowpass filters between the I and Q branches, is also minimized in this method.

A radio frequency transceiver for off-line transmit and receive calibrations includes: a transmit pre-distortion module configured to receive a transmit calibration signal during a transmit calibration mode, a transmit communication signal during a transmit communication operation mode, and one or more transmit calibration adjustment signals; a transmit channel frequency converter; and a transmit calibration module configured to provide the one or more transmit calibration adjustment signals and the transmit calibration signal to the transmit pre-distortion module. It may also include a receive channel frequency converter; a receive pre-distortion module configured to receive a receive calibration signal during the receive calibration mode, a receive communication signal during a receive communication operation mode, and one or more receive calibration adjustment signals; and a receive calibration module configured to provide the one or more receive calibration adjustment signals to the receive pre-distortion module and a receive calibration signal to the transmit pre-distortion module.

Methods and systems to calibrating a transmitter for I / Q imbalance and local oscillator feed-through include generating a test tone, frequency up-converting the test tone, monitoring one or more features of the up-converted test tone, and adjusting one or more features of the transmitter in response to the monitoring. The monitoring optionally includes monitoring a beating of the envelope of the up-converted test tone. In an embodiment, a first harmonic of the up-converted test tone is monitored for local oscillator feed-through (LOFT). Alternatively, baseband data inputs to the transmitter are disabled, and LOFT is measured by measuring power at the transmitter output. A second harmonic of the up-converted test tone is monitored for gain and phase imbalances. The adjusting optionally includes adjusting a gain imbalance, adjusting a phase imbalance, and / or adjusting DC offsets. The adjusting optionally includes an iterative refinement process. Such a refinement process optionally includes performing a first monitoring, applying a set of relatively coarse settings to the one or more features in the transmitter, monitoring the beating resulting from each of the coarse settings, selecting the coarse setting corresponding the smallest beating, applying a set of relatively fine settings centered around the selected coarse setting, wherein the fine settings are more closely related to one another than are the coarse settings, monitoring the beating resulting from each of the fine settings, and selecting the fine setting corresponding the smallest beating.

A transceiver front end includes a transmit / receive (T / R) switch, a first balun, a second balun, a low noise amplifier, a power amplifier, and compensation circuitry. The T / R switch is operably coupled to an antenna for receiving inbound radio frequency (RF) signals and for transmitting outbound RF signals. The first balun includes a single ended winding and a differential winding, where the single ended winding is operably coupled to the T / R switch. The second balun includes a single ended winding and a differential winding, where the single ended winding is operably coupled to the T / R switch. The low noise amplifier is operably coupled the differential winding of the first balun. The power amplifier is operably coupled to the differential winding of the second balun. The compensation circuitry is operably coupled to the first balun to compensate for at least one of phase imbalance, amplitude imbalance, and impedance imbalance of the first balun.