System and method for calibration using local oscillator (lo) phase shift
AssigneeQUALCOMM Incorporated
InventorsOjas CHOKSI, Ghaith SHABSIGH
Life of this patent
Estimating the term…
Abstract
A residual sideband (RSB) calibration system includes a phase locked loop (PLL) circuit shared between a transmit (Tx) circuit and a receive (Rx) circuit, the PLL circuit configured to provide a local oscillator (LO) signal to transmit mixers in the Tx circuit and to receive mixers in the Rx circuit, a phase shifter connected between an output of the PLL circuit and the receive mixers, and a loopback circuit connecting the Tx circuit and the Rx circuit.
Claims20
A residual sideband (RSB) calibration system, comprising:
- a phase locked loop (PLL) circuit shared between a transmit (Tx) circuit and a receive (Rx) circuit, the PLL circuit configured to provide a local oscillator (LO) signal to transmit mixers in the Tx circuit and to receive mixers in the Rx circuit;
- a phase shifter connected between an output of the PLL circuit and the receive mixers;
- and
- a loopback circuit connecting the Tx circuit and the Rx circuit.
A method for joint transmit and receive residual sideband (RSB) calibration, comprising:
- injecting a transmit (Tx) signal at a first phase of a local oscillator (LO) into a receive (Rx) circuit via a loopback circuit;
- measuring a main signal tone and an image signal tone at the first LO phase;
- shifting the first LO phase signal by 90 degrees to a second LO phase;
- injecting the Tx signal into the Rx circuit via the loopback circuit;
- measuring a main signal tone and an image signal tone at the second LO phase;
- determining a ratio of the image signal tone to the main signal tone at the first LO phase and the second LO phase to obtain a Tx RSB and a Rx RSB;
- adjusting a filter to compensate for the Tx RSB;
- and
- compensating for the Rx RSB by pre-distorting an Rx signal.
A method for joint transmit and receive residual sideband (RSB) calibration, comprising:
- generating a local oscillator (LO) signal in a phase locked loop (PLL) circuit, the PLL circuit shared between a transmit (Tx) circuit and a receive (Rx) circuit, the PLL circuit configured to provide the local oscillator (LO) signal to transmit mixers in the Tx circuit and to receive mixers in the Rx circuit;
- connecting a loopback circuit between the Tx circuit and the Rx circuit, the loopback circuit for injecting a transmit (Tx) signal at a first phase into a receive (Rx) circuit and for injecting the transmit (Tx) signal at a second phase into a receive (Rx) circuit;
- and
- generating the second phase by shifting the LO signal with a phase shifter between an output of the PLL circuit and the receive mixers.
Dependencies are inferred from the claim text.