An apparatus for generating a radio frequency signal based on a symbol within a constellation diagram is provided. The constellation diagram is spanned by a first axis representing an in-phase component and an orthogonal second axis representing a quadrature component. The apparatus includes a processing unit configured to select a segment of a plurality of segments of the constellation diagram containing the symbol. The segment is delimited by a third axis and a fourth axis each crossing the origin of the constellation diagram and spanning an opening angle of the segment of less than about 90. The processing unit is further configured to calculate a first coordinate of the symbol with respect to the third axis, and a second coordinate of the symbol with respect to the fourth axis. The apparatus further includes a plurality of digital-to-analog converter cells configured to generate the radio frequency signal using the first coordinate and the second coordinate.

Wide band quadrature signal generation includes a frequency synthesizer generating a LO or 2LO signal, a polyphase filter coupled to receive the LO signal and generate first in-phase and quadrature LO signals, a 2:1 frequency divider coupled to receive the 2LO signal and generate second in-phase and quadrature LO signals, and a LO signal selector for selecting either the first or second in-phase LO signals as an output in-phase LO signal and either the first or second quadrature LO signals as an output quadrature LO signal based on an output frequency. In some embodiments, when the output frequency is above a threshold, the first in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals and when the output frequency is at or below the threshold, the second in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals.

Wide band quadrature signal generation includes a frequency synthesizer generating a LO or 2LO signal, a polyphase filter coupled to receive the LO signal and generate first in-phase and quadrature LO signals, a 2:1 frequency divider coupled to receive the 2LO signal and generate second in-phase and quadrature LO signals, and a LO signal selector for selecting either the first or second in-phase LO signals as an output in-phase LO signal and either the first or second quadrature LO signals as an output quadrature LO signal based on an output frequency. In some embodiments, when the output frequency is above a threshold, the first in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals and when the output frequency is at or below the threshold, the second in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals.

A transmission system includes a first transponder including a first I/Q modulator, and a second transponder including a second I/Q modulator, and configured to communicate with the first transponder using a frequency modulation scheme, wherein the first transponder is configured to set a first phase rotation mode in a first state for first light signal output from the first I/Q modulator, and transmit, to the second transponder, a first command to specify a second phase rotation mode for second light signal output from the second I/Q modulator, and the second transponder is configured to set, in response to the first command, the second phase rotation mode in a state specified by the first command.

A transmission system includes a first transponder including a first I/Q modulator, and a second transponder including a second I/Q modulator, and configured to communicate with the first transponder using a frequency modulation scheme, wherein the first transponder is configured to set a first phase rotation mode in a first state for first light signal output from the first I/Q modulator, and transmit, to the second transponder, a first command to specify a second phase rotation mode for second light signal output from the second I/Q modulator, and the second transponder is configured to set, in response to the first command, the second phase rotation mode in a state specified by the first command.

Techniques related to signal processing include setting up a first operation mode or a second operation mode. In the first operation mode: providing a first analog signal to a first A/D converter by a first switch and a second analog signal to a second A/D by second switch, and converting the first analog signal to a first digital signal by the first A/D and the second analog signal to a second digital signal by the second A/D. In the second operation mode: demodulating a third analog signal to an in-phase signal and a quadrature signal by an I-Q-demodulator, providing the in-phase signal to the first A/D by the first switch, providing the quadrature signal to a second A/D by second switch, converting the in-phase signal to a third digital signal by the first A/D, and converting the quadrature signal to a fourth digital signal by the second A/D.

Wide band quadrature signal generation includes a frequency synthesizer generating a LO or 2LO signal, a polyphase filter coupled to receive the LO signal and generate first in-phase and quadrature LO signals, a 2:1 frequency divider coupled to receive the 2LO signal and generate second in-phase and quadrature LO signals, and a LO signal selector for selecting either the first or second in-phase LO signals as an output in-phase LO signal and either the first or second quadrature LO signals as an output quadrature LO signal based on an output frequency. In some embodiments, when the output frequency is above a threshold, the first in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals and when the output frequency is at or below the threshold, the second in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals.

Wide band quadrature signal generation includes a frequency synthesizer generating a LO or 2LO signal, a polyphase filter coupled to receive the LO signal and generate first in-phase and quadrature LO signals, a 2:1 frequency divider coupled to receive the 2LO signal and generate second in-phase and quadrature LO signals, and a LO signal selector for selecting either the first or second in-phase LO signals as an output in-phase LO signal and either the first or second quadrature LO signals as an output quadrature LO signal based on an output frequency. In some embodiments, when the output frequency is above a threshold, the first in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals and when the output frequency is at or below the threshold, the second in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals.

A calibration circuit and a calibration method for a phase shifter, a phase-shift circuit, a radio frequency transmitting circuit, a radio frequency receiving circuit, a radar sensor and an electronic device are provided. The calibration circuit for the phase shifter includes a phase acquisition circuit and a phase calibration circuit, the phase acquisition circuit coupled to the phase shifter is configured to modulate a radio frequency sample signal acquired from the phase shifter using a first baseband signal, down-convert the modulation signal to obtain a second baseband signal containing an actual phase; the phase calibration circuit coupled to the phase acquisition circuit is configured to acquire the actual phase in the second baseband signal, determine calibration phase information according to a phase deviation between the actual phase and a preset phase-shift phase, generate a phase-shift control signal according to calibration phase information and transmit it to the phase shifter.

Techniques related to signal processing include setting up a first operation mode or a second operation mode. In the first operation mode: providing a first analogue signal to a first A/D converter by a first switch and a second analogue signal to a second A/D by second switch, and converting the first analogue signal to a first digital signal by the first A/D and the second analogue signal to a second digital signal by the second A/D. In the second operation mode: demodulating a third analogue signal to an in-phase signal and a quadrature signal by an I-Q-demodulator, providing the in-phase signal to the first A/D by the first switch, providing the quadrature signal to a second A/D by second switch, converting the in-phase signal to a third digital signal by the first A/D, and converting the quadrature signal to a fourth digital signal by the second A/D.