Cartesian loop systems with digital processing
OwnerStephen Ian Mann, Mark Anthony Beachinventors
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Abstract
A Cartesian loop system for radio transmitters in which at least part of the baseband processing is carried out in the digital domain. Digital processing circuitry (250) combines a baseband input signal with a Cartesian feedback signal (206,207) to generate a forward signal. Analog circuitry (221, 201, 203, 204) converts the forward signal into a transmission output signal and generates the Cartesian feedback signal. Preferably the digital processing circuitry applies a phase shift process (208) to the Cartesian feedback signal before combination with the baseband input signal. The system is programmable allowing a single device to be used in a range of transmitters under different radio standards.
Claims17
A Cartesian loop system for radio transmission equipment comprising:
- digital processing circuitry that combines a baseband input signal with a Cartesian feedback signal to generate a forward signal, coupled to,
- analog circuitry that converts the forward signal into a transmission output signal and generates the Cartesian feedback signal.
A Cartesian loop circuit for transmitting baseband signals comprising:
- a forward path for converting an input digital baseband signal to an analog RF output signal,
- means for sampling the analog RF output signal to generate a feedback analog signal,
- a feedback path for converting the analog feedback signal to a digital baseband feedback signal, and
- digital processing circuitry that combines the input digital baseband signal with the digital feedback signal to create a combined signal for the forward path.
A method of linearising a radio transmitter comprising:
- (a) receiving a baseband input signal for transmission,
- (b) digitally combining the input signal with a Cartesian feedback signal to generate a modified signal,
- (c) upconverting and amplifying the modified signal to generate a radio frequency output signal, and
- (d) generating the Cartesian feedback signal from the radio frequency output signal.
Dependencies are inferred from the claim text.