Reference signal distribution in multi-module systems
Methods and systems for reducing and eliminating the effects of reference signal leakage in multi-module radio-frequency systems, particularly for radio-frequency integrated-circuit devices. Isolation is provided by frequency shifting, by binary phase-shift keying of reference signals to furnish different reference signals with unique signatures to enable separation and discrimination, and by backwards sending of reference signals from receiver to transmitter to avoid contamination of receiver signals by leakage of transmitter reference signals. In addition to improving calibration, methods of the present invention also provide noise reduction in certain multiple-module radio frequency systems.
1. A radio-frequency transmitter-receiver system comprising:
a transmitter for transmitting a transmitted signal at a transmission frequency;
a receiver for receiving the transmitted signal as a received transmitted signal, wherein:
the receiver includes a local oscillator having a local oscillator signal at a local oscillator frequency, for downconverting the received transmitted signal from the transmission frequency to an intermediate frequency as a receiver intermediate frequency signal;
a transmitter downconverter associated with the transmitter, for downconverting a reference signal from the receiver's local oscillator frequency to the intermediate frequency as a transmitter intermediate frequency signal, according to a signal from the transmitter;
a reference signal path from the local oscillator of the receiver to the transmitter downconverter, for conveying the local oscillator signal from the local oscillator of the receiver to the transmitter downconverter; and a phase comparator, for measuring a phase difference between the receiver intermediate frequency signal and the transmitter intermediate frequency signal;
wherein the signal from the transmitter for downconverting the reference signal is a modulation of the local oscillator signal, and the transmitted signal is also a modulation of the local oscillator signal.
2. The radio-frequency transmitter-receiver system of claim 1 , wherein the signal from the transmitter for downconverting the reference signal is the transmitted signal.
3. The radio-frequency transmitter-receiver system of claim 1 , wherein the signal from the transmitter for downconverting the reference signal is a modulation of the transmitted signal.
4. A method for calibrating a radio-frequency transmitter-receiver system having:
a transmitter with a downconverter, wherein the transmitter outputs a transmitted signal, and
a receiver with a local oscillator signal, wherein the receiver mixes a received signal with the local oscillator signal to produce a receiver intermediate frequency signal,
the method comprising:
conveying the local oscillator signal from the receiver to the downconverter of the transmitter via a reference signal path;
downconverting by mixing the local oscillator signal from the receiver with the transmitted signal via the downconverter of the transmitter, to a transmitter intermediate frequency signal at the transmitter;
wherein the downconverting is according to a modulation of the local oscillator signal, and the transmitted signal is also a modulation of the local oscillator signal;
measuring a phase difference between the receiver intermediate frequency signal and the transmitter intermediate frequency signal; and
calibrating the transmitter-receiver system according to the phase difference.