Carrier frequency recovery in a receiver

A receiver, comprising:

• a first low pass filter having a first low pass filter input and a first low pass filter output;
• a second low pass filter having a second low pass filter input and a second low pass filter output;
• frequency reference circuitry having a frequency reference output and configured to generate a reference signal having a reference frequency at the frequency reference output;
• a phase locked loop (PLL) including a voltage controlled oscillator (VCO), the VCO having a VCO input and a VCO output, the VCO input coupled to the frequency reference output;
• an I-Q mixer having a first I-Q mixer input, a second I-Q mixer input, a first I-Q mixer output and a second I-Q mixer output, the first I-Q mixer output coupled to the first low pass filter input, the second I-Q mixer output coupled to the second low pass filter input, the second I-Q mixer input coupled to the VCO output, and the I-Q mixer configured to:
• multiply the first I-Q mixer input by the second I-Q mixer input to generate an I component at the first I-Q mixer output;
• and multiply the first I-Q mixer input by the second I-Q mixer input phase shifted by 90° to generate a Q component at the second I-Q mixer output;
• and
• a carrier recovery (CR) block having a CR output and first and second CR inputs, the first CR input coupled to the first low pass filter output, the second CR input coupled to the second low pass filter output, and the CR block configured to generate a control voltage at the CR output to tune at least one of the VCO or the frequency reference circuitry responsive to the first and second CR inputs;
• in which:
• the VCO has a VCO control input coupled to the CR output, and the VCO is configured to change a frequency of the VCO output responsive to the control voltage, so the frequency of the VCO output is closer to a frequency of an unmodulated carrier signal component of a receiver input signal at the first I-Q mixer input;
• or
• the frequency reference circuitry has a frequency reference input coupled to the CR output, the frequency reference circuitry is configured to change the reference frequency responsive to the control voltage, and the VCO is configured to change the frequency of the VCO output responsive to the reference frequency, so the frequency of the VCO output is closer to the frequency of the unmodulated carrier signal component of the receiver input signal.

A method of transmitting a signal, comprising:

• generating a frequency reference signal having a reference frequency, and providing the frequency reference signal to a phase locked loop (PLL);
• generating a voltage controlled oscillator (VCO) output, using a VCO of the PLL, responsive to the frequency reference signal, so that the VCO output forms a carrier signal;
• receiving an I input signal, a Q input signal, and a direct current (DC) leaky carrier signal;
• adding the DC leaky carrier signal to either the I input signal or the Q input signal, wherein a first input signal includes the carrier signal plus the I input signal or the Q input signal that is added to the DC leaky carrier signal, and a second input signal includes the I input signal or the Q input signal that is not added to the DC leaky carrier signal;
• modulating the carrier signal with the first input signal and the second input signal using an I-Q mixer to generate a modulated signal;
• and
• transmitting the modulated signal.

A method, comprising:

• a) receiving an input signal;
• b) generating a frequency reference with a reference frequency using a frequency reference generator;
• c) generating a voltage controlled oscillator (VCO) output, using a VCO, responsive to the frequency reference;
• d) multiplying the input signal by an output of a voltage controlled oscillator (VCO) of a phase locked loop (PLL) using an I-Q mixer to generate a first mixer output, and multiplying the input signal phase shifted 90° by the VCO output to generate a second mixer output;
• e) low pass filtering the first mixer output and the second mixer output, and using the low pass filtered first mixer output and low pass filtered second mixer output as phase frequency detector inputs;
• f) generating a control voltage, using a phase frequency detector, responsive to the phase frequency detector inputs;
• g) repeating the steps b) through f) while controlling at least one of the VCO or the frequency reference generator using the control voltage, until the VCO output stabilizes;
• and
• h) after the VCO output stabilizes, high pass filtering the first mixer output to generate a first receiver output, and high pass filtering the second mixer output to generate a second receiver output.