Disclosed are systems, methods, and structures for DSP-free coherent receiver architectures applicable for short-reach optical links. Operationally, a received optical signal is down-converted by mixing it with a local oscillator (LO) laser signal using a 90-degree hybrid followed by balanced photodiodes. Other receiver functions are performed using analog signal processing thereby avoiding power-hungry, high-speed analog-to-digital converters and high-speed digital signal processing. Carrier phase recovery is performed by an electrical phase-locked loop employing a multiplier-free phase estimator stage thatwhile designed for quaternary phase-shift keying signalsmay be employed in designs exhibiting higher modulation formats. Since carrier phase recovery is performed in the electrical domain, LO laser frequency modulation or LO laser integration is not employed. Polarization demultiplexingif employedmay be performed by the addition of an optical polarization controller prior to the hybrid and may advantageously be realized by cascading multiple phase shifters driven by low-speed circuitry.

A receiver circuit includes a quadrature signal generator to generate an in-phase (I) signal and a quadrature (Q) signal from a local oscillator signal and an IQ phase sense and control circuit to generate a phase adjustment code responsive to a phase error between quadrature signals generated by a plurality of mixers. The receiver circuit also includes a phase corrector to adjust a phase difference between the I and Q signals from the quadrature signal generator to generate corrected I and Q signals to be provided to the plurality of mixers.

A mixer is connected to a signal generator and an antenna and outputs a signal at an intermediate frequency. A PLL demodulator subjects the signal at the intermediate frequency from the mixer to PLL demodulation. An amplifier amplifies a signal from the PLL demodulator. A detector detects an amount of shift occurring in the PLL demodulator. A detector detects a gain of the amplifier. An FSK demodulator subjects a signal from the amplifier to FSK demodulation. An AFC unit detects a frequency offset in the signal from the amplifier and causes the signal generator to make a correction for the frequency offset detected.

A mixer is connected to a signal generator and an antenna and outputs a signal at an intermediate frequency. A PLL demodulator subjects the signal at the intermediate frequency from the mixer to PLL demodulation. An amplifier amplifies a signal from the PLL demodulator. A detector detects an amount of shift occurring in the PLL demodulator. A detector detects a gain of the amplifier. An FSK demodulator subjects a signal from the amplifier to FSK demodulation. An AFC unit detects a frequency offset in the signal from the amplifier and causes the signal generator to make a correction for the frequency offset detected.

Systems and methods for beamforming using a cross-mixing architecture are provided. A beamformer can use an element-to-element mixing concept and can avoid the use of conventional bulky analog phase shifters. Incident signals can be sent through a phase-locked loop and then mixed with a signal from an antenna element oppositely spaced about a phase center of the antenna element array. Beamformers can be integrated into existing hybrid structures by substituting the traditional analog part of the beamforming process.

Systems and methods for beamforming using a cross-mixing architecture are provided. A beamformer can use an element-to-element mixing concept and can avoid the use of conventional bulky analog phase shifters. Incident signals can be sent through a phase-locked loop and then mixed with a signal from an antenna element oppositely spaced about a phase center of the antenna element array. Beamformers can be integrated into existing hybrid structures by substituting the traditional analog part of the beamforming process.

A method for avoiding inter-modulation distortion in a communications apparatus capable of supporting carrier aggregation and communicating with a peer communications apparatus in a wireless network via at least a first CC and a second CC includes: determining a frequency adjustment value for adjusting a first oscillating frequency of a first local oscillation signal utilized for processing an RF signal of the first CC or a second oscillating frequency of a second LO signal utilized for processing an RF signal of the second CC when an RF signal or a baseband signal of the second CC is interfered with by an inter-modulation distortion signal contributed by any signal component related to the first CC; and adjusting the first oscillating frequency or the second oscillating frequency according to the frequency adjustment value.

A method for avoiding inter-modulation distortion in a communications apparatus capable of supporting carrier aggregation and communicating with a peer communications apparatus in a wireless network via at least a first CC and a second CC includes: determining a frequency adjustment value for adjusting a first oscillating frequency of a first local oscillation signal utilized for processing an RF signal of the first CC or a second oscillating frequency of a second LO signal utilized for processing an RF signal of the second CC when an RF signal or a baseband signal of the second CC is interfered with by an inter-modulation distortion signal contributed by any signal component related to the first CC; and adjusting the first oscillating frequency or the second oscillating frequency according to the frequency adjustment value.

Various embodiments relate to a PLL based FSK demodulator, the FSK demodulator comprising a PFD configured to receive an input signal, a fully differential auxiliary charge pump configured to receive and amplify the input signal from the PFD, a capacitor configured to filter the input signal from the auxiliary charge pump and a fully differential slicer configured to demodulate the input signal and output recovered data.

Various embodiments relate to a PLL based FSK demodulator, the FSK demodulator comprising a PFD configured to receive an input signal, a fully differential auxiliary charge pump configured to receive and amplify the input signal from the PFD, a capacitor configured to filter the input signal from the auxiliary charge pump and a fully differential slicer configured to demodulate the input signal and output recovered data.