Certain aspects provide a circuit for frequency conversion. The circuit includes first mixer circuitry coupled to a load circuit and having a first mixer configured to generate a first portion of a frequency-converted differential signal to be provided to the load circuit based on first differential input signals and second differential input signals, and a second mixer configured to generate a second portion of the frequency-converted differential signal based on third differential input signals and fourth differential input signals. The circuit also includes second mixer circuitry coupled to another load circuit and having a third mixer configured to generate a first portion of another frequency-converted differential signal based on the first differential input signals and the fourth differential input signals, and a fourth mixer configured to generate a second portion of the other frequency-converted differential signal based on the third differential input signals and the second differential input signals.

Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.

Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.

An aspect includes a filtering method including operating a first filter to filter a first input signal to generate a first output signal; operating a second filter to filter a second input signal to generate a second output signal; and merging at least a portion of the second filter with the first filter to filter a third input signal to generate a third output signal. Another aspect includes a filtering method including operating switching devices to configure a filter with a first set of pole(s); filtering a first input signal to generate a first output signal with the filter configured with the first set of pole(s); operating the switching devices to configure the filter with a second set of poles; and filtering a second input signal to generate a second output signal with the filter configured with the second set of poles.

A receive device includes: a quadrature detector; and a first signal detector that detects whether a signal subjected to detection in the quadrature detector is a received signal. The first signal detector assigns the signal subjected to quadrature detection in the quadrature detector to an orthogonal plane divided into a plurality of quadrants and derives an amount of movement of the signal assigned between quadrants, integrates absolute values of derived amounts of movement over a predetermined period of time, and determines whether the signal subjected to quadrature detection is a received signal by comparing an integrated value derived from integration with a threshold value.

Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.

Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.

A communication system is provided. The communication system includes a at least one baseband controller configured to process signals in a baseband frequency band. The communication system also includes at least one radio unit that is physically remote from the at least one baseband controller. Each radio unit includes a plurality of virtual radio units (VRUs) in a physical housing of the respective radio unit. Each radio unit also includes a fronthaul interface configured to communicate with the at least one baseband controller using a packet-based protocol on behalf of each VRU. Each radio unit also includes at least one radio frequency front end unit configured to transmit from and receive on behalf of each of the VRUs.

A quadrature detector subjects a received signal to quadrature detection and outputs a base band signal. A direct current component measurement circuit measures a magnitude of a direct current component included in the base band signal from the quadrature detector. A first HPF and a second HPF reduce the direct current component included in the base band signal from the quadrature detector. A demodulator demodulates the base band signal output from the first HPF and the second HPF. A controller exercises control to attenuate a level of the received signal input to the quadrature detector when the magnitude of the direct current component measured by the direct current component measurement circuit is equal to or larger than a threshold value.

Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.