Methods and devices used in mobile receiver front end to support multiple paths and multiple frequency bands are described. The presented devices and methods provide benefits of scalability, frequency band agility, as well as size reduction by using one low noise amplifier per simultaneous outputs. Based on the disclosed teachings, variable gain amplification of multiband signals is also presented.

A low noise amplifier includes at least two variable gain amplifier stages, each variable gain amplifier configured to accept an input signal and to provide a load driving signal; a tunable bandpass filter connected as a load to each variable gain amplifier stage, wherein each bandpass filter includes a resonant tank, each resonant tank including an inductor, wherein each inductor of each resonant tank is oriented in orthogonal relation with respect to each respective longitudinal axis of each next inductor, the orthogonal relation of the respective longitudinal axes configured to reduce mutual coupling between the tunable bandpass filters; a cross-coupled transistor pair, and at least one cross-coupled compensation transistor pair biased in a subthreshold region configured to add a transconductance component as a function of a load driving signal; and, a controller circuit configured to tune each tunable bandpass filter.

A low noise amplifier includes at least two variable gain amplifier stages, each variable gain amplifier configured to accept an input signal and to provide a load driving signal; a tunable bandpass filter connected as a load to each variable gain amplifier stage, wherein each bandpass filter includes a resonant tank, each resonant tank including an inductor, wherein each inductor of each resonant tank is oriented in orthogonal relation with respect to each respective longitudinal axis of each next inductor, the orthogonal relation of the respective longitudinal axes configured to reduce mutual coupling between the tunable bandpass filters; a cross-coupled transistor pair, and at least one cross-coupled compensation transistor pair biased in a subthreshold region configured to add a transconductance component as a function of a load driving signal; and, a controller circuit configured to tune each tunable bandpass filter.

Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed for particular gain modes to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores when switching gain modes to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a high gain amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity (e.g., for lower gain modes). The disclosed signal amplifiers have a first active core with amplification chains for each of a plurality of inputs and a second active core with a single amplification chain to amplify signals received at the plurality of inputs.

Disclosed herein are signal amplifiers having a plurality of amplifier cores. Individual amplifier cores can be designed for particular gain modes to enhance particular advantages while reducing other disadvantages. The signal amplifier can then switch between amplifier cores when switching gain modes to achieve desired performance characteristics (e.g., improving noise figure or linearity). Examples of signal amplifiers disclosed herein include amplifier architectures with a high gain amplifier core that reduces the noise figure and a linearity boost amplifier core that increases linearity (e.g., for lower gain modes). The disclosed signal amplifiers have a first active core with amplification chains for each of a plurality of inputs and a second active core with a single amplification chain to amplify signals received at the plurality of inputs.

A communication system includes a demodulator configured to demodulate an amplified modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit. The filter is configured to generate a filtered first signal based on a first signal. The first signal is based on the first carrier signal and the amplified modulated signal. The filter has a gain adjusted based on a set of control signals. The gain adjusting circuit is coupled to the filter, and configured to generate the set of control signals based on at least a voltage of the filtered first signal or a voltage of a second signal. The gain adjusting circuit includes a first peak detector configured to output a peak value of the voltage of the second signal. The voltage of the second signal includes a voltage of the first signal or a voltage of a reference signal.

A communication system includes a demodulator configured to demodulate an amplified modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit. The filter is configured to generate a filtered first signal based on a first signal. The first signal is based on the first carrier signal and the amplified modulated signal. The filter has a gain adjusted based on a set of control signals. The gain adjusting circuit is coupled to the filter, and configured to generate the set of control signals based on at least a voltage of the filtered first signal or a voltage of a second signal. The gain adjusting circuit includes a first peak detector configured to output a peak value of the voltage of the second signal. The voltage of the second signal includes a voltage of the first signal or a voltage of a reference signal.

Various embodiments of the invention relate to a tunable gain equalizer to enable a RF output with constant gain over a wide frequency band. The tunable gain equalizer comprises a series path formed by a plurality of adjustable capacitors coupled in series, and two shunt paths coupled to the series path. The adjustable capacitors may be varactors coupled to a biasing voltage for capacitance adjustment. The shunt paths comprise inductors to enable a positive gain slope to compensate negative gain slope of RF amplifiers. The shunt paths may be bridged by one or more branches connected between the two shunt paths. The bridged branches provide a higher tunable gain slope amount and a better input/output matching. By making the biasing voltage of the tunable gain equalizer temperature dependent, the tunable gain equalizer is able to generate a temperature dependent gain slope to offset the temperature variation influence.

An amplification circuit configured to generate an output signal by differentially amplifying first and second input signals. The first and second input signals are a differential signal pair. Alternatively, the first input signal is a single-ended signal, and the second input signal is a reference signal. The amplification circuit is configured to perform a differential amplification operation by increasing a gain for generating an output signal based on the first input signal.

The disclosed technology is related to a radio-frequency (RF) amplifier having a bypass circuit and a resonant structure to improve performance in a bypass mode (e.g., a low gain mode). The disclosed amplifiers have a resonant structure that effectively isolates an amplifier core from a bypass circuit. For example, in a bypass mode, the resonant structure is configured to create an open impedance looking into the amplifier core input. This effectively removes any loading from the amplifier core to the bypass circuit. The disclosed amplifiers with resonant structures improve linearity performance in bypass modes due at least in part to the open impedance to the amplifier core provided by the resonant structure.