A tunable filter is described where the frequency response as well as bandwidth and transmission loss characteristics can be dynamically altered, providing improved performance for transceiver front-end tuning applications. The rate of roll-off of the frequency response can be adjusted to improve performance when used in duplexer applications. The tunable filter topology is applicable for both transmit and receive circuits. A method is described where the filter characteristics are adjusted to account for and compensate for the frequency response of the antenna used in a communication system.

A digital amplifier that minimizes and restricts an analog signal system and uses a feedback signal and a dither signal is achieved. A pulse width modulator that adjusts a pulse width of a digital signal, a switching circuit that amplifies an output signal from the pulse width modulator, and a feedback signal generation unit that generates a feedback signal based on an output signal from the switching circuit are included, the pulse width modulator adjusts the pulse width of the digital signal with reference to the feedback signal, and the feedback signal generation unit includes a first amplifier that outputs a first amplified signal in which a difference between the output signal from the switching circuit and one of a reference voltage and a dither signal is amplified and a second amplifier that amplifies a difference between the first amplified signal and the other of the dither signal and the reference voltage and outputs the amplified difference as the feedback signal.

A filter includes multiple filter circuits. The filter circuits are coupled in series between an input terminal and an output terminal, to generate an output signal according to an input signal. One of the filter circuits operates as an active filter circuit or a passive filter circuit according to amplitude of the input signal.

A filter includes multiple filter circuits. The filter circuits are coupled in series between an input terminal and an output terminal, to generate an output signal according to an input signal. One of the filter circuits operates as an active filter circuit or a passive filter circuit according to amplitude of the input signal.

A variable filter for an RF circuit has a signal loop comprising a signal input port and a signal output port, and a plurality of circuit elements connected within the signal loop. The plurality of circuit elements comprise a multi-pole resonator comprising a plurality of frequency tunable resonators and an adjustable scaling block that applies a gain factor. Adjacent frequency tunable resonators within the multi-pole resonator are reciprocally coupled. A controller is connected to tune the multi-pole resonator and to adjust the gain factor of the adjustable scaling block such that the signal loop generates a desired bandpass response.

A variable filter for an RF circuit has a signal loop comprising a signal input port and a signal output port, and a plurality of circuit elements connected within the signal loop. The plurality of circuit elements comprise a multi-pole resonator comprising a plurality of frequency tunable resonators and an adjustable scaling block that applies a gain factor. Adjacent frequency tunable resonators within the multi-pole resonator are reciprocally coupled. A controller is connected to tune the multi-pole resonator and to adjust the gain factor of the adjustable scaling block such that the signal loop generates a desired bandpass response.

This disclosure is directed to filtering in a transceiver of an electronic device. In some instances, active analog filters may be deployed in the transceiver of the electronic device to achieve greater linearity and/or reduce noise in the transceiver. However, as signal bandwidth grows increasingly larger, an active analog filter may consume excessive power. To remedy the excessive power consumption, a passive ladder LC filter may be used. Some LC ladder filters may include a limited quality factor (Q), which may lead to undesirable effects in the transceiver (e.g., voltage droop). To address these undesirable effects, certain components in the LC ladder filter may be relocated from an input port to a feedback chain of an amplifier coupled to the LC ladder filter. The new structure may enable components in the LC ladder filter to be tuned without causing additional voltage droop across the LC ladder filter.

This disclosure is directed to filtering in a transceiver of an electronic device. In some instances, active analog filters may be deployed in the transceiver of the electronic device to achieve greater linearity and/or reduce noise in the transceiver. However, as signal bandwidth grows increasingly larger, an active analog filter may consume excessive power. To remedy the excessive power consumption, a passive ladder LC filter may be used. Some LC ladder filters may include a limited quality factor (Q), which may lead to undesirable effects in the transceiver (e.g., voltage droop). To address these undesirable effects, certain components in the LC ladder filter may be relocated from an input port to a feedback chain of an amplifier coupled to the LC ladder filter. The new structure may enable components in the LC ladder filter to be tuned without causing additional voltage droop across the LC ladder filter.

An active filter and an analog-to-digital converter (ADC) configured to suppress out-of-band peaking. An active filter may include an active device configured to provide a power gain to an input signal, a feedback network configured to connect an output of the active device to an input of the active device, and an input impedance network configured to couple the input signal to the input of the active device. A combination of the feedback network and the input impedance network is configured to provide frequency response properties of the active filter such that a frequency domain signal transfer function of the active filter has a constant in numerator.

A filter can perform two filtering processes. The filter includes a switching circuit, a first filter circuit, and a second filter circuit. The first filter circuit is coupled to the switching circuit. The second filter circuit is coupled to the switching circuit. The first filter circuit performs a first filtering process on an input signal according to a state of the switching circuit. The first filter circuit and the second filter circuit work together to perform a second filtering process on the input signal according to the state of the switching circuit.