Abstract: Certain aspects of the present disclosure generally relate to electronic circuits and, more particularly, to techniques and apparatus for signal amplification. One example apparatus generally includes: a current sensor configured to sense a current associated with an amplifier; and a voltage sensor configured to sense a voltage associated with the amplifier. The apparatus may also include a logic circuit configured to: detect a first over-current condition associated with the amplifier based on the current; detect a first over-voltage condition associated with the amplifier based on the voltage; and adjust an amplification gain to yield a first adjusted gain level for an input signal based on detection of the first over-current condition and the first over-voltage condition, wherein the amplifier is configured to amplify the input signal based on the first adjusted gain level.

Abstract: Certain aspects of the present disclosure provide techniques for multi-stage impedance tuning for a radio frequency (RF) transmitter. An example apparatus includes RF circuitry comprising an amplifier, an impedance tuning circuit coupled to an output of the amplifier, and an antenna tuner coupled between an antenna feed and an output of the impedance tuning circuit. The apparatus further includes one or more memories and one or more processors coupled to the one or more memories. The one or more processors are configured to cause the apparatus to configure at least one parameter of the impedance tuning circuit or the amplifier based at least in part on at least one load characteristic at the antenna feed; and communicate one or more signals via the RF circuitry while the at least one parameter is configured based at least in part on the at least one load characteristic at the antenna feed.

Abstract: A device includes a first circuit path coupled to a first node and a second node, the first circuit path having at least one first varactor circuit configured to receive a first tuning voltage, the first circuit path having a resistor with a selectable value, and a second circuit path coupled to the first node and the second node, the second circuit path having at least one second varactor circuit configured to receive a second tuning voltage, the second circuit path having a capacitor with a selectable value.

Abstract: A device includes a first circuit path coupled to a first node and a second node, the first circuit path having at least one first varactor circuit configured to receive a first tuning voltage, the first circuit path having a resistor with a selectable value, and a second circuit path coupled to the first node and the second node, the second circuit path having at least one second varactor circuit configured to receive a second tuning voltage, the second circuit path having a capacitor with a selectable value.

Abstract: A method and apparatus for frequency up-converting a baseband signal to radio frequency (RF) in two steps using the two quadrature components of a single local oscillator signal. In a first stage, the baseband signal is split into two parts in quadrature with each other and supplied to a quadrature mixer that mixes the one component of the baseband signal with the I component of a local oscillator signal at frequency FLO and separately mixes the other baseband component with the Q component of the same local oscillator to produce an intermediate frequency signal centered at the local oscillator frequency and comprising two components, namely, an I component and a Q component. In the second stage, the intermediate frequency signal is mixed with both components of the same local oscillator signal in a sub-harmonic mixer-to produce a radio frequency output signal having a frequency component at three times the local oscillator frequency minus the baseband frequency.

Abstract: A method and apparatus for frequency down-converting a radio frequency (RF) signal to baseband in two steps using the two quadrature components of a single local oscillator. In the first stage, the RF signal is mixed with both components of the local oscillator signal (LO) in a sub-harmonic mixer to produce an intermediate frequency (IF) output signal having a frequency component at twice the local oscillator frequency minus the RF frequency, i.e., (2×LO)?RF=IF. In the second stage, the IF signal is split into two and supplied to a quadrature mixer that mixes the IF signal with the I component of the same local oscillator signal and separately mixes the IF signal with the Q component of the same local oscillator signal to produce an output signal comprising an I component and a separate Q component at baseband.

Abstract: An antenna for a radio frequency identification (RFID) system and a method for communicating in an RFID system are provided. The antenna includes a first port configured to provide RFID communication in a first polarization plane and a second port configured to provide RFID communication in a second polarization plane. The first polarization plane is orthogonal to the second polarization plane.

Abstract: A method and apparatus for frequency down-converting a radio frequency (RF) signal to baseband in two steps using the two quadrature components of a single local oscillator. In the first stage, the RF signal is mixed with both components of the local oscillator signal (LO) in a sub-harmonic mixer to produce an intermediate frequency (IF) output signal having a frequency component at twice the local oscillator frequency minus the RF frequency, i.e., (2×LO)?RF=IF. In the second stage, the IF signal is split into two and supplied to a quadrature mixer that mixes the IF signal with the I component of the same local oscillator signal and separately mixes the IF signal with the Q component of the same local oscillator signal to produce an output signal comprising an I component and a separate Q component at baseband.

Abstract: A method and apparatus for frequency up-converting a baseband signal to radio frequency (RF) in two steps using the two quadrature components of a single local oscillator signal. In a first stage, the baseband signal is split into two parts in quadrature with each other and supplied to a quadrature mixer that mixes the one component of the baseband signal with the I component of a local oscillator signal at frequency FLO and separately mixes the other baseband component with the Q component of the same local oscillator to produce an intermediate frequency signal centered at the local oscillator frequency and comprising two components, namely, an I component and a Q component. In the second stage, the intermediate frequency signal is mixed with both components of the same local oscillator signal in a sub-harmonic mixer-to produce a radio frequency output signal having a frequency component at three times the local oscillator frequency minus the baseband frequency.