Abstract: The present disclosure describes apparatuses and techniques for shaping near-field transmission signals. In some aspects, a baseband data signal is shaped based on a coupling condition of an antenna. A radio frequency (RF) carrier signal is modulated with the shaped baseband data signal to provide a shaped transmission signal, which is then applied to the antenna to generate an RF field. The shaped transmission signal can be effective to reduce distortions of the RF field associated with the coupling condition.

Abstract: Systems, methods, and other embodiments associated with radio frequency identification (RFID) circuits are described. According to one embodiment, a radio frequency identification circuit includes an antenna network and an integrated circuit configured to operate as a reader and a tag in combination with the antenna network. The integrated circuit is configured to provide an output admittance determined by a ratio of current and voltage negative feedback signals such that a frequency response of the combined integrated circuit and antenna network is adjustable when operating as a reader.

Abstract: Systems, methods, and other embodiments associated with radio frequency identification (RFID) circuits are described. According to one embodiment, a radio frequency identification circuit includes an antenna network and an integrated circuit configured to operate as a reader and a tag in combination with the antenna network. The integrated circuit is configured to provide an output admittance determined by a ratio of current and voltage negative feedback signals such that a frequency response of the combined integrated circuit and antenna network is adjustable when operating as a reader.

Abstract: Systems, methods, and other embodiments associated with radio frequency identification (RFID) circuits are described. According to one embodiment, a radio frequency identification circuit includes an antenna network, including an antenna and an antenna interface coupled to the antenna, wherein the antenna interface includes first and second capacitors, which are coupled in series with the antenna. An integrated circuit includes a first pin and a second pin coupled respectively to a first node and a second node of the second capacitor and configured to operate as a reader and a tag in combination with the antenna network, and an amplifier embedded in the integrated circuit and configured to provide an output admittance determined by a ratio of current and voltage negative feedback signals such that a frequency response of the combined integrated circuit and antenna network is adjustable without increasing power consumption of the RFID when operating as a reader.

Abstract: The present disclosure describes apparatuses and techniques for shaping near-field transmission signals. In some aspects, a baseband data signal is shaped based on a coupling condition of an antenna. A radio frequency (RF) carrier signal is modulated with the shaped baseband data signal to provide a shaped transmission signal, which is then applied to the antenna to generate an RF field. The shaped transmission signal can be effective to reduce distortions of the RF field associated with the coupling condition.

Abstract: A system includes a weighting module, a mixer module, and a frequency selective impedance (FSI). The weighting module is configured to receive an input signal having an amplitude and to generate weighted outputs. Amplitudes of the weighted outputs have ratios relative to the amplitude of the input signal. The mixer module has switches configured to receive the weighted outputs and to generate a staircase waveform when the switches are clocked by clock signals. Amplitudes of steps of the staircase waveform are based on the ratios. The FSI is configured to communicate with the switches. The switches are configured to translate an impedance of the FSI centered on a first frequency to a second frequency determined by a frequency of the clock signals.

Abstract: A polyphase filter comprises an impedance network. The polyphase filter also comprises a first differential amplifier that includes first inverting and non-inverting inputs and first inverting and non-inverting outputs. The first inverting and non-inverting inputs communicate through the impedance network with a first phase and a shifted first phase of an input signal, respectively. A second differential amplifier of the polyphase filter includes second inverting and non-inverting inputs and second inverting and non-inverting outputs. The second inverting and non-inverting inputs communicate with a second phase and a shifted second phase of the input signal, respectively, through the impedance network. The second phase is offset from the first phase.