Abstract: Various embodiments relate to accelerating ramp-down of a modulated signal. In one embodiment, an antenna driver signal is defined and asserted to accelerate ramp-down. The accelerating ramp-down driver signal may include a series of sinusoidal-like pulses asserted at a driver output. The sinusoidal-like pulse may be synchronized by phase to a declining antenna current. Signal properties—such as phase, amplitude, delay, shape and frequency—of the sinusoidal-like pulse may be adopted to affect the ramp-down of the modulated signal.

Abstract: Various embodiments relate to accelerating ramp-down of a modulated signal. In one embodiment, an antenna driver signal is defined and asserted to accelerate ramp-down. The accelerating ramp-down driver signal may include a series of sinusoidal-like pulses asserted at a driver output. The sinusoidal-like pulse may be synchronized by phase to a declining antenna current. Signal properties—such as phase, amplitude, delay, shape and frequency—of the sinusoidal-like pulse may be adopted to affect the ramp-down of the modulated signal.

Abstract: In some implementations, an automatic gain control (AGC) circuit comprises: a pre-divider circuit operable to pre-divide an input signal according to a pre-divider circuit setting and output a pre-divided signal; a pre-amplifier operable to pre-amplify the pre-divided signal and output a pre-amplified signal; a post-divider circuit operable to post-divide the pre-amplified signal according to a post-divider circuit setting; an analog-to-digital converter (ADC) operable to generate a digital data stream from the post-divided signal; logic operable to sample the digital data stream; determine a pre-divider circuit setting and a post-divider circuit setting based on the sampled data stream; set the pre-divider circuit and the post-divider circuit based on the determined settings; and generate a received signal strength value based on the pre-divider circuit setting and the post-divider circuit setting.

Abstract: In some implementations, an automatic gain control (AGC) circuit comprises: a pre-divider circuit operable to pre-divide an input signal according to a pre-divider circuit setting and output a pre-divided signal; a pre-amplifier operable to pre-amplify the pre-divided signal and output a pre-amplified signal; a post-divider circuit operable to post-divide the pre-amplified signal according to a post-divider circuit setting; an analog-to-digital converter (ADC) operable to generate a digital data stream from the post-divided signal; logic operable to sample the digital data stream; determine a pre-divider circuit setting and a post-divider circuit setting based on the sampled data stream; set the pre-divider circuit and the post-divider circuit based on the determined settings; and generate a received signal strength value based on the pre-divider circuit setting and the post-divider circuit setting.

Abstract: In some implementations, an automatic gain control (AGC) circuit comprises: a pre-divider circuit operable to pre-divide an input signal according to a pre-divider circuit setting and output a pre-divided signal; a pre-amplifier operable to pre-amplify the pre-divided signal and output a pre-amplified signal; a post-divider circuit operable to post-divide the pre-amplified signal according to a post-divider circuit setting; an analog-to-digital converter (ADC) operable to generate a digital data stream from the post-divided signal; logic operable to sample the digital data stream; determine a pre-divider circuit setting and a post-divider circuit setting based on the sampled data stream; set the pre-divider circuit and the post-divider circuit based on the determined settings; and generate a received signal strength value based on the pre-divider circuit setting and the post-divider circuit setting.

Abstract: Systems, methods, circuits and computer-readable mediums are disclosed for sign detection in multi-dimensional signal measurements. In some implementations, orthogonally oriented antennas are configured to generate signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space. A circuit is coupled to the antennas and configured to: determine polarities of the signals based on phase measurements between the signals; reduce a possible number of magnetic field vector interpretations based on the determined polarities of the signals; reduce a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic field vector interpretations; compare the reduced possible number of angles or angle differences to predetermined angle or angle differences; and detect a relay attack based on results of the comparing.

Abstract: In some implementations, an automatic gain control (AGC) circuit comprises: a pre-divider circuit operable to pre-divide an input signal according to a pre-divider circuit setting and output a pre-divided signal; a pre-amplifier operable to pre-amplify the pre-divided signal and output a pre-amplified signal; a post-divider circuit operable to post-divide the pre-amplified signal according to a post-divider circuit setting; an analog-to-digital converter (ADC) operable to generate a digital data stream from the post-divided signal; logic operable to sample the digital data stream; determine a pre-divider circuit setting and a post-divider circuit setting based on the sampled data stream; set the pre-divider circuit and the post-divider circuit based on the determined settings; and generate a received signal strength value based on the pre-divider circuit setting and the post-divider circuit setting.

Abstract: In one embodiment, a method includes receiving, at a first device, a first signal transmitted from a first antenna and receiving a second signal after receiving the first signal. The second signal is transmitted from a second antenna after the first signal was transmitted from the first antenna. The method includes determining expected characteristics of an expected signal based on combining the first signal and the second signal. The method includes receiving, at the first device, a third signal comprising signals transmitted from the first antenna and the second antenna substantially simultaneously. The method includes determining whether the third signal comprises at least one characteristic that matches the expected characteristics. In response to determining that the third signal matches the expected signal, the method includes engaging, by the first device, in a communication session with a second device, the second device comprising the first antenna and the second antenna.

Abstract: Systems, methods, circuits and computer-readable mediums are disclosed for sign detection in multi-dimensional signal measurements. In some implementations, orthogonally oriented antennas are configured to generate signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space. A circuit is coupled to the antennas and configured to: determine polarities of the signals based on phase measurements between the signals; reduce a possible number of magnetic field vector interpretations based on the determined polarities of the signals; reduce a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic field vector interpretations; compare the reduced possible number of angles or angle differences to predetermined angle or angle differences; and detect a relay attack based on results of the comparing.

Abstract: Systems, methods, circuits and computer-readable mediums are disclosed for sign detection in multi-dimensional signal measurements. In some implementations, orthogonally oriented antennas are configured to generate signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space. A circuit is coupled to the antennas and configured to: determine polarities of the signals based on phase measurements between the signals; reduce a possible number of magnetic field vector interpretations based on the determined polarities of the signals; reduce a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic field vector interpretations; compare the reduced possible number of angles or angle differences to predetermined angle or angle differences; and detect a relay attack based on results of the comparing.

Abstract: Systems, methods, circuits and computer-readable mediums are disclosed for sign detection in multi-dimensional signal measurements. In some implementations, orthogonally oriented antennas are configured to generate signals in response to a magnetic field, where the signals correspond to components of magnetic field vectors in space. A circuit is coupled to the antennas and configured to: determine polarities of the signals based on phase measurements between the signals; reduce a possible number of magnetic field vector interpretations based on the determined polarities of the signals; reduce a possible number of angles or angle differences between the magnetic field vectors based on the reduced possible number of magnetic field vector interpretations; compare the reduced possible number of angles or angle differences to predetermined angle or angle differences; and detect a relay attack based on results of the comparing.

Abstract: A circuit, use, and method for controlling a receiver circuit is provided, wherein a complex baseband signal is generated from a received signal, a phase difference between a phase of the complex baseband signal and a phase precalculated from previous sampled values is determined, the phase difference is compared with a first threshold, a number is determined by counting the exceedances of the first threshold by the phase difference, a number of the counted exceedances is compared with a second threshold, and the receiver circuit is turned off if the number of counted exceedances exceeds the second threshold within a time period.

Abstract: A method for controlling a receiver circuit and circuit with a receiver circuit and with a control circuit is provided, whereby a received signal is demodulated and filtered. An amplitude value of the demodulated and filtered signal is compared with thresholds of a window comparator. A zero crossing of the demodulated and filtered signal is compared with time thresholds of a time window by a comparison unit. A first output value of the window comparator and a second output value of the comparison unit are logically combined, and wherein, via the logical combination, the receiver circuit is turned off if, within a period of time, the amplitude value is determined to be outside a window formed by the thresholds of the window comparator, or a zero crossing is determined to be outside the time window.

Abstract: A circuit, use, and method for controlling a receiver circuit is provided, wherein a complex baseband signal is generated from a received signal, a phase difference between a phase of the complex baseband signal and a phase precalculated from previous sampled values is determined, the phase difference is compared with a first threshold, a number is determined by counting the exceedances of the first threshold by the phase difference, a number of the counted exceedances is compared with a second threshold, and the receiver circuit is turned off if the number of counted exceedances exceeds the second threshold within a time period.

Abstract: A circuit, use, and method for controlling a receiver circuit is provided, wherein a complex baseband signal is generated from a received signal, a phase difference between a phase of the complex baseband signal and a phase precalculated from previous sampled values is determined, the phase difference is compared with a first threshold, a number is determined by counting the exceedances of the first threshold by the phase difference, a number of the counted exceedances is compared with a second threshold, and the receiver circuit is turned off if the number of counted exceedances exceeds the second threshold within a time period.

Abstract: In one embodiment, a method includes receiving, at a first device, a first signal transmitted from a first antenna and receiving a second signal after receiving the first signal. The second signal is transmitted from a second antenna after the first signal was transmitted from the first antenna. The method includes determining expected characteristics of an expected signal based on combining the first signal and the second signal. The method includes receiving, at the first device, a third signal comprising signals transmitted from the first antenna and the second antenna substantially simultaneously. The method includes determining whether the third signal comprises at least one characteristic that matches the expected characteristics. In response to determining that the third signal matches the expected signal, the method includes engaging, by the first device, in a communication session with a second device, the second device comprising the first antenna and the second antenna.

Abstract: A circuit for a loop antenna having a first antenna terminal and a second antenna terminal with an antenna impedance, and method for tuning an overall impedance that has an antenna impedance of a loop antenna and a tuning impedance, with an output amplifier for amplifying a transmit signal that has an output for connection to the first antenna terminal of the loop antenna, with a tuning device designed for automatic tuning that has a terminal, which is separated from the output of the output amplifier for connection to the second antenna terminal, in which the tuning device has an adjustable tuning impedance that is connected to the terminal, in which the tuning device has a measurement device that is connected to the tuning impedance in order to measure a voltage amplitude across the tuning impedance, in which the tuning device has a computing unit that is connected to the measurement device and the adjustable tuning impedance, and in which the computing unit is designed for automatic adjustment of the tunin

Abstract: A receiving circuit and method for receiving an amplitude shift keying signal is provided. At least one exponent signal, an exponent-removed in-phase signal, and an exponent-removed quadrature-phase signal are generated from an in-phase input signal and a quadrature-phase input signal. An amplitude is determined as a sum of several summands, whereby the summands are determined from the exponent signal and/or from the exponent-removed in-phase signal and/or from the exponent-removed quadrature-phase signal (Q?), and wherein the amplitude (A) is demodulated.

Abstract: A method for controlling a receiver circuit and circuit with a receiver circuit and with a control circuit is provided, whereby a received signal is demodulated and filtered. An amplitude value of the demodulated and filtered signal is compared with thresholds of a window comparator. A zero crossing of the demodulated and filtered signal is compared with time thresholds of a time window by a comparison unit. A first output value of the window comparator and a second output value of the comparison unit are logically combined, and wherein, via the logical combination, the receiver circuit is turned off if, within a period of time, the amplitude value is determined to be outside a window formed by the thresholds of the window comparator, or a zero crossing is determined to be outside the time window.

Abstract: A method detects relaying of a contactless data communication by a radio amplifier for intercepting and manipulating the communication to achieve an unauthorized authentication. The method involves transmitting an electromagnetic field successively from at least two spatially separated antennas of a transmitting unit, receiving the transmitted fields in a receiving unit, determining field strength vectors of the received fields allocated to each antenna, and comparing actual values of the vectors with prescribed nominal values stored in a nominal value field that maps the true field strength distribution in multi-dimensional space around the transmitting unit. The actual field strength magnitude and the reception angle between the transmitting antennas can be determined from the vectors and compared with stored nominal values in this manner. When the determined actual values match prescribed nominal values of the nominal value field, the occurrence of a relaying of the signal can be reliably excluded.