Metamaterials are described which can be employed with satellites, e.g., small sats, to increase the observability of such satellites. Any type of suitable metamaterial can be used. In exemplary embodiments fractal-based patterns or structures may be used.

A system includes a memory configured to store instructions and a processor that is coupled to the memory. The processor is configured to determine, based on data received from one or more of a reference tag or a positioning sensor tag, a change in a first orientation or position of a portal system platform. The processor is further configured to determine, based on detection data, a second orientation or position of a wireless identification (ID) tag or a change in the second orientation or position. The processor is further configured to determine whether the second orientation or position is valid based on the received data and to perform a response action responsive to determining that the second orientation or position is invalid due to the change of the first orientation or position of the portal system platform.

A method includes: transmitting, from a reader device, a first set of wireless signals, in a first frequency band, detectable by RFID transponder devices; transmitting, from the reader device, a second set of wireless signals, at a second frequency band different from the first frequency band, detectable by the RFID transponder devices; detecting, at the reader device, a set of reply wireless signals transmitted by one or more of the RFID transponder devices in response to the first set of wireless signals, the set of reply signals comprising identification data associated with the one or more of the RFID transponder devices, and orientation information representative of relative orientation of the respective one or more of the RFID transponder devices to the reader device; and deriving location information for at least one of the one or more of the RFID transponder devices based on the detected set of reply wireless signals.

A device for selectively reflecting an incident microwave signal or millimeter-wave signal includes multiple antennae disposed in an array. Each antenna has an input adapted to selectively receive a forward bias signal or a zero bias signal. The device also includes a diode disposed at each input of each antenna. The device also includes a switching device connected to each input, and configured to selectively apply a forward bias or zero bias to each of the diodes. In forward bias, each of the antennae detects the incident microwave signal or millimeter wave signal, and in zero bias, each of the antennae reflects the incident microwave signal or millimeter wave signal.

In a configuration for detection of a movement state of a radio tag using a phase difference of a response wave from the radio tag, a phase [i] and a measurement time t[i] of a response wave from a radio tag measured are sequentially stored in a memory. A difference from a previous phase and a difference from a previous measurement time with respect to each phase [i] stored in the memory are calculated as a phase difference [i] and a time difference t[i]. A phase addition value sum[i] obtained by cumulatively adding a plurality of the phase differences [i] is calculated so as to correct a phase difference in which the corresponding time difference t[i] among the calculated plurality of the phase differences [i] exceeds a time threshold tsa [i], whereby the movement state of the radio tag is detected based upon the calculated phase addition value sum[i].

A harmonic reflector circuit comprising an antenna connected to a non-linear circuit via a matching circuit, wherein the harmonic reflector circuit is configured to receive a signal at a receive frequency (fRX), and configured to transmit said received signal at a transmit frequency (fTX), where the transmit frequency is a multiple of the receive frequency, the harmonic reflector circuit wherein the receive frequency (fRX) is in an interval from a first frequency to a second frequency, where the first frequency is at least 800 MHz; and the second frequency is at least 34 MHz larger than the first frequency; the received signal is transmitted at the transmit frequency (fTX) with an output power (Pout) of at least 70% of the maximum available output power (Pmax).

In some embodiments, a transmitter has a first mode and a second mode. The transmitter is configured to repeatedly send discrete first wireless signals carrying transmitter identification information uniquely associated with the transmitter in the first mode and to send a second wireless signal carrying the transmitter identification information in the second mode. A receiver is configured to receive a wireless signal of the first wireless signals such that the receiver is activated by the wireless signal of the first wireless signal and, in response to receiving the wireless signal of the first wireless signals, to send a third wireless signal carrying the transmitter identification information to the transmitter. The transmitter is configured to transition from the first mode to the second mode in response to receiving the third wireless signal and determining that the third wireless signal includes the transmitter identification information uniquely associated with the transmitter.

A nonlinear radar system includes a handheld unit including a display screen, a first antenna configured to generate and emit an incident signal having a first frequency, and a second antenna configured to receive a reflected return harmonic signal having a second frequency, as well as a transponder tag is attached to an existing golf ball. Such a transponder tag is in communication with and responsive to the handheld unit, and includes an electromagnetic nonlinear element configured to be detected by the incident signal without the need for a line of sight. Upon being detected by the incident signal, the transponder tag is configured to transmit the reflected return harmonic signal having the second frequency different from the first frequency. The transponder tag is passive and does not require a power source other than incident radiation.

In some embodiments, a transmitter has a first mode and a second mode. The transmitter is configured to repeatedly send discrete first wireless signals carrying transmitter identification information uniquely associated with the transmitter in the first mode and to send a second wireless signal carrying the transmitter identification information in the second mode. A receiver is configured to receive a wireless signal of the first wireless signals such that the receiver is activated by the wireless signal of the first wireless signal and, in response to receiving the wireless signal of the first wireless signals, to send a third wireless signal carrying the transmitter identification information to the transmitter. The transmitter is configured to transition from the first mode to the second mode in response to receiving the third wireless signal and determining that the third wireless signal includes the transmitter identification information uniquely associated with the transmitter.

A product locating system is provided. The system includes at least one Radio Frequency (RF) backscatter transmitter configured to emit a main carrier RF signal that forms an excitation signal. The system further includes a passive RF backscatter tag associated with a product and configured to generate an Ultra-Wideband (UWB) signal from the excitation signal. The system also includes at least one RF backscatter receiver configured to simultaneously receive both the excitation signal from the at least one RF backscatter transmitter and the UWB signal from the passive RF backscatter tag, and compute the time-difference-of-arrival (TDoA) therebetween. TDoA information from multiple RF backscatter receivers, including the at least one RF backscatter receiver, is aggregated to compute the location of the product to which the passive RF backscatter tag is attached.