There are many known methods of retransmitting radio wave signals intra-building and inter-building, as well as ground-to-aircraft or ground-to-satellite. Some techniques modulate the reflection coefficient of an antenna. Prior art has used frequency multiplication or field effect transistor (FET) mixing to modulate the reflection coefficient of an antenna, and therefore the reflected amount of incident power to perform this function. This method is limited by its instantaneous bandwidth to about 50 MHz and its overall efficiency, in addition to the tendency to produce large amounts of harmonics. Other techniques include optical retroreflectors and RFID transponders. Optical retroreflectors reflect the illuminating energy; RFID transponders use a fixed RF frequency with resonant circuits.
There exists a need for a retroreflector that eliminates the power requirements of a local oscillator, and does not suffer the limitations on switching speed of nonlinear junctions that limit instantaneous bandwidth common in prior art.
A novel single-wideband retroreflector was developed that eliminates the need for a local oscillator and a local transmitter. The wideband retroreflector comprises an antenna, a circulator, and a mixer. It transfers data by the illumination of the retroreflector with a continuous wave of RF energy, where the retroreflector both modulates the incoming signal and retransmits it using the incoming signal energy.
The circulator has three physical ports. The first port is connected to the output of the antenna. Signals received at port one of the circulator are preferentially routed to port two. Signals received at ports two and three are similarly routed to the next port.
The mixer has three physical ports: the radio frequency (RF), local oscillator (LO), and intermediate frequency (IF). The mixer LO port is connected to the second port of the circulator, and receives the radio wave signal from the antenna. A user-definable input signal is received at the intermediate frequency port of the mixer. The user-definable input signal modulates the received radio signal. The modulated signal is re-transmitted to the antenna by a connection from the output of the mixer that is connected to the third port of the circulator.
An externally produced, continuous wave, radio wave transmission within the microwave-millimeter wave frequency band is modulated with a wideband signal with a minimum operating instantaneous bandwidth of 5 KHz to 500 MHz, and retransmitted as a modulated waveform by the antenna.