Standing wave cancellation wireless transmitter, receiver, system and respective method

Abstract

The present invention is enclosed in the area of wireless communication systems, generally towards the problem of multipath interference, and specifically towards mitigating the effect of standing wave in indoor positioning systems. The present invention includes a standing wave cancellation wireless transmitter configured to, for each signal with wavelength λ to be transmitted, transmit a first wave with wavelength λ and a second wave with wavelength λ and a shift equal to half the wavelength λ. It is also part of present invention a standing wave cancellation wireless receiver configured to perform the average of a first wave with wavelength λ and a second wave with wavelength λ and a shift equal to half the wavelength λ, creating a single received signal and a system comprising at least one of said wireless transmitters and at least one of said wireless receivers and a method implemented by the said transmitter and receiver.

Claims

1. A standing wave cancellation wireless transmitter, the wireless transmitter being configured to, for each signal with wavelength to be transmitted, transmit a first wave with wavelength and transmit a second wave with wavelength and a phase shift equal to half the wavelength and wherein the wireless transmitter comprises: (a) a signal generator suitable for creating a signal with wavelength, (b) an output, and (c) a relay switch, configured so that the relay switch: (A) alternatively connects the signal generator through a first path generating a first wave and through a second path to the output, and (B) wherein the second path is connected to a means for delivering the signal shifted in half the wavelength, creating the second wave.

2. The standing wave cancellation wireless transmitter according to claim 1 characterized in that the relay switch is a single pole double throw (SPDT) relay switch, the output a speaker and the signal generator is an ultrasonic signal generator with two outputs: i) a first output which outputs an ultrasound wave with wave wavelength and ii) a second output which outputs a second wave with wavelength and a phase shift equal to half the wavelength, wherein the second output consists of the means for delivering the signal shifted in half the wavelength.

3. Standing wave cancellation wireless transmitter according to claim 1 characterized in that the relay switch is a Double Pole Double Throw (DPDT) relay switch, the output an antenna, the signal generator is a radio signal generator and the means for delivering the signal shifted in half the wavelength consist of a coaxial cable.

4. Standing wave cancellation wireless transmitter according to claim 1 characterized in that it is further configured to implement time division multiplexing.

5. Use of the transmitter of claim 1 in positioning systems, preferably indoor positioning systems.

Description

DESCRIPTION OF DRAWINGS

(1) The features of the invention believed to be innovative are set forth with particularity in the claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes exemplary embodiments of the invention, taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1—a graph displaying the effect of the standing wave on the indoor positioning system estimation, along with the effect of the mitigation used within the system.

(3) FIG. 2—a schematic view of the electric circuit of a wireless transmitter (1) according to the present invention, used to mitigate the standing wave effect in radio wave transmission, representing means for delivering the signal shifted in half the wavelength λ (4) as a coaxial cable, a relay switch (3) as a double pole double throw switch, the output (5) as an antenna and the signal generator (2).

(4) FIG. 3—a schematic view of the electric circuit of a wireless transmitter (1) according to the present invention, used to mitigate the standing wave effect in ultrasound transmission, representing a relay switch (3) as a single pole double throw switch, the output (5) as a speaker and the signal generator (2).

(5) FIG. 4—a graph displaying linear estimations of signal strength trend lines gained from measuring signals from different pairs of transmitters after the standing wave cancelation process, in a range of approximately 12 meters. It is gained from measuring signals from different pairs of transmitters. This graph contains a number of lines equal to the number of emitter pairs inside an example scenario (not limited to three pairs).

DETAILED DESCRIPTION OF THE INVENTION

(6) The most general configurations of the present invention are defined in the Summary of the invention. These configurations may be further detailed. The standing wave cancellation wireless transmitter (1) may further comprise a signal generator (2) suitable for creating a signal with wavelength λ, an output (5) and a relay switch (3), connected so that a relay switch (3) alternatively connects the signal generator (2) through a first path generating a first wave and through a second path to the output (5), wherein the second path is connected to means for delivering the signal shifted in half the wavelength λ (4), creating the second wave. It consists of a possible implementation of the previously defined transmitter, delivering two waves, in which the second wave is shifted in half the wavelength.

(7) When the relay switch (3) is in the initial position, the signal generator (2) transmits a first wave directly to the output (5). The signal generator (2) may also control the relay switch (3), so when it switches the relay switch (3) to the alternate position, the signal comes from the means for delivering the signal shifted in half the wavelength λ (4), and then to the output (5). Therefore, the second wave will have a half wavelength delay in relation to the first wave.

(8) The transmitter of the present invention may implement radio or ultrasound communications.

(9) In an embodiment specifically for radio communications, said signal generator (2) is a radio signal generator, the relay switch (3) is a Double Pole Double Throw (DPDT) relay switch (3), the output (5) an antenna and the means for delivering the signal shifted in half the wavelength λ (4) consist of a coaxial cable. The half wavelength delay generated by the correct length of the coaxial cable (see FIG. 2) generates the second radio wave. A radio wireless transmitter (1) according to the present invention uses the DPDT relay switch (3) to emit two radio waves—possibly in time-division multiplexing-, thus mitigating the effect of the standing wave by summing up the two waves before processing them. The dashed line in FIG. 2 surrounding all of the elements besides the antenna represents a metallic enclosure that serves as a reflector and isolator of the radio signal contained inside the electric circuit.

(10) In this case, when the DPDT relay switch (3) is in the initial position, the radio signal generator (2) transmits a first wave directly to the output (5) using the shortest path possible. The signal generator (2) may also control the DPDT relay switch (3), so when it switches the relay switch (3) to the alternate position, the signal passes through a coaxial cable of a certain length, and then to the output (5). This causes the half wavelength delay generated by the correct length of the coaxial cable and generates the second wave. The dashed line surrounding all of the elements besides the antenna represents a metallic enclosure that serves as a reflector and isolator of the radio signal contained inside the electric circuit.

(11) Specifically for ultrasound communications, the relay switch (3) is a Single Pole Double Throw (SPDT) relay switch (3), the output (5) a speaker and the signal generator (2) is an ultrasonic signal generator with two outputs: i) a first output which outputs an ultrasound wave with wave wavelength λ and ii) a second output which outputs a second wave with wavelength λ and a phase shift equal to half the wavelength λ, wherein the second output consists of the means for delivering the signal shifted in half the wavelength λ (4). Similarly to what was referred to radio communications and considering FIG. 3, which displays a hardware-based solution that implements the standing wave mitigation for ultrasound waves, the ultrasound transmitter is connected to a SPDT relay switch (3), which enables the signal generator (2) to switch between two audio outputs. One of the outputs is a regular A wavelength ultrasound wave. The other audio output (5) outputs the same ultrasound wave, but with a phase shift for λ/2.

(12) In a preferred embodiment relative to both the radio and ultrasound implementations, the transmitter of the present invention is further configured to implement time division multiplexing which, as said, mitigates the effect of the standing wave by summing up the two waves before processing them.

(13) Considering the wireless receiver of the present invention, said average performed to the first and second received waves, it is the average of the amplitude or power of said first and second waves.

(14) Also, the wireless receiver of the present invention may implement radio or ultrasound communications.

(15) Specifically for radio communications, it comprises an antenna and radio wave transducer means.

(16) Specifically for ultrasound communications, it comprises a microphone and ultrasound transducer means.

(17) The system defined in Summary of the invention may include a wireless transmitter (1) and a wireless receiver as defined in any of previously defined embodiments.

(18) Also, the method defined in Summary of the invention may also be implemented by this system, including its previously referred embodiment. This method may still be further detailed in that it comprises the following steps: a signal with wavelength λ is generated in a wave generator; said signal is inserted into a first path and into a second path by means of a relay switch (3); the signal transmitted through the second path is shifted in half the wavelength λ; both the signal from the first path and the signal from the second path are wirelessly transmitted through the output (5).

(19) Also, in any of the embodiments of said method, the signal may be a radio signal or an ultrasound signal.

(20) The present invention also includes the use of the previously referred transmitter, receiver or system, in any of the detailed embodiments, in positioning systems, preferably indoor positioning systems.

(21) The several embodiments described are combinable.

(22) Each of the claims of the following set of claims defines specific embodiments.