METHOD AND APPARATUS TO PRODUCE A WIDEBAND RF SIGNAL

Abstract

Method and apparatus to produce a wideband RF signal covering an increased first bandwidth, utilizing at least one narrowband transceiver (1) capable of producing an output RF signal with a base frequency f.sub.base and a second bandwidth, wherein the second bandwidth is lower than the first bandwidth, and wherein the base frequency Case depends on the setting of at least one frequency register (2, 2′, 2″), which is adjustable by a control unit, as well as method to estimate the position of a narrowband RF transceiver (1) using a multitude of coherent wideband RF receivers (12) and computer-readable medium comprising computer-executable instructions causing an electronic device to perform the method.

Claims

1-16. (canceled)

17. A computer-implemented method to produce a wideband RF signal covering an increased first bandwidth, utilizing at least one narrowband transceiver capable of producing an output RF signal with a base frequency and a second bandwidth that is lower than the first bandwidth, and an output amplifier capable of broadcasting said signal, wherein the base frequency is adjustable by a control unit, the method comprising: producing, by the at least one transceiver, an output signal at a starting base frequency within the second bandwidth; activating, by the control unit, the output amplifier to broadcast the output signal; and sweeping, by the control unit, the base frequency up or down while the output amplifier is active, in order to have the output signal at least partially cover the first bandwidth.

18. The computer-implemented method of claim 17, wherein the base frequency is changed by altering internal setting of the at least one narrowband transceiver, such as the values of frequency control registers to have the at least one narrowband transceiver increase or decrease the base frequency.

19. The computer-implemented method of claim 17, wherein: the base frequency is consecutively changed by a frequency step, and after each change, the base frequency setting is held constant for a time step.

20. The computer-implemented method of claim 17, wherein prior, during, or after each frequency sweep, the output amplifier broadcasts a continuous wave signal at a fixed and predetermined frequency.

21. The computer-implemented method of claim 17, wherein: the at least one narrowband transceiver produces an output signal at an upper base frequency, and the base frequency is repeatedly reduced from the upper base frequency down to a lower base frequency, or the at least one narrowband transceiver produces an output signal at a lower base frequency, and the base frequency is repeatedly increased from the lower base frequency up to an upper base frequency.

22. The computer-implemented method of claim 21, wherein the value of the frequency step is an integer multiple of the minimum frequency step size of the at least one narrowband transceiver.

23. The computer-implemented method of claim 17, wherein a multitude of frequency sweeps are performed through different overlapping first bandwidths, resulting in covering a third bandwidth larger than each of the overlapping first bandwidths.

24. A computer-implemented method to estimate a position of a narrowband RF transceiver using a plurality of synchronized and/or coherent wideband RF receivers, the method comprising: broadcasting, by the narrowband transceiver, a wideband RF signal covering an increased first bandwidth utilizing the at least one narrowband transceiver capable of producing an output RF signal with a base frequency and a second bandwidth that is lower than the first bandwidth, and an output amplifier capable of broadcasting said signal, wherein the base frequency is adjustable by a control unit, by producing, by the narrowband RF transceiver, an output signal at a starting base frequency within the second bandwidth, activating, by the control unit, the output amplifier to broadcast the output signal, and sweeping, by the control unit, the base frequency up or down while the output amplifier is active, in order to have the output signal at least partially cover the first bandwidth; receiving, by the wideband RF receivers, the wideband RF signal; and determining, by an external computation device, from the position of the wideband RF receivers, the position of the narrowband RF transceiver.

25. The computer-implemented method of claim 24, wherein during the frequency sweep, internal parameters of the narrowband RF transceiver are determined, such as the tolerance of an internal oscillator or the phase offset, the time offset and/or the frequency offset of the output amplifier.

26. The computer-implemented method of claim 25, wherein the following parameters are used to choose parameters of the frequency sweep, in order to ensure that the output signal has reproducible characteristics, such as a change in phase or frequency over time: a start time, a time step, and/or a frequency step of the frequency sweep.

27. The computer-implemented method of claim 26, wherein the parameters are transmitted to an external receiver and used for the correlation of sent and received signals.

28. The computer-implemented method of claim 27, wherein the parameters are transmitted to the external receiver by on/off-modulation of a continuous wave signal broadcast by the output amplifier prior, during, or after the frequency sweep.

29. The computer-implemented method of claim 28, wherein at the external receiver, parameters of the frequency sweep, such as frequency deviation from the ideal, start time, start phase and/or frequency step, are determined by running statistical analysis, such as a least-squares algorithm, over a single or a multitude of received frequency sweeps.

30. A computer-readable medium, comprising computer-executable instructions, which when executed by an electronic device, cause the electronic device to produce a wideband RF signal covering an increased first bandwidth by: producing, by at least one narrowband transceiver capable of producing an output RF signal with an adjustable base frequency and a second bandwidth that is lower than the first bandwidth, and an output amplifier capable of broadcasting said signal, an output signal at a starting base frequency within the second bandwidth; activating the output amplifier to broadcast the output signal; and sweeping the base frequency up or down while the output amplifier is active, in order to have the output signal at least partially cover the first bandwidth.

31. The computer-readable medium of claim 30, wherein the electronic device comprises an electronic shelve label.

32. The computer-readable medium of claim 30, wherein the electronic device comprises a smart sensor.

33. The computer-readable medium of claim 30, wherein the electronic device comprises a fitness tracker.

Description

DRAWINGS

[0039] FIG. 1 shows a schematic overview of an embodiment of a system-on-a-chip comprising an embodiment of an apparatus according to the invention;

[0040] FIGS. 2a through 2d show schematic diagrams of the output signal magnitude over frequency during execution of an embodiment of a method according to the invention;

[0041] FIGS. 3a and 3b show schematic Bode plots of the output signal during execution of an embodiment of a method according to the invention;

[0042] FIG. 3c shows a schematic plot of the frequency and phase error of the output signal over time during execution of an embodiment of a method according to the invention;

[0043] FIG. 4 shows a schematic overview of a system for localization executing an embodiment of a method according to the invention.

DESCRIPTION

[0044] FIG. 1 depicts a schematic block diagram of a system-on-a-chip 5 in which an embodiment of an apparatus according to the invention is implemented, for example as an electronic shelve label (ESL), a remote control, or a smart sensor application such as home automation or fitness tracking devices. Such device can be configured to perform embodiments of the methods as described herein.

[0045] The system-on-a-chip 5 includes, as a control unit, a central processing unit (CPU) 6, such as a microcontroller, ARM microprocessor, or application-specific instruction set processor or the like. The central processing unit 6 is connected to a local system bus 7, such as an ARM Advanced Microcontroller Bus Architecture (AMBA), peripheral component interconnect (PCI) architecture bus or the like.

[0046] Connected to local system bus 7 in the depicted embodiment are a memory controller 8 which interfaces a main memory 9 and frequency registers 2, 2′, 2″, a RF module 3 with transceiver 1, and an input/output (I/O) interface 4. The main memory 9 might be any machine-readable electronic storage medium, including but not limited to nonvolatile, mediums such as read only memories (ROMs) or erasable, electrically programmable read only memories (EEPROMs), Flash memory, SRAM, and the like. The I/O interface 4 may be based on industry standards such as USB, FireWire, Ethernet, USART, I.sup.2S, and the like, and will differ according to the intended application. Wireless networking protocols such as Wi-Fi or Bluetooth may also be supported. Further, an external oscillator 11 is connected to the I/O interface 4 and provides a reference frequency f.sub.ref for the RF module 3.

[0047] The transceiver 1 is part of an RF module 3 and comprises an RF receiver and an RF transmitter, transmitting and receiving through an attached antenna 10. Carrier frequencies used in the RF module 3 might include those in the industrial, scientific and medical (ISM) radio bands such as 433.92 MHz, 915 MHz, 2.45 GHz, and 5.8 GHz wherein channels of narrow bandwidths in the range of 10 kHz to 100 kHz might be provided.

[0048] The RF module 3 may comply with a defined protocol for RF communications such as Zigbee, Bluetooth low energy, or Wi-Fi, or it may implement a proprietary protocol. It might operate in full-duplex or half-duplex mode, and might apply different narrow-band RF signal modulation schemes such as, for example, 2-FSK, GFSK and/or MSK.

[0049] Frequency registers 2, 2′, 2″ might be provided and might be interfaced by the memory controller 8, or might be interfaced separately. In this particular embodiment, the frequency registers comprise a first register 2 (denoted as FREQ0), a second register 2′ (denoted as FREQ1), and a third register 2″ (denoted as FREQ2) of 8-bit each, which together form a 24-bit carrier frequency register. Setting of the frequency registers 2, 2′, 2″ determines the base frequency f.sub.base of the transceiver operation.

[0050] Those of ordinary skill in the art will appreciate that the hardware depicted in FIG. 1 may vary for particular implementations.

[0051] Further possible components, such as power supply, voltage regulator, memory controller, I/O controller, Timer, internal reference oscillator, and the like will be apparent to the skilled person and are therefore not described. The depicted example is provided for the purpose of explanation only and is not meant to imply architectural limitations with respect to the present disclosure.

[0052] FIG. 2a shows a schematic plot of magnitude over frequency of the desired wideband RF signal covering an increased first bandwidth B1, and shows the actual output signal of the transceiver 1 with narrow second bandwidth B2. It can be seen that the output signal of the transceiver 1 is located around f.sub.base+f.sub.channel within a narrow second bandwidth B.sub.2 smaller than the desired first bandwidth B.sub.1. In embodiments not shown, the output signal is a single-frequency carrier with zero bandwidth. The output signal of the transceiver 1 therefore cannot reach the desired first bandwidth B.sub.1.

[0053] FIG. 2b shows the same plot at different time steps while an embodiment of a method according to the invention is carried out. While the channel frequency f.sub.channel is kept constant, the base frequency f.sub.base swept from a low value f.sub.base,low to a high value f.sub.base,high in consecutive time steps t.sub.0<t.sub.1<t.sub.2.

[0054] The value of f.sub.channel has been kept constant and is disregarded in this plot. Thus, by constantly increasing the base frequency of the transceiver 1 in consecutive time steps, a much higher bandwidth of the output signal can be reached.

[0055] FIG. 2c shows the same plot in different time steps while a further embodiment of the method according to the invention is carried out. While the channel frequency f.sub.channel is kept constant, in this embodiment the base frequency f.sub.base is swept from a high value f.sub.base,high to a low value f.sub.base,low in consecutive time steps t.sub.0<t.sub.1<t.sub.2. The value of f.sub.channel is disregarded in this plot. Thus, by constantly reducing the base frequency of the transceiver 1, a much higher bandwidth of the output signal can be reached.

[0056] In further embodiments not shown, the base frequency f.sub.base is swept over the increased bandwidth B.sub.1 in non-consecutive and preferably random time steps.

[0057] FIG. 2d shows a schematic plot of magnitude over frequency at different time steps while a further embodiment of the method according to the invention is carried out. In this embodiment, a multitude N of frequency sweeps are performed through different and overlapping first bandwidths B.sub.1,i=B.sub.1,1, B.sub.1,2, . . . , B.sub.1,N. In this embodiment, the output signal is a single-frequency carrier with different base frequencies f.sub.base,1, f.sub.base,2, . . . , f.sub.base,N with zero bandwidth, denoted in the figure as B.sub.2=0 Hz which is swept over each partial bandwidth B.sub.1,i in order to cover a third bandwidth B.sub.0 which is even larger than each of the overlapping first bandwidths B.sub.1,i.

[0058] FIGS. 3a and 3b show schematic Bode plots of the transceiver's output signal, referenced to an ideal sweep signal, during execution of an embodiment of a method according to the invention.

[0059] According to the embodiment in FIG. 3a, the base frequency of the transceiver f.sub.base is swept from a low value f.sub.base,low to a high value f.sub.base,high in consecutive time steps Δt. The value of f.sub.channel has been kept constant and is disregarded in this plot. Thus, by constantly increasing the base frequency of the transceiver 1 in consecutive time steps, a much higher bandwidth of the output signal is reached. It is shown that the frequency sweep does not follow an ideal straight line, as the PLL of the transceiver will have to accommodate to the desired frequency changes. This leads, in this embodiment, to a small non-linearity in the frequency of the output signal. As seen in the phase plot, however, the time steps Δt and the frequency steps Δf are chosen in such a way that there might be a slight offset, but no significant phase variation during the sweep in the output signal.

[0060] According to the embodiment in FIG. 3b, the base frequency of the transceiver f.sub.base is swept from a high value f.sub.base,high to a low value f.sub.base,low in consecutive time steps Δt. The value of f.sub.channel has been kept constant and is disregarded in this plot. Thus, by constantly decreasing the base frequency of the transceiver 1 in consecutive time steps, a much higher bandwidth of the output signal is reached. It is shown that the frequency sweep does not follow an ideal straight line, as the PLL of the transceiver will have to accommodate to the desired frequency changes.

[0061] This leads, in this embodiment, to a small non-linearity in the frequency of the output signal. As seen in the phase plot, however, the time steps Δt and the frequency steps Δf are chosen in such a way that there is no significant phase variation during the sweep in the output signal.

[0062] FIG. 3c shows a schematic plot of the frequency and phase error Δφ of the output signal over time between the transmitted signals of multiple executions of an embodiment of a method according to the invention. It can be seen that the phase error is more or less negligible during the frequency sweep from f.sub.base,low to f.sub.base,high, but increases at the beginning and end of the frequency sweep. In some embodiments of the invention, frequency sweeps are repeated in order to allow receiving devices to deduce sweep parameters from the received signal and/or to improve localization performance, for example, by averaging received signal waveforms over multiple sweeps.

[0063] FIG. 4 shows a schematic overview of a system for localization of a narrowband transceiver 1, executing an embodiment of a method according to the invention. A narrowband transceiver 1 is located at an unknown position. Three coherent wideband receivers 12 are located at known positions and connected to a computation device 13. The transceiver 1 employs a method according to the invention to broadcast a wideband RF signal. The wideband receivers 12 receive the signal, which, due to the different distance to the transceiver 1, will be phase-shifted. The external computation device 13 calculates a cross-correlation of the received wideband RF signals and extracts, from the phase difference, the resulting time difference of arrival between the received wideband signals. From the difference in time of arrival and the known position of the receivers, the external computation device 13 determines the position of the narrowband RF transceiver 1.

[0064] Further applications of the method according to the invention fall into the scope of the attached claims and will be apparent to the skilled person, thus they need not be described in detail.

LIST OF REFERENCE NUMERALS

[0065] 1 Transceiver [0066] 2, 2′, 2″ Frequency register [0067] 3 RF module [0068] 4 I/O interface [0069] 5 System-on-chip [0070] 6 Central processing unit [0071] 7 Local system bus [0072] 8 Memory controller [0073] 9 Main memory [0074] 10 Antenna [0075] 11 External oscillator [0076] 12 Receivers [0077] 13 Computation device