WO2021228279A1

WO2021228279A1 - Method and system for controlling backscatter circuit based on multi-subcarrier modulation

Info

Publication number: WO2021228279A1
Application number: PCT/CN2021/101724
Authority: WO
Inventors: 朱丰源; 冯宇达; 李倩茹; 田晓华; 王新兵
Original assignee: 上海交通大学
Priority date: 2020-05-13
Filing date: 2021-06-23
Publication date: 2021-11-18
Also published as: CN111683031B; CN111683031A

Abstract

Provided are a method and system for controlling backscatter circuit based on multi-subcarrier modulation, comprising: a multi-subcarrier modulation algorithm for backscatter tags; step M1: a phase-based digital oscillator determining a final logic output 0/1; step M2: according to the logic output of the multi-phase digital oscillator, on the basis of an output decision module, determining a logic value 0/1 of a final control signal outputted to a radio-frequency switch; said output decision module is the logic output of the multi-phase digital oscillator to vote for the logic value of the control signal finally outputted to the radio-frequency switch. The method of the present invention can be used for any backscattering or non-traditional backscattering circuit. The invention achieves an algorithm of which multi-carrier is the digital domain, without limiting an analog circuit.

Description

Method and system for controlling backscatter circuit based on multi-subcarrier modulation

Technical field

The present invention relates to the field of communications, in particular, to a method and system for controlling a backscatter circuit based on multi-subcarrier modulation, and more specifically, to an algorithm that can realize multi-subcarrier modulation and how to provide the output of the algorithm For the circuit, and there are no restrictions on the backscattered radio frequency circuit.

Background technique

Backscatter communication has attracted widespread attention in the field of Internet of Things in recent years. Its main feature is to use external electromagnetic waves to modulate to realize its own communication. Since there is no need to actively generate electromagnetic waves, even if it is generated for Wi-Fi communication, the power consumption is very low, only tens of microwatts (see the paper by Bryce Kellogg et al. in NSDI in 2016). However, the current backscatter equipment still has three problems: (a) the communication rate is too low, (b) the network capacity is not enough, (c) the support for long-distance protocols is not enough. In terms of speed, the current highest-speed backscatter communication device can only upload data at the physical layer at 11 Mbps (Bryce Kellogg, 2016). In terms of capacity, current backscatter devices can only support 48 devices to communicate in the same Wi-Fi frequency band. In support of long-distance protocols, the current backscatter system only supports LoRa protocol (Vamsi Talla, Mehrdad Hessar, 2017), but does not have the ability to support other long-distance protocols, such as LTE-M. The multi-subcarrier modulation technology is of great help in solving the above three problems. OFDM technology is a typical multi-subcarrier modulation technology, which has extremely high spectrum utilization rate and is suitable for high-speed communication; while OFDMA technology based on OFDM is a key technology to increase capacity and is used in the new generation of 802.11 protocols and 4G and 5G networks; In addition, the LTE-M protocol also requires multi-subcarrier modulation to be compatible with the physical layer mode of LTE.

Patent document CN106506426B (application number: 201610885466.3) discloses a backscatter communication modulation method based on OFDM (Orthogonal Frequency Division Multiplexing) carrier. The modulation method of the present invention is used in a backscatter communication system. The backscatter communication system includes a radio frequency source, a reader, and a tag; the main steps are: the radio frequency source transmits an OFDM carrier signal to the tag; the tag receives the OFDM signal, and the tag It also includes a backscatter antenna and a radio frequency energy collection module, the radio frequency energy collection module is used to collect energy from the OFDM signal in the tag environment, the backscatter antenna is used to send information bits to the reader; the reader receives and Decode the backscattered signal from the tag.

Summary of the invention

In view of the defects in the prior art, the purpose of the present invention is to provide a method and system for controlling a backscatter circuit based on multi-subcarrier modulation.

According to the present invention, a method for controlling a backscatter circuit based on multi-subcarrier modulation includes: a multi-subcarrier modulation algorithm for backscatter tags;

Step M1: Determine the logic output 0/1 based on the phase-based digital oscillator;

Step M2: According to the logic output of the digital oscillators of multiple phases, based on the output decision module, determine the logic value 0/1 of the control signal finally output to the RF switch;

The output decision module is the logic output of the digital oscillator of multiple phases to vote for the logic value of the control signal finally output to the radio frequency switch.

Preferably, the step M1 includes:

The phase-based digital oscillator stores the specific phase in the register according to the preset sampling clock each time according to the sub-carrier frequency of the phase-based digital oscillator and adds the phase stored in the original register; each time it stores the specific phase The phase is a fixed value, and the digital oscillator judges the interval according to the phase addition value, and then determines the logic output 0/1.

Preferably, the digital oscillator making interval judgment according to the phase addition value includes: the digital oscillator making interval judgment according to the fractional part after the phase addition and/or the digital oscillator making a uniform numerical change according to the phase addition value, so that The decimal point in the phase addition value is moved, and the phase addition integer is obtained for interval judgment.

Preferably, the step M2 includes: multi-subcarrier modulation requires multiple digital oscillators, and multiple digital oscillators provide multiple 0/1 outputs; based on the output decision module, according to the voting method, determine the final output to the RF switch The logic value of the control signal is 0/1.

Preferably, the voting method is based on multiple logic values 0/1 provided by multiple digital oscillators. When the number of logic values 0 is greater than the number of logic values 1, the final output is logic value 0; when the logic value is 0 If the number is less than the number of logical value 1, then the final output is logical value 1. When the number of logical value 0 is equal to the number of logical value 1, then logical value 0 or logical value 1 is finally output.

Preferably, the carrier of the multi-subcarrier modulation algorithm of the backscatter tag includes: a microcontroller and an editable logic circuit.

According to the present invention, a system for controlling a backscatter circuit based on multi-subcarrier modulation includes: a multi-subcarrier modulation algorithm for backscatter tags;

Module M1: Phase-based digital oscillator, which determines the logic output 0/1;

Module M2: According to the logic output of the digital oscillator of multiple phases, based on the output decision module, determine the logic value 0/1 of the control signal finally output to the RF switch;

Preferably, the module M1 includes:

The phase-based digital oscillator stores the specific phase in the register according to the preset sampling clock each time the sampling clock is based on the subcarrier frequency of the phase digital oscillator and adds the phase stored in the original register; each time the specific phase is stored The phase is a fixed value, and the digital oscillator judges the interval according to the added value of the phase, and then determines the logic output 0/1;

The digital oscillator making interval judgment according to the phase addition value includes: the digital oscillator makes interval judgment according to the fractional part after the phase addition and/or the digital oscillator makes a uniform numerical change according to the phase addition value, so that the phase is added The decimal point in the value is moved, and the phase is added to the integer for interval judgment.

Preferably, the module M2 includes: multi-subcarrier modulation requires multiple digital oscillators, and multiple digital oscillators provide multiple 0/1 outputs; based on the output decision module, according to the voting method, decide the final output to the RF switch The logic value of the control signal is 0/1;

The voting method is based on multiple logic values 0/1 provided by multiple digital oscillators. When the number of logic values 0 is greater than the number of logic values 1, the final output is logic value 0; when the number of logic values 0 is less than the logic value 1, If the number of value 1, then the final output is logic value 1. When the number of logic value 0 is equal to the number of logic value 1, then finally output logic value 0 or logic value 1.

Compared with the prior art, the present invention has the following beneficial effects:

1. The method proposed by the present invention enables the backscatter device to realize multi-subcarrier modulation, thereby supporting a wider range of communication protocols.

2. The method of the present invention enables the backscatter device to communicate in OFDM mode, thereby obtaining higher spectrum efficiency.

3. The method of the present invention can be applied to any backscattering or non-traditional backscattering circuit. Realize the multi-carrier algorithm in the digital domain without restricting the analog circuit;

4. Since the final output is a 1-bit logic control signal, it is compatible with any existing backscatter circuit; this is because backscatter communication naturally requires impedance switching function; and the logic generated by the algorithm provided by the present invention The signal can be used to control impedance switching. The logic signal generated by the algorithm provided by the present invention can be used to control impedance switching.

Description of the drawings

By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, purposes and advantages of the present invention will become more apparent:

Fig. 1 is a sample design scheme of a phase-based digital oscillator in the present invention.

Fig. 2 is a schematic diagram of the output decision maker in the present invention deciding output according to the input of multiple digital oscillators.

The use of four digital oscillators in FIG. 2 is only an example, and the present invention does not limit the number of digital oscillators or the number of sub-carriers.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be pointed out that for those of ordinary skill in the art, several changes and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

The invention provides a multi-subcarrier modulation technique suitable for backscatter communication. This technology is an algorithm in the digital domain. Only two switchable impedances are required on the radio frequency circuit to support multi-subcarrier modulation, and it can be applied to most existing backscatter circuits.

Example 1

According to the present invention, a method for controlling a backscatter circuit based on multi-subcarrier modulation includes: a multi-subcarrier modulation algorithm for backscatter tags; as shown in Fig. 2,

Specifically, the step M1 includes:

The phase-based digital oscillator stores the specific phase in the register according to the preset sampling clock each time the sampling clock is based on the subcarrier frequency of the phase digital oscillator and adds the phase stored in the original register; each time the specific phase is stored The phase is a fixed value, and the digital oscillator judges the interval according to the phase addition value, and then determines the logic output 0/1.

The phase stored in the original register means that the register is a storage device, and a value must be stored in it. After initialization, the value is 0. As the system runs, this value will change (because our algorithm will assign a new value to it). Use this value to represent the phase. So the phase stored here refers to the value in the current register.

The phase stored in the next clock in the register = the original phase (in the register) + Delta phase. Among them, the Delta phase is a fixed value when the subcarrier is fixed, Delta\phi=k/N. Where k is the subcarrier number, and N is a constant (the total number of subcarriers in the system). Of course, if we change the sub-carrier assigned to this device, k will change and the Delta phase will also change.

Specifically, the digital oscillator making interval judgment according to the phase addition value includes: the digital oscillator making interval judgment according to the fractional part after the phase addition and/or the digital oscillator making a uniform numerical change according to the phase addition value, so that The decimal point in the phase addition value is moved, and the phase addition integer is obtained for interval judgment.

Step M2: According to the logic output of the digital oscillator of multiple phases, based on the output decision module, determine the logic value 0/1 of the control signal finally output to the RF switch; that is, the control signal for controlling the RF switch comes from the multi-subcarrier modulation algorithm ；

For example: there are a oscillators, and a oscillators work independently. According to the above rules, a oscillator may generate an output of 0/1, and there are 2^a possibilities. In the chip, the operations of a oscillators are parallel, and the outputs are also simultaneous. However, the signal that our backscattering device ultimately controls the RF switch cannot have a signal, but can only be determined by a logic signal 0/1 to determine the final output. This is the function of the output decision module, which is based on the output of a oscillator to vote to choose whether it is 0 or 1 in the end.

Specifically, the step M2 includes: multi-subcarrier modulation requires multiple digital oscillators, and multiple digital oscillators provide multiple 0/1 outputs; based on the output decision module, according to the voting method, determine the final output to the RF switch The logic value of the control signal is 0/1.

Specifically, the voting method is based on multiple logic values 0/1 provided by multiple digital oscillators. When the number of logic values 0 is greater than the number of logic values 1, the final output is logic value 0; when the logic value is 0 If the number is less than the number of logical value 1, then the final output is logical value 1. When the number of logical value 0 is equal to the number of logical value 1, then logical value 0 or logical value 1 is finally output.

Specifically, the carrier of the multi-subcarrier modulation algorithm of the backscatter tag includes: a microcontroller (MCU) and an editable logic circuit, such as PLD/CPLD/FPGA.

Other active/passive circuits that use the multi-subcarrier modulation algorithm of the present invention, for example, use the state of switching power amplifiers on an active radio frequency circuit and use the multi-subcarrier modulation algorithm of the present invention, which is based on the multi-subcarrier modulation algorithm of the present invention. The sub-carrier modulation algorithm controls the state of the active radio frequency circuit to switch the power amplifier.

Since the final output is a 1-bit logic control signal, it is compatible with any existing backscatter circuit; this is because backscatter communication naturally requires impedance switching function; and the logic signal generated by the algorithm provided by the present invention is that Can be used to control impedance switching.

Specifically, the module M1 includes:

As shown in Figure 1, the phase-based digital oscillator stores a specific phase in the register according to the preset sampling clock each time the sampling clock is based on the sub-carrier frequency of the phase digital oscillator and adds the phase stored in the original register; Each time a specific phase is stored as a fixed value, the digital oscillator makes interval judgments based on the phase addition value, and then determines the logic output 0/1.

Module M2: According to the logic output of the digital oscillator of multiple phases, based on the output decision module, determine the logic value 0/1 of the control signal finally output to the RF switch; that is, the control signal for controlling the RF switch comes from the multi-subcarrier modulation algorithm ；

The output decision module is the logic output of the digital oscillator of multiple phases to vote to select the logic value of the control signal that is finally output to the radio frequency switch.

Specifically, the module M2 includes: multi-subcarrier modulation requires multiple digital oscillators, multiple digital oscillators provide multiple 0/1 outputs; based on the output decision module, according to the voting method, determine the final output to the RF switch The logic value of the control signal is 0/1.

Example 2

Example 2 is a variation of Example 1

For the convenience of description, it is specified that the phase is equal to the physical phase/2. But the actual calculation in the chip is a fixed-point number, which can be mapped with the phase here, such as multiplying by 1024 uniformly, which will cause the decimal point to move. For example, 0.5 in the physical world can be expressed as 512 (multiplied by 1024) in the chip, and can be stored in the chip as a 10-bit unsigned integer. In this case, the integer part is n times 1024, and the decimal is The part less than 1024, so that when we do addition, the physical world discards the integer part and retains the decimal part. The operation is equivalent to retaining only the lowest 10bit and discarding the 11th bit that may be generated by the addition of two 10-bit numbers. These two methods are essentially equivalent.

Example 3

Example 3 is a variation of Example 1 and/or Example 2

The determination of the interval of the digital oscillator according to the fractional part after the phase addition includes:

The simplest interval is (0,0.5) judged as "0"; (0.5,1) judged as "1". The case greater than 1 does not exist because the integer part has been discarded. It will not be less than 0, because the phase storage format is an unsigned positive number. Of course, this is not the only judgment interval, as long as it is satisfied that the two intervals are complementary between (0,1) and each occupy a length of 0.5 (but must be continuous). For example, (0,0.1) and (0.6,1) are judged as "0", and (0.1,0.6) is judged as "1". There are countless such options. Phase 0 and Phase 1, according to the previous mapping rules, before normalization, they should actually be 0 and 2π, so these two points are the same point, so (0,0.1) and (0.6,1) are one Continuous interval.

Those skilled in the art know that, in addition to implementing the system, device and various modules provided by the present invention in a purely computer-readable program code manner, it is completely possible to make the system, device and various modules provided by the present invention by logically programming method steps The same program is implemented in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system, device and various modules provided by the present invention can be regarded as a hardware component, and the modules included in it for implementing various programs can also be regarded as the structure within the hardware component; The modules for realizing various functions can be regarded as both software programs for realizing methods and structures within hardware components.

The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

A method for controlling a backscatter circuit based on multi-subcarrier modulation, which is characterized by comprising: a multi-subcarrier modulation algorithm for backscatter tags;

Step M1: Determine the logic output 0/1 based on the phase-based digital oscillator;

Step M2: According to the logic output of the digital oscillator of multiple phases, based on the output decision module, determine the logic output 0/1 of the control signal finally output to the RF switch;

The output decision module is used for the logic output of the digital oscillator with multiple phases to vote to select the logic value of the control signal finally output to the radio frequency switch.
The method for controlling a backscatter circuit based on multi-subcarrier modulation according to claim 1, wherein the step M1 comprises:

The phase-based digital oscillator stores the specific phase in the register according to the preset sampling clock each time the sampling clock is based on the subcarrier frequency of the phase digital oscillator and adds the phase stored in the original register; each time the specific phase is stored The phase is a fixed value, and the digital oscillator judges the interval according to the phase addition value, and then determines the logic output 0/1.
The method for controlling a backscatter circuit based on multi-subcarrier modulation according to claim 2, wherein the digital oscillator performs interval judgment according to the phase addition value comprises: the digital oscillator according to the fractional part of the phase addition Do interval judgment and/or the digital oscillator makes a uniform numerical change according to the phase addition value, so that the decimal point in the phase addition value is moved, and the phase addition integer is obtained for interval judgment.
The method for controlling a backscatter circuit based on multi-subcarrier modulation according to claim 1, wherein the step M2 comprises: multi-subcarrier modulation requires multiple digital oscillators, and multiple digital oscillators provide multiple zeros. /1 output; based on the output decision module, according to the voting method, determine the logic value 0/1 of the control signal finally output to the RF switch.
The method for controlling a backscatter circuit based on multi-subcarrier modulation according to claim 4, wherein the voting method is based on a plurality of logic values 0/1 provided by a plurality of digital oscillators output, when the logic value is 0 If the number of is greater than the number of logical value 1, then the final output is logical value 0; when the number of logical value 0 is less than the number of logical value 1, then the final output logical value 1; when the number of logical value 0 is equal to the number of logical value 1, then Finally, a logic value of 0 or a logic value of 1 is output.
The method for controlling a backscatter circuit based on multi-subcarrier modulation according to claim 1, wherein the carrier of the multi-subcarrier modulation algorithm of the backscatter tag comprises: a microcontroller and an editable logic circuit.
A system for controlling a backscatter circuit based on multi-subcarrier modulation, which is characterized by comprising: a multi-subcarrier modulation algorithm for backscatter tags;

Module M1: Phase-based digital oscillator, which determines the logic output 0/1;

Module M2: According to the logic output of the digital oscillator of multiple phases, based on the output decision module, determine the logic output 0/1 of the control signal finally output to the RF switch;

The output decision module is used for the logic output of the digital oscillator with multiple phases to vote to select the logic value of the control signal finally output to the radio frequency switch.
The system for controlling the backscatter circuit based on multi-subcarrier modulation according to claim 7, wherein the module M1 comprises:

The phase-based digital oscillator stores the specific phase in the register according to the preset sampling clock each time the sampling clock is based on the subcarrier frequency of the phase digital oscillator and adds the phase stored in the original register; each time the specific phase is stored The phase is a fixed value, and the digital oscillator judges the interval according to the added value of the phase, and then determines the logic output 0/1;

The digital oscillator making interval judgment according to the phase addition value includes: the digital oscillator makes interval judgment according to the fractional part after the phase addition and/or the digital oscillator makes a uniform numerical change according to the phase addition value, so that the phase is added The decimal point in the value is moved, and the phase is added to the integer for interval judgment.
The system for controlling the backscatter circuit based on multi-subcarrier modulation according to claim 7, wherein the module M2 includes: multi-subcarrier modulation requires multiple digital oscillators, and multiple digital oscillators provide multiple zeros. /1 output; based on the output decision module, according to the voting method, determine the logic value 0/1 of the control signal finally output to the RF switch;

The voting method is based on multiple logic values 0/1 provided by multiple digital oscillators. When the number of logic values 0 is greater than the number of logic values 1, the final output is logic value 0; when the number of logic values 0 is less than the logic value 1, If the number of value 1, then the final output is logic value 1. When the number of logic value 0 is equal to the number of logic value 1, then finally output logic value 0 or logic value 1.
The system for controlling the backscatter circuit based on multi-subcarrier modulation according to claim 7, wherein the carrier of the multi-subcarrier modulation algorithm of the backscatter tag comprises: a microcontroller and an editable logic circuit.