CN116546455A - Passive communication method, passive communication system and node equipment - Google Patents

Passive communication method, passive communication system and node equipment Download PDF

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Publication number
CN116546455A
CN116546455A CN202310584054.6A CN202310584054A CN116546455A CN 116546455 A CN116546455 A CN 116546455A CN 202310584054 A CN202310584054 A CN 202310584054A CN 116546455 A CN116546455 A CN 116546455A
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pin
reflection coefficient
radio frequency
antenna
frequency switch
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卢宁宁
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CETC 54 Research Institute
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CETC 54 Research Institute
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/02—Amplitude-modulated carrier systems, e.g. using on-off keying; Single sideband or vestigial sideband modulation
    • H04L27/04—Modulator circuits; Transmitter circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
    • H04L27/12—Modulator circuits; Transmitter circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
    • H04L27/20—Modulator circuits; Transmitter circuits

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

The invention discloses a passive communication method, a passive communication system and node equipment, and relates to the field of wireless communication. By utilizing the characteristics of the equivalent impedance of the two circuit structures such as short circuit and open circuit and the like, which are irrelevant to frequency, on the premise of not changing the software and hardware of the object end node and not increasing the complexity of the object end node, the message to be sent is modulated on the environmental electromagnetic waves with a plurality of frequencies in a parasitical mode, the multifrequency concurrent redundant parasitic transmission is realized, the power consumption of the object end node is ensured to be at an extremely low level, the error rate of the passive communication technology is reduced, the reliability is improved, and the anti-interference capability and the environmental adaptability of the passive communication technology are enhanced.

Description

Passive communication method, passive communication system and node equipment
Technical Field
The present invention relates to the field of wireless communications, and in particular, to a passive communication method, a passive communication system, and a node device.
Background
Along with the proposal of concepts such as smart city, smart agriculture, smart medical treatment, intelligent wearable, etc., the internet of things is increasingly applied in social life, and has become one of industries which develop at home and abroad. The object end node is an essential component of the Internet of things, belongs to a sensing layer of the Internet of things, is positioned at the tail end of the topological structure of the Internet of things, is generally embedded into a human body or an object for use, serves as a sensing organ and an executing organ of objective things, and is a key ring for realizing an intelligent network and constructing network intelligence. However, the problems of overlarge communication power consumption and the like are not solved properly, and the milliwatt-level communication power consumption can quickly consume the battery capacity, which severely restricts the application of the internet of things.
In order to reduce the communication power consumption on the object end node, researchers have designed passive communication technology based on electromagnetic wave back scattering, and the principle of the technology is shown in fig. 1 and 2. Wherein A is an antenna (antenna impedance Z) a ) B is an environmental radio frequency source, C is a radio frequency switch, Z L For the load, Z in the actual circuit L Can change along with the change of the frequency of the incident electromagnetic wave, and can lead Z to be made by design aiming at the specific frequency of the incident electromagnetic wave L ＝Z a 。
1) The object end node converts the collected data into a unipolar square wave signal by a baseband processing method such as channel coding, and then uses the square wave signal to control the state (on or off) of the radio frequency switch C so as to realize parasitic modulation of the message, in particular: (1) When it is desired to transmit bit 1 (as shown in FIG. 1), a high level appears at CTRL, causing switch K to 1 Closing, antenna A and load Z L On, ideally Z L ＝Z a The radio frequency circuit is matched with the antenna, so that the reflection coefficient is 0, the electromagnetic signals are all absorbed, and the power of the reflected signals is 0. (2) When it is desired to transmit bit 0 (as shown in FIG. 2), a low level appears at CTRL, causing switch K to 1 Opening, antenna A and load Z L And the antenna is not communicated, and at the moment, the load impedance is infinite and the reflection coefficient is 1. Ideally, the signal is totally reflected, with the reflected signal power being the greatest.
2) The receiving end can recover the bit data sent by the object end node by distinguishing the intensity (representing the high and low level changes) of the reflected signal, specifically: sampling and judging the received electromagnetic wave signal, (1) when the energy of the electromagnetic wave signal in one symbol period is greater than a threshold value, indicating that the data sent by an object terminal node is bit 0; (2) When the energy of the electromagnetic wave signal in one symbol period is smaller than the threshold value, the data sent by the object end node is indicated as bit 1.
As can be seen from fig. 1 and 2, there is only one active device in the transmitter, the rf switch. Taking the most common radio frequency switch ADG901 as an example, the power consumption is less than or equal to 2.75 microwatts and is far lower than the power consumption of the level of the Internet of things communication chips such as ZigBee, bluetooth, loRa and the like at the level of often milliwatts.
However, the passive communication techniques shown in fig. 1 and 2 essentially use the electromagnetic wave backscattering principle to realize OOK (On-Off Keying) modulation, so that the problem of excessive power consumption of wireless communication is solved, and meanwhile, the passive communication techniques can only be used for specific incident electromagnetic wave frequencies, so that the passive communication techniques have many defects, such as weak anti-interference capability, high error rate, poor reliability, poor environment adaptability and the like.
Disclosure of Invention
In order to solve the above problems, the embodiments of the present invention provide a multi-frequency concurrent passive communication technology, which utilizes the characteristics that the equivalent impedance of two circuit structures such as short circuit and open circuit is irrelevant to frequency, and on the premise of not changing the software and hardware of an object end node and not increasing the power consumption and complexity of the object end node, the data to be sent is parasitic modulated on the environmental electromagnetic waves with multiple frequencies, thereby implementing multi-frequency concurrent redundant parasitic transmission of the message, so as to improve the anti-interference capability of the passive communication technology, reduce the bit error rate and enhance the reliability of the passive communication technology.
Some embodiments of the present disclosure provide a passive communication method, including:
the node apparatus receives incident electromagnetic waves of a plurality of frequencies through an antenna, the node apparatus comprising: the antenna and the radio frequency switch are in short circuit between a first pin of the radio frequency switch and the ground, an open circuit is between a second pin of the radio frequency switch and the ground, a third pin of the radio frequency switch is connected with the antenna, a fourth pin of the radio frequency switch is connected with the control end, and the control end is used for inputting a control sequence generated by data to be transmitted;
the node equipment controls the communication state of each pin of the radio frequency switch by using a control sequence, and respectively controls the communication of a third pin and the first pin or the second pin by using first control data and second control data in the control sequence to respectively form a first reflection coefficient and a second reflection coefficient which are irrelevant to the frequency of receiving electromagnetic waves;
the node equipment reflects the incident electromagnetic waves with a plurality of frequencies through the antenna to form reflected electromagnetic waves with the same reflection coefficient, and the reflection coefficient during reflection is a first reflection coefficient or a second reflection coefficient.
In some embodiments, the first reflection coefficient Γ is in a state that the third pin is communicated with the first pin 0 ＝(Z 0 -Z a )/(Z 0 +Z a ) -1; or alternatively, the process may be performed,
in the state that the third pin is communicated with the second pin, the second reflection coefficient Γ ∞ ＝(Z ∞ -Z a )/(Z ∞ +Z a )＝+1；
Wherein Z is a Representing the antenna impedance, Z 0 Represents a first load impedance between the first pin and ground, the equivalent impedance of the first load impedance is 0, Z ∞ Representing a second load impedance between the second pin and ground, the equivalent impedance of the second load impedance being infinity.
In some embodiments, the data to be transmitted is generated into a control sequence by means of amplitude shift keying ASK, frequency shift keying FSK, or phase shift keying PSK.
In some embodiments, further comprising:
the receiver converts the received reflected electromagnetic wave into a digital sampling sequence;
the receiver performs band-pass filtering operation on the digital sampling sequence by using a plurality of band-pass filters to obtain a plurality of paths of signals, wherein different band-pass filters have different center frequencies;
the receiver performs down-conversion operation and signal processing operation on each signal by using a plurality of mixers;
the receiver determines the final received bit data based on the processed multipath signals.
Some embodiments of the present disclosure provide a node apparatus for passive communication, comprising:
the antenna and the radio frequency switch are in short circuit between a first pin of the radio frequency switch and the ground, an open circuit is between a second pin of the radio frequency switch and the ground, a third pin of the radio frequency switch is connected with the antenna, a fourth pin of the radio frequency switch is connected with the control end, and the control end is used for inputting a control sequence generated by data to be transmitted;
based on the control of the first control data and the second control data in the control sequence, the third pin is respectively communicated with the first pin or the second pin to respectively form a first reflection coefficient and a second reflection coefficient which are irrelevant to the frequency of the received electromagnetic wave;
the antenna is used for receiving the incident electromagnetic waves with a plurality of frequencies, and reflecting the incident electromagnetic waves with a plurality of frequencies with the same reflection coefficient to form reflected electromagnetic waves, wherein the reflection coefficient during reflection is a first reflection coefficient or a second reflection coefficient.
In some embodiments, the first reflection coefficient Γ is in a state that the third pin is communicated with the first pin 0 ＝(Z 0 -Z a )/(Z 0 +Z a ) -1; or alternatively, the process may be performed,
in the state that the third pin is communicated with the second pin, the second reflection coefficient Γ ∞ ＝(Z ∞ -Z a )/(Z ∞ +Z a )＝+1；
Wherein Z is a Representing the antenna impedance, Z 0 Represents a first load impedance between the first pin and ground, the equivalent impedance of the first load impedance is 0, Z ∞ Representing a second load impedance between the second pin and ground, the equivalent impedance of the second load impedance being infinity.
In some embodiments, further comprising: the sequence generation module is configured to generate a control sequence for the data to be transmitted by adopting an amplitude shift keying ASK, a frequency shift keying FSK or a phase shift keying PSK mode.
Some embodiments of the present disclosure provide a passive communication system comprising: a node device.
In some embodiments, the system further comprises: a receiver, comprising:
the analog-to-digital conversion module is used for converting the received reflected electromagnetic wave into a digital sampling sequence;
the plurality of band-pass filters are used for respectively performing band-pass filtering operation on the digital sampling sequences to obtain multiple paths of signals, and different band-pass filters have different center frequencies;
a plurality of mixers for performing down-conversion operation on each signal, respectively;
the signal processing modules are used for respectively executing signal processing operation on each path of signal;
and the data synthesis module is used for determining finally received bit data based on the processed multipath signals.
In some embodiments, the node device is an internet of things end node device.
In some embodiments, the data synthesis module is configured to select one of the processed multipath signals as the finally received bit data.
Drawings
Fig. 1 shows a modulation method (CTRL high level) in passive communication.
Fig. 2 shows a modulation method (CTRL low level) in passive communication.
Fig. 3 shows a block diagram of a passive communication system.
Fig. 4 shows a schematic diagram of the circuit structure of the transmitter of the object end node and the multi-frequency concurrent parasitic modulation method.
Fig. 5 shows a schematic diagram of a receiver and a method of receiving a multi-frequency concurrent parasitic transmission.
Fig. 6 shows ASK mapping pattern of unipolar square wave.
Fig. 7 shows the FSK mapping pattern of a unipolar square wave.
Fig. 8 shows the PSK mapping pattern for a unipolar square wave.
Detailed Description
1) Passive communication systems, i.e. multifrequency concurrent parasitic transmission systems
As shown in fig. 3, the whole passive communication system comprises a radio frequency source F 1 ，F 2 ，…，F n Node equipment (such as an object end node or an end node of the internet of things) N and a receiver R. Their functions are:
(1) Radio frequencySource F 1 ，F 2 ，…，F n Respectively send out electromagnetic signals c 1 (t)，c 2 (t)，…，c n (t). Wherein c i (t),i∈[1,n]The electromagnetic signal can be any frequency band and any waveform. In practice, the RF source F 1 ，F 2 ，…，F n The system can be a radiation source inherent in objective environments such as an FM broadcasting tower, a television broadcasting tower, a cellular network base station, a WiFi router and the like, or a radiation source specially arranged for realizing low-power consumption passive communication of an object terminal node.
(2) A node device (e.g., an object node) N is the sender of the message. Unlike conventional transmitters, the object node N does not generate a carrier wave, and when a message needs to be transmitted, it simply uses the principle of electromagnetic wave backscattering to transmit a binary bit sequence to be transmitted, while parasitically modulating the binary bit sequence at the radio frequency source F 1 ，F 2 ，…，F n Electromagnetic waves of different frequencies radiated outwards.
As can be seen from fig. 4, since the object node transmitter does not require large power consumption devices such as oscillators, mixers, power amplifiers, etc., the node power consumption and complexity thereof are very low.
(3) The receiver R is the receiver of the message and is mainly responsible for recovering the binary bit sequence transmitted by the object end node N from the received electromagnetic signal (comprising a plurality of different frequency components).
2) Circuit structure of transmitter of object terminal node
The circuit structure of the transmitter of the object end node is shown in fig. 4, and mainly comprises an antenna and a radio frequency switch K. The first pin of the radio frequency switch is in short circuit with the ground, the second pin of the radio frequency switch is in open circuit with the ground, the third pin of the radio frequency switch is connected with the antenna, the fourth pin of the radio frequency switch is connected with the control end, and the control end is used for inputting a control sequence generated by data to be transmitted. A first load impedance between the first pin and ground, i.e. load impedance Z 0 A second load impedance between the second pin and ground, i.e. load impedance Z ∞ 。
(1) Load impedance Z 0
Switch K at Z 0 Pin PIN on one side 0 And the direct grounding is adopted to form a short circuit.
No matter the frequency of the radio frequency signal c (t), only the PIN PIN is ensured 0 Ground-to-ground wiring L 0 Is much smaller than the signal wavelength, then Z 0 Is always approximately equal to 0 omega.
(2) Load impedance Z ∞
Switch K at Z ∞ Pin PIN on one side 1 And the floating is suspended, and an open circuit is formed between the floating and the ground.
No matter the frequency of the radio frequency signal c (t), only the PIN PIN is ensured 1 The length of the exposed part is far smaller than the wavelength of the signal, then Z ∞ Is always equivalent to approximately equal to ++ infinity omega.
3) Generation of modulated signals
The object node converts the data to be transmitted into a unipolar square wave m (t, and uses m (t to control the on/off state (on or off) of the rf switch K), as shown in fig. 4.
When the RF switch K connects the antenna to the load impedance Z 0 When in communication, the first reflection coefficient Γ of the radio frequency path at the object end node 0 The method comprises the following steps:
Γ 0 ＝(Z 0 -Z a )/(Z 0 +Z a )＝-1 (1)
wherein Z is a Representing the antenna impedance, Z 0 Representing a first load impedance between the first pin and ground, the equivalent impedance of the first load impedance being approximately equal to 0Ω.
When the RF switch K connects the antenna to the load impedance Z ∞ When in communication, the second reflection coefficient Γ of the radio frequency path at the object end node ∞ The method comprises the following steps:
Γ ∞ ＝(Z ∞ -Z a )/(Z ∞ +Z a )＝+1 (2)
wherein Z is a Representing the antenna impedance, Z ∞ Representing a second load impedance between the second pin and ground, the equivalent impedance of the second load impedance being approximately equal to infinity.
Then, by the circuit shown in fig. 4, the reflection coefficient obtained according to the value of m (t) is:
wherein Z represents the load impedance, when the radio frequency switch K communicates the antenna with the load impedance Z 0 When z=z 0 The method comprises the steps of carrying out a first treatment on the surface of the When the radio frequency switch K is communicated with the antenna and the load impedance Z ∞ When z=z ∞ 。
4) Multifrequency concurrent parasitic transmission
When the incident electromagnetic wave is c (t), the electromagnetic signal b (t) reflected by the object end node is:
because of Z 0 、Z ∞ The value of (c) is independent of the frequency of the incident electromagnetic wave c (t), so that as shown in FIG. 3, when the electromagnetic wave c is of a plurality of frequencies 1 (t)、c 2 (t)、…、c n (t) (the frequencies are denoted as f respectively 1 、f 2 、…、f n ) When reaching the object end node at the same time, the object end node can reflect the object end node with the same reflection coefficient, and at this time, the electromagnetic signal b (t) reflected by the object end node is shown as formula (5):
b(t)＝Γ(t)c 1 (t)+Γ(t)c 2 (t)+…+Γ(t)c n (t) (5)
this corresponds to modulating the signal Γ (t) parasitically at f 1 ～f n And on a plurality of frequencies.
That is, an embodiment of the present disclosure proposes a passive communication method, including:
the node apparatus receives incident electromagnetic waves of a plurality of frequencies through an antenna, the node apparatus comprising: the antenna and the radio frequency switch are in short circuit between a first pin of the radio frequency switch and the ground, an open circuit is between a second pin of the radio frequency switch and the ground, a third pin of the radio frequency switch is connected with the antenna, a fourth pin of the radio frequency switch is connected with the control end, and the control end is used for inputting a control sequence generated by data to be transmitted;
the node equipment controls the communication state of each pin of the radio frequency switch by using a control sequence, and respectively controls the communication of a third pin and the first pin or the second pin by using first control data and second control data in the control sequence to respectively form a first reflection coefficient and a second reflection coefficient which are irrelevant to the frequency of receiving electromagnetic waves;
the node equipment reflects the incident electromagnetic waves with a plurality of frequencies through the antenna to form reflected electromagnetic waves with the same reflection coefficient, and the reflection coefficient during reflection is a first reflection coefficient or a second reflection coefficient.
5) Demodulation method
The receiver of the receiver is shown in fig. 5, and mainly comprises an analog-to-digital conversion module, a band-pass filter, a mixer, a signal processing module and a data synthesis module.
(1) Analog-to-digital conversion module
The electromagnetic signal (i.e., the reflected electromagnetic wave) received by the antenna is converted into a sequence of digital samples.
(2) Band-pass filter (BPF)
In a receiver, a plurality of bandpass filters are included, each of which is denoted by f 1 、f 2 、…、f n For the center frequency, different band-pass filters have different center frequencies, the analog-to-digital conversion module converts the center frequency to obtain a digital sampling sequence, and the band-pass filter operation is performed to obtain L 1 、L 2 、…、L n And the signals of all paths.
(3) Mixer with a high-speed mixer
In a receiver, comprising a plurality of mixers, L 1 、L 2 、…、L n Each of the signals corresponds to a mixer for performing a down-conversion operation on each of the signals.
(4) Signal processing module
In the receiver, L 1 、L 2 、…、L n Each signal corresponds to a signal processing module, and is used for performing demodulation, decoding, verification and other operations, and adopting adaptive operations with modulation, coding and the like of a transmitter.
(5) Data synthesis module
Mainly for from L 1 、L 2 、…、L n And selecting one bit data from the bit data obtained in each path as the finally received bit data. For example, the one with the best signal strength is selected as the final received bit data.
The methods shown in fig. 3, fig. 4 and fig. 5 not only can ensure that the power consumption of the object end node is at an extremely low level, but also can improve the environment adaptability of the backscatter communication, and can also enhance the reliability of the backscatter communication technology through redundant transmission.
In addition, the multi-frequency concurrent transmission technology provided by the invention is very important for anti-interference, and when a certain frequency point is interfered, the perceived data can be parasitically transmitted through other frequency points without changing the software and hardware of the object end node or increasing the complexity of the object end node.
Node device, further comprising: the sequence generation module is configured to generate a control sequence for the data to be transmitted by adopting an amplitude shift keying ASK, a frequency shift keying FSK or a phase shift keying PSK mode.
First embodiment
The object node may convert the data to be transmitted into a unipolar square wave m (t) in an ASK (amplitude shift keying) manner, as shown in fig. 6. The object node may map bit 1 to a high level with duration T and bit 0 to a low level with duration T; the object end node may also map bit 1 to a low level of duration T and bit 0 to a high level of duration T.
Second embodiment
The object node may convert the data to be transmitted into a unipolar square wave m (t) in an FSK (frequency shift keying) manner, as shown in fig. 7. With a bit duration of T, the object node can map bit 1 to a duration of T, a frequency of f H Is a square wave of (2); mapping bit 0 to a duration T, frequency f L Is a square wave of (c).
Third embodiment
The object node may use PSK (phase shift keying) to convert the data to be transmitted into a unipolar square wave m (t), as shown in fig. 8. Recording the bit duration as T, the object end node can map the bit 1 into square waves with the duration as T, the frequency as f and the phase as 0; bit 0 is mapped to a square wave of duration T, frequency f, phase pi.
It will be appreciated by those skilled in the art that embodiments of the present disclosure may be provided as a method, system, or computer program product. Accordingly, the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present disclosure may take the form of a computer program product embodied on one or more non-transitory computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer program code embodied therein.
The foregoing description of the preferred embodiments of the present disclosure is not intended to limit the disclosure, but rather to enable any modification, equivalent replacement, improvement or the like, which fall within the spirit and principles of the present disclosure.

Claims (10)

1. A passive communication method, comprising:
the node apparatus receives incident electromagnetic waves of a plurality of frequencies through an antenna, the node apparatus comprising: the antenna and the radio frequency switch are in short circuit between a first pin of the radio frequency switch and the ground, an open circuit is between a second pin of the radio frequency switch and the ground, a third pin of the radio frequency switch is connected with the antenna, a fourth pin of the radio frequency switch is connected with the control end, and the control end is used for inputting a control sequence generated by data to be transmitted;
the node equipment controls the communication state of each pin of the radio frequency switch by using a control sequence, and respectively controls the communication of a third pin and the first pin or the second pin by using first control data and second control data in the control sequence to respectively form a first reflection coefficient and a second reflection coefficient which are irrelevant to the frequency of receiving electromagnetic waves;
the node equipment reflects the incident electromagnetic waves with a plurality of frequencies through the antenna to form reflected electromagnetic waves with the same reflection coefficient, and the reflection coefficient during reflection is a first reflection coefficient or a second reflection coefficient.
2. The method according to claim 1, wherein:
in the state that the third pin is communicated with the first pin, the first reflection coefficient Γ 0 ＝(Z 0 -Z a )/(Z 0 +Z a ) -1; or alternatively, the process may be performed,
in the state that the third pin is communicated with the second pin, the second reflection coefficient Γ ∞ ＝(Z ∞ -Z a )/(Z ∞ +Z a )＝+1；
Wherein Z is a Representing the antenna impedance, Z 0 Represents a first load impedance between the first pin and ground, the equivalent impedance of the first load impedance is 0, Z ∞ Representing a second load impedance between the second pin and ground, the equivalent impedance of the second load impedance being infinity.
3. The method according to claim 1, wherein:
and generating a control sequence for the data to be transmitted by adopting an amplitude shift keying ASK, a frequency shift keying FSK or a phase shift keying PSK mode.
4. A method according to any one of claims 1-3, further comprising:
the receiver converts the received reflected electromagnetic wave into a digital sampling sequence;
the receiver performs band-pass filtering operation on the digital sampling sequence by using a plurality of band-pass filters to obtain a plurality of paths of signals, wherein different band-pass filters have different center frequencies;
the receiver performs down-conversion operation and signal processing operation on each signal by using a plurality of mixers;
the receiver determines the final received bit data based on the processed multipath signals.
5. A node device for passive communication, comprising:
the antenna and the radio frequency switch are in short circuit between a first pin of the radio frequency switch and the ground, an open circuit is between a second pin of the radio frequency switch and the ground, a third pin of the radio frequency switch is connected with the antenna, a fourth pin of the radio frequency switch is connected with the control end, and the control end is used for inputting a control sequence generated by data to be transmitted;
based on the control of the first control data and the second control data in the control sequence, the third pin is respectively communicated with the first pin or the second pin to respectively form a first reflection coefficient and a second reflection coefficient which are irrelevant to the frequency of the received electromagnetic wave;
the antenna is used for receiving the incident electromagnetic waves with a plurality of frequencies, and reflecting the incident electromagnetic waves with a plurality of frequencies with the same reflection coefficient to form reflected electromagnetic waves, wherein the reflection coefficient during reflection is a first reflection coefficient or a second reflection coefficient.
6. The node device of claim 5, wherein:
in the state that the third pin is communicated with the first pin, the first reflection coefficient Γ 0 ＝(Z 0 -Z a )/(Z 0 +Z a ) -1; or alternatively, the process may be performed,
in the state that the third pin is communicated with the second pin, the second reflection coefficient Γ ∞ ＝(Z ∞ -Z a )/(Z ∞ +Z a )＝+1；
Wherein Z is a Representing the antenna impedance, Z 0 Represents a first load impedance between the first pin and ground, the equivalent impedance of the first load impedance is 0, Z ∞ Representing a second load impedance between the second pin and ground, the equivalent impedance of the second load impedance being infinity.
7. The node device of claim 5, further comprising:
the sequence generation module is configured to generate a control sequence for the data to be transmitted by adopting an amplitude shift keying ASK, a frequency shift keying FSK or a phase shift keying PSK mode.
8. A passive communication system, comprising: the node device of any of claims 5-7.
9. The system of claim 8, further comprising:
a receiver, comprising:
the analog-to-digital conversion module is used for converting the received reflected electromagnetic wave into a digital sampling sequence;
the plurality of band-pass filters are used for respectively performing band-pass filtering operation on the digital sampling sequences to obtain multiple paths of signals, and different band-pass filters have different center frequencies;
a plurality of mixers for performing down-conversion operation on each signal, respectively;
the signal processing modules are used for respectively executing signal processing operation on each path of signal;
and the data synthesis module is used for determining finally received bit data based on the processed multipath signals.
10. The system of claim 9, wherein:
the node equipment is end node equipment of the Internet of things; or alternatively, the process may be performed,
the data synthesis module is used for selecting one from the processed multipath signals to serve as the finally received bit data.
CN202310584054.6A 2023-05-23 2023-05-23 Passive communication method, passive communication system and node equipment Pending CN116546455A (en)

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