CN113542182B - A device for passively increasing the transmission distance of backscattered 2ASK modulation - Google Patents

Abstract

The invention provides a passive device for improving the transmission distance of backscattering 2ASK modulation, belonging to the technical field of wireless communication, comprising a control module, a directional sending and receiving antenna, a directional transmitting antenna and a switch modulation module. The invention adopts the dual antenna and dual switch 2ASK modulation mode suitable for the backscatter communication system, which not only effectively realizes the 2ASK modulation of the Backscatter wireless communication, but also improves the transmission distance of the Backscatter 2ASK modulation. The invention overcomes the shortcoming of the traditional Backscatter2ASK modulation communication system in terms of short transmission distance, and ensures a good modulation effect.

Description

A device for passively increasing the transmission distance of backscattered 2ASK modulation

technical field

The invention belongs to the technical field of wireless communication, and in particular relates to a passive device for improving the transmission distance of backscattered 2ASK modulation.

Background technique

Modulation is an indispensable and important part of wireless communication systems. Compared with traditional modulation techniques in wireless communication systems, backscatter modulation has been widely used due to its simple modulation equipment and low power consumption. It is in the application of RFID technology. The wireless communication system based on backscatter technology has also received extensive attention. The biggest advantage of this communication system is that it can fully realize passive tags, which is one of the important technologies for the future smart Internet of Things.

Backscatter modulation is achieved by changing the impedance of the antenna terminal. When the antenna is terminated with different impedances, the signal will be reflected, and the reflected signal strength and phase will change due to different impedances. Signal modulation can be achieved by using this change. The modulated reflected signal will be transmitted on the same antenna.

When the backscatter technology uses the antenna to connect different loads, different reflection coefficients will be obtained to realize the modulation of the signal. Compared with the traditional digital modulation, the complexity of the realization is greatly reduced, the equipment requirements are relatively simple, and the power consumption is also greatly reduced. It has great advantages in the application of the Internet of Things. The current backscatter communication system also has some problems. One of the important problems is that the transmission distance is too short (the transmission distance is usually less than 100m), so long-distance transmission cannot be realized, which greatly limits the application of this technology. Improving the transmission distance of Backscatter technology is also an important topic in current backscatter research.

SUMMARY OF THE INVENTION

In view of the above deficiencies in the prior art, the present invention provides a passive device for increasing the modulation transmission distance, which overcomes the shortcoming of the traditional Backscatter 2ASK modulation signal in terms of short transmission distance.

In order to achieve the above purpose, the technical scheme adopted in the present invention is:

This solution provides a passive device for improving the transmission distance of backscattered 2ASK modulation, including a control module, a directional transceiver antenna, a directional transmit antenna, and a switch modulation module; the directional transceiver antenna, the directional transmit antenna, and the switch modulation module connect;

The control module is used to provide a control signal for the switch modulation module, and the control signal is the baseband signal of the user;

The switch modulation module is used to receive the control signal provided by the control module and modulate the carrier signal;

The directional transceiver antenna is used to receive the carrier signal and transmit the 2ASK modulated signal to the incoming wave direction of the carrier;

The directional transmit antenna is used to transmit the 2ASK modulated signal to the direction in which it is aimed.

Further, the isolation between the directional transmitting and receiving antenna and the directional transmitting antenna exceeds 30dB.

Still further, the control module is a digital circuit module, and the control signal waveform provided by the control module is consistent with the modulation signal waveform required by the switch modulation module.

Still further, the switch modulation module includes a first SPDT switch, a second SPDT switch, and a matching load; both the first SPDT switch and the second SPDT switch include a moving terminal, a second SPDT switch, and a second SPDT switch. A fixed port and a second fixed port; the moving end RFc2 of the second SPDT switch is connected to the directional transmitting antenna; the moving end RFc1 of the first SPDT switch is connected to the directional transmitting and receiving antenna ;

The first stationary port RFs11 of the first SPDT switch is turned on, the second stationary port RFs12 of the first SPDT switch is turned off, and the first stationary port RFs12 of the second SPDT switch is not activated. The port RFs21 is turned on, and the second stationary port RFs22 of the second SPDT switch is turned off; or

The second stationary port RFs12 of the first SPDT switch is turned on, the first stationary port RFs11 of the first SPDT switch is turned off, and the second stationary port RFs11 of the second SPDT switch is simultaneously disconnected. The port RFs22 is turned on, and the first stationary port RFs21 of the second SPDT switch is turned off.

Still further, the second non-moving port RFs12 of the first SPDT switch can be connected to different terminals (such as ground) that can form reflections.

Still further, the second stationary port RFs22 of the second SPDT switch is connected to a terminal without signal output (eg, a matched load).

Still further, the first SPDT switch and the second SPDT switch are controlled by the same set of control signals.

Still further, the directional transmitting and receiving antennas and the directional transmitting antennas are both directional antennas and have the same or different antenna gains.

Beneficial effects of the present invention:

(1) The present invention adopts the dual-antenna and dual-switch 2ASK modulation mode suitable for the Backscatter communication system, overcomes the shortcoming of the traditional Backscatter 2ASK modulation system in terms of short transmission distance, and not only effectively realizes the 2ASK modulation of the Backscatter wireless communication , and effectively improve the transmission distance of Backscatter 2ASK modulation system.

(2) Compared with the traditional Backscatter 2ASK modulation system, the present invention adopts the mode of joint operation of dual directional antennas and dual switches, which can improve the transmission distance, and can transmit 2ASK modulated signals in the selected direction, which can realize signal radiation. Flexible control of direction.

Description of drawings

FIG. 1 is a schematic diagram of the composition of the Backscatter 2ASK modulation module of the present invention.

FIG. 2 is a test circuit of the Backscatter 2ASK modulation module in this embodiment.

Detailed ways

The specific embodiments of the present invention are described below to facilitate those skilled in the art to understand the present invention, but it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes Such changes are obvious within the spirit and scope of the present invention as defined and determined by the appended claims, and all inventions and creations utilizing the inventive concept are within the scope of protection.

Example

As shown in FIG. 1 , the present invention provides a device for passively improving the transmission distance of 2ASK modulation, including a control module, a directional transceiver antenna, a directional transmit antenna, and a switch modulation module; the directional transceiver antenna and the directional transmit antenna are related to the The switch modulation module is connected; the control module is used to provide a control signal for the switch modulation module, and the control signal is the baseband signal of the user; the switch modulation module is used to receive the control signal provided by the control module, and modulate carrier signal; the directional transmitting and receiving antenna is used to receive the carrier signal and transmit the 2ASK modulated signal to the incoming wave direction of the carrier wave; the directional transmitting antenna is used to transmit the 2ASK modulated signal to the direction it is aimed at. The isolation between the directional transmitting and receiving antenna and the directional transmitting antenna exceeds 30dB. The control signal waveform provided by the control module is consistent with the modulation signal waveform used by the switch modulation module. The switch modulation module includes a first SPDT switch, a second SPDT switch and a matching load; both the first SPDT switch and the second SPDT switch include a moving end, a first non-moving end port and a second stationary port; the moving end RFc2 of the second SPDT switch is connected to the directional transmitting antenna; the moving end RFc1 of the first SPDT switch is connected to the directional transmitting and receiving antenna; the The first stationary port RFs11 of the first SPDT switch is turned on, the second stationary port RFs12 of the first SPDT switch is turned off, and at the same time the first stationary port RFs21 of the second SPDT switch is turned off is turned on, the second stationary port RFs22 of the second SPDT switch is turned off; or the second stationary port RFs12 of the first SPDT switch is turned on, the first SPDT switch A stationary port RFs11 is turned off, while the second stationary port RFs22 of the second SPDT switch is turned on, and the first stationary port RFs21 of the second SPDT switch is turned off. The second stationary port RFs12 of the first SPDT switch can be connected to other terminals capable of forming reflections. The second stationary port RFs22 of the second SPDT switch can be connected to other terminals without signal output. The first SPDT switch and the second SPDT switch are controlled by the same set of control signals. The directional transmitting and receiving antennas and the directional transmitting antennas are both directional antennas, which have the same or different antenna gains.

In this embodiment, the present invention includes: 2 directional antennas (directional transmitting and receiving antennas, directional transmitting antennas), one switching modulation module and one control module. The switch modulation module includes a first SPDT switch and a second SPDT switch, and the moving ends of the two switches are respectively connected to the directional transceiver antenna (for receiving and transmitting) and the directional transmitting antenna (for transmitting); the first SPDT The throw switch can be grounded (it may also be other loads that form a large reflection) or the second SPDT switch can be connected, and the second SPDT switch can be connected to the first SPDT switch or a matching load; the control module It is a digital circuit module that sends control signals to the switch modulation module. Under the action of the control signal, the system modulates the carrier signal received by the directional transceiver antenna, and the modulated signal is transmitted through the directional transceiver antenna and the directional transmit antenna, and received by different receivers in the directions aligned with the two antennas.

In this embodiment, the two directional antennas are one receiving and transmitting directional antenna and one directional transmitting antenna.

In this embodiment, the switch modulation module is composed of two SPDT switches (a first SPDT switch and a second SPDT switch) and a matching load. Each SPDT switch consists of three signal ports, which are one moving port (represented by the RFc port) and two non-moving ports (represented by the RFs port). The directional transceiver antenna is connected to the RFc1 port of the first SPDT switch. Among the two RFs ports of the first SPDT switch, one port RFs12 is connected to the ground to realize a short circuit, and the other port RFs11 is connected to the The RFs21 port of the second SPDT switch, the other fixed port RFs22 of the second SPDT switch is connected to the matching load, the RFc2 port of the second SPDT switch is connected to the directional transmitting antenna, and the control module is the first The SPDT switch and the second SPDT switch provide a control signal, which is the baseband signal of the user.

In this embodiment, the control module is a digital circuit module that sends a control signal to the switch, and the waveform of the input control signal is consistent with the waveform of the modulation signal.

In this embodiment, in addition to being connected to the ground, the RFs12 port of the first SPDT switch may also be connected to other terminals capable of forming a larger reflection.

In this embodiment, in addition to the matching load, the RFs22 port of the second SPDT switch can also be connected to other terminals without signal output.

In this embodiment, the Backscatter 2ASK modulated directional transceiver antenna is used to receive the carrier signal of the Backscatter wireless communication system, and transmit the 2ASK modulated signal in the direction of the incoming wave of the carrier.

In this embodiment, the Backscatter 2ASK modulated directional transmit antenna is used to transmit the 2ASK modulated signal in the direction in which it is aimed, and the isolation between the two antennas in this direction exceeds 30dB.

In this embodiment, as shown in FIG. 1 , the directional antenna 1 is a directional transmitting and receiving antenna, and the directional antenna 2 is a directional transmitting antenna. After the directional transceiver antenna receives the carrier signal (single tone or bandwidth signal), the first SPDT switch and the second SPDT switch act simultaneously under the action of the same control signal c(t) of the control module. A SPDT switch is connected to the RFs21 port of the second SPDT switch through the RFs12 port to ground (short-circuit state) or through the RFs11 port. Correspondingly, the second SPDT switch is connected to the matching load through the RFs22 port (the load impedance is usually 50 ohms) or connect the RFs21 port to the RFs11 port of the first SPDT switch.

In this embodiment, under the same c(t) control, when the first SPDT switch is connected to the ground, the second SPDT switch is connected to the matching load. At this time, the carrier signal (take a single tone as an example) received by the directional antenna 1 (directional transceiver antenna) A ₀ cos(2πf _c t+θ) will be reflected and still transmitted through the directional transceiver antenna (directional antenna 1). A 2ASK modulated high-level signal is formed in the direction of the directional transceiver antenna (directional antenna 1). At this time, because the matching load is turned on, the directional transmitting antenna (directional antenna 2) has no signal transmission, which means that a low-level signal of 2ASK modulation is formed in the direction of the directional transmitting antenna (directional antenna 2).

In this embodiment, under the same control of c(t), when the first SPDT switch is connected to RFs11, the second SPDT switch is connected to the RFs21 port, that is, the first SPDT switch and the second SPDT switch are connected to the RFs21 port. Throw switch 2 switches are turned on. At this time, the carrier signal A ₀ cos(2πf _c t+θ) received by the directional antenna 1 (directional transmitting and receiving antenna) will be transmitted to the second SPDT switch and transmitted by the directional transmitting antenna (directional antenna 2). A high-level signal of 2ASK modulation is formed on the directional transmitting antenna (directional antenna 2), while no signal is transmitted on the directional antenna 1 (directional transmitting and receiving antenna), which means that a low-level 2ASK modulation is formed on the directional antenna 1 (directional transmitting and receiving antenna). Signal. To sum up, the modulated signals transmitted by the directional antenna 1 and the directional antenna 2 have opposite phases, and can be received by different receivers in the directions aligned with the two antennas.

In this embodiment, when the waveform of the control signal is consistent with the waveform of the modulation signal, the switch state is associated with the modulation signal c(t). If the control signal:

The transmitted signal s _t1 (t) of directional antenna 1 (directional transmitting and receiving antenna) and the transmitted signal s _t2 (t) of directional antenna 2 (directional transmitting antenna) can be expressed as:

Among them, A ₁ and A ₂ are the signal amplitudes, which are related to the control signal, the actual reflection coefficient, and the actual circuit loss, and ξ ₁ and ξ ₂ are the phase changes caused by reflection and circuit transmission. It can be seen from the expression that the modulated signal envelopes emitted by directional antenna 1 and directional antenna 2 are out of phase.

In this embodiment, from the perspective of signal power, the link budget of the system can be simply analyzed. Let Z _a =R _a +jX _a be the complex impedance of the antenna. For two different loads Z _c1 and Z _c2 , consider the differential backscattered power:

Among them, _Ra is the real part of the antenna impedance, and G is the gain of the directional antennas 1 and 2 (it is assumed here that the directional antenna 1 and the directional antenna 2 have equal gains). where the current can be calculated from the following equation:

Γ ₁ and Γ ₂ are the reflection coefficients at the load end when Z _c1 and Z _c2 are connected, and V ₀ is the antenna voltage caused by the incident wave.

给出。In this embodiment, when the power density of the incident wave is S, V ₀ can be determined by

given.

In this embodiment, the differential radar cross section is:

Ideally |Γ ₁ -Γ ₂ | ² =1, because the corresponding Γ ₁ and Γ ₂ are -1 and 0 when the antenna terminal is connected to the ground and the matched load is connected.

To sum up, it can be obtained that the signal power received by the receiver in the single-station mode (the receiver at the receiver where the carrier source is located receives the modulated signal transmitted by the directional antenna 1) is:

Among them, P _t represents the carrier power, G _t0 represents the transmit antenna gain of the carrier source, λ represents the operating wavelength of the system, and d ₀ represents the distance from the carrier source to the system.

In this embodiment, if the dual-station mode is adopted (the modulated signal transmitted by the directional antenna 2 is received by a receiver different from the receiver where the carrier source is located), the power received by the receiver is:

In the formula, G _r represents the gain of the receiver antenna, and d represents the distance from the system to the receiver.

In this embodiment, combined with the source transmit power:

P _s =P _t G _t0

Get the link loss for single station mode

and link loss in dual-station mode

倍(其中G₀为传统的RF tag采用的全向天线的增益，显然G>G₀)，达到了增加传输距离的目的。此外，由于本发明所采用的结构，散射信号(与散射回源端的信号的包络特性相反)还能通过定向天线2辐射到另一个需求方向，实现了信号辐射方向的灵活控制。Compared with the traditional Backscatter 2ASK communication mode using the omnidirectional antenna, the received power is the original when the present invention is adopted.

times (where G ₀ is the gain of the omnidirectional antenna used by the traditional RF tag, obviously G>G ₀ ), which achieves the purpose of increasing the transmission distance. In addition, due to the structure adopted in the present invention, the scattered signal (contrary to the envelope characteristic of the signal scattered back to the source end) can also be radiated to another desired direction through the directional antenna 2, realizing flexible control of the signal radiation direction.

In this embodiment, as shown in Figure 2, which is a schematic diagram of the test (test) circuit, the signal source generates a carrier signal (single tone signal) and is transmitted by the antenna, the directional antenna 1 receives the carrier signal, and the modulation module completes 2ASK modulation After that, it is transmitted by directional antenna 1 and directional antenna 2, and is received and analyzed by an oscilloscope (including the receiving front end) in the direction where the directional antenna 1 and directional antenna 2 are aligned. The experimental results show that the Backscatter 2ASK modulation device described in the present invention can effectively complete the Backscatter 2ASK signal modulation. The signal can travel farther; the quality of the signal received at the same distance is better.

Claims (3)

1. a device that passively improves backscattering 2ASK modulation transmission distance, is characterized in that, comprises control module, directional sending and receiving antenna, directional transmitting antenna and switch modulation module; Described directional sending and receiving antenna and directional sending antenna and described Switch modulation module connection; The control module is configured to provide a control signal for the switch modulation module, and the control signal is a user's baseband signal; The switch modulation module is used to receive the control signal provided by the control module and modulate the carrier signal; The directional transceiver antenna is used to receive the carrier signal and transmit the 2ASK modulated signal to the incoming wave direction of the carrier; The directional transmitting antenna is used to transmit the 2ASK modulated signal to the direction in which it is aimed; The isolation between the directional transmitting and receiving antenna and the directional transmitting antenna exceeds 30dB; The switch modulation module includes a first SPDT switch, a second SPDT switch and a matching load; both the first SPDT switch and the second SPDT switch include a moving terminal and a first non-moving port and the second fixed port; the moving end RFc2 of the second SPDT switch is connected to the directional transmitting antenna; the moving end RFc1 of the first SPDT switch is connected to the directional transmitting and receiving antenna; The first stationary port RFs11 of the first SPDT switch is turned on, the second stationary port RFs12 of the first SPDT switch is turned off, and the first stationary port RFs12 of the second SPDT switch is not activated. The port RFs21 is turned on, and the second stationary port RFs22 of the second SPDT switch is turned off; or The second stationary port RFs12 of the first SPDT switch is turned on, the first stationary port RFs11 of the first SPDT switch is turned off, and the second stationary port RFs11 of the second SPDT switch is simultaneously disconnected. The port RFs22 is turned on, and the first stationary port RFs21 of the second SPDT switch is turned off; The second stationary port RFs12 of the first SPDT switch is connected to different terminals capable of forming reflection; The second stationary port RFs22 of the second SPDT switch is connected to a terminal without signal output; The first SPDT switch and the second SPDT switch are controlled by the same set of control signals. 2. The device for passively improving the transmission distance of backscattering 2ASK modulation according to claim 1, wherein the control module is a digital circuit module, and the control signal waveform provided by the control module is different from the switching modulation module. The required modulation signal waveforms are the same. 3 . The device for passively increasing the transmission distance of backscattered 2ASK modulation according to claim 1 , wherein the directional transceiver antenna and the directional transmit antenna are both directional antennas with the same or different antenna gains. 4 .

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