A Bluetooth RF circuit based on dual antennas

Abstract

The present invention relates to a Bluetooth radio frequency circuit based on dual antennas, which belongs to the field of Bluetooth radio frequency technology and solves the problems of poor accuracy and high hardware cost of existing Bluetooth ranging methods. In the present invention, the Bluetooth radio frequency circuit includes: a BLE chip, a phase shift circuit, an antenna 1 and an antenna 2; wherein the radio frequency port 1 and the radio frequency port 2 of the BLE chip are connected to the two input ends of the phase shift circuit in a one-to-one correspondence, and the two output ends of the phase shift circuit are connected to the antenna 1 and the antenna 2 in a one-to-one correspondence; the antenna 1 and the antenna 2 are arranged relative to each other, and the combination provides an omnidirectional directional pattern; the radio frequency port 1 and the radio frequency port 2 of the BLE chip are differential outputs. The Bluetooth radio frequency circuit provided by the present invention has a simple structure and low cost, and can effectively improve the accuracy of Bluetooth ranging.

Description

Technical Field

[0001] The present invention relates to the technical field of Bluetooth radio frequency, and in particular to a Bluetooth radio frequency circuit based on dual antennas. Background Art

[0002] The car digital key is a technology based on BLE, UWB and NFC that can perform seamless operation of the vehicle. Among them, BLE (Bluetooth low energy) is responsible for communication and coarse positioning, and UWB is activated at a set distance for precise ranging.

[0003] The disadvantage of existing products is that BLE positioning uses a technical principle based on signal strength, and the signal strength is greatly affected by the surrounding environment of the car key itself. For example, at the same distance from the vehicle, the calculated distance will vary greatly due to different surrounding environments (the car key is placed in a bag or pocket).

[0004] At the same time, small-size antennas cannot achieve an ideal omnidirectional radiation pattern, which means that even when the car key itself is not affected by the surrounding environment, the signal strength received by the vehicle end will vary greatly due to its different postures.

[0005] In addition, the internal circuit structure of existing digital car keys is complex and the cost is high, which limits their wide application. Figure 1 As shown, the circuit uses a radio frequency switch to switch between different antennas, which increases the circuit cost and causes problems of unstable communication and untimely response due to the long switching time.

[0006] Therefore, how to design a car digital key or related Bluetooth radio frequency circuit with high ranging accuracy and low hardware cost is a technical problem that needs to be solved urgently. Summary of the invention

[0007] In view of the above analysis, an embodiment of the present invention aims to provide a Bluetooth radio frequency circuit based on dual antennas to solve the problems of poor accuracy and high hardware cost of existing Bluetooth ranging methods.

[0008] The present invention discloses a dual-antenna based Bluetooth radio frequency circuit, the Bluetooth radio frequency circuit comprising: a BLE chip, a phase shift circuit, an antenna 1 and an antenna 2; wherein:

[0009] The RF port 1 and RF port 2 of the BLE chip are connected to the two input ends of the phase shift circuit in a one-to-one correspondence, and the two output ends of the phase shift circuit are connected to the antenna 1 and the antenna 2 in a one-to-one correspondence;

[0010] Antenna 1 and antenna 2 are arranged relative to each other and combined to provide an omnidirectional pattern;

[0011] The RF port 1 and the RF port 2 of the BLE chip are differential outputs.

[0012] On the basis of the above scheme, the present invention also makes the following improvements:

[0013] Furthermore, the phase shift circuit includes: capacitors C1 and C2, and inductors L1 and L2; wherein,

[0014] One end of the capacitor C1 is connected to one end of the inductor L1, and the other end of the capacitor C1 is grounded; one end of the capacitor C1 serves as an input end of the phase shift circuit, and the other end of the inductor L1 serves as an output end matched with an input end of the phase shift circuit;

[0015] One end of the capacitor C2 is connected to one end of the inductor L2, and the other end of the inductor L2 is grounded; one end of the capacitor C2 serves as another input end of the phase shift circuit, and the other end of the inductor C2 serves as an output end matching the other input end of the phase shift circuit.

[0016] Furthermore, the Bluetooth radio frequency circuit also includes two filter capacitors;

[0017] The RF port 1 and the RF port 2 of the BLE chip are respectively connected in series with corresponding filter capacitors and then connected to the two input terminals of the phase shift circuit one by one.

[0018] Furthermore, the Bluetooth radio frequency circuit is located on a printed circuit board.

[0019] Furthermore, an antenna no-space zone 1 and an antenna no-space zone 2 are set on the printed circuit board; wherein the antenna no-space zone 1 carries the antenna 1, and the antenna no-space zone 2 carries the antenna 2.

[0020] Furthermore, the BLE chip and the phase shift circuit in the Bluetooth radio frequency circuit are located on the printed circuit board 1; the antenna 1 and the antenna 2 in the Bluetooth radio frequency circuit are located on the printed circuit board 2;

[0021] The two output ends of the phase shift circuit on the printed circuit board 1 are connected to the antenna 1 and the antenna 2 on the printed circuit board 2 in a one-to-one correspondence through a radio frequency connector.

[0022] Furthermore, an antenna no-space zone and an antenna no-space zone 2 are set on the printed circuit board 2 ; wherein the antenna no-space zone 1 carries the antenna 1 , and the antenna no-space zone 2 carries the antenna 2 .

[0023] Furthermore, the antenna no-go zone 1 and the antenna no-go zone 2 are arranged on two diagonals of the printed circuit board or the printed circuit board 2 .

[0024] Furthermore, antenna 1 and antenna 2 are arranged in parallel.

[0025] Furthermore, antenna 1 and antenna 2 are arranged vertically.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0027] The dual-antenna based Bluetooth radio frequency circuit provided by the present invention simplifies the circuit structure of the Bluetooth radio frequency circuit, and the implementation of the circuit does not require the help of a control circuit, thereby effectively reducing the high hardware cost. At the same time, the performance complementarity between multiple antennas is utilized to provide an omnidirectional directional pattern in combination to eliminate the irregular problem of the directional pattern, thereby effectively ensuring the accuracy of Bluetooth ranging.

[0028] At the same time, the present invention also provides a variety of design methods for realizing an omnidirectional antenna pattern by combining antenna 1 and antenna 2, providing technical guidance for relevant technical personnel to implement this solution.

[0029] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components;

[0031] Figure 1 A circuit diagram of a currently common multi-antenna design circuit provided by an embodiment of the present invention;

[0032] Figure 2 A circuit diagram of a dual-antenna Bluetooth radio frequency circuit provided by an embodiment of the present invention;

[0033] Figure 3 A circuit diagram of a phase shift circuit provided by an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of the structure of a layout mode 1 of antenna 1 and antenna 2 provided in an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of the structure of a layout mode 2 of antenna 1 and antenna 2 provided in an embodiment of the present invention;

[0036] Figure 6 A schematic diagram of a directional pattern coordinate system of a layout mode 1 of antennas 1 and 2 provided in an embodiment of the present invention;

[0037] Figure 7The directional diagram of the antenna 1 provided in the embodiment of the present invention on the XY plane;

[0038] Figure 8 The directional diagram of the antenna 1 provided in the embodiment of the present invention on the XZ plane;

[0039] Fig. 9 The directional diagram of the antenna 1 provided in the embodiment of the present invention on the YZ plane;

[0040] Fig.10 The directional diagram of the antenna 2 provided in the embodiment of the present invention on the XY plane;

[0041] Fig.11 The directional diagram of the antenna 2 provided in the embodiment of the present invention on the XZ plane;

[0042] Fig.12 This is the directional diagram of the antenna 2 provided in the embodiment of the present invention on the YZ plane. DETAILED DESCRIPTION

[0043] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0044] A specific embodiment of the present invention discloses a Bluetooth radio frequency circuit based on dual antennas, the structural diagram of which is shown in FIG. Figure 2 As shown, the Bluetooth radio frequency circuit includes: a BLE chip, a phase shift circuit, an antenna 1 and an antenna 2; wherein the radio frequency port 1 and the radio frequency port 2 of the BLE chip are connected to the two input ends of the phase shift circuit in a one-to-one correspondence, and the two output ends of the phase shift circuit are connected to the antenna 1 and the antenna 2 in a one-to-one correspondence; the antenna 1 and the antenna 2 are arranged relative to each other, and the combination provides an omnidirectional radiation pattern; the radio frequency port 1 and the radio frequency port 2 of the BLE chip are differential outputs.

[0045] During the specific implementation process, taking the above-mentioned Bluetooth RF circuit built into the car key as an example, when Bluetooth positioning is required, the BLE chip generates a positioning signal, and outputs a differential signal with the same amplitude and a phase difference of 180° through RF port 1 and RF port 2. The differential signal is processed by the phase shift circuit, and two signals with the same amplitude and phase are output, and are transmitted through antenna 1 and antenna 2 respectively. Since antenna 1 and antenna 2 can be combined to provide an omnidirectional directional pattern, it can ensure that the positioning signal covers all areas within the radiation range of antenna 1 and antenna 2, effectively improving the positioning accuracy. When antenna 1 or antenna 2 receives the signal fed back by the car, the phase shift circuit works in reverse and will be fed back to the BLE chip through the phase shift circuit, so that the BLE chip can complete the positioning and ranging according to the signal fed back by the car. Since antenna 1 or antenna 2 can accurately receive the signal fed back by the car, the accuracy of Bluetooth ranging is guaranteed.

[0046] Therefore, compared with the prior art, the dual-antenna based Bluetooth radio frequency circuit provided in this embodiment simplifies the circuit structure of the Bluetooth radio frequency circuit, and the implementation of the circuit does not require the help of a control circuit, which effectively reduces the high hardware cost. At the same time, the performance complementarity between multiple antennas is utilized to provide an omnidirectional directional pattern in combination to eliminate the irregular problem of the directional pattern, thereby effectively ensuring the accuracy of Bluetooth ranging.

[0047] Specifically, in order to further reduce the circuit design cost, this embodiment also provides the following phase shift circuit, which uses a combination of inductance and capacitance to generate a 90° phase shift. The structural diagram is shown in FIG. Figure 3 As shown, it includes: capacitors C1 and C2, inductors L1 and L2; wherein, one end of the capacitor C1 is connected to one end of the inductor L1, and the other end of the capacitor C1 is grounded; one end of the capacitor C1 serves as an input end of the phase shift circuit, and the other end of the inductor L1 serves as an output end matched with one input end of the phase shift circuit; one end of the capacitor C2 is connected to one end of the inductor L2, and the other end of the inductor L2 is grounded; one end of the capacitor C2 serves as another input end of the phase shift circuit, and the other end of the inductor C2 serves as an output end matched with another input end of the phase shift circuit.

[0048] In addition, in order to further improve the performance of the Bluetooth RF circuit, the Bluetooth RF circuit provided in this embodiment also includes two filter capacitors; the RF port 1 and the RF port 2 of the BLE chip are respectively connected in series with the corresponding filter capacitors and then connected one-to-one with the two input ends of the phase shift circuit.

[0049] In actual application, the Bluetooth radio frequency circuit is located on a printed circuit board, and antenna no-space zone 1 and antenna no-space zone 2 are set on the printed circuit board; wherein antenna no-space zone 1 carries antenna 1, and antenna no-space zone 2 carries antenna 2. Alternatively, in order to improve the working performance of antenna 1 and antenna 2, the BLE chip and phase shift circuit in the Bluetooth radio frequency circuit are located on the printed circuit board 1; the antenna 1 and antenna 2 in the Bluetooth radio frequency circuit are located on the printed circuit board 2, and the two output ends of the phase shift circuit on the printed circuit board 1 are connected to the antenna 1 and antenna 2 on the printed circuit board 2 in a one-to-one correspondence through a radio frequency connector. At this time, antenna no-space zone 1 and antenna no-space zone 2 are set on the printed circuit board 2; wherein antenna no-space zone 1 carries antenna 1, and antenna no-space zone 2 carries antenna 2.

[0050] Since the antenna's directional pattern cannot be an ideal sphere, it is restricted by the size of the circuit board, and the directionality of its directional pattern will be stronger. Therefore, different relative layout methods are used in the circuit design to compensate for it, making it as spherical as possible. The antenna no-air zone (referring to the area where metal is prohibited around the antenna) is designed according to the design requirements of the antenna, and the copper sheet is removed. Preferably, the relative layout of antenna 1 and antenna 2 is combined to provide an omnidirectional directional pattern. During the specific implementation process, in order to ensure the directional pattern effect, the directional patterns of antenna 1 and antenna 2 can be obtained by simulation or actual measurement, and it is determined whether the combination of the two can provide an omnidirectional antenna pattern. It should be emphasized that all relative layout combinations of antenna 1 and antenna 2 that provide omnidirectional directional patterns are within the protection scope of this embodiment. During the specific implementation process, there is no restriction on the type of antenna, and various forms such as ceramic antennas, PCB antennas and rod antennas can be used.

[0051] After actual engineering implementation, the embodiment of the present invention provides the following optional combinations of antenna 1 and antenna 2:

[0052] (1) Layout of antenna 1 and antenna 2

[0053] Antenna restricted zone 1 and antenna restricted zone 2 are arranged at two diagonal corners of the printed circuit board (or printed circuit board 2), and antenna 1 and antenna 2 are arranged in parallel; the structural schematic diagram is shown in FIG. Figure 4 shown.

[0054] (2) Layout of antenna 1 and antenna 2

[0055] Antenna restricted zone 1 and antenna restricted zone 2 are arranged at two diagonal positions of the printed circuit board (or printed circuit board 2), and antenna 1 and antenna 2 are arranged vertically; the structural schematic diagram is shown in FIG. Figure 5 shown.

[0056] Taking the above layout mode 1 as an example, the schematic diagram of its directional pattern coordinate system is as follows: Figure 6 At this time, the directional patterns of antenna 1 in the XY plane, XZ plane, and YZ plane are as follows: Figure 7 , Figure 8 , Fig. 9 Analysis Figure 7 , Figure 8 , Fig. 9 It can be seen that the antenna patterns in the XZ and YZ planes are relatively circular, and the gain in the XY plane at 225° is lower.

[0057] The directional patterns of antenna 2 in the XY plane, XZ plane, and YZ plane are as follows: Fig.10 , Fig.11 , Fig.12 Analysis Fig.10 , Fig.11 , Fig.12It can be seen that the antenna patterns in the XZ and YZ planes are relatively circular, and the gain in the XY plane at 45° is lower.

[0058] Therefore, considering the above antenna 1 and antenna 2, at their respective low gain locations, the other antenna can provide better gain, thereby compensating for the defects of the radiation pattern to a certain extent, verifying the feasibility of providing an omnidirectional radiation pattern through the relative layout combination of antenna 1 and antenna 2.

[0059] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0060] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A dual-antenna based Bluetooth radio frequency circuit, characterized in that: The Bluetooth radio frequency circuit includes: a BLE chip, a phase shift circuit, an antenna 1 and an antenna 2; wherein, The RF port 1 and RF port 2 of the BLE chip are connected to the two input ends of the phase shift circuit in a one-to-one correspondence, and the two output ends of the phase shift circuit are connected to the antenna 1 and the antenna 2 in a one-to-one correspondence; Antenna 1 and antenna 2 are arranged relative to each other and combined to provide an omnidirectional pattern; The RF port 1 and the RF port 2 of the BLE chip are differential outputs.

2. The dual-antenna based Bluetooth radio frequency circuit according to claim 1, characterized in that: The phase shift circuit includes: capacitors C1 and C2, inductors L1 and L2; wherein, One end of the capacitor C1 is connected to one end of the inductor L1, and the other end of the capacitor C1 is grounded; one end of the capacitor C1 serves as an input end of the phase shift circuit, and the other end of the inductor L1 serves as an output end matched with an input end of the phase shift circuit; One end of the capacitor C2 is connected to one end of the inductor L2, and the other end of the inductor L2 is grounded; one end of the capacitor C2 serves as another input end of the phase shift circuit, and the other end of the inductor C2 serves as an output end matching the other input end of the phase shift circuit.

3. The dual-antenna based Bluetooth radio frequency circuit according to claim 2, characterized in that: The Bluetooth radio frequency circuit also includes two filter capacitors; The RF port 1 and the RF port 2 of the BLE chip are respectively connected in series with corresponding filter capacitors and then connected to the two input terminals of the phase shift circuit one by one.

4. The dual-antenna based Bluetooth radio frequency circuit according to claim 3, characterized in that: The Bluetooth radio frequency circuit is located on a printed circuit board.

5. The dual-antenna based Bluetooth radio frequency circuit according to claim 4, characterized in that: Antenna no-space zone 1 and antenna no-space zone 2 are set on the printed circuit board; wherein antenna no-space zone 1 carries antenna 1, and antenna no-space zone 2 carries antenna 2.

6. The dual-antenna based Bluetooth radio frequency circuit according to claim 3, characterized in that: The BLE chip and the phase shift circuit in the Bluetooth radio frequency circuit are located on a printed circuit board 1; the antenna 1 and the antenna 2 in the Bluetooth radio frequency circuit are located on a printed circuit board 2; The two output ends of the phase shift circuit on the printed circuit board 1 are connected to the antenna 1 and the antenna 2 on the printed circuit board 2 in a one-to-one correspondence through a radio frequency connector.

7. The dual-antenna based Bluetooth radio frequency circuit according to claim 6, characterized in that: An antenna no-space zone and an antenna no-space zone 2 are set on the printed circuit board 2 ; wherein the antenna no-space zone 1 carries the antenna 1 , and the antenna no-space zone 2 carries the antenna 2 .

8. The dual-antenna based Bluetooth radio frequency circuit according to claim 5 or 7, characterized in that: The antenna no-go zone 1 and the antenna no-go zone 2 are arranged on two diagonal corners of the printed circuit board or the printed circuit board 2 .

9. The dual-antenna based Bluetooth radio frequency circuit according to claim 8, characterized in that: Antenna 1 and antenna 2 are arranged in parallel.

10. The dual-antenna based Bluetooth radio frequency circuit according to claim 8, characterized in that: Antenna 1 and antenna 2 are arranged vertically.

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