Design method for broadband Mesh networking communication terminal radio frequency module

Abstract

The invention relates to the technical field of wireless communication, and discloses a design method for a broadband Mesh networking communication terminal radio frequency module, which comprises the following steps: designing the overall structure of the radio frequency module, and optimizing the design of a receiving link, a transmitting link and a transceiving logic control unit based on a radio frequency chip. The transmitting link adopts a preceding-stage, middle-stage and final-stage three-stage power amplification structure and is provided with graded power headroom, and the core is that the transmitting-receiving logic control unit takes a radio frequency chip as a core and synchronously controls the radio frequency switch of the receiving link and the amplifier bias of the transmitting link through an SPI (Serial Peripheral Interface) bus; the radio frequency module designed by the method is high in output power, low in noise, high in reliability and strong in anti-interference capability, can be used for realizing quick and reliable switching of transmitting and receiving states and frequency point selection of a frequency hopping filter, and is integrated with a circulator standing wave protection mechanism to effectively absorb reflection power and protect a power amplifier. The radio frequency module designed by the method is high in output power, low in noise, high in reliability and strong in anti-interference capability; the method is especially suitable for high-speed frequency hopping broadband Mesh ad hoc network communication terminals.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to a design method of a radio frequency module for a broadband Mesh networking communication terminal. BACKGROUND

[0002] With the development of the power system towards intelligentization and distributed management, broadband Mesh networking communication terminals have become the key equipment for realizing efficient and reliable communication. As the core component of wireless communication equipment, the radio frequency module undertakes important functions such as signal tuning, amplification, filtering and anti-interference processing, and its performance directly affects the communication distance, data transmission rate and system stability.

[0003] However, the traditional radio frequency module design has obvious deficiencies in complex electromagnetic environments, such as weak anti-interference ability, unreasonable gain distribution, imperfect standing wave protection mechanism, etc. These problems not only cause a significant decline in communication quality, but also may cause equipment damage. Therefore, how to design a radio frequency module with high gain, low noise characteristics, strong anti-interference ability and perfect standing wave protection mechanism has become a technical problem to be solved in the current wireless communication field, which is of great significance to improve the reliability and stability of power system communication. SUMMARY

[0004] (I) Technical problems solved In view of the deficiencies of the prior art, the present application provides a design method of a radio frequency module for a broadband Mesh networking communication terminal, which solves the problems of insufficient anti-interference ability and uneven gain distribution.

[0005] (II) Technical solutions To achieve the above-mentioned purpose, the present application provides the following technical solutions: a design method of a radio frequency module for a broadband Mesh networking communication terminal, comprising: The receiving link is used for tuning, filtering, amplifying and AGC controlling the received 1.4GHz radio frequency signal, and the received signal is outputted, and the structure thereof comprises: an SMP connector as a radio frequency signal input port, sequentially connected with a pi attenuator for input signal power adjustment, a first radio frequency switch connected with the output end of the pi attenuator to realize transceiver channel switching, a low noise amplifier connected with the output end of the first radio frequency switch to amplify the signal, a second radio frequency switch connected with the output end of the low noise amplifier to realize double channel selection, a frequency hopping filter connected with the output end of the second radio frequency switch for frequency band selection, a third radio frequency switch connected with the output end of the frequency hopping filter to realize output path selection, one selection end of the third radio frequency switch connected with a power load for absorbing reflected power, and the other selection end connected with a radio frequency chip receiving port as a receiving link output; Also includes the transmission link for the baseband input 1.4GHz radio frequency signal after filtering and three-stage power amplifier through the antenna transmission, its structure includes: SMP connector as the baseband signal input port, sequentially connected to the initial amplification of the pre-stage amplifier, the pre-stage amplifier output connected to the low-pass filter to filter out the spurious signal, the low-pass filter output connected to the π type attenuator to adjust the linearity, the π type attenuator output connected to the intermediate amplifier, the intermediate amplifier output connected to the final amplifier to realize the final amplification of the signal, the final amplifier output connected to the circulator, realize the isolation and standing wave protection of transceiver, the circulator output connected to the output filter to further suppress the harmonic, finally through the radio frequency antenna interface transmission; The transceiver logic control unit takes the radio frequency chip as the core, synchronously controls the three radio frequency switches of the receiving link and the three-stage amplifier bias voltage of the transmitting link through the SPI bus, realizes the fast switching of the transceiver state and the frequency point selection of the frequency hopping filter, ensures that the receiving state is disconnected with the transmitting link power supply, the transmitting state is disconnected with the receiving link power supply, and the frequency hopping filter frequency point and the working point of the amplifier are synchronously adjusted when frequency hopping.

[0006] Preferably, the overall design of the radio frequency module includes: The radio frequency module works in the L band of 1.4GHz, the transmitting link adopts a three-stage amplification structure, the maximum output power reaches 20W, the error vector magnitude is less than 6%, and the noise coefficient of the receiving link is less than 6dB; the module integrates the frequency hopping filter, supports full-band frequency hopping, and the frequency hopping rate is not less than 500 hops / s; The transceiver logic control circuit is used for coordinating the signal processing of the receiving link and the transmitting link, and realizing the control function based on the Zynq-7030 chip.

[0007] Preferably, the receiving link optimization design includes: The receiving link cascade gain is 15.6dB, the cascade noise coefficient is 5.49dB, wherein the low-pass filter insertion loss is 0.6dB, the circulator insertion loss is 0.3dB, the radio frequency switch insertion loss is 0.5dB, the frequency hopping filter insertion loss is 3dB, and the low-noise amplifier gain is 21dB; An automatic gain control strategy is adopted, and the specific control logic is that: When the received signal strength is-100dBm to-76dBm, the baseband board automatic gain control gain is fixed to 60dB, and the radio frequency module gain is 15dB; When the signal strength is-76dBm to-20dBm, the baseband board automatic gain control gain is linearly reduced from 60dB to 4dB, and the radio frequency module gain remains 15dB; When the signal strength is between -20dBm and 0dBm, the baseband board automatic gain control gain is reduced from 24dB to 4dB, and the radio frequency module automatic gain control gain is reduced from 15dB to -5dB.

[0008] Preferably, the transmit link optimization design comprises: The transmit link adopts a three-stage amplification structure, the front-stage amplifier is of the RFGA0024 model, the gain is 20dB, the middle-stage amplifier is of the TQP7M9105 model, the gain is 19.5dB, the last-stage amplifier is of the BLF644P model, the gain is 20dB, the total gain is about 60dB, and the maximum output power reaches 20W. The power margin is set, wherein the last-stage amplifier output power is 44dBm, there is a 4.5dB margin from the saturation point 48.5dBm, the middle-stage amplifier output power is 24dBm, there is a 6dB margin from the saturation point 30dBm, and the front-stage amplifier output power is 5dBm, there is a 15dB margin from the saturation point 20dBm.

[0009] Preferably, the standing wave protection mechanism comprises: A circulator is arranged at the output end of the last-stage power amplifier, the high-power signal reflected back from the antenna port is guided to a power load for absorption by using the electromagnetic one-way transmission characteristic, and the open circuit and short circuit protection are supported.

[0010] Preferably, the frequency hopping anti-interference mechanism comprises: The frequency hopping filter supports n working frequency points (for example, 30), covers a 300MHz bandwidth, and the single channel bandwidth is 10MHz. The frequency hopping synchronization adopts a 15-length m sequence as a synchronization word, the residence time is 1.5us, the frame length is 19.2us, the frequency hopping rate is greater than 500 hops / s, and the throughput rate loss is about 9%. The mechanism is verified by MATLAB simulation, when the received signal strength is greater than -92dBm, the detection probability is close to 100%, the missing capture probability is close to 0%, and the false alarm probability is 0.

[0011] (Three) beneficial effects Compared with the prior art, the present application provides a design method for a wideband Mesh networking communication terminal radio frequency module, which has the following beneficial effects: 1. The design method for the wideband Mesh networking communication terminal radio frequency module optimizes the design of the receive link and the transmit link, adopts an automatic gain control (AGC) strategy and a three-stage amplification structure, supports long-distance communication (≥100km), significantly improves the signal transmission efficiency and communication quality while meeting the distributed management requirements of the power system, and adapts to the application requirements of high reliability scenarios.

[0012] 2. The design method of the radio frequency module for the broadband Mesh networking communication terminal supports 30 working frequency points and covers 300MHz bandwidth through integrated frequency hopping filter and m sequence synchronization design, the data transmission success rate is greater than or equal to 90% when 30% frequency points are interfered, the communication stability in a complex electromagnetic environment is significantly enhanced through an efficient frequency hopping anti-interference mechanism, and the influence of signal interference on system performance is effectively reduced.

[0013] 3. The design method of the radio frequency module for the broadband Mesh networking communication terminal optimizes graded gain distribution and realizes open circuit and short circuit protection through a three-stage amplification structure and a circulator standing wave protection design, the service life of equipment is prolonged, the maintenance cost is reduced, and the high reliability operation of power system communication equipment is ensured while the quality of transmitted signals is improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is a schematic diagram of the principle block diagram of the radio frequency module of the application; Figure 2 It is a schematic diagram of the relationship between ADC input and received signal strength; Figure 3 It is a schematic diagram of the relationship between radio frequency chip gain and received signal strength; Figure 4 It is a schematic diagram of the relationship between radio frequency board receiving gain and received signal strength.

[0015] Figure 5 It is a MatLab algorithm simulation detection / fake alarm / miss capture probability curve diagram of the application. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0017] Since the radio frequency module design has obvious deficiencies in a complex electromagnetic environment, the anti-interference ability is weak, the gain distribution is unreasonable, and the standing wave protection mechanism is imperfect, these problems not only cause a significant decline in communication quality, but also may cause equipment damage.

[0018] In the following embodiments, the broadband Mesh communication terminal works in the L band of 1.4GHz based on the radio frequency module, but is not limited to 1.4GHz. The actual values required by each component are taken as an example when the final output receiving link gain is 15.6dB and the noise coefficient is 5.49dB.

[0019] As Figure 1 shown, the radio frequency module block diagram shows a schematic diagram, including a receiving link, a transmitting link and a transceiver logic control unit three parts. The receiving link is connected in turn SMP input connector, π attenuator, the first radio frequency switch, low noise amplifier, the second radio frequency switch, frequency hopping filter and the third radio frequency switch; The transmitting link is connected in turn SMP input connector, preamplifier, low pass filter, π attenuator, intermediate amplifier, final amplifier, circulator and output filter; The control unit takes the radio frequency chip as the core, and controls the three radio frequency switches of the receiving link and the three-stage amplifier bias voltage of the transmitting link through the SPI bus synchronization, realizes the fast switching of the receiving and transmitting states and the frequency point selection of the frequency hopping filter, and realizes the reliable switching of the receiving and transmitting states under the mechanical interface of the plug-in radio frequency connector.

[0020] In the embodiment, in the transmitting link, when the excitation signal output by the radio frequency chip control circuit is-7dBm, the transmitting channel gain requires at least 50dB, and in the present example, a three-stage amplification structure is adopted, and the three-stage amplifier can provide about 60dB gain. The preamplifier is configured with the model RFGA0024, and the gain is 20dB; The intermediate amplifier is configured with the model TQP7M9105, and the gain is 19.5dB; The final amplifier is configured with the model BLF644P, and the gain is 20dB.

[0021] Further, RFGA0024 and TQP7M9105 are used as the drive stage of the final BLF644P, when the total power output is 20W (43dBm), considering the rear stage insertion loss, the BLF644P output power is about 44dBm, which is 4.5dB away from the saturation power point. At this time, the TQP7M9105 output power is 24dBm, which is 6dB away from the saturation power, and the linearity will not be under pressure; The RFGA0024 output power is about +5dBm, which is 15dB away from the saturation power, and there will be no compression phenomenon.

[0022] As Figure 2 shown, the internal ADC input range of the radio frequency chip selected in the embodiment is selected as-10dBFS~ -40dBFS, and the ADC input is calculated according to the formula: dBFS=Pin (dBm) +Analog Gain (dB)-13dB+4.1dB. In the present example, when the minimum receiving signal is-100dBm, the Analog Gain is 69dB, and the ADC input is calculated as-40dBFS.

[0023] As Figure 3 and Figure 4As shown, an automatic gain control (AGC) strategy is adopted, when a weak signal is received, the receiving link gain is increased, when the received signal becomes strong, the gain is reduced, so as to keep the ADC input signal strength relatively stable. When the received signal strength is between -100dBm and -76dBm, the radio frequency chip gain needs to be fixed at 60dB, and the radio frequency module board gain is fixed at 15dB; when the signal strength is between -76dBm and -20dBm, the radio frequency chip gain is linearly reduced from 60dB to 4dB, and the radio frequency module board gain is fixed at 15dB; when the signal strength is between -20dBm and 0dBm, the radio frequency chip gain is reduced from 24dB to 4dB, and the radio frequency module board automatic gain control gain is reduced from 15dB to -5dB, thereby completing the dynamic range change of a wide range of received signals.

[0024] In this embodiment, a frequency hopping filter is integrated in the transmitting link, and the anti-interference mechanism is enhanced. In this example, the frequency hopping operating frequency points are selected as follows:

[0025] A total of 30 operating frequency points are selected, and the actual coverage bandwidth of the 10MHz signal bandwidth is 300MHz.

[0026] In this example, the frequency hopping synchronization design is as follows. Both the Barker code and the m sequence have good autocorrelation characteristics, but the length of the Barker code is only 13, and the length of the m sequence can be In this example, an m sequence with a length of 15 is selected as the frequency hopping synchronization word. With a 50MHz operating bandwidth and a pseudo code rate of 12.5Mcps, the receiving sensitivity in one observation period is:

[0027] Through the frequency hopping synchronization design, the receiving sensitivity value is better than the receiving sensitivity of the 5MHz basic rate (about -82dBm).

[0028] As shown in Figure 5 the MatLab algorithm simulation-95dBm received signal strength sensitivity detection / fake alarm / miss capture probability curve diagram, when the received signal strength is greater than -92dBm, the detection probability tends to 1, and the miss capture probability tends to 0, and the false alarm probability is 0 under all conditions. The performance of frequency hopping synchronization is much better than that of data frame reception, so as to make the data frame reception of wideband Mesh networking communication accurate.

[0029] The advantages of the wideband Mesh networking communication terminal radio frequency module proposed in this example are as follows: 1. Optimize the receiving link design, adopt an automatic gain control (AGC) strategy, and thus complete the dynamic range change of a wide range of received signals.

[0030] 2. The optimization of the transmitting chain design, using a three-stage amplification structure, configuring the pre-stage, intermediate and final amplifiers, setting the hierarchical gain distribution and power margin, so that the signal does not appear compression phenomenon.

[0031] 3. Designing a standing wave protection mechanism, configuring a circulator at the output end of the final power amplifier, guiding the high-power signal reflected back by the antenna port to the power load absorption, thus protecting the final power amplifier and the receiving chain from damage.

[0032] 4. Designing a frequency hopping anti-interference mechanism, integrating a frequency hopping filter, so as to have better anti-interference performance.

[0033] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A design method for a radio frequency module of a broadband mesh networking communication terminal, characterized in that, include: The receiving link is used to tune, filter, amplify, and control the received 1.4GHz RF signal. After receiving the signal, it outputs the 1.4GHz RF signal. The transmission link is used to transmit the output 1.4GHz radio frequency signal through an antenna after filtering and three-stage power amplification. The transceiver logic control unit uses an RF chip as its core and synchronously controls the bias voltage of the three RF switches in the receiving link and the three-stage amplifier in the transmitting link via the SPI bus to achieve rapid switching between the transmitting and receiving states and frequency selection of the frequency hopping filter.

2. The design method for a radio frequency module for a broadband mesh networking communication terminal according to claim 1, characterized in that: The receiving link uses an SMP connector as the RF signal input port, which is sequentially connected to a π-type attenuator for input signal power adjustment. The output of the π-type attenuator is connected to a first RF switch to switch between transmit and receive channels. The output of the first RF switch is connected to a low-noise amplifier for signal amplification. The output of the low-noise amplifier is connected to a second RF switch for dual-channel selection. The output of the second RF switch is connected to a frequency hopping filter for frequency band selection. The output of the frequency hopping filter is connected to a third RF switch for output path selection. One selection terminal of the third RF switch is connected to a power load to absorb reflected power, and the other selection terminal is connected to the receiving port of the RF chip as the receiving link output. The receiving link is used to tune, filter, amplify, and perform AGC control on the received 1.4GHz RF signal before outputting it.

3. The receiving link according to claim 2, characterized in that, The receiving link is controlled collaboratively by the transceiver logic control unit, employing an automatic gain control (AGC) strategy. The specific control logic is as follows: When the received signal strength is between -100dBm and -76dBm, the baseband board's automatic gain control gain is fixed at 60dB, and the RF module gain is 15dB. When the signal strength is between -76dBm and -20dBm, the baseband board's automatic gain control gain linearly decreases from 60dB to 4dB, while the RF module gain remains at 15dB. When the signal strength is between -20dBm and 0dBm, the baseband board's automatic gain control gain decreases from 24dB to 4dB, and the RF module's automatic gain control gain decreases from 15dB to -5dB.

4. The design method for a radio frequency module for a broadband mesh networking communication terminal according to claim 1, characterized in that: The transmit link uses an SMP connector as the baseband signal input port, which is sequentially connected to a preamplifier for initial amplification. The output of the preamplifier is connected to a low-pass filter to filter out spurious signals. The output of the low-pass filter is connected to a π-type attenuator to adjust linearity. The output of the π-type attenuator is connected to an intermediate amplifier. The output of the intermediate amplifier is connected to a final amplifier to achieve final signal amplification. The output of the final amplifier is connected to a circulator, and a standing wave protection mechanism is designed to achieve transmit-receive isolation. The output of the circulator is connected to an output filter to further suppress harmonics. Finally, the signal is transmitted through the RF antenna interface. The transmit link is used to transmit the 1.4GHz RF signal input from the baseband after filtering and three-stage power amplification through the antenna.

5. The transmission link according to claim 4, characterized in that: The transmission link adopts a three-stage amplification structure. The pre-amplifier is model RFGA0024 with a gain of 20dB; the intermediate amplifier is model TQP7M9105 with a gain of 19.5dB; and the final amplifier is model BLF644P with a gain of 20dB. The total gain is approximately 60dB, and the maximum output power reaches 20W. The power margins are set as follows: the final stage amplifier output power is 44dBm, with a 4.5dB margin from the saturation point of 48.5dBm; the intermediate stage amplifier output power is 24dBm, with a 6dB margin from the saturation point of 30dBm; and the preamplifier output power is 5dBm, with a 15dB margin from the saturation point of 20dBm.

6. The design method for a radio frequency module for a broadband mesh networking communication terminal according to claim 1, characterized in that: The transceiver logic control unit is based on an RF chip. It synchronously controls the bias voltage of the three RF switches in the receiving link and the three-stage amplifier in the transmitting link via the SPI bus. This enables rapid switching between receiving and transmitting states and selection of the frequency point of the frequency hopping filter. It ensures that the power supply to the transmitting link is disconnected in the receiving state and the power supply to the receiving link is disconnected in the transmitting state. During frequency hopping, the filter frequency point and the operating point of the amplifier are adjusted synchronously, so that the RF module can reliably switch between receiving and transmitting states through the mechanical interface of the plug-in RF connector.

7. The design method for a radio frequency module for a broadband mesh networking communication terminal according to claim 1, characterized in that: Standing wave protection mechanisms include: A circulator is installed at the output of the final stage power amplifier. Taking advantage of the unidirectional transmission characteristics of electromagnetic waves, the high-power signal reflected back from the antenna port is directed to the power load for absorption, supporting open-circuit and short-circuit protection.

8. The design method for a radio frequency module for a broadband mesh networking communication terminal according to claim 1, characterized in that: Frequency hopping filters include: The frequency hopping filter supports n operating frequencies, covering a bandwidth of 300MHz, with a single-channel bandwidth of 10MHz. Frequency hopping synchronization uses a 15-bit m-sequence as the synchronization word, with a dwell time of 1.5μs, a frame length of 19.2μs, a frequency hopping rate greater than 500 hops / second, and a throughput loss of approximately 9%.

9. The design method for a radio frequency module for a broadband mesh networking communication terminal according to claim 1, characterized in that: The frequency hopping anti-interference mechanism was verified by MATLAB simulation. When the received signal strength is greater than -92dBm, the detection probability is close to 100%, the missed detection probability is close to 0%, and the false alarm probability is 0.

10. The design method for a radio frequency module for a broadband mesh networking communication terminal according to claim 1, characterized in that: The radio frequency module is designed based on radio frequency chips, and the transceiver logic control circuit is based on the Zynq-7030 chip to achieve signal processing coordination.

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