Channel calibration system and method for a radio frequency hardware-in-the-loop test system

Abstract

This invention provides a channel calibration system and method for a radio frequency (RF) semi-physical testing system. The implementation system comprises four subsystems: one tuning and control subsystem and three RF subsystems. The three RF subsystems are directly connected via RF cables, eliminating the need for additional equipment such as calibration networks or switch matrices. Each RF subsystem consists of a computer control unit, a digital processing unit, and an RF transceiver unit. This method eliminates the need for additional equipment such as calibration networks, switch matrices, instruments, or microwave anechoic chambers, achieving automatic channel calibration through the system itself. This invention achieves automatic channel calibration across multiple dimensions between subsystems through the system itself, offering advantages such as high calibration efficiency, low complexity, and good calibration results. It effectively ensures the reliability, stability, and consistency of test results across different dimensions, demonstrating strong versatility and engineering feasibility.

Description

Technical Field

[0001] This invention relates to the field of electronic countermeasures, and more particularly to a channel calibration system and method for a radio frequency hardware-in-the-loop test system. Background Technology

[0002] With the continuous development of electronic technology and modern warfare, the real battlefield environment places higher demands on the combat systems and equipment of both sides. To adapt to the needs of future warfare, combat systems and equipment require rapid upgrades and iterations. Therefore, a testing system is needed to address the issues of time, cost, and risk encountered during the upgrade and iteration process. Radio frequency (RF) hardware-in-the-loop (HIL) testing systems connect RF-grade physical components to the test loop for real-time simulation, offering higher realism and cost-effectiveness compared to other types of testing systems. Currently, RF HIL systems are developing towards more systems, more channels, and more dimensions. To meet the development needs of RF HIL systems, automatic channel calibration across multiple systems and dimensions is a crucial technical problem that must be solved.

[0003] Conventional channel calibration methods typically involve adding additional equipment such as calibration networks, switching matrices, instruments, and microwave anechoic chambers. This not only increases system complexity and cost but also results in cumbersome operation, low calibration efficiency, and poor calibration performance. Furthermore, conventional channel calibration methods generally only consider channel calibration within a few limited dimensions, such as short-term time, finite fixed frequency points, and finite channel gain, failing to guarantee the reliability, stability, and consistency of test results across different dimensions. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a channel calibration system and method for a radio frequency semi-physical test system. The aim is to achieve multi-dimensional automatic channel calibration through the system itself without additional equipment such as calibration networks, switch matrices, instruments, or microwave anechoic chambers.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a channel calibration system for a radio frequency (RF) semi-physical test system, comprising a tuning control subsystem, a first RF subsystem, a second RF subsystem, and a third RF subsystem. The tuning control subsystem interacts with the first RF subsystem, the second RF subsystem, and the third RF subsystem via a network. The first RF subsystem and the second RF subsystem are provided with N1 RF receiving channels and N2 RF transmitting channels, and the second RF subsystem and the third RF subsystem are provided with N3 RF receiving channels and N4 RF transmitting channels.

[0007] Furthermore, the first radio frequency subsystem, the second radio frequency subsystem, and the third radio frequency subsystem all include a computer control unit. The computer control unit interacts with the digital processing unit via a network, and the digital processing unit and the radio frequency transceiver unit are connected via an intermediate frequency cable and a control bus.

[0008] Furthermore, the computer control unit is composed of a computer; the digital processing unit is composed of a DSP unit, an FPGA unit, an N-channel AD acquisition unit, and an M-channel DA transmission unit; the radio frequency transceiver unit is composed of N receiving channels and M transmitting channels; each receiving channel is composed of a gain control unit, a down-conversion unit, a pattern modulation unit, and a polarization control unit; each transmitting channel is composed of an up-conversion unit, a gain control unit, a pattern modulation unit, and a polarization control unit.

[0009] Furthermore, a channel calibration method for an RF semi-physical test system, implemented using the aforementioned channel calibration system, further includes:

[0010] In the receive correction mode, the external N-channel RF input signals are converted into N-channel intermediate frequency input signals after passing through N-channel receive channels. The N-channel intermediate frequency input signals are acquired by N-channel AD acquisition units and then processed by FPGA unit, DSP unit and computer to obtain the correction coefficient.

[0011] In transmit calibration mode, M calibration intermediate frequency signals are generated sequentially through the computer, DSP unit, FPGA unit, and M-channel DA transmitter unit. After passing through the M-channel transmit channels, the M calibration intermediate frequency signals are converted into M-channel radio frequency output signals.

[0012] Furthermore, it also includes:

[0013] Sa, after the system is powered on, the command and control subsystem initiates a system self-test command. The first radio frequency subsystem, the second radio frequency subsystem, and the third radio frequency subsystem perform self-tests and report the status of their internal modules.

[0014] After the self-test is passed, the guidance and control subsystem determines the correction dimension and the specific parameters of each dimension according to the content of the specific test subject, and sends them to the first radio frequency subsystem, the second radio frequency subsystem and the third radio frequency subsystem respectively.

[0015] After the Sc command is issued, the guidance and control subsystem initiates a system calibration command to begin multi-dimensional calibration of the system channels.

[0016] Sd. After receiving the system calibration command, the first radio frequency subsystem first enters the transmit calibration mode, generates radio frequency calibration signals of different dimensions and parameters in sequence, and notifies the second radio frequency subsystem to start receiving and processing.

[0017] After receiving the notification, Se and the second radio frequency subsystem enter the receiving correction mode, collect radio frequency correction signals of different dimensions and parameters, perform correction and storage respectively, and end the receiving correction mode.

[0018] After the second radio frequency subsystem ends the receive correction mode, it enters the transmit correction mode, and sequentially generates radio frequency correction signals of different dimensions and parameters, and notifies the first radio frequency subsystem to start receiving processing.

[0019] Sg. After receiving the notification, the first radio frequency subsystem enters the receiving correction mode, collects radio frequency correction signals of different dimensions and parameters, performs correction and storage respectively, and ends the receiving correction mode.

[0020] Sh, after the first radio frequency subsystem ends the receive calibration mode, the transmit / receive channel calibration between the first radio frequency subsystem and the second radio frequency subsystem is completed. The first radio frequency subsystem sends a calibration command to the third radio frequency subsystem to start the transmit / receive channel calibration between the third radio frequency subsystem and the second radio frequency subsystem.

[0021] Si, the third RF subsystem, and the second RF subsystem perform transmit / receive channel calibration according to the steps described in Sd-Sg. After calibration is completed, a calibration completion command is sent to the instruction control subsystem to end the calibration of the system channels.

[0022] Furthermore, the channel calibration steps between the first RF subsystem, the second RF subsystem, and the third RF subsystem are as follows: first, channel calibration is performed between the first RF subsystem and the second RF subsystem, and then channel calibration is performed between the second RF subsystem and the third RF subsystem.

[0023] SI. First, the first radio frequency subsystem transmits N2 correction signals, and the second radio frequency subsystem receives N2 correction signals; then, the second transmitting subsystem transmits N1 correction signals, and the first radio frequency subsystem receives N1 correction signals.

[0024] SII. When the first RF subsystem transmits N2 correction signals and the second RF subsystem receives N2 correction signals, the computer control unit of the first RF subsystem sends waveform parameters to the digital processing unit of the first RF subsystem.

[0025] SIII. Under the control of the correction mode control module, the baseband data generation module in the digital processing unit of the first radio frequency subsystem generates single-channel baseband correction transmission data according to the waveform parameters. Under the control of the correction timing generation module, the digital upconversion module converts the single-channel baseband correction transmission data into multiple intermediate frequency correction transmission signals and sends them to the radio frequency transceiver unit of the first radio frequency subsystem.

[0026] SIV, the transmit channel in the radio transceiver unit of the first radio frequency subsystem, converts multiple intermediate frequency corrected transmit signals into multiple radio frequency corrected transmit signals and sends them to the second radio frequency subsystem;

[0027] After receiving multiple radio frequency correction transmission signals, the transceiver channel control module in the radio frequency transceiver unit of the second radio frequency subsystem controls the receiving channel according to the frequency code, gain code, pattern coefficient, and polarization coefficient, and converts the multiple radio frequency correction transmission signals into multiple intermediate frequency correction receiving signals, which are then sent to the digital processing unit of the second radio frequency subsystem.

[0028] Under the control of the correction timing generation module, the digital downconversion module of the digital processing unit of the second radio frequency subsystem SVI converts multiple intermediate frequency correction received signals into multiple baseband correction received data. After being processed by the correction coefficient calculation module, the correction coefficient is obtained, and after being timestamped, it is sent to the computer control unit of the second radio frequency subsystem.

[0029] The beneficial effects of this invention are as follows: the method and system generate radio frequency correction signals from multiple dimensions such as time, space, energy, frequency, polarization and waveform, and collect and analyze the signals to complete the multi-dimensional correction of the test system channels. It has the advantages of high equipment correction efficiency, low complexity and good correction effect, effectively ensuring the reliability, stability and consistency of the test results of the system under different dimensions, and has strong versatility and engineering feasibility. Attached Figure Description

[0030] Figure 1 This is a block diagram of a channel calibration system for a radio frequency semi-physical testing system according to the present invention;

[0031] Figure 2 A block diagram of the radio frequency subsystem;

[0032] Figure 3 This is a schematic diagram of the channel calibration principle. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Please see Figures 1 to 3 A channel calibration system for a radio frequency (RF) semi-physical test system includes a tuning control subsystem 1, a first RF subsystem 2, a second RF subsystem 3, and a third RF subsystem 4. The tuning control subsystem 1 interacts with the first RF subsystem 2, the second RF subsystem 3, and the third RF subsystem 4 via a network. The first RF subsystem 2 and the second RF subsystem 3 are provided with N1 RF receiving channels 701 and N2 RF transmitting channels 702. The second RF subsystem 3 and the third RF subsystem 4 are provided with N3 RF transmitting channels 703 and N4 RF receiving channels 704.

[0035] The radio frequency subsystems do not require additional equipment such as calibration networks or switch matrices for connection, nor do they require additional equipment such as instruments or microwave anechoic chambers for auxiliary calibration.

[0036] The first radio frequency subsystem 2, the second radio frequency subsystem 3, and the third radio frequency subsystem 4 each include a computer control unit 5. The computer control unit 5 and the digital processing unit 6 interact with each other via a network. The digital processing unit 6 and the radio frequency transceiver unit 7 are connected via an intermediate frequency cable and a control bus.

[0037] The computer control unit 5 consists of a computer 501; the digital processing unit 6 consists of a DSP unit 601, an FPGA unit 602, an N-channel AD acquisition unit 603, and an M-channel DA transmission unit 604; the radio frequency transceiver unit 7 consists of an N-channel receiving channel 701 and an M-channel transmitting channel 702; each receiving channel 701 consists of a gain control unit 7011, a down-conversion unit 7012, a pattern modulation unit 7013, and a polarization control unit 7014; each transmitting channel 702 consists of an up-conversion unit 7021, a gain control unit 7022, a pattern modulation unit 7023, and a polarization control unit 7024.

[0038] The computer control unit uses a general-purpose computer as its hardware platform; the digital processing unit adopts a DSP+FPGA+AD+DA architecture to realize the acquisition and output of multiple intermediate frequency signals; the radio frequency transceiver unit adopts a frequency conversion+gain control+pattern modulation+polarization control architecture to realize the transmission and reception of radio frequency signals and control.

[0039] A channel calibration method for a radio frequency (RF) semi-physical test system, implemented using the aforementioned channel calibration system, further includes:

[0040] In the receive correction mode, the external N-channel RF input signals are converted into N-channel intermediate frequency input signals after passing through the N-channel receive channel 701. The N-channel intermediate frequency input signals are acquired by the N-channel AD acquisition unit 603 and then processed by the FPGA unit 602, DSP unit 601 and computer 501 to obtain the correction coefficient.

[0041] In transmit calibration mode, M-channel calibration intermediate frequency signals are generated sequentially through computer 501, DSP unit 601, FPGA unit 602, and M-channel DA transmit unit 604. The M-channel calibration intermediate frequency signals are converted into M-channel radio frequency output signals after passing through M-channel transmit channel 702.

[0042] Also includes:

[0043] Sa, after the system is powered on, the instruction control subsystem initiates a system self-test command. The first radio frequency subsystem 2, the second radio frequency subsystem 3, and the third radio frequency subsystem 4 perform self-tests and report the status of their internal modules.

[0044] After the self-test is passed, the guidance and control subsystem determines the correction dimension and the specific parameters of each dimension according to the content of the specific test subject, and sends them to the first radio frequency subsystem 2, the second radio frequency subsystem 3 and the third radio frequency subsystem 4 respectively.

[0045] After the Sc command is issued, the guidance and control subsystem initiates a system calibration command to begin multi-dimensional calibration of the system channels.

[0046] Sd. After receiving the system calibration command, the first radio frequency subsystem 2 first enters the transmit calibration mode, generates radio frequency calibration signals of different dimensions and parameters in sequence, and notifies the second radio frequency subsystem 3 to start receiving and processing.

[0047] After receiving the notification, Se and the second radio frequency subsystem 3 enter the receiving correction mode, collect radio frequency correction signals of different dimensions and parameters, perform correction and storage respectively, and end the receiving correction mode.

[0048] After the second radio frequency subsystem 4 ends the receive correction mode, it enters the transmit correction mode, and generates radio frequency correction signals of different dimensions and parameters in sequence, and notifies the first radio frequency subsystem 2 to start receiving processing.

[0049] Sg, After receiving the notification, the first radio frequency subsystem 2 enters the receiving correction mode, collects radio frequency correction signals of different dimensions and parameters, performs correction and storage respectively, and ends the receiving correction mode.

[0050] Sh, after the first RF subsystem 2 ends the receive calibration mode, the transmit / receive channel calibration between the first RF subsystem 2 and the second RF subsystem 3 is completed. The first RF subsystem 2 sends a calibration command to the third RF subsystem 4 to start the transmit / receive channel calibration between the third RF subsystem 4 and the second RF subsystem 3.

[0051] Si, the third RF subsystem 4 and the second RF subsystem 3 perform transmit and receive channel calibration according to the steps of Sd-Sg. After calibration is completed, a calibration completion command is sent to the instruction control subsystem to end the calibration of the system channel.

[0052] The channel calibration steps between the first RF subsystem 2, the second RF subsystem 3, and the third RF subsystem 4 are as follows: first, channel calibration is performed between the first RF subsystem 2 and the second RF subsystem 3, and then channel calibration is performed between the second RF subsystem 3 and the third RF subsystem 4.

[0053] S1. First, the first radio frequency subsystem 2 transmits N2 correction signals, and the second radio frequency subsystem 3 receives N2 correction signals; then, the second transmission subsystem 3 transmits N1 correction signals, and the first radio frequency subsystem 2 receives N1 correction signals.

[0054] SII. When the first RF subsystem 2 transmits N2 correction signals and the second RF subsystem 3 receives N2 correction signals, the computer control unit of the first RF subsystem 2 sends the waveform parameters to the digital processing unit of the first RF subsystem 2.

[0055] SIII. Under the control of the correction mode control module, the baseband data generation module in the digital processing unit of the first radio frequency subsystem 2 generates single-channel baseband correction transmission data according to the waveform parameters. Under the control of the correction timing generation module, the digital upconversion module converts the single-channel baseband correction transmission data into multiple intermediate frequency correction transmission signals and sends them to the radio frequency transceiver unit of the first radio frequency subsystem 2.

[0056] SIV, the transmit channel in the radio frequency transceiver unit of the first radio frequency subsystem 2, converts multiple intermediate frequency corrected transmit signals into multiple radio frequency corrected transmit signals and sends them to the second radio frequency subsystem 3;

[0057] After receiving multiple radio frequency correction transmission signals, the transceiver channel control module in the radio frequency transceiver unit of the second radio frequency subsystem 3 controls the receiving channel according to the frequency code, gain code, pattern coefficient, and polarization coefficient, and converts the multiple radio frequency correction transmission signals into multiple intermediate frequency correction receiving signals, which are then sent to the digital processing unit of the second radio frequency subsystem 3.

[0058] Under the control of the correction timing generation module, the digital downconversion module of the digital processing unit of the second radio frequency subsystem 3 in SVI converts multiple intermediate frequency correction received signals into multiple baseband correction received data. After being processed by the correction coefficient calculation module, the correction coefficient is obtained, and after being timestamped, it is sent to the computer control unit of the second radio frequency subsystem 3.

[0059] Two RF subsystems perform channel calibration, enabling calibration of the transmit and receive channels across multiple dimensions, including time, space, energy, frequency, polarization, and waveform. The digital processing unit (DMU) generates single-channel baseband calibration transmit data based on different waveform parameters, such as waveform pattern and PDW descriptor, achieving waveform-dimensional calibration. The DMU also generates frequency codes (frequency), gain codes (energy), pattern coefficients (space), and polarization coefficients (polarization), driving the RF transceiver unit to transmit and receive multiple RF calibration signals, achieving calibration across multiple dimensions such as frequency, energy, space, and polarization. The DMU timestamps the calibration coefficients obtained from each calibration and reports them to the computer control unit for storage. This ensures consistency between results from two experiments over a longer time interval, while meeting the calibration requirements of the current experiment, thus achieving time-dimensional calibration.

[0060] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be defined by the appended claims.

Claims

1. A channel calibration system for a radio frequency semi-physical testing system, characterized in that: It includes a tuning and control subsystem (1), a first radio frequency subsystem (2), a second radio frequency subsystem (3) and a third radio frequency subsystem (4). The tuning and control subsystem (1) interacts with the first radio frequency subsystem (2), the second radio frequency subsystem (3) and the third radio frequency subsystem (4) through a network. The first radio frequency subsystem (2) and the second radio frequency subsystem (3) are provided with N1 radio frequency receiving channels (701) and N2 radio frequency transmitting channels (702). The second radio frequency subsystem (3) and the third radio frequency subsystem (4) are provided with N3 radio frequency transmitting channels (703) and N4 radio frequency receiving channels (704). The first radio frequency subsystem (2), the second radio frequency subsystem (3) and the third radio frequency subsystem (4) all include a computer control unit (5), the computer control unit (5) and the digital processing unit (6) interact with each other through a network, and the digital processing unit (6) and the radio frequency transceiver unit (7) are connected through an intermediate frequency cable and a control bus; The computer control unit (5) is composed of a computer (501); the digital processing unit (6) is composed of a DSP unit (601), an FPGA unit (602), an N-channel AD acquisition unit (603), and an M-channel DA transmission unit (604); the radio frequency transceiver unit (7) is composed of an N1-channel radio frequency receiving channel (701) and an N2-channel radio frequency transmitting channel (702); each of the N1-channel radio frequency receiving channels (701) is composed of a first gain control unit (7011), a down-conversion unit (7012), a first pattern modulation unit (7013), and a first polarization control unit (7014); each of the N2-channel radio frequency transmitting channels (702) is composed of an up-conversion unit (7021), a second gain control unit (7022), a second pattern modulation unit (7023), and a second polarization control unit (7024).

2. A channel calibration method for a radio frequency hardware-in-the-loop test system, the method comprising: The method employs a channel calibration system for a radio frequency semi-physical test system as described in claim 1, and further includes: In the receiving correction mode, the external N-channel RF input signals are converted into N-channel intermediate frequency input signals after passing through the N1-channel RF receiving channel (701). The N-channel intermediate frequency input signals are acquired by the N-channel AD acquisition unit (603) and then processed by the FPGA unit (602), DSP unit (601) and computer (501) to obtain the correction coefficient. In the transmit calibration mode, M-channel calibration intermediate frequency signals are generated sequentially through the computer (501), DSP unit (601), FPGA unit (602), and M-channel DA transmit unit (604). The M-channel calibration intermediate frequency signals are converted into M-channel RF output signals after passing through the N2-channel RF transmit channel (702).

3. The channel calibration method for a radio frequency semi-physical testing system according to claim 2, characterized in that, Also includes: Sa, after the system is powered on, the instruction control subsystem (1) initiates a system self-test command, and the first radio frequency subsystem (2), the second radio frequency subsystem (3) and the third radio frequency subsystem (4) perform self-tests and report the status of their internal modules respectively; Sb, after the self-test is passed, the guidance and control subsystem (1) determines the correction dimension and the specific parameters of each dimension according to the content of the specific test subject, and sends them to the first radio frequency subsystem (2), the second radio frequency subsystem (3) and the third radio frequency subsystem (4) respectively. After the Sc is issued, the guidance and control subsystem (1) initiates a system calibration command to start multi-dimensional calibration of the system channels; Sd, After receiving the system calibration command, the first radio frequency subsystem (2) first enters the transmit calibration mode, generates radio frequency calibration signals of different dimensions and different parameters in sequence, and notifies the second radio frequency subsystem (3) to start receiving and processing; After receiving the notification, Se and the second radio frequency subsystem (3) enter the receiving correction mode, collect radio frequency correction signals of different dimensions and different parameters, perform correction and storage respectively, and end the receiving correction mode. After the second radio frequency subsystem (3) ends the receiving correction mode, it enters the transmitting correction mode and generates radio frequency correction signals of different dimensions and different parameters in sequence, and notifies the first radio frequency subsystem (2) to start receiving processing. Sg, After receiving the notification, the first radio frequency subsystem (2) enters the receiving correction mode, collects radio frequency correction signals of different dimensions and different parameters, performs correction and storage respectively, and ends the receiving correction mode; Sh、After the first radio frequency subsystem (2) ends the receiving correction mode, the transceiver channel correction between the first radio frequency subsystem (2) and the second radio frequency subsystem (3) is completed. The first radio frequency subsystem (2) sends a correction command to the third radio frequency subsystem (4) to start the transceiver channel correction between the third radio frequency subsystem (4) and the second radio frequency subsystem (3). Si, the third RF subsystem (4) and the second RF subsystem (3) perform transceiver channel calibration according to the steps of Sd-Sg. After calibration, a calibration completion command is sent to the instruction control subsystem (1) to end the calibration of the system channel.

4. The channel calibration method of a radio frequency hardware-in-the-loop test system according to claim 3, wherein, The channel calibration steps between the first radio frequency subsystem (2), the second radio frequency subsystem (3) and the third radio frequency subsystem (4) are as follows: first, channel calibration is performed between the first radio frequency subsystem (2) and the second radio frequency subsystem (3), and then channel calibration is performed between the second radio frequency subsystem (3) and the third radio frequency subsystem (4); SI. First, the first radio frequency subsystem (2) transmits N2 correction signals, and the second radio frequency subsystem (3) receives N2 correction signals; then the second radio frequency subsystem (3) transmits N1 correction signals, and the first radio frequency subsystem (2) receives N1 correction signals. SII. When the first radio frequency subsystem (2) transmits N2 correction signals and the second radio frequency subsystem (3) receives N2 correction signals, the computer control unit of the first radio frequency subsystem (2) sends the waveform parameters to the digital processing unit of the first radio frequency subsystem (2). SIII. Under the control of the correction mode control module, the baseband data generation module in the digital processing unit of the first radio frequency subsystem (2) generates single-channel baseband correction transmission data according to the waveform parameters. Under the control of the correction timing generation module, the digital upconversion module converts the single-channel baseband correction transmission data into multiple intermediate frequency correction transmission signals and sends them to the radio frequency transceiver unit of the first radio frequency subsystem (2). SIV, the transmit channel in the radio transceiver unit of the first radio frequency subsystem (2) converts the multiple intermediate frequency correction transmit signals into multiple radio frequency correction transmit signals and sends them to the second radio frequency subsystem (3). After receiving the multiple radio frequency correction transmission signals, the transceiver channel control module in the radio frequency transceiver unit of the second radio frequency subsystem (3) controls the receiving channel according to the frequency code, gain code, pattern coefficient, and polarization coefficient, and converts the multiple radio frequency correction transmission signals into multiple intermediate frequency correction receiving signals, which are then sent to the digital processing unit of the second radio frequency subsystem (3). The digital downconversion module of the digital processing unit of the second radio frequency subsystem (3) converts multiple intermediate frequency correction received signals into multiple baseband correction received data under the control of the correction timing generation module. After being processed by the correction coefficient calculation module, the correction coefficient is obtained, and after being timestamped, it is sent to the computer control unit of the second radio frequency subsystem (3).

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