What Is a Network Interface Adapter?

The interface adapter is a signal hub between the testing equipment and the equipment to be tested, and gathers a large number of signals to be tested. Its function is to transfer the signals of the interfaces of the equipment to be tested to the measuring instrument through different conditioning modules. With the universal interface adapter, the user can automatically switch to different test objects by controlling the matrix switch of the measurement and control computer, thereby achieving the purpose of one test system corresponding to multiple test objects, and solving the problem of repeated development of the interface adapter.

As an important part of the automatic test system, the interface adapter is the bridge between the device under test and the test instrument. At present, most measuring instruments can be used universally, and the interface adapter is dedicated. If one object to be measured corresponds to one interface adapter, it will make the interface adapter variety, the test system huge, and waste resources. With the universal interface adapter, the user can control the matrix switch of the measurement and control computer to automatically switch to adapt to different test objects, thereby achieving the purpose of one test system corresponding to multiple test objects, and solving the problem of repeated development of the interface adapter. ^[1]

The interface adapter is a signal hub between the testing equipment and the equipment to be tested, and gathers a large number of signals to be tested. Its function is to transfer the signals of the interfaces of the equipment to be tested to the measuring instrument through different conditioning modules. In general, the design of a universal interface adapter should follow these principles:

1) The interface adapter design should use passive components as much as possible. Active devices are more affected by environmental parameters and increase the uncertainty of test results.

2) Modular and standardized design should be adopted in the design to increase the reliability and maintainability of the interface adapter.

3) It can realize the electrical isolation between the device under test and the test instrument, and has a certain safety protection function for the test system.

4) The interface adapter should contain the necessary calibration design, which can play a certain calibration function to the measurement error brought by the adapter.

With the expansion of network scale and technological progress, the communication network structure is becoming more and more complex. At present, most domestic service providers have established their own network management systems. These network management systems are separated from each other, leaving behind problems such as inaccessible management information and incompatible network management protocols. Therefore, a comprehensive network management system capable of supporting mixed network resource management, network operation monitoring, network optimization, and service scheduling in a mixed network environment is needed to improve the comprehensive utilization of network resources from the perspective of the entire network and strengthen the ability to maintain the entire network. To realize the comprehensive management of multi-professional networks, the data collected by each professional network management system must be integrated and adapted first, so building a universal interface adapter is the basis for building a comprehensive network management system.

General interface adapter overall plan

All test instruments are connected to the device under test through an interface adapter. When the object to be tested changes, you only need to switch the matrix switch and replace the corresponding conditioning module according to the signal characteristics of the port of the device under test, thereby greatly improving the system. Versatility and scalability. The interface adapter is mainly composed of a matrix switch, a digital signal conditioning module and an analog signal conditioning module. Its main function is to adjust various signals such as digital and analog to meet the requirements of test instruments, and also play a role in protecting the safety of the instrument. Its implementation block diagram is shown in the figure.

Interface adapter implementation block diagram

Universal Interface Adapter Internal Module

1) Matrix switch design

Schematic diagram of the mapping process from the port under test to the instrument port

The matrix switch is an important part of the interface adapter. It is responsible for controlling the flow of signals and is the key to achieving automatic testing and improving versatility. The figure shows the mapping process from the port under test to the instrument port, where A = (a ₁ , a ₂ , ..., an) is the port under test, and B = (b ₁ , b ₂ , ..., b _n ) is the port of the instrument. L is the mapping relationship between A and B, M is the mapping relationship between A and C, and N is the mapping relationship between C and B. It is not difficult to see from the figure that the key to the design of the matrix switch is the determination of the mapping relationship M and the mapping relationship N. If L is known, it is only necessary to obtain any mapping relationship of M or N to know another mapping relationship.

2) Analog signal conditioning module design

The main role of the analog signal conditioning module is to properly condition the analog signal so that its voltage range meets the input voltage requirements of the measuring instrument. AD827 is used in the conditioning circuit. The maximum bandwidth of this chip is 50MHz, and two op amps are integrated inside the chip, which are used for signal amplification, translation and attenuation. The analog signal conditioning circuit is shown in the figure.

Analog signal conditioning circuit

The left part of the picture is the first link, the input is V1, and the output is V2. Its role is to amplify the weak signal. The right half is the second link. This link is the signal attenuation link. Its maximum gain is 1. By adjusting the potentiometer, the minimum attenuation of the signal can be 0.

3) Digital number conditioning module design

The digital signal conditioning module uses SN74ABT16245 as the driving chip. The direction of the signal can be controlled by the switches K ₁ and K _2. If T / R ₁ and T / R ₂ are both high, the signal direction is A ₀ A ₁₅ to B ₀ B ₁₅ ; If T / R ₁ and T / R ₂ are both low level, the signal direction is B ₀ B ₁₅ to A ₀ A ₁₅ . The digital signal conditioning circuit is shown in the figure.

Digital signal conditioning circuit ^[1]