Introduction to Modern Communication System and DSP Experiment Platform

1 Introduction

In recent years, communication electronics and computer technology have developed rapidly, and have been constantly innovating. In particular, radio communication technology has developed rapidly in recent years. In response to the ever-changing new technologies, the theoretical courses and teaching methods of communication majors in colleges and universities also need to be constantly updated to keep up with the requirements of the times. Therefore, the corresponding communication experiment courses and experimental equipment also need to be updated and developed accordingly, so that students can master the latest technologies in the field of communication electronics through practical training and cultivate corresponding practical skills.

At present, the communication principle experimental devices used by many colleges and universities in China are of outdated design technology, and the experimental content does not combine the current advanced communication technology. In view of this situation, we have developed the "JLC type modern communication system principle technology and DSP comprehensive experimental development system" based on software radio technology, which is currently the most advanced in China. It is suitable for communication and electronic technology experiments in colleges and universities, and can also be used as a software and hardware development platform for communication electronic products.

2 System Functions

Compared with the traditional communication principle experimental system, the biggest feature of this experimental development system is the advanced technology of its implementation - the use of DSP technology and FPGA/CPLDD technology. The system is based on DSP chips (CPU) and FPGA ultra-large-scale programmable chips as the core of the basic hardware platform, and a series of DSP system experiments and modern communication system principle and technology experiments are completed through DSP software programming loading. Therefore, the experimental development system has an open architecture, and this openness includes three aspects, namely, openness to user use, openness to production, and openness to research and development. On this general hardware platform, different experimental contents can be downloaded according to the needs of different levels such as graduate students, undergraduates, junior college students or technical secondary school students, and users can also design experimental projects by themselves. The system function block diagram is shown in Figure 1. The system function module is mainly composed of 9 parts, which can complete a series of experiments on the principles and technologies of modern analog communication systems and modern digital communication systems and a series of DSP system experiments, and DSP application system solutions can also be developed on this platform.

The series of typical experiments of DSP system and typical experiments of communication system principle and technology developed by this system are as follows:

I/O experiments;

A/D interface experiment;

D/A interface experiment;

External interrupt system experiment;

Software interrupt experiment;

Timer experiment;

Serial port interrupt experiment;

Host interface experiment;

Sine signal generation experiment;

White noise generation experiment;

FIR filter experiments;

IIR filter experiments;

Signal synthesis experiments;

DSP serial communication system experiment;

DSP parallel communication system experiment;

Frequency hopping communication control system experiment;

Amplification and attenuation;

FFT;

Error correction coding technology;

Synchronous technology;

AM communication systems;

FM communication systems;

Phase modulation communication system;

Digital baseband communication systems;

PCM communication system;

ASK communication system;

FSK communication system;

PSK communication system;

Comprehensive experiment of simulated communication system;

Comprehensive experiment of digital communication system.

3. Software and Hardware Design

3.1 Hardware Design

The block diagram of the system hardware circuit is shown in Figure 2. The hardware platform adopts modular functional design to facilitate debugging and measurement. The DSP device uses the TMS320VC5402 chip of TI (Texas Instruments); the input and output channel design of the experimental platform uses the TLV320AICl0 chip of TI to complete the A/D and D/A conversion circuit functions, and communicates with the DSP's high-speed multi-channel buffered serial port McBSP for serial full-duplex communication. TLV320AICl0 integrates audio sampling, anti-aliasing filtering and audio output circuits on one chip. It is a better device for completing language signal input and output processing; the DSP chip and peripheral circuits use 3.3V and 5V mixed logic design; the bit synchronization module, correlator module, synchronous decoding module, etc. in the communication subsystem are implemented by FPGA devices, using ALTERA's EPFl0K30A-208PQFP device; the DSP and FPGA are connected through the DSP local bus definition; the communication between the DSP and the AT89C51 microcontroller is carried out through the HPI interface of the DSP, and the microcontroller and the PC perform asynchronous serial communication.

3.2 Software Design

According to the above system functions and hardware structure, the software design of this system is mainly divided into three parts, namely, the system main control module including the self-test module, 30 system experimental function realization modules and keyboard LCD display module. Modular design is adopted in software design. The system main control module manages and calls each software module, and each part communicates according to a custom communication protocol. The application program is written in three different methods. The system main control module is written in C language, and other application program modules are implemented in C language, assembly language or C language and assembly language mixed programming methods to achieve the best utilization of TMS320VC5402DSP chip software and hardware resources. The main program block diagram of the system is shown in Figure 3.

4 Conclusion

The designed modern communication system principle technology and DSP experimental platform is highly practical, advanced, open and flexible, and has been successfully applied in the teaching and scientific research of many units. The usage shows that its performance is stable and reliable.