Preface

With our society becoming increasingly dependent on computers and the Internet, more and more government, military, public security and financial organizations as well as individuals feel the need of accessing the Internet or private network through wireless channel. High-speed and high-capacity wireless communication is the best solution for areas where it is difficult to bury cables, or when there is an emergent need for communication.         This need is more evident with military unit and public security department that often need to transmit voice, data and live pictures in their work. So, devices and equipments capable of providing high-speed, mobile, secure and organized communication can be a great help for them.

Overview

The UHF Broad Band Data Radio (UBBDR) employs techniques such as DS-SS, digital modulation/demodulation, RAKE receiving and data encryption, featuring high security level and strong anti-jamming capability. Embed-in wireless packet network protocol enables self-organized communication for mobile users. The interfaces on the unit include RS232 and RJ45, supporting digital voice, static picture and video-frequency picture transmission. The friendly man-machine interface makes it easy to use. The modularized design simplifies the repair and upgrade.

System Architecture 

The UBBDR consists of the following modules: transmitter, receiver, frequency source, radio power amplifier, base band processing, network protocol processing and display. See Fig.1. 

                  Fig.1 System architecture

Note:

The big arrows stand for data channels and the small ones stand for control channels.

The protocol processing modules is the main control module of the unit, responsible for protocol processing, data processing, status control etc. The software also designed in modularized structure, making it easy to change a particular feature by upgrading the corresponding module.

Base band processing module receives instructions from the protocol-processing module, directly controls the operation of the transmitter and the receiver. The data to be transmitted will go through error correction coding, differential coding, spectrum spreading, frequency filtering
before being outputted as a 70MHz IF signal. The incoming signal will go through an inverse
process before being restored to the base band signal and preceded to the protocol-processing module.

In order to suppress the image interference, the transmitter adopted three-stage frequency conversion scheme in its design. It converses the 70MHz signal to 225-450MHz, avoiding the interference frequencies.

At the beginning portion of the transmitter, there is a multi-stage, high-gain and low-noise amplifier whose gain is 55dB and the noise coefficient if less than 2.7 dB, making it possible to keep the overall noise at a low level. The AGC technique is used in its IF and RF circuit
design to accommodate the broad dynamic range. The dynamic range of AGC is 80 dB.

The linearization technique is used in the RF amplifier design to assure that the amplifier
always works in linear section. As a result, the amplified signal has the minimum of distortion and group latency, the amplitude-phase response line is roughly flat.

The frequency source is excellent in terms of phase deviation and noise level, satisfying
the need of digital modulation.   

 Specifications  

l        Frequency Range: 225MHz—450MHz

l        Channel Spacing:      6.0 MHz

l       Number of Channels: 35 

l       Channel Step Size: 625KHz

l       Modulation: BPSK, QPSK

l       Transmitting IF: 70Mhz

l       Receiving IF:      30 KHz

l        Image Rejection：     ≥60dB

l       IF Rejection ≥60dB

l        Frequency Stability:   2´10^-6

l       RF Power: 20W±1.5dB

l       Sensitivity: -90dBm(Pe≤1´10^-6 error corrected)

l       AGC Dynamic Range: ≥80dB

l        ECR:   Pe≤1´10^-4   (No error correction)

l       Data Rate:  64-288 Kbps

l        Error Correction: RS coding, Data rate variable

l       RF Impedance:   50Ω

l        Power Supply: +28V/5A

Communication Mode  

Point-to-point communication

When radio sets are not organized, any two of them can communication with each other. The communication terminal can either send or receive data through RS232 or RJ45 interface. The highest possible data rate for RS232 and RJ45 are 115Kbps and 10Mbps respectively. See Fig.2.

Fig. 2 Point-to-Point Communication

Organized communication

With the embedded networking protocol, customer can group all radio sets into certain sub networks and form an integral network. See Fig.3 bellow.

Fig.3    Organized communication

 Relayed communication

When some radio sets in a network cannot directly communicate with each others due to blocked path or long distance, other radio sets can relay signal for them. Signal is allowed to be relayed by up to three radio sets before reaching its destination. See Fig.4.

Fig.4 Relayed Communication

Typical Application

Backbone radio network for division and brigade

Fig.5 Typical application 1

Wireless monitoring

Fig.6 Typical application 2