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The remote village can’t receive the signal from town base station because of long distance. If we adopt the original signal frequency of 900MHz and 1800MHz, it’s easy to affect by the outside condition and the loss of wireless propagation path is biggish. Also the signal is easy to block off by the complicated Montana landform. So we need a system which uneasy to affect by outside condition and with powerful diffraction to transmit and cover, achieve large-scale wireless communication service to villages.
Direct against the above situation, the Enclave Companding System has researched. It compress the communication signal form wide bandwidth to narrowband via simulate channelized, band selective or digital channelized, then transmit the signal in long distance. The Enclave Companding System compress the donor signal from 24M bandwidth of 900M band to 4M bandwidth of 150M or 230M band, in remote expand the intermediate frequency to the original 900M band, then cover after linear amplification. The advanced compression and filtering technology debase the device interference to network system. Availably solve the signal coverage problem in hilly, mountainous and silvan areas, also in coverage areas with lean frequency resource.
Product Category: Simulate Companding Channelized Frequency Shifting Repeater, Simulate Companding Band Selective Frequency Shifting Repeater, Digital Companding Channelized Frequency Shifting Repeater.

Product Features：
☞Long distance transmission and complicated landform coverage with powerful penetrability and diffraction
☞Intermediate frequency can chose from 1500MHz to 250MHz,in 4~8MHZ uplink and downlink wideband, evade interferential frequency via choosing and shifting
☞Less interference to base station uplink, strong supportability of data service and less influence to E-GPRS downloading rate.
☞Support Multi-split pattern, and thinks to the small traffic in remote villages, the Multi-split pattern aim at the coverage of blink and weak area, reducing coverage cost
☞Flexible regulating and testing methods, support net opening, serial port and remote upgrad.

Technology Analysis:

1、Analysis of Enclave System Relay and Coverage Ability

    Enclave System uses VHF band of 150MHz to 230MHz, which compare to GSM900 or GSM1800 band, the radio wave diffraction much stronger, transmission loss much less, and more conformable for signal long distance transmission and coverage under special landform.

1.1    Diffraction Analysis:

The Electromagnetic Wave has the characteristic similar to optic wave, so for the large margin of power, even there has barrier in the way, it can also communicate via reflection wave or antenna side lobe in short distance transmission. But in long distance transmission, the way between transceiver antennae must be “line of sight out of barrier”.

The calculation formula of Fresnel radius is as follow:

R=0.5*(λ*D)*0.5

 — λ is wavelength，λ＝3×108 /f(meter)

—      D is the distance between two antennae.

Therefore, at mountainous area thus non-vision distance propagation environment with many obstacles, the Enclave System has stronger ability to conquer landform environment and transmit.

1.2    Space Transmission Loss Analysis

The signal transmission loss in free space is nearly relevant to signal frequency, the higher frequency, the greater unit distance loss. The signal loss in free space can be calculated by the formula as follow:

PL（dB） =32.45 + 20lgf + 20lgd

If the transmission distance is the same, the attenuation that 900MHz signal beyond 150MHz will be:

20(lg900-lg150) = 15.56dB

The attenuation beyond 230MHz will be：

20(lg900-lg230) = 11.85dB

Thereby, the loss of 900MHz signal in free space is 32 multiples of 150MHz signal, and 16 multiples of 150MHz signal. Other things being equal, the 150MHz/230MHz signal can transmit longer distance.

Typical Application：

The Villages’ Communication Project is mainly aim at the coverage of remote villages.