User's Manual

EMS Wireless Operator’s Manual

MirrorCell II CDM 812, CDM1912 Series

608112-1, Rev C

For indoor installations, achieving adequate isolation is still important, but somewhat

easier to achieve. This is because the donor and server antennas are physically

separated by the building material, which is normally quite lossy to RF. This is

especially true if the donor antenna is placed on a building roof that has a metallic

layer. In most of these installations, inexpensive yagi donor antennas can be used.

The server antenna(s) are frequently ceiling mount designs with most of the radiation

directed down toward the building floor. This further enhances the isolation.

3.3 Antenna Mounting and Isolation Measurements

Use the following steps to mount the donor antenna.

1. Mount donor antenna at the initial desired location. A visual line of sight path to

the BTS is critical for a strong, stable donor signal that is a constant level over a

long period of time.

2. Measure the received signal strength from the donor site. The amount of power

the repeater can produce is dependent on this signal level.

3. If greater signal strength is needed, try raising the donor antenna’s height, or

use a higher gain antenna, if possible.

4. Measure the RF channel strength received at the donor antenna and verify that

the proper base station sector is being received. The RF channel of the desired

base station should be at least 15dB higher than any of the other received RF

carriers. This can be measured using a spectrum analyzer. If necessary, the

donor antenna should be oriented until the desired RF channels are 15dB greater

than any others received. If this cannot be achieved, use an antenna with higher

gain. This means the antenna beamwidth is narrower, which requires greater

precision to physically orient the antenna toward the donor site. But, the donor

signal will be higher, and the antenna will be more effective rejecting unwanted

signals.

Then, isolation measurements should be made to ensure proper operation of the

repeater. Isolation measurement can be accomplished easily by following the

procedure outlined below, as illustrated in Figure 5.