User's Manual

EMS Wireless Operator’s Manual
MirrorCell II CDM 812, CDM1912 Series
608112-1, Rev C
34
Figure 11: MirrorCell

II Internal View
The repeater is enclosed in an aluminum case with rear mounted cooling fins.
Aluminum offers a lightweight design with good heat conduction and weatherproof
protection. The housing conforms to the NEMA (weather-proof) standard. Per the
NEMA 4 specification, the enclosure will withstand 65 PSI (pounds per square inch)
pressure salt water spray on all four sides with no leakage to the inside.
The unit is cooled with electric fans that are cycled depending on the internal
temperature of the unit. Forced air from the fans is directed between cooling fins on
the rear of the cabinet, which enhances the MTBF by as much as 100%.
The transmit and receive antenna ports are standard N-type (DIN 7-16 optional)
located on the underside of the repeater.
7.2 Channelizer Module
The primary reference frequency for the MirrorCell

II repeater is provided by a 20
MHz temperature stabilized crystal oscillator. This basic reference frequency is used
by the PLL to generate the local oscillator (LO) frequency. The 20 MHz frequency
accuracy is 5 ppm. All internally generated frequencies are locked to this basic
oscillator. The same LO frequency is used for both the up converter and down
converter, ensuring no difference in the input and output frequencies.
The downlink and uplink paths in the channelizer module each consist of an LNA, a
down-converting mixer with a low side Local Oscillator that produces a 140 MHz
Intermediate Frequency (IF). Then, SAW (Surface Acoustic Wave) filters, an up-
converting mixer, and a post amplifier complete the circuit. The channelizer module
also includes power level control functionality. Note that the uplink path includes the
power amplifier in the Channelizer unit, while the downlink path has the power amplifier
external to the channelizer.
7.3 Downlink Power Amplifier
The downlink power amplifier may have output power levels as shown in Table 1. The
power amplifiers are designed to meet industry standards regarding Adjacent Channel
Power Ratio (ACPR) and spectral re-growth.