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(Source: Motorola, author unknown)

Paging Base Station Description

Motorola recognizes the many challenges facing our customers. Things like . . . System capacity . . . New Market Applications . . . Increasing Competition . . . Regulatory Uncertainties. It helps to simplify where you can. That is where Nucleus comes in. Nucleus provides BEST IN CLASS solutions to important issues including site costs, power sources, flexibility for the future, and east of maintenance and installation.

Here is a look at Nucleus' revolutionary features. These features can give your paging system a competitive advantage today . . . and tomorrow.


Size is only the beginning . . .

The size and weight of the Nucleus base station have been dramatically reduced. The new configuration has yielded size and weight reductions of up to 70% over the PURC 5000 product platform. The High Power Nucleus Station is 14" tall and weighs 105 pounds in a rack-mount configuration. The Standard Power model is 8.75" tall and weighs 60 pounds. The smaller size has many benefits including ease of maintenance, potentially cheaper site rental costs, and ease of stacking multiple stations.

Modular Construction
The construction of the Motorola Nucleus paging base station is modular. The control housing is a 5-rack unit high card cage made of welded sheet metal. The modules plug into a backplane-interconnect board that not only routes the signals between modules, but also provides connections external to the station. The interconnect board shielding provides added protection against RF signals. The use of gold card-edge connectors is to ensure reliable connectivity between the modules and the backplane.

The separation of functions is on a per module basis. The functional module units include the Power Amplifier, Exciter, Power Supply, Station Control, Reference modules. The figure below shows modular construction for the Standard Power unit.

nucleus front photo

The modular construction facilitates two key features.

First, the concept of a building block product. The building block concept allows the customer to expand or upgrade his current system easily. Many common modules are used throughout the product line, regardless of power level and band. The building block approach reduces the number of different spare parts required to maintain a system.

The second key feature provided by the building block approach is FRU or Field Replaceable Unit diagnostics. In the Nucleus, functionality is captured in each of the separate modules. If a failure occurs in the base station, FRU diagnostics identify the failed module by displaying a red colored LED on the front of the module. This allows a technician to quickly identify the problem, replace the module with a

working unit, and take the failed unit to a service shop for repair. FRU failure indications are also available remotely. This allows the technician to bring the proper replacement module to the site. FRU provides a fast, easy method for failure identification and repair.

nucleus modules

The following describes the parameters, alarms, and configuration settings for the base station:


The operator determines the thresholds for many of these alarms remotely from a VDT or locally at the station's front panel.

The following paragraphs provide a functional description of each module:

A. Station Control
The user interface to the base station is through the station control module. The user interfaces to the station control module either remotely from a VT100 compatible video display terminal (VDT) or locally at the base station through a front panel display and keypad. On the front panel of the station control module, the existence of an 8 character alphanumeric display and push button keypad facilitate interaction with the user. The user may display, enter or modify parameters from the front panel. For security purposes, the front panel is password-protected and is can be changed by the user at any time.

When Nucleus is connected to a Public Switched Telephone Network (PSTN) modem, the user will be able to access Nucleus remotely. Nucleus will communicate using ASCII protocol that allows any VT-100 compatible VDT with a PSTN modem to access the station control. From the remote VDT, the user will be able to perform all functions that are available from the local front panel. The same PSTN modem can be used to facilitate communications and control with the Control Point equipment. This means fewer costly site visits are required. Also, when a site visit is needed the user is better equipped to perform the required actions and spends less time at the site.

The station control also contains the program software. Through advanced technology and processors, the station control can have its program software upgraded via the distribution link or the PSTN modem. This software downloading process will insure that the Nucleus base station will never become obsolete.

The functions within the station control module are user friendly and increase the flexibility of the base station. These features provide a station that is easy to operate and quick to install and diagnose.

The Station Control is configured in one of the following ways:

A. A Station Control Module and a Wildcard I/O Board, or

B. A Nucleus Advanced Control (NAC) Board and a Wildcard I/O Board,


C. A Station Control Module and a C-NET Network Interface Unit (NIU)

The station control board is responsible for the internal diagnostics, maintenance and alignment functions. Each module in the base station contains digital logic that communicates, via the internal SPI bus, with the station control module to report status. The station control module uses this logic to adjust the operation and performance of each module. Some of the parameters that the station control module can adjust electronically include transmitter power output, carrier frequency offset, deviation offsets, transmit frequency, maximum transmit deviation and several alarm thresholds. For maintenance and diagnostic purposes the station control module not only receives alarm indications, but also test point voltages, temperature and power output indications.

The Wildcard I/O Board serves as the interface between the external control equipment and the base station (for example, an external NIU).

The Wildcard I/O Board contains SPI interface circuitry to control the eight outputs, eight inputs, and alarm relay. The eight outputs are open-collector inputs to indicate station alarms. The eight inputs may be used to monitor external site equipment. The inputs are TTL-compatible signals with internal pull-ups to +5 V.

The Nucleus Advanced Control (NAC) is to provide all the features of the current ACB product. This control scheme is used with the Advanced Simulcast Controller (ASC) and is compatible with all of the different control paths (wireline, RF link, and satellite link). The NAC will support 2-level modulation. Therefore, acceptable paging formats are 512/1200/2400 POCSAG. Golay, Tone, Voice and 1600 FLEX™. Additionally, NAC will support Tone Remote Control, Digital Remote Control 1 & 2, Key on Data, Local Control, and Direct Digital. The standard alarm reporting includes: polled diagnostics, unsolicited alarms, ASCII diagnostics, auto delay equalization, RF power measurements, wildcard inputs and outputs, alarm relay, and verification tone.

For high data speed and digital transmission, the C-Net Network Interface Unit (NIU) and the SCM combined provide the proper control. Basically, the C-Net Controller takes information from the Terminals and decodes it into a digital format (the C-Net data stream) for high speed transmission. Also embedded into the data stream is the system timing. The NIU, located next to the Station Control Board in the base station, receives the C-Net data stream via the link (compatible with wireline, RF, and satellite link distribution), and decodes it into the original data. The data consists of the paging data itself and what time the paging data will be transmitted. This technique is called "Store and Forward" and it allows for accurate simulcasting performance as well as jitter-free pages. C-Net allows simulcasting to be achieved via the three synchronization methods: Monitor, Direct Sync., and GPS. Diagnostics are done through PSTN. When phone lines are not available, over the air reporting to centralized monitor sites can be achieved. One of the more attractive features of C-Net is the Software Downloading capability. That is, C-Net has the capability to simultaneously reprogram all NIUs on a network via the link system. This feature provides a convenient, rapid software updating and ensures that all sites are always operating with the same software version. Future features can be implemented in a matter of minutes without costly site visits.

B. Reference Module
The reference module uses 2 slots that contain either the high stability oscillator (HSO) or the ultra high stability oscillator (UHSO). The HSO/UHSO provides a reference for carrier frequency generation in the Exciter and a clock reference in the station control module. The reference is a 5-MHz signal that goes to the station control module and the Exciter through the backplane.

The GPS receiver is built into the reference module of the station when used. The GPS provides a timing reference (1 PPS) and universal time for base station synchronization. The Global Positioning System (GPS) provides a viable source of Universal Coordinated Time (UCT) and synchronization timing.

The Motorola GPS Receiver is a 6-channel simultaneous tracking receiver that provides a timing pulse once per second in an RS232C interface format. The receiver also outputs real time at an RS232C interface to the station control module. The receiver mounts within the reference module enclosure to receive input power and improve RF immunity.

The antenna is an active microstrip patch powered by the GPS receiver. The antenna housing is a ray dome package that has dimensions of 3.9" (99 mm) diameter x 1" (25 mm) high and weighs just 7.3 ounces (210 grams). The design does not require tower mounting. Motorola has also specially designed its GPS receiver to operate in hostile RF environments and over a wide temperature range from -30° C to +60° C.

C. Exciter Module
The Exciter module is a microprocessor-controlled module that generates a modulated RF signal at the desired transmit frequency and sends this signal to the PA for amplification.

The Exciter module, occupies 1 slot, contains the transmit voltage controlled oscillator (VCO), the transmit carrier frequency synthesizer, the digital modulator and the power control. The design of the frequency synthesizer allows for broadband operation with the capability of synthesizing at least 32 frequencies. Since synthesis of the carrier is direct, sideband noise and harmonics are better than -90 dB below the carrier.

A 6811 microprocessor is in the Exciter to control thermal derating of output power, low battery derating, synthesizer loop leveling and loading, fan control, high VSWR protection, diagnostics and digital modulation. The digital modulation and output power adjustments are electronic and done separately for each channel to improve performance and eliminate adjustments for service and factory test. The PA heat sink contains temperature sensing devices that the microprocessor in the Exciter monitors. The microprocessor uses this information to signal the fans to turn on for cooling of the Power Amplifier and maintain the operating temperature at an optimum level.

The station's digital modulator is built into the design of the Exciter module. The modulator is capable of 2 or 4-level FSK modulation at data rates up to 6400 bps. The 6811 microprocessor generates exact digital deviations to enhance the simulcast performance and reduce variation between stations. Through the use of this special modulator, the Nucleus station is equipped to handle POCSAG, Golay, FLEX™, ERMES and future paging protocols.

D. Power Amplifier
The Nucleus PA has a new, smaller, state-of-the-art cooling design. The high gain dual device modules help achieve high gain with fewer parts. The new surface mount RF devices and the graphite heatsinks help cool the PA faster. Also, the front-to-back cooling design makes it easier to stack several stations into a single cabinet.

The power amplifier module contains the intermediate power amplifier (IPA), final amplifier module, harmonic filter, single stage isolator, and directional couplers for power control and diagnostics. The Power Amplifier in the Standard Power Station occupies 3 slots in the card cage.

The low-level modulated RF signal from the Exciter Module is input to the Intermediate Power Amplifier (IPA) in the PA. After amplification to approximately 0-10 W (depending on power control voltage from Exciter Module), the signal is fed to either a Driver (25W PA models) or a Final (125 W PA models). The gain of the IPA stage is controlled by the power control voltage from the Exciter Module. The smart power control protects the power amplifier by making sure that the station is always transmitting at the proper output level. Smart power control provides enhanced diagnostics, increased dynamic range and eliminates the need for mechanical tuning.

The modulated RF signal is amplified by the Driver/Final and is output to the site transmit antenna via a circulator and a harmonic filter/coupler. The coupler consists of a calibrated wattmeter which feeds a dc voltage proportional to the output power to the TX Power Control Circuitry in the Exciter Module to serve as the feedback signal in the power control loop.

The power amplifier module is laser tuned in the factory to prevent the need for adjustments during installation. Electronic power leveling adjustments made from the station control module provide an RF output that is continuously adjustable from 25 to 125 watts. Advanced heat sinks and cooling techniques allow continuous duty operation from -30° C to +60° C. The power control and protection circuitry provide automatic power cutback when encountering faulty or extreme temperature conditions. The power cutback is a gradual derating until reaching the 3 dB or half power point. The power amplifier also has a built-in single stage circulator to protect the transmitter from potential interfering signals at radio sites. The power amplifier design is extremely reliable even under demanding environmental conditions. The design minimizes servicing and down time.

E. Power Supply
The Nucleus station has several Power Supply alternatives using a switching power supply design. This new design provides greater flexibility for the customers' power source conditions worldwide. One alternative is an AC Power Supply module that operates from 90-280 VAC and from 47-63 Hz without jumper changes or modifications. This comes with a battery revert option as well. Another alternative is a DC power supply module that operates in 24VDC systems (21-30VDC) or 48V/60VDC systems (38-72VDC). All power supply alternatives generate 5V, 14V, and 28V dc operating voltages to power the station modules.

The front panel of the power supply includes an on/off switch and two LED indicator lights. The first indicator light is red and labeled "Module Fail." This light is an indication that the power supply module is not providing output power, but input power is present. The second indicator light is green in color and labeled "AC On," will turn off when the input voltage has dropped too low. In AC battery backed up stations, this would indicate that the station is in the battery revert mode. In DC only stations, this means that the site charger has failed and that the battery voltage is at insufficiently low level.

The supply design meets the most stringent safety requirements worldwide. The power supply has received or applied for many safety approvals worldwide.

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