Diamond CD® The Harris® Diamond CD® solid-state transmitter with LDMOS technology delivers the highest-quality performance and UHF reliability for ATSC broadcasters. Each Diamond CD transmitter has a control cabinet and one to five power amplifier (PA) cabinets. The control cabinet houses the system controller, exciter, monitoring and control panel/graphical user interface (GUI), driver amplifier and an optional second exciter and driver with automatic changeover.
Features
Apex M2X™ multimedia exciter enables easy migration between standards Real-Time Adaptive Correction (RTAC™) provides continuous automatic correction and optimum performance Developed to deliver uncompromised signal quality for digital transmission Parallel operation of redundant components for reliability Compact footprint, with powerful configuration for flexible installation layouts Modular power supply for uninterrupted operation On-air servicing of PA modules, eliminating downtime Air-cooled amplifiers for easy installation and low maintenance costs Comprehensive factory support, extensive training, 24-hour technical assistance and parts
Powerful Performance The Diamond CD transmitter provides maximum performance and UHF reliability with an array of features and enhancements. With the dual exciter option, switching occurs after the driver amplifier stage, providing 100 percent power output if an exciter or driver amplifier fault occurs. Each power amplifier cabinet is a self-contained 7.25 kW average power RF amplifier with individual AC power feed, control circuits, interlocks, air cooling, RF amplifier modules and modular power supplies. This distributed architecture delivers system redundancy and enables easy system expansion to meet future broadcast needs. The power amplifier cabinet houses up to 16 parallel RF power amplifier (PA) modules and eight parallel power supplies—one for every two PA modules—to ensure minimal loss of output power if a PA module or power supply is removed from service. By preserving maximum RF power at all times, the broadcaster is protected from abrupt losses in coverage brought on by the “cliff effect.” Hotpluggable PA modules and on-air replaceable power supplies may be installed and removed from the transmitter without interrupting transmission for ease of maintenance and quick return to full power. Smart PA modules feature internal protection against high reflected power, over temperature, low gain and RF overdrive conditions. Each PA module also includes a microprocessor for control and diagnostics. As added protection, regulated power supplies are also internally fault protected.
Benefits Apex M2X Exciter The Diamond CD transmitter includes the Apex M2X exciter, which supports a range of analog, digital and mobile standards. This flexibility, coupled with the exclusive RTAC correction, provides superior performance today and can easily adapt to meet future broadcast needs. Cost-Effective, Maximum Efficiency The Diamond CD transmitter offers power efficiency, low operating costs and reduced cost of ownership over the life of the transmitter. Lightweight, Compact Footprint This compact transmitter has minimal space requirements to fit even the most crowded, shared transmitter site. Because of its compact size and light weight, the transmitter can be serviced without the need for a two-person lift and can be affordably shipped same day or overnight, for cost-efficient spares holding.
Straightforward Monitoring and Control Distributed control architecture delivers outstanding reliability, soft failure operation and simple serviceability. Improved Uptime With redundant power amplifier (PA) and universal power supply (PS) modules, on-air servicing is quick and easy—without any broadcast interruption.
Diamond CD Details Control Cabinet
Solid-State Amplification
The control cabinet houses the system controller, monitoring and control panel, exciter, driver amplifiers and an optional second exciter with automatic changeover. It also controls electronic RF phase and gain balancing used in multiple amplifier cabinet configurations. Serial RS-232 and standard, parallel remote control interfaces are also included.
Featuring the latest LDMOS power transistor technology, the rugged RF amplifiers offer high efficiency and high gain and exhibit excellent thermal characteristics. Linearity and IMD performance is improved compared to older bipolar designs. Unlike tube amplifiers, solid-state devices have no wear-out mechanism.
Graphical User Interface
Compact, modular, regulated power supplies can be removed while the transmitter is on air. Power supplies are protected from incoming AC line transients, over current and over voltage. Up to eight power supplies for each PA cabinet minimize output power loss, resulting in minimal loss of viewers due to the cliff effect.
An eye-level interface presents easy-to-understand transmitter status information, with signal flow diagrams and analog bar-graph metering. Power Amplifier (PA) Cabinet
When fully populated with 16 power amplifier (PA) modules, each cabinet is a self-contained RF power amplifier with AC power feed, control circuits, interlocks, air cooling, RF amplifiers and power supplies. Apex Exciter
Third-generation Harris 8-VSB exciter with patented technologies to generate an RF signal of integrity and linearity.
Power Supplies
Cooling
Air cooling provided by internal and external fans. With the internal fan, air enters through filters in the rear door of each PA cabinet and is circulated by a direct-drive fan. Air is exhausted from the top of the cabinet. An optional, external fan works to isolate transmitter cooling air from building air.
Power Amplifiers
All PA modules are identical and interchangeable. Each hot-pluggable module features a high-speed DC switch that disables the module if a fault occurs or if the module is removed from the transmitter. Modules are protected against high reflected power, over temperature, low gain and RF overdrive. Fault status and metering are displayed on the main control panel.
Harris Apex M2X Exciter — The Heart of the Transmitter The Diamond CD transmitter features the third-generation Apex exciter, the ATSC 8-VSB. Building on well-proven Apex capabilities, the ATSC-8 features enhance performance and maximize signal coverage, ease of operation and compatibility with other equipment. The ATSC 8-VSB offers RTAC, which corrects frequency response distortions in the power amplifier and the high-power bandpass filter that affect coverage area, error vector magnitude (EVM) and signal-to-noise ratio. RTAC delivers consistent coverage by keeping the EVM low and the signal-to-noise ratio high. The RTAC works adaptively—without training signals—to optimize performance continuously, over time and variations in temperature. Using a patented modulation technique, the Apex generates DTV signal integrity, and offers multiple levels of linear and non-linear correction for exceptional in-channel performance. Optional Upgrade for IP The optional Harris eCDi® enhanced network monitoring and control package seamlessly integrates the transmitter and exciter with an IP network. eCDi provides full monitoring and control of all transmitter functions, including power amplifier status, output monitoring, control system diagnostics, and RTAC control and monitoring for digital television transmitters. In addition to transmitter-level information, eCDi accesses Apex exciter data, does a signal analysis and displays it on a web-enabled PC in any remote location in compliance with the station’s network security and access policies.
RTAC Explained With RTAC advanced digital precorrection, the Apex M2X is able to fully use the transmitter power amplifier while maintaining spectral mask compliance of the digital signal.
0 -10 -20
Precorrection can be implemented various ways, which are listed below in order of sophistication:
Analog fixed precorrection Digital fixed precorrection Digital adaptive precorrection Digital, memoryful, adaptive precorrection (RTAC)
There are two types of precorrection used by the the Apex M2X: linear and nonlinear.
-30 -40 dB
-50 -60 -70
uncorrected
-80
corrected
-90 -100
MHz
Linear Precorrection Linear precorrection corrects for the non-ideal amplitude response and time response of the transmission system, including the power amplifier and any bandpass filters. Linear precorrection helps optimize the modulation performance of the transmitted digital signal so less equalization is required at the receiver. Nonlinear Precorrection Nonlinear precorrection corrects for the two major types of nonlinearity (AM to AM and AM to PM) in the RF power amplifier that cause unwanted spectral components and poor RF mask compliance. With AM to AM nonlinearity, the RF power amplifier output amplitude does not exactly track the input amplitude. This nonlinearity occurs typically near the peak output power of the amplifier where saturation effects cause the output response to flatten as the input continues to increase and the amplifier output goes to zero. With AM to PM nonlinearity, the RF power amplifier output phase does not track the input phase. The amplifier acts like a phase modulator as the power output varies to follow the input signal, producing undesirable sidebands.
Fixed vs. Adaptive Fixed precorrection can improve the system linearity for one specific operating point, but has to be manually readjusted for changes in power output, antenna load impedance, temperature or operating point. Adaptive digital precorrection uses an RF sample taken at the output of the RF amplifier and automatically adjusts the shape of the precorrection, continuously optimizing the linearization of the system. The bandwidth limitation, especially in tube type amplifiers (IOT) and the stored energy in tuned circuits introduce “memory effects.” Digital, Adaptive, Memoryful Precorrection Digital, adaptive, memoryful precorrection can correct for these memory effects and for simple AM to AM and AM to PM distortions. Even wideband solid-state RF amplifiers have memory effects that change the shape of the nonlinearities with digital modulation data states. RTAC is the only system with simultaneous, linear and nonlinear, adaptive, memoryful precorrection, providing total correction to all types of RF amplifiers.
Diamond CD Block Diagram Control Cabinet
CD 1A Exciter
Driver
MULTI-CABINET SPLITTER
DD-1 SMPTE-310M Exciter Select CD 1A Exciter
Driver DD-1
SMPTE-310M
Control
Meters
Remote
PA Cabinet
PA
Solid State Amplifiers
PA PA
MULTI-CABINET SPLITTER
PA PA PA PA
Filter
PA PA PA PA PA PA PA PA PA PSU 1
THRU
PSU 8