Motorola Solutions Inc. 89FC4825 Manuale Utente

 
Functional Description / Operation of Modules (Draft) 
 

The following table shows the specifications of MTR3000 Power Amplifier (PA). 

Specifications of Power Amplifier 
Parameter Specification 
Operational Frequency Range 

403–470 MHz (UHF R1) or 470–524 MHz (UHF R2) 

Minimum Input Return Loss (TX mode) 

7 dB 

Rated RF Output Power Range 

8–100 W 

Rated RF Input Power Range 

9.8–14 dBm 

28.6V Supply Nominal Voltage (AC Power) 

28.6V (+/- 4%) 

14.2V Supply Nominal Voltage 

14.2V (+/- 3%) 

28.6V Supply Maximum Current Draw 

12.6A 

14.2V Supply Maximum Current Draw 

2.0A 

Maximum Standby Power Consumption 

1.2 W 

 

Functional Theory of Operation 

The Power Amplifier (PA) is designed for continuous-duty operation across each specified band and power level.  

All PA contain a multi-stage power amplifier board at the input (RF Board), a circulator with isolation load 

termination, a low-pass filter/directional coupler at the output (Output Board), and a DC Distribution Board 

incorporating circuitry for diagnostics and RF power control.  The PA and its sub-circuits are broad-band devices 
and require no manual tuning or alignment to operate over the specified conditions. 

The main interface between the PA and the rest of the BR is through the DC Distribution Board.  The DC 

distribution board contains the PA external I/O’s that connects to the power supply directly through a cable and to 

the control module through a cable to the backplane.  These I/O’s are used to distribute the DC supply buses 

(28.6V and 14.2V nominal) from the power supply to within the PA as well as the various signals used for the 
control of the PA from the SCM such as the SPI bus signals, PA enable, and the reset line. 

The DC Distribution Board contains the SPI circuitry as well as metering circuitry used by both SW and internal PA 

HW for determining when fault conditions are present and take appropriate action when needed.  A brief 

description of the PA SPI devices is shown below: 

•  Customer Programmable Logic Device (CPLD): main PA SPI interface, with all other PA SPI devices 

connected through this device 

•  Non-Volatile Memory (NVM): used to store calibration data and identification information 

•  Digital to Analog Converter (DAC): converts SW digital signals to analog within the PA.  This controls the 

PA fan, power control circuit, and some other circuits within the PA 

•  Analog to Digital Converter (ADC): converts analog signals within the PA to digital for SW interface.  These 

signals are used by SW for HW metering 

A combination of software (SW) and hardware (HW) controls are used to regulate the PA RF output power level.  
By way of software control, the SCM programs RF output power through the SPI bus.  Once programmed, the PA 

power control loop will level the output power to the requested level, if possible.  The requested output power may 

not be achievable if an alarm condition is present, and output power may be reduced by way of SW or HW control 

if alarm conditions are present. 

Within the Base Station / Repeater (BR), the modulated RF signal passes from the Exciter Module to the driver 
amplifier within the PA.  The driver amplifier is located on the RF Board and is a multi-stage amplifier circuit that 

amplifies the RF input signal up to a maximum of approximately 4 W, as needed to achieve the software requested 

BR RF output power.  The RF signal from the driver amplifier is further amplified by the final amplifier stage, which 

is also located on the RF Board and consists of multiple paralleled RF devices with associated splitting and 

combining circuitry. 

This RF signal then passes through a circulator and harmonic (low pass) filter, through an RF directional coupler, 

and is output to the site transmit antenna port.  The circulator prevents a high Voltage Standing Wave Ratio 

(VSWR) at the PA output from damaging the final amplifier devices, and also improves intermodulation attenuation 

(IMA) performance by providing isolation to the final amplifier.  The harmonic filter attenuates the harmonic levels 

generated by the preceding RF amplifier devices. 

The RF directional coupler is a calibrated wattmeter, with its calibration information stored in the PA NVM.  The 

forward and reverse power wattmeter provides a signal corresponding to the measured output power to the ADC