Advantages

The sensor has been developed on the above integrated scheme and offers many advantages.

• Modular and scalable

• High operational life

• Graceful degradation

• Compact form factor

• Absence of high voltage

• No requirement of vacuum

Brief Technical Specifications of RF amplifier modules

• Operating Frequency: 325 to 650 MHz (tunable at single frequency)

• Bandwidth (1 dB): ±2 MHz

• Power Rating: 500 W X 4 (CW Power) or 1.5 kW X 2 (pulse width ≤ 1ms)

• Input VSWR: ≤ 1.25

• Output VSWR handling: ≤ 1.4:1

• Gain: ≥ 18 dB

• Efficiency: ≥ 55 %

• Harmonics: better than -30 dBc

• Spurious better than -50 dBc (within 2 GHz frequency span)

• Power requirement: 48-52 V (DC), 20 A max.

• Cooling Requirement: Water cooling (~ 5 kgf/cm^2, 8 liter per minute)

• Interface Connections: 50 Ω, N-type receptacle for both input and output

Introduction:

The radio frequency power amplifier (PA) modules are key component in various commercial and industrial applications. Unparalleled advantages of solid-state technology have made transistor-based RF amplifier a promising candidate. Such transistor with moderate continuous wave (CW) power level (~ 100-800 W), appropriately designed with the impedance matching networks and bias circuits, takes the form of a power amplifier module. For achieving hundreds of kW of RF power, multiple power amplifier modules are suitably arranged in multi-stage divide and combine architecture, along with power combiners, dividers and directional couplers. The potential advantages claimed for high-power solid-state amplifiers are its long failure-free life, low bias voltage, no risk of X-rays and electric shock, graceful degradation and low projected volume-production costs.

Majority of the PA design related literature with waveform shaping is available for low power (< 100 W), as its research community is driven by requirement of communication sector. The cellular phones and base stations, require an average RF power of less than 100 W. For this power level, the wave shaping of the voltage waveform at the terminals of the transistor is possible by selecting a device, having voltage/current rating higher than the actual requirement. When higher power designs are planned, the optimum calculated values of voltage/current often exceed the maximum rating of the transistor. For particle accelerators, the required RF signal is mostly monotonic/pulse in nature but RF power requirement is very high (~ > 100 kW) among all applications. Additionally, the large output parasitic of the ubiquitous LDMOS transistor (for UHF band), presents performance related issues unless they are suitably absorbed in impedance matching circuit.

Hence, one needs to explore suitable augmentation to newer concept of harmonic tuned design space, so as to apply it for higher power designs. For present modules, novel variants viz. the Continuous Class J and Extended continuous Class F mode amplifier in 500 W CW and 1.5 kW pulse power regimes are physically demonstrated in UHF band. Here, unlike the conventional modes with shorted harmonics at the output, the output voltage waveform of the PA is engineered and optimized by selecting a set of harmonic terminations, for the given bias and input drive conditions. The developed PA modules at 325 MHz, 505.8 MHz and 650 MHz are shown in Fig. 1. These PA modules are designed in such a way that in CW mode four standalone gain blocks, can simultaneously operate with a common water-cooled cold plate. In pulse mode two gain blocks re combined so that effectively amplification is performed by two gain modules with a common water-cooled cold plate.
             

Brief Technical Specifications of RF amplifier modules

•    Item Type: Tuned RF amplifier
•    Operating Frequency: 325 to 650 MHz (tunable at single frequency)
•    Bandwidth (1 dB):  ±2 MHz
•    Power Rating: 500 W X 4 (CW Power) or 1.5 kW X 2 (pulse width ≤ 1ms)
•    Input VSWR: ≤ 1.25
•    Output VSWR handling: ≤ 1.4:1
•    Gain: ≥ 18 dB
•    Efficiency: ≥ 55 %
•    Harmonics: better than -30 dBc
•    Spurious better than -50 dBc (within 2 GHz frequency span)
•    Power requirement: 48-52 V (DC), 20 A max.
•    Module Packaging: 500W X4 (CW Power) or 1.5kWX2 (Pulse Power)
•    Cooling Requirement: Water cooling (~ 5 kgf/cm2, 8 liter per minute)
•    Interface Connections: 50 Ω, N-type receptacle for both input and output
•    Physical dimensions: 200 mm x 200 mm X 100 mm (length X width X height) for a module of 4 x 500 W CW amplifiers.
•    Gross Weight: ≤ 10 Kg

Typical End Users

It is a thru-line dual channel sensor thus it can be used for measuring RF power while system is working (without terminating) and monitoring line or load condition in various RF systems used for strategic applications. For example, application in solid-state high-power amplifier systems can be quoted, where a huge requirement exists for accurate and reliable measurement of forward as well as reflected powers of the amplifier modules. It is also required for cellular base stations, military radar communications, global positioning systems.

Facilities Required for Commercial Production

Assembly and Inspection:

•    Electronic Board Inspection Setup
•    Electronics Testing
•    Final Assembly Setup

RF Measurement and Testing Facility:

•    RF Generator
•    Driver Amplifier
•    RF Power Sensors and Meters
•    Programmable DC Power Supply
•    Vector sensor or Phase detector for gain and insertion phase measurement
•    Re-circulating Water Chiller
•    RF Load, Cables, Adopters and other RF accessories

Optional Facilities (may be outsourced /shared)

Fabrication Facility for Amplifiers:
•    PCB Fabrication
•    SMD Board Population/Soldering
•    CNC Machining (VMC or equivalent)

Manpower Requirement

Sr.      Designation                                                                                                                Nos.
1         Technical officer (B Tech in Electronics Engg)                                            1
2        Technical Supervisor (Diploma in Electrical/Electronic Engg.)          1
3        Operators/Technician   (ITI)                                                                                    2