SITIS Archives - Topic Details
Program:  SBIR
Topic Num:  N07-007 (Navy)
Title:  Solid-State High-Efficiency Radar Transmit Module
Research & Technical Areas:  Air Platform, Electronics, Battlespace

Acquisition Program:  
 RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is “ITAR Restricted”. The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the “Permanent Resident Card”, or are designated as “Protected Individuals” as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.
  Objective:  Develop innovative technology with a solid-state high module (or building block) power output that has the necessary characteristics to operate in a Class E or F radar transmit module.
  Description:  The efficiency of current radar transmitters for airborne surveillance systems is in the 20 percent to 30 percent range. The remaining 70 percent to 80 percent of the electrical energy that is generated to drive these devices must be removed as heat energy. The weight and fuel consumption associated with the generation of this unused electrical energy, and its removal as heat energy results in increased airborne system costs and/or reduced aircraft performance. These impacts are exacerbated by the reduced size and increased altitudes associated with high-altitude, long-endurance unmanned air vehicles (UAVs), where propulsion and power generation are principal cost drivers. Further, the increased demand for greater surveillance capability in the form of long-range detection of low-observable air targets continues to drive power requirements to higher and higher levels. The conventional approach to achieving kilowatts of peak power is to combine lower power devices, typically in a parallel corporate feed, to achieve the desired transmit power levels. There is a significant penalty associated with configurations of this nature, due to the RF losses inherent with the combining networks. The higher power requirements necessitate more combining networks with commensurately higher power losses. One approaches a point where the dissipation in the combining networks must be addressed as part of the overall system thermal design, impacting the capacity of the cooling system. Consequently, a comprehensive approach to both improving high-power amplifier efficiency, and developing the highest module (or building block) power output is required to reduce the number of combining networks required to achieve the ultimate transmitter peak power. The silicon bipolar devices that have been the mainstay for high-power short-pulse amplifiers do not possess the characteristics for use in Class E or F high-power amplifiers (HPAs). Whereas, these high-voltage lateral diffused metal oxide semiconductors (LDMOS) are improving, their high capacitance limits their performance in a switched mode Class E amplifier. Silicon carbide (SiC) and Gallium Nitride (GaN) devices show promise to deliver high power and high efficiency. These devices are becoming commercially available. These devices have the ability to sustain very high heat densities, in excess of 10 watts per sq mm. Both SiC and GaN have breakdown voltages on the order of 50 volts, a significant improvement over silicon LDMOS devices with a 28-volt capability. Because these newer solid-state, SiC and GaN device designs offer higher efficiencies, it is anticipated that forced-air or conduction cooling will be utilized to achieve the thermal design. Another factor in the device selection process is to evaluate the tolerable heat dissipation of the devices. SiC appears to be particularly tolerant of high-power dissipations, with the ability to handle 3-10 watts/mm2 with junction temperatures of 200 C. These factors along with the plenum design and judicious use of heat pipes should be considered to provide a reliable long life environment for the HPAs. The focus of this development effort is on SiC or GaN Class E or F HPAs at the UHF frequency (405-450 MHz).

  PHASE I: Demonstrate feasibility of proposed technology in a laboratory breadboard experiment and evaluate with respect to stated performance objectives.
  PHASE II: Develop and demonstrate a solid-state prototype HPA circuit module that addresses the electrical objectives stated above and the thermal requirements that will satisfy reliable long-term operation within operational flight environments of next generation UAVs. Efficient packaging for multiple module integration should implement combiner networks to minimize RF losses, which will subsequently impact total efficiency of the HPA multi-module configuration.

  PHASE III: Refine design as necessary and incorporate into a solid-state high-power amplifier module design. Integrate and demonstrate modules to implement an operating UHF high-power radar transmitter. Transition this technology into an operational radar transmitter. PRIVATE SECTOR COMMERCIAL POTENTIAL/

  DUAL-USE APPLICATIONS: The high-efficiency transmit modules should have application to all commercial avionics manufacturers, all commercial radar applications, and all marine radar applications.

  References:  1. T.B. Mader and Z.B. Popovic, “The Transmission-Line High-Efficiency Class-E Amplifier,” IEEE M&GWL, Vol.5, N0.9, pp.290-292, Sept. 1995. 2. R. Tayrani, “A Monolithic X-band Class-E Amplifier,” IEEE GaAs IC Symposium Digest 2001, pp.205-208. 3. T. Quach et al., “Broadband Class-E Power Amplifier for Space Radar Application,” IEEE GaAs IC Symposium Digest 2001, pp.209-212. 4. Agilent Advanced Design Systems (ADS), V.1.7, & Agilent ICCAP, V.5.4.

Keywords:  Radar; Efficiency; Power Amplifier; Solid-State; Silicon Carbide; Transmitter

Questions and Answers:
Q: What is the output impedance?
A: The maximum load mismatch (VSWR) tolerance is: 5 to 1. The operational VSWR is 2:1.
Q: What is the output impedance?
A: The maximum load mismatch (VSWR) tolerance is: 5 to 1. The operational VSWR is 2:1.
Q: 1. What DC power supplies are available on the UAV to use for the amplifier design, what is the voltages and current handling for these supplies?
2. What size and weight restriction do we have on that amplifier design?
3. What is the power level, CW, and peak?
4. At what altitudes is this UAV going to operate?
5. Do we need to regulate the output power, or just ON-OFF, at full power?
A: 1. The amplifier supply voltage is approximately 100 volts DC.

2. The nominal dimensions for each module are 10 x 11 x 5.5 inches, for a volume of approximately 567 cubic inches. The module could be packaged to various dimensions, depending upon the application. In our case we are packaging the modules to fit within a wing to power a wing conformal UHF radar. Custom packaging will be required around the cooling system. The prefer cooling approach is to employ air cooling.

3. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

5. ON-OFF at full power is desired but regulating the output power will be considered.
Q: 1. Will you clarify "peak power requirement"?
It implies operation is in pulsed mode.
2. What is the pulse width and duty cycle?
3. Is CW demonstration necessary?
A: 1. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

2. Pulse Width: up to 100 microseconds
Duty Factor: 25%
Pulse Droop: 1 db

3. A cw or pulsed demonstration in phase 1 is not necessary but highly desired.
Q: 1. What is the power of the highest module currently?
2. What is the resolution of the frequency range this amplifier must operate?
3. What is the temperature range this amplifier must operate in?
A: 1. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

2. The focus of this development effort is on Class E or F High Power Amplifiers (HPAs) at the UHF frequency (405-450 MHz).

3. Our baseline for "base plate" temperature is 25 degrees C. This may vary in a final design of the radar transmit module depending upon the environment that the transmitter is to operate in. Note however that the base plate temperature will be kept low to permit high power output per device while allowing the substrate materials to operate at their capabilities in terms of junction temperatures. For example GaN can operate in the range of 200 degree C junction temperatures and SiC can operate with 275 degree C temperatures. If one were to operate the devices at higher case temperatures, the power output per device would have to be reduced to ensure the 200 or 275 degree junction temperature was not exceeded.
Q: 1. What is the gain required?
2. What is the PAE required?
3. What harmonic levels are acceptable?
4. Is there an IP3 spec?
5. What are the size and weight specs?
A: 1. The RF Gain required would be 40 to 50 db range. At 40 db we would need an RF input of about 1 watt, at 50 db we would need only 100 milliwatts.

Note that if too much gain is in the amplifier it will oscillate.
During the detail design that issue would be resolved. Higher gain would allow use of smaller RF cables from the Exciter but that weight gain may be offset by additional shielding weight in the module to prevent oscillation. Less gain would mean less power dissipation in the wing area which may also be desirable.

2. The hightest drain efficiency is desirable. The targeted drain efficiency is 75%-95%.

3. The harmonic levels should be kept at a reasonable acceptable level and should be part of the tradeoff analysis.

4. The harmonic levels should be kept at a reasonable acceptable level and should be part of the tradeoff analysis.

5. The nominal dimensions for each module are 10 x 11 x 5.5 inches, for a volume of approximately 567 cubic inches. The module could be packaged to various dimensions, depending upon the application. In our case we are packaging the modules to fit within a wing to power a wing conformal UHF radar. Custom packaging will be required around the cooling system. The prefer cooling approach is to employ air cooling.

The targeted RF modlue weight is 30lbs.
Q: 1. What is the minimum output power requirement?
2. What is the minimum gain requirement or is there an established input power level?
3. Is the proposal limited to SiC and GaN devices or are other technologies acceptable given the output and efficiency requirements?
4. Are minimal corporate feeds acceptable?
A: 1. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

2. The RF Gain required would be 40 to 50 db range. At 40 db we would need an RF input of about 1 watt, at 50 db we would need only 100 milliwatts.

Note that if too much gain is in the amplifier it will oscillate.
During the detail design that issue would be resolved. Higher gain would allow use of smaller RF cables from the Exciter but that weight gain may be offset by additional shielding weight in the module to prevent oscillation. Less gain would mean less power dissipation in the wing area which may also be desirable.

3. The topic is limited to GaN and SiC devices as stated in the topic.

4. Yes.
Q: 1. What DC power supplies are available on the UAV to use for the amplifier design, what is the voltages and current handling for these supplies?
2. What size and weight restriction do we have on that amplifier design?
3. What is the power level, CW, and peak?
4. At what altitudes is this UAV going to operate?
5. Do we need to regulate the output power, or just ON-OFF, at full power?
A: 1. The amplifier supply voltage is approximately 100 volts DC.

2. The nominal dimensions for each module are 10 x 11 x 5.5 inches, for a volume of approximately 567 cubic inches. The module could be packaged to various dimensions, depending upon the application. In our case we are packaging the modules to fit within a wing to power a wing conformal UHF radar. Custom packaging will be required around the cooling system. The prefer cooling approach is to employ air cooling.

3. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

5. ON-OFF at full power is desired but regulating the output power will be considered.
Q: 1. Will you clarify "peak power requirement"?
It implies operation is in pulsed mode.
2. What is the pulse width and duty cycle?
3. Is CW demonstration necessary?
A: 1. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

2. Pulse Width: up to 100 microseconds
Duty Factor: 25%
Pulse Droop: 1 db

3. A cw or pulsed demonstration in phase 1 is not necessary but highly desired.
Q: 1. What is the power of the highest module currently?
2. What is the resolution of the frequency range this amplifier must operate?
3. What is the temperature range this amplifier must operate in?
A: 1. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

2. The focus of this development effort is on Class E or F High Power Amplifiers (HPAs) at the UHF frequency (405-450 MHz).

3. Our baseline for "base plate" temperature is 25 degrees C. This may vary in a final design of the radar transmit module depending upon the environment that the transmitter is to operate in. Note however that the base plate temperature will be kept low to permit high power output per device while allowing the substrate materials to operate at their capabilities in terms of junction temperatures. For example GaN can operate in the range of 200 degree C junction temperatures and SiC can operate with 275 degree C temperatures. If one were to operate the devices at higher case temperatures, the power output per device would have to be reduced to ensure the 200 or 275 degree junction temperature was not exceeded.
Q: 1. What is the gain required?
2. What is the PAE required?
3. What harmonic levels are acceptable?
4. Is there an IP3 spec?
5. What are the size and weight specs?
A: 1. The RF Gain required would be 40 to 50 db range. At 40 db we would need an RF input of about 1 watt, at 50 db we would need only 100 milliwatts.

Note that if too much gain is in the amplifier it will oscillate.
During the detail design that issue would be resolved. Higher gain would allow use of smaller RF cables from the Exciter but that weight gain may be offset by additional shielding weight in the module to prevent oscillation. Less gain would mean less power dissipation in the wing area which may also be desirable.

2. The hightest drain efficiency is desirable. The targeted drain efficiency is 75%-95%.

3. The harmonic levels should be kept at a reasonable acceptable level and should be part of the tradeoff analysis.

4. The harmonic levels should be kept at a reasonable acceptable level and should be part of the tradeoff analysis.

5. The nominal dimensions for each module are 10 x 11 x 5.5 inches, for a volume of approximately 567 cubic inches. The module could be packaged to various dimensions, depending upon the application. In our case we are packaging the modules to fit within a wing to power a wing conformal UHF radar. Custom packaging will be required around the cooling system. The prefer cooling approach is to employ air cooling.

The targeted RF modlue weight is 30lbs.
Q: 1. What is the minimum output power requirement?
2. What is the minimum gain requirement or is there an established input power level?
3. Is the proposal limited to SiC and GaN devices or are other technologies acceptable given the output and efficiency requirements?
4. Are minimal corporate feeds acceptable?
A: 1. The desired peak RF power per module is approximately 8.6 kW. The radar design that we are using assumes a 25% duty factor which would mean the average transmitted RF power is 2.14 kW. We are considering 7 transmit modules for the radar for a total transmitted power of 15 kW RF.

2. The RF Gain required would be 40 to 50 db range. At 40 db we would need an RF input of about 1 watt, at 50 db we would need only 100 milliwatts.

Note that if too much gain is in the amplifier it will oscillate.
During the detail design that issue would be resolved. Higher gain would allow use of smaller RF cables from the Exciter but that weight gain may be offset by additional shielding weight in the module to prevent oscillation. Less gain would mean less power dissipation in the wing area which may also be desirable.

3. The topic is limited to GaN and SiC devices as stated in the topic.

4. Yes.

Record: of