Q A_Sources_Sought_V1.pdf

Sources Sought Notice

BAA-RVKV-2013-0005

Questions and Answers

Question Government Response

1. Under the power-added-efficiency (PAE) specifications (Table 1), a 5-d backoff efficiency is requested. The 5-dB backoff for the PAE: Is it input backoff or output-power backoff?

The requirement is for the output power backoff.

Since the amplifier will most likely be operated in compression (although not a requirement) during nominal high power output (see answer #2), this may require adjusting the operating mode (such as bias changes, linearization, etc.) to achieve the required PAE at this backoff.

2. Is the operating point of the amplifier intended to be at saturation? At 5-d backoff? Or can we chose it so long as the amplifier meets all performance specification (Output RF power, PAE, AM/PM, Gain flatness, etc.)

The primary requirement is efficiency at the nominal high power output, while meeting the other performance requirements. It is expected (although not a requirement) that the amplifier may need to be operated near saturation to achieve the stated efficiency.

3. Is the group delay variation over temperature?

Frequency

Group delay is the negative slope of the phase verses frequency behavior of the amplifier (incremental change in phase/incremental change in 2*pi* frequency). The constraint on the group delay insures that over the frequency band of interest, the slop remains inside the limits specified in Table 1.

4. Is the AM/PM intended as AM/PM conversion or AM/PM transfer?

The limited specified for AM to AM and AM to PM distortion are generally described in terms of conversion distortion.

5. Is a radiation-cooled package an option where the radiator of the amplifier is exposed outside of the spacecraft to dissipate heat to space? A radiation-cooled package radiates a significant portion of the amplifier waste heat directly to space and therefore may significantly reduce required satellite dissipation and size.

It is preferred that the thermal design of the amplifier should permit the greatest flexibility to the spacecraft designer. The offeror is posing an option, where presumably, the amplifier must be mounted externally, or with an external view to space. A more conventional approach, which may offer more flexibility, is that waste heat is conducted to a thermal path within the spacecraft to an external radiator. This may permit more choices in the placement of this component, and would potentially allow more options for shielding, EMI and other protection. However, this more conventional approach is not a requirement as long as other requirements are met. If this radiation-cooled approach is proposed, the offeror is encouraged to explain how the considerations for integration in a spacecraft can be accommodated and the benefits of this approach.

6. In relation to the subject announcement we kindly ask you for clarification about the number of amplifiers that would be the outcome of this effort. Will it be one amplifier covering all L1, L2, L5 bands with different output power levels at each sub-band, or three amplifiers one for each sub-Band.

The offeror is referred back to the published Sources Sought announcement for the answer to this question. Specifically, under section c.

Objective: (para #2) ”In support of this objective, the Government requests information on industry’s capability to perform the research and development necessary to deliver a space qualifiable advanced technology L-band RF power amplifier (minimum TRL 5+).” (para #5) “The input to the amplifier is the low power radio frequency signal at one of the navigation frequencies (L1, L2 or L5) modulated with the corresponding navigation signals. The intent of any future procurement would be to perform the research and development activities necessary to identify and validate an amplifier design/architecture suitable for application in all these frequency ranges and for all current and projected navigation signals and modulations.”

7. For all bands what is the expected Peak to Average of the composite signal covering the ±50 MHz bandwidth around each of the center frequencies: L1, L2 or L5?

The signal Peak to Average Power Ratio (PAPR) will be less than or equal to 1 dB.

8. In general, what are the signal characteristics being amplified?

The signals are the existing GPS codes, described at www.gps.gov. Generally these are PRN codes transmitted via phase shift key modulation on the L-band carrier. The composite signal is a group of phase modulated signals which are combined to produce a very nearly constant RF envelope.

Applicability of this amplifier to a broader range of possible signals is also of interest, but not required.

9. If there is a significant PAR of the composite input signal, are the specified Output RF Power levels, and Power Added Efficiencies (threshold and Objective) for average or peak levels?

The signal has an insignificant PAPR. The RF output power and PAE are specified for average levels.

10. Does the Group Delay variation reference the peak to peak or 0 to peak variation over the full 100 MHz bandwidth?

The group delay variation requirement is specified in terms of a peak to peak value.

11. Does the specification on AM/PM apply to dynamic or static power variation (i.e. if the signal has a significant AM component does this apply to the average power or the instantaneous power?)

The specification is given as the static value of

AM/PM.

12. With regard to the specification to life, we expect performance degradation over a lifespan, especially in the presence of radiation. To what level of degradation does this specification apply?

The flight operational design life shall be 15 years (objective), and it is desired that the performance requirements are met throughout this lifetime.

13. With regard to signal quality, what would be considered a measure of Quality (e.g. EVM, IM, BER, etc.)?

EVM and BER are composite measurements of signal distortion. The AM/PM, gain flatness, group delay, and VSWR are the critical contributing factors that determine signal quality, and these are given in the specification.

14. We seek clarification on the bandwidth requirement reflected in Table 1 of the Sources Sought. Based on our understanding of the GPS signals +/-50MHz bandwidth is not required.

Are there other wider bandwidth signals anticipated or was this intended to be 50MHz total bandwidth?

The bandwidth requirement (+/- 50 MHz) is intentionally set wider than the bandwidth of the signals to ensure the amplifier bandwidth does not contribute to signal distortions such as correlation loss, AM/PM, or code truncation loss.

15. The power output of the advanced technology power amplifier varies significantly (by more than a factor of 2.7) over the three frequency bands listed (L1, L2 or L5). Consequently, it would be difficult to develop a single amplifier that would provide high efficiency operation at all three desired power levels and frequencies.

Do you expect the three power outputs at L1, L2 or L3 to be provided by a single power amplifier or separate amplifiers, and can you clarify what adjustments might be available to adjust output power level to maintain high efficiency as a function of frequency-supply voltage, etc.?

Whatever additional information you can provide on the desired architecture and/or CONOPS of the power amplifier(s) would be greatly appreciated.

The offeror is referred back to the published Sources Sought announcement for the answer to this question. Specifically, under section c.

Objective: (para #2) ”In support of this objective, the Government requests information on industry’s capability to perform the research and development necessary to deliver a space qualifiable advanced technology L-band RF power amplifier (minimum TRL 5+).” (para #5) “The input to the amplifier is the low power radio frequency signal at one of the navigation frequencies (L1, L2 or L5) modulated with the corresponding navigation signals. The intent of any future procurement would be to perform the research and development activities necessary to identify and validate an amplifier design/architecture suitable for application in all these frequency ranges and for all current and projected navigation signals and modulations.”

16. For SOC #6 "Alternate Options," how much detail is required (i.e., is a ROM expected for that, too)?

The offeror is referred back to the Sources Sought solicitation, page 4, b. Statement of Capabilities (SOC). If alternate options are proposed, the same conditions apply as apply to other elements included in the General Background section of the solicitation, “to include sufficient written information to indicate capacity and any other specific and pertinent information that would enhance our evaluation.”

17. For SOC #7 "Feedback/Comments," what is the expectation for this section? What is the Government looking for feedback on?

The offeror is again referred back to the Sources Sought solicitation, page 4, b. Statement of Capabilities (SOC). Examples of Feedback/Comments would include such items as a critique of the Government objectives, technical goals and requirements, assumptions, etc., “to include sufficient written information to indicate capacity and any other specific and pertinent information that would enhance our evaluation.”