Calibration step 2
In the second calibration step, channel 2 is activated and channels 1, 3, and 4 receive calibration signals. The calibration signal level is limited by two aircraft Minimum Operational Performance Standards (MOPS) requirements.17 The first requirement is that when the transmitter is in an inactive state, the RF power at the antenna terminal should not exceed -70 dBm. The second requirement is that the maximum receiver sensitivity is -99 dBm. These limits set the dynamic range of the calibration signal between -99 dBm and -70 dBm. Table 3 illustrates the performance of different antenna modules.
A quick glance at Table 3 shows that the active antenna module can provide good performance (when properly calibrated) compared to multiple antenna systems implemented with and without phase shifters, as well as with systems using the SBFN with a five monopulse-element antenna system with four receive channels. The active antenna approach provides four receive channels and antenna terminals with moderate bandwidth and avoids an additional phase shifter.
1. L. G. Maloratsky, "RF Design of Avionics L-Band Integrated Systems," Microwave Journal, 2009.
2. D. Kutman et al., "Multifunctional Aircraft Transponder," United States Patent No. 6,222,480, April 2001.
3. L. G. Maloratsky et al., "Combined Aircraft TCAS/Transponder with Common Antenna System," United States Patent No. 7,436,350, October 2008.
4. "Signal Sorting Methods and Directional Finding," Microwaves 101.
5. "An Introduction to Dipole Adcock Fixed-Site DF Antennas," Application Note AN-005, PDF Products, December 1999.
6. M. F. Gard et al., "Electronic Compass," United States Patent No. 5,850,624, December 1998.
7. B. E. Dinsmore et al., "Apparatus and Method for an Amplitude Monopulse Directionall Antenna," United States Patent No. 5,191,349, March 1993.
8. L. G. Maloratsky et al., "Aircraft Directional/Omnidirectional Antenna Arrangement," United States Patent No., 7,385,560, June 2008.
9. L. G. Maloratsky, "Switched Directional/Omnidirectional Antenna Module for Amplitude Monopulse Systems," IEEE Antennas & Propagation Magazine, October 2009.
10. L. G. Maloratsky et al., "Switched Beam Forming Network for an Amplitude Monopulse Directional and OmnidirectionalAntenna," United States Patent No. 7,508,343, March 2009.
11. L. G. Maloratsky, "Analyze Bearing Accuracy of a Monopulse System," Microwaves & RF, Part 1, March 2009, Part 2, April 2009.
12. L. G. Maloratsky, Passive RF and Microwave Integrated Circuits, Elsevier, Amsterdam, 2004.
13. T. Seki, "Low-Loss and Compact Sector Antenna that Adopts Omnidirectional Characteristics," 2000 IEEE Antenna and Propagation Society International Symposium, Vol. 2, 2000.
14. Svantesson et al., "High-Resolution Direction Finding Using a Switched Parasitic Antenna," Statistical Signal Processing, 2001 Proceedings of 11th IEEE Signal Processing- Workshop, pp. 508-511.
15. B. Dinev, "GSM off Road-Increasing Service Area for Mobile Telephony and Data-Advanced Antennas," Master's Degree Project, Stockholm, Sweden, 2006.
16. D. V. Thiel et al., Switched Parasitic Antennas for Cellular Communications, Artech House, Boston, 2002.
17. TCAS Minimum Operation Performance Standards MOPS, RTCA, Inc., 1997.