We recently spoke with Dr. Koen Van Caekenberghe, author of several articles on RF MEMS technology for radar sensors, about RF MEMS phase shifters. Koen shares his thoughts on the small but growing RF MEMS phase shifter market including applications, market developments, pricing and vendors of RF MEMS phase shifters as well as alternative technologies.
The radar sensor market has a global turnover of about $6.25 billion annually according to Defense Industry Daily. In Koen's opinion, approximately 50% of the budget is spent on airborne, ground-based, and naval AESA radar sensors, and approximately 25% of the budget is spent on mechanically scanned radar sensors -- and during the next decade, 20% of the mechanically scanned radar sensors might be replaced by PESA radar sensors based on RF MEMS shifters, resulting in a potential global market of $300 million annual
MEMS Investor Journal: Please provide a general description of RF MEMS phase shifters.
Koen: RF MEMS phase shifters alter the phase of an RF signal by means of RF MEMS switches, switched capacitors, and varactors [1, 2]. Phase shifters are used in radars based on electronically scanned arrays.
MEMS Investor Journal: How do radars work?
Koen: Radars sense angle, range and velocity of (moving) scatterers in the environment. Radar figures of merit include field of view in terms of solid angle and maximum unambiguous range and velocity, as well as angular, range and velocity resolution. The angle of a target is detected by scanning the field of view with a directive beam. Scanning is done electronically, by scanning the beam of an array, or mechanically, by rotating an antenna. The range and radial velocity of a target are detected through frequency modulation (FM) ranging and range differentiation (frequency modulated continuous wave radar), or through pulse delay ranging and the Doppler effect (pulse-Doppler radar). The angular resolution is inversely related to the half power beamwidth of the antenna or the array, whereas the range resolution is inversely related to the signal bandwidth.
MEMS Investor Journal: As you mentioned, RF MEMS phase shifters are used in radars based on electronically scanned arrays. What are the main advantages of using them?
Koen: Electronically scanned arrays, or phased arrays, offer several advantages over mechanically scanned antennas such as multiple agile beams and interleaved radar modes. Figures of merit of an electronically scanned array, as shown in Fig. 1, are the bandwidth, the effective isotropically radiated power (EIRP) times the Gr/T product, the field of view, the half-power beamwidth, the pointing error, the polarization purity and the sidelobe level. EIRP is the product of the transmit gain, Gt, and the transmit power, Pt. Gr/T is the quotient of the receive gain and the antenna noise temperature. Gr and Gt are linearly related to the aperture area, whereas the half power beamwidth is inversely related to the largest aperture dimension. The field of view is limited by the antenna element spacing, d, and the pointing error is inversely related to the phase shift resolution (number of effective bits of the phase shifter).
Figure 1: Figures of merit of an electronically scanned array set the radar sensor's ability to search and track targets.
MEMS Investor Journal: What is the history of RF MEMS phase shifters and where were they first developed?