GB704659A - Improvements in or relating to directly fed notched aerofoil aerials - Google Patents

Abstract

704,659. Aerials. MINISTER OF SUPPLY. Dec. 14, 1949 [Dec. 15, 1948], No. 32491/48. Classes 40 (5) and 40 (7) A metal skin aerofoil w is adapted to function as an aerial by forming a notch in its edge at a position selected to intercept a substantial part of any current in the aerofoil, the notch being cut to a depth which is small compared with a quarter wavelength and tuned to resonance by a capacity c connected across the notch. R.F. energy is coupled to or extracted from the notch by coaxial cable c. Metal plates, a<SP>1</SP>, a<SP>2</SP>, b bound the sides of the notch, and dielectric covers e', e' enclose the notch to maintain the aerodynamic surface. Condenser c is controlled remotely by electric motor k. The construction illustrated is suitable for installing in the trailing edge of a wing and the aerial thus provided operates with horizontally polarized means. For vertically polarized means the leading edge of a fin may be notched, Fig. 5 (not shown), the fin functioning as a unipole with the aircraft acting as a counterprise. In this embodiment the notch is completely filled with a shaped dielectric slab, and the tuning condenser is housed within the notch in a hole in the dielectric. Radio frequency input and output couplings.- As shown coaxial cable c is connected across the slot between the side plates a<SP>1</SP>, d at a position from the end plate b selected to provide an impedance match. In an alternative matching system, Fig. 3 (not shown), the cable is connected across one of two tuning condensers connected in series across the notch. According to the Provisional Specification, Fig. 2 (not shown), the coaxial cable is connected directly across the mouth of the notch and a tuning condenser is connected across the cable by means of a T junction. Specification 607,159 is referred to in the Provisional Specification.