Dual-feed, dual-mode antenna for mono-directional pattern

Abstract

A compact transmitting and receiving antenna has dual feeds permitting magnetic and electric dipole radiation. The antenna includes a loop antenna disposed within a loop shield and a mast. The loop shield is insulated from ground and a feed is provided to it and the mast to excite these as an electric monopole. The shield becomes part of the monopole antenna and provides the benefits of top-loading. An isolation transformer permits the simultaneous transmission of monopole and dipole radiation. The transformer converts an unbalanced coaxial feed line to the balanced loop antenna and isolates the monopole feed voltage from the loop antenna feed. To eliminate the affect of the monopole feed on the loop feed, and vice versa, the components on the high side of the monopole feed (the loop shield and mast) are driven in common mode (voltage) by the monopole feed, and will not couple the loop antenna feed through the transformer windings. Thus, with respect to the monopole feed voltage, both sides of the transformer windings connected to a loop antenna will be at the same voltage. No voltage drop across the transformer windings due to the monopole feed voltage will occur and hence no coupling to the loop feed transmitter will take place. The voltage insulation requirements are concentrated at the monopole feed point so that the isolation feed transformer takes all the voltage, making the loop, loop shield and monopole driven in common mode.

What is claimed is: 
     
       1. A transmitting and receiving antenna apparatus comprising: a loop antenna;   a monopole antenna including a ground isolated tubular mast and a tubular loop shield electrically coupled to said mast, said mast and shield surrounding said loop antenna except at a gap in said shield opposite said mast;   a loop antenna feed;   an isolation transformer providing electrical coupling between said loop antenna and said loop antenna feed; and   a monopole antenna feed electrically coupled to said monopole antenna.   
     
     
       2. An apparatus according to claim 1 in which said loop antenna and said monopole antenna are driven at a common voltage when in a transmitting mode. 
     
     
       3. An apparatus according to claim 2 in which a voltage drop between said monopole antenna feed and said monopole antenna occurs across said isolation transformer. 
     
     
       4. An apparatus according to claim 3 in which said loop antenna is balanced and in which said loop antenna feed is unbalanced and in which said isolation transformer converts said unbalance loop antenna feed to said balanced loop antenna. 
     
     
       5. An apparatus according to claim 4 in which said loop antenna feed and said monopole antenna feed are operably coupled to tuning, matching and power combining means. 
     
     
       6. An apparatus according to claim 5 in which said loop antenna and said monopole antenna are operated below resonance and in which said tuning, matching and power combining means includes an inductive frequency tuner for said monopole antenna feed and a capacitive frequency tuner for said loop antenna feed. 
     
     
       7. An apparatus according to claim 5 in which said tuning, matching and power combining means includes a low power signal source for providing a low power signal to a first power level tuner having an output of which is passed to a first amplifier having an output passed to said loop antenna feed, and   a second power level tuner having an output of which is passed to a second amplifier having an output passed to said monopole antenna feed.   
     
     
       8. An apparatus according to claim 1 in which said monopole antenna feed is directly electrically coupled to said monopole antenna. 
     
     
       9. A transmitting and receiving antenna apparatus comprising: inner and outer loop antennas;   a monopole antenna including a ground isolated tubular mast and inner and outer tubular loop shields electrically coupled to said mast, said inner and outer tubular loop shields having axis orthogonal to one another and to a longitudinal axis of said mast, said loop antennas being surrounded by said mast and their respective shields except at gaps in said shields opposite said mast;   an inner loop antenna feed;   an outer loop antenna feed;   an isolation transformer providing electrical coupling between said inner loop antenna and said inner loop antenna feed;   an isolation transformer providing electrical coupling between said outer loop antenna and said outer loop antenna feed; and   a monopole antenna feed electrically coupled to said monopole antenna.   
     
     
       10. An apparatus according to claim 9 in which said monopole antenna feed is directly electrically coupled to said monopole antenna. 
     
     
       11. An apparatus according to claim 9 in which said loop antennas and said monopole antenna are driven at a common voltage when in a transmitting mode. 
     
     
       12. An apparatus according to claim 11, in which a voltage drop between said monopole antenna feed and said monopole antenna occurs across said isolation transformers. 
     
     
       13. An apparatus according to claim 12 in which said loop antennas are balanced and in which said loop antenna feeds are unbalanced and in which said isolation transformers convert said unbalance loop antenna feeds to said balanced loop antennas. 
     
     
       14. An apparatus according to claim 13 in which said loop antenna feeds and said monopole antenna feed are operably coupled to tuning, matching and power combining means. 
     
     
       15. An apparatus according to claim 14 in which said loop antennas and said monopole antenna are operated below resonance and in which said tuning, matching and power combing means includes an inductive frequency tuner for said monopole antenna feed and an individual capacitive frequency tuner for each of said loop antenna feeds. 
     
     
       16. An apparatus according to claim 14 in which said tuning, matching and power combining means includes a low power signal source for providing a low power signal to a first power level tuner having an output of which is passed to a first amplifier having an output passed to said inner loop antenna feed,   a second power level tuner having an output of which is passed to a second amplifier having an output passed to said outer loop antenna feed, and   a third power level tuner having an output of which is passed to a third amplifier having an output passed to said monopole loop antenna feed.