A recent paper1 has described the design and performance of a waveguide-fed parallel plate lens which provides five beams from a sixteen element antenna array, with sidelobes ≈ − 20 dB and beam crossovers ≈ − 10dB, in the frequency band 8–12 GHz. A microstrip version of this lens has been designed, constructed and tested, with the addition of a beam port overlap network to now provide nine beams with crossovers ≈ − 2 dB. Fair performance is achieved at midband, but internal reflections are found to limit the bandwidth of the microstrip lens design.
Results are presented of observations extending over a decade of propagation by means of sporadic-E ionization at frequencies in the range 59 to 77 MHz. The seasonal, diurnal and longer term trends in the data are discussed. Cumulative distributions of event durations are presented for different groupings of the data. A limited study of possible polarization discrimination at these frequencies is also described. The results are discussed in terms of their potential use in spectrum planning at frequencies around 70 MHz.
The general properties of hybrid networks are described and two main types, the quadrature and the 0¿180° types, are identified. A list of uses of hybrid networks in radio frequency circuits follows. Seventeen configurations of hybrid networks are given with diagrams showing the variations of their input and output parameters with frequency. The 3 dB transmission line coupler is described in more detail and multiplexers are mentioned.
