| 摘要 |
<p>A fairly simple R.F. system for indicating the bearing of the source of incident microwave radiation comprises two spaced, broad-beam antennas (A1, A2) supplying signals via power dividers (PD1, PD2) to amplitude comparison means and phase comparison means, both of which operate without down-conversion to an I.F. The main lobes of the radiation patterns of the antennas (A1, A2) are inclined towards one another so that for non-normal incidence there is a difference between the amplitudes of signals received respectively by the two antennas (A1, A2). The amplitude comparison means comprises detector diodes (D1, D2), logarithmic amplifiers (LA1, LA2), and a first subtractor (SUB1), the magnitude of the output signal from which [sensed for example with a threshold detector (TD)] indicates from which side of normal the radiation is incident. The phase comparison means comprises a hybrid ring (HR) having <<sum>> and <<difference>> output ports (3, 4 respectively) connected respectively to an instantaneous frequency measuring apparatus (IFM) and a detector diode (D3), and further comprises logarithmic amplifiers (LA3, LA4) and a second subtractor (SUB2), the outputs of detector diodes in IFM being summed to provide the signal at its output (6) connected to one amplifier (LA3). The output of the second subtractor (SUB2) is an accurate but ambiguous representation of the bearing angle with respect to normal (being an even function thereof); the ambiguity can be resolved by reference to the output signal of the first subtractor (SUB1) which may also be used as an approximate representation of the bearing angle.
<??>Using broad-band R.F. components, the system may readily be operable over a broad bandwidth, e.g. an octave.
<??>A data comparator (DC) and a pulse repetition frequency filter (FLTR) control gates G1-G3) which inhibit the provision of bearing data except with pulsed incident radiation having substantially a desired frequency and PRF. </p> |
