Patent GB-1488610-A (GB)
Title: Antenna apparatus
IPC: H01Q3/26
Filed: 1975-03-06
Abstract: 1488610 Aerial scan control; radio directionfinders MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 6 March 1975 [6 March 1974 7 March 1974] 9451/75 Headings H4A and H4D An aerial apparatus comprises an aerial means which is controllable to exhibit directivity in a plurality of directions, scanning signal means generating a signal for controlling the directivity of the aerial means through said directions in succession, and memory means for retaining signals which are related to signal levels from the aerial means when exhibiting directivity in the said directions. The apparatus also comprises detecting means for detecting a maximum level memory signal, and control means responsive to the detecting means to hold the directivity of the aerial means in the direction corresponding to said maximum level memory signal. The apparatus may be applied in a fixed station-mobile station radio communication system to both types of station. As described, the aerial means has four available directions of directivity, at right angles to each other. A central sleeve-type dipole 2, Fig. 1, is surrounded by four parasitic elements 3a to 3d, each of which is in two parts bridged by a series tuned circuit in parallel with a switching diode (Fig. 3, not shown). When a diode is switched on by a digital "1" output from an associated OR gate 15a to 15d the parasitic element acts as a director, and when there is no output (digital "0") it acts as a reflector. Alternatively, four independent aerials (e.g., of Yagi-Uda type) pointing in the four directions may be used (Fig. 7, not shown). The aerial outputs are coupled through respective switching diodes to a common terminal, and are made available in succession by digital "1" outputs from the gates 15a to 15d. A scanning signal generating means 4 receives clock pulses at a terminal S90 from a generator 6 via a NAND gate 14, and generates successive signals at terminals S11 to S14 which are coupled to first input terminals of the gates 15a to 15d, whereby the aerial scanning outputs are obtained. The means 4 is a ring counter composed of six flip-flops and also provides an initiating memory clearing signal at a terminal S10, and a terminating signal at a terminal S15. Output from the active dipole 2 at a terminal 30 is used in a radio receiver to provide at a terminal 7 of a multiplexer 8 a direct current which is indicative of the signal strength obtained from the aerial means. The multiplexer 8 receives outputs from the terminals S11 to S14, and is operated synchronously with the scanning of the aerial means to connect the successive inputs at the terminal 7, corresponding to the four directions of directively, to respective charging devices 9a to 9d. Each such device may comprise a field effect transistor, a capacitor connected to the input terminal thereof, and a transistor also connected to said input terminal and used for discharging the memory signal, i.e., the charge in the capacitor, at the commencement of the scanning sequence (Fig. 3, not shown). A differential amplifier 10 receives input signals from the charging devices 9a to 9b and produces a digital "1" signal on that one of its four output terminals pertaining to the input signal of highest level (provided it exceeds a threshold value) and digital "0" outputs on its other output terminals. Said output terminals are connected to respective first input terminals of four NAND gates 11a to 11d, the second input terminals of which are connected to the terminal S15 of the scanning signal generating means 4. When the terminating signal is given, if there is a digital "1" signal on one of the output terminals of the differential amplifier 10, the corresponding one of the gates 11a to 11b produces a digital "0" signal which, via a four input NAND gate 12 and an inverter 13, prevents the passage of clock pulses from a generator 6 through the gate 14 to the terminal S90 of the means 4, i.e., scanning is stopped. The output signals of the gates 11a to 11d are also coupled via respective inverters 20a to 20d to the second input terminals of respective OR gates 15a to 15d, so that the directivity of the aerial means is held in the direction of the strongest received signal. A manual or automatic reset signal generating means 5 may be connected to a terminal S91 of the scanning signal generating means 4. In another embodiment (Figs. 4, 6, not shown), instead of a terminating signal being applied simultaneously to the holding gates (11a to 11d, Fig. 1) a succession of individual scanning signals is applied to said gates, and also to the OR gates (15a to 15d, Fig. 1) which control the directivity of the aerial means instead of inverted outputs from the holding gates.