US3798649A

US3798649A - Antenna control

Info

Publication number: US3798649A
Application number: US00283951A
Authority: US
Inventors: S Houng
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-08-28
Filing date: 1972-08-28
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19

Abstract

An automatic control for a motorized directional antenna of the type used for reception of a high frequency broadcast signals. The control includes electronic circuitry for monitoring the incoming signal input at a broadcast receiver and electronically comparing the received signal to a signal of maximum strength from the signal source received during movement of the antenna, together with a logic-controlled switching circuit that causes the antenna motor to reverse in a predetermined pattern to hunt and aim the antenna at an angular position at which the maximum signal strength is received.

Description

I United States Patent [1 1 [111 3,798,649

Houng Mar. 19, 1974 ANTENNA CONTROL Primary Examiner-Maynard R. Wilbur [76] Inventor: Shunien Houng, 917 E. DeSmet, Assistant Examiner-Theodore Blum Spokane Wash 99202 Attorney, Agent, or Ftrm-Wells, St. John & Roberts [21] Appl. No.: 283,951 An automatic control for a motorized directional antenna of the type used for reception of a high fre- [52] CL 343/117 R quency broadcast signals. The control includes elec- [51] Int Cl G015 1/44 tronic circuitry for monitoring the incoming signal [58] Field 343/117 R input at a broadcast receiver and electronically coma "5 7 'paring the received signal to a'signal of maximum [56] References Cited strength from the signal source received during movement of the antenna, together with a logic-controlled UNITED STATES PATENTS switching circuit that causes the antenna motor to re- 33371969 6/1973 343/117 R verse in a predetermined pattern to hunt and aim the atoms g antenna at an angular position at which the maximum ogers.... 3,686,671 8/1972 Holley 343/117 R slgnal Strength recewed' MECHAMlCN. COUPLJMG 4 Claims, 11 Drawing Figures I votmcrr. i coMPARAron Vt RESET no.2. l i l l {g l 2 i 1 MAXIMUM vomaea R E SGNAL com R Ei BNARY AMTEWXA AMPLIFIER 'm' DETECTOR NOAIA COUNTER /0 ('5 (7x 1 i MEMORY SWITCHWG ERASER C\RCUIT I w MOTOR J (DUTROL PAIENTEDIIIAR I 9 I974 3Q798649 SHEET 1 {IF 3 MECHAMICN. COUPLING VOLTAGE. I QOMRARATOR VT RESET I No.2. I 5 6 I4 I M I x ANTENNA R E I IGwA L a LCfiki??? E; r BINARY AMPLIFIER vm' DETECTOR 4 COUNTER /0 g,

(5 FIGI (2x I! I MEMORY SWITCHING ERASER C\RCUIT FIG 2 30 X I fl/FZ/T IZI 38 J( MOTOR I M x OUTPUT V: 20 4 In 'ZfififQQ-p 5r COLITROL T K'KMVVI) 27 32 Z4 26 M 26 L22 25 r I. G I I I I I o I l I I AA/rew v V0 O/TFZ/T I I I AA/GZE FIG 3 Q I I I 79 l/ o I I I I I #955 010 I I I IAA/TEA/NA VOLTAGE. I I I ANGLE COMPARATOR I I I I I 4 q /g/ OUTPUT VOLTAGE H H LOG/CO 0 ANTENNA ANGLE PATENTEUMAR 1 9 1914 3; 798 649 SHEET 3 OF 3 AUIZA/A/A FIG 7 g a Q R J I 0. Ac. 44 w MOTOR ga a g2 43 A- F T L FIG 8 VAR/A BLES F LIA/C 7704/5 Q. Q 6 M F R I I 0 O I I I O O O I O I I O I I 0 I O I I O I 0 I 0 1' 0 r I 0 I I 0 I O O O O O O I I 0 I I O I O I I O I I O O I O O I I I O ANTENNA CONTROL BACKGROUND OF THE INVENTION This disclosure relates to an electronic circuit for au tomatically controlling rotation of a directional broadcast receiving antenna to obtain maximum signal strength. The circuitry operates independent of any external or manual controls to automatically turn the antenna to hunt the rotational position at which maximum signal strength is achieved. To assure that the rotatable antenna is positioned properly, the control circuitry for the antenna motor is programmed logically to move the antennaangularly beyond the desired posi: tion and reverse its rotation in repetitive pattern of angular movement to return such location once it has been located.

Many prior efforts have apparently been directed to mechanization of antenna control. The most common system is a simple manual control switch that allows a person to manually operate the rotor for the antenna and set it at a desired angular position when changing stations at the broadcast receiver. An example of such a system is shown in the Jordan U. 5. Pat. No. 2,498,957.

The prior U. S. Pat. No. 2,597,424 to Znaidukas, shows an automatic control system, but it seeks a signal of predetermined strength. It is not designed to seek maximum strength regardless of the specific amplitude of the signal.

The Bennett U.S. Pat. No. 3,197,683 discloses a pulse-controlled system for an antenna rotor, but this requires presetting of the antenna for each input pulse signal. Each installation must be properly preset and such a device would not automatically seek new sta tions or signals coming from a broadcast antenna that has been physically relocated. The patents to Blauvelt, U. S. Pat. Nos. 2,872,631 and Lunn, 3,043,998 represent other prior attempts to provide semi-automatic control of a television antenna. However, these arrangements also require either manual setting of a control or presetting to match station location at the time of installation.

SUMMARY OF THE INVENTION This invention provides an electronic control for a reversible motor having a rotatable shaft that angularly turns a directional antenna for high frequency broadcast signals, such as a television or FM broadcast receiving antenna. A memory circuit monitors the strength of the instantaneous signal received by the receiver and stores the maximum signal received during each operating sequence. The signals are compared by a comparator circuit which produces a digital output signal when the comparative signal reaches a predetermined level. A binary counter receives the digital signal and produces alternate control signals in response to its detection ofa sequence of reversal in the digital output signal pattern. Eletronic switch circuits are operatively connected to the binary counter and to a motor control circuit connected to the reversible motor at the antenna to operate the motor in a preset logical sequence whereby the antenna is automatically moved beyond the angular position at which the maximum signal is received and is subsequently returned to that position and locked. The circuitry is then automatically reset at the conclusion of each operating sequence so as to be operable in a new sequence when the receiver is subsequently tuned to another signal source.

It is a first object of this invention to provide a truly automatic signal-sensing and seeking control for a rotatable broadcast signal receiving antenna, operating entirely without manual intervention or any requirement that it be individually preset to a given location and receiver.

Another object of this invention is to provide an automatic control circuit of this type which will seek out maximum incoming signals of various strength.

Another object of the invention is to provide a completely electronic control circuit so as to minimize mechanical problems and optimize dependability.

These and further objects will be evident from the following disclosure, which illustrates an example of a specific arrangement incorporating the invention, It is to be understood that the specific details disclosed are presented only by way of example and that the invention itself is set out in the claims that follow the description.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified block diagram of the control circuitry;

FIG. 2 is a schematic drawing of the maximum signal detector circuit;

FIG. 3 is an interrelated plot of voltages;

FIG. 4 is a simplified block diagram of the binary counter;

FIG. Sis a simplified diagram of the switching circuit;

FIG. 6 is a simplified diagram of the memory eraser circuit;

FIG. 7 is a circuit diagram of the motor control;

FIG. 8 is a logic truth table motor control;

FIG. 9 is a plot of the received signal intensity;

FIG. 10 is an interrelated plot of the received signal and control signals during operation of the circuitry; and

FIG. 11 is a plot similar to FIG. 10, illustrating an alternate sequence of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT The general arrangement of the present apparatus is illustrated in FIG. 1, where a conventional rotatable high frequency broadcast receiving antenna (television, short wave or FM) is illustrated by the block 10. The structure of such antennas, which typically include a rotatable mast and an electrically powered drive unit, is well-known in the art and no further description is believed necessary to an understanding of the following disclosure of control circuitry for the power unit that angularly locates the antenna for maximum signal strength.

The broadcast signal received by antenna 10 is directed to a conventional amplifier 11. The amplified signal (V,,,) is directed to a maximum signal detector circuit 12, which serves as a monitor to determine the relative intensity of the received signal during rotation of antenna 10 and as a memory to store the maximum received signal (V,,.,). The resulting differential signal voltage (V serves as a comparison of signal strengtli during an operational sequence. This differential voltage is then directed to a first voltage comparator, which converts the analog signal to a binary signal (E The binary signal is counted by a binary counter 14 that controls operation of a switching circuit 15. The switching circuit 15 is logically arranged or pre-set to operate motor control 18 for antenna in a preselected reversing pattern of rotation such that antenna 10 is moved beyond the angular position at which its maximum broadcast signal intensity is received, is then reversed to verify the location of maximum signal intensity by again passing the position of maximum signal intensity, and once more reversed to lock at that position. After each sequence, a memory eraser circuit 17 and second voltage comparator 16 re-set the circuitry and hold the antenna at its desired position until there is change in the signal received at antenna 10.

It is to be noted that the above apparatus requires no manual operation. It operates automatically when the signal received at antenna 10 is varied, which occurs normally when the receiving set is tuned to a different intensity or channel. In the case of a television receiver, each time that the user changes the channel being received at his set, the signal at antenna 10 will vary in frequency because the antenna will not then be aimed at the signal source. The antenna 10 will then be automatically rotated to seek out and lock at the angular position at which the received signal has its greatest in tensity. Unlike prior devices for such angular positioning, the present apparatus requires no pre-setting or calibration. It will automatically seek out each station, and does not require adjustment for new or relocated broadcast signal sources.

The details of the operating circuitry are shown schematically in the drawings, since the basic circuits used in this combination are well-known in electronic control and logic circuit design.

The maximum signal detector circuit 12 is illustrated in greater detail in FIG 2. It receives the amplified signal from antenna 10 and amplifier 11 at input 20. This is stored in a capacitor 21 across input 20. Capacitor 21 acts as a memory device, storing the maximum input voltage for an indefinite time during each operating sequence. It acts as a storage memory because of the very high resistance in its discharge path which consists of the high input resistance of a differential amplifier 22 and the high resistance of a reversed-bias diode 23.

A second capacitor 24 is also connected across input 20, along with a diode 25 and potentiometer 26. The output voltage from this secondary circuit is directed to differential amplifier 22 at

inputs

27, 28. The instantaneous signal directed to the differential amplifier 22 is identified as V,-v The amplifier 22 compares this signal V, with the maximum signal stored across capacitor 21 and directed to the amplifier input 27, 30. The output terminals 31, 32 of amplifier 22 produce a differential signal V,, directly proportional to the difference in the input signals. When output signal V is 0 the two input signals to amplifier 22 are equal. The relation between the angular position of the antennas, the input voltage V, and the amplifier output voltage V, is illustrated graphically in the upper two portions of FIG. 3.

The signal V is directed to a first voltage comparator 13 which converts the analog input signal to a digital output signal. The circuit 13 responds to an arbitrary threshold voltage level, producing alternating logical 0 and logical 1 signals when the differential output V passes the threshold level. The binary signal E changes from a logical l to a logical 0 when the signal V, exceeds the threshold level and returns to a logical 1 when the signal next falls below the threshold level. The operational sequence is illustrated at the lower portion of FIG. 3 relative to the signals at circuit 12.

The binary signal is monitored by a counter diagramatically illustrated in FIG. 4. It consists of two flipflop circuits 33 connected in a divided-by-four counter configuration. The output flip-flop states are indicated by Q and 6, where 6 represents not Q, as shown in the truth table (FIG. 8). The output from the binary counter 14 controls switching circuits 15.

The switching circuits, illustrated in FIG. 5, consist of three AND gates 34, one NAND 35, and an inverter 36. The AND gates 34 provide a logical 1 output when all inputs are simultaneously present and above the logical 1 level. The inverter 36 inverts the input logic statement. The NAND gate is a combination of an AND gate and an inverter output stage.

The logic statement M, R and F in the truth table, FIG. 8, represent the functions of the antenna rotor. M represents motor operation and F and R respectively represent forward or reverse movement. When M and R are 1 the motor 18 rotates in reversed direction. When M and F are 1 motor 18 rotates in a forward direction. When M is 0, the motor is turned off. The logic statements are expressed by the following equations? E- QT R M I (where Y= Q Q F M- 1 (where 1 Q Q The resetting of the apparatus is accomplished in response to the input signal voltage, V as well as the motor logic statement M. A voltage comparator 16, basically identical to the previously-described circuit 13, produces a re-set signal V, used as a re-set signal for binary counter 14 (FIG. 4) and as a trigger signal to the memory eraser circuit 17. The circuit 17 (FIG. 6) consists of an OR gate which produces a logical 1 output when either M or V, input, or both are equal to a logical 1. The logic statement is expressed by the equation E, A V,

where 17 and V, represent, respectively, the logic statements of the motor and the reference voltage output of the voltage comparator 16.

When the motor stops, both I71 and E, are at logical 1. The memory eraser discharges the capacitor 21 by operation of relay 38 to close the normally-open switch 40 connected across capacitor 21. Switch 40 can be closed manually or by operation of relay 38. This erases the stored memory of the maximum signal and latches the antenna 10 at the maximum receiving position because of the output of the differential amplifier 22 becomes negative. Whenever the input signal V is below a reference voltage shown arbitrarily at line 41 in FIG. 9, both E, and V, are at logical 1. E, then erases the stored memory at capacitor 21 and V, re-sets the binary counter such that antenna 10 begins to rotate in searching for the maximum signal input the V The motor control circuit 18 is basically shown in FIG. 7. The DC motor 42 is mechanically coupled to antenna 10. Its direction of rotation is controlled by two silcon-controlled rectifiers (SCR) 43, 44 which in turn are controlled by the logical statements R and F. The power source to motor 42 is an AC power line having terminals indicated at 45.

A typical antenna pattern during rotation of antenna is illustrated in FIG. 9. This assumes rotation in such manner as to encounter an initial increase in signal strength. The object of the present apparatus is to set antenna 10 at the center angular position at which the intensity of the received signal is at a maximum, shown in FIG. 9 by the letter C. When one selects a TV station, or if the receiving signal intensity should fall below the reference value indicated by line 411, V, is at logical 1. This re-sets the binary counter 14 and erases the stored memory at capacitor 21 in the maximum signal detector circuit 12. Antenna It) then begins to rotate and eventually the received signal intensity will rise above the reference level at 41, illustrated in FIGS. 9 and 10 by the letter A.

When the receiving signal V reaches A, as shown in FIG. 9, V, changes to logical 0. This restores the memory at capacitor 21 and releases the reset to binary 14. These logical statements are represented by the first row of the truth table in FIG. 8.

When the signal V reaches the apex C, capacitor 21 will store the maximum signal voltage received. Antenna 10 will continue rotating and pass the apex C. When this decline in received signal strength is sensed, at D, the outout signal E, of voltage comparator 13 will be switched to logical 0, which will be counted by the binary counter 14 and fed to the switching circuit 15. This changes the logical statements to the second row of the truth table.

Antenna It) is then reversed in direction and goes back to the apex C, again changing the digital output of voltage comparator l3 and moving the logical statements to the third row of the truth table. Antenna 1O continues rotating in the reverse direction until the maximum signal detector 12 senses a decrease in signal at B. This verifies that a maximum signal had been received and assures detection of a maximum signal in instances where initial rotation of the antenna resulted in a decrease of signal strength (FIG. 10). Again the digital output of voltage comparator 13 changes to 0 and changes the logical statements to the fourth row of the truth table. The antenna l0 reverses once more and goes back to the apex C. When the binary counter 14 has counted two decreases in signal strength, one on each side of a maximum signal, it locates the maximum point of signal reception between these. When the incoming signal V, next reaches the amplitude shown at C, it changes the logical statements to the fifth row of the truth table.

Upon reaching this state, shown at the fifth row of the truth table, the antenna 10 stops and M is at logical 1. This results in operation of memory eraser 17 to close switch 40 and erase the stored memory in capacitor 21. The output of the differential amplifier V becomes negative and antenna 110 is latched at the position of maximum signal reception.

Remaining rows 6, 7 and 8 are unused logical statements in the illustrated circuits.

When the binary counter 14 is re-set manually by closing switch 40, the antenna may follow the above operation, shown as an ABCDCBC operation (FIG. 10). Alternately, initial reversal of the signal may result in a decline in signal strength, in which case the apparatus will follow a BABCDC operation as shown in FIG. 11. The description of the latter is essentially the same as that discussed with respect to FIGS. 9 and 10.

Various modifications might be made in the particular circuitry used to carry out this invention. However, such modifications are believed to be well within the skill of those knowledgable in the design of logic circuits of the type discussed above.

Having thus described my invention, I claim:

1. In combination with a high frequency broadcast signal receiving antenna rotatably mounted on a support;

a reversible motor operatively connected between the support and antenna for selectively rotating the antenna so as to index the antenna for reception of a broadcast signal of maximum strength;

a motor control circuit operatively connected to the motor selectively operable to cause the motor to rotate the antenna in opposite directions;

and a receiver connected to the antenna;

the improvement in an automatic control for the motor control circuit comprising:

memory means connected to the receiver for continuously monitoring the strength of the instantaneous signal received thereby from the antenna, storing the maximum signal received and producing a comparative signal proportional to the difference in strength between the stored maximum signal and the instantaneous signal received thereby;

comparator means operatively connected to said memory means for producing a first digital output signal in response to reception of a comparative signal above a predetermined threshold level and a second digital output signal in response to reception of a comparative signal below the predetermined threshold level;

binary counter means operatively connected to said comparator means for counting two reversals of the digital output signal from said comparator means for producing alternate control output signals dependent upon the number of digital output signals received thereby from said comparator means;

and logic switching means operatively connected to the binary counter means and said motor control circuit for operating the motor in alternative directions of rotation in response to a predetermined logical sequence of control output signals to thereby reversibly rotate the antenna to hunt and aim the antenna at an angular position at which the maximum signal strength of a selected station is received at said receiver.

2. The apparatus set out in claim 1, further comprising:

memory eraser means operatively connected to said memory means for erasing the maximum signal stored therein following aiming of the antenna at the angular position at which the maximum strength of a selected station is received and preventing production of a comparative signal while the instantaneous signal received by the receiver remains above a predetermined reference level.

3. The apparatus set out in claim 2 wherein said logic switching means is programmed to first initiate and continue rotation of the antenna when the instantaneous signal received by the receiver falls below the predetermined reference level, thereby deactivating said memory eraser means.

4. The apparatus set out in claim 2 wherein said logic switching means is programmed to first initiate and ative signal next falls below the predetermined threshold level;

to then againreverse the direction of rotation when the comparative signal again rises above the predetermined threshold level; and

finally to stop rotation of the antenna when the comparative signal next falls below the predetermined threshold level.

Claims

1. In combination with a high frequency broadcast signal receiving antenna rotatably mounted on a support; a reversible motor operatively connected between the support and antenna for selectively rotating the antenna so as to index the antenna for reception of a broadcast signal of maximum strength; a motor control circuit operatively connected to the motor selectively operable to cause the motor to rotate the antenna in opposite directions; and a receiver connected to the antenna; the improvement in an automatic control for the motor control circuit comprising: memory means connected to the receiver for continuously monitoring the strength of the instantaneous signal received thereby from the antenna, storing the maximum signal received and producing a comparative signal proportional to the difference in strength between the stored maximum signal and the instantaneous signal received thereby; comparator means operatively connected to said memory means for producing a first digital output signal in response to reception of a comparative signal above a predetermined threshold level and a second digital output signal in response to reception of a comparative signal below the predetermined threshold level; binary counter means operatively connected to said comparator means for counting two reversals of the digital output signal from said comparator means for producing alternate control output signals dependent upon the number of digital output signals received thereby from saiD comparator means; and logic switching means operatively connected to the binary counter means and said motor control circuit for operating the motor in alternative directions of rotation in response to a predetermined logical sequence of control output signals to thereby reversibly rotate the antenna to hunt and aim the antenna at an angular position at which the maximum signal strength of a selected station is received at said receiver.

2. The apparatus set out in claim 1, further comprising: memory eraser means operatively connected to said memory means for erasing the maximum signal stored therein following aiming of the antenna at the angular position at which the maximum strength of a selected station is received and preventing production of a comparative signal while the instantaneous signal received by the receiver remains above a predetermined reference level.

4. The apparatus set out in claim 2 wherein said logic switching means is programmed to first initiate and continue rotation of the antenna when the instantaneous signal received by the receiver falls below the predetermined reference level, thereby deactivating said memory eraser means; to next reverse the direction of rotation of the antenna in response to reception of a comparative signal at the comparator means above the predetermined threshold level; to continue such reversed rotation when the comparative signal next falls below the predetermined threshold level; to then again reverse the direction of rotation when the comparative signal again rises above the predetermined threshold level; and finally to stop rotation of the antenna when the comparative signal next falls below the predetermined threshold level.