GB2033179A - R.F. signal selector - Google Patents

Abstract

A channel selecting device is arranged to store in respective memories 36 and 37 tuning information and aerial rotation information for each selected channel. The desired channel is selected using a keyboard 32 and the information for that channel is read out, the aerial rotation data being converted to a d.c. signal for comparison with a signal representing the actual aerial position to control an aerial servo motor system 1 to 8 Figure 1. <IMAGE>

Description

SPECIFICATION R.F. signal selector The present invention relates to a circuit arrangement for selecting a r.f. signal from a range of r.f.

signals.

It is usual nowadays to fit signal receivers for domestic use, for example radio receivers or television sets, with memory devices by means of which it is possible to store information relative to the tuning of a certain number of preferred transmitted frequencies, so as to be able, afterwards, to reestablish the tuning of the same transmitted frequencies rapidly under manual control.For example, television sets are normally fitted with a varicap diode tuning group, i.e. voltage controlled, and with a memory for 12 or 16 channels, which memory can be of two types: a mechanical memory, in which a potentiometer, associated with every channel that can be stored, regulates and stores the tuning voltage, and a key or push-button enables channel recall; oran electronic memory ofthe semiconductortype in which at least one memory cell is associated with every channel so as to store, in binary form, a number which corresponds either to the tuning voltage (voltage synthesis) or to the signal frequency (frequency synthesis), as well as" the usual selection key or push-button.

Further details of the systems in use can be found for example in: "Monolithically integrated FM front-end with new diode tuning concept" by H.

Rinderle & W. Beckenbach, IEEE Transactions on C.E. 4, November 1975; "Sendersuchlauf mit elektronischer Speicherung" by W. Baum, Funkschau 12, 1977; "A frequency synthesizer for television receivers" by E. G. Breeze, Transactions BTR, November 1974; "Digital television tuner uses MOS LSI and non volatile memory" by L. Penner, Electronics, 1st April 1976.

Naturally it is always necessary to associate the receiver with a device that picks up signals, i.e. an antenna, which, in the case of a television set or of a F.M. receiver, should be directional. Nowadays, because of the multiplicity of television transmitters the use of rotating directional antennas has become so common that it is possible, by means of only one antenna, to receive all the channels that can be received in the area. Rotation of such antennas, which are usually installed on the roof of a building, can be controlled by the user by means of appropriate remote control devices; however it is inconve- nient to have to change the angular position of the antenna every time tuning to another channel is desired.It is known to automate the search for optimum antenna position (see for example the article "Automatische Antennenrotor-Steuerung" by H. Mueller Funkschau 5 1978); however this is a lengthy procedure which requires the antenna to perform a complete rotation everytime and then go back to the optimum position.

It is also known, see for instance published German Patent Application DOS 1.954.699; to combine in only one mechanical control the commands of two potentiometers storing respectively informå- tion related to the tuning of the selected channel and the information related to the optimum orientation of the aerial position for the-reception of said channel. Nevertheless, this'solution encounters problems with device reliability, since the mechanical contacts wear by use until they can cause often the failure of the whole device.In addition; given the increasing number of preselected channels which the user wishes to have available, the need to provide two potentiometers for every command causes a considerable complication in constructing the device, as well as somewhat increasing the cost.

:According to the present invention, there is provided a circuit arrangement for selecting a r.f. signal from'a range of r:f. signals that can be received by a signal receiver in association with a locatable device that picks up r.f. signals, the circuit arrangement' comprising: memory means for storing information relative to the tuning of a certain number of preferred signals; means for recalling the said information from the said memory means so as to reestablish the tuning of one of the said preferred signals under manual'control; means for storing, for each such preferred signal, information relative to the optimum angular position of the locatable device-for that preferred signal; and means for producing signals for causing the- locatable device to attain the approp riateangularposition when a preferred signal is recall'ed; wherein the memory means comprise cells ofa semiconductor memory in which both the tuning and angular position information are stored in the form of binary numbers.

-The invention will now be described with reference to a non-iimiting example illustrated in the accompanying drawings, in which : Figure 1 shows the electrical schematic of a known circuit arrangement, fitted with a mechanical memory, for the selection of signals.

Figure 2 shows the electrical schematic of a circuit arrangement, fitted with electronic memory, for the selection of signals and embodying the present invention.

In Figure 1, number 1 identifies awide-band rotating receiving antenna, for the television V-band (610-860 MHz); number2 identifies a d.c. electric motor, the rotor of which is identified by number 3 and is mechanically coupled to antenna 1 and to the slider of rheostat 4.

Rheostat 4 is inserted in-a bridge, the junctions of which are identified by letters A, B, C, D; the bridge consists, besides rheostat 4, of resistors 5 and 6 and of a second rheostat contained in tuning group 21 and connected across junctions A and B.

Junction D is connected-to the circuit ground; to junction A is applied a +V supply voltage; the voltage available across the C-B arm is applied to the + and - inputs of differential amplifier 7, the output of which, by means of power amplifier 8, controls motor 2.

Tuning group 21 'is of the mechanical memory type with potentiometers and includes a certain number of conventional type selection push-buttons incorporating tuning control knobs for the control of the corresponding tuning potentiometer; for simplicity, two such push-buttons (11 and 12) only are shown in the figure, although it is obvious that any number can be provided.

Push-button 11 controls, when pressed, the closing of switches 10 and 13 and, when rotated, the position of the slider of tuning potentiometer 9; the voltage thus present at the said slider is available, via switch 10 which is closed, at terminal Vv, from which it is applied to the varicap diodes of the tuner proper, which is not shown in the figure and can be of any of the known types on the market.

Closing of switch 13, on the other hand, connects junctionsAand B of the bridge to reheostat 12; the position of the slider of rheostat 12 is controlled by the user by means of thumb-wheel 14.

In this way the user who wishes to store a certain television channel by associating it to push-button 11, carries out the following procedure: - Press push-button 11; - Rotate push-button 11 so as to obtain the best tuning; - Rotate thumb-wheel 14 so as to obtain the optimum antenna angular position; such position is in fact uniquely determined by the position of the slider of rheostat 12, which, via switch 13 which is closed, constitutes the arm of the bridge opposite to that formed by rheostat 4, so that the motor, which is controlled by the voltage present on diagonal C-B, rotates, depending on the polarity of the said voltage, in the right direction to bring the bridge into balance.

Thereafter, each time the user presses pushbutton 11, he will reobtain the same channel, with the tuning that was previously chosen and the antenna will automatically rotate to reach the angular position that was previously chosen. Operation of push-button 17, thumb-wheel 20, switches 16 and 19, potentiometer 15 and rheostat 18 is exactly the same as that described for push-button 11; so is the operation of all the other push-buttons which are not shown in the Figure.

The above described known circuit arrangement suffers, as already mentioned, from drawbacks due to the mechanical realization of the means for memorizing the information related to the tuning and to the angular position of the rotative aerial.

Figure 2 shows the circuit arrangement of an embodiment of the present invention, using electronic memory and frequency synthesis channel selection. For simplicity, Figure 2 does not show the antenna, the electric motor and amplifiers 7 and 8; terminals + and - which are on the right hand side of Figure 2 are the inputs of amplifier 7; potentiometer 44 in Figure 2 is taken to be mechanically coupled to the rotor of motor 2 of Figure 1.

In Figure 2, numbers 30 and 31 identify two rotary thumb-wheel switches which are used to set the number of the channel to be selected (it is known that every television channel is identified within a frequency allocation standard by a number: for example, in the C.C.I.R. standard, the UHF channels are identified by numbers 21 to 69; in the America standard, the UHF channels are identified by numbers 14to 83).

In Figure 2, number 32 indicates a keyboard with 16 keys numbered 1 to 16 for recalling the stored channels; number 33 identifies a push-button for the storage of a tuned channel; number 34 and 35 identify two push-buttons connected in a known way via OR gate 41 to the clock input of 6 bit UP/DOWN counter 42; push-button 34 is also connected to the UP/DOWN control input of the counter; each time push-button 34 is pressed, the counter increments its content by one, whereas each time push-button 35 is pressed the counter decrements its content by one.

Keyboard 32 supplies a 4 bit address to a nonvolatile 16 X 7 RAM memory 36 which is used to store the channel number associated with each key of keyboard 32; the same keyboard also supplies a 4 bit address to a second non-volatile 16 X 6 RAM memory 37 which is used to store a 6 bit binary number which corresponds to the antenna optimum position for that channel.

A BCD/Binary converter 43 receives two 4 bit data words from the two rotary thumb-wheel switches 30 and 31 and feeds memory 36 with the data converted into 7 bit binary form; them memory also receives an enable pulse at its control input RNV from the store push-button 33 and addresses read-only memory 38 (ROM 10 OX 16) with a 7 bit data word.

Memory 38, in turn, supplies thirteen bits to the tuner frequency control system (not shown in the Figure) which contains according to known techniques, a prescaler, a programmable divider, a phaselocked loop, a V.C.O.; this system is indicated in the Figure by "PLL".

Memory 38 also supplies three bits for band switching to the relative circuits not shown in the Figure and symbolicaily identified by letters BA.

Memory 37 receives the store pulse from the output of gate 41 and supplies a 6 bit data word to buffer 39 which receives the + V supply voltage and presents six outputs connected to a typical digital/ analogue conversion network of the R/2Rtype identified by 40.

The +V voltage is also applied to the terminals of potentiometer 44, which replaces rheostat 4 of Figure 1 and which is mechanically coupled to the rotor of motor 2; the slider of the said potentiometer is connected to the + input of amplifier 7, whilst the output of the R/2R network is connected to the input of the same amplifier. The circuit described operates in the following way.

A user who wants to store a channel should carry out the following procedure: - On keyboard 32, press the key to which he wishes to allocate the channel; this action chooses one of the sixteen memory cells in memories 36 and 37; - By means of rotary thumb-wheel switches 30 (tens) and 31 (units) set the number of the desired channel and press store push-button 33; this action stores the selected number in the chosen cell of memory 36; due to the fact that when push-button 33 is released, memory 36 goes into READ, the data enters ROM 38 and the image corresponding to the chosen channel appears on the television screen: - Find the optimum antenna position by means of push-buttons 34 and 35; the number counted by counter 42 is automatically stored in the chosen cell of memory 37 whilst converter 40 supplies at its output the corresponding voltage and the antenna assumes a position such that the voltage on the wiper of potentiometer 44 is equal to the voltage at the output of the converter.

At this point all storage operations have been carried out and each time the user wishes to select the same channel again, he only has to press the corresponding key on keyboard 32; memory 36 supplies at its output the channel number, allowing the tuning system to tune in to the exact corresponding frequency, and memory 37 supplies at its output the count which indicates the optimum antenna position.

Advantages clearly result from the above, advantages which are particularly evident when the receiver is fitted with a remote control for recalling stored transmitter frequencies.

Many variations can be made without, however, departing from the scope of the present invention as defined in the appended claims. For example, if the receiver is already fitted with a micro-processor in order to control the selection of the transmitter frequencies and/ar other functions (like for example the regulation and storage of the levels of analogue signals like volume, brightness, colour, etc.) it is sufficient to modify the micro-processor programme, using a memory of bigger capacity and possibly an additional D/A converter or modifying the existing converter, to allow the realization of the circuit arrangement.

Claims (7)

1. A circuit arrangement for selecting a r.f. signal from a range of r.f. signals that can be received by a signal receiver in association with a locatable device that picks up r.f. signals, the circuit arrangement comprising: memory means for storing information relative to the tuning of a certain number of preferred signals; means for recalling the said information from the said memory means so as to reestablish the tuning of one of the said preferred signals under manual control; means for storing, for each such preferred signal, information relative to the optimum angular position of the locatable device for that preferred signal; and means for producing signals for causing the locatable device to attain the approp riate angular reaction when a preferred signal is recalled; wherein the memory means comprise cells of a semiconductor memory in which both the tuning and anular position information are stared in the form of binary numbers.

2. A circuit arrangement according to claim 1, and comprising a number of keys or push-buttons, each for controlling the recall of a respective deter mined transmitter frequency previously chosen.

3. A circuit arrangement according to claim 1 or 2 wherein the angular position information is repre sented in the signal producing means by a d.c.

voltage.

4. A circuit arrangement according to claim 3, wherein said signal producing means comprises a resistor bridge, one arm of which includes a variable resistor the value of which is function of the angular position at the device that picks up r.f. signals, and means for controlling the current supplied to a motor for setting the angular position according to the voltage across one of the bridge diagonals.

5. A circuit arrangement according to any one of the preceding claims, when incorporated in a television set fitted with a remote control device for recalling from memory the desired channel that had been previously stored and which comprises means such that the said recall automatically produces also the positioning of the device that picks up r.f. signals according to the position previously stored for that channel.

6. A circuit arrangement according to any one of the preceding claims, when incorporated in a receiver having a microprocessor provided for controlling one or more functions of the receiver, the microprocessor having said electronic memory means associated therewith so as to store both the items of information related to one of the preferred signals and recall the items pertaining to a preferred signal by means of a single command.

7. A circuit arrangement for selecting a r.f. signal constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.