GB2272341A - Programmable electronic tuner for collective TV aerials using analog memory - Google Patents

Abstract

Programmable channel filters are used in an electronic tuner for collective TV aerials, in which up to 8 channel filters (11 to 18) can be tuned to the same number of channels. It comprises a microcontrol (1), an EEPROM memory (3), a keyboard (2) and a display (4), as well as a dynamic memory device (8), which allow the user to change the selected filter states thus adapting to the conditions of each installation. The signal data are switched and directed by a selector (7) to the respective positions of the dynamic analog memory (8) to be sequentially transmitted to the filters. <IMAGE>

Description

2272341 LE ELECTRONIC TUNER FOR COLLECTIVE TV AERIALS The present

invention relates to a programmable electronic tuner for collective television aerials, in respect of the electronic tuning of the TV receiver channel f ilters f or all three television tuning bands, low VHF, high VHF and UHF. The channel f ilters with which the tuner is provided comprise varicap, diodes the capacity of which is adjusted to the required resonance value by applying a given voltage or "tuning signal', programmed in a memory and governed by a microcontrol.

A system is known (GB-2 187 906 -A) f or tuning resonant circuits with varicap diodes by applying specific bias-voltages to each such circuit, which are stored as binary codes in a memory device from which they are taken and directed by a microcontrol and converted by the relevant D/A converter. It is also common to have an inductance and varicap parallel resonant circuit structure with an earthed terminal, to which signal voltage is applied through a resistor.

The application of a specific tuning signal to each resonant circuit or tuning circuit allows filters to be made with unpaired varicaps and with components having a greater tolerance.

A microcontrol or logic circuit sequence is also known (ES515 591) for adjusting the tuning of each channel as follows: receiving and decoding the keyboard selected channel indication, taking from a non-volatile memory the programmed data prerecorded for each set by the manufacturer, directing the memory position f or the band and the channel to be tuned to, generating the tuning signals using a D/A converter and after being 2 amplified applying the same to the selected filter. The tuner of the said patent shares the same converter and amplifier for the various circuits that can be tuned to making up a single filter, switching for individual adjustment by means of switches that receive control signals from the logic circuit.

In known channel filter tuning digital systems, the signal data, that is to say the bias-voltages for each varicap, recorded in the memory device, have been previously defined by the manufacturer for the possible tuning of a single and given channel number. The changing of the memory signal data needs erasing and reprogramming means which requires the equipment to be sent to the manufacturer. As the numbers of tunable channels to receive pictures of the various broadcasts varies from one geographic area to another, the suppliers of amplifying sets for collective aerials have to have a range of adjusted sets in stock, each of which is appropriate for only a given area.

The programmable electronic tuner for collective TV aerials subject of the invention comprises a structure of two or more coupled tunable circuits in which each such circuit has a control input through which the same is individually applied the appropriate tuning voltage or signal.

An EEPROM memory device is programmed by the manufacturer, as binary signal data, with the appropriate bias-voltages for each tuning circuit and for each of the channel frequencies, and with data relating to the channel numbers and f ilter numbers, the assignment to a given channel number of a given filter number and the relevant bias-voltages thereof, one per tunable circuit for each channel, constituting the "filter state". The EEPROM memory device used, unlike the memories mentioned in the state of the art, allows the data to be erased and reprogrammed by electric impulses, and these operations can hence be carried out wherever the equipment is installed. This different characteristic of the J memory device used in the digital tuning system being described is convenient in that the channel data obtained af ter the tuning process carried out by the installer, after a preset time or by keyboard instruction, are incorporated onto the memory replacing the original factory data. There is thus no longer any need to supply sets having a different adjustment. A single kind can be used f or all geographic areas, without having to rely on the channel numbers to be tuned to. The site installer himself assigns a f ilter number to each channel and can restart the tuning process under other installation conditions, without the appliance having to be sent to the manufacturer, for instance, for replacement of one of the amplifier filters or for a fresh channel reorganisation, as would be required with current sets.

The user keys the channel numbers, the filter numbers and the filter state instructions into the microcontrol and that is the end of the tuning process. A display shows the selected channel number and the filter number with which it operates during the tuning process.

The programmed signals to tune the resonant circuits of a filter number in to the channel selected for such filter are directed by the microcontrol to a circuit developed to constitute a dynamic memory, with a plurality of outputs, each for a filter tunable circuit, that receives the same before they are applied, converted into analogue signals amplified up to the DC level required to bias a varicap diode.

The number of outputs required for the dynamic memory must be at least the product of the number of tunable circuits comprising a filter and the number of channel filters the amplifying set has, and excess outputs can be left unoccupied.

For economic reasons an amplifier-D/A converter set cannot be used for each output terminal. The number of converters has been reduced to the extent that the dynamic memory circuit storage and switching sequence time so allows, having to such end a selector which directs towards such dynamic memory the respective signals for each output, simultaneously switching as many outputs from such dynamic memory as there are converters in the set.

The programmed channel tuning process algorithm allows the microcontrol, because of the type of EEPROM memory used, to carry out the operations to reprogram a filter with another tuning frequency or channel if the installer should at any time decide to change the state of any one filter, keying in the new channel number to be tuned to and then continuously and automatically carrying out the tuning operation routine: taking the respective signal data programmed in the EEPROM memory, loading such data onto the converters, controlling the dynamic memory by means of a selector and applying signals suited to each of the selected filter tuning circuits, through the dynamic memory outputs. The user decides when to end tuning of all channels, reprograms the new channel assignment to the filters or new "filter state" in the EEPROM memory and the microcontrol begins with its permanent working cycle systematically loading onto the converters the data of each tuned channel and applying the same to the relevant filter until a new decision is made to change the filter state. The new filter state shall also remain in the EEPROM memory for a subsequent starting of the appliance, for instance after a power-cut or if the amplifying set is reinstalled, which memory shall start from the channels reprogrammed during the last tuning operation.

In order to prevent the same channel from being tuned to at the same time by more than one f ilter, the microcontrol compares the channel of the filter that is being operated in the tuning process described above, with the channels assigned to the remaining filters, rejecting such channel if it has already been assigned.

C S Figure i is the electrical diagram of the basic structure of a channel filter used.

Figure 2 diagrammatically shows a detailed view of the dynamic memory, with 32 outputs applied to the same number of tuning circuits in the programmable filters.

Figure 3 shows the digital tuning system of the circuits making up 8 channel filters.

Figure 4 is the flow diagram of the algorithm for tuning and reprogramming the filters.

i The figures show that the programmable electronic tuner for collective TV aerials, in accordance with a preferred embodiment of the invention, uses the known filter structure that appears in figure 1, which comprises four tunable varicap circuits (CR, to CR4), two before the amplifying stage and two others at the output, each of which is activated from the control line (R1 to R4) with a voltage (Vs, 1 to VS 4) or specific tuning signal programmed in the EEPROM memory (3) for each channel, initially by the manufacturer or subsequently by the installer, which EEPROM memory therefore has programmed as binary data the appropriate voltages to tune each channel with each of the filters and the filter state.

Since the number of programmable TV channels in a preferred collective aerial appliance is eight, as shown in figure 3 a dynamic RAM memory (8) is used which has 32 outputs (S1 to S32) to which the specific tuning signals are directed sequentially four by four by means of the selector (7).

For the simultaneous application of four adjustment signals to the same number of circuits of a same filter (11 to 18) four PIA converter (5) and amplifier (6) sets are used. The digital 6 programming system is governed by a microcontrol (1) that receives instructions from the installer via the keyboard (2). The tuning process is followed by the installer on the display (4) which shows at all times the filter number (11 to 18) being worked with and the channel number being tuned to.

The reprogramming and tuning sequence governed by the microcontrol (1) is shown in the flow diagram of figure 4: the decision to change a filter state or not is made at block (26). If it is not. the tuning routine will be repeated for each channel (blocks 23 to 25) with the initially selected filter: data loaded onto converters (5) at block (23), dynamic memory controlled by means of the selector (7) at block (24), relevant signals applied through the dynamic memory at block (25). If the decision is to change the state of a given channel, the new filter is selected at block (27), and the aforesaid tuning routine, shown at block (28), is then executed. Having definitively tuned the required channels, with the relevant instruction, block (29), EEPROM memory (3), stores the new assigned data, block (30), and the routine of block (28) is now repetitively executed in a "working position".

A 7 Referring to Fig.3 of the accompanying drawings, the dynamic memory 8 is an analogue memory capable of storing four analogue values for each channel filter as each channel filter includes four varicap-tuned circuits shown in Fig.1 as CR1, CR2, CR3, and CR4. The dynamic memory 8, being an analogue memory, requires that its-stored data be refreshed in order to avoid its loss. Data refresh is accomplished by the reading, at regular time intervals, of the four- parameter set of data for the filter 11, say, from the EEPROM 3 in digital form, converting the four-parameter set of digital data into a four-parameter set of analogue data in the D/A converters of the D/A converter set 5, amplifying the four-parameter set of analogue data in the amplifier set 6, using the selector 7 to select those storage elements of the dynamic memory 8 that are connected to the four varicap-tuned circuits of the filter 11 to receive the fourparameter set of analogue data and applying the four-parameter set of analogue data to those four storage elements.

The data refresh operation described above for those storage elements of the dynamic memory 8 that are connected to the filter 11 is repeated for each of the the storage elements of the dynamic memory 8 connected to the other filters 12 to 18.

The EEPROM 3 contains only eight four-parameter sets of digital data and can be reprogrammed by the circuit shown in Fig.3 shold it be found necessary to 6 change the eight sets of data in the EEPROM 3.

In the reprogramming of the EEPROM 3, the keyboard 2 is used to instruct the controller 1 that the EEPROM 3 is to be reprogrammed, to select a channel number to be associated with the first new four-parameter set of data and to select one of the eight filters 11 to 18 for which that new data will be used. The keyboard 2 is then used to instruct the controller 1 to execute an autotune routine during which the system is tuned to the lowestfrequency channel, say, available, the four-parameter set of analogue data required to achieve that tuning is digitised and the resulting four-parameter set of digital data is stored in the EEPROM at an address determined by the selected channel number along with data indicating which of the eight filters 11 to 18 is to receive that stored data.

The autotune routine described above is repeated for seven more channel numbers for which respective channels are found and filters allocated, at which time the keyboard 2 is used to instruct the controller 1 that the reprogramming of the EEPROM 3 is complete and the system returns to its tuning mode.

The system requires only four sets of D/A converters 5 and amplifiers 6 although it is capable of storing thirty-two pieces of analogue data. That is to say, the system requires the same number of D/A converters and amplifiers 6 as the number of parameters required to to tune each filter and the dynamic memory 8 requires that number of storage locations for each filter connected to It, 9 it.

The display 4 serves to inform the user of what is taking place.

/0 C L A 1 M S 1. - A PROGRAMMABLE ELECTRONIC TUNER FOR COLLECTIVE TV AERIALS, comprising a plurality of channel f ilters (11 to 18) each of which includes a number of tunable inductance and varicap circuits (CR, to CR4) in parallel, a microcontrol (1), a keyboard (2), a display (4) and a memory device (3) to store the programmed signal data, a small number of D/A converters (5) and amplifiers (6) generating, within a repetitive sequential process, the varicap DC bias-voltages (VS, to VS32) to tune the filters, characterised in that a selector (7) and a dynamic memory device (8) is provided for tuning and directing the signal data; the dynamic memory device (8) has a plurality of memory positions onto which, within the tuning process routine in each channel, all the signal data converted into bias-voltages (Vs, to VS32) are loaded before being applied to the respective filters, which memory positions correspond to each of the outputs (s, to S32) f or each tunable circuit (CR, to CR32) to which they are directed by the selector (7) during an uninterrupted sequential process.

2. - A PROGRAMMABLE ELECTRONIC TUNER FOR COLLECTIVE TV AERIALS, as in claim 1, characterised in that the memory device (3) to store the signal data is of the EEPROM kind and has stored in it all the signal data for all the f ilters and all the tunable frequency bands.

3.- A PROGRAMMABLE ELECTRONIC TUNER FOR COLLECTIVE TV AERIALS, as in the above claims, characterised in that after executing the tuning routine (blocks 23 to 25) it is established that the user can change or not the programmed f ilter state, selecting any one filter (11 to 18) to tune in to any TV channel using the keyboard (2) and following the process on the display (4), the said tuning routine being repeated with the data of the new filter state.

4. - A PROGRAM14ABLE ELECTRONIC TUNER FOR COLLECTIVE TV r i 0 11 AERIALS, as in the above claims, characterised in that the memory device (3) storing the signal data can be reprogrammed by the installer for the different filter states selected upon completion of the tuning process of all channels, such states remaining when the appliance is started subsequently and until they are again modified.

5.- A PROGRAMMABLE ELECTRONIC TUNER FOR COLLECTIVE TV AERIALS, as in claim 1, characterised in that the microcontrol (1) and the dynamic memory (8) have internal means to avoid tuning two filters to the same channel. by comparing the channel that is being tuned to with the channels tuned to by the remaining filters.

6. A programmable electronic tuner including N tunable channel filters, each requiring M tuning vol- tages, connected to data output ports of an analogue memory providing N groups of M storage locations, M digital-to-analogue (D/A) converters connected to data input ports of the analogue memory, an electrically erasable programmable digital memory (EEPROM) connected to the input ports of the D/A converters, the EEPROM providing storage locations for N groups of digital data of M words per group, and control means capable of tuning each channel filter and writing the tuning data as a group of M digital words into the EEPROM, the control means being capable of selecting each group of M digital words from the EEPROM, applying the M digital words to the D/A converter to provide M analogue voltages and of storing the M analogue voltages at a selected group of M storage locations in the analogue memory.

7. A programmable electronic tuner substantially as described herein with reference to, and as shown by, the accompanying drawings. 0