TUNING APPARATUS AND A METHOD

Abstract: A circuit of a tuning device for tuning a radio transceiver, the circuit comprising a variable impedance device (14), which consists of a pair of variable resistors having an open circuit between their tracks, the "wiper arm" (14a) of which is connected to a voltage controlled oscillator (VCO) (15). The voltage controlled oscillator may suitably comprise a CMOS 4046 integrated circuit. The voltage controlled oscillator outputs a stream of pulses, having in this case a 1:1 mark: space ratio, to the transceiver units micro-computer (not shown). At the centre point of the tracks of the variable impedance device (14) there is a null position corresponding to an open circuit. As the user turns a dial this centre position is indicated by a notch. As the wiper arm is moved from the centre position towards either extent, the value of the voltage at the VCO terminal (15a) increases. Because of this the rate of production of pulses, i.e. the frequency of the pulse stream output by the VCO (15), increases accordingly. Each pulse represents an increment or decrement of the frequency to which the radio transceiver (not shown) is tuned.

Description: TUNING APPARATUS AND A METHOD This invention relates to tuning apparatus and a method of tuning and is concerned particularly, although not exclusively, with tuning apparatus and a method of tuning for use with a receiver of electromagnetic radiation. Modern radio receivers, and combined receivers and transmitters (known as transceivers) are digitally tuned to the desired radio frequency by an in-built micro computer which, when the desired radio frequency is reached, locks the digital tuner to that particular frequency. A known radio transceiver permits a user to manually scan through the receivable range of frequencies by turning a dial, until the desired frequency is reached, whereupon the tuner will be "locked" to that frequency by the micro computer. The dial works by generating a series of electronic pulses which are detected by the micro computer. Each pulse is ascribed a particular value corresponding to a change in frequency. For example each pulse may represent 10 Hz, and as the dial is manually turned to produce a stream of pulses, each pulse fed to the micro computer will cause the micro computer to increment or decrement the tuned frequency by 10 Hz. The rate of generation of the pulses is directly proportional to the rate of turning of the dial. The user continues to turn the dial until the transceiver is tuned up or down to the desired frequency and knows when the desired frequency has been reached by observing a digital display on the apparatus which indicates the frequency to which the transceiver is tuned. The value in hertz of each of the pulses generated by the tuning of the dial can be varied. For example if the user wishes to change the tuned frequency by a large amount, eg. by several hundred kilohertz, the pulses can be ascribed a value of a 100 Hz. This reduces the time taken to tune the transceiver to the desired frequency. In addition, the number of turns of the dial necessary to produce the required number of pulses is reduced. When for example the user has tuned the transceiver to within a few kilohertz he might ascribe to the pulses a lower frequency value to enable more accurate tuning to the desired frequency. This alteration of the size of the steps taken by the digital tuner is typically made by pressing an appropriate button on the front of the transceiver. The value of each pulse might be variable by factors of 10 between, say 5 Hz and 5 KHz. Despite being able to vary the steps taken by the digital tuner as it progresses through the range of tunable frequencies it can still take a relatively long time to reach the desired frequency, particularly if the frequency must be changed by a few megahertz. A more advanced prior apparatus uses a multi vibrator to generate automatically the pulses. Whilst the range of frequency of pulse generation provided by a multi vibrator is sufficient for most "broadcast band" receiving applications, a transceiver requires a much broader frequency range of pulse generation. For example, where in a broadcast band receiver a minimum step size of around one KHz might suffice, a transceiver for use by a radio enthusiast would typically require a minimum step size of around one Hz. A multi vibrator would not provide such a broad variation. According to a first aspect of the present invention there is provided tuning apparatus for tuning the reception of receiving apparatus, which receiving apparatus is arranged to receive electromagnetic radiation, the tuning apparatus being arranged in use to change the frequency of electromagnetic radiation to which the receiving apparatus is tuned by automatically incrementing or decrementing said frequency, wherein the tuning apparatus comprises means to alter the rate at which said frequency is changed. Preferably the tuning apparatus is arranged in use automatically to increment or decrement the frequency to which the receiving apparatus is tuned by automatically supplying to a micro computer of the receiving apparatus a number of electronic pulses, each of which pulses causes the micro computer to change said frequency by a predetermined number of cycles per second, the means to alter the rate at which said frequency is changed comprising means to alter the rate at which said pulses are supplied to said micro computer, wherein the apparatus includes pulse generation means arranged to generate the pulses, which pulse generation means comprises a voltage- controlled oscillator. Preferably the tuning apparatus is arranged in use to tune the reception of receiving apparatus which is arranged, in use, to receive radio signals. The voltage-controlled oscillator may be arranged to generate pulses at a variable rate. Preferably the rate at which the voltage controlled oscillator generates the pulses is controlled by the setting of a variable impedance device. The variable impedance device may comprise one or more variable resistors. In a preferred arrangement the rate at which the pulses are generated may be altered by movement of a contact arm of the variable impedance device. Preferably the variable impedance device comprises a pair of variable resistors having a common contact arm. The tuning apparatus may be arranged to increment the frequency to which the receiving apparatus is tuned when the contact arm of the variable impedance device is located on a first side of a null position. Alternatively or additionally, the tuning apparatus may be arranged to decrement the frequency to which the receiving apparatus is tuned when the contact arm of the variable impedance device is located on a second side of a null position. The tuning apparatus may include sensing means arranged in use to sense on which side of the null position the contact arm of the variable impedance device is located. Preferably the variable impedance device comprises a potentiometer, the contact track of which is split into first and second portions which portions are electrically isolated from each other at a position corresponding to a null position, wherein a contact arm of the potentiometer is arranged in use to movably contact either the first or second track portions or to contact the electrically isolated portion therebetween at a first end, and at a second end is electrically connected at least indirectly to ground, the first and second track portions being electrically connected respectively to first and second switching means, such that when the contact arm is made to contact one of the track portions, a voltage is provided to the voltage-controlled oscillator, the magnitude of the voltage being dependent upon the position of the contact arm on the track portion. At least one of the first and second switching means may comprise a transistor. In a preferred arrangement the tuning apparatus is located remote from the receiving apparatus and may be electrically connected thereto by means of a cable. The cable may be arranged to be received in a socket on a case of the receiving apparatus. According to a second aspect of the present invention there is provided a method of changing the frequency of electromagnetic radiation to which receiving apparatus is tuned, the method comprising automatically incrementing or decrementing said frequency and altering the rate at which the frequency is changed, wherein the method comprises automatically supplying a number of electronic pulses to a micro computer of the receiving apparatus, each pulse causing the micro computer to increment or decrement the frequency to which the receiving apparatus is tuned, wherein the method comprises altering the rate at which the pulses are supplied to the micro computer to alter the rate at which the micro computer increments or decrements the frequency, characterised in that the method includes controlling the voltage applied to a voltage-controlled oscillator to vary the rate at which the pulses are supplied to the micro computer. Preferably the method comprises varying the rate at which the pulses are supplied to the micro computer by adjusting the impedance of a variable impedance device. In a preferred arrangement the method includes varying the rate at which the pulses are supplied to the micro computer by moving a contact arm of the variable impedance device relative to a null position. The invention also includes tuning apparatus substantially as herein described when used in a method substantially as herein described. The invention also includes receiving apparatus when used with tuning apparatus substantially as herein described or when used in a method substantially as herein described. The invention may include any combination of the features or limitations referred to herein. An embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 shows a conventional radio transceiver unit; Figure 2 shows, schematically, a circuit of a tuning device for use with a transceiver unit of Figure 1; Figure 3 shows a transceiver unit with the tuning device of Figure 2 connected; and Figure 4 shows in more detail a potentiometer arrangement of the apparatus of Figures 1 to 3. Referring particularly to Figure 1, this shows in basic form a conventional radio receiver unit 10 comprising a casing 11 and a digital display 12 which is, in use, arranged to indicate, among other things, the frequency to which the transceiver is tuned. A dial 13 is provided which, in prior art transceivers, is used to manually change the frequency to which the transceiver is tuned. This is achieved by continually rotating the dial which causes pulses to be generated at a rate proportional to the rate of turning of the dial. The pulses are ascribed a particular value of frequency step-size, such that for example each pulse may represent a step of 50 Hz, and the micro computer increments or decrements the frequency to which the transceiver is tuned by the step- size for each of the pulses it receives. The direction of tuning, ie. an increment or decrement of frequency, is selected by the direction (ie. clockwise or anticlockwise) in which the dial 13 is turned. Turning to Figure 2, this shows, schematically, a circuit of a tuning device according to an embodiment of the invention for use in tuning the transceiver of Figure 1. The circuit comprises a variable impedance device 14, which consists of a pair of variable resistors having an open circuit between their tracks, the "wiper arm" 14a of which is connected to a voltage controlled oscillator (VCO) 15. The voltage controlled oscillator may suitably comprise a CMOS 4046 integrated circuit. The voltage controlled oscillator outputs a stream of pulses, having in this case a 1:1 mark:space ratio, to the transceiver units micro computer (not shown) . The mark:space ratio may be altered for different types of equipment. These pulses replace the pulses created manually in the prior art apparatus by the turning of the dial 13. At the centre point of the tracks of the variable impedance device 14 there is a null position corresponding to the open circuit. As the user turns a dial (described below in relation to Figure 3) this centre position is indicated by a notch. When the contact arm is in contact with the portion of either track closest to the centre "off" position a low voltage appears at the VCO 15 (via the wiper-arm 14a) . The value of this low voltage is determined by the value of the variable resistor R v , which sets the "law" of the variable impedance device 14. As the wiper-arm is moved from the centre position towards either extent, the value of the voltage at the VCO terminal 15a increases. Because of this the rate of production of pulses, ie. the frequency of the pulse stream output by the VCO 15, increases accordingly. The maximum frequency of the pulse stream output by the VCO 15 may exceed 1 megahertz, although the speed at which the micro computer is able to accept pulses will in some cases limit the speed of tuning. In practice the variation in the rate of generation of pulses may allow the frequency- changing steps to be made at a rate of one every few seconds up to a rate of several thousand per second. Transistor switches 16 and 17 detect the side of the centre position on which the wiper arm 14 is located. The switches activate an ENABLE circuit which in use activates an UP/DOWN sensing device 19. The UP/DOWN sensing device 19 sends either an UP signal or a DOWN signal to the micro computer in response to the location of the wiper arm 14a in relation to the centre position. This determines in which direction the micro computer changes the frequency, ie. an increment or a decrement of frequency with every pulse from the VCO 15. Referring also now to Figure 3, this shows a similar transceiver unit 10 to that of Figure 1, with the addition of a tuning device shown generally at 20 according to an embodiment of the present invention. The tuning device 20 comprises a case 21 in which is housed the circuit of Figure 2. On the outside of the case 21 is located a dial 22 which, in use, is turned by a user to effect movement of the wiper arm 14a of the variable impedance device 14 (shown in Figure 2) . The tuning device 20 is electrically connected to the transceiver unit 10 by a cable 23 which, in this embodiment, conveniently plugs in to a socket 24 on the case 11 of the transceiver unit 10. The dial 22 has a centre-null position (not shown) which may be recognised by a user as a small notch in the tracks of the variable impedance device 14. When the dial 22 is in the centre-null position, no pulses are generated by the VCO 15 and hence the microcomputer (not shown) of the transceiver unit 10 does not change the frequency to which it is tuned. When it is required to change the frequency to which the transceiver unit 10 is tuned, a user simply turns the dial 22 to either side of the centre position. The direction of tuning of the dial 22 ie. either clockwise or anti-clockwise determines whether the tuned frequency is changed upwardly (ie. increasing frequency) or downwardly (ie. decreasing frequency) . Furthermore, the extent to which the dial 22 is turned away from the centre position will determine the rate at which the tuned frequency is either incremented or decremented. This is achieved because the extent to which the wiper arm 14a of the variable impedance device 14 is moved along the track away from the centre position determines the voltage experienced at the VCO 15, which in turn determines the rate of output of pules which pulses are interpreted by the micro-computer as increments or decrements in the tuned frequency. Hence the further the dial 22 is turned the faster will be the change in the tuned frequency, up to a given maximum. A user can therefore change the frequency to which the transceiver unit 10 is tuned, either upwards or downwards, at a rate of his choosing without constantly having to rotate the dial 13 on the front of the transceiver case 11. In addition, once the apparatus is set either incrementing or decrementing the tuned frequency the user can advantageously remove his hands from the apparatus until the desired frequency is reached. Referring to Figure 4, this shows in more detail an embodiment of potentiometer arrangement for use in the apparatus. Base connections of PNP transistors 25 and 26 are connected to ends of track portions 27a and 27b of split track potentiometer 27. When contact arm 28 is in the central "null" position (shown) , no voltage appears at the collector of either transistor, however a voltage appears between either base connection and ground. When the contact arm 28 makes contact with, for example, track portion 27a, the current drain from the base of transistor 25 will switch on this transistor and a voltage close to +V will appear at its collector. This voltage is used to enable the VCO circuit which then produces pulses at a rate dependent upon the actual voltage at the contact arm 28. This voltage will never be close to zero when the VCO is enabled, because of the presence of variable resistance 29 in the resistance path from transistor 25 or 26 to ground. This does not present any problem to the minimum frequency of the VCO as the frequency range is set by other inputs to the VCO integrated circuit (not shown) . The voltage at the collector of 25 is used to determine whether the pulses generated by the VCO are either incremental or decremental to the frequency of reception/transmission of the apparatus. The above described arrangement permits a potential dynamic range of step size of more than one million to one, using a single split track potentiometer to control the VCO. In the embodiment described above the tuning device 20 is electrically connected to the transceiver 10 by plugging cable 23 into socket 24 on the case 11 on the transceiver 10. With suitable adaptation, a microphone socket (not shown) of the transceiver unit 10 could be made to receive the cable 23, thereby avoiding the need for an extra socket on the case 11. It will be understood that, whilst the tuning device has been described as a separate unit to the transceiver unit 10, it could equally be made to integrate with the transceiver unit 10 within the case 11.

Claims: CLAIMS 1. Tuning apparatus for tuning the reception of receiving apparatus, which receiving apparatus is arranged to receive electro-magnetic radiation, the tuning apparatus being arranged in use to change the frequency of electro-magnetic radiation to which the receiving apparatus is tuned by automatically incrementing or decrementing said frequency, wherein the tuning apparatus comprises means to alter the rate at which said frequency is changed. 2. Tuning apparatus according to claim 1 wherein the tuning apparatus is arranged, in use, to tune the reception of receiving apparatus which is arranged, in use, to receive radio signals. 3. Tuning apparatus according to claim 1 or claim 2 wherein the tuning apparatus is arranged in use to automatically increment or decrement the frequency to which the receiving apparatus is tuned by automatically supplying to a micro-computer of the receiving apparatus a number of electronic pulses, each of which pulses causes the micro-computer to change said frequency by a predetermined number of cycles per second. 4. Tuning apparatus according to claim 3 wherein the means to alter the rate at which said frequency is changed comprises means to alter the rate at which said pulses are supplied to said micro-computer. 5. Tuning apparatus according to claim 3 or claim 4 wherein the tuning apparatus comprises a pulse generation means which is arranged to generate the pulses. 6. Tuning apparatus according to claim 5 wherein the pulse generation means comprises a voltage controlled oscillator. 7. Tuning apparatus according to claim 6 wherein the voltage controlled oscillator is arranged to generate pulses at a variable rate. 8. Tuning apparatus according to claim 6 or claim 7 wherein the rate at which the voltage controlled oscillator generates the pulses is controlled by the setting of a variable impedance device. 9. Tuning apparatus according to claim 8 wherein the variable impedance device comprises one or more variable resistors. 10. Tuning apparatus according to claim 8 or claim 9 wherein the rate at which the pulses are generated may be altered by movement of a contact arm of the variable impedance device. 11. Tuning apparatus according to any of claims 8 to 10 wherein the variable impedance device comprises a pair of variable resistors having a common contact arm. 12. Tuning apparatus according to claim 8 wherein the variable impedance device comprises a potentiometer, a contact track of which is split into first and second portions, which portions are electrically isolated from each other at a position corresponding to a null position, wherein a contact arm of the potentiometer is arranged in use to movably contact either the first or second track portions or to contact the electrically isolated portion therebetween at a first end, and at a second end is electrically connected at least indirectly to ground, the first and second track portions being electrically connected respectively to first and second switching means, such that when the contact arm is made to contact one of the track portions, a voltage is provided to the voltage controlled oscillator, the magnitude of the voltage being dependent upon the position of the contact arm on the track portion. 13. Tuning apparatus according to claim 12 wherein at least one of the first and second switching means comprises a transistor. 14. Tuning apparatus according to any of claims 10 to 13 claim 11 wherein the tuning apparatus is arranged to increment the frequency to which the receiving apparatus is tuned when the contact arm of the variable impedance device is located on a first side of a null position. 15. Tuning apparatus according to any of claims 10 to 14 wherein the tuning apparatus is arranged to decrement the frequency to which the receiving apparatus is tuned when the contact arm of the variable impedance device is located on a second side of a null position. 16. Tuning apparatus according to claim 14 or claim 15 wherein the tuning apparatus includes sensing means arranged in use to sense on which side of the null position the contact arm of the variable impedance device is located. 17. Tuning apparatus according to any of the preceding claims wherein the tuning apparatus is located remote from the receiving apparatus. 18. Tuning apparatus according to claim 17 wherein the tuning apparatus is electrically connected to the receiving apparatus by means of a cable. 19. Tuning apparatus according to claim 18 wherein the cable is arranged to be received in a socket on a case of the receiving apparatus. 20. Tuning apparatus substantially as herein described with reference to the accompanying drawings. 21. A method of changing the frequency of electro¬ magnetic radiation to which receiving apparatus is tuned, the method comprising automatically incrementing or decrementing said frequency and altering the rate at which the frequency is changed. 22. A method according to claim 21 comprising automatically supplying a number of electronic pulses to a micro-computer of the receiving apparatus, wherein each pulse causes the micro-computer to increment or decrement the frequency to which the receiving apparatus is tuned. 23. A method according to claim 22 wherein the method comprises altering the rate at which the pulses are supplied to the micro-computer to alter the rate at which the micro-computer increments or decrements the frequency. 24. A method according to claim 22 or 23 including controlling the voltage applied to a voltage controlled oscillator, to vary the rate at which the pulses are supplied to the micro-computer. 25. A method according to any of claims 21 to 24 comprising varying the rate at which the pulses are supplied to the micro-computer by adjusting the impedance of a variable impedance device. 26. A method according to claim 25 including varying the rate at which the pulses are supplied to the micro¬ computer by moving a contact arm of the variable impedance device relative to a null position. 27. A method substantially as herein described with reference to the accompanying drawings. 28. Apparatus as claimed in any of claims 1 to 20 when used in a method according to any of claims 21 to 27.

Inventors: HOLDEN ROBERT, HOLDEN, ROBERT
Applicants: HOLDEN ROBERT, HOLDEN, ROBERT
Application year: 1993
Main classification: H03J1
IPC codes: H03J1