Automatic tuning method of double conversion tuner

The present invention is directed to a method for automatically Ab vote and to a circuit arrangement of a Doppelüberlagerungs- Television receiver, in particular to a method for automatically tuning and a circuit arrangement of a double conversion television receiver, in which a deviation of the image / sound carrier wave of the double overlay approximately television receiver selected transmission channel corresponding Tuning voltage is applied to a voltage controlled oscillator, so another vote takes place, so that the originating from the input filter Damping based on the image / sound carrier wave is minimal, according to the Oberbegrif fen of the independent claims 1 and 8. FIG.

Generally uses the receiving part in a television receiver, a Number of built-in tuners with mixers to signals within a number receiving of TV frequency bands. For example, a first tuner selects ei NEN transmission channel within the VHF television frequency band (54-88 and 174- 216 MHz) and a second tuner a transmission channel within the UHF-TV Frequency band (470-890 MHz). If a television receiver and the remote cable sehsignal CATV can receive is, a receiving system for this Si should signal to be added to a third tuner and mixer.

A double superheterodyne reception system for receiving VHF and UHF TV TV broadcasting signals (air insulation) to avoid the complexity of a number of tuners and the problem of the immense costs involved is under entitled "High Capacity TV" by DL in arch on consumer electronic IEEE manual CE-24, 1st Edition, February 1978 page 39-46, describes. Nevertheless, a composed Need for a simple and cheap receiver system for the reception of VHF-TV, UHF TV and CATV signals.

For this purpose, a receiving section until now is how the technical content of the US- 4408348 can be seen, with a control unit for He generating a tuning signal provided, the size of the frequency selected channel is set; further comprising a first filter element for Off selection of the high-frequency signal (HF) corresponding to the band from a first (low ribbon) with the low-frequency portion of the first cable band (MB-CATV) and a first broadcast band (L-VHF) selected channel corresponds, in pendency of said tuning signal; a second filter element for selecting the RF Signal to a second reception band (high band) with the obe ren frequency range of the first cable band (MB-CATV), a second round radio tape (H-VHF) and finally the low part of the second cable band (SB-CATV) depending on the tuning selected channel ent speaks; continued from an assembly to select a filter which first the Filter working sets when the selected channel in the first reception band (low band), and activates the second filter when the selected channel in the two th reception band (high band) is; and finally of several Abstimmsyste MEN, which as a result of the signal from the RF signal of the first broadcasting band, first cable tape, of the second broadcast band and the second tow band an intermediate frequency signal (ZF) produced.

The control unit generates a tuning signal, the magnitude of the frequency of the selected channel is determined.

The first filter selects that of high-frequency signal to the un from the direct frequency range of the first cable band and the first reception band selected with the first broadcast band, depending on the tuning signal Channel corresponds.

The second filter selects the one high frequency signal from the first cable band, the second radio and the second reception band in Ab pendence from the tuning selected channel corresponds.

The device for selection of the filter operates the first filter when the attached selected signal within the first reception band is, and the second filter, if the selected channel is on the second reception band.

A single superheterodyne receiver with capacitance diode for receiving the Broadcast spectrum used in the television broadcast. Since the capacity of the diode a voltage controlled oscillator (VCO) applied tuning voltage with those which anzule to the varactor diode of a Hochfrequenzabstimmkreises is gene, is identical, it is in a single superheterodyne receiver with capaci tätsdiode possible ABZU the entire tuner with a single tuning be right.

Nevertheless double super-heterodyne receivers should be used to the circular radio spectrum use. This is particularly advantageous when several input signals rer species in relation to the input signals of single superheterodyne receivers with capacitance diode and high-frequency signals. According to the nature of the Double conversion tuner, the tuning voltages to the capaci tätsdioden the VCO and the RF tuning circuit differently.

Since VCO and RF tuning of the double superheterodyne receiver on unterschiedli che frequencies are matched, if different tuning voltages applied are, the problem arises that the input originating from the filter attenuation becomes larger.

A generic double conversion television receiver is disclosed in US-PS 4,402,089 discloses. This comprises a first mixer stage, where filtered and amplified mixed input signals with the output of a first local oscillator be, and a second mixer which its input the output signal a second local Osziallators overlaid to a second intermediate frequency signal to generate for the TV signal processor. An intermediate frequency amplifier and a plurality of Filter circuits are arranged between two mixing stages. The input circle has two signal paths, one for the VHF and the other for the UHF Tape. In each path tunable filters are arranged as well as an amplifier and a "Trap circuit", which is a fixed tuned filters for damping the second Zwischenfre frequency is.

Tunable circuits in the HF band filters are influenced so that predetermined, fre -selective characteristics are obtained. This is done by means of an electronic Adjusting device which and a programmable ROM, digital / analog converter having analog buffer amplifier.

The control is effected by means of a decoding and control logic that their Eingangsi signals received from a control keypad. In the operation of the electronic adjustment device decodes said logic the channel selected by the keyboard Input information and addresses a corresponding storage location in the Peek term ROM. The value is input to a digital / analog converter, the analog one Tuning signal generated that amplifies and the tuning means of the respective Buffer amplifier is supplied. This sequence is repeated for all tunable circuits ever membranously performed, when a new channel is selected.

The digital values ​​of the respective tuning voltages are a non-volatile all- Random access memory entered by means of a separate tuner adjusting unit with is receiver connected only for the purpose of making adjustments.

In the known arrangement, the optimal tuning voltages are characterized determined that the contents of the memory locations are varied until the desired loading operating conditions that at appropriate points in the tuning system with appropriate Test signals are detected, are achieved. Such, static tuner Tuning is not just capable of changing reception conditions to be as the place and time of the fluctuating operating conditions Receiver result.

On the other hand, DE-PS 33 47 132, a circuit arrangement and a method disclosed for dynamically tuning a tuner oscillator. Here is an opti male vote be found that the frequency of the resonant circuit of a PLL-controlled oscillator, a frequency generated by a local oscillator by a so-called Kennfreugenz is generated which arithmetic in which Mean value between the frequency of the picture carrier and the sound carrier lies, and when crashing mixing always a slightly reduced intermediate circuit frequency is transformed, must be matched to the then the intermediate frequency circuit. This method requires a number of additional elements (local oscillator, mixer, Switching stages and capacitors), without which the previously known arrangement not funk is capable tion.

Furthermore, the leaves 33 47 132 previously known tuning method from DE-PS not transposed to a double conversion television receiver, where the Conditions are much more difficult. Because with Doppelüberlagerungs- Fersehempfängern, due to the numerous influences names on the Emp fang signal also "inclined" settings result in which, for example. A filter and / or a local oscillator is set disadvantageous, but what optimal by a Adjustment of the remaining elements is compensated. In such a case it can pas Sieren that one of the amplifier signal as a result of an unfavorable input signal level is in a sort of limitation state, so that a change before switched tuning elements no change of the tapped and Vote using AGC voltage causes. In the absence of recognizable Feedback can in such a case be found not optimal setting.

It is therefore an object of the present invention, the various, above be signed to solve commonly occurring problems, especially a dynamic cal method for automatic tuning and circuitry ei to provide nes double conversion television receiver available. This should a tuning voltage to be applied to the RF tuning circuit, which under differently to tuning voltage for the VCO of Doppelüberlagerungs- Television receiver and the image / sound carrier wave of the input of the double conversion uses storage receiver input to the channel.

To solve this problem, the invention provides the next level in the claims chen measures contained before. This includes the tuning circuit of the Receiving part a number of bandpass filters for processing of the formants nena mergers applied RF signal and an RF amplifier and an on passungsschaltkreis, a number of internal oscillators for producing Wave signals with adaptation to the applied RF signal, and furthermore a number of mixers for mixing the output of the matching circuit and the internal oscillator. The receiving part further contains an After running synchronization circuitry (PLL) for controlling the output of the in internal oscillator of the tuning, a circuit for generating a Video intermediate frequency, which from the output signal of the Abstimmschaltkrei ses a signal for automatic RF gain control (AGC) as well as a signal for automatic RF gain control (AGC) as well as a Signal for automatic IF gain control (ZFAGC) produced, also an automatic tuning, which using the two output signals of the video intermediate frequency generating circuit, the band-pass filter signal of the tuning controls. This automatic shut voting element comprising a number of A / D converters for implemen tion of the two analog signals of the Videozwi rule frequency generating circuit in digital Signa le, a ROM-memory element with the control program, which the procedure for automatic tuning of the front invention corresponds to a microprocessor for Processing of the two converted to digital values Signals using the data stored in the ROM memory element Control program, a number of D / A converters to implement two by the microprocessor generated, digital signals in analog signals, as well as an operational amplifier, the Outputs of the D / A converter compares and voting circuitry controls. According to the described scarf processing arrangement, the method consists of a first Pro process, wherein the VCO circuit using a PLL circuit circuit and tunes the RF signal with the aid of a by the control program from a memory element of the Mi continuously supervises read tuning value tunes, wherein the AGC voltage of the picture carrier wave with a maximum AGC voltage is compared. A second process uses ZFAGC voltage when the first process the maximum AGC is reached or exceeded voltage; if the maxi male AGC voltage is greater, this step is skipped. Then, the tuning voltage is controlled so that the AGC voltage maximum gain he extends, said AGC value ge in a memory element is stores. In addition to +4.5 MHz Oszillati onsfrequenz of the input signal are added, whereby the VCO is controlled. In a third process is the Tonträ gerwelle determined and their tuning voltage controlled that the AGC voltage of the sound carrier wave has a maximum reached amplification factor. This value is in a stored memory element and finally the VCO means the oscillation frequency controlled. A fourth process controls the RF signal with a tuning voltage, which by subtracting a value obtained by subtracting the picture carrier wave voltage from the Tonträ gerwellenspannung corresponds, from the picture carrier wave clamping tion results. This tuning is in a Memory element stored. In a fifth process a value of the AGC voltage of the image carrier is subtracted which results from the difference between the AGC voltage the picture carrier wave and the AGC voltage of the sound carrier wave results. According to the resulting value is the new AGC Voltage of the image carrier wave set. Accordingly, the AGC voltage of the new sound carrier wave set. A sixth Process compares the absolute value of the AGC Spannungsdiffe ence of the new image and sound carrier wave of the fifth Prozes ses with fixed numerical values. sets A seventh process Finally, the tuning firmly on the AGC voltage the newly determined sound carrier wave, when the absolute value and the fixed numerical value in the sixth process were the same. If the absolute value and the fixed numerical value among are differently, the AGC voltage of Bildträgerw is elle compared with the AGC voltage of the new sound carrier wave, changed and the tuning voltage in a memory element stored. An eighth process changes the AGC voltage of Picture / sound carrier wave of the seventh process again where amended by tuning the picture carrier wave so is that the sixth process can be performed.

The above what will be presented and the benefits the present invention will in the following description of the invention with reference to the accompanying drawings explained.

to show better understanding of the invention, and to, how it may be carried out, in the following a game embodiment with reference to the accompanying drawings explained. In the figures:

<b>Fig.</b> 1 is a flowchart of a preferred method for automatic tuning of the vorlie lowing invention,

<b>Fig.</b> 2 graphs for explaining the preferred procedural procedure for automatic tuning in accordance <b>Fig.</b> 1 and

<b>Fig.</b> 3 is a block diagram of the used Schaltungsan Regulation, with the process of the invention is applied.

In the following, the a preferred embodiment invention with reference to the accompanying Drawing described in detail.

<b>Fig.</b> 3 shows a block diagram of the system used, with the method for automatically adjusting a Dop pelüberlagerungsempfängers according to the present invention is applied.

In this <b>Fig.</b> 3 passes through the RF input signal at the antenna input <b>11</b> is applied, a first band-pass filter <b>12</b>, In a first RF amplifier <b>13</b> sufficient ver strengthens and after passing through the matching circuit <b>14</b> to the first mixing stage <b>15</b> applied. This first mixed step <b>15</b> mixes the output of the matching circuit circle <b>14</b> with the signal of a first internal oscillator <b>16</b>, The output signal of the mixer stage<b>15</b> is one of second band-pass filter <b>17</b> filtered and a second RF amplifier <b>18</b> supplied. The first internal oscillator<b>16</b> is supplied from the PLL circuit <b>300</b> controlled. This PLL circuit <b>300</b> the control means of the VCO. The most the second RF amplifier <b>18</b> signal present is sufficient strengthened so that the amplifier output signal to the off output signal of a second internal oscillator <b>20</b> in a second mixer <b>19</b> can be mixed. The output signal of the second mixing stage <b>19</b> is the third RF amplifier <b>21</b> again amplified and finally a one Video intermediate frequency (VIF) producing circuit <b>30</b> supplied. This VIF producing circuit<b>30</b> generated a HFAGC signal <b>31</b> and a signal ZFAGC <b>32</b>, These signals<b>31</b>. <b>32</b> be the A / D converters <b>42</b>. <b>43</b> the microprocessor control unit <b>40</b> supplied. These Microprocessor control unit <b>40</b> is so constructed that a ROM <b>44</b> and a microprocessor <b>41</b> with the A / D-wall learning <b>42</b>. <b>43</b> are connected. From the A / D converters<b>42</b>. <b>43</b> into digital values ​​converted HFAGC- (<b>31</b>) And ZFAGC signals (<b>32</b>) Are of the microprocessor <b>41</b> processed. While this processing occurring results are the Digi / analog converters <b>51</b>. <b>52</b> supplied. This D / A converter<b>51</b>. <b>52</b> set the digital output signals of the microprocessor <b>41</b> in analog values ​​to which the comparator <b>50</b> created are to the RF tuning of the first Bandpassfil ters <b>12</b> to create.

<b>Fig.</b> 1 shows a flow diagram of a preferred Substituted Structuring the inventive method for automatic Poll. According to<b>Fig.</b> 1, the output frequency of the VCO accurately adjust the VCO tuning step <b>101</b> pres fen in which the VCO by using the PLL Schaltkrei ses <b>300</b> is tuned. After this VCO votes step <b>101</b> has undergone, is to maximum ampli obtain kung, an RF Spannungsabstimmschritt <b>102</b> by run, in which the RF voltage by means of a from the ROM <b>44</b> Control program contained read Tuning voltage VT is adjusted. The he RF Vote follows into three bands, and is between these bands ge according to the selected channel switched. Here is the RF Tuning voltage in response to the change of the AGC clamping tion of the tuner and the IF amplifier set. she will means traversal (sweeping) the tuning so determined that a maximum gain within the RF Abstimmspannungsbereichs the desired channel he enough is. The process of going through, a kind of scanning (scanning) represents, is below it purifies. After processing of the RF tuning step<b>102</b> be the AGC voltage of the picture carrier wave VP and a ma ximaler AGC voltage value obtained from the ROM <b>44</b> out was read, in step <b>103</b> compared with each other. Since the RF voltage tuning step <b>102</b> is the System in which the field of A <b>Fig.</b> 2 shown to was standing. This PC is the picture carrier wave and SC the tone carrier wave. If the read maximum value of the AGC Voltage is equal to or smaller than the actual value the AGC voltage of the picture carrier wave of the input signal during this comparing step <b>103</b>Which is ZFAGC- Voltage in step <b>104</b> used. Otherwise, if the Ma mum value of the AGC voltage is greater than the actual Value of the AGC voltage of the picture carrier wave, is immediately to step <b>105</b> passed. In this step,<b>105</b> will the set tuning voltage VT so that the Bildträ gerwelle VP related AGC voltage maximum ampli kung factor results. The value of the AGC voltage V_AGC (VP) relative to the picture carrier wave, in step <b>106</b> in egg NEM memory element stored. From the setting in step <b>105</b> results in a system state, as in the part picture of B <b>Fig.</b> is seen. 2 Im in the field B Darge presented graph moves the tuning voltage VT to egg ner position which is identical to the voltage Vp of the Picture carrier wave. On the other hand, after the step<b>107</b> the VCO by adding +4.5 MHz to Os is tuned zillationsfrequenz FO according to the RF signal, the tuning voltage VT is controlled so that the sound on the carrier wave-based AGC voltage maximum ampli achieved kung factor. This occurs in step<b>108</b>, currency rend of step <b>107</b> If the oscillation frequency of the raised half to +4.5 MHz to on the sound carrier wave related AGC voltage VS to be determined. This 4.5 MHz ent speak to the difference value SC-PC. Therefore, after the VCO so has been tuned to the oscillation frequency by 4.5 MHz was raised, the desired value is determined by the vote will go through so that this value to ma imum gain is. During step<b>108</b> results of the partial image of C <b>Fig.</b> 2 represented Sy stemzustand. According to this frame C corresponds to the Ab tuning voltage VT of the voltage VS of the sound carrier wave.

The AGC voltage VS, V_AGC (VS), which by itself SETTING ment of the tuning voltage VT in step <b>108</b> results, is in step <b>109</b> stored in a memory element. in the step <b>110</b> is the VCO on the oscillation frequency FO adjusted in accordance with the RF signal. To compare value to obtain the difference between the voltage ΔVSP VS the sound carrier wave SC and the voltage VP of Bildträ gerwelle PC (ΔVSP = VS - VP) again to form a further tuning voltage VT of the voltage VP of the image carrier wave PC subtracted (VT = VP - ΔVSP). On this Value is the tuning voltage VT in step <b>111</b> turned represents, at the same time an adjustment of the RF signal takes place. Then, the corresponding AGC voltage V_AGC (-ΔVSP), Engaged in the tuning voltage VT = VP - ΔVSP yields, in step <b>112</b> Stored in a memory element chert. During step<b>111</b> the system is in a D field of <b>Fig.</b> 2 state shown. In step<b>113</b> is the AGC voltage of the step <b>112</b> set for the AGC voltage (VP = VP - ΔVSP) the new picture carrier wave PC and the AGC voltage of the picture carrier wave PC for the AGC Value (VS '= VP) of the new sound carrier wave SC. At the time of step <b>113</b> lies in the field of E <b>Fig.</b> 2 Darge introduced system state. The AGC voltages of new Pictorial and sound waves of step <b>113</b> be in step <b>114</b> compared with each other. In this comparison, is the size of the absolute value of the difference between the AGC voltage VS 'of the sound carrier wave SC and the AGC voltage VP 'of the picture carrier wave PC (| V_AGC (VS ') - V_AGC (VP ') |) he averages. That is, it is determined whether the gain factor (V_AGC (- ΔVSP) is identical with the gain factor (V_AGC (P)) is. If in step<b>114</b> the Verstärkungsfakto ren the sound carrier wave and the picture carrier wave identical are, the voltage value VS 'of the sound carrier wave of Ab tuning voltage VT in step <b>123</b> assigned and finally stopped. If as a result of the comparison in step<b>114</b> the absolute value is not equal to the fixed value 0, the AGC voltage VS 'new sound carrier wave SC with the AGC Voltage VP 'of the new picture carrier wave PC at step <b>115</b> compared. If during this comparison of the AGC voltage value VS 'of the sound carrier wave SC is larger, the ver independent amplification factor number N amending voting voltage VT subtracted (N = - (N + 1)), which in step <b>116</b> happens. However, if the AGC voltage Vp 'of the Bildträ gerwelle PC is greater than the AGC voltage VS 'of Tonträ gerwelle SC, is the amplification factor independent number N amending tuning voltage VT in step <b>117</b> added (N = N + 1). A second tuning voltage (VT2 = VS '+ NΔV) in step <b>118</b> educated. A differential voltage .DELTA.V is with the gain value independent of N, which at steps <b>116</b> respectively <b>117</b> been determined is multiplied and finally to the AGC voltage value VS 'of the sound carrier wave SC added. The AGC voltage V_AGC (VS '+ NΔV) based on the tuning voltage VT2, is in the step <b>119</b> stored in a memory element. The AGC Value (VP '+ NΔV) obtained in step <b>119</b> been saved is, corresponds to a voltage gain at a Shift the tuning of the sound carrier wave SC Graph to the left by about 1 MHz. A third tuning (VT3 = VP '+ NΔV) in step <b>120</b> set. in this connection is the amplification factor independent number N with the Differential voltage .DELTA.V multiplied and this value for AGC Voltage VP 'of the picture carrier wave PC added. The AGC clamping voltage V_AGC (VP '+ NΔV) the third tuning voltage VT3, wel che in step <b>120</b> has been set, in step <b>121</b> stored. Subsequently, the image will be / Media wave tuning voltages VT2, VT3 steps <b>118</b> and <b>120</b> set (replaced) by the AGC voltage value (VS '= VS' + NΔV) another sound carrier wave VS ', SC and by the AGC voltage value (VP '= VP' + NΔV) of the image carrier wave PC, which in step <b>122</b> happens. thereupon the program returns to step <b>114</b> back. In this Loop the system remains until the Absolutbe contract (| V_AGC (VS ') - V_AGC (VP ') |) identical to the solid Value is 0. Once this is the case, through the clamping voltage value VS 'of the sound carrier wave SC in step <b>123</b> a final tuning voltage VT set. In step<b>123</b> lies in the field of F <b>Fig.</b> 2 shown before graph. Here, the voltage is a NΔV at each pass by 1 MHz increasing tension. The value of the differential voltage .DELTA.V = ΔVSP / 4; 5.

As set forth above, the present invention has the Prior in part, that the originating from the input filter losses, be subjected to the image / sound carrier wave, are minimal. This is determined by the choice of the capacitance diode of the A achieved gangs RF circuit scale tuning.