DE4126774A1 - Converter for Astra satellite signal reception - selects two local oscillator frequencies so that second or third order mixing products fall between channels - Google Patents

Abstract

The converter has a polarisation filter (11) for separating horizontal and vertical polarised signals. After the filter is a mixing stage (15',15") in each following reception branch (13',13") with local oscillators (17',17") for each mixing stage for converting the reception signals into IF, pref. with a combination diplexer (21) for feeding a common output line (5). The frequencies of the two local oscillates are chosen so that second or third order mixing products of the local oscillation frequencies in the IF plane lie frequency-gap increased w.r.t. the other channel frequency intervals. The products have a min. spacing of 14.75 MHz to the adjacent channels between the 15th and 17th, or 16th and 18th channel. USE/ADVANTAGE - For reception of Astra 1C satellite, with reduced channel interference.

Description

The invention relates to a converter arrangement for receiving Satellite reception signals according to the preamble of the claim 1.

A large number of satellites are now geostationary in space stationed through which the most varied of programs and Program packages can be received.

To the satellites that have become more important lately have heard of the Astra 1A, for example in a frequency range from 11.2 to 11.45 GHz.

The other satellite was also a short distance away Astra 1B positioned geostationarily.

The two signals become linearly orthogonal to one another polarized waves for the reception of different television programs  broadcast on the Astra 1A satellite channels 1 to 16 and channels via satellite Astra 1B 17 to 32 with the frequency ranges enclosed in the system according to the table, with the emitted signals in each channel alternately linearly polarized once horizontally and once vertically and are therefore perpendicular to each other.

Because the two Astra satellites are immediately adjacent to each other are positioned geostationarily, each of the two Satellite broadcast programs via only one satellite Receiving system can be received.

The horizontally polarized waves of the Astra 1A satellites and Astra 1B can be in the one of a polarization switch downstream reception branch by means of a local oscillator, for. B. with a local oscillator frequency of 9.7 GHz in an intermediate frequency IF range can be implemented. The through channels 2 to 32 radiated vertically polarized waves are emitted in the second receiving branch by means of a local oscillator frequency of e.g. B. 10.25 GHz implemented in the corresponding IF frequency range. This results in two staggered Frequency ranges that are applied to a single output line with a diplexer, d. H. be fed into a single-cable lead can. By a sufficiently large frequency spacing between the horizontally and vertically polarized transmission ranges of the two satellites can therefore use a combination diplexer be used, whose characteristic is only a little steep, whereby the construction effort can be limited.

However, a third Astra satellite Astra 1C is now said to be in the immediate vicinity Proximity to the other two geostationary, that on channels 33 to 48 with the frequencies 10.964 emits up to 11.185.5 GHz. This has the consequence that in the second reception branch by the local oscillator there channels 33 to 48 of the satellite Astra 1C into an IF frequency be implemented, which z. B. partially with the IF frequency  of channels 21 to 31 overlaps. Another disadvantage is that the Frequency offset between the Astra-1C channels to the Astra-1B- Channels is too small or is practically non-existent, so that a combination diplexer particularly high demands in terms of should meet a steepness to be demanded.

But above all, between the two local oscillator Frequencies mixed products that the simple or integers Multiples the difference of the local oscillator frequencies. Although the first mixed product is outside of the one received Frequency range lies, the disadvantage of the second weighs Mixed product, d. H. the double frequency difference between the two local oscillators the heavier because this mixed product falls directly into a specific reception channel and thus interference with the programs broadcast via this channel leads. The same applies to the higher mixed products.

The object of the present invention is therefore that To overcome disadvantages according to the prior art and one To create converter arrangement in which the on different Frequently broadcast programs with high quality and with few or only minor interference effects with comparatively little technical effort can be received, in particular even when the third Astra satellite is stationed.

The task is according to the invention in accordance with the claim 1 specified features solved. Advantageous embodiments of the Invention are specified in the subclaims.

The present invention is particularly surprising and cleverly ensures that the to a Interference leading mixed products practically without additional technical Measures are "suppressed" in their disruptive influence. the local oscillator frequencies for implementation in the Zwi frequency level are selected so that at least the  double or triple the local oscillator frequency difference, the interference product of the second or third order exactly in that Channel frequency spacing range between the 15th and 17th or 16th and 18th channel falls, which in contrast to the other channel Frequency intervals are larger. Because this "bigger frequency jump" results from the distance from the satellite Astra 1A to channel frequencies broadcast to satellite Astra 1B.

The selection is always made so that the larger Interfering mixed product with the best possible and large distance between the two mixing frequencies of the neighboring Channels come to rest.

The concept of solution explained above applies in principle independently whether, for example, channels 1 to 31 are opposite channels 2 to 32 in the IF frequency level higher or lower lie.

In a further embodiment of the invention, the total permissible IF bandwidth from 950 to 2050 MHz the V channel range and the H channel area for receiving the vertical or horizontally polarized signals so that the bandwidth of the Channel gap between the two IF channel areas becomes maximum.

Finally, in a preferred embodiment of the invention also the frequency offset of the channel center frequencies of the V or H signals broadcast via the third satellite Astra 1C to the H- received in the same frequency range or V signals at least in the sense of a compromise solution at least be chosen so large that also with a diplexer low slope, the least possible disturbance in the transition area of the signals received by the third Astra satellite 1C polarity to that received by the two Astra satellites Signals of different polarity is caused. A diplexer with low steepness has significant cost advantages and leaves technically easier to realize.

The invention is described below using an exemplary embodiment explained. It shows in detail

Fig. 1 shows a schematic view of a basic structure of the converter arrangement according to the invention,

Fig. 2 shows an overview of the received channel frequencies as well as the location of the disturbing mixing products,

FIGS. 3a to 3c extracts enlarged views of Fig. 2,

Fig. 4 graphical representations of an optimally selected mixed product.

In Fig. 1 a schematic illustration of a satellite antenna 1 followed by a converter arrangement 3 and a single dissipation 5 is shown the manner of a "Einkabellösung", wherein possibly provided polarization rotator or - for receiving circularly polarized waves - optionally upstream polarization converter omitted etc. are. Such measures can also be provided as required.

The converter 3 shown only in principle comprises, for example, an upstream part of the converter arrangement forming filter 7 , a preamplifier 9 , a polarizing filter 11 and in each subsequent receiving branch 13 ' and 13'' a mixer 15' and 15 '' , each a local oscillator 17 ' or 17''is assigned.

A mixer 19 ' or 19'' and a combination diplexer 21 can be arranged downstream, for example. The signals received via the two receiving branches 13 ' and 13'' and converted into a respective IF frequency are then amplified, for example, via a further amplifier stage 23 , which may be provided, and fed to the connected consumers via the single derivative 5 .

The individual amplifiers, filters etc. can also if necessary be connected externally to the converter arrangement.

In a preferred embodiment, the first local oscillator in the first branch 15 ' for receiving the horizontally polarized waves according to the table attached in the system for receiving channels 1, 3, 5,. . ., 31 with a frequency of 10.259 GHz and the local oscillator for receiving the vertically polarized waves in the second receiving branch 15 '' , ie for receiving the channels 2, 4, 6,. . ., 32 operated at a frequency of 9.665 GHz.

With the selected local oscillator frequencies mentioned above, this means that, according to FIG. 2, channels 1 to 31 are converted into a lower IF frequency and channels 2 to 32 into a higher IF intermediate frequency. The table shown in the system shows the frequencies emitted by the three Astra satellites in relation to their channels 1 to 48 as well as the polarization. Then, for example, the 31st channel is broadcast at a frequency of 11,670.75 MHz. With a local oscillator frequency LO1 of 10.259 GHz, this results in an intermediate frequency (IF frequency) of 1411.75 MHz, as shown for channel 31 in FIG. 1. Accordingly, the IF frequencies can also be calculated for the other channels.

The channels 1 to 31 are used in the exemplary embodiment shown Reception of the horizontally H-polarized and channels 2 to 32 to receive the V-polarized vertical signals.

From Fig. 2 it can also be seen that between the 31st and the 2nd channel there is a channel gap with the bandwidth B, which - which will be discussed - should be as large as possible. The extent of this distance is limited, however, since the permissible IF frequency range is generally limited to a frequency spectrum from 950 to 2050 MHz. In the selected exemplary embodiment, this is fulfilled because the first channel has an IF frequency of 955.25 MHz and the 32nd channel has an IF frequency of 2020.50 MHz.

A purely mathematical check shows that the frequency spacing of the center frequency of the individual channels is 29.5 MHz in each case. Only between the 15th and 17th or the 16th and 18th channels is there a larger frequency gap of 43.5 MHz. It is precisely in this gap that the mixed product of the second or third order can be placed, as a rule the mixed product of the second or third order, which, depending on the technique chosen, has a greater disturbing influence, also in quantitative terms. In the _exemplary embodiment shown, the frequencies F _LO1 and F _{LO2 were selected} for the frequency of the first and second local oscillators so that the following mixed products result:

_Mixed product of the 1st order: 1 × (F _LO1 -F _LO2 ) = 594
2nd order mixed product: 2 × (F _LO1 -F _LO2 ) = 1188
3rd order mixed product: 3 × (F _LO1 -F _LO2 ) = 1782

From this it can be seen that the first mixed product with a frequency of 594 MHz is outside the reception range.

The second mixed product at 1188 MHz lies between the center frequencies for the 15th and 17th channels, which is converted to the IF frequency of 1161.75 and 1205.25 MHz, as is shown in principle in FIG. 2 and in an enlarged view is shown in Fig. 2a. This results in a minimum frequency offset d₁₇ of 17.25 MHz, which means a significant improvement over the prior art.

The third mixed product falls in the IF range, in which the vertical Channels implemented with the local oscillator frequency 9665 GHz will. The third mixed product with 1782 MHz is between the 16th channel at 1770.50 MHz and the 18th channel with 1814 MHz. The minimum frequency offset to the center frequency is thereafter d₁₆ = 11.50 MHz.  

This distance from the center frequency of the closest neighbor Transmission channel is lower than in the case of the second Mixed product. In the drawing is also quantitative Regarding the influence of the disturbance variable, which is evident is that the third mixed product is also quantitative only leads to a much smaller disturbance. Furthermore is the frequency offset determined above for this in quantitative With regard to low interference, fully sufficient.

With the selected local oscillators, the channels 34 to 48 of the third Astra satellite 1C converted into a frequency range, which partially overlaps with channels 23 to 31 and partly in the bandwidth B of the channel gap between the V- or H-polarized waves.

Appropriate filter measures can then be used to suppress and hide the channels 34 to 40 shown in FIG. 2, so that, depending on the consumer, the desired programs transmitted on the specific channels can be fed into the single derivative.

From Fig. 3c and from the following illustration it can be seen that there is an optimal and favorable frequency offset of the Astra-1C channels to the Astra-1B channels at the selected local oscillator frequencies.

For example, the 31st channel of the Astra 1B is converted into a ZF Frequency of 1411.75 MHz implemented. Channel 40 of the satellite Astra 1C is converted into an IF frequency of 1402.5 MHz. The frequency offset is therefore 9.25 MHz, so that the locos zillator combination of 10.259 and 9.665 GHz clear Has advantages.

Through certain technical measures, such as filter assemblies it is also possible to ensure that, for example the interference of the second mixed product is less is as the interference of the third mixed product. Then would  the corresponding local oscillator frequencies are selected so that the corresponding third order mixed product if possible middle z. B. between the frequencies of the 16th and 18th channels comes to lie. Preferred is here, as in the above Embodiment, always an area where the Mixed product of second or third order in a distance range from

lies. This means that the two or three times the mixed product of the lo cal oscillator frequency difference in an area formed around the middle of half the frequency spacing between the channels 15 and 17 or 16 and 18 with a range of z. B. should be ± 7 MHz, preferably at least with a range of ± 6 MHz, ± 5 MHz, ± 4 MHz, ± 2 MHz or ± 1 MHz. The corresponding relationships are shown in FIG. 3.

Finally, it is also pointed out that the local oscillators can be selected so that, in contrast to the exemplary embodiment according to FIGS. 2 to 3c, channels 2 to 30 in a lower IF frequency and channels 1 to 31 in a higher IF frequency Frequency are implemented so that the channel sequence to the embodiment of FIG. 1 is exactly the opposite. In this case, the channels 33 to 47 of the third Astra satellite 1C (which are used to receive the H-polarized signals) would at least partially match the frequency range of the channels 26 to 32 of the second Astra satellite 1B to receive the V-polarized signals overlap so that the appropriate masking measures and a corresponding frequency offset should be achieved here.

The above based on a preferred embodiment resulting values are subsequently shown using a simple Played over, based on which different optimal Local oscillator frequencies can be selected.  

After that there are (without a corresponding derivation enter into the following relationships:

F _LO1 = F ₁₇ -2F ₃₁ + 2F ₄₀ -d ₁₇ + 2K (1)

F _LO2 = F ₁₇ -3F ₃₁ + 3F ₄₀ -d ₁₇ + 3K (2)

Mean
F _i = the respective frequency of channel i of the Astra satellites,
d₁₇ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 17th channel,
K = the center frequency offset between the H-polarized signals transmitted on channels 17 to 31 to the closest V-polarized signals of the third Astra satellite with channels 34 to 48.

By a suitably clever choice for d₁₇ and K, the local oscillator frequencies F _LO1 and F _LO2 can now be determined, the value for d₁₇ to the frequency of the adjacent channel 17 the condition

should meet. Then there would be the cheapest value for d₁₇ = 21.75 MHz and for K = 14.75 MHz, namely half the value of 29.5 MHz, i.e. H. the frequency center distance between the frequency of the 31st and for example the 40th channel. As a result you got then for the local oscillator frequency:

F _LO1 = 10 265.5
F _LO2 = 9,677.0

This is the only optimal solution in general do not come into play because at these local oscillator frequencies the first channel of the IF level has an intermediate frequency of 948.75 MHz would result, which is slightly below the fixed per se lowest allowed intermediate frequency of 950 MHz would. Due to a slight deviation, the In the sense of a compromise, the optimal value can be determined.

The optimal values given above can vary in larger band ranges. Values are still favorable in which the difference from F _LO1 -F _LO2 , as results from the most optimal values mentioned above, by no more than ± 10 MHz, in particular no more than ± 9 MHz, ± 8 MHz, ± 7 MHz, ± 6 MHz, in particular ± 5 MHz, ± 4 MHz, ± 3 MHz or only ± 1 MHz deviates and varies.

For the sake of completeness, it is mentioned that instead of Formulas (1) and (2) above also include those mentioned below Formulas can be chosen:

F _LO1 = F ₁₇ + 2F ₂ -2F ₃₁ -d ₁₇ + 2B (4)

F _LO2 = F ₁₇ + 3F ₂ -3F ₃₁ -d ₁₇ + 3B (5)

being the size
B = the bandwidth of the channel gap between the 31st and 2nd channel

is.

The above formulas (1), (2) and (4) and (5) apply in the event that the double local oscillator difference as a second order mixed product between the 15th and 17th Channel is laid. In certain applications, however, it can may well be that the mixed product of third order also in quantitatively a greater disturbance than the mixed product  second order, so that you then the mixed product third order so between the 16th and 18th channels, so that the frequency spacing d₁₆ to the neighboring (usually channel 16 closer to that shown in equation (3) Conditions met.

In this case, equations (1), (2) and (4), (5) only change to the extent that there instead of the reproduced Sizes

-d₁₇ and F₁₇

the sizes

+ d₁₆ and F₁₆

should be used. d₁₆ would then be the frequency differences represent the limit amount between one of the neighboring channels should definitely be adhered to.

In the following, a further modification of only the completeness is intended be explained for the sake of it.

In contrast to the embodiment according to Fig. 1, it is also possible that the local oscillator frequencies are selected for the intended in the first as the second receive branch mixer so that the IF frequencies of the channels lie 2 deeper to 32, and in contrast, the channel frequencies 1 to 31 in the IF frequency range are higher, that is, they are reversed to the representation according to FIG. 1. Then the channels 33 to 47 (for receiving the H-polarized signals) received by the third Astra satellite 1C by means of the second local oscillator would be partly with some channels, usually in channels 26 to 32 for receiving the corresponding V-polarized ones Signals overlap.

This arrangement could also, depending on which Mixed product of the local oscillator frequency the greater interference  also in quantitative terms, the corresponding Lo calos oscillator frequencies are chosen so that either Second order mixed product between the 16th and 18th channels or the third order mixed product between the 15th and 17th Channel as centrally as possible according to the formulas given above for the 17 or the 16 comes to rest. These formulas would then read:

F _LO1 = F ₁₈ -F ₃₂ + 2F ₃₉ -d ₁₈ + 2K (6)

F _LO1 = F ₁₈ -3F ₃₂ + 3F ₃₉ -d ₁₈ + 3K (7)

Instead of the size K for the frequency center offset can also again the size "B" selected for the bandwidth in the channel gap are, so that alternatively the formulas can be summarized as:

F _LO1 = F ₁₈ + 2F ₁ -2F ₃₂ -d ₁₈ + 2B (8)

F _LO2 = F ₁₈ + 3F ₁ -3F ₃₂ -d ₁₈ + 3B (9)

Deviating from the formulas (6) to (9) should apply again that the second mixed product has less interference than that Third order mixed product, i.e. H. that the triple local oszil frequency difference between the 15th and 17th channels (which have a higher frequency than the frequencies of the channels 16 and 18) must be placed, so again instead of Sizes

-d₁₈ and F₁₈

the sizes

+ d₁₅ and F₁₅

in formulas (6) and (9), where the size

d _i

the corresponding formula (3) for the frequency distance to the neighboring Channel i should meet.  

Table with regard to the channels broadcast by the Astra satellites, the associated channel frequencies and polarities

Claims (14)

1.Converter arrangement for receiving satellite reception signals, in particular for receiving the signals emitted via the satellites Astra 1A to 1C, with a polarization switch ( 11 ) for separating the horizontally and vertically polarized H and V signals, each with a mixing stage ( 15 ′ , 15 ′ ′ ) in each of the two reception branches ( 13 ′ , 13 ′ ′ ) arranged downstream of the polarization switch ( 11 ), each with a local oscillator ( 17 ′ , 17 ′ ′ ) assigned to each mixing stage ( 15 ′ , 15 ′ ′ ) for converting the received signals into intermediate frequencies (IF), preferably with a combination diplexer ( 21 ) for feeding the frequencies converted into the respective IF frequency into the two IF branches ( 15 ' , 15'' ) into a common derivative ( 5 ), characterized in that the local oscillator frequency F _LO1 and F _{LO2 of} the two local oscillators are selected so that the two or three times the mixed product of the local oscillator frequencies (Mischpr second or third order product) on the IF frequency level in which the frequency gap between the 15th and 17th or the 16th and 18th channels, which is larger than the other channel frequency spacings, is at a minimum distance of 14.75 MHz from the adjacent channels . 2. Converter arrangement according to claim 1, characterized in that each of the mixed product from two or three times Lo frequency difference in the enlarged frequency gap  between the 15th and 17th or the 16th and 18th channels, which also has the greater interference in quantitative terms exercises. 3. Converter arrangement according to claim 1 or 2, characterized in that in the generally permissible IF frequency range from 950 to 2050 MHz the bandwidth (B) of the channel gap between the channels for receiving the V-polarized or the H-polarized Signals in the IF frequency level maximum or at least is approximately maximum. 4. Converter arrangement according to one of claims 1 to 3, characterized characterized in that the frequency offset (K) in the IF Level between the channels for receiving the V-polarized Waves of the third Astra satellite (1C) and the neighboring ones H-polarized signals of the first and second astra Satellite (1A, 1B) or for receiving the H-polarized signals of the third Astra satellite (1C) and the neighboring ones V signals from the first and second Astra satellites (1A, 1B) above of a lower minimum limit. 5. Converter arrangement according to claim 4, characterized in that that the frequency offset (K) is more than 5 MHz, preferably more than 6, 7, 8, 9, 10, 11, 12, 13, 14 or 14.75 MHz. 6. Converter arrangement according to one of claims 1 to 5, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₇ -2F ₃₁ + 2F ₄₀ -d ₁₇ + 2K (1) F _LO2 = F ₁₇ -3F ₃₁ + 3F ₄₀ -d ₁₇ + 3K (2) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₇ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 17th channel,
K = the center frequency offset between the H-polarized signals transmitted on channels 17 to 31 to the closest V-polarized signals of the third Astra satellite with channels 34 to 48
is. 7. Converter arrangement according to one of claims 1 to 6, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₇ + 2F ₂ -2F ₃₁ -d ₁₇ + 2B (4) F _LO2 = F ₁₇ + 3F ₂ -3F ₃₁ -d ₁₇ + 3B (5) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₇ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 17th channel,
B = the bandwidth of the channel gap between the 31st and 2nd channel
is. 8. Converter arrangement according to one of claims 1 to 5, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₆ -2F ₃₁ + 2F ₄₀ -d ₁₆ + 2K (1) F _LO2 = F ₁₆ -3F ₃₁ + 3F ₄₀ -d ₁₆ + 3K (2) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₆ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 16th channel,
K = the center frequency offset between the signals of the third Astra satellite and the adjacent signals of the first and second Astra satellites
is. 9. Converter arrangement according to one of claims 1 to 5 or 8, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₆ + 2F ₂ -2F ₃₁ -d ₁₆ + 2B ( 4) F _LO2 = F ₁₆ + 3F ₂ -3F ₃₁ -d ₁₆ + 3B (5) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₆ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 16th channel,
B = the bandwidth of the channel gap between the 31st and 2nd channel
is. 10. Converter arrangement according to one of claims 1 to 5, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₈ -F ₃₂ + 2F ₃₉ -d ₁₈ + 2K (6) F _LO1 = F ₁₈ -3F ₃₂ + 3F ₃₉ -d ₁₈ + 3K (7) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₈ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 18th channel,
K = the center frequency offset between the signals of the third Astra satellite and the adjacent signals of the first and second Astra satellites
is. 11. Converter arrangement according to one of claims 1 to 5 or 10, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₈ + 2F ₁ -2F ₃₂ -d ₁₈ + 2B ( 8) F _LO2 = F ₁₈ + 3F ₁ -3F ₃₂ -d ₁₈ + 3B (9) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₈ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 18th channel,
B = the bandwidth of the channel gap between the 31st and 2nd channel
is. 12. Converter arrangement according to one of claims 1 to 5, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₅ -F ₃₂ + 2F ₃₉ -d ₁₅ + 2K (6) F _LO1 = F ₁₅ -3F ₃₂ + 3F ₃₉ -d ₁₅ + 3K (7) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₅ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 15th channel,
K = the center frequency offset between the signals of the third Astra satellite and the adjacent signals of the first and second Astra satellites
is. 13. Converter arrangement according to one of claims 1 to 5 or 12, characterized in that the local oscillator frequency F _LO1 and F _LO2 result from the following equations: F _LO1 = F ₁₅ + 2F ₁ -2F ₃₂ -d ₁₅ + 2B ( 8) F _LO2 = F ₁₅ + 3F ₁ -3F ₃₂ -d ₁₅ + 3B (9) where
F _i = the respective frequency of channel i of the Astra satellites,
d₁₅ = the preselectable frequency distance of the interfering mixed product from the transmission frequency of the 15th channel,
B = the bandwidth of the channel gap between the 31st and 2nd channel
is. 14. Converter arrangement according to one of claims 1 to 13, characterized in that the double or triple local oscillator difference placed between the channels 15 and 17 or 16 and 18 to the adjacent channel d _{i is} a distance of at least 10 MHz, preferably 12, 14 , 16, 18, 20 or 21.75 MHz.