DE3505183A1 - Frequency converter for community antenna systems and cable distribution networks with an input converter and an output converter - Google Patents

Abstract

In a frequency converter for community systems and cable distribution systems with an input converter with mixing stage, in which the received frequency is mixed with a frequency generated by a voltage-controlled oscillator, a frequency synthesis circuit with programmable divider is provided for the tuning. The output converter similarly exhibits a free programmable frequency or voltage synthesis circuit for tuning and for generating a second oscillator frequency for mixing it with that present from the input converter. To provide for individual tuning of the input and output converter to various frequencies without calibrating the circuits, the adjustment variables significant for the tuning are determined in a tuning process, including all frequency-changing parameters of the circuit, and are stored in a memory. This memory is activated by a microprocessor which optionally switches through the corresponding adjustment values to the adjustment elements of the input and output converter.

Description

Frequency converter for community antenna systems

and cable distribution systems having an input converter and an output converter The invention relates to a frequency converter for community antenna systems and Cable distribution systems with an input converter and an output converter according to the preamble of claim 1.

IF converters are known to be used in receiving stations from medium-sized and large community antenna systems and cable television distribution systems as well as in Re-conversion points used. Implementation in smaller reception facilities is always necessary when the received frequency ranges in the end devices cannot be processed directly or the line losses are so high that the received frequencies have a level that is necessary for a proper frequency selection not enough. This is particularly the case with direct satellite receiving stations. Due to the carrier frequency in the 12 GHz range, it is essential that the receiving station first converts the received frequency into an intermediate frequency that can be further processed (900 to 1,750 MHz).

A well-known system for frequency conversion of the received channels in the terrestrial radio area is e.g. from the company publication "ZGA-Anlage" of the company Bosch known about the standard intermediate frequency (IF) of 38.9 MHz for the TV converter and 10.7 MHz can be used for the VHF converter input and output converter. In the ZF level, the Selectivity through surface wave resp. Ceramic filter reached. The two independent ones required for implementation Mixing frequencies are generated by voltage controlled oscillators (VCO) whose Frequencies are controlled by programmable PLL circuits. For the different Converter uses the oscillator frequencies of a single reference crystal. The PLL circuit used as a frequency synthesis circuit allows the mixing frequencies to be programmed in a certain grid, which makes a frequency set-off easy is realized.

The well-known TV converters consist of an input and an output converter, which is usually provided with a loop-through output. The input converter contains the first mixer and the downstream ZF amplifier. There is a damping actuator in the entrance intended to reduce the input level. In the module output converter are the second Mixer and the output level control housed.

Here, too, a level control is provided to reduce the gain. A switch, with which the regulation can be switched off for the leveling, and on Level controls, with which the working range of the control can be set, are also available included in the known design according to the ZGA system from Bosch. the Intermediate frequency interface allows any interconnection of input and output converter. It is crucial that the PLL circuit that the frequencies of the oscillator is controlled, can only be programmed via firmly soldered bridges. The division ratio of the frequency dividers present in the PLL circuit is hereby fixed. The filter circuits are manual at the set frequency matched.

One tuned to a certain reception frequency in this way Input converter is with each on a certain output frequency of a channel within a frequency band (Volume I, III or IV and V) matched output converter can be connected.

Just like the input converter, the filter circuits of the output converter are also based on a frequency set once by programming. Adhering to the synchronous and parallel running conditions of the filter circuits, these are at adjusted according to the set oscillator frequency.

When interconnecting different input and output converters Care must be taken to ensure that the output converters influence each other when looping through the output signals, an output raster with a minimum distance e.g. from a TV channel in the VHF range or from at least three TV channels in the UHF range is ensured. For the practical use of such a converter, this means that the input and output converters are specifically selected according to the receiving location and must be assigned to each other. It goes without saying that a multitude be kept ready by various coordinated input and output converters must, especially since the channel spacing in the UHF range is at least two channels in the VHF range and should be at least three channels in the UHF range.

In terms of manufacturing technology, this has the effect that mechanically and electrically matched individual components must be manufactured, with the filter circuits for Ensuring the optimal synchronous and parallel running conditions for one Receive or output channel must be adjusted.

The invention is based on the object of the input and output converter to be interpreted in such a way that for the reception of any reception channels in the respective reception area and its implementation in other named transmission channels in the respective frequency range the cable system only requires a single input and output converter unit, these can be individually tuned to certain input channels and output channels should be.

According to the invention, the object is initially for a frequency converter of the type mentioned solved according to the technical teaching reproduced in claim 1.

The essence of the invention is, instead of using PLL loops permanently set and balanced input and output converters design so that they are tunable and thus on everyone at the installation site any receiving channel and any assigned output channel can be tuned are. The advantages given by the invention are both in manufacturing also given during installation. The comparison, i.e. the definition of that information for setting the frequency synthesis and voltage synthesis circuits are in the Fabrication related to any receiving channel and output channel in the synchronization process For all available channels in a certain area, grid dimensions can be automatically recorded and can be written into the readable non-volatile memory. In addition, you can when using selective and tunable filter circuits to achieve synchronous and parallel running properties for the respectively set receiving channel the corresponding Voltage values for controlling the capacitance diodes of these circuits are digitized can also be read out in a memory or stored in analog memory that can be called up will. at Calling a channel is thus used by the microprocessor one the information for setting the frequency synthesis circuit (the frequency divider the PLL circuit) and, on the other hand, at the same time the voltage values at the D / A converter to correct the coordination of the individual pre- and selective circles.

The process of determining the various digitized values for the PLL circuit and the voltage synthesis circuits for the filter circuits can be carried out fully automatically in a production facility, individually for everyone Converter. This also reduces manufacturing and component tolerances, especially the the components that determine the resonance frequency, such as capacitance diodes, from the outset recorded and taken into account.

The microprocessor, which can be accessed by an input keyboard or by a adjustable channel selector can be activated - e.g.

by preselection switch and the values for the PLL circuit and the voltage synthesis circuit or the D / A converter for direct Outputs control of the frequency-determining components is part of the invention and offers besides the economic advantages the possibility of individual Alignment and layout of the input and output converters.

A major advantage is that the installer, the one Receiving system with converter installed, only one converter unit per channel, which includes input and output converters, needs to use, however a distinction must be made as to whether the received channels are in such in should be implemented in the lower or upper VHF range or in the UHF range or in the case of radio frequency converters (VHF converters) in which frequencies. Depending on the design the converter is either via a keyboard or a corresponding setting switch the channel number of the received channel and also the channel number of the Output signal. The microprocessor reads the in readable from EPROM or ROM memories or other non-volatile memories Information for the frequency synthesis circuits and possibly voltage synthesis circuits for the filters and feeds them to the frequency dividers or to the D / A converters. Each channel number are specific storage locations in the memory assigned, which are called by the microprocessor. For permanently installed systems the channels of the communal antenna system are planned in the conventional way, However, it has been found that regroupings are made possible, for example, by means of additional reception options and supplements become necessary in order to avoid undesired cross-modulation products Conventional systems would therefore have to be exchanged and new upstream and downstream converters be grouped. When using a converter according to the invention, however, is it is only necessary to set the input and output channels according to the Changing requirements. This enables individual adaptation.

This has particular advantages in large cable distribution networks 10 and more occupied channels.

Advantageous further developments of the invention are set out in the subclaims described. It has been shown that in particular with an embodiment according to claim 4 a particularly high output power can be achieved.

Basically, it is known from DE-OS 28 14 577 for overlay receivers with an oscillator circuit and at least one pre-circuit, both via electronic Means (capacitance diodes) are matched to the control voltages or control currents for these electronic means, taking into account the synchronism and parallel operation conditions to be generated by a microcomputer. It is not absolutely necessary that when passing through a frequency range of the oscillator circuit, the frequency sub-ranges are constantly adapted to the pre-circles. To optimize the synchronous and parallel running conditions however, this is necessary.

The corresponding digitized values are stored in a memory and can be called out from this controlled by the microprocessor. this happens by entering the selected receiving channel. The entered channel number or the assigned position number on a remote control or a fixed control of an overlay receiver represent the address for the memory that the Reads out information and sent it to them usually as frequency synthesis circuits used PLL circuits (FLL could also be used) outputs. The match = de pre-circle frequency or other selective filter circuits that of the respective Oscillator frequency is assigned, is through microcomputer controlled voltage synthesis also discontinued. Instead of channel numbers, the frequency values can be set using the Microprocessor can also be entered directly, in a writable and readable Memories can be stored (RAM). In all cases it will be via the microprocessor both the frequency synthesis circuit and the pre-circuits to the new reference oscillator frequency set.

An arrangement that works in the same way by means of a PLL circuit tunable receiver circuit is also the subject of DE-OS 32 41 103. An electronic The voting unit is particularly suitable for television receivers with the same properties, where the programmed channels are called up from a ROM memory when the channel is selected Dividers of a frequency synthesis circuit are controlled, from DE-OS 28 54 852 also known.

The invention applies the microprocessor tuning technology known per se from tuner technology on converter, whereby two completely different frequency converters are controlled in parallel which has the advantages described in relation to the subject matter of the patent.

The invention is illustrated below with reference to FIGS. 1, 2 and 3 in In the form of block diagrams, illustrated embodiments are explained in more detail Fig. 1 shows a freely programmable converter e.g. for direct satellite reception, in Fig. 2 the structure of an output converter with an output power amplifier and in Fig. 3 an output converter with an output filter circuit.

In the block diagram in Fig. 1 is a freely programmable converter for converting the received first intermediate frequency of a direct satellite receiver circuit in the YHF or UHF range for feeding into a cable duct system, stating of the most important structural units.

In the assembly 1 are united a satellite tuner that automatically is tunable, D / A converter for voltage control of the voltage-dependent components the filter circuits as well as capacitance diodes and a PLL circuit of known design arranged to stabilize the frequency of the oscillator. At the entrance of the satellite tuner the first IF from the satellite reception station is available. The block 2 has a FM demodulator and signal processing circuits e.g. for decoding a signal transmitted according to the D2-MAC method. The module 3 has a picture IF demodulator and a residual sideband filter, on him is that of the IF demodulator 2 and possibly. CVBS signals present via signal processing. The sound is filtered out separately and after processing in the two audio channels NF1 and NF2, an audio frequency modulator 4 supplied. The output side is the BIL-IF modulator with the output converter 5 connected, the applied intermediate frequency either in channels of the VHF or UHF range implements. The output converter instructs to tune automatically Filter D / A converter on, which depending on the choice of output channel through one of one non-volatile memory 6 retrievable information emit a certain voltage, the one change in capacitance of the capacitance diodes of the filter circuits and thus one Change the frequency response, thereby creating the synchronous and parallel running conditions of the converter are guaranteed. Integrated in the output converter 5 are also Selective YHF and UHF amplifiers, not shown, as well as the automatic coordinated Filters and a PLL circuit for automatic setting of the oscillator frequency. The audio frequency modulation and demodulation is not discussed in more detail because these are known techniques.

According to the invention it is now provided that in the non-volatile memory 6 all the information for setting the voltage values on the voltage-controlled Components of the filter circuits and those digital values that are used for setting the Part ratios of the frequency divider of the PLL circuit when tuned to one specific channel are required. In the non-volatile memory are for each channel to be set in the input converter, which has blocks 1, 2, 3 and 4, as well as for the PLL circuit in the output converter 5, for each The corresponding information is stored separately on the output channel. Via a bus 7 the frequency-related values stored in the non-volatile memory are read out and the addressed D / A converters or the addressed dividers of the PLL circuit fed. The corresponding control takes over a microprocessor 8, which is from a Keypad 9 or setting switches (microswitches) by specifying the frequency or the channel or a digit corresponding to these characteristic values is activated. The microprocessor calls depending on the input information based on the written Program the corresponding addressed memory locations in the non-volatile memory and reads out the information and sends it to the D / A converter or to the Divider of the PLL circuit further. This is in a simple manner by pressing the The setting using the keypad or by entering the channel numbers using a switch of each input channel and each output channel in the respective frequency range possible separately.

In Fig. 2 is an output converter in the form of a block diagram shown with its essential assemblies. This is already at entrance 20 IF signal converted in the upstream input converter; It will be about one Low-pass filter 21 and a level regulator 22 are fed to a mixer 23 (fzF). On the second The mixer input is the fixed oscillator frequency fosz, which is sent from voltage controlled oscillator 24 is supplied. The dem is at the mixer output Output frequency fA assigned to the input channel, which is controlled by a three-circuit filter with voltage-controlled, adjustable resonance circuits and a downstream Amplifier 26 via a further downstream multi-filter circuit 27, which is also voltage-controlled resonance circuits open at an output preamplifier 28, which is followed by an output power amplifier 29.

The signal converted into the output frequency is transmitted via this to fed into the cable distribution system. The output 30 is for this purpose to the cable distribution network connected.

A tap is provided behind the preamplifier 28 for control purposes, which regulates the input level.

The level evaluation is housed in block 31 and provides the automatic Level regulator 22. The PLL circuit consists in a known design of a fixed Divider 31, which divides down the oscillator frequency and this a comparison circuit in the PLL circuit 32 supplies. In the circuit 32 is also known per se Way, a further divider is provided, which is set controlled by the microprocessor 33 will. A single generator 34 is provided as a reference generator, of which both the clock frequency for the microprocessor 33 as well as the reference frequency for the Oscillator 24 can be derived. In the PLL circuit 32 takes place in a known manner a phase comparison, whereby the oscillator 24 is adjusted to the set frequency will. In parallel are in a non-volatile memory, which is in the chip of the microprocessor 33 Can be integrated, the values stored for synchronism and parallel adjustment the filter circuits of the selective filters 25, 27 when the oscillator 24 is tuned a certain frequency are required. The values are when calibrating the converter entered in non-volatile memory for each channel during fabrication and are now when the oscillator 24 is set to a certain frequency of this assigned, read out and a control circuit 35, which has D / A converter, fed. As a result, the voltages UD are applied to the varactor diodes of the tunable Filter circuits and cause them to be detuned in the desired manner.

As a special feature, the embodiment according to FIG. 2 has a single one Exit on. This is provided in this form in today's high-quality systems. Output voltages of 4 V eff can be tapped from this. In contrast, are in the embodiment according to FIG. 3 - has essentially the same components As in FIG. 2 - two outputs 36, 37 with 2 V eff output voltage and 75 Ohm impedance intended. The second filter 27 is immediately in front of the outputs. switched that The first filter circuit 25 is arranged behind the mixer 23. The first as well as the second Preamplifiers are connected between filters 25 and 27. Since the execution and the Operation are the same as in Fig. 2, will not be discussed in more detail.

Claims (5)

Claims 1. Frequency converter for community antenna systems and cable distribution systems with an input converter in which the received frequency amplified or unamplified in one via single or multi-circuit filter circuits Mixer stage with a specific, generated by a voltage-controlled oscillator Frequency is mixed on which voltage controlled oscillator is used for tuning required voltage from a frequency synthesis circuit with programmable Divider (PLL circuit) or a voltage synthesis circuit is applied, and their Filter circuits can be tuned electronically if necessary and have means, a voltage to the synchronous and / or parallel operation to the tuned frequency can be applied by a voltage synthesis circuit, and that the output intermediate frequency of the input converter in an output converter with a different oscillator frequency is mixed by another voltage-controlled oscillator, which is controlled by a applied voltage from a second freely programmable frequency (PLL circuit) or voltage synthesis circuit is adjustable to the desired frequency, wherein the clock frequency for setting and reading out the programmable memories and dividers the frequency and voltage synthesis circuits of one or more reference oscillators can be derived, and the output frequency of the mixer of the output converter Filters and amplifiers can be fed into the cable network, which is not possible n z e i c h n e t that for tuning the input converter to a certain oscillator frequency one reception Channel contains the information for determining the frequency divider ratios the frequency synthesis circuit or the information for the voltage synthesis circuit are stored in a non-volatile, programmable, readable memory, and that the information for determining the division ratio of the frequency synthesis circuit or the digital values of the voltage synthesis circuit in the output converter as well are stored in a non-volatile, programmable, readable memory, and that the information stored in the non-volatile memory for the synthesis circuits in the input converter and in the output converter optionally controlled by a microprocessor readable and, depending on the choice of input channel and output channel, the frequency divider the frequency synthesis circuit or the D / A converters of the voltage synthesis circuit are supplied. 2. Frequency converter according to claim 1 with selective filter circuits in Input and output converters, which by means of electronic means (capacitance diodes) are tunable, characterized in that the digitized determined during the comparison Values of the control voltage or control currents for the electronic means taking into account the synchronism and parallel operation conditions for the individual receiving and output channels are determined and stored in a non-volatile memory, and that when voting of the oscillator to a certain frequency that of the respective receiving or output channel associated control voltage information from the non-volatile memory of the Microprocessor read out and to match the filter circuits to the upstream D / A converters are created. 3. Frequency converter according to one of the preceding claims for the first intermediate frequency of a satellite radio receiving system, characterized in that, that the received first intermediate frequency channel into a second intermediate frequency can be implemented step by step, and that the second intermediate frequency is stepwise channel can be implemented in any channel of a certain cable band. 4. Frequency converter according to one of the preceding claims with a Output converter in which the selective filter circuits are arranged after the mixer are, characterized in that a power amplifier at the output of the converter is provided. 5. Frequency converter according to one of claims 1 to 3, characterized in that that a power amplifier before the selective filter circuit located at the output is arranged.