Microwave integrated teleradioinformation MITRIS system (Transmitting part)
A low-power MITRIS system is intended for channel "shifting" from the main head-end to new locations for a distance of 8km. It is impossible to use digital tuners in the new locations because signal reception is conducted by analog tuners from a low-power MITRIS system. The price of this system can be compared to the price of digital tuners.
* The system is compatible with the existing cable networks and is intended for a directive transmission of
TV signals from the main head-end for a distance of 8-20km
* A broad frequency range provides transmission of great information streams over-the-air, including digital
streams from IKM-15, IKM-30 telephone multiplexers, etc.
* It occupies an intermediate position between television market and telephony market
* It is based on use of frequency modulation
* Compact design
* Delivery set for MITRIS-5: AVT-300F modulator - 5pc, UCA-5 up-converter - 1pc, dish 0.6m - 1pc,
power supply device 12V - 1pc, infeed - 1 pc
|Operating frequency range||11.70 - 12.2 GHz|
|Video input||frequency band||20 Hz - 6 MHz|
|level/impedance||1V / 75 Ω|
|Audio input||frequency band||20Hz - 20 kHz|
|Frequency band width of one radiochannel||30 MHz|
|Frequency spectrum step||50 MHz|
|Frequency modulator output level||100 dB/µV|
|Depth of control of frequency modulator output Level||20 dB|
|Power emitted "on-air" by one radiochannel (while transmitting 10 TV channels)||2 mW|
|Emitted radiochannel polarization||linear|
|Voice subcarrier of each radio signal not higher||3|
|Heterodyne oscillator stability in a -50...60îÑ operating temperature range||2.5x10-5|
|Heterodyne oscillator signal suppression in output signal spectrum not less||20 dB|
|Harmonic and compound signal suppression at the transmitter output not less||50 dB|
|Transmitting antenna diameter/Antenna gain||0.64m / 35dB|
A MITRIS receiving part comprises standard satellite equipment: a dish antenna and analog tuners (see the fig. at the left side) or a SAT receiver SR-100, manufactured by Beta TV com. The explanation of this part's operation is not necessary.
A Supposed Procedure of Operation with MITRIS System Transmitting Part.
Inject group signal from frequency modulator outputs to an up converter (see fig.1). Signal levels of each modulator at the up-converter input should be set according to the table given in the MITRIS datasheet. It should be done with the help of an output level adjuster on a faceplate of every modulator or with the help of an additional continuous attenuator which can reduce group signal. (A device LFM-320 or an analogous one can be used for measuring). While having the set output levels, signal power is the same for each channel at the up-converter output. The signal power amounts to 2 mW (level spread of signals arriving to the up-converter is caused by amplitude frequency response unevenness of a transmission path and the up-converter).
Power equalization at the up-converter output is needed for a qualitative signal reception. The dynamic range of a receiving converter is not high because of its higher gain of ≈40...50dB. Its dynamic range amounts approximately to 10 dB and ranges (output) from 41dB/µV (for a channel) to 51dB/µV (for a channel). The information is given for a AP8-74C converter of the company MICROELECTRONICS TECHNOLOGY. (The lower level of dynamic range is defined by converter noise power led to the input - Ueff.n ≈8dB/µV and the necessary store of SNR which amounts to 33dB. Altogether 33+8=41dB/µV. The upper level is defined by the maximum possible output amplifier level of a receiving converter IMA3 of which is 100dB/µV according to DIN 45004. While having 10 channels the maximum output level for a channel is a bit higher than 93 dB/µV. While having a 40dB gain of the ÀÐ8-74Ñ converter the upper level amounts to 93-40=53dB/µV and dynamics amounts to 53-41 ≈10dB. Irregularity of the ÀÐ8-74Ñ receiving converter is slight, not more than 1dB. That is why it was not considered in the description above).
Thus while using the ÀÐ8-74Ñ receiving converter the signals at its output should be within the limit of 41+40=81 dB/µV to 53+40=93 dB/µV for a channel (the control can be effected by connecting a LFM-320 device to the output of the receiving converter). In case of an 93dB/µV upper threshold excess the group signal power at a sending end should be lowered (with the help of a group signal continuous attenuator). If a signal level at a receiving-end is lower than a lower threshold give consideration to a more precise transmitting and receiving antenna orientation or change the secondary radiators to those with a greater diameter. Use the description given above while using receiving converters of other companies.