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DOCSIS Subscriber Transceiver

* It is intended for arrangement of a wireless "reverse channel" data transmission and forward channel reception from a base station.   It is installed at subscriber's place where the Internet service of the DOCSIS standard is delivered
* Operability of the subscriber transceiver is provided within the radius of from 1 to 28km when having the head equipment antennas   with the gain=12dB and the subscriber equipment with the gain=27dB.
* It tolerates use of external reflectors with a different gain
* Hermetic case


Structure scheme of DOCSIS subscriber transceiver

DocsisAnt.jpg
Antenna with antenna feed


   Power supply device PS-105F                                Subscriber transmitter-receiver converter

Product specifications
Transmitter Output signal frequency range 2305 - 2325 MHz
Input signal frequency range 28.0625 - 48.0625 MHz
Maximum output power 0.2 W
Gain 23 dB
Input signal level -37...+8 dBm
Out-of-Band Emission Level when output power is 100mW not worse -60 dBc
Heterodyne oscillator frequency 2276.9375 MHz
Heterodyne oscillator phase noise while tuning out to ± 100 kHz not worse -100 dBc/Hz
Heterodyne oscillator frequency departure under the influence of all destabilizing factors not more ± 3 kHz
Operation mode switched by input signal level
Signal power to transfer to transmission mode -42 dBm
Receiver Input signal frequency range 2500 - 2700 MHz
Output signal requency range 470 - 670 MHz
Gain 31 dB
Noise ratio 4 dB
Heterodyne oscillator frequency 2030 MHz
Heterodyne oscillator phase noise while tuning out to ± 100 kHz not worse -100 dBc/Hz
Heterodyne oscillator frequency departure under the influence of all destabilizing factors not more ± 3 kHz
Operation mode continuous
Third degree intermodulation product level when output level of each of the two signals is 1dBm not worse -55 dBc
Common features Voltage supply/Consumption current +15V/0.27A ... +24V/0.17A
Ambient temperature -30...+50
Relative air humidity up to 100%
Weight 1.1 kg
Dimensions 210x175x80 mm
Connector "Modem input-output" F-type
Connector "Antenna input-output" N-type

Example of Over-the-Air Internet Network Arrangement for Different Distances

     Let us consider the system of over-the-air Internet network arrangement in the DOCSIS standard with the help of a DOCSIS subscriber transceiver, a DOCSIS head transceiver (produced by Beta TV com), a head cable modem (CMTS) and a subscriber cable modem (CM).
     Connection scheme (distance between the head-end and a subscriber's place is 1...28km; a recommended subscriber antenna gain is 27dB, base station antenna gain is 12dB):

Dop_Abon_transceiver_DOCSIS.jpg

     Provide signal injection of a forward channel from the CMTS output to the DOCSIS head transceiver input from -27 dB/mW to -2 dB/mW (it is the AGC system operability range in the DOCSIS head transceiver). afterwards the transformed signal of a forward channel in the frequency range of 2500...2524 MHz with a 300mW level arrives to a combined antenna 13/ 360.
     When having the a drop cable loss of 3 dB over a reverse channel (between the DOCSIS head transceiver and the CMTS; 100m of an RG-11 cable provide the loss of 3 dB) and the signal level of -47dB/mW supported by the CMTS at the forward channel input (if the level is lower the CMTS transfers a command to the subscriber modem to increase its output level, if the level is higher the CMTS transfers a command to decrease the level) the signal level at the antenna TA 13/ 360 output is -74 dB/mW (when the level of the noise applied to the DOCSIS head transceiver input is ~ -113 dB/mW in a 3 MHz band and the necessary SNR for a QPSK modulation is 16 dB the store for weather conditions is 23 dB: - 113+ 16 +23 = -74 dB/ mW).
     The forward channel power arriving to a subscriber antenna from the transmitter-receiver converter output is ?30 mW (100 mW is the maximum signal power) at a 28km distance.
     Taking into account the subscriber transmitter-receiver gain of 23 dB the forward channel signal level on its modem input-output is ? - 8 dB/mW (at the distance of 28 km). At the distance of 1km the forward channel signal level at its modem input-output is -38dB/mW. (we remind that output stages of forward channel transmission amplifier are de-energized in the subscriber transmitter-receiver converter while having a reverse channel signal value less than the value of 42 dB/mW).
     The cable modem has the maximum reverse channel output level of 10 dB/mW and the minimum level of 60 dB/mW. Thus a loss store in the drop cable at subscriber's place over a reverse channel is 18 dB (i.e. the drop cable length may be longer than 100m while using a cable RG-6; the RG-6 has the loss of -8,8 dB/100m on a 100 MHz frequency). Let us define the maximum length of the RG-6 cable from a probability of the maximum voltage dip applied from a power supply PS 105F over a centre core to the transmitter-receiver converter. Taking into account that consumption current of the subscriber converter is 0,3A, resistance of the RG-6 cable is 110 Ω/km and a probable voltage dip is 9V (from 24 to 15V) we get the maximum length of the RG-6 cable about 300m.
     Let us consider signal pass of the forward channel.
     The signal level at the subscriber transmitter-receiver converter input is -65 dB/mW (for the distance of 28km between a subscriber and the head-end) when having the forward channel output power of 300mW at the base station and of 27dB and 13dB at the subscriber antenna and the head-end antenna correspondently.
     While having a 108 dB/mW level of the noise applied to the subscriber transmitter-receiver converter input in a 8MHz band and the necessary SNR of 30dB for a QAM-64 a store for weather conditions is 13dB: - 108+30+13 = -65dB/mW.
     Transfer ratio of the subscriber transmitter-receiver converter over a forward channel is 31 dB. Thus the forward channel signal at the modem input-output of the subscriber transmitter-receiver is -34dB/mW (cable modem operability range over the forward channel is from -67dB/mW to -7 dB/mW; the forward channel signal at the modem input-output of the subscriber transmitter-receiver is -4dB/mW at a 1 km distance between a subscriber and the head-end; note that the subscriber transmitter-receiver converter is overloaded when having the level of 1:0 dB/mW). Thus the drop cable loss store over the forward channel at subscriber's place is about 33 dB.
     Use this reasoning while using data transmission at the distance of less than 1km. A subscriber antenna with a less gain should be used. An input subscriber transmitter-receiver attenuator of -10dB may be used to prevent the subscriber transmitter-receiver converter overloading over the forward channel.