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 Introduction:
Traditional Cable Television Systems had long been associated with one way downstream
signal transmissions that provided video services to customers. The return
path, when utilized, had been used primarily for PEG (Public, Educational,
Government) channels, which transmitted the signal from a remote site such
as a school or city hall back to the headend for retransmission on the downstream.
As customers demanded more channels and services
the bandwidths of the systems have continually increased to 860MHz, with
higher gain amplifiers, increased tilt and utilization of the return
bandwidth in the entire system for high-speed data and telephony services.
With the use of higher bandwidths and the addition of new services has
come the requirement for tighter tolerances in both the downstream and
upstream signals in order to maintain quality service to the customer
and meet FCC Technical Specifications. With the use of the return band
has come the challenge of controlling ingress and noise, which affects
the reliability of the upstream signals. To maintain these tighter tolerances
and control ingress and noise in the return path requires some unique
and creative solutions that are found in Antronix taps with the E-Option.
E-Option Taps
E-Option Taps have the capability to accommodate a variety of plug-in modules
that allow the conditioning of the system in either the downstream or upstream
for optimum system performance. E-Option allows each tap location to be conditioned
individually for its specific requirement, conditioning only the tap ports
without affecting the through insertion loss (see fig 1). E-Option solves design
challenges such as return
path ingress and noise reduction, negative/positive tilt compensation and high/low
passive return path loss.
Full Bandwidth Cable Equalizer (CE): The cable equalizer
is used to equalize the entire bandwidth from 5 to 1000MHz. The cable
equalizer is normally used on taps toward the end of the line. The advantages
of this equalizer are:
- It allows the system to have full equalization from 5 to 1000MHz
independent of the return bandwidth or split.
- It equalizes the forward bandwidth to overcome excessive negative
tilt associated with long coaxial lines allowing
the distribution line to be extended.
- It conditions the tap ports for the correct signal levels for proper
set-top operation and to meet FCC Technical specifications.
- It adds attenuation on the return path allowing cable modems to
operate at a higher output and lowers the noise/ingress coming from
the customers premise, achieving a greater signal to noise/ingress
on the return path.
- It is available in a variety of values to meet your design criteria.
Cable Simulator (CS): The cable simulator is used in
the latest system designs that are utilizing high output amplifiers allowing
the full use of the amplifier gain with large positive tilts. The cable
simulator is normally used in the first few taps after an amplifier. The advantages
of the cable simulator are:
- It simulates a fixed amount of cable thus overcoming excessive positive
tilts.
- It conditions the tap ports for correct signal levels for proper set-top
operation and to meet FCC Technical Specifications.
- It is available in a variety of values to meet your design criteria.
Return Path Block Attenuation (RA): The return path attenuator
is used in systems deploying high speed data services that are utilizing the
return path. The return path attenuator is normally used in low value taps toward
the end of the distribution system which have low loss in the return path. The
advantages of the return path attenuator are:
- It adds attenuation in the return path without affecting the forward path
allowing the cable modem to operate at a higher output level increasing the
carrier to noise/ingress ratio.
- It attenuates any ingress or noise coming from the subscriber premise thus
improving the reliability of the return path.
- It prevents the return fiber transmitters from going into clipping.
- It is available in a variety of values to meet your design criteria.
High Tap Value Plug-in (HT): The High Tap Value Plug-in is used
in system designs that are utilizing amplifiers with high outputs, high value
taps and cable modems. The advantages of the High Tap
Value Plug-in are:
- It lowers the return path attenuation in high value taps allowing the cable
modem to overcome the large passive loss associated with these taps.
- It increases the carrier to noise/ingress of the cable modem signal.
- It is available in a variety of values to meet your design criteria.
High Pass Filter (HP): The High Pass Filter is used in systems
deploying cable modem services. The advantages of
the high pass filter are:
- It eliminates ingress and noise generated from the customer premises from
getting into the return path.
- It allows high pass filtering on all tap ports using one filter.
- Cost savings, one filter verses 2, 4 or 8.
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