New-Tech Europe Magazine | June 2016

attenuation slope is adjustable via an analog control signal. This component offers significantly increased versatility under the widely-varied operating conditions to which CATV systems are subjected. An “intelligent” control system can tune the voltage-variable equalizer’s (VVE) frequency response on the fly, continually adapting to changes in operating parameters, and maintaining peak system performance. Figures 2 and 3 illustrate the performance of a simplified hypothetical CATV system (consisting of two Mini-Circuits PGA-106-75+ amplifiers and 100 feet of RG-6/U coaxial cable). The red plot shows the gain of this system without the equalizer, and the blue plot shows the gain of this system with Mini-Circuits’ VAEQ-1220-75+ voltage-variable equalizer inserted. In this simulation, a tuning voltage of 3.05 volts is applied to the VVE through its control input. In this hypothetical system, the VAEQ- 1220-75+ reduces a slope of about -20 dB to a nearly flat region. While this model has a particularly flat response within the DOCSIS 3.1 downstream band—up to 1220 GHz (and change)— it is also operable down to 5 MHz. The VAEQ-1220-75+ is designed for use in 75Ω systems and is operable over the entire DOCSIS

Figure 2 Implementation of AT Safeguards

that component performance varies with temperature, manufacturing tolerances, humidity, the installation technician’s choice of breakfast on the preceding Tuesday, and so on. So, an equalizer that exhibits an optimal attenuation slope for 300 feet of Manufacturer A’s coaxial cable, roasting at high noon during a Texan summer, might not work so well with 50 icicle-draped feet of Manufacturer B’s cable in Maine. A designer may choose to design into her or his system a switchable bank of equalizers, which may be inserted into the signal path as

necessary, but a discretized solution like this can rapidly turn cumbersome. Because the “amount” of positive slope needed to effectively flatten the gain of a particular system will vary depending on cable length, amplifier performance, gain/attenuation variations thereof over temperature, and myriad other system parameters, passive equalizers are applicable to relatively narrow regimes of operating conditions. A tunable solution, on the other hand, would be highly desirable. Mini-Circuits’ VAEQ-1220-75+ offers exactly that—an equalizer whose

Figure 2: Hypothetical CATV transmission system including equalizer

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