The use of a CATV system to provide internet, voice over internet protocol (“VOIP”) telephone, television, security, and music services is well known in the art. In providing these services, a downstream bandwidth (i.e., radio frequency (“RF”) signals, digital signals, and/or optical signals) is passed from a supplier of the services to a user, and an upstream bandwidth (i.e., radio frequency (“RF”) signals, digital signals, and/or optical signals) is passed from the user to the supplier. For much of the distance between the supplier and the user, the downstream bandwidth and the upstream bandwidth make up a total bandwidth that is passed via a signal transmission line, such as a coaxial cable. The downstream bandwidth is, for example, signals that are relatively higher in frequency within the total bandwidth of the CATV system while the upstream bandwidth is, for example, signals that are relatively lower in frequency.
Traditionally, the CATV system includes a head end facility, where the downstream bandwidth is initiated into a main CATV distribution system, which typically includes a plurality of trunk lines, each serving at least one local distribution network. In turn, the downstream bandwidth is passed to a relatively small number (e.g., approximately 100 to 500) of users associated with a particular local distribution network. Devices, such as high-pass filters, are positioned at various points within the CATV system to ensure the orderly flow of downstream bandwidth from the head end facility, through the trunk lines, through the local distribution networks, and ultimately to the users.
At various locations between the head end facility and the user, there are amplifiers and slope adjustment devices for the purpose of maintaining the quality of the downstream bandwidth. This statement introduces three terms (i.e., quality, amplifiers, and slope adjustment devices) that are important to the remaining discussion. These will be discussed broadly below.
The quality of the downstream bandwidth is often a measure of: (i) a signal level of a particular channel within the downstream bandwidth, the signal level referred to merely as “level;” and (ii) a general consistency of levels across all of the channels in the downstream bandwidth, the general consistency referred to as “slope.” These objective measurements are often used by technicians to evaluate CATV system performance during operation and to troubleshoot customer complaints.
The level of each channel should fall within a specific range that has been determined to provide satisfactory video, sound and information transfer rates for users. The specific requirements for each channel are not of importance to the present discussion, but it is helpful to understand that are specific targets for the level of each channel. Note that this is a simplistic definition to explain “level,” and note that this definition does not include other variances such as between analog and digital.
Slope is measurement used to assess the amount of loss experienced due in large part to cable length. While all channels experience some loss, channels transmitted using higher frequencies within the downstream bandwidth experience more loss than those transmitted using lower frequencies. Accordingly, when the levels for all of the channels within the downstream bandwidth are graphed such that they are arranged in order according to the frequency of the channel, there may be a significant visual downward slope in the graph from the lowest frequency channel to highest frequency channel. This downward slope becomes more prominent as the length of signal cable increases. Note that this is a simplistic definition to explain the consistency of levels across all of the channels and the “slope” that is created by losses occurring in the signal cables. Also note that this definition does not include other variances such as between analog and digital.
The presence of slope is not removed through the use of typical drop-style amplifiers. The drop-style amplifiers merely amplify the entire downstream bandwidth. In other words, these drop-style amplifiers raise the level of each channel equally. In turn, if there is a large amount of slope present, such as when a user's premise includes long distances of signal cable, the drop-style amplifier may cause some channels to exceed their level specification while other channels may remain below their specification.
It is known to add a fixed or manually adjustable slope compensator/low frequency attenuator when there is a long run of signal cable. However, these devices require expensive testing equipment to determine whether and/or how much slope compensation should be supplied to a particular premise. Further, due to the cost of installation and a general misunderstanding regarding how to install such devices, there are relatively few in existence, compared to the number of such devices needed.
For at least the forgoing reasons, a need is apparent for a device, which can increase the overall quality of the downstream bandwidth that includes providing an appropriate amount of amplification and an appropriate amount of slope compensation increasing the signal strength and increasing the signal-to-noise ratio.