© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 HFC Theory Oklahoma SCTE 9/12/2012 Scott Randolph

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 HFC Theory Oklahoma SCTE 9/12/2012 Scott Randolph srandolp@cisco.com Agenda - CATV & Amplifier History - Basic Amplifier Types and Operation - “dB’s” - Unity Gain - Long Loop AGC - Modulation MER/BER CNR/SNR - Amplifier /LE Set Up

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 2 CATV Then Vacuum Tube Technology: the Jerrold 12- Channel SDA-4 Super Distribution Amplifier Vacuum Tube Technology: the Jerrold HPM-12 Channel 12 Amplifier Typical Frequency Plan, 12-Channel System, One Way (1948-1989) Long Cascades Poor Powering Multiple Headends Poor or No Designs Limited Resources

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 3 CATV Now Fiber Optics Short Cascades Standby Power Supplies Increased System Reliability System Monitoring Return Path What’s The Constant??

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 7 Any doubling of power is represented by +3dB Gain Any Halving of power is represented by -3dB Loss Does This explain why I cautioned of a 3dB loss at the output of a Amplifier?? Power Push Pull Stage Push Pull Stage X -3dB

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 8 dBmV & dB “dB” is a ratio of two power levels. It indicates the Gain or Loss of a device. “dB’ is 10 times a power ratio and 20 times a voltage ratio. dB = 10Log P 1 / P 2 and Power = E 2 /R dB = 10Log (E 2 out /R / E 2 in /R ) dB = 10Log (Voltage Ratio) 2 or dB = 20Log (Voltage Ratio) “dBmV” is the unit of measurement for RF energy in a Cable Television system. 0 dBmV = 1000 mV / 75 

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 9 What is “0” dBmV??  The FCC minimum RF level to a consumers device in the home is 0dBmV.  0 dBmV is 1000 micro volts across 75 ohms. Power = V 2 /R, = (1000x10 -6 ) 2 / 75 = Example: Average Hair Dryer will draw 1000 to 1500 Watts THIRTEEN BILLIONTHS OF A WATT P ref = 13.33x10 -9 Watts How much power is represented at 0dBmV?

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 11 Equalizer Function 0 dBmV 20 dBmV 10 dBmV 50 MHz 1GHz Effect of Cable 20 dB 0 dB 0 dB 10 dB 50 MHz 1GHz Effect of Equalizer 50 MHz 1GHz The equalizer response pattern compliments the response pattern of the cable to produce a flat broad- band output signal. 10 dBmV Combined Results Results

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 12 Attenuator Function 50 MHz 1GHz 0 dBmV 20 dBmV 10 dBmV 0 dBmV 20 dBmV 10 dBmV 50 MHz 1GHz This Graph Represents a 10dBm Pad This Graph Represents a 10dBm Pad An attenuator reduces the level of the signal equally at all frequencies. An attenuator at the input of an amplifier directly affects C/N.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 13 Forward Path Set Up DC TP Input AT High Low Input Atten Input EQ Pre Amp Response Equalizer Interstage Slope Eq. ALSC Option Plug In Inter Stage Amp Dist EQ Post Amp Post Amp Pad High Low High Low High Low Signal Director DC 4-8-12 Return Combiner -5 dB Pad Return Amp Pad Interstage Atten. DC TP DC TP Input ATT DC TP

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 14 The equalizer response pattern is Designed to Compliment the response pattern of the cable. When too Much Equalization is used the Familiar “Hump” Is created ReferenceLevel 50 MHz 1 GHz Effects of Over Equalization

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 16 Forward Path Unity Gain  Unity gain in the downstream path exists when the amplifier’s station gain equals the loss of the cable and passives before it.  In this example, the gain of each downstream amplifier is 22 dB. The 750 MHz losses preceding each amplifier are 22 dB as well. For example, the 22 dB loss between the first and second amplifier is all due to the cable itself, so the second amplifier has a 0 dB input attenuator. Given the +10 dBmV input and +32 dBmV output, you can see the amplifier’s 22 dB station gain equals the loss of the cable preceding it.  The third amplifier (far right) is fed by a span that has 14 dB of loss in the cable and another 2 dB of passive loss in the directional coupler, for a total loss of 16 dB. In order for the total loss to equal the amplifier’s 22 dB of gain, it is necessary to install a 6 dB input attenuator at the third amplifier.  In the downstream plant, the unity gain reference point is the amplifier output.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 17 Reverse Path Unity Gain  Unity gain in the upstream path exists when the amplifier’s station gain equals the loss of the cable and passives upstream from that location.  In this example, the gain of each reverse amplifier is 15 dB. The 30 MHz losses following each amplifier are 15 dB as well. For example, the 4 dB loss between the first and second amplifier is all due to the cable itself, so the second amplifier has an 11 dB output attenuator. The amplifier input is +20 dBmV, making the reverse amplifier module output +35 dBmV. In order to obtain unity gain and the correct input at the first upstream amplifier location, an 11 dB output attenuator is required at the second amplifier’s reverse output so that the total loss equals the gain of the amplifier.  The third amplifier (far right) feeds a span that has 3 dB of loss in the cable and another 2 dB of passive loss in the directional coupler, for a total loss of 5 dB. In order for the total loss to equal the amplifier’s 15 dB of gain, it is necessary to install a 10 dB output attenuator at the third amplifier.  In the upstream plant, the unity gain reference point is the amplifier input.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 18 Changes to the Return Path Long Loop AGC Changing things in one part of the system may result in undesirable changes in another part of the system.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 19 Long Loop AGC Cause and Effect  Consider what will happen if the value of the attenuator at the reverse optical transmitter is increased. This will initially reduce the RF levels through the optical link, the splitter/combiner network in the hub/headend, and the CMTS upstream input. The CMTS will react to this decreased level by telling the cable modem to increase its upstream RF transmit power. The power in the coaxial plant will increase until the original level at the CMTS input port is achieved. The net result of increasing the optical transmitter attenuator will not be a decrease in the RF levels further upstream, but rather an increase in RF levels at the cable modem output and in the RF plant!

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 20 Conclusions  Return system is a loop  Unity Gain Upstream and Downstream  Changes anywhere in the loop can effect the performance of the network  Modem outputs can vary from manufacturer to manufacturer (Levels are reduced as higher Modulation Schemes are used)  Once the return laser is setup DON’T TOUCH IT Changing the drive levels can effect the window of operation of the laser  Work as a team to diagnose system problems

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 22 Per Carrier Power vs. Composite Power  As you add more carriers to the return path the composite power to the laser increases.  To maintain a specific amount of composite power into the transmitter the carrier power must be reduced.  When modulation schemes are changed the composite power into the transmitter changes. The higher the order of modulation the more energy the channel contains.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 25 CNR is a pre-detection measurement performed on RF signals Raw carrier power to raw noise power in the RF transport path only—say, a coaxial cable distribution network or a standalone device/converter or HE hetrodyneprocessor Ideal for characterizing network impairments CNR Carrier to Noise

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 26 SNR Signal to Noise SNR is a pre-modulation or post-detection measurement performed on baseband signals Includes noise in original signal, transmitter or modulator, transport path, and receiver & demodulator Ideal for characterizing end-to-end performance—the overall signal quality seen by the end user

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 28 BER Bit Error Ratio BER = number of errors / total number of bits sent BER = Number of Errors/Total Number of Bits Sent The rate is typically expressed as 10 to the negative power. For example, four erroneous bits out of 100,000 bits transmitted would be expressed as 4 x 10 -5, or the expression 3 x 10 -6 would indicate that three bits were in error out of 1,000,000 transmitted. BER is the digital equivalent to signal-to-noise ratio in an analog system. Noise is the main enemy of BER performance.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 29 Amplifier Operation and Set UP The Following Set Up Procedures will reference Cisco GainMaker RF Amplifiers. Please refer to your Equipment Installation and Operations Manual

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 31 Power Routing System Amplifier/Line Extender The red shunt should be utilized to identify the port where AC is routed into the housing.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 35 Forward Setup, GainMaker™ HGD System Amplifier, AGC, Manual and Thermal Preparation 1.Remove AC SHUNTS from module and install module into housing, tighten 4 captive screws. (For New Module Installation) 2.Leave Interstage EQ, Interstage Pad, and Output Pads as installed from the factory. 3.Install properly calculated AGC Pad (pilot freq. output level – 34). 4.Plug-In/Verify AUX DC, Splitter or Jumper as called for by design. 5.Install fwd. input Pad and EQ values as called for by design. 6.Verify AC Voltage and Cutoff jumper is in correct position, 30 volts for 60 volt systems, 40 or 50 volts for 90 volt systems. 7.Install RED AC Shunt at AC input port and Black Shunts into other ports as called for by system design. 8.Verify DC Voltage test points, located both on the power supply and module, measures 24 volts dc +/- 1 volt.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 36  Step 1. Verify adequate signal at the input of the module.  Step 2. Move test cable to Main output test point and confirm signal levels are present. HGD Step 3. Select proper setup Option using S1 (three position switch). 3.1 If Thermal setup Option (S1 in position 1) proceed to step 4. (Recommended) 3.2 If Manual setup Option (S1 in position 2) proceed to step 3.2.1. 3.2.1 Turn manual backoff pot full CCW for maximum gain. 3.2.2 Note ambient temperature. 3.2.3 Note system pilot freq. (see GainMaker Matrix for verification) 3.2.4 Refer to “Manual Backoff Chart”, Cross reference temperature and pilot frequency to determine backoff level in dB. 3.2.5 Reduce gain as specified by Manual Backoff Chart as measured at the pilot frequency, at the main output test point Step 4. Achieve specified output tilt at main output test point by adjusting the input equalizer value, or cable simulator (used in short spaced locations).

Step 6. Align AGC with the amplifier. 6.1 Measure and note signal level at main output test point of the pilot carrier frequency. 6.2 Set S1 to position 3 (normal AGC operation). 6.3 Adjust AGC gain pot to achieve pilot carrier level noted in step 5.1. (Note: AGC gain pot is not required to be set in the middle of range.) 6.4 Verify AGC setup by switching S1 between position 1, or 2 and position 3 verifying that tilt and levels do not change significantly. 6.5 Set S1 to position 3 (normal AGC operation). HGD Step 7. Verify Signal Level at AUX 1 and AUX 2 is within +/- 1 dB, as specified on line 9, measured at output test points. (AUX output minus AUX Plug-In) Step 8. Close station to specified torque of 5 to 12 ft-lb following sequence indicated on the housing.

Step 6. Align AGC with the amplifier. 6.1 Measure and note signal level at main output test point of the pilot carrier frequency. 6.2 Set S1 to position 3 (normal AGC operation). 6.3 Adjust AGC gain pot to achieve pilot carrier level noted in step 5.1. (Note: AGC gain pot is not required to be set in the middle of range.) 6.4 Verify AGC setup by switching S1 between position 1, or 2 and position 3 verifying that tilt and levels do not change significantly. 6.5 Set S1 to position 3 (normal AGC operation).

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 41 Forward Setup, GainMaker™ Line Extender With AGC Preparation 1.Remove AC SHUNTS from module and install module into housing, tighten 2 captive screws. 2.Leave Interstage EQ and Interstage Pad as installed from the factory. 3.Install properly calculated AGC Pad (pilot freq. output level – 29). 4.Install fwd. input Pad and EQ values as called for by design. 5.Verify AC Cutoff jumper in correct position, 30 volts for 60 volt systems, 40 or 50 volts for 90 volt systems. 6.Install RED AC Shunt at AC input port and Black Shunt into other port as called for by system design. 7.Verify DC Voltage test point located on the power supply and module, measures from 18 to 27 volts dc. 8.Verify DC Voltage test point located on the module measures 12 volts dc +/-1 volt.

 Step 1. Verify adequate signal at the input of the module.  Step 2. Move test cable to Main output test point and confirm signal levels are present. Step 3. Select proper setup Option using S1 (three position switch). 3.1 If Thermal setup Option (S1 in position 1) proceed to step 4. (Recommended) 3.2 If Manual setup Option (S1 in position 2) proceed to step 3.2.1. 3.2.1 Turn manual backoff pot full CCW for maximum gain. 3.2.2 Note ambient temperature. 3.2.3 Note system pilot freq. (see GainMaker Matrix for verification) 3.2.4 Refer to “Manual Backoff Chart”, Cross reference temperature and pilot frequency to determine backoff level in dB. 3.2.5 Reduce gain as specified by Manual Backoff Chart as measured at the pilot frequency, at the main output test point. Step 6. Align AGC with the amplifier. 6.1 Measure and note signal level at main output test point of the pilot carrier frequency. 6.2 Set S1 to position 3 (normal AGC operation). 6.3 Adjust AGC gain pot to achieve pilot carrier level noted in step 5.1. (Note: AGC gain pot is not required to be set in the middle of range.) 6.4 Verify AGC setup by switching S1 between position 1, or 2 and position 3 verifying that tilt and levels do not change significantly. 6.5 Set S1 to position 3 (normal AGC operation).

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 43 Forward Setup, GainMaker™ Line Extender with Thermal Control  Procedure Step 1. Verify adequate signal at the input of the module. Step 2. Move test cable to Main output port and confirm signal levels are present. Step 3. Select proper setup Option using S1 (three position switch). Switch 1 Positions Amplifier Only Amplifier and Coax Step 4. Achieve specified output tilt by adjusting the input equalizer value. (A Cable Simulator may be required in short spaced locations) Step 5. Achieve specified output level by adjusting the input pad value. Step 6. Close station to specified torque of 5 to 12 ft-lb following sequence indicated on the housing.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 45 Setting up Reverse Levels in the GainMaker™ System Amplifier and Line Extenders  Preparation Step 1. A Reverse sweep system or reverse carrier generator should be available for this alignment procedure. Step 2: Typically a reverse reference trace has been taken at the node or first amplifier from the headend. Step 3. Install O dB pads into all reverse input pad sockets. Step 4. Populate the reverse output pad and EQ locations with design values as called for on system prints.

Step 1. Inject 38 dBmV into the reverse injection test point (main forward output test point) to simulate 18 dBmV at the port. Step 2. Adjust reverse output EQ for flat response at upstream amp. Step 3. Adjust reverse output pad to match the reference trace level. Usually at the zero dB reference level. Step 4. Move injection cable to Aux 1 injection port and verify level. Step 5. Move injection cable to Aux 2 injection port and verify level. Step 6. Increase the reverse input pad on AUX I and Aux 2 ports to match the loss of a forward plug-in splitter (HGD ONLY) or coupler if used. If a jumper is used the reverse pad would remain a zero or the design value when reverse conditioning is used. Step 7. If the design print calls for additional reverse padding, then increase reverse input pad again by that amount. Step 8. Close station to specified torque of 5 to 12 ft-lb following sequence indicated on the housing.

Step 1. Inject 38 dBmV into the reverse injection test point (main forward output test point) to simulate 18 dBmV at the port. Step 2. Adjust reverse output EQ for flat response at upstream amp. Step 3. Adjust reverse output pad to match the reference trace level. Usually at the zero dB reference level. Step 4. If the design print calls for additional reverse padding, then increase reverse input pad again by that amount. Step 5. Close station to specified torque of 5 to 12 ft-lb following sequence indicated on the housing.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 HFC Theory Oklahoma SCTE 9/12/2012 Scott Randolph

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© 2007 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPresentation_ID 1 HFC Theory Oklahoma SCTE 9/12/2012 Scott Randolph

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