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Hfc g rf amplifiers Hfc g rf amplifiers Presentation Transcript

  • Broadband System - G Satellites are spaced every 2nd degrees above earth"C" BandToward satellite 6.0 GHz "L" BandToward earth 4.0 GHz Toward satellite 14.0 GHz Toward earth 12.0 GHz TV TRANSMITTER Headend Cable area 1 RF Amplifiers.
  • RF amplifiers 2
  • RF AmplifiersThe quest for the ideal RF amplifier.•The basic function of a power amplifier is always the same: to boost a low-power signal to a higher power level, to be delivered to the amplifier load.Because that role is so fundamental, its tempting to view amplifiers assimple black-box devices, with an input, an output, and a constantamplification factor. In many instances, the black-box approach provides anadequate picture.•It fails, however, when the demands placed on an amplifier are extreme.•Hardest to satisfy is the requirement for maximum capability of two or moreconflicting parameters, such as the demand;• For broad bandwidth, 870 to 1,000 MHz.•High power in the same package, output at 46.0 to 48.0 dBmV. 3 View slide
  • RF Amplifiers•Selecting the right amplifier, usually require a forward and a return path. Theforward amplifier required for today’s needs are either: 50 to 750, 50 to 870 and50 to 1,000 MHz bandwidth.•The return path can be from: 5 to 40 / 42 or 5 to 65 MHz. 5 40 50 750 870 1,000 5 65 85 750 870 1,000 4 View slide
  • RF AmplifiersBi-directional filters on RF amplifier, can causes some problem on channel 2.This Problem is caused by the bi-directional filter, retarding the informationbetween the Picture Carrier of channel 2, situated at 55.25 MHz and the ColourInformation, situated at 3.59 MHz above the picture carrier or 58.84 MHz. Thisproblem is called Group Delay. The group delay specification is given innanosecond.In most modern RF amplifier, the Group delay is around 30 nanosecond peramplifier at channel 2, the delay gets better as we increase in frequency. Ifthis retard goes beyond 250 nSec due to cascading RF amplifiers, you’ll seethe colour not been display properly inside the picture.A 10 amplifiers cascade with a 30 nanosecond would give a 300 nSec groupdelay, which could mean problem. 30 nSec 5
  • RF AmplifiersType of amplifications Circuit used in modern RF amplifiers; Single ended transistor Single ended transistor Push Pull transistor o 180 Push Pull transistor o Power Doubling 180 transistor o 180 o 180 To day’s Circuitry can be: •Push pull •Power Doubler •GaAs 6
  • RF Amplifiers•Today RF amplifiers requires a lot of gain. It is not rare today to see amplifiersoperating between 30 to 45 dB of gain at 750, 870 or 1,000 MHz.•They also requires a high output level, between 42 to 48 dBmV a their highestfrequency.•The need for high gain amplifier is mainly because, it is more economical tokeep the old amplifiers location and just replaced old amplifier by newamplifiers with the required gain.•Most of today amplifiers utilised either Power Doubling or GaAs amplificationcircuit at their output stage. GaAs circuit gives a 3 dB better output capabilitythat a Power Doubling circuit.•GaAs amplifiers also have a higher compression point than Power Doublingamplifiers. 7
  • RF Amplifiers Yesterday’s amplifier Today’s high gain amplifier to status Fuse monitoring -20 dB EQ Fuse Input IC Output IC Pad Variable Variable JXP RF/ RF Gain Tilt AC AC -20 dB Possibility of Fuse RF Splitter or RF/ EQ JXP BODE BRD JXP AC RF 7, 10, 12 dB AC coupler ADU JXP -20 dB Input IC Output IC Manual JXP Variable Variable RF/ Gain RF Pad Gain Tilt AC AC 5 Control -20 dB 40 Possibility MHz MHz of a 3th ICS JXP RF output 5 40 fromFuse MHz MHz status Fuse monitoring -20 dB -16 dB AC / DC Power Supply fuse ICS fuse EQ JXP JXP Drive 24 Vdc to status Power vcc monitoring Supply -20 dB Fuse fuse 90 / 60 Vac fuse ICS JXP They were called TRUNK / BRIDGER These amplifiers comes amplifier. The BRIDGER and a completely equipped with distribution selector were added for either 2 or 4 outputs. The only local signal distribution. Often a AGC/ASC module was also needed module that can be added is a to control its output level. level. AGC or a TLC module. 8
  • RF AmplifiersRequired gain for RF amplifiers, where we want to keep the same amplifier location, while upgradingan HFC system to a higher operating frequency.For an upgrade from 550 MHz to 870 MHz, the new amplifier will require a 34.2 dB gain, when the old requireamplifier was operating at a 32.0 dB gain. These calculations are only for TRUNK amplifiers without multitap Required gain for the RF section of a HFC system This spread sheet will calculate the required gain, of the RF amp. when you want to keep the amplifiers at the same location, while doing a frequency upgrade on a HFC sysem. These calculations are only for replacement of TRUNK amplifiers without multitaps. Actual Gain : 32.0 dB @: 450 550 750 870 1000 MHz Amp. Enter gain of the amplifier. ENTER Loss System Dist. Mt. Amp. dB Spacing Betw een GAIN. 100 m t. MHz Am p. 4.43 450 722.5 32.0 dB 35.6 dB 42.2 dB 46.2 dB 49.1 dB 4.92 550 650.2 32.0 dB 38.0 dB 41.6 dB 44.2 dB 5.84 750 547.9 32.0 dB 35.1 dB 37.2 dB 6.40 870 500.2 32.0 dB 34.0 dB 6.79 1000 471.2 32.0 dB Above distances and losses are with 625 P-III Cable The gain should be the same for any type of P-III cable. 9
  • RF AmplifiersRequired gain for RF amplifiers, where we want to keep the same amplifier location, while upgradingan HFC system to a higher operating frequency.For an upgrade from 550 MHz to 870 MHz, the new amplifiers will require a 28.6 dB gain, when theold amplifiesr were operating at a 22.81 dB gain. These calculations are only for distribution amplifiers with multitap This program will calculate the loss between L.E. with multitaps Present amplifier gain @ 450 MHz 1.63 dB loss 100 Enter : 1.63 for 500-P-III 1.35 for 625-P-III dBmV 1.63 1.63 1.63 1.63 1.63 1.63 1.63 distance 0.9 100 0.8 100 1 100 1.4 100 1.4 100 1.9 100 4 100 Input 700 43.00 29 26 23 20 17 14 10 20.19 ft 14 14.47 15.04 15.41 15.38 15.35 19.08 < output at multitap gain Present amp. Gain. 22.81 dB Required amplifier gain @ 750 - 870 MHz 2.34 dB loss 100 Enter : 2.16 for 500-P-III @ 750 M Hz 2.35 for 500-P-III @ 870 M Hz dBmV 2.34 2.16 2.16 2.16 2.16 2.16 2.16 distance 1.3 100 1.3 100 1.2 100 1.6 100 1.7 100 1.9 100 4.3 100 Input 700 46.00 29 26 23 20 17 14 10 17.40 15.7 16.36 15.9 15.54 14.78 13.92 18.18 < output at multitap With 64 QAM @ 870 M Hz gain 28.60 Amplifier dB gain required to upgrade the system from 450 to 750 M Hz. With 64 QAM @ 870 M Hz 28.60 dB 10
  • RF Amplifiers•Example of RF amplifiers on a system operating at 300 MHz with 32 dB gain,where the RF amplifier are keep at the same location for a new system operation at750 MHz.•These new amplifiers will require a 36.3 dB gain at 750 MHz to expand the passingband to 750 MHz from 300 MHz. 32 dBmV 32 dBmV 28 dBmV 28 dBmV 19 dBmV 10 dBmV 50 MHz 300 50 MHz 300 50 MHz 300 22 dB spacing at 300 MHz 48 dBmV 48 dBmV 23.6 dBmV 38 dBmV 38 dBmV 11.7 dBmV 50 MHz 750 50 MHz 750 50 MHz 750 36.3 dB spacing at 750 MHz 11
  • RF AmplifiersSo for and upgrade in frequency for CATV-HFC system, you’llneed to calculate two different amplifier gain:•One gain for the TRUNK amplifier section.•One gain for the LINE EXTENDER section.•With the LINE EXTENDER section, it could also mean toreplace multitap with different value. We will see this in a latersection.Let have a look at the different amplifiers possibility. 12
  • RF Amplifiers A Four Outputs, High Gain Amplifier. 870 MHz 50 870 MHz MHz 50 MHz to status monitoring -20 dB870 50MHz MHz 870 MHz 40 JXP RF/ MHz 5 RF MHz AC AC 50 MHz -20 dB 5 40 -20 dB MHz MHz JXP RF/ RF AC AC RF/ EQ JXP BODE BRD JXP -20 dB AC RF AC JXP RF/ RF AC AC -20 dB ADU JXP Manual JXP RF RF/ Gain AC AC 5 Control -20 dB 40 MHz MHz ICS JXP 5 40 from fuse MHz MHz status -20 dB monitoring -20 dB ICS JXP -16 dB fuse -20 dB fuse ICS EQ JXP JXP Drive ICS JXP 24 Vdc fuse to status Power vcc monitoring Supply -20 dB fuse 90 / 60 Vac fuse ICS JXP 47 dB gain, minimum full @ 1,000 MHz. 13
  • RF Amplifiers A Dual or Three Outputs, High Gain Amplifier. 870 MHz 50 870 MHz 50 MHz MHz to status monitoring -20 dB870 50MHz MHz 40 JXP RF/ 870 MHz 5 RF MHz MHz AC AC 50 -20 dB MHz Possibility of 5 40 RF Splitter or MHz MHz RF/ EQ JXP BODE BRD JXP AC RF 7, 10, 12 dB AC coupler ADU JXP -20 dB Manual JXP RF/ Gain RF AC AC 5 40 Control -20 dB MHz MHz Possibility of a 3th ICS JXP RF output 5 40 from MHz MHz status monitoring -20 dB -16 dB fuse ICS fuse EQ JXP JXP Drive 24 Vdc to status Power vcc monitoring Supply -20 dB fuse 90 / 60 Vac fuse ICS JXP 47 dB gain, minimum full @ 1,000 MHz. 14
  • RF Amplifiers A One Output, High Gain Amplifier. 870 MHz 870 50 MHz 50 MHz MHz to status monitoring -20 dB 87050 MHzMHz 40 MHz 5 JXP RF/ RF MHz AC 870 AC MHz -20 dB 50 MHz RF/ EQ JXP BODE BRD JXP 5 40 AC RF MHz MHz AC ADU JXP Manual Gain 5 40 Control -20 dB MHz MHz 5 40 ICS JXP fuse MHz MHz from status monitoring -20 dB -16 dB fuse ICS EQ JXP JXP Drive to 24 Vdc status vcc Power monitoring Supply 90 / 60 Vac fuse 38 dB gain, minimum full @ 1,000 MHz. 15
  • RF Amplifiers RF Input of a Modern Amplifier. 50 108 121.25 225 300 450 550 750 870 MHz MHz MHz MHz MHz MHz MHz MHz MHzSignal after proper equalizer 16
  • RF Amplifiers RF Output of a Modern Amplifier. 48.5 dBmV 47.0 dBmV 10 dB 11.5 dB 6 dB4 dB 37.0 dBmV 50 108 121.25 225 300 450 550 750 870 MHz MHz MHz MHz MHz MHz MHz MHz MHz 17
  • RF Amplifiers•Because coaxial cable is frequency dependent, the loss at highfrequency (750, 870 or 1,000 MHz) is much higher than at lowerfrequency, 50 MHz, something like 4.2 to 1 for 750 MHz system, 4.6 to 1for 870 MHz system and 4.9 to 1 for 1,000 MHz system.•This difference will cause a big difference in level at the input of thenext amplifier. With this big difference in level between the LOW andHIGH frequencies, the next amplifier will require a cable equalizer at hisinput, the equalizer will bring all the signal at a flat level before hittingthe first amplification circuit.•When temperature change are high, it is a good practice to equipped RFamplifier with a AGC circuit. (Automatic Gain Control) Level change due to temperature changes. Signal after equalizer. 18
  • RF Amplifiers with an AGC control. Input next amplifier after 30 dB spacing at 870 MHz 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 31 31 30 30 29 29 28 28 27 27 26 26 25 25 Temperature 24 24 Swing @ 870 MHz -40 o From - 40 C to + 40 C 23 23 22 22 20 o 21 21 20 20 40 o Temperature 19 alizer 19 r cable equ Swing @ 300 MHz Signal afte 18 18From -40 C to + 40 C 17 Signal after cable equalizer 17 16 16 Signal after cable eq ualizer 4 15 9 15 9 . 14 14 2 5 13 13 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 19
  • Powering RF AmplifiersToday RF amplifiers requires between 40 to 90 volts AC to operates properly.This voltage is generally supplied by a UPS power working off the power lineat 110 volts AC or from a non-standby power supply also working at 110 VAC. Coaxial Coaxial RF and AC Power RF and AC Inserter Batteries 110 Volts AC 20
  • Powering RF Amplifiers•Powering an HFC system.•The first thing to know about powering a HFC system, is to only utilized80% of the capacity of the AC Power Supply. If a Power Supply is capableof delivering 15 amperes, 80% of 15 amperes will be 12 amp. This willpermit a reserve for the warm day of summer, where the coaxial cablelosses get higher, then drawing more amperage.•In the future, a broadband system, will also require more utilisation of ACpower, mainly because we will be installing active equipment on the side ofeach home. This active equipment will require AC voltage that will be feedby the drop wire to supply VoIP telephony, Cable modem services, Paytelevision, Security services, and other types of services.•One more thing that will be required from the AC power supply, is able todeliver at less 6 hours of standby time, giving the technician, time tocomes and hook up a gasoline generator, to make sure the system is keepin operation at all time.•By doing the above, we will be able to meet the 99.99999% working time,demanded by some insurance and protection company. 21
  • Powering RF AmplifiersThere is two ways to supply the require AC to a cascade of amplifiers. Theoldest and most utilized way is called Standard Powering P.S, where the P.S.converted 110 VAC to either 60 or 90 VAC. To day, the industry usesstandby-by P.S. where batteries supply DC voltage that is then converted inAC voltage. Should be Should be above above 40 VAC 40 VAC 15 Amps Standard 15 Amps Power Supply 60-90 60- Coaxial cable with 1 output VAC AC Powering stop 22
  • Powering RF Amplifiers A new way to supply AC to a cascade of amplifier is called Centralized Powering, where the UPS are installed in a centre location, where the AC is feed thru a special cable called « Power cable ». Should be Should be 40 VAC 40 VAC24 Amps Power Supply Should bewith two 12 Amps output 50 ohms 40 VAC Should be 40 VAC Powering Cable AC Powering stop 24 24 24 Amps Amps Amps 60-90 VAC 60-90 VAC 60-90 VAC Gas Generator main powering plan 23
  • Powering RF Amplifiers Mechanical Description Power 50 Power 30 Power 20 (nominal) POWER CABLE. 0.218 0.320 0.345 Inner Conductor (Inches) Solid Copper Copper-Clad Copper-Clad Power cable is a different Inner Aluminium Aluminium Conductor type of coaxial cable than Dielectric Diameter 0.563 0.563 0.515 the one used for CATV 0.625 0.625 0.625 Outer Conductor Seamless Seamless Seamless system. This cable is a Aluminium Aluminium Aluminium 50 ohms coaxial cable 0.685 Black PE Jacket Diameter 0.685 Black PE 0.685 Black Four Yellow utilized only to transport PE Stripes 60 or 90 Volts AC from a Minimum Bend Radius 4.5 8.5 7.0 centralized powering Weight lb/kft 268 233 307 centre to a cascade ofElectrical Description Power 50 Power 30 Power 20 amplifiers. The most (nominal) common type is a 625 cable, where the centre Impedance, ohms 50 30 20 conductor is different Capacitance, pF/ft 23.1 38.2 66.9 than standard coaxial Velocity of Propagation, % 87% 88.6% 79.5% cable.DC Resistance, ohms/kft @ 68F Centre Conductor 0.22 0.16 0.13 Outer Conductor 0.23 0.23 0.14 Loop 0.45 0.39 0.27 24
  • Specifications of P-III-625 vs Power CableStandard Coaxial Cable 75 ohms:Type Central Conductor DC LoopT-10-625 10- 0.137” 0.137” 1.10 ohms/1000’ ohms/1000’____________________________________________________________________________________________________________________________________Power Feeder Cable 50 ohms:Type Central Conductor DC LoopPower - 50 0.45” 0.45” 0.218 ohms/1000’ ohms/1000’Power – 30 0.30” 0.30” 0.320 ohms/1000’ ohms/1000’Power – 20 0.27” 0.27” 0.345 ohms/1000’ ohms/1000’ 25
  • Powering RF AmplifiersTo find the voltage at location 6B = 60 or 90 VAC - (VD1 + VD2 + VD3 + VD4 + VD5)VD1 = The current drawn by amplifiers: 4 – 5 – 6 - 5A -6B -6C must pass by T-10-750 (D1) in this case. T- 10- I (total) = (.94 + .99 + .95) + (5 (.45)) = 5.12 amperes I (total) X (0.00076 ohm X 2000’) or 5.12 amp. X 1.58 ohm = 7.78 Volts ACVD2 = The current drawn by amplifiers: 5 – 6 – 5A - 6A - 6B - 6C must pass by VD2 (0.99 + 0.94) + (4 X (0.45)) = 3.78 amp X 1.58 ohm = 5.67 Volts ACVD3 = The current drawn by amp. 6 - 5A - 6A - 6B - 6C must pass by VD3 = 0.94 + (4 X (0.45)) = 2.29 amp X 1.58 ohm = 3.48 Volts ACVD4 = The current drawn by amp. 6A - 6B = 0.9 amp. = 0.9 amp. X (0.00018 ohm X 800’) = 1.334 = 1.21 Volt AC VD5 =The current drawn by amp. 6B = 0.45 X (0.00018 ohm X 900’) = 1.512 ohm = 0.68 Volt ACVD6 = 60 – (7.78 + 5.67 + 3.48 + 1.21 + 0.68) = 41.2 Volts AC VD-2 VD-3 1C 2A 3A VD-1 6C 700 700 600 600 2000 2000 2000 2000 VD-6 2000 1 2 3 4 5 6 800 VD-4 800 800 700 800 1A 6A VD-5 6B 2B 4A 5A 900 800 1B 6B 60 VAC 26 Cable T-10-750 (0.00076 ohm / ft) Cable T-10-500 (0.00163 ohm / ft)
  • Powering RF AmplifiersIn most amplifiers, the AC power can be feed by any of the input or theoutput port. Adding or removing a 20 or 30 amperes fuse, will get thisamplifier to work properly. Proper fuses location will also give thepossibility to send the required AC power to the next amplifier. to status monitoring -20 dB RF & AC JXP RF/ RF AC AC RF only -20 dB Possibility of RF Splitter or RF/ EQ JXP BODE BRD JXP AC RF 7, 10, 12 dB AC coupler ADU JXP -20 dB RF only Manual JXP RF/ Gain RF AC AC 5 40 Control -20 dB MHz MHz Possibility of a 3th ICS JXP RF output 5 40 from MHz MHz status -20 dB monitoring -16 dB Fuse ICS installed fuse EQ JXP JXP Drive 24 Vdc to Power status vcc monitoring Supply -20 dB 90 / 60 Vac fuse ICS JXP 27
  • Powering RF AmplifiersAdding and removing fuses at input and output of RF amplifiers, will directhow the amplifiers will get their required AC voltage. PS Power direction Power direction in Thru position. in Thru position. Power direction in In or Out position. 28
  • RF Amplifiers Distortions.RF amplifiers are not a perfect device, they not only give GAIN, but they alsocauses some problems to the quality of the signal deliver to the HFCbroadband system.Here are some of the problems amplifiers are causing:•Second Order distortion (2nd).•Third Order distortion (3th).•Cross Modulation distortion (XM).•Composite Third Order distortion (CTB).•Composite Second Order distortion (CSO).•Noise distortion (C/N).•Hum distortion (HUM). 29
  • Response of an RF Amplifiers. Digital section Analog section 46 dBmV 45 " 44 " 43 " 42 "Return section 41 " 40 " 39 " 38 " 37 " 35 " 34 " FM 5 40 / 50 300 450 550 750 870 MHz 30
  • RF Amplifiers Distortions.A Second Order distortion is the addition or the subtraction of two (2)CW signals or two (2) television channels causing a none wantedsignal in the operating bandwidth of the RF amplifier. 46 dBmV 45 " 44 "•The formula is F1 ± F2 43 " 42 " 41 " 40 " 39 " 38 " 37 " 35 " 34 "50 870 MHz - + 31
  • RF Amplifiers Distortions. * A Second Order distortion. For every dB F1=55.25 change, the 2nd + order distortion F2=67.25 ------------ will change by 1 122.50 dBCH-2 CH-4 CH-1455.25 67.25 121.25 32
  • RF Amplifiers Distortions.A Third Order distortion is the addition or the subtraction of thefrequency of three (3) CW signals or three (3) television channels causinga none wanted signal in the bandwidth of the RF amplifier. 46 dBmV 45 " 44 " 43 "•The formula is F1 ± F2 ± F3 42 " 41 " 40 " 39 " 38 " 37 " 35 " 34 " 50 870 MHz - + 33
  • RF Amplifiers Distortions. * A Third Order distortion. F1=55.25 + F2=67.25 For every dB + change, the 3th F3=121.25 ------------ order distortion will 243.75 change by 2 dBCH-2 CH-4 CH-14 CH-2755.25 67.25 121.25 241.25 34
  • RF Amplifiers Distortions.Cross Modulation (XM) distortion is a mixing of the first side band of a TVsignal located at; 15.75 KHz, with any of the other TV signal in the spectrum.Cross modulation is always measured to a CW reference.•Cross modulation is no longer a major problem with modern amplifier 6.0 MHz 0 % of modulation -10 -20 -30 Niveau de Transmodulation dB -40 -50 -60 -70 3.59 MHz 15.75 kh 4.5 MHz 35
  • RF Amplifiers Distortions.Composite Third Order (CTB) distortion is the addition of many third orderbeats in a 6 MHz spacing, where it become impossible to be measured as asingle beat. This problem becomes more important when a RF amplifier arecarrying more than 30 channels.The CTB gets even worse as channels are added to the system. 46 dBmV 45 " 44 " 43 " 42 " 41 " 40 " 39 " 38 " 37 " 35 " 34 " 50 870 MHz CTB Distortion 36
  • RF Amplifiers Distortions.3th Order beat versus Composite Third Order Beat (CTB). 6.0 MHz 6.0 MHz 0 0 -10 -10 -20 -20 -30 -30dB -40 dB -40 -50 -50 -60 -60 -70 -70 3.59 MHz 3.59 MHz 4.5 MHz 4.5 MHz 3th Order beat. Composite 3th Order 37
  • RF Amplifiers Distortions.Since the problem of Composite Third Order (CTB) gets worst by the numberof channels carried by the RF system, the worst channel been affected by CTBwill change depending on the number of channels the HFC system is carrying. MHz CH. Nub. Beat (4 MHz) @ CH. 54-300 36 334 11 54-450 60 1156 32 54-552 77 1983 41 54-750 110 4206 57 38
  • RF Amplifiers Distortions.Composite Second Order (CSO) distortion occurred at +0.75 and 1.25 MHzabove and below of all the TV carrier. The CSO problem is because all thefrequency of all TV channel are at : ****.25 MHz.If ch-2 freq.: (55.25) + ch-3 freq.: (67.25) give a beat at 122.50 MHz, which is1.25 MHz above ch-14 (121.25 MHz). Channel 34 (283.25) minus ch-12(205.25) will give a beat at 78.00 MHz then 0.75 MHz above ch-4 (77.25). 6.0 MHz 0 -10 -20 -30 dB -40 -50 -60 -70 3.59 MHz 4.5 MHz 39
  • RF Amplifiers Distortions.Since the problem of Second Order Composite (CSO) gets worst by thenumber of channels carried by the RF system, the television channel mostoffended, will also be at different place in the passing band of the system. MHz CH. Nub. Beat @ CH. 54-300 36 10 41 54-450 60 20 61 54-552 77 29 78 54-750 110 45 116 40
  • Signal-to-Interference Limits for Non-Coherent Carriers.Amplitude below video carrier (dB) -30 -40 Video Color Sound -50 -60 0 1 2 3 4 5 6 Channel bandpass (MHz) For good quality signal, there should not be any signal other that QAM or Video information in the YELLOW section. 41
  • RF Amplifiers Distortions. RF amplifiers distortions specifications are usually given by the amplifier manufacturer. It is very important that the following should be mentioned, when RF amplifier distortions are published.•The number of channels measured for the amplifier’s specification.•The operating level at which the distortion were measured.•For CTB and CW, the distortion should always be mentioned with CW channels.•For CTB and CSO, the number of channels should always be mentioned.•Third Order Distortion level get worst by 2 dB, when the operating level isaugmented by 1 dB. The same thing goes for X Mod, 3th Order.•Second Order has a ration of 1 for 1. The same thing goes for 2nd Order 42
  • RF Amplifiers Distortions.Since distortions level of CTB, CSO are affected by the operating levelof the amplifiers, every time we increase or decrease the operatinglevel by 1.0 dB, these distortions will be affected by:•2 dB for CTB 870 MHz•1 dB for CSO + 1.0 dB 50 MHz CTB Will increase or decrease by 2.0 dB CSO Will increase or Decrease by 1.0 dB CTB 43
  • RF Amplifiers Distortions. At an operating level; level; At an operating level; CN = 55.99 dB CN = 59.0 dB CTB = - 58.98 dB 1 CTB = -65.00 dB 2 CSO = - 61.49 dB CSO = -66.0 dBIf the operating level of both amplifier is; If the operating level of both amplifier is;Augmented by 2 dB, Distortions will be; Lower by 2 dB, Distortions will be;CN = 57.99 dB CN = 53.99 dBCTB = - 54.98 dB CTB = - 62.98 dBCSO = - 59.49 dB CSO = - 63.49 dB 44
  • RF Amplifiers Specifications. 45
  • RF Amplifiers Specifications. 46
  • RF Amplifiers Distortions.How RF amplifiers are tested for distortion measurements. AC Power Supply 47
  • RF Amplifiers Distortions.As RF amplifier are not perfect devise, they also have another problem callednoise, often called thermal noise. Noise is caused by the transistor givingamplification. Some amplifiers circuitry are causing more noise than other.Noise in a CATV Broadband system is always measure for a 4.2 MHz bandwidthand it is measured as a CARRIER to NOISE ratio. Thermal noise ratio of a perfectRF amplifier is 59.2 dB, before his noise figure is added. The noise of an RFamplifier is usually given as a dB NOISE FIGURE. 6.0 MHz 6.0 MHz 0 0 -10 -10 -20 -20 -30 -30 dB -40 dB -40 -50 -50 -60 -60 -70 -70 3.59 MHz 3.59 MHz 4.5 MHz 4.5 MHz Noise figure of an RF Noise figure of an RF amplifier with 0 dB Noise amplifier with 10.0 dB 48 Figure Noise Figure
  • RF Amplifiers Distortions.Below is an example on how Carrier to Noise affect an RF amplifier.10 dBmV 57.2 dB C/N 15 dBmV 62.2 dB C/N to status to monitoring -20 dB status monitoring -20 dB JXP RF/ RF AC AC JXP RF/ RF AC AC -20 dB Possibility of RF Splitter or -20 dB RF/ EQ JXP BODE BRD JXP Possibility of AC RF 7, 10, 12 dB AC coupler RF/ EQ JXP BODE BRD JXP RF Splitter or AC RF 7, 10, 12 dB AC coupler ADU JXP -20 dB Manual JXP -20 dB RF/ ADU JXP Gain RF AC AC Manual JXP Control RF/ 5 40 -20 dB Gain RF MHz MHz Possibility AC AC of a 3th Control 5 40 -20 dB ICS JXP RF output MHz MHz Possibility of a 3th from RF output 5 40 ICS JXP MHz MHz statu s 5 40 from monitoring -20 dB MHz MHz statu s -16 dB monitoring ICS -20 dB se fuse fu EQ JXP JXP Drive -16 dB ICS se fuse fu EQ JXP JXP Drive 24 Vdc to status vcc Power Supply 24 Vdc monitoring to -20 dB status vcc Power fuse 90 / 60 monitoring Supply Vac -20 dB fuse fuse ICS JXP 90 / 60 Vac fuse ICS JXP Carrier to Noise Carrier to Noise Noise Figure 11.0 dB Noise Figure 11.0 dB 59.2-12.0 +10 = 57.2 dB C/N 59.2-12.0 +15 = 62.2 dB C/N 1 dB is added to the fig. To Noise for the EQ. 49
  • RF Amplifiers Distortions.Below is an example on how Carrier to Noise affect a cascade of RF amplifier.15 dBmV 62.2 dB C/N 15 dBmV 59.19 dB C/N FIRST Amp. SECOND Amp. to to status status monitoring -20 dB monitoring -20 dB JXP RF/ JXP RF RF/ AC RF AC AC AC -20 dB -20 dB Possibility of Possibility of EQ JXP BODE BRD JXP RF Splitter or RF Splitter or RF/ 7, 10, 12 dB RF/ EQ JXP BODE BRD JXP AC RF AC RF 7, 10, 12 dB AC coupler AC coupler ADU JXP -20 dB -20 dB ADU JXP Manual JXP Manual JXP RF/ Gain RF Gain RF RF/ AC AC AC AC Control Control 5 40 -20 dB 5 40 -20 dB MHz MHz Possibility MHz MHz Possibility of a 3th of a 3th ICS JXP RF output ICS JXP RF output 5 40 from 5 40 from MHz MHz statu s MHz MHz statu s monitoring monitoring -20 dB -20 dB -16 dB -16 dB ICS se ICS se fuse fu fuse fu EQ JXP JXP Drive EQ JXP JXP Drive 24 Vdc 24 Vdc to to status vcc Power Power status vcc monitoring Supply Supply -20 dB monitoring -20 dB fuse fuse 90 / 60 90 / 60 Vac fuse Vac ICS JXP fuse ICS JXP Carrier to Noise Carrier to Noise Noise Figure 11.0 dB Noise Figure 11.0 dB 59.2-12.0 +15 = 62.2 dB C/N 59.2- 59.2-12.0 +15 = 62.2 dB C/N 59.2- Formula for a cascade of amplifier for: Carrier to Noise. C/N of FIRST Amp. – 10Log 10 of 2 = 3.01 dB 50
  • RF Amplifiers Distortions.Hum is a amplitude modulation, where the 50 or 60 Hz frequency of thepower company is harmonized with the 59.94 Hz of the televisionhorizontal sweep.Hum can be generated by faulty AC-DC power supply or by defectivepassive equipment in the system.•One or two bars appears usually going up the TV screen, at the sametime as the picture is showed on the television set.•The easiest way to measure hum is using a CW carrier and a spectrumanalyzer.•In Canada we expect broadband system to have a HUM ratio better than2.0% or 34 dB to CW carrier. 51
  • RF Amplifiers Distortions.Below are the maximum distortion expected at all customersfor a good quality picture in a modern Broadband System. •Second Order. -51.0 dB •Third Order. -51.0 dB •Cross Modulation. -48.0 dB •Third Order Composite. -51.0 dB •Second Order Composite. -51.0 dB •Carrier to Noise. +48.0 dB •Hum Modulation. 34.0 dB or 2% 52
  • How to Adjust an RF Amplifier.1. Make sure the amplifier is installed properly.2. Make sure that the AC power route is properly mapped and is in the proper range. the3. Check the RF level at the input of the amplifier, it should meet what is put on the plan.4. Install the proper equalizer at the input of the amplifier.5. If required, install an RF pad at the input of the amplifier.6. Get the amplifier to work at his maximum output by adjusting the amplifier’s gain control at his minimum, this output should give about 4.0 dB above the operation level requires. operation7. If the above function give you more that 4.0 dB, you should install a proper pad, to bring install this level at 4.0 dB above operating level.8. Adjust the amplifier at his proper operating level by adjusting the variable gain.9. Once operating his proper operating level, check if the slope is in his right range. This range should be 10.0 dB for 750 MHz system, and 11.5 dB for 870 MHz system.10. If above operation is not in his normal range, verify or change the input equalizer.11. If the amplifier overall response is not acceptable, adjust his response by adjusting the overall mop-up control. mop-12. Function 11 should only be done with proper sweep equipment. 53
  • How to Adjust an RF Amplifier. 870 MHz 50 870 MHz 50 MHz MHz to status monitoring -20 dB 870 50 MHz MHz 40 JXP RF/ 870 MHz 5 RF MHz MHz AC AC 50 -20 dB MHz Possibility of 5 40 RF Splitter or MHz MHz RF/ EQ JXP BODE BRD JXP AC RF 7, 10, 12 dB AC couplerRF Input Manual ADU JXP JXP -20 dB RF/ Gain RF AC AC Input Equalizer 5 40 MHz MHz Control -20 dB Possibility of a 3th ICS JXP RF output 5 40 from -20 dB MHz MHz status monitoring RF Output -16 dB fuse ICS fuse EQ JXP JXP Drive Input Pad 24 Vdc to status vcc Power monitoring Supply -20 dB fuse 90 / 60 Vac fuse ICS JXP Variable Gain Mid Stage Output Response Attenuator Corrector Attenuator 54
  • Test! 55
  • •Does CTB and CSO add at the same speed in a HFC system?___________________________________________________________•What linear distortions works at 20 log10, in a HFC system?_____________________________________________________•What is the operating level difference between Push pull and Power Doubling?____________________________________________________________•Name a new type amplification circuitry used in modern RF amplifier?_____________________________________________________________•What is the minimum requirement at a customer for Carrier to Noise Level?______________________________________________________________•What is the level of CTB and CSO required at a customer?_______________________________________________________________•What does HUM do to a television signal?_______________________________________________________________•What is the proper RF level at a multitap?_______________________________________________________________ 56
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