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SENDER A.M. Transmitters

SENDER. SENDER S.A. SENDER A.M. Transmitters. SENDER. SENDER S.A. Company was created in 1997 by a group of engineers and technitians with long experience in Solid state A.M. Transmitters. Located in Santiago Chile, with 25 employes. 40% of them are shareholders.

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SENDER A.M. Transmitters

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  1. SENDER SENDER S.A. SENDER A.M. Transmitters

  2. SENDER SENDER S.A. • Company was created in 1997 by a group of engineers and • technitians with long experience in Solid state A.M. • Transmitters. • Located in Santiago Chile, with 25 employes. • 40% of them are shareholders. • Main activity: Design and manufacturing of A.M. transmitters, • antenna tuning units, duplexers and triplexers. • First transmitter in operation Nov 1997. • Transmitters sold up to now:127 from 1 KW to 12.5 KW.

  3. SENDER Product Line AM 1500 SS 1.5 KW/1.1 KW, single phase / 2 power amplifiers AM 3000 SS 2.25 KW/3KW, single phase or 3 phase / 4 power amplifiers. AM 7500 SS 5.5 KW/ 7.5 KW, 3 phase or single phase / 7 power amplifiers. AM 15000 SS 11 KW/13 KW,3 phase / 14 power amplifiers AM 25000 SS 22 KW/26KW, 3 phase / 28 power amplifiers A.T.Us for 1.5 KW, 3 KW,7.5 KW, 13 KW and 26 KW

  4. SENDER Product highlights • Solid State. Modular / redundant • architecture • High efficiency. PWM & class D R.F. • amplifiers • Hot plug in power amplifiers with Mosfets. • Simple design with standard components. • Totally rustproof cabinet made of iridated • aluminum with stainless steel hardware. • Excellent specs and audio quality. • Outstanding factory support. • Very competitive price.

  5. SENDER Basic specifications Frequency range: .53 MHZ to 1.7 MHZ. Input voltage: 110V or 220 V single phase, 220V or 380V 3 ph +or - 10%. Line frequency 47HZ to 63 HZ. Efficiency: 75% or better for single phase transmitters, 80% or better for 3 phase transmitters. Frequency response: Better than +or- 1 dB 30 Hz to 10 KHZ. Distortion: Less than 1% at nominal power and 90% modulation. Harmonics and spurious:- 73 dB or better for AM 1500 SS, - 80 dB or better for other models.

  6. SENDER Frequency stability:+- 5 Hz. Output impedance: 50 Ohm Dimentions and weigths: AM 1500 SS W=44 cm,H=62.5cm D=60 cM , 100 Kg. AM 3000 SS W=44 cm,H=65.5cm D=60 cM , 160 Kg. AM 15000 SS W=80 cm,H=181cm D=81 cM , 500 Kg.

  7. SENDER Standard features: 2 power level with independient adjustment and modulation autotracking. Start, stop,power level selection and power level adjustment remotely controled. Automatic alarm reset. Positive and negative limiter.

  8. SENDER Basic block diagram Combiner A1 Synth Output A2 Filter Out PWM An PWR Control Supply

  9. SENDER Relationship with RICHARDSON ELECTRONICS • Exclusive representation for Asia and other specific countries. • Joint project to manufacture transmitters in U.S.A. • Sender sells Omnicast F.M. Transmitters in Latin America. • Excellent level of personal contacts .

  10. SENDER Near future projects • FCC type acceptance. • Frequency agile 1.5 KW transmitter. • IBOC compatibility. • Inboard audio processor and modulation monitor. • Higher power amplifiers

  11. SENDER Reliability in A.M. stations

  12. SENDER Introduction • Harmonic set of: • Transmitter • Radiating system • Energy System • Auxiliary Equipment Station Concept

  13. SENDER Experience with stations using Solid State A.M. Transmitters • Very high reliability if precautions related with the following topics are considered: Antenna discharges A.C. Source transients and discharges A.C. Source voltage limits Load stability Interference from nearby stations Reliability is reduced in unprotected stations

  14. SENDER STL RX ATU TX Basic elements of a station ANTENNA Audio & Rem. Ctrl. RF H.V TRANSF. DISTR. BOARD T.P. A.C. GROUND PLANE

  15. SENDER TRANSMITTER BASIC BLOCKS • POWER SUPPLY • PWM MODULATOR • R.F. DRIVER • CLASS D or E • R.F. OUTPUT FILTER • CONTROL,PROTECTIONS,SIGNALING • EXTERNAL INTERFACE

  16. SENDER PWM MODULATOR • GENERATES D.C + A.C. VOLTAGE FOR THE R.F. AMP. • SWITCHING DEVICE, HIGH EFFICIENCY • A FILTER IS NEEDED TO ELIMINATE SWITCHING FREQUENCIES • CONMUTATION FREQUENCY IS 72 KHZ.

  17. SENDER PWM (PULSE WIDTH MODULATION) SIMPLIFIED DIAGRAM: R.F. AMPLIFIER D.C. SUPPLY Switch (Mosfet) PWM FILTER LOAD

  18. SENDER PWM waveform Filtered output voltage 1) 2) S 3) V RL 4) PWM BASIC OPERATION • Between 1) y 4) duty cycle is increased • Mean voltage in the load increases proportionally • A filter is required to remove high frequency components F = 72 kHz

  19. SENDER PWM Frequency spectrum Amplitude D.C Component PWM 0° Audio Frecuency 72 kHz 144 kHz

  20. SENDER PWM Frequency spectrum Amplitude D.C. component PWM 180° Audio 72 KHZ components out of phase Frecuency 144 kHz 72 kHz

  21. SENDER PWM filter diagram

  22. SENDER PWM filter frequency response

  23. SENDER PWM filter response sensibility to load changes Rload +/- 15%

  24. SENDER Load change consequences • With reduced load (Rload< Rnominal) transmitter will produce high frequency submodulation • With increased load (Rload>Rnominal) transmitter will show high frequency overmodulation • Distorsion will increase if filter is not propperly loaded.

  25. SENDER Modulated class D R.F. Amplifier. +V T1 T3 RL T2 T4 PWM filter

  26. SENDER Class D r.f. Amplifier diagram

  27. SENDER Cgd Cgd Cgd Cgd Cds Cds Cds Cds Cgs Cgs Cgs Cgs Class D Bridge parasitic elements V+ RL Ciss = Cgs + Cgd Crss = Cgd Coss = Cds + Cgd

  28. SENDER Mosfets drive Vgs Dead time V+ T1 T3 Vgs(thr) RL time T2 T4 Vgs peak = 13V

  29. SENDER R.F. drive circuit • Ls and Cs series resonant • Lp paralel resonant with mosfet input capacitance (Partially) Ls Cs MOSFET drive Drive signal Lp SCgs

  30. SENDER V+ T1 T3 RL T2 T4 Class D bridge current paths V+ T1 T3 RL T2 T4

  31. SENDER Class D bridge undisered current paths. V+ V+ T1 T3 T1 T3 RL RL T2 T4 T2 T4

  32. SENDER Class D Amplifier basics. • Low impedance driver required for: • Fast switching • Low Vgs modulation by Crss • Tuned load to produce sinusoidal current • High efficiency (>95 %) • Duty cycle should be < 0.5 • Avoid transversal currents • Coss charge and discharge through Rl

  33. SENDER Class D R.F. Amp typical waveforms.

  34. SENDER MOSFET characteristics • No secondary breakdown • positive temperature coeff. Of Rdson (Simplify parallel operation) • Voltage controled device (Vgs) • Driver impedance dependent switching times. • Intrinsic antiparallel diode

  35. SENDER IRFP350 MOSFET • Rdson = 0.3 ohms • Vdss = 400 Vdc • Vgs = +/- 20 Vmax Vth = 3 V Vsat = 9 V • Id = 16 A @ Tc=25ºC 10 A @ Tc=100ºC • Idmax = 64 A • Capacitance @ f=1MHz, Vds=25V , Vgs=0V • Ciss = 2600 pF (2400 pF for Vds>40V) • Coss = 660 pF (200 pF for Vds>40V) • Crss = 250 pF (50 pF for Vds>40V)

  36. SENDER Class D amplifier example SENDER

  37. Cicuit data Vdc = 110 V F = 1600 kHz d = 0.43 Transistor IRFP350 Rdson = 0.3 ohms Ton = 16 ns Toff = 40 ns Coss = 200 pF L2 = 7.04 uH C2 = 1.55 nF Operational data RL = 15 ohms Po = 132.36 W h = 97.93 % Transistor stresses Vmax = 110.81 V Imax = 4.12 A Pdis = 0.70 W x2 (1.4 Wtotal) SENDER Class D Simulation(1/2 bridge,Vmax<400x.75/2.5) *Simulated with HB plusfrom Design Automation

  38. SENDER Class E Amplifier diagram

  39. SENDER Class E amplifier example

  40. SENDER Class E amplifier basics. • R.F.Choke large enough to produce constant current • High Q series resonant circuit to produce sinusoidal current • Vds y dVds/dt =0 prior to starting conduction • High efficiency (>95%) • if special high voltage transistors with low Rdson are used

  41. SENDER Clase E Waveforms

  42. Circuit Data Vdc = 33 V F = 1600 kHz d = 0.48 Transistor IRFP350 Rdson = 0.3 ohms Ton = 16 ns Toff = 40 ns Coss = 200 pF L1=12.3uH L2=3.7uH C1= 4.1nF C2=4.9nF Operational Data RL = 7.3 ohms Po = 125.27 W h = 90.53 % Transistor stresses Vmax = 118.79 V Imax = 9.84 A Pdis = 6.55 W x2 (13.1 Wtotal) SENDER Clase E Simulation(Vmax<400x.75/2.5) *Simulated with HEPA Plus from Design Automation

  43. SENDER Passband Output filter • Reduce R.F. Harmonics • High third harmonic att > 80 dB • Medium second harmonic att. > 40 dB • Higher harmonics att > 70 dB • Permits impedance matching between amplifier and load. • Atenuates low frequency components (Lightning protection)

  44. SENDER Output filter • Design oriented to protect R.F.amplifier • Low frequency attenuation • Inductor input • Strategically located sensors: • Spark Gap °Transient suppressor • SWR °Overpower • Overcurrent °Phase • Input transient suppressor(Active or pasive)

  45. SENDER Output filter diagram

  46. SENDER Output filter frequency response

  47. SENDER Real and imaginary part of filter input impedance

  48. SENDER Protections integrated in the output filter SENDER SENDER

  49. SENDER Posible Transmitter Agresions • Antenna • Impedance change and discharges • A.C. Supply • Voltage variation and transients • Program signal • Level variations and transients • Ground • Transfered potentials and high ground currents

  50. SENDER Antenna related problems • Impedance change • Low heigth antennas are particularly unstable • Restricted bandwidth • Interference from other stations • Discharges

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