GB1262370A - Improvements in or relating to radio frequency transmitters - Google Patents

Improvements in or relating to radio frequency transmitters

Info

Publication number
GB1262370A
GB1262370A GB4737869A GB4737869A GB1262370A GB 1262370 A GB1262370 A GB 1262370A GB 4737869 A GB4737869 A GB 4737869A GB 4737869 A GB4737869 A GB 4737869A GB 1262370 A GB1262370 A GB 1262370A
Authority
GB
United Kingdom
Prior art keywords
amplifier
transistor
output
unit
transistors
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB4737869A
Inventor
Bernard David Bradshaw
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems Electronics Ltd
Original Assignee
Marconi Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Marconi Co Ltd filed Critical Marconi Co Ltd
Priority to GB4737869A priority Critical patent/GB1262370A/en
Publication of GB1262370A publication Critical patent/GB1262370A/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers
    • H03G3/3042—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
    • H02H3/093—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current with timing means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/52—Circuit arrangements for protecting such amplifiers

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)

Abstract

1,262,370. Transistor Class B amplifiers; transmitting systems. MARCONI CO. Ltd. 6 July, 1970 [25 Sept., 1969], No. 47378/69. Headings H3T and H4L. [Also in Division H2] A solid state radio frequency transmitter including a Class B transistor power amplifier 1 has a control means A, B operable automatically if the D.C. supply current taken by the amplifier reaches for a predetermined time a predetermined value less than the maximum available D.C. supply current from the power source D for rendering effective circuit protection means 7 for the amplifier. Normally, transistors A4, A12 and 7 are off and transistor A5 is on. The current drawn by the Class B amplifier 1 produces a voltage drop across resistor 6 which is compared with a voltage set by potentiometer A1, A2 by differential amplifier A4, A5. If the output load current drawn by the amplifier 1 exceeds a predetermined amount for a predetermined relatively long time, e.g. a few seconds, as determined by the time constant of A3, A6 and A8, transistors A4, A12, and 7 turn on and transistor A5 turns off so that transistor 7 shunts the r.f. input 3 to the amplifier. Control unit B is similar to unit A and protects against peak output overload. The potentiometer A1, A2 in unit B is adjusted so that the transistors A4, A12 and 7 require a larger current through resistor 6 to switch them on and the time constant of A3, A6 and A8 in unit B has a shorter time constant. Control unit C prevents secondary breakdown of the transistors in the power amplifier 1. The unit C is similar to units A and B but requires a larger current through resistor 6, than that for a peak overload, so as to obtain an output at C13 and the time constant is made very short. This output from C13 turns on SCR 8 so as to shunt the positive supply D2 from D, which may be provided with a current overload protection. A reflection sensor 5 is provided between the output of the Class B amplifier 1 and the transmitter aerial so that impedance mismatch, such as disconnection of the aerial or load, causing a reflected power exceeding say 10% operates the transistor 7 via connection 513 so as to shunt the input. In a modification each of the units A and B may feed its output control signal to a monostable or bi-stable which apply protection, e.g. by rendering transistor 7 conductive and/or cutting off the D.C. supplied to the amplifier 1.
GB4737869A 1969-09-25 1969-09-25 Improvements in or relating to radio frequency transmitters Expired GB1262370A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB4737869A GB1262370A (en) 1969-09-25 1969-09-25 Improvements in or relating to radio frequency transmitters

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4737869A GB1262370A (en) 1969-09-25 1969-09-25 Improvements in or relating to radio frequency transmitters

Publications (1)

Publication Number Publication Date
GB1262370A true GB1262370A (en) 1972-02-02

Family

ID=10444754

Family Applications (1)

Application Number Title Priority Date Filing Date
GB4737869A Expired GB1262370A (en) 1969-09-25 1969-09-25 Improvements in or relating to radio frequency transmitters

Country Status (1)

Country Link
GB (1) GB1262370A (en)

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