1978-05-03
1980-01-29
Griffin, Robert L.
325182, H04B 104
Patent
active
041863461
ABSTRACT:
The transmitter has a carrier control and includes an exciter for supplying the carrier voltage to a modulation stage, usually the final RF-power amplifier of a broadcast transmitter, with the modulation voltage having a controlled dc content. The modulation voltage is amplified in a modulation amplifier and the amplified modulation voltage is supplied to the modulation stage. The modulation amplifier includes a switching amplifier producing pulse duration modulated pulses, a modulation voltage controlled pulse duration modulator preceding the switching amplifier and a filter section following the switching amplifier. An adder element is connected in advance of the modulation amplifier, specifically in advance of the modulation voltage-controlled pulse duration modulator. The applied modulation voltage is supplied to a rectifier followed by a filter section and the filter section is connected to a control element and supplies thereto a variable direct voltage as a volume-dependent control magnitude which contains also very low frequency components in accordance with the volume of the modulation voltage. The output of the control element is supplied to the adder element for combining with the modulation voltages supplied to the modulation amplifier to change the pulse duty factor of the output pulses of the switching amplifier as required for carrier control of the transmitter. The volume control magnitude supplied from the control element can be additionally superposed by a fixed direct voltage to establish the average pulse length of the output pulses of the pulse duration modulator and thus to establish the average direct voltage value of the filter section of the modulation amplifier and the average operating point of the modulation stage.
REFERENCES:
patent: 3413570 (1968-11-01), Bruene et al.
patent: 3477042 (1969-11-01), Wachs
patent: 3943446 (1976-03-01), Quidort
patent: 4122415 (1978-10-01), Luther, Jr. et al.
Griffin Robert L.
LICENTIA Patent-Verwaltungs-G.m.b.H.
Ng Jin F.
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