Telecommunications – Transmitter and receiver at separate stations – Frequency or phase modulation
Patent
1981-03-02
1982-12-21
Ng, Jin F.
Telecommunications
Transmitter and receiver at separate stations
Frequency or phase modulation
455 67, H04B 100, H04B 1700
Patent
active
043653464
ABSTRACT:
The baseband input to a frequency modulation radio transmitter is switchably connectable to a square wave generator, the amplitude of the square wave output being adjusted to provide a predetermined deviation of the FM radio transmitter. The output frequency of a pilot oscillator is also applied to the baseband input and is subjected to amplitude modulation because of non-linearities which exist in the system and which adversely affect the signal during transmission through the system.
At the receiving end of the radio system, the receiver output contains a signal comprising the pilot frequency and a superimposed amplitude modulated signal, and this signal is applied to a product detector. The output of the product detector is a pulsating DC signal comprising a basic DC component, which is representative of the amplitude of the pilot frequency, and an AC component, which is representative of the system non-linearity. The pulsating DC signal is applied to one terminal of a capacitor. The AC component appears at the other terminal and is rectified and integrated to obtain a DC signal, the amplitude of which is proportional to the slope component in the system non-linearity. This DC signal is measured by a direct current meter.
REFERENCES:
patent: 3195047 (1965-07-01), Ruthroff
patent: 3271679 (1966-09-01), Fostoff
patent: 3492579 (1970-01-01), Carassa
patent: 3492583 (1970-01-01), Sinelli
Froese Abram
Liebelt Alvin
Onotera Larry Y.
AEL Microtel Ltd.
Cool Leonard R.
Ng Jin F.
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