Richard Hirschmann Radiotechnisches Werk

Theodor T Bossert

A frequency-modulated ultrashort-wave signal is received, but due to wave-reflection phenomena from physical bodies reflecting towards the receiving antenna is amplitude modulated, this amplitude modulation being dependent upon frequency. Derived from the frequency-modulated signal is a frequency-deviation signal indicating its instantaneous frequency deviation, and also an amplitude-indicating signal indicating its instantaneous amplitude. These can be fed to the x- and y-inputs of an oscilloscope for display of an amplitude versus frequency curve used to generate a quantitative characterization of reception quality, the oscilloscope screen being provided with a horizontal reference axis. In order that the horizontal reference axis implied by such curve stay in register with that on the screen, even during rotation of the receiving antenna, the amplitude-indicating signal is normalized with respect to the reflection-free amplitude value which the frequency-modulated signal would have in the absence of these wave-reflection phenomena. This is accomplished by applying the amplitude-indicating signal to a clocked amplitude regulator, which is clocked only when the frequency-deviation signal indicates substantially zero frequency deviation of the received frequency-modulated signal.

Normalization method and apparatus used when quantitatively measuring

A frequency-modulated ultrashort-wave signal is received, but due to wave-reflection phenomena from physical bodies reflecting towards the receiving antenna is amplitude modulated, this amplitude modulation being dependent upon frequency. An amplitude-indicating signal and a frequency-deviation signal are derived from the received frequency-modulated signal and, instead of merely being applied to the x- and y-deflection inputs of an oscilloscope for partly subjective analysis by a skilled analyst, are applied, preferably via low-pass filters, to first and second differentiators, the two output signals of which are transmitted to a divider which produces a differential-quotient signal indicating the rate of change of the amplitude of the frequency-modulated signal with respect to the frequency deviation of the frequency-modulated signal. The differential-quotient signal is applied to an extreme-value-responsive indicator, whose read-out constitutes a direct quantitative measure of reception quality which can be used, for example, to automatically steer the receiving antenna.

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Munich, Germany

Theodor T Bossert