Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Patent
1980-01-10
1982-06-15
Blum, Theodore M.
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
330 2, G01S 502
Patent
active
043353843
ABSTRACT:
A logarithmic amplifier calibrator having a signal generator providing an exponentially decaying calibration signal and a pulse generator providing a sample pulse each time the calibration signal has decayed by a predetermined decibel (db) increment. More specifically, the calibrator includes a crystal which is excited to an energy level through a feedback loop having an amplification means whose gain is controlled by a voltage controlled attenuator. The decay characteristics of the crystal when installed in the calibrator are determined so that the time required for the crystal to decay over an entire calibration range is known. This time is then divided into a plurality of time increments, each time increment corresponding to a predetermined db drop in the calibration signal. Sample pulses derived from a high frequency, high stability oscillator in the calibrator are developed to correspond to each of the predetermined time increments. The calibration signal is amplified by a logarithmic amplifier to be calibrated, and its output values at the time of each sample pulse provides a plurality of calibration points which can be utilized by a computer to compensate for non-theoretical operation of the logarithmic amplifier. In another application of the invention, the calibrator is utilized in conjunction with an amplitude comparison direction finding receiving system having two receiving channels each of which contains a logarithmic amplifier. During a calibration sequence, the exponentially decaying calibration signal is provided simultaneously to both of the logarithmic amplifiers, and the sample pulses are used to simultaneously clock analog-to-digital converters associated with each of the logarithmic amplifiers. Thus, a means is provided whereby both of the logarithmic amplifiers are calibrated with respect to each other, therefore providing a means for compensating for amplifier mismatch, one of the largest contributors to amplitude error budgets in this type of direction finding system.
REFERENCES:
patent: 3735410 (1973-05-01), Poppe et al.
Arbuckle Frederick M.
Blum Theodore M.
Bunker Ramo Corporation
Freilich Arthur
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