INVESTIGATION OF CONSTANT DELAY NARROW BAND IF AMPLIFIERS.
Final rept. for Jun 63-May 65,
MONTANA STATE UNIV BOZEMAN ELECTRONICS RESEARCH LAB
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The program covers the design, construction and testing of two bread-board narrowband IF amplifiers centered at 455 kc having a constant time delay characteristic over the 3 db passband. The first amplifier uses a passive filter and equalizer ahead of the amplifier section. The amplifier uses dual conversion to lower the IF frequency, and thus decreases the sensitivity of the time delay characteristic to changes in component value. Though the individual sections of this amplifier were tuned to a fair degree of precision, the overall response was unstable. Several limitations of this design, discussed in the text, were overcome by taking the second approach. The second approach uses a staggered tuned amplifier employing cascaded sections having a third order equal ripple time delay response. A computer program was generated to compute all necessary filter parameters. This approach lowered the required Q sufficiently so that air core coils could be used instead of ferrite core coils. Also included are various methods of measuring time delay for narrowband amplifiers. A study is made of the sensitivity to critical components for several designs including the familiar maximally flat time delay response. A study is also made of the time delay distortion caused by the lowpass to bandpass transform. Author