Pulse-compression frequency-discriminator

1,104,545. Frequency measurement. MULLARD Ltd. July 7, 1965 [April 7, 1964], No. 14390/64. Heading G1U. [Also in Division H3] A frequency-measuring apparatus, Fig. 3, comprises a pre-amplifier 10 connected to the input terminal 1, the output of the amplifier being applied to a mixer 11. Also applied to the mixer is the signal from an L. O. 13 having a linear sawtooth frequency/time characteristic. The output of the mixer 11 at an intermediate frequency selected by a band-pass filter 12 is supplied to a frequency discriminator 17 (see Division H3). The output of a discriminator 14 which improves the linearity of the L. O. 13 is also applied to a sawtooth generator 15 supplying the X plates of a calibrated C. R. T. 16 to provide a time base, the Y plates of the C. R. T. being supplied from the output of discriminator 17. The C.R.T. give a display similar to a pulse-compression response graph with a maximum corresponding to the frequency of the input signal. In a modification Fig. 4 (not shown) an additional filter 18 and amplifier 19 are provided and an A-scan display 16 is supplied via a wide-band video-amplifier 21. In another modification Fig. 5 (not shown) a doubleprobe system using reversed-polarity diodes replaces the single diode system of Fig. 2. In another arrangement Fig. (not shown) having an operating band from 8 to 12 Gc/Sec. and a sweep rate of 100 Kc/Sec. there are twenty probes and a backward wave oscillator 22 is swept over the frequency range by a waveform generator 23.