Improvement of the preliminary frequency divider. Scheme, description

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Improvement of the preliminary frequency divider. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Measuring technology

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Reference [1] describes a broadband frequency prescaler. With a total division factor of 100, the maximum frequency at its output is 15 MHz, and with K193IE7 counters operating at frequencies up to 2000 MHz, it is even higher. Amateur frequency meters are usually made on TTL microcircuits with an upper frequency measurement limit of up to 10 ... 15 MHz; with CMOS chips - up to 2 MHz.

I have finalized the divider using less scarce microcircuits. Now it can be used to measure frequencies above 1 GHz with a low-frequency frequency counter. Schematic diagram of the modified part of the device is shown in the figure.

(click to enlarge)

The preamplifier and divider by 4 on the K193IE5A counter (DD1 in this circuit) are kept unchanged. The divider with a division factor of 25 is replaced by a divider with a division factor of 250. It is assembled on a K193IE2 (DD2) counter with a division factor of 10 and several K555TM2 D-flip-flops. Triggers DD3, DD4.1 and DD4.2, DD5 form two dividers with division ratios of 5. On the transistor VT6 and diodes VD6 - VD8, an ESL level converter is assembled to the TTL level. Such a replacement of microcircuits made it possible to eliminate the supply voltages of -5,2 V and -2 V (microcircuits of the K193 series also work at a voltage of 5 V).

Thus, the overall division factor has become equal to 1000. Now the signal from the output of the pre-divider can be fed directly to the input of a frequency counter, made even on CMOS chips. The current consumed by the device has decreased, and it became possible to place the preamplifier described in [2] on the same board with the divider. If necessary, the amplifier can be turned off using an additional switch.

As already mentioned, when using the K193IE5 counter instead of K193IE7A, the upper frequency limit will increase to 2000 ... 2200 MHz. Therefore, for reliable operation of the divider, it is necessary to use KR3TM4 or other TTLSH triggers with a maximum operating frequency of at least 531 MHz as triggers DD2, DD55, turning them on accordingly. Setting up a prescaler is described in [1].

Literature

Beetle V. Preliminary frequency divider for the range of 50 ... 1500 MHz. - Radio, 1992, No. 10, p. 46, 47.
Zhuk V. Preliminary frequency divider for the range of 50 ... 1500 MHz (Our consultation). - Radio, 1993, No. 6, p. 45.

Author: A.Slinchenkov, Ozersk, Chelyabinsk region

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