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Diode Filter Mixer

IP.com Disclosure Number: IPCOM000073426D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Crouse, WG: AUTHOR

Abstract

This circuit is used to shape, filter and mix signals for a four-phase modulator, a function similar to that performed in data sets but using simpler circuits requiring no conventional filters. The circuit receives two sets of data signals each in the form of a sawtooth wave with either of two complementary phases. The signals are converted in diode filters to approximate sine waves and a third sawtooth wave of lower frequency is used to alternately gate the signals to an output terminal.

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Diode Filter Mixer

This circuit is used to shape, filter and mix signals for a four-phase modulator, a function similar to that performed in data sets but using simpler circuits requiring no conventional filters. The circuit receives two sets of data signals each in the form of a sawtooth wave with either of two complementary phases. The signals are converted in diode filters to approximate sine waves and a third sawtooth wave of lower frequency is used to alternately gate the signals to an output terminal.

In the drawing, a data signal 1 which is a sawtoothed wave having data representing sections of one of four phases is applied to terminal 2 and passes through a resistor 3 to the anode of a diode 4.

The cathode of diode 4 is connected to a negative voltage through a resistor 5. A second diode 6 has its anode grounded and its cathode connected to the negative supply through resistor 7. The cathodes of diodes 4 and 6 are connected by a capacitor 8 and together provide a balanced circuit for sine wave generation.

The anode voltage of diode 4 is amplified by a transistor 9 connected through a resistor 10 to a positive source and having a diode 11 with its anode connected to ground and its cathode connected to the emitter of diode 9, through a capacitor 12. Resistors 3, 5, and 7 and the voltage current characteristics of diodes 4, 6, 11 and transistor 9 are selected so that the collector current of transistor 9 approximates a sine wave for a sawtooth input at terminal 2.

A duplicate arrangement comprising an input terminal 13, resistor 14, transistor 15, diodes 16, 17 and 18, capacitors 19 and 20 and resistors 21 and 22 is provided for the second data signal 23.

Collectors of transistors 9 and 15 are connected together to form output termina...