Delay circuit

A delay circuit having the characteristics that the delay time is proportional to the frequency comprising:

• (a) a first analog-digital converter connected to an input terminal of the delay circuit for receiving analog signal to be transmitted by the delay circuit,
• (b) a first transversal filter connected to the output of said first analog-digital converter, said transversal filter having a plurality of delay elements connected in series with one another, the delay time (T) of each delay element being the same as the sampling interval of said first analog-digital converter, a plurality of potentiometers each having one end thereof connected to the junction points between said delay elements and the output of the last delay element, and an adder connected to the tap output of each of said potentiometers, wherein said tap outputs provide a tap weight to the output of each of said delay elements and wherein said adder sums the outputs of said potentiometers to provide an output of the transversal filter,
• (c) a first digital-analog convertor connected to the output of said transversal filter so as to provide an analog output signal to be transmitted,
• (d) a second analog-digital convertor connected to an input terminal of the delay circuit for receiving said transmitted analog signal,
• (e) a second transversal filter connected to the output of said second analog-digital converter, said transversal filter having a plurality of delay elements connected in series with one another, the delay time (T) of each delay element being the same as the sampling interval of said second analog-digital converter, a plurality of potentiometers each having one end thereof connected to the junction points between said delay elements and the output of the last delay element, and an adder connected to the tap output of each of said potentiometers, wherein said tap outputs provide a tap weight to the output of each of said delay elements and wherein said adder sums the outputs of said potentiometers to provide an output of the transversal filter,
• (f) a second digital-analog converter connected to the ouput of said second transversal filter so as to provide an analog output signal of the received signal,
• (g) a digital memory storing the precalculated value for each of the desired delay characteristics and providing the tap weights of said potentiometers of said first transversal fitler, (h) means for providing the content of said digital memory selectively to the potentiometers of said first transversal filter according to the desired delay characteristics, and
• (i) means for providing the inversed value of the content of said digital memory selectively to the potentiometers of said second transversal filter according to the desired delay characteristics.