IMPEDANCE SIMULATING CIRCUIT FOR TRANSMISSION LINES

• US 3,828,281 A
• Filed: 02/26/1973
• Issued: 08/06/1974
• Est. Priority Date: 02/26/1973
• Status: Expired due to Term

• Current Assignee: Charles W. Chambers Jr
• Original Assignee: Charles W. Chambers Jr
• Inventors: Chambers, Charles W. Jr.
• Primary Examiner(s): Gensler, Paul L.
• Application Number:
  US05/335,488
• Time in Patent Office: 526 Days
• Field of Search: 333/17,17M,8R,8T 323/45 179/17G,170.2,175.31E
• US Class Current: 333/17.1
• CPC Class Codes: H03H 11/30 Automatic matching of source impedance to load impedance
• CPC Class Codes: H03H 11/405 Positive impedance converters H03H11/42 takes precedence; used in frequency selective networks H03H11/0416
• CPC Class Codes: H03H 11/44 Negative impedance converters H03H11/42 takes precedence; used in frequency selective networks H03H11/10
• CPC Class Codes: H03H 11/48 simulating reactances

Abstract

A circuit for simulating the presence of positive or negative impedances in shunt or in series with a transmission line. A voltage generating circuit generates an impedance simulating voltage and introduces that voltage in series with the transmission line. A current generating circuit generates an impedance simulating current and introduces that current in shunt with the transmission line. Current feedback circuitry controls the voltage generating circuitry in accordance with the amplitude of the signal current in the transmission line to simulate either a positive or negative series impedance. Voltage feedback circuitry controls the current generating circuitry in accordance with the signal voltage across the transmission line to simulate either a positive or negative shunt impedance. Circuitry is also provided to afford these simulated impedances in the presence of echo suppressing and impedance matching characteristics.

Claims

1. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, voltage generating means for generating an impedance simulating voltage, said voltage generating means having simulating input means and output means, series connecting means for applying the voltage at the output means of said voltage generating means in series with the transmission line, current sensing means for establishing a signal which varies substantially only in accordance with a signal current through the transmission line, means for electrically connecting said current sensing means to the transmission line, current feedback means for controlling the magnitude and character of the simulated impedance to be introduced in series with the transmission line and means for connecting said current feedback means to said current sensing means and to the simulating input means of said voltage generating means, the phase relationships between said generating means, said connecting means, said sensing means and said feedback means being selected to afford a positive simulated impedance.

2. An apparatus for simulating the presence of impedance in a transmission line as set forth in claim 1, including current generating means for generating an impedance simulating current, said current generating means having simulating input means and output means, shunt connecting means for applying the current at the output means of said current generating means in shunt with the transmission line, voltage sensing means for establishing a signal which varies substantially only in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line and means for connecting said voltage feedback means to said voltage sensing means and to the simulating input means of said current generating means, the phase relationship between said current generating means, said shunt connecting means, said voltage sensing means and said voltage feedback means being selected to afford a positive simulated impedance.

3. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, current generating means for generating an impedance simulating current, said current generating means having simulating input means and output means, shunt connecting means for applying the current at the output means of said current generating means in shunt with the transmission line, voltage sensing means for establishing a signal which varies substantially only in accordancE with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line and means for connecting said voltage feedback means to said voltage sensing means and to the simulating input means of said current generating means, the phase relationship between said generating means, said connecting means, said sensing means and said feedback means being selected to afford a positive simulated impedance.

4. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, voltage generating means for generating an impedance simulating voltage, said voltage generating means having simulating input means and output means, series connecting means for applying the voltage at the output means of said voltage generating means in series with the transmission line, current sensing means for establishing a signal which varies substantially only in accordance with a signal current through the transmission line, means for electrically connecting said current sensing means to the transmission line, current feedback means for controlling the magnitude and character of the simulated impedance to be introduced in series with the transmission line and means for connecting said current feedback means to said current sensing means and to the simulating input means of said voltage generating means, the phase relationship between said generating means, said connecting means, said sensing means and said feedback means being selected to afford a negative simulated impedance.

5. An apparatus for simulating the presence of impedance in a transmission line as set forth in claim 4, including current generating means for generating an impedance simulating current, said current generating means having simulating input means and output means, shunt connecting means for applying the current at the output means of said current generating means in shunt with the transmission line, voltage sensing means for establishing a signal which varies substantially only in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line and means for connecting said voltage feedback means to said voltage sensing means and to simulating input means of said current generating means, the phase relationship between said current generating means, said shunt connecting means, said voltage sensing means and said voltage feedback means, said voltage sensing means and said voltage feedback means being selected to establish a negative simulated impedance.

6. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, current generating means for generating an impedance simulating current said current generating means having simulating input means and output means, shunt connecting means for applying the current at the output means of said current generating means in shunt with the transmission line, voltage sensing means for establishing signal which varies substantially only in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line and means for connecting said voltage feedback means to said voltage sensing means and to the simulating input means of said current generating means, the phase relationship between said generating means, said connecting means, said sensing means and said feedback means being selected to afford a negative simulated impedance.

7. In an apparatus for sImulating the presence of impedance in a transmission line, the combination of, voltage generating means for generating an impedance simulating voltage, said voltage generating means having input means and output means, series connecting means for applying the voltage at the output means of said voltage generating means in series with the transmission line, current sensing means for establishing a signal which varies in accordance with a signal current through the transmission line, means for electrically connecting said current sensing means to the transmission line, current feedback means for controlling the magnitude and character of the simulated impedance to be introduced in series with the transmission line, means for connecting said current feedback means to said current sensing means and to the input means of said voltage generating means, voltage sensing means for establishing a signal which varies in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, and means for connecting said voltage sensing means to the input means of said voltage generating means.

8. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, current generating means for generating an impedance simulating current, said current generating means having input means and output means, shunt connecting means for applying the current at the output means of said current generating means in shunt with the transmission line, voltage sensing means for establishing a signal which varies in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line, means for connecting said voltage feedback means to said voltage sensing means and to the input means of said current generating means, current sensing means for establishing a signal which varies in accordance with a signal current through the transmission line, means for electrically connecting said current sensing means to the transmission line, and means for connecting said current sensing means to the input means of said current generating means.

9. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, voltage generating means for generating an impedance simulating voltage, said voltage generating means having input means and output means, current generating means for generating an impedance simulating current, said current generating means having input means and output means, series connecting means for applying the voltage at the output means of said voltage generating means in series with the transmission line, shunt connecting means for applying the current at the output means of said current generating means in shunt with the transmission line, current sensing means for establishing a signal which varies in accordance with a signal current through the transmission line, means for electrically connecting said current sensing means to the transmission line, voltage sensing means for establishing a signal which varies in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, current feedback means for controlling the magnitude and character of the simulated impedance to be introduced in series with the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line, means for connecting said current feedback means to said current sensing means and to the input means of said voltage generating means to establish a positive simulated impedance in series with the transmission line, means for connecting said voltage feedback means to said voltage sensing means and to the input means of said current generating means to establish a positive simulated impedance in shunt with the transmission line, means for connecting said voltage sensing means to the input means of said voltage generating means to introduce a signal increasing voltage in series with the transmission line for one direction of transmission therethrough, and means for connecting said current sensing means to the input means of said current generating means to introduce a signal aiding current in shunt with the transmission line for said one direction of transmission therethrough.

10. An apparatus as set forth in claim 9 in which the signal gain resulting from said signal increasing voltage and signal increasing current is substantially equal to the signal loss resulting from the presence of said series and shunt simulated impedances.

11. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, voltage generating means for generating a voltage in series with the transmission line, said voltage generating means having simulating input means, cancelling input means and output means, current generating means for generating a current in shunt with the transmission line, said current generating means having simulating input means, cancelling input means and output means, means for applying the voltage at the output means of said voltage generating means in series with the transmission line, means for applying the current at the output means of said current generating means in shunt with the transmission line, current sensing means for establishing a signal which varies in accordance with a signal current through the transmission line, means for electrically connecting said current sensing means to the transmission line, voltage sensing means for establishing a signal which varies in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, current feedback means for controlling the magnitude and character of the simulated impedance to be introduced in series with the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line, means for connecting said current feedback means between said current sensing means and the simulating input means of said voltage generating means, means for connecting said voltage feedback means between said voltage sensing means and the simulating input means of said current generating means, series control means for causing said voltage generating means to introduce a signal increasing voltage in series with the transmission line, shunt control means for causing said current generating means to introduce a signal increasing current in shunt with the transmission line, means for connecting said series control means between said voltage sensing means and one of the input means of said voltage generating means, means for connecting said shunt control means between said current sensing means and one of the input means of said current generating means, the signal gain resulting from said signal increasing voltage and signal increasing current being substantially equal to the signal loss resulting from the presence of said series and shunt simulated impedances for one direction of transmission through the transmission line.

12. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, voltage generating means for introducing a voltage in series with the transmission line, said voltage generating means having simulating input means, cancelling input means and output means, current generating means for introducing a current in shunt with the transmission line, said current generating means having simulating input means, cancelling input means and output means, means for applying the voltage at the output means of said voltage generating means in series with thE transmission line, means for applying the current at the output means of said current generating means in shunt with the transmission line, current sensing means for establishing a signal which varies in accordance with a signal current through the transmission line, means for electrically connecting said current sensing means to the transmission line, voltage sensing means for establishing a signal which varies in accordance with a signal voltage across the transmission line, means for electrically connecting said voltage sensing means to the transmission line, current feedback means for controlling the magnitudee and character of the simulated impedance to be introduced in series with the transmission line, voltage feedback means for controlling the magnitude and character of the simulated impedance to be introduced in shunt with the transmission line, means for connecting said current feedback means to said current sensing means and to the simulating input means of said voltage generating means, means for connecting said voltage feedback means to said voltage sensing means and to the simulating input means of said current generating means, series impedance compensating means for varying the relative amplitudes of the signals at the simulating and cancelling input means of said voltage generating means as functions of frequency, shunt impedance compensating means for varying the relative amplitudes of the signals at the simulating and cancelling input means of said current generating means as functions of frequency, said functions of frequency being selected to substantially match the impedances looking into the apparatus to the impedances looking into the transmission line.

13. An apparatus as set forth in claim 12 in which the phase relationship between said voltage generating means, said series connecting means, said current sensing means and said current feedback means are selected to establish a negative series simulated impedance and in which the phase relationship between said current generating means, said shunt connecting means, said voltage sensing means and said voltage feedback means are arranged to establish a negative shunt simulated impedance.

14. An apparatus as set forth in claim 12 in which said series impedance compensating means includes first and second series networks having impedances which vary as respective first and second functions of frequency, means for connecting said first series network to said voltage sensing means and to the simulating input means of said voltage generating means, means for connecting said second series network to said voltage sensing means and to the cancelling input means of said voltage generating means, and in which said shunt impedance compensating means includes first and second shunt networks having impedances which vary as respective first and second functions of frequency, means for connecting said first shunt network to said current sensing means and to the cancelling input means of said current generating means and means for connecting said second shunt network to said current sensing means and to the simulating input means of said current generating means.

15. In an apparatus for simulating the presence of impedance in a transmission line, the combination of, voltage generating means for generating a voltage in series with the transmission line, said voltage generating means having input means and output means, current generating means for generating a current in shunt with the transmission line, said current generating means having input means and output means, means for applying the voltage at the output means of said voltage generating means in series with the transmission line, means for applying the current at the output means of said current generating means in shunt with the transmission line, means for controlling the amplitude of the signal at the input means of said voltage generating means in accordance with the magnitude of a signal current through the transmission line to establisH a simulated negative impedance in series with the transmission line, means for controlling the amplitude of the signal at the input means of said current generating means in accordance with signal voltage across the transmission line to establish a simulated negative impedance in shunt with the transmission line, means for varying the difference between the ratio of the voltage which said voltage generating means introduces in series with the transmission line to the signal voltage across the transmission line and the ratio of the current which said current generating means introduces in shunt with the transmission line to the signal current through the transmission line, as a function of frequency, to match the impedances of the apparatus to the impedances of the transmission line over the band of frequencies to be transmitted through the transmission line.