R. F. IMPEDANCE BRIDGE FOR MEASURING REFLECTION COEFFICIENT

• US 3,800,218 A
• Filed: 02/07/1973
• Issued: 03/26/1974
• Est. Priority Date: 02/07/1973
• Status: Expired due to Term

• Current Assignee: Jacob Shekel
• Original Assignee: Jacob Shekel
• Inventors: Shekel, Jacob
• Primary Examiner(s): Krawczewicz, Stanley T.
• Application Number:
  US05/330,275
• Time in Patent Office: 412 Days
• Field of Search: 324/58B,58.5B,57R,DIG.1
• US Class Current: 324/646
• CPC Class Codes: G01R 17/00 Measuring arrangements involving comparison with a reference value, e.g. bridge
• CPC Class Codes: G01R 27/28 Measuring attenuation, gain, phase shift or derived characteristics of electric four pole networks, i.e. two-port networks; Measuring transient response in line transmission systems H04B3/46

Abstract

A bridge for measuring the reflection coefficient of a twoterminal load, in which the insertion loss between an input port and an output port is proportional to the reflection coefficient of the load connected to a third port, and the constant of proportionality is substantially independent of frequency; includes a balun, a first two-terminal network connected in one arm of the bridge, a second two-terminal network connected in the opposite arm of the bridge, and a resistance equal to the reference resistance in the arm opposite the port to which the load is connected. The impedance of the second network is the inverse, relative to the reference resistance, of the parallel combination of the first network and the additional impedance to ground caused by the connection of the balun.

Claims

1. A bridge for measuring the reflection coefficient of a twoterminal load relative to a characteristic impedance Ro, said bridge having a first terminal for connection to said load, a second terminal for connection to a generator, a third terminal for connection to a receiver or a measuring device, a fourth terminal for connection to the respective ground terminals of said load, generator and receiver or measuring device, a fifth terminal, a resistance of value Ro being connected between said second terminal and said fifth terminal, a first two-terminal network being connected between said fifth terminal and said fourth terminal, a second Two-terminal network being connected between said first terminal and said second terminal, a balun having a balanced terminal pair and an unbalanced terminal pair, said balanced terminal pair being connected between said first terminal and said fifth terminal of said bridge, said unbalanced terminal pair being connected between said third terminal and said fourth terminal of said bridge, said second network having an impedance which is substantially equal to the inverse, with respect to Ro, of the parallel combination of said first network and the effective load presented by said balun between said fifth terminal of said bridge and ground.

2. The bridge of claim 1, wherein said balun comprises a section of coaxial cable wound on a ferrite core.

3. The bridge according to claim 1, further comprising an equalizer matched at its input and output to Ro connected between said second terminal and said generator.

4. The bridge according to claim 3, further comprising a second equalizer matched at its input and output to Ro connected between said third terminal and said receiver or measuring device.

5. The bridge according to claim 1, further comprising an equalizer matched at its input and output to Ro connected between said third terminal and said receiver or measuring device.

6. The bridge according to claim 2, further comprising an equalizer matched at its input and output to Ro connected between said second terminal and said generator.

7. The bridge according to claim 6, further comprising a second equalizer matched at its input and output to Ro connected between said third terminal and said receiver or measuring device.

8. The bridge according to claim 2, further comprising an equalizer matched at its input and output to Ro connected between said third terminal and said receiver or measuring device.