AMPLITUDE-LINEAR DIFFERENTIAL PHASE SHIFT CIRCUIT

• US 20080111607A1
• Filed: 11/10/2006
• Published: 05/15/2008
• Est. Priority Date: 11/10/2006
• Status: Abandoned Application

• Current Assignee: EH Antenna Systems, LLC
• Original Assignee: EH Antenna Systems, LLC
• Inventors: Hart, Robert T.
• Application Number:
  US11/558,522
• Publication Number:
  US 20080111607A1
• Time in Patent Office: Days
• US Class Current: 327/255
• CPC Class Codes: H01P 1/18 Phase-shifters H01P1/165 takes precedence
• CPC Class Codes: H03H 7/461 particularly adapted for use in common antenna systems

Abstract

A broad frequency range phase shift circuit is responsive to a radio-frequency signal generated by a radio-frequency source and generates a lagging phase signal and a leading phase signal, 90° out of phase with the lagging phase signal, corresponding to the radio-frequency signal. An operational amplifier has a signal input that receives the radio-frequency signal from the radio-frequency source and generates a low impedance amplified output signal. A series resonant circuit receives the amplified signal from the operational amplifier and shifts the phase of the amplified signal in an amount that approaches 90° as the amplified signal frequency approaches DC to 0° as the amplified signal frequency increases to the cut-off frequency. A transmission line receives the amplified signal from the operational amplifier and has an electrical length substantially equal to one-fourth of a wavelength corresponding to the cut-off frequency.

Claims

1. A phase shift circuit, responsive to a radio-frequency signal generated by a radio-frequency source, for generating a lagging phase signal corresponding to the radio-frequency signal and a leading phase signal corresponding to the radio-frequency signal that is 90°

out of phase with the lagging phase signal, the radio-frequency signal having a frequency between DC and a preselected cut-off frequency, the phase shift circuit comprising;

a. an operational amplifier having a signal input that receives the radio-frequency signal from the radio-frequency source and that generates a low impedance amplified output signal;

b. a series resonant circuit that receives the amplified signal from the operational amplifier and that shifts the phase of the amplified signal in an amount that approaches 90°

as the amplified signal frequency approaches DC to 0°

as the amplified signal frequency increases to the cut-off frequency; and

c. a transmission line that receives the amplified signal from the operational amplifier and that has an electrical length substantially equal to one-fourth of a wavelength corresponding to the cut-off frequency.

2. The phase shift circuit of claim 1, wherein the transmission line comprises a coaxial cable.

3. The phase shift circuit of claim 1, further comprising a resistor, having an impedance that matches the transmission line, that is in series between the amplified signal and the transmission line.

4. The phase shift circuit of claim 1, wherein the series resonant circuit includes an inductor that is coupled to the amplified signal and a capacitor that is in series with the inductor, and a terminating resistor, the inductor and the capacitor chosen so that the series resonant circuit elements have a preselected Q relative to the terminating resistor.

5. The phase shift circuit of claim 4, wherein the preselected Q has a nominal value of 0.707.

6. An amplitude-linear differential phase shift circuit that is responsive to a radio-frequency signal, comprising:

a. an operational amplifier responsive to the radio-frequency signal that generates an amplified signal having a predetermined gain;

b. a leading phase shift circuit that generates a leading phase signal corresponding to the amplified signal so that the leading phase signal leads the radio-frequency signal by 90°

when the radio-frequency signal has a frequency that approaches DC and decreases linearly to 0°

when the radio-frequency signal has a frequency equal to the predetermined cut-off frequency; and

c. a lagging phase shift circuit that generates a lagging phase signal corresponding to the amplified signal so that the lagging phase signal lags the radio-frequency signal by an amount that approaches 0°

when the radio-frequency signal has a frequency that approaches DC and that increases linearly to 90°

when the radio-frequency signal has a frequency equal to a predetermined cut-off frequency,

so that a constant phase difference of 90°

is maintained between the lagging phase signal and the leading phase signal.

7. The amplitude-linear differential phase shift circuit of claim 6, wherein the lagging phase shift circuit comprises a transmission line.

8. The amplitude-linear differential phase shift circuit of claim 7, wherein the transmission line has an electrical length equal to one quarter of a wavelength corresponding to the cut-off frequency.

9. The amplitude-linear differential phase shift circuit of claim 7, wherein the transmission line comprises a coaxial cable.

10. The amplitude-linear differential phase shift circuit of claim 6, wherein the leading phase shift circuit comprises an inductor that is coupled to the amplified signal and a capacitor that is in series with the inductor, the inductor and the capacitor chosen so that the series resonant circuit has a preselected Q at the cut-off frequency.

11. The amplitude-linear differential phase shift circuit of claim 10, wherein the preselected Q has a nominal value of 0.707.

12. A linear vector addition diversity combiner circuit, for combining a first radio-frequency signal and a second radio-frequency signal, comprising:

a. a leading phase shift circuit that generates a leading phase signal corresponding to the second radio-frequency signal so that the leading phase signal leads the second radio-frequency signal by an amount that approaches 90°

when the second radio-frequency signal has a frequency that approaches DC and increases linearly to 0°

when the second radio-frequency signal has a frequency equal to the predetermined cut-off frequency, the leading phase signal coupled to the first node;

b. a lagging phase shift circuit that generates a lagging phase signal corresponding to the first radio-frequency signal so that the lagging phase signal lags the first radio-frequency signal by an amount that approaches 0°

when the radio-frequency signal has a frequency that approaches DC and increases linearly to 90°

when the radio-frequency signal has a frequency equal to a predetermined cut-off frequency, the lagging phase signal coupled to a first node; and

c. an operational amplifier responsive to the first node that generates a combined signal that includes components of both the lagging phase signal and the leading phase signal.

13. The linear vector addition diversity combiner circuit of claim 12, wherein the lagging phase shift circuit comprises a transmission line.

14. The linear vector addition diversity combiner circuit of claim 13, wherein the transmission line has an electrical length equal to one quarter of a wavelength corresponding to the cut-off frequency.

15. The linear vector addition diversity combiner circuit of claim 13, wherein the transmission line comprises a coaxial cable.

16. The linear vector addition diversity combiner circuit of claim 12, wherein the leading phase shift circuit comprises an inductor and a capacitor that are coupled to the amplified signal and a terminating resistor, the inductor and the capacitor having a preselected Q relative to the terminating resistor at the cut-off frequency.

17. The linear vector addition diversity combiner circuit of claim 16, wherein the preselected Q has a nominal value of 0.707.

18. A method of generating a pair of signals, each corresponding to a radio-frequency signal, comprising the steps of:

a. generating a leading phase signal corresponding to the radio-frequency signal so that the leading phase signal leads the radio-frequency signal by an amount that approaches 90°

when the radio-frequency signal has a frequency that approaches DC and decreases linearly to 0°

when the radio-frequency signal has a frequency equal to the predetermined cut-off frequency; and

b. generating a lagging phase signal corresponding to the radio-frequency signal so that the lagging phase signal lags the radio-frequency signal by an amount that approaches 0°

when the radio-frequency signal has a frequency that approaches DC and increases linearly to 90°

when the radio-frequency signal has a frequency equal to a predetermined cut-off frequency,

so that a constant phase difference of 90°

is maintained between the lagging phase signal and the leading phase signal.

19. The method of claim 18, further comprising the step of feeding the radio-frequency signal into an operational amplifier, thereby generating an amplified signal, prior to the steps of generating a lagging phase signal and generating a leading phase signal.

20. The method of claim 19, wherein the step of generating a lagging phase signal comprises the step of feeding the amplified signal into a transmission line having an electrical length equal to one quarter of a wavelength corresponding to the cut-off frequency.

21. The method of claim 19, wherein the step of generating a leading phase signal comprises the step of feeding the amplified signal into a leading phase shift circuit that includes an inductor and a capacitor that is in series with the inductor that are coupled to the amplified signal, and a terminating resistor, the inductor and the capacitor having a preselected Q with a nominal value of 0.707, relative to the terminating resistor, at the cut-off frequency.

22. A method of combining a first radio-frequency signal with a second radio-frequency signal, comprising the steps of:

a. generating a leading phase signal corresponding to the second radio-frequency signal so that the leading phase signal leads the second radio-frequency signal by an amount that approaches 90°

when the radio-frequency signal has a frequency that approaches DC and decreases linearly to 0°

when the radio-frequency signal has a frequency equal to the predetermined cut-off frequency;

b. generating a lagging phase signal corresponding to the first radio-frequency signal so that the lagging phase signal lags the first radio-frequency signal by an amount that approaches 0°

when the radio-frequency signal has a frequency that approaches DC and increases linearly to 90°

when the radio-frequency signal has a frequency equal to a predetermined cut-off frequency; and

c. feeding the lagging phase signal and the leading phase signal into an input of an operational amplifier, thereby generating a vector-combined signal that includes components of both the lagging phase signal and the leading phase signal.

23. The method of claim 22, wherein the step of generating a lagging phase signal comprises the step of feeding the first radio-frequency signal into a transmission line having an electrical length equal to one quarter of a wavelength corresponding to the cut-off frequency.

24. The method of claim 22, wherein the step of generating a leading phase signal comprises the step of feeding the second radio-frequency signal into a leading phase shift series resonant circuit that includes an inductor, a capacitor and a terminating resistor, the inductor and the capacitor chosen to have a Q with a nominal value of 0.707 relative to the terminating resistor at the cut-off frequency.