WO1997008772A1

WO1997008772A1 - Printed 180 degree differential phase shifter

Info

Publication number: WO1997008772A1
Application number: PCT/US1996/013699
Authority: WO
Inventors: Leo Maloratsky; John Ide
Original assignee: Alliedsignal Inc.
Priority date: 1995-08-23
Filing date: 1996-08-21
Publication date: 1997-03-06

Abstract

A printed 180 degree differential phase shifter includes a short nonuniform nonregular line (10) and a uniform transmission line (12). The nonuniform nonregular line consists of two broadside coupled lines (13, 14) of both sides of a thin dielectric substrate (19).

Description

PRINTED 180 DEGREE DIFFERENTIAL PHASE SHIFTER

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. Patent Application Serial No.

08/234,487, filed April 28, 1994 by the present inventors. BACKGROUND OF THE INVENTION

The present invention relates to VHF and microwave miniature receivers and transmitters and more particularly to high power amplifiers,

modulators, and phase array antennas.

Differential phase shifters are well known in the art. Typical differential phase shifters, however, require diodes, inductors, capacitors, ferrites. Λ/4 couplers and interconnecting cables. These components and their interconnections increase size, cost and line losses while causing a decrease in reliability. It is an object of the present invention to provide a differential phase shifter having no such components and therefore having improved reliability and a reduced size at a reduced cost.

SUMMARY OF THE INVENTION This invention contemplates a printed 180 degree differential phase shifter including a short

nonuniform (coupled) nonregular (without ground plane) line and a uniform (single) transmission line of the same length. The nonuniform, nonregular line consists of two broadside coupled lines on both sides of a thin dielectric substrate without ground

metallization in the area of coupled lines. Strong magnetic coupling between coupled lines provides miniaturization of the phase shifter. The output port of the first coupled line is electrically connected with the opposite end of the second coupled line and with the ground plane of the uniform line.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates an expanded isometric view of one embodiment of the present invention.

Figure 2 illustrates dependence of phase shift (in degrees) and loss (in dB) on relative detuning (in percent) for a thin dielectric with a thickness of 0.003" and a length of coupled lines of 0.055".

Figure 3 is a diagrammatic representation illustrating the implementation of the 180 degree phase shift.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings. Figure 1 shows the printed 180 degree differential phase shifter of the invention including uniform transmission line 12 and nonuniform nonregular line 10. Nonuniform (coupled) nonregular (without ground plane) line 10 contains two parallel broadside coupled lines 13 (top) and 14 (bottom) located on both sides of a thin dielectric substrate 15. In this invention the coupled lines 13 and 14 have very strong magnetic coupling to provide small length of these lines. Magnetic coupling is determined by the coefficient of magnetic coupling k = M/Lo, where M is mutual inductance per unit of length, Lo is self-inductance per unit of length; 0<k<1. For strong coupling k is equal to

0.85...1.0. In many cases for maximization of k (k →1) iron or ferrite cores are used. However, it diminishes thermostability, has high cost and increases the dimensions of the components. In this invention the method of magnetic coupling

activization without any cores issued. Strip coupled lines are printed on two sides of the thin electric substrate to provide strong magnetic coupling. This effect is intensified by elimination of the ground plane from area 27 directly below the coupled lines. For example, at a thickness of substrate 0.02" k equals 0.9, and at a thickness 0.002" k equals 0.97. When k grows from 0.85 to 0.99 the length of said coupled lines is decreased 10 times.

Coupled lines 13 and 14 have a short circuit connection between end 16 of said line 13 and end 17 of said line 14. Said short circuit connection is connected to ground plane 18 of uniform transmission lien 12. Ground plane 18 is located on base

dielectric substrate 19. In Figure 1 input (or output) 20 and output (or input) 22 of the coupled lines are electrically interconnected with

corresponding input (or output) 21 and output (or input) 23 on said base dielectric substrate 19.

Input (or output) 11 and output (or input) 25 of uniform line 12 are electrically interconnected with corresponding input (or output) 24 and output (or input) 26 on said base dielectric substrate 19.

Inputs (outputs) 21, 24 and outputs (inputs) 23, 26 may be configured for various applications and located on said base dielectric substrate 19.

Electrical length of nonuniform nonregular line 10 is equal to the electrical length of uniform line 12. Electrical length 0₁₀ of said line 10 is equal to

. Λ₁₀ is equal to the wavelength in said line 10. 1₁₀ is equal to the geometric length of said line 10 which is equal to the line cdef of Figure 1 which ranges from 0.02 Λ₁₀ to 0.08⋀₁₀. This length depends on the coefficient of magnetic coupling k.

The electrical length Ө₁₂ of uniform line 12 is equal to

. Λ₁₂ is equal to tbe wavelength in uniform line 12. 1₁₂ is equal to the geometric length of uniform line 12 which is equal to line ghij of Figure 1 which equals (0.02...0.08) Λ₁₂. In general, wavelengths Λ₁₀ and Λ₁₂ are not equal, therefore, for Ө₁₀ = Ө₁₂ or

it: is necessary that

. 1₁₂.

The length of the nonuniform nonregular line depends on the thickness of dielectric substrate 15. For example, the length of broadside coupled lines on the dielectric with thickness 0.003" is equal to 0.005Λ₁₀, and the length of the uniform line is equal to .055Λ₁₂.

For very short nonuniform nonregular line

10 (Ө₁₀< 0.01) from Kirchhoff's current rule it follows that the current in input 20 is equal and opposite in direction, whereby the current in output 22, i.e. the phase shift in said line 10 is 180 degrees. For short nonuniform nonregular line 10 (Ө₁₀>0.01) the 180 degree phase shift is obtained as a result of subtraction of the uniform line phase response. The concept of the invention and its implementation can be achieved in different ways. For example, a configuration of the compact printed nonuniform nonregular line and the uniform line can be realized by a meander line, a spiral line, etc. The uniform line can be based on any planar

transmission line (microstrip, stripline, etc.).

Considering the arrangement shown in Figure 3, VHF or microwave signals are applied to input port 24 of the uniform line and port 21 of nonuniform

nonregular line 10. These signals pass through the differential phase shifter and appear at outputs 26 and 23, respectively, having differentional phase 180 degrees: the signal in output port 23 has the lagging phase in comparison with the phase of the signal in output port 26.

Similarly, if input ports 26 and 23 are properly terminated and input signals are applied to these input ports, the resulting signals at outputs 24 and 21, respectively, have differentional phase shift 180 degrees: the signal in output port 21 has the lagging phase in comparison with the phase of the signal in output port 24.

The uniform line of variable length can be used for adjustment of a phase shift. Figure 2 shows dependence of a phase shift (in degrees) and loss (in dB) on relative detuning (in percent) for a thin "Kapton" dielectric with thickness 0.003" and a length of coupled lines 1₁₀ = 0.055Λ₁₀. The uniform microstrip line is printed on the same "Kapton" substrate which is connected with said base

dielectric substrate made of "Duroid 5880". It can be seen that this gives a phase shift equal to 180 degrees + 5 degrees and losses that are less than 0.3 dB for a relative detuning of + 5 percent (center frequency equals 120 MHz). Other phase shift accuracies, losses and bandwidth performance

combinations can be obtained by appropriate selection of the thickness of the thin dielectric substrate and the length of said coupled lines.

With the above in mind it will be understood that nonuniform nonregular line 10 with input and output transmission lines 21 and 23 is equivalent to a two-port network (Figure 3). The notation is kept the same as in Figure 1. From Kirchhoff"s current rule it follows (Figure 3) that if the currents in two input poles 21 and 18 of the two-port network are equal and opposite in direction, then the current in two output poles 23 and 18 are likewise equal and opposite in direction.

If I = -I₁' then I₂ = -I'₂. (1)

Currents in top 13 and bottom 14 coupled lines of the very short nonuniform

nonregular line 10 are determined by: I₀₂ = -I₀₁ . (2) From Kirchhoff's current rule (Figure 3) it follows that: I₀₂ = I₂ + I₃

(3) I₀₁ + I₃ = I'₁

Applying equations (1) and (2) to equation (3) it is seen that I₁ = I'₂. Thus, the phase shift in the given nonuniform nonregular line is 180 degrees.

It is not intended that this invention be limited to the hardware arrangement or operational procedures shown disclosed. This invention includes all of the alterations and variations thereto as encompassed within the scope of the claims as follows.

Claims

WHAT IS CLAIMED IS:

1. A printed 180 degree differential phase shifter comprising:

a thin dielectric substrate mounted to a base;

a uniform transmission line mounted on said thin dielectric substrate comprising an input and an output;

a nonuniform nonregular line without ground mounted on said thin dielectric substrate comprising an input and output;

wherein said uniform transmission line and said nonuniform nonregular line have equal electrical length which depends on thickness of said thin electric substrate.

2. A printed 180 degree differential phase shifter as claimed in claim 1 wherein said nonuniform nonregular line comprises:

two parallel broadside coupled lines mounted on each side of said thin dielectric

substrate.

3. A printed 180 degree differential phase shifter as claimed in claim 2 wherein said two parallel broadside coupled lines mounted on each side of said thin dielectric substrate have high magnetic coupling.

4. A printed 180 degree differential phase shifter as claimed in claim 3 wherein each of said two parallel broadside coupled lines mounted on each side of said thin dielectric substrate comprise short opposite connections.

5. A printed 180 degree differential phase shifter as claimed in claim 4 wherein said short opposite connections connect each of said two parallel broadside coupled lines to ground connected to said base.

6. A printed 180 degree differential phase shifter as claimed in claim 2 further comprising two short circuits between opposite ends of each of said two parallel coupled lines and a ground of said uniform line.

7. A printed 180 degree differential phase shifter as claimed in claim 5 wherein said ground is common to said uniform transmission line.

8. A printed 180 degree differential phase shifter as claimed in claim 2 wherein said nonuniform nonregular line and said uniform transmission line have equal input and output impedances.

9. A printed 180 degree differential phase shifter as claimed in claim 2 wherein said two parallel broadside coupled lines are removed from ground of said uniform line.

10. A printed 180 degree differential phase shifter comprising: thin dielectric substrate means mounted to a base;

uniform transmission line means mounted on said thin dielectric substrate means comprising an input and an output;

nonuniform nonregular line means mounted on said tin dielectric substrate means comprising an input and an output wherein said nonuniform line means comprises two parallel broadside coupled lines mounted on each side of said thin dielectric

substrate;

wherein said uniform transmission line means and said nonuniform nonregular line means have equal electrical length dependent on thickness of said thin dielectric substrate means.

11. A printed 180 degree differential phase shifter as claimed in claim 10 further comprising two short circuits connecting opposite ends of each of said two parallel broadside coupled lines with a ground of said uniform line means.