Variable differential phase shifter providing phase variation of

Details Variable differential phase shifter providing phase variation of Variable differential phase shifter providing phase variation of

1996-05-23

1998-09-01

Pascal, Robert

Wave transmission lines and networks

Plural channel systems

Having branched circuits

333160, 333245, 333263, 333 24C, H01P 118, H01P 504

Patent

active

058016007

DESCRIPTION:

BRIEF SUMMARY
This application claims benefit of international application PCT/NZ94/00107 filed Oct. 14, 1994.


THE TECHNICAL FIELD

The present invention relates to a variable differential phase shifter. The variable differential phase shifter of the invention allows the phase of two output signals to be continuously varied over a given range with respect to an input signal. The variable differential phase shifter of the invention is particularly suitable for use in tilting the beam of an antenna array.


BACKGROUND OF THE INVENTION

Referring to FIG. 1 a prior art antenna array consisting of four elements 1-4 is shown. Feed-line 5 supplies a signal to drive the antenna elements 1-4. The signal from line 5 is equally divided between branches 6 and 7. Feed line 6 supplies the driving signal to antenna elements 1 and 2. The signal from branch 6 is further divided between branches 9 and 10. A phase shifter 11 is provided in branch 10 to shift the phase of the signal supplied to antenna element 2 by .beta. with respect to the phase of the signal driving antenna element 1. In branch 7 phase shifter 8 introduces a phase shift of 2.beta. with respect to the phase of the signal in branch 6. This phase shifted signal is divided between branches 12 and 13. Antenna element 3 thus receives a driving signal which is phase shifted by 2.beta.. A further phase shift element 14 is provided in branch 13 so that the signal driving antenna element 4 is phase shifted by 3.beta..
Accordingly, the antenna elements 1, 2, 3, 4 are phase shifted by an amount 0, 1.beta., 2.beta., 3.beta. respectively. In this way the beam of the antenna array can be tilted by a desired amount. Sometimes, to control side lobe levels and beam shape, other than progressive phase shift may be employed. Non-equal power division may also be employed.
In prior art systems phase shifters 8, 11 and 14 may be lengths of cable or active phase shifters. Commonly, active phase shifters using PIN diodes are employed which can be switched on or off to introduce phase shifts in a branch of the feed network. The phase shifters may include a number of PIN diodes to allow a number of delays of different magnitudes in be introduced into a feed path as required.
Such prior art phase shifters suffer from the disadvantage that they can usually only provide phase shifts between respective branches in a stepped manner and cannot usually provide continuous differential phase shifting between branches. Further, high power PIN diodes used in active systems are both expensive, particularly where a large number of antenna elements are employed and have higher losses than the present device. Active systems using PIN diodes also introduce non-linearities and intermodulation.
Other particular advantages of the present invention are as follows:
Because there are no sliding metal contacts, the phase shifter will require little maintenance. If a suitable dielectric is used (for example polytetrafluoroethylene) the sliding friction will be low. This in an advantage when designing mechanical drive mechanisms or selecting suitable electric motors. Because there are no sliding electrically conductive surfaces in contact, the phase shift variation speed can be maximised.
Also, for a required differential phase shift, the amount of mechanical movement is half that required by in-line phase shifters. This may result in a more compact structure. Finally, incorporating a matching section in the phase shifter structure reduces the manufacturing cost of a typical feed network.


DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a variable differential phase shifter which overcomes the above disadvantages or at least provides the public with a useful choice.
According to one aspect of the invention there is provided a variable differential phase shifter comprising: tube coupled at ends thereof to first and second outputs; slideable therealong; and slideable therealong; the inner and outer sleeves being connected to an input and being slideable along said coaxial line in fixed r

REFERENCES:
patent: 4446463 (1984-05-01), Irzinski
patent: 4570134 (1986-02-01), Woodward
patent: 4602227 (1986-07-01), Clark et al.
patent: 4616195 (1986-10-01), Ward et al.
patent: 4635062 (1987-01-01), Bierig et al.
patent: 4755778 (1988-07-01), Chapell
patent: 4843355 (1989-06-01), Knorr
patent: 4849763 (1989-07-01), DuFort

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