1. * GB780054 (A)
Description: GB780054 (A) ? 1957-07-31
Radio frequency propagating systems
Description of GB780054 (A)
PATrENT SPECIFICATION
Date of Application and filing Complete Specification: Oct. 7, 1955,
78,09054 No. 28620/55.
tXN7 ' A ' Application made in United States of America on Oct. 1 1,
1954.
B y: ' Complete Specification Published: July 3!, 1957.
Index at acceptance:-Classes 39(1), D(8:12B4:226.17D:18A:38) and
40(8), U18(AI:
A2:B1:B3:B4A:B4B).
International Classification:-HOljv HO3h.
COMPLETE SPECIFICATION
Radio Frequency Propagating Systems We, STANDARD TELEPHONES AND CABLES
LIMITED, a British Company, of Connaught House, 63, Aldwyeh, London,
W.C.2, England, do hereby declare the invention, for which we pray
that a patent may be granted to us, and the method by which it is to
be performed, to be particularly described in and by the following
statement:This invention relates to radio frequency propagating
systems for use in the ultra high frequency range.
It has been proposed heretofore to provide the standard type of hollow
rectangular waveguide with a gas discharge tube for attenuation, phase
modulation and switching purposes. Such waveguides, however, are
characteristically narrow band and in order to cover a wide frequency
range, such as 1000 megacycles to 10,000 megacycles, for example, six
different waveguide sizes are required.
One of the objects of this invention is to provide a novel combination
waveguide and gas discharge arrangement suitable for operation over
bands of frequency far exceeding that possible with the aforementioned
rectangular type of waveguide and gas discharge tube combination.
Another object is to provide a novel structure for direct current
isolation of desired portions of a waveguide structure and a further

2. object is to utilise this isolation feature to provide one or more
resonant sections along the waveguide for band-pass filtering
operation.
According to the present invention there is provided a radio frequency
propagating system, comprising a first conductor, a second conductor,
means disposing said conductors in dielectrically spaced,
substantially parallel relation, said first conductor being wider than
said second conductor to present thereto a planar surface so that the
electric field distribution of [Price 3/6] radio frequency waves to be
propagated thlerealong is in a mode approximating the TEM mode, thus
enabling propagation of wave energy over a broad band of frequencies,
a gas discharge device disposed with50 respect to said conductors to
intercept at least part of the electric field therebetween and means
to control the ionisation of the gaseous medium contained in said
device.
The invention will become more apparent by reference to the following
description taken in conjunction with the accompanying drawings, in
which:
Fig. 1 is a view in plan of the combination waveguide and gas
discharge device 60 of this invention; Fig. 2 is a view in side
elevation ofE Fig. 1; Fig. 3 is a view in cross-section taken along
lines 3-3 of Fig. 2; 66 Fig. 4 is a view in plan with the gas tube
shown in section of a modified waveguide and gas tube arrangement; and
Fig. 5 is a longitudinal cross-sectional view taken along lines 5-5 of
Fig. 4. 70 Referring to Figs. 1 to 3, a section of Microstrip
waveguide is shown which includes a first or planar eonduetor 1, a
second or strip conductor 2, and a layer of dielectric material 3
which separates the 75 conductors 1 and 2 in parallel relation.
The dielectric material may comprise polyethylene, polystyrene, a
substance known under the Registered Trade Mark "Teflon," fibre glass
or laminations of fibre80 glass and "Teflon," or other suitable
material of dielectric quality, or if the Microstrip structure permits
the dielectric may be air. The dielectric layer 3 is provided with a
cutout 4 which is slightly85 wider than the strip conductor 2 and
directly underlying the strip 2. In this cutout is a flat elongated
glass tube 5 containing a gaseous material, such as neon in a thin
strata only a small fraction of 90 2 780,054 a wavelength in
thickness. The ends of the glass envelope 5 extend laterally as
indicated at 6 and 7 where they terminate about electrodes 8 and 9.
The electrodes may he coupled to a source of biasing voltage 10
controlled by a rheostat 11 which is coupled in series with a source
of modulating voltage 12. While the cutout 4 may extend to one side
edge of the conductor 101, it is preferable to retain or replace the
portion of the dielectric indicated at 13 so as to avoid an unbalanced

3. line dielectrically along the tube. If desired, the dielectric
material may be removed on both sides of the tube 5. In either case
the cutout presents a discontinuity in the line and requires some
alteration in the line or some form of tuning means to o-vercomre the
effect of this discontinuity. As shown in Figs. 1-3, small tuning
stubs 4a and 4b may be provided at the ends of the cutout 4, the stubs
being in the form of smnall conductive projections soldered to or made
integral with the conductor 2. For further information on use of these
tuning devices reference is made to British Patent Specifieations Nos.
761,761 and 761,762. If desired the discontinuity of the cutout 4 may
be overcome by narrowing the space between conductors 1 and 2 through
the cutout.
In this embodiment the gas tube provides for several possible
functions. It may be used for attenuating the propagation of wave
energy along the line or it may he used as a phase shifter, amplitude
or phase modulator, or as a switch. The tube 5 in the position shown
intercepts substantially all or at least a very high percentage of the
electric field which exists between the eonductors 1 and 2. When the
gaseous medium is ionised, the gas plasma absorbs the radio frequency
energy and, depending upon the pressure of the gas and the degree of
ionisation, substantially complete absorption can be obtained, thus
operating as a switch. The bias 10 may be controlled by rheostat 11 to
place the gas in partial ionisation and the souree 5012 which may be a
signal wave or pulse source, may be utilised to rmodulate the wave
energy by v-arying the degree of ionisation of the gas.
Referring to Figs. 4 and 5, the strip conductor is divided into two
portions 2a and 2b to which is secured a gas discharge device 14 which
comprises an envelope 15 in-to which projects two strip sections 16
and 17. The inner ends of the sections 16 and 17 are shaped to provide
a V gap 18 corresponding to the V-shaped gaps disclosed in British
Patent Specification No.
761,778. This form of gap is particularly adapted for the propagation
of radio frequeney energy while operating to isolate the two
strip.-etins eleetrically. The strip portions 1G aml, 17 may be
disposed in overlapping relation to the ends of strip sections 2a and
2A t, which they may be secured as by soldein. as indicated at 19. 70
While separate elec trodes may be provided within the e vec]ope 15, we
prefer to utilise the strip se1t. ns 16 and 17 to effect ionisation of
the a. This is done by providing two coaxial couplers 20 and 2175
which are coupled l.t oIpposite ends of the device. The plianai
conductor lt is provided with an opening 22 alboutl which the outer
conductor 2:. of the coupler 20 is secured. The inner e;ndutor 24 of
the80 coupler unit extends through the opening 22 and is conneted
direetly to the strip conductor la. as indicated at 25. The coupler 20

4. is pr1,i led with a movable plunmer 26 whlich Las an annular sleeve of
85 dielectric material 27 to electrically insulate the
inner,on.1iictojr from the outer conductor. By adjusting the plunger
26 with respect to the iunction 25. a suseeptance is provided in the
Microstrip line 90 which presents in conjuncetion with the gap 18 a
resonant section having a band pass characteristic. The position of
the plunger 26 determines the value of the suseeptance. The spacing of
the junction95 23 with respect to the gap 18 is selected to
approximate a half wavelength. The coupler 21 which is likewise
coupled to Ihe strip 2b at 28 is provided with adjustable plunger 29
which,,erates as a short be-100 tween the inner and outer conductors
30 and 31. By adjustingo plunger 29 approximately a qluarter
wavelength from the strip 2b allowing for the dielectric constant of
material 3a. this provides a minirnml of reflection of the radio
frequency flowing along the Microstrip line. This coupling 21 provies
for a direct current return circuit between the strip portion 17 and
around and the source of biasing 110 potential 33. By applying a bias
on the portions 16 and 17 the gaseous medium of tube 14 is ionised as
may be required. In the provision of the direct current returned
circuit througlh coupler 21, it 115 should be noted that the
MIierostrip conduetor 2a and other circuitry to wvhich it may be
coupled are maintained isolated with respect to ground or the planar
eonduetor la. 120 In order to overcome the discontinuity provided by
the cutout 34. tuning stubs and 36 may be provided adjacent the ends
of the eutodt:34 similarly as provided in connection witl the cutout 4
in Figs. 125 1. 2 and 3.
In operation of t e emnlodiment illustrated in Figs. 4 ait 5. let it
he assumed that the embodiment is to be utilised as a band pass
filter. In this case, the tube 14 130 780,054 780,054 is maintained in
an un-ionised condition so that the susceptance value of the gap 18 is
utilised to provide the desired resonant circuit. When it is desirable
to block the band pass frequencies, the tube 14 is ionised by applying
a positive bias from source 33 thus ionising the gaseous medium to
attenuate the flow of wave energy along the Microstrip. The gas plasma
thus formed absorbs the wave energy thereby blocking its passage. This
switching function may act as a complete blocking of wave energy or it
may be so controlled as to change the band pass characteristic of the
filter in addition to its function as an attenuator. For example, if
the gap 18 is relatively wide the gas plasma may function to change
the susceptance value thereof thus changing the band pass
characteristics of the filter. However, if the gap 18 is relatively
small, the gas plasma may have relatively small detuning effect on the
gap suseeptance and would in that case function only as an attenuator
to the band pass frequencies.

5. While we have shown only one filtering section in the embodiment of
Figs. 4 and 5, it will be readily apparent to those skilled in the art
that the unit may be multiplied to form a series of filtering or
resonant sections, each of which may be controlled independently with
regard to the ionisation of the gaseous medium surrounding the gap 18.
In this way the overall band pass characteristics could be varied by
ionising the gaseous medium at one or more of the gaps.
Gases other than neon may be used in tubes 5 and 14. The gas or gas
mixture used should be light with a high ionisation potential for
rapid diffusion and high breakdown power. Helium and hydrogen either
alone or mixed at an appropriate pressure are particularly
satisfactory for this purpose. For further information on the gas and
gas pressure that may be used reference is made to British Patent
Specification No. 761,869.
* Sitemap
* Accessibility
* Legal notice
* Terms of use
* Last updated: 08.04.2015
* Worldwide Database
* 5.8.23.4; 93p