SHIN CHEON WOO (KR)
| KR20000063239A | 2000-11-06 | |||
| JPH07212131A | 1995-08-11 | |||
| US5216388A | 1993-06-01 |
BACKGROUND ART A millimeter wave integrated circuit, NRD Guide, has characteristics such as the low loss and non-radiativeness, etc.
An NRD Guide circuit is constructed by maintaining the gap between the upper conducting plate and the lower conducting plate as a half wave length of the frequency to be used or shorter and by positioning a dielectric transmission line that has a certain constant width and the height which is the same as the gap between the upper conducting plate and the lower conducting plate.
DISCLOSURE OF THE INVENTION Millimeter waves generated from a Gunn diode mount (6) on which a Gunn diode (14) is mounted are fed by a strip resonator (7). The FM modulation is performed by using a VCO located at the rear of the oscillation unit and comprised of the front Teflon (8) which has the length of LI and a certain air gap (d), a high permittivity sheet (9), a Varactor diode mount (10) and the rear Teflon (12) that has the length of L2. In order to transmit modulated signals, the present invention further comprises a mode
suppressor (5), an NRD Guide (3) and an antenna (4).
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a perspective view of an FM modulation transmitter equipped with a VCO that includes a Varactor diode at the rear of the Gunn diode oscillation unit.
Figure 2 illustrates a top view of an FM modulation transmitter equipped with a VCO that includes a Varactor diode at the rear of the Gunn diode oscillation unit.
Figure 3 illustrates an enlarged top view of a Gunn diode oscillation unit and a VCO that includes a Varactor diode at the rear of the Gunn diode oscillation unit.
Figure 4 illustrates a perspective view of a Gunn diode mount that includes a Gunn diode.
Figure 5 illustrates a strip resonator for feeding millimeter waves oscillated at the Gunn diode to the NRD Guide.
Figure 6 illustrates a mode suppressor for suppressing the unnecessary mode generated when millimeter waves are fed.
Figure 7 illustrates enlarged views of a Varactor diode mount and the Varactor diode.
Figure 8 is a graph that illustrates frequency shift depending on air gap.
Figure 9 is a graph that illustrates change of usable frequency range depending on change of length of the front Teflon.
Figure 10 is a graph that illustrates change of usable frequency range depending on change of length of the rear Teflon.
Figure 11 is a graph that illustrates frequency modulation characteristics
depending on air gap when the reverse bias voltage is applied to the Varactor diode where the VCO is placed at the rear of the oscillation unit.
**Description of the code at an important part of a diagram** 1: Upper Conducting Plate 2: Lower Conducting Plate 3: NRD Guide 4: Rod Antenna 5: Mode Suppressor 6: Gunn Diode Mount 7: Strip Resonator 8: Front Teflon 9: High Permittivity Sheet 10: Varactor Diode Mount 11: Electric Wire (semi-rigid) for Supplying Reverse Bias Voltage to Varactor Diode 12: Rear Teflon 13: Choke Type Substrate for Supplying Bias to Positive Terminal of Gunn Diode 14: Gunn Diode 15: Thin Teflon 16: Metal (Copper) Thin Film 17: Varactor Diode d: Gap Between Strip Resonator and Front Teflon LI : Thickness of Front Teflon
L2: Thickness of Rear Teflon BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will now be explained in detail with references to the attached drawings.
Figure 1 illustrates a perspective view of an FM transmitter equipped with an oscillation unit, modulation unit and antenna between the upper conducting plate and the lower conducting plate (1,2). The modulation unit comprises a Gunn diode mount (6) on which a Gunn diode (14) is mounted, a strip resonator (7) and a mode suppressor (5). The modulation unit comprises the front Teflon (8), a piece of high permittivity sheet (9), a Varactor diode mount (10) and the rear Teflon (11). Modulated signals are fed to a rod antenna (4) through an NRD Guide (3) and radiated.
Figure 2 illustrates a top view of an FM modulation transmitter equipped with a VCO in the rear, according to the present invention.
Figure 3 illustrates an enlarged top view of the oscillation unit and the modulation unit. The Gunn diode (14) is mounted on the Gunn diode mount (6) as illustrated in Figure 4. The Gunn diode mount oscillates millimeter waves by applying bias through the bias choke (13).
The oscillated millimeter waves are supplied to the NRD Guide (3) using the dielectric substrate (7) that has permittivity of 2.56 and thickness of 0.3mm as illustrated in Figure 5. Also, the mode suppressor (5) is inserted for suppressing unnecessary mode that is generated when millimeter waves are fed.
The modulation unit is mounted with a certain air gap from the strip resonator (7). The air gap (d) plays a key role in determining frequency shift corresponding to the voltage at the time of the FM modulation. Figure 8 illustrates the result of change of
frequency shift depending on air gap (d). It is found that the frequency shift decreases as the air gap (d) increases.
The modulation unit is mounted upon selecting the appropriate level of frequency shift depending on the air gap. The front Teflon (8), the high permittivity sheet (9), the Varactor diode mount (10) and the rear Teflon (11) are arranged in the order listed herein to construct the modulation unit. The usable frequency range is determined depending on the lengths of the front Teflon (8) and the rear Teflon (11).
Figure 9 is a graph that illustrates frequency range change depending on the length of the front Teflon (8) under the condition that the voltage is 5V, the thickness of the high permittivity sheet (9) is 0.135mm, the length of the rear Teflon (11) is 2.5mm and the air gap is 1.5mm. The graph shows that the usable frequency range decreases as the length of the front Teflon (8) increases.
Figure 10 is a graph that illustrates frequency range change depending on the length of the rear Teflon (11) under the condition that the voltage is 5V, the thickness of the high permittivity sheet is 0.135mm, the length of the front Teflon (8) is 1. 2mm and the air gap is 1. 5mm. The usable frequency range is determined over the width of lGHz corresponding to the length of the rear Teflon (11) around the usable frequency determined by the front Teflon (8).
The high permittivity sheet (9) is inserted for the impedance matching between the front Teflon (8) and the Varactor diode mount (10). The thickness of the high permittivity sheet in a preferred embodiment of the present invention is 0.135mm.
In Figure 7, the dielectric substrate (10) that has the permittivity of 2.56 and the thickness of 0.3mm is used and the Varactor diode named MA46H120 and manufactured by M/A Com is used. The gap between the metal thin films on the part
where the Varactor diode (17) is mounted is 0.3mm. Metal thin films having the gap of 0. lmm may be used as well.
Consequently, an FM transmitter in the 60GHz range is implemented with the above-described structures. Figure 11 is a graph that illustrates frequency change corresponding to voltage changes (0V, 5V, 10V) where the air gap is respectively 1. 2mm, 1. 3mm, 1. 4mm, 1. 5mm and 1. 6mm. As shown in the graph, the frequency change of the FM transmitter that has the air gap of 1. 5mm shows the highest linearity.
INDUSTRIAL APPLICABILITY As explained above, an FM transmitter may be downsized by providing an FM transmitter in the new shape according to the present invention and the mass production becomes possible because the fabrication process is made simple.
Also, the FM transmitter according to the present invention may be used widely in various application fields such as radar, broadcasting, etc. due to the small size and the improved linearity and output characteristics of the FM transmitter.