Electrical resistors – With inductance-reducing
Patent
1990-10-02
1992-09-29
Lateef, Marvin M.
Electrical resistors
With inductance-reducing
338 60, 333 22R, H01C 302
Patent
active
051516764
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a terminator utilizing a film resistance. In more detail, the present invention particularly relates to a structure of resistive terminator which is to be used in the microwave frequency band and is constituted through use of microstrip line and film resistance.
BACKGROUND ART
A film resistance terminator is used for terminating the line by absorbing an energy propagated on the transmission line without reflection. In this case, absorbed energy is converted to heat. Namely, the film resistance terminator never reflects an input signal and is used, for example, to absorb the signal as a terminator of a hybrid circuit, etc.
A structure of an example of the conventional film resistance terminator is shown in FIG. 1 and FIG. 2. FIG. 1 is a plan view of a film resistance terminator, while FIG. 2 is a sectional view along the line Y-Y' in FIG. 1. In this figure, the numeral 10 designates a dielectric material substrate; 11, a conductor film; 12, a grounding conductor; 13, a first microstrip line; 14, a second microstrip line; 15, a conductor ribbon; 30, a film resistance consisting of a thin or thick film such as a tantalum nitride.
A structure of the film resistance will then be explained. A flat area is formed as a step-down area at a part of the grounding conductor 12. On this flat area, the dielectric material substrate 10 covered with the conductor film 11 at the rear surface thereof is mounted. Moreover, a first microstrip line 13 as a signal input part, a film resistor 30 which becomes a termination resistor connected to the first microstrip line 13 and a second microstrip line 14 for grounding the film resistor 30 are formed on the dielectric material substrate 10. In this case, the second microstrip line 14 is arranged at the end part of dielectric material substrate 10 and is almost flat for the upper step surface of the grounding conductor 12. Moreover, the conductor film 11 at the rear surface of the dielectric material substrate 10 is provided in close contact with the flat area of the grounding conductor 12. In addition, the conductor ribbon 15 is formed to electrically connect the second microstrip line 14 and the grounding conductor 12. Regarding the characteristic and size of each element, for example, the dielectric material substrate 10 is formed by alumina ceramics having the curve A, dielectric constant of 9.8 and thickness of 0.38 mm. The microstrip lines 13, 14 are formed by the conductor in the width of 0.36 mm and thickness of 0.003 mm, while the second microstrip line 14 has the length of 0.1 mm. The film resistor 30 has the width of 0.3 mm and length of 0.3 mm.
In this structure, for functioning as a terminator, the characteristic impedance of the first microstrip line is set equal to a DC resistance value of the film resistor for impedance matching. In this case, the characteristic impedance of first microstrip line is set to 50 ohms and therefore, a DC resistance of film resistor 30 is also set to 50 ohms which is equal to such characteristic impedance. With such structure, the input signal is terminated.
A return loss at the conventional film resistance terminator described above, namley a rate of appearance of reflected wave for the input signal is by the curve A in FIG. 3. This graph indicates a result of calculation for obtaining a return loss through the simulation by inputting sizes of respective parts of the film resistance terminator and then changing the frequency of input signal.
As will be understood from the graph of FIG. 3, the structure of conventional film resistor provides a good return loss in the comparatively low frequency band but shows deterioration of return loss for higher frequency band.
Next, a cause of deterioration of return loss in such a higher frequency band will be discussed. A film resistor which is easily influenced by the frequency can be thought as a cause. Therefore, a method of obtaining an input impedance of transmission path which results in load termination as shown in FIG. 4 will be i
REFERENCES:
patent: 4413241 (1983-11-01), Bitoune et al.
Fujitsu Limited
Lateef Marvin M.
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