Boots – shoes – and leggings
Patent
1995-06-07
1998-02-17
Voeltz, Emanuel T.
Boots, shoes, and leggings
364485, 364557, 331158, 331176, H03B 532, H03L 100
Patent
active
057197822
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a frequency measuring apparatus for measuring the frequency of a signal with high accuracy using a crystal oscillator as a reference frequency source, and more specifically to a frequency measuring apparatus and a frequency measuring method wherein there are entirely eliminated the need of high-degree techniques and much labor in manufacture, adjustment, and inspection of conventional crystal oscillators and wherein the accuracy of the measurement is further improved, and further wherein the cost of manufacture of the apparatus is sharply reduced and the apparatus is miniaturized.
2. Description of the Prior Art
An apparatus for measuring the frequency of a signal generally requires a reference frequency source. Such reference frequency sources include the so-called temperature compensated crystal oscillator (TCXO) for the accuracy of measurement up to .+-.1 ppm, and the so-called oven-controlled highly stabilized crystal oscillator (OCXO) when further higher accuracy is required. These oscillators are manufactured as oscillator units by those skilled in the art. Such an oscillator unit satisfies requirements for the reference frequency source as its unit.
More specifically, the requirements are such that an absolute frequency is ensured at the center of a variable width, that an associated frequency is variable within a predetermined width with use of a variable capacitor in order to moderate a change with the lapse of time in the associated frequency, and that a change in an output frequency falls within a predetermined deviation with respect to environmental changes such as changes with the lapse of time, and in temperature and a power supply.
Manufacturers in this field conventionally design, manufacture, inspect, and ship such oscillators so as to satisfy these requirements. In other words, TCXO and OCXO as conventional reference oscillators require a high-degree technique and labor which can not be dealt with by persons other than those skilled in the art to result in the high cost where a cost rate of a reference oscillator to that of a frequency measuring apparatus including the reference oscillator is increased.
The following is an example of the aforementioned high-degree technique and labor upon manufacturing the Tcxo and Ocxo.
In a required temperature range there is necessary a monotonically decreasing temperature characteristic for a frequency before compensation, so that the frequency is needed to be variable over .+-.15 ppm in a temperature range of from 0.degree. to 70.degree. C. for example. In addition to this requirement a frequency variation of about .+-.5 ppm using a variable capacitor, etc., is required for moderating a change with the lapse of time, and further a function to moderate manufacturing tolerance of a crystal oscillator, say .+-.10 ppm is required. Possibilities of so much frequency variations mean that there must also additionally be taken into consideration frequency variations caused by changes with the lapse of time and temperature changes of circuit components constituting a reactance network for varying an associated frequency.
This in turn causes severe variations of load capacitance viewed from a crystal oscillator which further cause a change in the conditions of an oscillator loop and result in variations of oscillation redundancy and of an output level.
The variations of load capacitance to moderate the change with the lapse of time in an oscillation frequency are equivalent to shifting of the angle of cutting of a crystal and result in a change in the temperature compensation characteristic.
There is further a limitation to the crystal oscillator that a capacitance ratio (a ratio between parallel capacitance and equivalent series resonance circuit capacitance) of the quartz oscillator should be lower, in order for the crystal oscillator to have a required frequency varying function.
The conventional technique suffers from a difficulty of its not ensuring stable oscillation
REFERENCES:
patent: 4297657 (1981-10-01), Frerking
patent: 4380745 (1983-04-01), Barlow et al.
patent: 4513259 (1985-04-01), Frerking
patent: 4611181 (1986-09-01), Fukumura
patent: 4893097 (1990-01-01), Zwack
patent: 4949055 (1990-08-01), Leitl
patent: 5126699 (1992-06-01), Kabler
patent: 5319324 (1994-06-01), Satoh et al.
patent: 5392005 (1995-02-01), Bortolini et al.
Bui Bryan
Toyo Communication Equipment Co., Ltd.
Voeltz Emanuel T.
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