scispace - formally typeset
Search or ask a question

Showing papers on "Frequency drift published in 1996"


Patent
13 Aug 1996
TL;DR: In this paper, a synchronizing apparatus for a differential OFDM receiver that simultaneously adjusts the radio frequency and sample clock frequency using a voltage controlled crystal oscillator to generate a common reference frequency is presented.
Abstract: A synchronizing apparatus for a differential OFDM receiver that simultaneously adjust the radio frequency and sample clock frequency using a voltage controlled crystal oscillator to generate a common reference frequency. Timing errors are found by constellation rotation. Subcarrier signals are weighted by using complex multiplication to find the phase differentials and then the timing errors. The reference oscillator is adjusted using the timing errors. Slow frequency drift may be compensated using an integral of the timing error. Frequency offset is found using the time required for the timing offset to drift from one value to another.

138 citations


Journal ArticleDOI
TL;DR: In this paper, the inviscid frequency shift, due to nonlinearity, has been extracted from the damped oscillation data, using a central-averaging scheme, for the classical case of the oscillations of a free low-viscosity drop, it has been found that the frequency shift agrees well with the predictions of the nonlinear theory of Tsamopoulos & Brown.
Abstract: Oscillations of low-viscosity drops were studied in the microgravity environment of a Space shuttle flight. From the damped oscillation data, the inviscid frequency shift, due to nonlinearity, has been extracted using a central-averaging scheme. For the classical case of the oscillations of a free low-viscosity drop, it has been found that the frequency shift agrees well with the predictions of the inviscid nonlinear theory of Tsamopoulos & Brown (1983) for e < 0.3. But for the oscillations of a rotating low-viscosity drop, under acoustic levitation, the frequency shift is smaller, and the percentage of time spent in prolate displacement is significantly less than that for the classical case.

83 citations


Patent
17 Dec 1996
TL;DR: In this paper, a temperature compensation circuit for a crystal oscillator module (12) used in a communication device (200) is presented, where an existing microcontroller (210) of the communication device is used to provide temperature compensating digital data (30) for a single-input single-output (SISO) crystal oscillators.
Abstract: A temperature compensation circuit (10) for a crystal oscillator module (12) used in a communication device (200). An existing microcontroller (210) of the communication device (200) is used to provide temperature compensating digital data (30) for a crystal oscillator (18). In this way, the crystal oscillator module (12) does not require an on-board memory which substantially cuts costs. The temperature compensation digital data (30) is converted to a temperature compensation signal (22) in a digital-to-analog converter which controls the crystal oscillator frequency. However, typical digital-to-analog converters are driven by voltage regulators which vary over temperature. To solve this problem, the crystal oscillator module (12) includes an on-board voltage regulator (34) which supplies a characterized regulated voltage (36) to the digital-to-analog converter such that the temperature compensation signal (22) from the digital-to-analog converter is inherently corrected for voltage variations in the voltage regulator (34). This improves stability of the output frequency (20) from about 5 ppm to about 2 ppm.

72 citations


Patent
11 Jul 1996
TL;DR: In this article, the rate of phase change of a digital pulse train providing a frequency-modulated component of interrogation frequency for an atomic frequency standard can be varied, for example, by multiplexing a plurality of differently phased (delayed) pulse trains to vary the phase change in a digital interrogation frequency component.
Abstract: In the generation of frequency-modulated interrogation frequencies for atomic frequency standards, the modulation characteristics can be tailored to the frequency discrimination characteristics of a physics package. The rate of phase change of a digital pulse train providing a frequency-modulated component of interrogation frequency for an atomic frequency standard can be varied, for example, by multiplexing a plurality of differently phased (delayed) pulse trains to vary the rate of phase change in a digital interrogation frequency component, or by effecting phase delays and phase advances through the addition and subtraction of pulses of a digital interrogation frequency component. In addition, fine frequency and/or modulation depth control, which can overcome physics package frequency offsets, can be effected through the addition and/or subtraction of increments of phase to and/or from a digital frequency component of the interrogation frequency at a variable phase change frequency (or drop rate count) to provide variable rates of phase change in alternate half-cycles of the modulation frequency in the synthesis of a frequency-modulated interrogation signal.

71 citations


Patent
20 Jun 1996
TL;DR: In this article, a frequency-locked loop (FLL) with an oscillator whose output frequency controls the amount of charge provided by a switched feedback capacitor to a charge integrator whose output voltage controls the frequency of the oscillator is considered.
Abstract: A frequency locked loop (FLL) having an oscillator whose output frequency controls the amount of charge provided by a switched feedback capacitor to a charge integrator whose output voltage controls the frequency of the oscillator. A switched reference capacitor provides a charge to the charge integrator which is a function of a reference frequency, so that the oscillator output frequency is a function of a product of the reference frequency times a ratio of the capacitance of the reference capacitor to the capacitance of the feedback capacitor. Plural reference capacitors, each responsive to a respective reference frequency may be provided so that the oscillator output frequency can be related to the sums or differences of the reference frequencies, the ratios of capacitors, the ratio of the reference voltages or a fixed multiplication factor.

62 citations


Patent
17 Jun 1996
TL;DR: A ring oscillator comprising an odd number of inverters connected in a ring, and apparatus for driving the ring oscillators so that it oscillates at a frequency slightly less than its maximum oscillating frequency such that harmonics of the oscillating frequencies are suppressed.
Abstract: A ring oscillator comprising an odd number of inverters connected in a ring, and apparatus for driving the ring oscillator so that it oscillates at a frequency slightly less than its maximum oscillating frequency such that harmonics of the oscillating frequency are suppressed.

49 citations


Patent
Takaaki Kawakami1
27 Sep 1996
TL;DR: In this paper, a frequency detection circuit detects the frequency of a horizontal sync signal, and generates a mode switching signal corresponding to the detected frequency, and the oscillation modes of the voltage-controlled oscillator are switched in accordance with the frequency detection signal output from the frequency detector circuit.
Abstract: A frequency detection circuit detects the frequency of a horizontal sync signal, and generates a mode switching signal corresponding to the detected frequency. A voltage-controlled oscillator constituting a PLL circuit has a plurality of oscillation modes obtained by dividing a frequency equal to an integer multiple of the frequency of the horizontal sync signal into a plurality of frequency ranges, and oscillates signals in the respective frequency ranges in accordance with control voltages output from a filter. The oscillation modes of the voltage-controlled oscillator are switched in accordance with the mode switching signal output from the frequency detection circuit. In the voltage-controlled oscillator, since the frequency range in each oscillation mode is narrow, the oscillation gain can be suppressed low, and a deterioration in jitter characteristics can be prevented.

42 citations


Patent
Stephen F. Blazo1
06 Sep 1996
TL;DR: In this article, a phase-locked loop was proposed for generating an output having jitter and wander. But the phase detector was not included in the phase lock loop, and the phase summing node was not coupled with the phase detectors.
Abstract: A signal generator has a variable reference oscillator, a variable oscillator and a phase locked loop for generating an output having jitter and wander. The variable reference oscillator generates a reference having a varying phase offset over a first phase modulation frequency interval and a constant output over a second phase modulation frequency interval. The variable oscillator generates a constant output over the first phase modulation frequency interval and a variable output over the second phase modulation frequency interval. The phase locked loop includes a phase detector, a phase summing node and oscillator with the phase detector coupled to receive the outputs of the variable reference oscillator and the oscillator, and phase summing node coupled to receive the outputs of the variable oscillator and the phase detector. The output of the phase locked loop tracks the variable reference oscillator over the first phase modulation frequency interval and generates a phase modulated output in response to the variable output of the variable oscillator over the second phase modulation frequency interval.

38 citations


Patent
Spears John H1
10 May 1996
TL;DR: In this article, a reference oscillator (118) in a communication device (100) such as a radiotelephone is controlled by temperature compensating the reference oscillators (118), at the time of manufacture, characterizing data are stored in nonvolatile memory (128) in the communication device.
Abstract: A reference oscillator (118) in a communication device (100) such as a radiotelephone is controlled by temperature compensating the reference oscillator (118). At the time of manufacture, characterizing data are stored in non-volatile memory (128) in the communication device (100). When the communication device (100) is powered up, the characterizing data are read and used to provide an initial correction (206) to the output frequency of the reference oscillator (118). Subsequently, an automatic frequency control operation is performed using the RF signal received from a remote transmitter as a reference signal. A frequency correction is determined (214) in the form of a frequency step size and step direction. The output frequency of the reference oscillator is repeatedly stepped until frequency error is minimized.

37 citations


Patent
18 Apr 1996
TL;DR: In this paper, an optical comb generator is used to determine the frequency component of a test light source by means of a superheterodyne receiver, and the frequency comb of the comb generator may be displaced as a whole and/or have its spectral width modified.
Abstract: An optical frequency generator has an optical comb generator (1) with which because of optical non-linearities around a central frequency a plurality of sidebands may be generated whose frequency spacing is given by the sending frequency of a frequency sender (13) supplied to the comb generator (1) The central frequency is adjustably coupled by a superheterodyne unit (6) to the spectral component of a reference light source (8) By modifying the frequency difference between the reference light source (8) and the central frequency of the comb generator (1) and by modifying the sending frequency of the frequency sender (13), the frequency comb of the comb generator (1) may be displaced as a whole and/or have its spectral width modified The optical frequency generator is appropriately used to determine the frequency component of a test light source (15) by means of a superheterodyne receiver (17)

36 citations


Patent
15 Mar 1996
TL;DR: In this paper, a voltage controlled oscillator having substantial frequency dependence on a parallel RC timing element including a voltage-variable resistance element, such as a MOSFET biased in the triode region, can be connected to ground.
Abstract: A voltage controlled oscillator having substantial frequency dependence on a parallel RC timing element including a voltage-variable resistance element, such as a MOSFET biased in the triode region. One terminal of the timing element can be connected to ground. The voltage used to tune the timing element, to lock the voltage controlled oscillator to a reference frequency can be used to control similar timing elements integrated upon the same circuit, for example a continuous-time filter in an ethernet transceiver. The oscillator frequency is substantially independent of variations in supply voltage.

Patent
26 Apr 1996
TL;DR: In this paper, a temperature compensated piezoelectric transducer was used to compensate for the deviation of an oscillation frequency caused by a change of temperature, where the temperature was measured by a temperature detection unit and the parameter changes according to the surrounding temperature.
Abstract: A temperature compensated piezoelectric oscillator includes: an oscillation circuit that drives a piezoelectric element with a current; a direct-current-stopping fixed capacitor; a frequency-temperature compensated circuit that compensates the deviation of an oscillation frequency caused by a change of temperature; and a piezoelectric transducer which includes a piezoelectric element driven in a prescribed frequency; where the above elements are connected serially; wherein the frequency-temperature compensated circuit includes a temperature compensation voltage generation section which generates a voltage based on a parameter that is changed in a temperature detection unit, in which the parameter changes according to the surrounding temperature; wherein the temperature compensation voltage generation section includes: a low-temperature control voltage generation section which generates a voltage that compensates a temperature characteristic of the piezoelectric element in a low temperature, where "low" indicates temperatures lower than a common temperature in the temperature characteristic of the piezoelectric element; and a high-temperature control voltage generation section which generates a voltage that compensates the temperature characteristic of the piezoelectric element in a high temperature, where "high" indicates temperatures higher than a common temperature in the temperature characteristic of the piezoelectric element; wherein the low-temperature control voltage generation section includes: a low-temperature first-degree voltage generation circuit which generates the voltage that linearly changes with temperature; a low-temperature high-degree voltage generation circuit which generates the voltage that behaves like a high degree function in a low temperature state of the voltage generated by the low-temperature first-degree voltage generation circuit; and a low-temperature voltage composite circuit which synthesizes voltages generated by the low-temperature first-degree voltage generation circuit and the low-temperature high-degree voltage generation circuit; and wherein the high-temperature control voltage generation section includes: a high-temperature first-degree voltage generation circuit which generates the voltage that linearly changes with temperature; a high-temperature high-degree voltage generation circuit which generates the voltage that behaves like a high degree function in a high temperature state of the voltage generated by the high-temperature first-degree voltage generation circuit; and a high-temperature voltage composite circuit which synthesizes voltages generated by the high-temperature first-degree voltage generation circuit and the high-temperature high-degree voltage generation circuit.

Patent
05 Mar 1996
TL;DR: In this paper, a temperature compensation system includes a first oscillator to generate a number of pulses which vary from a desired frequency as a function of temperature, and a second oscillator at a corrective frequency which is greater than the desired frequency.
Abstract: A temperature compensation system includes a first oscillator to generate a number of pulses which vary from a desired frequency as a function of temperature of the first oscillator. The system also includes a second oscillator to generate digital pulses at a corrective frequency which is greater than the desired frequency. A sensor provides an temperature signal for the first oscillator. A digital memory has a digital error table addressable by a signal corresponding to the temperature signal to provide a number of pulse errors corresponding to temperature error for each of the number of pulses. Each pulse error is a function of the corrective frequency and a temperature versus frequency characteristic of the first oscillator. An accumulator receives each pulse error to generate a cumulative error corresponding to one of the number of pulses. A variable delay device counts a quantity of corrective pulses from second oscillator to provide a delayed output pulse in accordance with the desired frequency. The quantity of corrective pulses is a function of the cumulative error signal received from the accumulator. The converter, memory, accumulator and delay device may be part of a microcontroller.

Patent
16 Aug 1996
TL;DR: In this paper, a self-monitoring feature for stabilizing the cyclic frequency/time sweep pattern is proposed. But the method is inherently independent of drift caused by ageing or temperature.
Abstract: A radar ranging system using a continuous wave frequency modulated transmission characteristic for the measurement of aircraft altitude or inter-vehicular distances in traffic employs a voltage regulated oscillator (15) which transmits a linear sweep frequency beam conforming to the cyclic frequency/time pattern of Figure 2 via an antenna (10). Target echoes are received by the same antenna via the synchronised switch (11) and by registering frequency differences related to the time of signal travel at the frequency counter (22) of a quartz (25) regulated controller (20) the range is derived. The method is inherently independent of drift caused by ageing or temperature and has a self-monitoring feature for stabilising the frequency/time sweep pattern.

Patent
Wilbur David Pricer1
12 Sep 1996
TL;DR: In this paper, a relatively low frequency oscillator in junction with a much higher frequency oscillators is used to produce a clock that is both accurate and minimizes power consumption, where the output of the high-frequency oscillator is counted during its operation period, and the amount counted is accumulated for subsequent time periods.
Abstract: A relatively low frequency oscillator in junction with a much higher frequency oscillator is used to produce a clock that is both accurate and minimizes power consumption. The high frequency oscillator is enabled only during a small portion of the clock's operation and is used to gauge the output of the low frequency oscillator. The output of the high frequency oscillator is counted during its operation period, and the amount counted is accumulated for subsequent time periods. When the accumulated count reaches a predetermined value, a clock output is provided.

Patent
25 Oct 1996
TL;DR: In this paper, a computer determines the sign of the variation in the absolute value of the phase in the course of successive sampling cycles of predetermined duration and produces therefrom frequency correction signals for the oscillator.
Abstract: An oscillator supplies a signal of adjustable frequency to drive power ultrasonic actuators. The oscillator frequency is varied and the phase between the voltage and current of the signal is continuously measured. A computer determines the sign of the variation in the absolute value of the phase in the course of successive sampling cycles of predetermined duration and produces therefrom frequency correction signals for the oscillator. A frequency correction is applied to the oscillator in the same direction as the frequency correction applied previously if the variation in absolute value of the phase is negative, and in the opposite direction if the variation in absolute value of the phase is positive. If the variation in absolute value of the phase is zero, a frequency correction of random sign is applied to the oscillator.

Patent
16 Apr 1996
TL;DR: In this paper, a radio control device includes a transmitter, a receiver, and a frequency synthesizer system, in which a PLL, circuit for controlling an oscillation frequency depending on a phase difference between a reference signal and the frequency is used and includes a frequency selecting means for selecting a required frequency from a plurality of predetermined frequency data.
Abstract: A radio control device includes a transmitter, in which a crystal type high frequency module equipped with a high frequency circuit corresponding to a frequency band of a carrier and a PLL high frequency module equipped with the high frequency circuit and a PLL circuit for controlling a frequency of the carrier depending on a phase difference between the carrier and a reference signal of oscillator are detachably mounted. Such construction permits the crystal type high frequency module and PLL high frequency module to be selectively used as desired and transmission data to be output by means of the carrier of a desired frequency set depending on the high frequency module. Also, the radio control device includes a receiver which employs a frequency synthesizer system in which a PLL, circuit for controlling an oscillation frequency depending on a phase difference between a reference signal and the oscillation frequency is used and includes a frequency selecting means for selecting a required frequency from a plurality of predetermined frequency data and a frequency setting means for fixedly setting a receive frequency on the frequency selected by the frequency selecting means when a power supply is turned on.

Patent
23 Feb 1996
TL;DR: In this paper, a portable telephone with an oscillation circuit including a crystal resonator and a variable-capacitance diode is used to compensate for the output frequency drift caused by a temperature change.
Abstract: In a portable telephone which uses a CPU, a memory, a temperature sensor, a D/A converter, and an A/d converter as control elements, and which has an oscillation circuit including a crystal resonator and a variable-capacitance diode, temperature compensation of the output frequency is made by using these existing control elements. The memory is previously stored with control information for correcting an output frequency drift of the portable telephone caused by a temperature change. The temperature of the oscillation circuit is detected with the temperature sensor and converted into a digital value in the A/D converter. The CPU reads control information corresponding to the detected temperature from the memory and applies it to the variable-capacitance diode of the oscillation circuit through the D/A converter, thereby maintaining the output frequency at a constant level. Also disclosed is a method of efficiently calculating an oscillation frequency of a crystal resonator with a reduced number of points of measurement for a temperature characteristic of the crystal resonator. A method of accurately carrying out the above-described temperature compensation is also disclosed.

Journal ArticleDOI
TL;DR: In this article, a technique of frequency-hopping spread-spectrum modulation was proposed to reduce the spectral power density at harmonics of the switching frequency in switched-mode power converters (SMPCs).
Abstract: SummaryElectromagnetic compatibility (EMC) remains an issue which can present many problems to designers of high frequency power converter circuits. Usual techniques for alleviating the problems of interference generation by power converters involve the use of screening materials and filters, however, the effectiveness of such measures depends on the frequency the interference and the power density at each frequency of interest. As pulse width modulation (PWM) generates high frequency harmonics at multiples of the switching frequency, modulation of the switching frequency may be used to spread the spectral power density present at these harmonic frequencies. This paper presents a technique of frequency-hopping spread-spectrum modulation which may be applied to switched-mode power converters (SMPC’s) to reduce the spectral power density at harmonics of the switching frequency. The influence of the peak frequency deviation, the modulation sequence length and the type of modulating sequence on the resultant ...

Patent
18 Apr 1996
TL;DR: In this paper, a ring oscillator with a frequency stabilizing circuit produces compensated voltage signals in response to changes in supply voltage and temperature to modify the conductances of field effect transistors of the frequency stabilizer.
Abstract: An integrated circuit includes a ring oscillator with a frequency stabilizing circuit. The frequency stabilizing circuit produces compensated voltage signals in response to changes in supply voltage and temperature to modify the conductances of field-effect transistors of the frequency stabilizing circuit to compensate the conductive path of the discharge current of a capacitor from the ring oscillator in order to stabilize the oscillation frequency.

Journal ArticleDOI
TL;DR: In this paper, an active RC oscillator consisting of two cascaded CCII-based first-order all-pass networks with unity overall feedback is described, and the oscillation frequency may be controlled by means of one or two grounded capacitors.
Abstract: An active-RC oscillator which consists of two cascaded CCII-based first-order allpass networks with unity overall feedback is described. The oscillation frequency may be controlled by means of one or two grounded capacitors. Experimental results are reported which establish the relative merits of single- or dual-element control of frequency for this oscillator.

Patent
11 Mar 1996
TL;DR: In this article, an adaptive infinite impulse response (IIR) filter is provided that can adaptively detect the presence of one or more tones in its input stream, subject only to a limitation that such tones fall within a frequency band consistent with accepted sampling principles (e.g., a maximum frequency of interest no greater than one-half the sampling frequency).
Abstract: An adaptive Infinite Impulse Response (IIR) filter is provided that can adaptively detect the presence of one or more tones in its input stream. The tones to be detected may be of arbitrary frequency, subject only to a limitation that such tones fall within a frequency band consistent with accepted sampling principles (e.g., a maximum frequency of interest no greater than one-half the sampling frequency--Nyquist sampling criteria). An IIR filter developed according to the method of the invention will adaptively locate the frequencies of tones to be detected, thereby allowing for frequency drift from nominal expected frequency values with no loss in accuracy. Such a filter will also process the input signal sample-by-sample, thereby avoiding the blocking problem of FFT-based filter approaches. With the filter of the invention, an application can identify the frequencies, associated power levels, SNR and duration of the tones. Thus, such an application can use a simple user specified library of tone parameters to decide if tones of interest are present in the input stream.

Patent
Jr. Robert O. Conn1
30 Aug 1996
TL;DR: In this article, a method for measuring localized operating temperatures and voltages on an integrated circuit is described, where an oscillator circuit with a frequency that varies with temperature and/or applied voltage is used to establish a known relationship between oscillation frequency and temperature.
Abstract: A method is described for measuring localized operating temperatures and voltages on an integrated circuit. The integrated circuit includes an oscillator circuit with a frequency that varies with temperature and/or applied voltage. The frequency of the oscillator is then determined, using a constant voltage, for a number of temperatures to establish a known relationship between oscillation frequency and temperature. Once the relationship is known, a similar oscillator is included within or adjacent a second circuit of the integrated circuit. The operating temperature or operating voltage of the second circuit may then be determined by monitoring the frequency of the oscillator while the second circuit is operational.

Patent
Veijo Korhonen1, Tero Ojanpera1
15 Oct 1996
TL;DR: In this paper, the reference frequency is accurately set by incrementally scanning the signal channel until a signal of magnitude greater than a predetermined level is detected, whereupon the receiver locks onto the detected signal and instructs the oscillator to produce a reference frequency signal of a certain frequency according to the frequency of said detected signal.
Abstract: A receiver and a method of setting the frequency of the reference signal in the receiver, the receiver comprising a voltage controlled crystal oscillator which provides the reference frequency for a synthesizer. The synthesizer in turn produces the local oscillator frequency signal in the receiver. Temperature fluctuations in the crystal are compensated for by microprocessor control of the oscillator. The reference frequency is accurately set by incrementaly scanning the signal channel until a signal of magnitude greater than a predetermined level is detected, whereupon the receiver locks onto said detected signal and instructs the oscillator to produce a reference frequency signal of a certain frequency according to the frequency of said detected signal.

Patent
08 Jan 1996
TL;DR: In this paper, a modulation frequency setting device sets the modulation frequency on the basis of the vehicle speed data from a vehicle speed detector and the detected range data, causing a low-frequency oscillator to generate a low frequency signal of the set frequency.
Abstract: Modulation frequency setting device sets the modulation frequency on the basis of the vehicle speed data from a vehicle speed detector and the detected range data, causing a low frequency oscillator to generate a low frequency signal of the set frequency. A transmitter transmits an electromagnetic wave (e.g., infrared light) which have been modulated with the low frequency signal. A phase comparator detects the phase difference between the low frequency signal and a detector output, and a range operating device produces range data. Relative speed operating unit finds the relative speed based on the range data. In case of a high vehicle speed, the modulation frequency is set low to extend the detection range. If an object in a short distance is detected, the modulation frequency is set high to limit the detection range to a short range, thereby enhancing the range resolution.

Patent
Yoshifumi Horiuchi1
26 Mar 1996
TL;DR: In this paper, the phase arator circuit detects a phase difference between a second-interval reference pulse signal from a GPS receiver and an almost secondinterval pulse signal obtained by dividing output of a voltage-controlled oscillator with a counter circuit, and the voltage of the control signal is then changed to match the phases.
Abstract: An oscillator with higher frequency stability. The phase arator circuit 17 detects a phase difference between a second-interval reference pulse signal 16 outputted from a GPS receiver 15 and an almost second-interval pulse signal 14 obtained by dividing output of a voltage-controlled oscillator 11 with a counter circuit 13. The delay circuit 31 and the difference calculating circuit 32 determine changes in the phase difference every second, while the averaging circuit 35 determines the mean value of the changes. The control voltage is changed to decrease the mean value of the changes to first match the frequency of the pulse signal 14 with that of the reference pulse signal 16, and the voltage of the control signal at this moment is stored. The voltage of the control signal is then changed to match the phases. The voltage of the control signal is restored to the stored value when the phases match. Since the oscillation frequency is controlled based on the mean value of the changes in the phase difference, the long-term frequency stability of GPS signals is incorporated in the stability of the oscillation frequency of the voltage-controlled oscillator.

Patent
24 Jul 1996
TL;DR: In this paper, a temperature compensation apparatus for an oscillator includes an output having an output for generating a clock signal with a frequency identical to the oscillating frequency of the oscillator, a memory for storing a frequency compensation lookup table based on the relationship between output frequencies of oscillator and the environmental temperature variations.
Abstract: A temperature compensation apparatus for an oscillator includes an oscillator having an output for generating a clock signal with a frequency identical to the oscillating frequency of the oscillator, a memory for storing a frequency compensation lookup table based on the relationship between output frequencies of the oscillator and the environmental temperature variations, a temperature detector for detecting the environmental temperature variations, a central processing unit for selecting a rating output frequency of the oscillator, acquiring a frequency compensation value from the frequency compensation lookup table stored in the memory in response to a detected environmental temperature, and converting the frequency compensation value into a corresponding compensation signal, and a compensation circuit receiving an output signal of the oscillator and a compensation signal from the CPU for compensating a deviation between the output frequency of the oscillator and the rating frequency and outputting a frequency signal close to the rating frequency of the oscillator.

Patent
27 Jun 1996
TL;DR: In this paper, a stabilization process for the local oscillator frequency in wide-band tunable DROs employed in receivers of a digital microwave radio link is described, where a microprocessor, already provided for normal operation control, cyclically reads the control voltage of a VCO inserted in a PLL which reconstructs an intermediate frequency carrier used to coherently demodulate the received signal.
Abstract: There is described a stabilization process for the local oscillator frequency in wide-band tunable DROs employed in receivers of a digital microwave radio link. A microprocessor, already provided for normal operation control, cyclically reads the control voltage of a VCO inserted in a PLL which reconstructs an intermediate frequency carrier used to coherently demodulate the received signal. The voltage read is compared with an optimal reference value by taking an error signal which controls a varicap diode of the DRO for tuning correction. With each reading, the optimal value can be modified on the basis of temperature data supplied by a heat sensor to cancel the effect of temperature on the reference.

Patent
28 Sep 1996
TL;DR: In this article, a phase-regulated oscillator is coupled to a phase detector via a frequency divider with a whole number division ratio (N) and an output frequency is provided which is compared in phase with a reference frequency.
Abstract: The frequency synthesiser includes a phase-regulated oscillator (1), coupled to a phase detector (2) via a frequency divider (3) with a whole number division ratio (N). An output frequency (fi) is provided which is compared in phase with a reference frequency (fr), the feedback loop between the output of the phase detector and the control input of the oscillator contains a loop filter (4). The frequency divider division ratio is determined by a control circuit (7), with periodic switching of the division ratio for minimising phase noise in the oscillator output signal (fo). The control circuit output signal is obtained by adding a whole number component (P) of the division ratio to a supplementary component. The component is provided by a chain circuit with a number of integrators with feedback weighting components, for simulating a fractional division ratio.

Patent
Joachim Hauk1
02 Oct 1996
TL;DR: In this article, a method and an arrangement for frequency modulation of a high-frequency signal, where the highfrequency signal is generated with an oscillator which is controlled by comparison of an actual frequency signal with a variable set frequency signal, is presented.
Abstract: In a method and an arrangement for frequency modulation of a high-frequency signal, where the high-frequency signal is generated with an oscillator which is controlled by comparison of an actual frequency signal with a variable set frequency signal, the actual frequency signal contains pulses with an average repetition frequency which corresponds to an actual frequency, with one pulse being derived from one edge of the high-frequency signal and its phase angle being determined by a predetermined clock pulse. The set frequency signal comprises pulses with an average repetition frequency which corresponds to a set frequency. The pulses increment or decrement an up/down counter from whose count a control voltage is derived for the oscillator.