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Showing papers on "Voltage-controlled oscillator published in 1986"


Patent
28 Aug 1986
TL;DR: In this article, a digitally temperature compensated oscillator (TCO) system is provided which is capable of ascertaining and memorizing in an EEPROM-based look-up table, appropriate digital values of a temperature-compensating tuning voltage to the TCO during calibration.
Abstract: A digitally temperature compensated oscillator (TCO) system is provided which is capable of ascertaining and memorizing in an EEPROM-based look-up table, appropriate digital values of a temperature-compensating tuning voltage to the TCO during calibration. An on-board temperature sensing mechanism tracks variations in temperature in the TCO and produces an analog voltage value corresponding to the instantaneous temperature. The voltage value of the sensor output is digitized and designated to constitute an address into the EEPROM based look-up table. As the temperature changes, the digitized output of the temperature sensor and hence the address to the EEPROM changes accordingly. The TCO tuning voltage value corresponding to the address represented by the measured temperature is extracted from the values stored within the EEPROM table and then converted into a corresponding analog voltage which is used to drive the voltage-controlled oscillator (VCO) in order to maintain the output frequency of the TCO stabilized at a desired value. The EEPROM contained within the TCO is preferably calibrated during production, under the control of a calibration and test circuit which regulates the calibration and testing of a TCO in a chamber whose temperature is ramped over a desired temperature range. The TCO includes an on-board microprocessor which allows integration of several of the TCO functions, including the analog-to-digital and the storage and retrieval of data to and from the EEPROM containing the look-up table and extremely simplifies the calibration and test procedure.

103 citations


Patent
21 Feb 1986
TL;DR: In this article, a fractional N synthesizer comprising a voltage controlled oscillator for producing an output signal which is afforded to a phase detector via a variable divider to provide a control signal for the oscillator in the presence of a phase difference between a reference signal from a reference source and the signal afforded from the variable dividers.
Abstract: A fractional N synthesizer comprising a voltage controlled oscillator for producing an output signal which is afforded to a phase detector via a variable divider to provide a control signal for the voltage controlled oscillator in the presence of a phase difference between a reference signal from a reference source and the signal afforded thereto from the variable divider wherein the synthesizer is provided with first and second accumulators, the arrangement of the accumulators being such that an output signal from the arrangement is provided in which the interpolation sidebands of the first accumulator caused by quantization errors in the first accumulator are cancelled, means being provided for setting the division ratio of the variable divider in dependence upon the output signal.

58 citations


Patent
29 Sep 1986
TL;DR: In this article, a voltage controlled oscillator is tuned with a network comprising two varactor diodes and two transmission lines, and the overall reactance of the network is such that, when a varactor tuning voltage is varied, the output frequency of the voltage-controlled oscillator will vary in an fashion with respect to the tuning voltage.
Abstract: A voltage controlled oscillator is tuned with a network comprising two varactor diodes and two transmission lines. By selecting appropriate values of varactor capacitance and transmission line length and width the overall reactance of the network is such that, when a varactor tuning voltage is varied, the output frequency of the voltage controlled oscillator will vary in an fashion with respect to the tuning voltage. Such a voltage controlled oscillator is gain compensated and exhibits a controlled modulation sensitivity over a range of frequencies. If the required frequency range of the oscillator is known beforehand, an alternate embodiment of the invention may be employed in which one of the varactor diodes is replaced with a fixed capacitor having a suitable value for the desired frequency range.

57 citations


Patent
31 Oct 1986
TL;DR: In this article, the reference oscillator (21) is controlled in closed loop manner through use of a phase-locked loop that responds, in part, to the lock frequency of the FM detector phase locked loop.
Abstract: A reference oscillator (21) suitable for use in a radio transceiver having a phase locked loop FM detector (12). During normal reception operation, the reference oscillator (21) can be controlled in closed loop manner through use of a phase locked loop that responds, in part, to the lock frequency of the FM detector phase locked loop. During transmit functions, or during other periods when the closed loop control may not provide accurate reference oscillator (21) operation, open loop control can be provided instead. Open loop control includes use of a stored value that reflects a most recent reliable value of an appropriate input control signal for the reference oscillator (21).

52 citations


Patent
23 Oct 1986
TL;DR: In this article, a phase difference between clock signals respectively fed to a reference frequency divider and to a frequency dividers for dividing the output frequency of a voltage-controlled oscillator becomes substantially zero, and two frequency dividers are initialized when the above-mentioned point in time is detected after turning on of the electric power source.
Abstract: In an intermittently operative phase-locked loop, in order to prevent the oscillator frequency from significantly changing at the time of turning on of an electric power source, a point in time at which a phase difference between clock signals respectively fed to a reference frequency divider and to a frequency divider for dividing the output frequency of a voltage-controlled oscillator becomes substantially zero is detected, and the two frequency dividers are initialized when the above-mentioned point in time is detected after turning on of the electric power source.

44 citations


Patent
Joseph P. Heck1
30 Sep 1986
TL;DR: In this paper, an improved frequency modulator was proposed for use in phase-locked loop (PLL) frequency synthesizers, which makes possible high deviation, low distortion, FM signals for a wide range of modulating signals, such as digital data or low frequency tone modulation.
Abstract: An improved frequency modulator apparatus for use in phase-locked loop (PLL) frequency synthesizers is disclosed which makes possible high deviation, low distortion, FM signals for a wide range of modulating signals, such as digital data or low frequency tone modulation. In a first embodiment having the improved frequency modulator, this apparatus advantageously injects the modulation signal into two ports, one at the VCO and the other provided in an unmodulated reference source signal chain. By properly balancing the levels into each of these two ports, a cancellation effect occurs which nulls the modulation signal at the output of the phase detector. In a second embodiment, the improved frequency modulator is incorporated in a PLL frequency synthesizer with an offset mixer to achieve relatively wide percentage deviation at a low frequency RF carrier. In a third embodiment, the improved frequency modulator is incorporated in a PLL synthesizer in its feedback loop so as to cancel the modulation components before they reach the phase detector. Thus, in the first two embodiments, the added phase modulator is inserted in the reference source signal path to the phase detector, while in the alternate third embodiment, the phase modulator is inserted into the feedback path and includes a phase inverter stage to correct for the inherent modulation polarity reversal.

44 citations


Patent
21 Jul 1986
TL;DR: In this paper, a method for calibrating an adjustable frequency generator having a voltage-controlled oscillator which is preceded by a computer via a digital-to-analog converter is described.
Abstract: A method for calibrating an adjustable frequency generator having a voltage-controlled oscillator which is preceded by a computer via a digital-to-analog converter. The control input of the oscillator is coupled to a calibrating device comprising a series circuit comprising a digital phase detector and a lowpass filter forming a phase-locked loop circuit arrangement. By the computer, a digital-to-analog converter is caused, upon a frequency reference value signal, to deliver a control voltage to the oscillator which corresponds to the output voltage of the lowpass filter prior to the start of the calibrating process. A digital value corresponding to the control voltage is stored in the computer together with a digital reference value corresponding to the given frequency.

42 citations


Patent
25 Jul 1986
TL;DR: In this paper, an improved gas density transducer which compares the resonant frequency of an enclosed, reference tuning fork crystal oscillator with the frequency of a detector tuning fork oscillator exposed to the surrounding gas is presented.
Abstract: An improved gas density transducer which compares the resonant frequency of an enclosed, reference tuning fork crystal oscillator with the resonant frequency of a detector tuning fork crystal oscillator exposed to the surrounding gas. The frequency of oscillation of the detector crystal oscillator exposed will vary in accordance with the gas density because of the motional resistance of the gas to vibrations of the tuning fork oscillator. The frequency of the detector oscillator can be compared to the frequency of the reference oscillator to determine the gas density.

38 citations


Patent
06 Jan 1986
TL;DR: In this paper, a variable capacitance circuit is used in a voltage controlled oscillator of a frequency synthesizer for providing extended frequency range, where a voltage multiplier circuit connected to a voltage divider network is used for supplying the plurality of voltages.
Abstract: A variable capacitance circuit includes a varactor having an anode side and a cathode side. A first variable bias voltage is applied to one of the sides and one of a plurality of voltages is applied as a second bias voltage to the other side for controlling the capacitance of the varactor. A voltage multiplier circuit connected to a voltage divider network is used for supplying the plurality of voltages. A decoder is responsive to input signals for selecting and applying one of the multiple voltage outputs. The variable capacitance circuit is used in a voltage controlled oscillator of a frequency synthesizer for providing extended frequency range.

37 citations


Journal ArticleDOI
TL;DR: In this paper, a ring oscillator intended for a 1?m NMOS monolithic IC implementation is presented. But the circuit displays a variable frequency from 1.5 GHz to 2.5GHz, and requires no off-chip tuning elements.
Abstract: Designs for ring oscillators that provide a 2:1 range of voltage-controllable frequency are compared. Simulated results are given for a ring oscillator intended for a 1 ?m NMOS monolithic IC implementation. The circuit displays a variable frequency from 1.5 GHz to 2.5 GHz, and requires no off-chip tuning elements.

36 citations


Patent
03 Feb 1986
TL;DR: In this paper, a voltage controlled oscillator (VCO) is stabilized against variations in output frequency resulting from changes in temperature or the power supply voltage by trimming the VCO from a second master VCO which is connected into a phase lock loop.
Abstract: A voltage controlled oscillator (VCO) is stabilized against variations in output frequency resulting from changes in temperature or the power supply voltage by trimming the voltage controlled oscillator from a second master VCO which is connected into a phase lock loop. Each of the two voltage controlled oscillators has an output frequency which is a function of two inputs. The signal input to one control input of each of the VCO's is the output of the low pass filter in the phase lock loop. The VCO's may both be implemented by cross-coupled NOR gates with grounded capacitor inputs.

Patent
31 Dec 1986
TL;DR: In this article, a burst mode communication receiver is phase-locked to a local frequency reference prior to data being received, and a reference timing preamble transmitted prior to the data is filtered and fed to the VCO causing it to injection lock such that the VCS becomes phase aligned with the preamle. The VCS is then permitted to free run during data transmission and continues to operate at substantially the same frequency.
Abstract: A timing recovery apparatus for a burst mode communication receiver. The apparatus provides for optimum sampling and digitizing of received data at a plurality of data rates. In particular, a VCO is phase-locked to a local frequency reference prior to data being received. A reference timing preamble transmitted prior to the data is filtered and fed to the VCO causing it to injection lock such that the VCO becomes phase aligned with the preamble. The VCO is then permitted to "free run" during data transmission and continues to operate at substantially the same frequency. A synchronous divider and multiplexer, responsive to the VCO, allows selection of sampling clocks for the plurality of data rates. The divider is forced to a known state during VCO injection locking, to assure that the sampling clocks have maintained the proper phase for optimal sampling at the corresponding data rate. Further, means is provided to monitor the frequency of the VCO. Should the VCO frequency drift more than a predetermined amount an indication of such is produced.

Journal ArticleDOI
TL;DR: A new method of microwave oscillator phase locking is accomplished by modulation of the electron beam before it reaches the cavity oscillator, which provides the coherence required of rf sources for linear accelerators and may enhance gyrotron performance for fusion heating.
Abstract: A new method of microwave oscillator phase locking, exploiting the extended nature of the gyroklystron configuration, is accomplished by modulation of the electron beam before it reaches the cavity oscillator. The amount of power required to give phase locking in a gyrotron is decreased by more than an order of magnitude from that predicted by Adler's theory. In addition, oscillator priming is observed at drive powers far below all other systems tested to date. These new methods provide the coherence required of rf sources for linear accelerators and may enhance gyrotron performance for fusion heating.

Patent
08 Aug 1986
TL;DR: In this article, a digital-to-analog converter receives the digital control voltage command and converts it to an analog control voltage signal which is fed to the VCO, and the resulting VCO output signal, at frequency, f out, is compared in a frequency counter with a reference frequency f R.
Abstract: Rapid frequency synthesizer apparatus, particularly for use in high speed frequency hooping systems, includes a voltage controlled oscillator (VCO) and a memory in which are stored digital control voltage commands corresponding to the various frequencies to be synthesized by the VCO. A controller, responsive to channel selection commands, addresses the memory and causes the corresponding digital control voltage command to be generated. A digital-to-analog converter receives the digital control voltage command and converts it to an analog control voltage signal which is fed to the VCO. The resulting VCO output signal, at frequency, f out , is compared in a frequency counter with a reference frequency f R . The controller controls operation of the frequency counter so that a difference between the actual synthesized frequency and the programmed frequency is determined. Responsive to this difference, the controller causes the addressed control voltage command to be modified in a manner designed to reduce the difference the next time the same programmed frequency is selected. A corresponding method for providing rapid frequency synthesis is described.

Patent
25 Jul 1986
TL;DR: In this paper, a radio frequency (r-f) transmitter has an electric oscillator circuit for producing an oscillating r-f signal in an antenna, which includes a feedback sub-circuit with a surface acoustic wave (SAW) resonator for stabilizing the oscillations.
Abstract: A radio frequency (r-f) transmitter has an electric oscillator circuit for producing an oscillating r-f signal in an antenna. A feedback sub-circuit of the oscillator circuit includes a surface acoustic wave (SAW) resonator for stabilizing the oscillations. The feedback circuit has a Q of less than 12000. There is a modulation sub-circuit of the oscillator circuit which includes a voltage variable capacitor. The voltage variable capacitor responds to input voltage variations to modulate the capacitance of the feedback circuit, thereby modulating the frequency of the transmitter. A garage door opener system employing the transmitter is also disclosed.

Patent
21 Feb 1986
TL;DR: In this paper, a frequency synthesizer of the fractional N type comprising a voltage controlled oscillator for producing an output signal which is afforded to a phase detector via a variable divider to provide a control signal for the oscillator in the presence of a phase difference between a reference signal from a reference source and the signal afforded from the variable dividers.
Abstract: A frequency synthesizer of the fractional N type comprising a voltage controlled oscillator for producing an output signal which is afforded to a phase detector via a variable divider to provide a control signal for the voltage controlled oscillator in the presence of a phase difference between a reference signal from a reference source and the signal afforded thereto from the variable divider wherein the division ratio of the variable divider is set in dependence upon the output of an interpolator arrangement comprising combiner means for receiving a digital input, digital controller means for receiving an output from the combiner means, digital slicer means for receiving an output from the digital controller means, feedback means for affording the output of the digital slicer means to a component for varying the division ratio of the variable divider.

Patent
25 Aug 1986
TL;DR: In this paper, a summing circuit is combined with a comparator and provided with inputs that accommodate differential sum/difference inputs, an error input and a ramp input from the oscillator or other source.
Abstract: A circuit for pulse width modulating the output of a voltage controlled oscillator without introducing any ocillator frequency or amplitude (slope) modulation. A summing circuit is combined with a comparator and provided with inputs that accommodate differential sum/difference inputs, an error input and a ramp input from the oscillator or other source. The ramp and error signals are combined differentially to pulse width modulate the comparator output and pulse width modulation can also be achieved by via the sum/difference inputs a differential relationship.

Patent
Haine John Leslie1
29 Jul 1986
TL;DR: A phase-locked digital synthesizer as mentioned in this paper comprises a voltage-controlled oscillator (6) supplying a frequency divider (7) the output of which is fed to a phase-sensitive detector (9) also receiving an input from a reference oscillator.
Abstract: A phase-locked digital synthesiser comprises a voltage-­controlled oscillator (6) supplying a frequency divider (7) the output of which is fed to a phase-sensitive detector (9) also receiving an input from a reference oscillator (10). The output of the detector (9) is fed back by a feedback loop to the voltage-controlled oscillator (6) to achieve phase-locking. The divider (7) receives an input from a logic circuit (8) to control the division ratio of the divider (7), the logic circuit being prompted by a control signal which is also used to select one of a plurality of loop filters (12,13) connected for selectable use in the feedback loop from the detector (9) to the voltage controlled oscillator (6), the selected loop filter being appropriate to the prompted division ratio. Other embodiments include compensating means to correct a loop phase error arising from a change in the division ratio.

Patent
Yoshida Yasuharu1
07 Jul 1986
TL;DR: In this article, a phase-locked regenerative circuit with a low-pass filter, a voltage-controlled oscillator, and a phase comparator is presented, where the output of the oscillator is sampled by a flip-flop for sending an output signal to the VCO through the lowpass filter.
Abstract: In a digital transmission system, a clock regeneration circuit includes a phase-locked loop having a low-pass filter, a voltage-controlled oscillator connected thereto, and a phase comparator for supplying to the low-pass filter a signal representative of the phase difference between an incoming two-level data bit stream and the output of the voltage-controlled oscillator. The incoming data bit stream is converted into a plurality of parallel data bit streams and fed to a multi-level quadrature amplitude modulator in response to a clock signal derived from the output of the voltage-controlled oscillator and converted into an outgoing multi-level digital signal. An incoming CMI (coded mark inversion) coded binary signal is sampled by a flip-flop for in response to the output of the voltage-controlled oscillator to supply an output signal to the VCO through the low-pass filter.

Patent
30 May 1986
TL;DR: In this article, a phase comparator determines the phase of the vector sum of the two color information signals and compares this against a desired phase value to generate a phase difference signal, which is then filtered and applied to a digital-to-analog converter which provides the frequency control signal for the analog voltage controlled oscillator.
Abstract: A digital television receiver, having a line-locked clock, includes a partly digital, partly analog phase locked loop. This phase locked loop regenerates two quadrature phase related subcarrier signals that are used to synchronously demodulate the chrominance signal components of the composite video signals into two color informaiton signals. The phase locked loop includes an analog voltage controlled oscillator which generates a signal that is independent of any frequency instability in the line locked clock signal. An analog-to-digital converter digitizes this signal to provide one of the subcarrier signals. This subcarrier signal is applied to a read-only memory to generate the second subcarrier signal. The two color information signals are obtained by multiplying the chrominance signals by the first and second subcarrier signals. A phase comparator determines the phase of the vector sum of the two color information signals and compares this against a desired phase value to generate a phase difference signal. The phase difference signal is filtered and applied to a digital-to-analog converter which provides the frequency control signal for the analog voltage controlled oscillator. In a second embodiment of the invention, a tracking filter is inserted at the output port of the analog-to-digital converter to allow the quantization resolution of the analog-to-digital to be reduced without affecting the performance of the phase locked loop.

Patent
18 Nov 1986
TL;DR: In this article, a PWM-FM control method and circuit is employed to control the output level of a resonant switch-mode inverter/converter, which is controlled via a nonlinear function shaper and VCO or ICO by the same voltage which controls the pulsewidth such that the turn-on of the controlled switching element(s) always occur(s).
Abstract: A PWM-FM control method and circuit is employed to control the output level of a resonant switch-mode inverter/converter. The frequency of the inverter/converter is controlled via a nonlinear function shaper and VCO or ICO by the same voltage which controls the pulse-width such that the turn-on of the controlled switching element(s) always occur(s) at substantially zero voltage and substantially zero current across the switching element(s), thereby minimizing switching losses and maximizing efficiency.

Patent
22 Oct 1986
TL;DR: In this article, a multiphase sinusoidal output signal (A',B',C') having a predetermined phase relationship to a multi-phase source signal was provided. But the phase relationship was not defined.
Abstract: A circuit for providing a multiphase digitally synthesized sinusoidal output signal (A',B',C') having a predetermined phase relationship to a multiphase source signal (A,B,C). The circuit comprises a phase comparator (12, 14, 16, 22), a voltage controlled oscillator (30) and a synthesizer (34). The voltage controlled oscillator produces an output frequency representative of the phase error. The variable frequency output is used for shifting the phase of the synthesized output signal in response to the phase error output signal of the phase comparator. The synthesizer digitally synthesizes at a predetermined amplitude the multiphase sinusoidal output signal. In an alternate embodiment, a second synthesizer is provided for producing a second multiphase synthesized output signal.

Patent
Hideo Miyashita1, Shigeo Yoshihara1
07 May 1986
TL;DR: In this article, a phase comparator adapted to produce a voltage representative of a difference in phase between outputs of a variable and a fixed frequency dividers is applied through a switch and a low pass filter to a voltage controlled oscillator.
Abstract: A frequency synthesizer applicable to a radio communication equipment includes a phase comparator adapted to produce a voltage representative of a difference in phase between outputs of a variable and a fixed frequency dividers. The output of the phase comparator is applied through a switch and a low pass filter to a voltage controlled oscillator. A reset circuit produces a reset signal interlocked with a power source of the synthesizer. The variable and the fixed frequency dividers are reset by the reset signal while the switch is closed after the generation of the reset signal and opened upon turn-off of the power source.

Patent
02 May 1986
TL;DR: In this article, a portable animal control unit includes circuitry incorporated in a miniature housing for generating an animal influencing modulated soundwave in the ultrasonic frequency range, the modulation rate was determined by the center frequency of the second oscillator output signal.
Abstract: A portable animal control unit includes circuitry incorporated in a miniature housing for generating an animal influencing modulated soundwave in the ultrasonic frequency range A first oscillator produces an output signal for driving an ultrasonic transducer, the output signal having a center frequency in the ultrasonic range A second oscillator produces an output control signal for modulating the frequency of the first oscillator, the modulation rate being determined by the center frequency of the second oscillator output signal and the amount of deviation of the second oscillator from the center frequency

Patent
25 Jun 1986
TL;DR: In this article, an apparatus for breaking the periodicity of the pseudorandom bit stream output from a linear sequence generator is described. But it does not specify the multiplexing selection criterion.
Abstract: An apparatus for breaking the periodicity of the pseudorandom bit stream output from a linear sequence generator. The apparatus includes a ring oscillator which periodically corrupts the sequence of the generator. The level of the supply voltage applied to the logic elements of the ring oscillator is varied over time, thereby altering the oscillator output frequency. In a second embodiment, the temperature of the logic elements of the ring oscillator is varied over time, thereby also altering the oscillator output frequency. A system comprising four of the above-disclosed apparatus having different linear sequences and different corrupting influences, are multiplexed, wherein the multiplexing selection criterion is determined by a logical combination of the four linear sequences.

Patent
Tatsuru Kojima1, Yukio Fukumura1
26 Jun 1986
TL;DR: In this article, a phase locked loop frequency synthesizer is proposed for generating a signal having a frequency which varies in response to a control voltage, which is determined by a control signal.
Abstract: A phase locked loop frequency synthesizer comprises a voltage-controlled oscillator (VCO) for generating a signal having a frequency which varies in response to a control voltage A variable frequency divider divides the output frequency of the VCO in a ratio which is determined by a control signal A reference oscillator supplies a reference signal having a predetermined frequency A fixed frequency divider divides the frequency of the reference signal in a fixed ratio A phase comparator compares the phases of the outputs of the fixed frequency divider and variable frequency divider to provide a control pulse corresponding to a phase difference between these outputs A charge pump has a power supply terminal for generating a charge/discharge voltage in response to the control pulse A loop filter includes a first capacitor which is supplied with the charge/discharge voltage for supplying a control voltage to the VCO which corresponds to the charge/discharge voltage A power supply circuit generates a DC voltage by boosting the voltage of the output of the fixed frequency divider and by supplying this boosted voltage to the charge pump The invention finds its greatest use in a portable radio receiver

Patent
24 Jul 1986
TL;DR: In this paper, a single modulator is used to produce three groups of sidebands on the laser beam at the laser frequency plus and minus the two modulation frequencies and at plus andminus the difference between the modulation signal frequencies.
Abstract: FM laser spectroscopy apparatus includes a single modulator for modulating a laser beam with first and second modulation signals (ω1, ω2). The two modulation signals are generated by mixing a signal from a first oscillator (ω1 +ω2)/2 and a signal from a second oscillator (ω1 -ω2)/2 and producing the two modulation signals (ω1, ω2). The modulator produces three groups of sidebands on the laser beam at the laser frequency plus and minus the two modulation frequencies and at plus and minus the difference between the two modulation signal frequencies. The apparatus provides practical high frequency FM spectroscopy as required for the observation of pressure broadened spectral features.

Patent
18 Feb 1986
TL;DR: In this paper, an up/down counter is up counted using the output of a VCO's output as a clock for a fixed time and is then down counted by a clocking signal related to the power main's frequency.
Abstract: A voltage to frequency converter or conditioner adapted for use with electromagnetic flowmeters produces a signal whose output frequency is related to measured flow while compensating for power frequency interference and variations in magnet current or magnetic induction B. The driving signal is summed with a feedback signal and coupled to a sampling integrator which drives the detector. The output of the detector (which may be integrated) is provided as the input to a VCO for producing the desired output signal. The VCO output is also coupled into a feedback circuit to which is also coupled a reference voltage which is at least proportional to the magnetic induction B or magnet current I. In one embodiment of the invention, an up/down counter is up counted using the VCO's output as a clock for a fixed time and is then down counted by a clocking signal related to power main's frequency. The time required for the down count operation is used to meter the feedback voltage to the summing junction at the input of the integrating sampler. This metering of the feedback voltage may be eliminated by the use of a multiplying DAC which produces an analog voltage corresponding to the product of the reference voltage and the count attained in the up/down counter which is modified so as to eliminate the necessity for down counting and is rather reset at the beginning of each integration period.

Patent
25 Feb 1986
TL;DR: In this paper, a pulse width modulator is used to derive variable frequency pulses having a frequency that is a direct function of an RMS like function of the amplitude and frequency of an information source; the width of the pulses is determined by the instantaneous amplitude of the information signal source.
Abstract: An RF-AM transmitter of the type including a power pulse amplifier driving an RF amplifier with a modulating voltage via a low pass filter includes a pulse width modulator for deriving variable frequency pulses having a frequency that is a direct function of an RMS like function of the amplitude and frequency of an information source; the width of the pulses is determined by the instantaneous amplitude of the information signal source. The pulse width modulator includes a constant amplitude, variable frequency triangular wave voltage controlled oscillator responsive to a DC signal representing the frequency and amplitude of the information source. In response to amplitude crossovers between the variable frequency triangular wave and the information source, transitions in the pulse width modulated wave are derived.

Journal ArticleDOI
TL;DR: In this paper, the frequency modulation due to injection current modulation of vapor phase transported distributed feedback (VPT DFB) semiconductor lasers is measured as a function of modulation frequency from 10 kHz to 1 GHz.
Abstract: The frequency modulation (FM) due to injection current modulation of vapor phase transported distributed feedback (VPT DFB) semiconductor lasers is measured as a function of modulation frequency from 10 kHz to 1 GHz. A large frequency modulation response of 350 MHz/mA is obtained for the modulation frequency range of 10 to 1000 MHz. Demodulation of optical frequency shift keying (FSK) at 560 Mb/s is demonstrated, indicating that frequency modulation due to thermal modulation does not pose a significant limitation at this bit rate or higher. The large FM response together with modulation bandwidths up to 8 GHz makes the VPT DFB laser an attractive source for high bit rate optical FSK transmission.