Abstract: A notch filter as disclosed which is adaptable to notching out a background siren from voice communications from an emergency vehicle. Two embodiments are disclosed. In the first embodiment, a frequency lock loop tracks the fundamental frequency of an electronic siren. The siren fundamental frequency is then notched out from voice transmissions using a notch filter. In the preferred transmissions using a notch filter. In the preferred embodiment, a digital ramp is generated by a first digital signal processor. This signal is input to an amplifier and a speaker thus producing an electronic siren. The digital ramp is also input to a second digital signal processor which notches out the fundamental frequency and odd harmonics thereof from the digital ramp thus acting as a comb notch filter. Analog voice is digitized by way of an analog to digital converter and input to the second digital signal processor.

Abstract: In a phased array antenna the phase of the signal applied to each antenna element is controlled by a phase lock loop which is locked to the frequency of a reference oscillator but whose phase is offset from it alternatively by introducing a DC offset to an integrator within the phase lock loop or by presenting a digital code to a counter circuit.

Abstract: An improved platform transmitter terminal (PTT) is disclosed for use in an ARGOS type satellite system. The PTT has reduced size, weight and extended life due to a solar array/rechargeable battery power source operating under the supervision of a unique power supply control and protection means. The invented PTT, when used in an ARGOS type system, opens the possibility of tracking, on a global basis, wild animals weighing as little as a few kilograms.

Abstract: A voltage-controlled-oscillator with a modulator, comprising a first variable capacitance diode, a second variable capacitance diode, and a third variable capacitance diode. The second variable capacitance diode is connected in series with the third variable capacitance diode to form a serial connection member.

Abstract: A voltage-controlled-oscillator with a modulator, comprising a first variable capacitance diode and a second variable capacitance diode. The first variable capacitance diode is connected in series with the second variable capacitance diode to form a resonance device, wherein capacitance of the first variable capacitance diode is controlled by applying a reverse bias voltage and an oscillation frequency control voltage to both ends of the first variable capacitance diode, and capacitance of the second variable capacitance diode is controlled in a reverse direction to changes in the capacitance of the first variable capacitance diode with respect to the oscillation frequency control voltage by applying the oscillation frequency control voltage and a modulation signal to both ends of the second variable capacitance diode to thereby provide a frequency modulated wave.

Abstract: A UHF transmission frequency oscillator generates a UHF radio signal that is frequency modulated by a program signal. The voltage applied to a control voltage input of the UHF transmission frequency oscillator controls the transmission frequency. A sample of the UHF transmission frequency signal is heterodyned with the output of a crystal controlled reference frequency oscillator to generate a frequency difference signal. A voltage controlled VHF radio signal generator produces a VHF signal frequency modulated by the program signal. A phase detector receives the frequency difference signal and the VHF signal frequency modulated by the program signal and therefrom applies a voltage to the control voltage input of the UHF transmission frequency oscillator for the transmission of a UHF radio frequency signal frequency modulated by the program signal. The VHF voltage controlled generator has VHF programmable frequency dividers, which are pre-settable, to establish the VHF radio transmission frequency.

Abstract: A modulator including a voltage controlled oscillator (VCO) having its center frequency stabilized to a reference frequency using a phase locked loop in which the low frequency range is increased by using frequency translation techniques. The VCO output signal is translated relative to the phase locked loop feedback signal so that an increased frequency division ratio can be used in the feedback loop and the effective frequency deviation at the phase comparator can be reduced by an arbitrary factor. This has the effect of increasing the allowable deviation at a given information signal frequency by that arbitrary factor. Likewise, a given deviation can be maintained for input information frequencies which are an arbitrary fraction of the low end cutoff frequencies of conventional modulators.

Abstract: The invention provides a DC-FM phase locked loop for use in transmitters for measuring and control purposes, wherein the modulation signal controls, via an A/D converter, the output frequency of a frequency synthesizer, this output frequency being used as the reference for the phase comparator. This permits modulation with extremely low frequencies or DC without the necessity to interrupt the loop.

Abstract: A frequency modulated transmitter including a reference frequency source providing a reference frequency to a phase locked loop circuit. The phase locked loop circuit provides a frequency output signal stabilized in accordance with this reference frequency and in accordance with a feedback signal. The phase locked loop circuit further includes a data input circuit that adjusts the output frequency in accordance with input data. Also included is the feedback circuit that provides the feedback signal to the phase locked loop circuit. This feedback circuit is derived from the frequency output signal. A synchronization circuit is connected to the feed back circuit and synchronizes the output of the feedback circuit with the reference frequency signal and the input data.

Abstract: A high frequency oscillator having an oscillation transistor connected to a resonant strip line unit consisting of a main strip line member and an auxiliary strip line member. The auxiliary strip line member is connected in parallel with or isolated from the main strip line member by a switch diode for switching the characteristic impedance of the strip line unit so as to generate a reception or transmission carrier wave output. A varactor diode connected to the strip line unit has its capacitance changed through an applied control voltage for channel switching. A modulating signal input terminal is directly connected to a portion of the auxiliary strip line member for modulating an FM transmission signal independently of the value of the control voltage applied to the varactor diode.

Abstract: An FM transmitter especially for physiological signal telemetry includes a transistor oscillator having a collector-to-base capacitance that is part of its tuned circuit. Means are disclosed for controllably varying the collector-to-base capacitance only in response to impressed physiological or other signals to provide FM modulated signals for aerial transmission to any suitable receiver. Means including cooperative constant emitter current and constant collector voltage DC biasing circuits are disclosed for eliminating undesirable, changing temperature induced frequency variations. Means are further disclosed for neutralizing undesirable antenna loading induced frequency variations. The system is capable of accepting multiplexed inputs.

Abstract: In a radio communication system, a transmitting section of a substation comprises a controlling circuit (21) for controlling a carrier frequency of a local oscillator (24) in response to a frequency deviation signal. A burst generating circuit (26) generates a burst in response to the input signal, a burst control signal, and a local oscillation signal of the carrier frequency. The transmitting section further comprises a holding circuit (34) responsive to a frequency control signal and the burst control signal. During presence of the burst control signal, the holding circuit holds the frequency control signal received before a beginning of the burst control signal to keep the carrier frequency of the local oscillation signal invariable until an end of the burst control signal. Otherwise, the frequency control signal passes through the holding circuit as it stands.

Abstract: A phase-locked loop modulation circuit, such as may be used for a data communications purposes, in which undesired level variations are eliminated by employing d.c. coupling entirely. The circuit includes a level converter circuit which converts a logic signal into a signal having substantially equal levels above and below a predetermined voltage, a voltage-controlled oscillator, and a circuit for superposing the signal having substantially equal levels on a control voltage of the voltage-controlled oscillator so that the output of the voltage-controlled oscillator is subjected to angular modulation.

Abstract: The invention concerns a frequency modulation broadcasting transmitter in which the output oscillator at the transmission frequency is modulated not directly by the audiofrequency signal but through the intermediary of a phase locking loop comprising a phase comparator supplied, on the one hand, by the output signal filtered from a picture or image frequency rejection mixer. This mixer receives, on the one hand, a modulated intermediary frequency signal from a modulator and, on the other hand, the output signal of the oscillator at the transmitting frequency F.sub.S, the reference frequency F.sub.o1 being determined as a function of the central transmitting frequency and of the intermediary frequency F.sub.o1 =F.sub.S -F.sub.1.

Abstract: A frequency synthesizing apparatus of the closed-loop design employing a first frequency mixing means to provide a continuous constant increment frequency coverage over a given output signal frequency range. The first frequency mixing means is responsive to the output signal and a first reference signal to provide a first difference signal both when the output signal frequency is higher than and lower than the first reference signal frequency. A frequency comparison means is responsive to the first difference signal and to an input signal, the input signal being continuously variable over a given input frequency range, to provide a first error signal for controlling the output frequency and stabilizing the closed loop. The first reference signal is comprising of a plurality of predetermined, selectable frequencies provided by a phase-locked loop employing a second frequency mixing means.

Abstract: Apparatus to provide calibrated frequency modulation (FM) of frequencies generated in a phase-locked loop is disclosed. A phase-locked loop (PLL) includes a voltage-controlled oscillator (VCO) which is locked to a loop frequence signal frequency. A modulo-10 divider is included which adds integral multiples of two pi radians of phase to the output signal of the VCO whenever the modulus of the divider is reduced by an integer. This forces the PLL to step change the loop frequency by an integral multiple of the reference frequency. A sampling circuit senses and measures the change in the VCO control voltage resulting from the step change in the loop frequency. The change in the control voltage is a measure of the VCO gain at that frequency. The change in the control voltage is converted to a digital number which is loaded into a multiplying digital-to-analog converter (DAC) to adjust the gain of the DAC.

Abstract: A 16-quadrature amplitude modulation (QAM) modulator for radio links converts a train of data into signals having a phase selected from sixteen predetermined phase values and an amplitude selected from four values. The modulator divides the data train into two data sub-trains. The two data sub-trains are respectively applied to a pair of four-phase modulators that are fed by a carrier source. The 16-QAM modulator also comprises two phase locked loops each including a voltage controlled microwave oscillator and an associated differential phase detector. The differential phase detector responds to the output of the associated four-phase modulator and the output of the associated voltage controlled microwave oscillator. Predetermined parts of the output signals of the two phase locked loops are added.

Abstract: A phase lock loop having an instruction input to which is applied the output signal of the frequency-modulated variable frequency oscillator. The pass band of the loop is regulated in order to obtain at its output, a frequency-filtered signal corresponding to the frequency-modulated signal applied to the instruction input. A phase demodulator having inputs coupled to the instruction input of the loop and to the output of the loop supplies a signal corresponding to the modulation index of the signal supplied by the oscillator. This signal is compared with a reference signal by a comparator circuit, which supplies a control signal to means for adjusting the amplitude of the modulating signal applied to the input of the oscillator, in order to permanently adjust the modulation index of the frequency-modulated signal, produced at the output of the oscillator, to the value of the desired modulation index corresponding to the reference signal.

Abstract: Apparatus is provided to frequency modulate (FM) RF carrier frequencies generated in a phase-locked loop (PLL). FM outside the loop bandwidth is AC coupled to the loop. FM within the loop bandwidth is DC coupled via an integrating OP-AMP to provide phase modulation. Whenever the output of the integrator exceeds a preset threshold, a prescaler removes or adds two pi (or integral multiples of two pi) radians of phase change from the input to the loop divide-by-N circuit. At the same time, a current source pumps charge into the integrator to exactly compensate for the amount of phase removed or added resetting the integrator. DC feedback around the integrating OP-AMP and a feedback signal proportional to the exact amount of phase added or removed provides a true synthesized loop center frequency with no drift. When the feedback path is interrupted, DC FM is provided.

Abstract: A SECAM modulator has a frequency control loop for maintaining constant average frequency of a VCO during a scanning line. However, this can cause varying deviation of the VCO. Therefore a second control loop is provided to control the voltage of the VCO to maintain constant voltage-to-frequency gain.

Abstract: A frequency modulation transmitter has a frequency synthesizer comprised of a voltage controlled oscillator for operating a transmitter section of the modulation transmitter. The output center frequency of the voltage controlled oscillator is determined by channel designation information. The level of a modulation input signal applied to the voltage controlled oscillator for modulating the center frequency is changed in accordance with the channel designation information.

Abstract: A voltage controlled oscillator includes a main varactor diode coupled to a frequency resonating circuit to produce an output frequency in response to a control voltage. A secondary varactor diode of an appreciably lower voltage to frequency sensitivity ratio is coupled to the main varactor diode. A modulation input circuit is coupled to the secondary varactor diode to enable modulation of the resonating output frequency. A linearizing circuit is coupled to the secondary varactor diode and tracks the main varactor diode capacitance to continuously adjust the bias voltage of the secondary varactor diode to provide constant carrier modulation deviation.

Abstract: In order to deliver an angle-modulated output signal as a function of digital information, the frequency synthesizer delivers an output frequency F.sub.S =(N+k)F.sub.R, where N is the integral part of a number N+k and F.sub.R is a reference frequency. Provision is made for a variable oscillator, an oscillator control loop comprising in series a variable divider having a preselected divisor N, a phase comparator for receiving the reference frequency and a summing device. The synthesizer further comprises a phase accumulator for performing, at the frequency F.sub.R, modulo-M summation of a number G=k(M) applied to its input. The sum and carry outputs of the accumulator are coupled respectively to the summing device in order to deliver a signal for compensating the signal delivered by the phase comparator and to the divider for delivering a control signal to select the divisor N+1.

Abstract: A frequency modulator for radio frequency (RF) signals is described that symmetrically modulates the RF signal with either binary signals or voice signals without distorting the amplitude of the binary signal near bit edges. The inventive frequency modulator includes a reference signal generator, a phase comparator for comparing the reference signal and a feedback signal to provide an error signal, a filter for filtering the error signal, a voltage-controlled oscillator (VCO) responsive to the filtered error signal for generating an output signal, a divider for dividing the VCO output signal by a predetermined number to provide the feedback signal, circuitry coupled to the VCO for modulating the VCO output signal with the binary signal, and circuitry coupled to the divider for varying the predetermined number of the divider between a first predetermined number and a second predetermined number in response to the binary signal.

Abstract: A transmitter having a transmitting phase synchronizing system. To one input of a frequency mixer is applied the output of a phase synchronizing type digital frequency synthesizer, through a first frequency divider. A modulating signal is applied to another input of the frequency mixer. The output from the mixer is connected via a bandpass filter to a phase synchronizing system having in series, along a main route, a phase detector, a lowpass filter, and a voltage controlled oscillator, and thence to an amplifier system. In a feedback route from another outlet of the voltage controlled oscillator to the phase detector is a second fixed frequency divider. The digital frequency synthesizer itself may have a reference oscillator connected in series to a third fixed frequency divider, a second phase detector, a second lowpass filter and a second voltage controlled oscillator, from which a feedback circuit leads back to the phase detector via the first fixed frequency divider and a variable frequency divider.

Abstract: A remote control circuit which operates on a frequency basis and essentially with analog signals. The remote control circuit includes at the transmitting end a controlled oscillator, a frequency/direct signal converter and a comparator connected together into a frequency control loop. A transmitter is also provided which is fed by the oscillator of the control loop. A control path including a frequency signal source and a frequency/direct signal converter is provided at the transmitting end and receives its input signal from the frequency signal source. The converter of the control path is connected with the one input of the comparator of the control circuit. At the receiving end there is provided an amplifier, a frequency/direct signal converter and an evaluation circuit.

Abstract: An FM transmitter is disclosed wherein a solid state microwave source at a first frequency is frequency modulated with a baseband signal, and a second such source at a different frequency is frequency modulated with the baseband signal inverted. Each of the modulated carriers is frequency doubled and input to a mixer. The output of the mixer is a carrier, having a frequency which is twice the difference of the two microwave frequencies, and frequency modulated by the baseband signal. An automatic frequency control circuit inputs equal and opposite control voltages to the two microwave sources.

Abstract: A programmable phase-locked loop frequency synthesizer having a feedback path that includes a tuned discriminator circuit is frequency modulated by coupling a portion of the modulating signal into the feedback path to effect modulation at rates which exceed the bandwidth of the phase-locked loop and by utilizing a portion of the modulating signal to frequency modulate the phase-locked loop reference signal to effect modulation at rates within the bandwidth of the phase-locked loop. A digitally controlled phase shifter that forms a portion of the discriminator tuning circuits in effect divides the phase-locked loop tuning range into a series of relatively narrow centiguous frequency bands. Data, representing deviations in the discriminator characteristics for each of these frequency bands, are stored in an erasable programmable read only memory.

Abstract: A phase-locked loop is disclosed that exhibits flat modulation characteristics over a wide range of carrier frequencies for either frequency or phase modulation at rates that are both within and outside the loop bandwidth. The disclosed arrangement is a programmable divide-by-N phase-locked loop frequency synthesizer wherein the feedback path includes a second phase-locked loop that serves as a tracking filter. Modulation is supplied to the main phase-locked loop via a first modulation path that couples the modulating signal to the frequency control terminal of the phase-locked loop voltage-controlled oscillator and via a second modulation path that couples the modulating signal to the phase-locked loop phase detector.

Abstract: A frequency modulator including a free-running oscillator which is frequency modulated and which is frequency stabilized by means of a reference oscillation by way of a phase control loop having a phase detector and a loop filter. In order to be able to process d.c. components with such a frequency modulator, given a keyed modulation signal, and without abandoning the limitation of the modulation spectrum, the modulation signal is supplied to a control input of the oscillator both by way of a modulation filter and by way of the phase control loop. For this purpose, the phase control loop includes, between the oscillator output and the phase detector, a frequency divider having a division ratio controlled by the modulation signal.

Abstract: A subcarrier frequency-modulated with a message signal is heterodyned with a carrier from a crystal-controlled oscillator in a mixer whose output is fed to a filter eliminating one of the resulting sidebands. In order to compensate temperature-dependent fluctuations of the carrier frequency, a function generator produces a corrective signal which is added to the message signal in the input of the frequency modulator traversed by the subcarrier. The corrective signal varies as a quadratic or a cubic function of temperature, depending upon the type of cut used on the quartz crystal controlling the carrier oscillator, with a polarity determined by which of the two sidebands is passed by the filter.

Abstract: The output frequency of a variable frequency oscillator is compared with that of a reference frequency source by means of a phase detector and the resultant error signal is integrated and applied as a negative feedback signal to the input of the oscillator whereby drift of the oscillator output frequency is minimized. Deviation, modulation index, dynamic stability and linearity are enhanced by means of a pulse generator that is synchronized with a modulating input signal supplied to the oscillator for supplying a keying signal to the phase detector during a portion of each cycle of the modulating input signal.

Abstract: A system which provides frequency conversion and continuously variable bandwidth control uses fixed filters to which opposite edges of the passband of the signal are applied in inverted frequency relationship. A channel contains the filters and three mixers to which injection signals derived from a single variable frequency oscillator and a fixed oscillator are applied to vary the bandwidth of the system without affecting the center frequency of the signal after processing in the system. The system may be designed to obtain either a variable bandpass or rejection band filtering characteristic.

Abstract: A simultaneous multichannel signal generator incorporating phase-locked l frequency correction. For each channel, there is a voltage-controlled oscillator (VCO) set to an appropriate frequency by a tuning signal and modulated by a channel data signal. The output signals from all VCO's are provided to a summer and then are appropriately amplified and filtered for transmission. A single multiplexed frequency correction circuit compares the phase of a reference frequency signal with the phase of a VCO output signal whose frequency has been divided, by a divide-by-N counter, to the reference frequency. If the divided VCO signal is out of phase with the reference frequency signal, an appropriate correction signal is provided to the device providing voltage control for that VCO.

Abstract: A frequency synthesizer including a phase lock loop comprising a voltage controlled oscillator, a four phase modulator for modulating the oscillator output signal, a phase detector for comparing the phases of a reference signal and the output signal of the modulator and filter means for supplying the phase detector output signal back to the oscillator. The two most significant bits of an arithmetic synthesizer are supplied to the modulator to produce, in the absence of additional modulating signals, discrete increments of 90.degree. phase shift in the oscillator output signal. To eliminate phase jitter, the remaining lower order bit positions of the arithmetic synthesizer are converted to analog voltages which are supplied into the phase lock loop to effect a gradual phase shift between the otherwise discrete 90.degree. phase shifts. Continuous phase, constant amplitude output signal is thereby produced having a frequency translated by the phase shifts introduced by the arithmetic synthesizer.