Abstract: A radio frequency (RF) link includes a link transmitter that includes a data modulator for modulating a data waveform together with an RF carrier, a photonic encoder coupled to the data modulator, and a transmitter antenna for transmitting an RF signal, wherein the RF signal comprises an output of the photonic encoder, and a link receiver including a receiver antenna for receiving the RF signal, a first laser source, a photonic limiter coupled to the first laser source and to the receiving antenna, a photonic decoder coupled to the photonic limiter, a photo-receiver coupled to the photonic decoder, and a demodulator coupled to the photo-receiver for demodulating an output of the photo-receiver with the RF carrier to form a data output.

Abstract: A method for exciting a resonator having a resonance frequency, the resonator is excited in a first period with a first frequency that differs from the resonance frequency by a first frequency difference is provided. During a second period, the resonator is excited with a second frequency that differs from the resonance frequency by a second frequency difference. The first frequency difference and the second frequency difference have different signs. Additionally, the amounts of the first frequency difference and of the second frequency difference differ from one another by less than 10% of the greater amount.

Abstract: A circuit and corresponding method are presented for generating an analog voltage from a digital input value is presented. An digital to analog conversion circuit, which is connected between a node and ground, receives an N-bit digital input value and generate from it a corresponding analog voltage. The node receives an input voltage provided by an op-amp connected to receive a reference voltage. The circuit also includes a variable resistance connected between the first node and ground in parallel with the digital to analog conversion circuit. The variable resistance is also connected to receive one or more of the digital input value and the value of the variable resistance is dependent upon the digital input values such that the combined current drawn from the first node by the variable resistance and the digital to analog conversion circuit is essentially constant during operation.

Abstract: A synchrocyclotron includes magnetic structures that define a resonant cavity, a source to provide particles to the resonant cavity, a voltage source to provide radio frequency (RF) voltage to the resonant cavity, a phase detector to detect a difference in phase between the RF voltage and a resonant frequency of the resonant cavity that changes over time, and a control circuit, responsive to the difference in phase, to control the voltage source so that a frequency of the RF voltage substantially matches the resonant frequency of the resonant cavity.

Abstract: A stabilised voltage controlled oscillator circuit comprises a closed loop circuit containing a voltage controlled oscillator (34), a local oscillator (40) and a harmonic mixer (38) that mixes a stabilised local oscillator (LO) frequency signal and a radio frequency (RF) signal from the voltage controlled oscillator (34) to obtain an intermediate frequency (IF) signal. An IF amplifier (42) is connected to a linear frequency discriminator (44) that provides an output signal to a summing amplifier (46), which is connected to the voltage controlled oscillator (34). The closed loop circuit uses the linear frequency discriminator (44) to provide a feedback signal that stabilises the voltage controlled oscillator (34).

Abstract: A tunable local oscillator (10) with a tunable circuit (12) that includes a resonator (16) and a transistor (14) as an active element for oscillation. Tuning of the circuit (12) is achieved with an externally applied dc bias (22, 24) across coupled lines (20) on the resonator (16). Preferably, the resonator (16) is a high temperature superconductor microstrip ring resonator with integral coupled lines (20) formed over a thin film ferroelectric material. A directional coupler (38) samples the output of the oscillator (14) which is fed into a diplexer (40) for determining whether the oscillator (14) is performing at a desired frequency. The high-pass and low-pass outputs (42, 44) of the diplexer (40) are connected to diodes (48, 46) respectively for inputting the sampled signals into a differential operational amplifier (50). Amplifier (50) compares the sampled signals and emits an output signal if there is a difference between the resonant and crossover frequencies.

Abstract: A 1-port tunable frequency discriminator that is incorporated into a frequency lock loop (FLL) for providing an improved FLL having reduced phase noise and settling times is provided. The invented 1-port tunable delay line discriminator reduces the phase noise generated by VCO's to approximately 105 dBc/Hz at 10 kHz, to better than 120 dBc/Hz at 100 kHz. The invention additionally reduces post tuning drift to less than 10 kHz after one microsecond. A secondary feedback loop, such as a conventional phase lock loop, can be incorporated into the invented FLL for providing phase and frequency coherency. The invention is formed by coupling a voltage controlled oscillator source (VCO) to a microwave signal detector and to an open ended delay line. When a microwave signal generated by the VCO reaches an end of the open ended delay line, a majority of the signal is reflected back along the line.

Abstract: A programmable apparatus is disclosed for generating a frequency modulated signal at a selected center frequency in accordance with digital data of at least first and second data levels. The modulating apparatus comprises a modulator having an input and an output and is responsive to an input modulation signal applied to its input for generating at its output the frequency modulated signal at a center frequency dependent on a quiescent voltage appearing at its input. A circuit is provided for sampling and storing a value of the quiescent voltage. An addressable memory stores a plurality of offsets. A programmable adding circuit adds a downloaded offset voltage to the stored value of the quiescent voltage to output a high modulation voltage. A programmable subtracting circuit subtracts a downloaded offset voltage from the stored value of the quiescent voltage to provide a low modulation voltage.

Abstract: A dielectric resonator frequency discriminator comprising a microstrip, a single mode dielectric resonator coupled to the microstrip, at least one detector for detecting an RF signal coupled to the microstrip and an RF input for introducing an RF signal coupled to the microstrip.

Abstract: A frequency oscillator and a frequency multiplier multiplying the signals from the oscillator contain inherent phase noise. A phase noise canceller removes phase noise, due to both the oscillator and the multiplier, by inserting a delay in one path and comparing phases of the delayed signal and the undelayed signal. This comparison may be either fed back to the tuning port of the oscillator or fed forward to a phase shifter which shakes off the phase noise. The delay may include a delay line, a cavity or any other suitable device which produces a phase shift. The phase noise canceller may also be designed to remove the total phase noise of the system, including additive phase noise from sources other than the oscillator and multiplier. The canceller may be calibrated and may be designed to reduce periodic response thereof.

Abstract: A first oscillator includes: a ring resonator; an oscillation circuit having a negative resistance active circuit coupled to a first point on the ring resonator for oscillating at an oscillation frequency and resonating the resonator; an output terminal, coupled to a second point on the ring resonator where a voltage is substantially zero with respect to the predetermined frequency when the ring resonator resonates, for outputting a resonant frequency signal, wherein even order harmonic components are outputted with the fundamental component suppressed. A second oscillator includes a ring resonator having points A to D equidistantly dividing the ring resonator, first and second oscillation circuits coupled to the points A and B respectively, first and second grounding capacitors having capacitance equivalent to those of the first and second oscillation circuits. Thus, two independent oscillators which do not affect each other are provided with a single resonator.

Abstract: In addition to a first opening (11) forming a primary output from a waveguide cavity (10) of a microwave oscillator, a coupling aperture (12) in a reflective wall (32) provides a secondary output which does not degrade the performance or tuning characteristics of the source. Less than -20 dB of the source power may be coupled out via the aperture (12) and is used in a feed-back loop (12,21,23,24,36) with an harmonic mixer (21) and frequency discriminator (24) to stabilize the source. The mixer comprises a further waveguide section (15) separated from the source cavity (10) by the reflective wall (32). An advantageous mixer assembly comprises a circuit substrate which is mounted across the further waveguide cavity (15) and which carries an inductive probe by which the signal from the coupling aperture (12) is fed to an antiparallel pair of mixer diodes on the substrate. The whole assembly may be bolted together through holes (34).

Abstract: A microwave oscillator is shown to include an oscillator having an output and a control port and a feedback circuit disposed between the output and the control port of the oscillator. The feedback circuit includes a modulated laser, having an input and an output, the input responsive to a portion of a signal from the output of the oscillator and a photo detector having an input and an output, the input of the photo detector responsive to a signal from the output of the modulated laser delayed by a predetermined amount of time. The feedback circuit further includes a detector having a first and a second input and an output, the first input of the detector responsive to a signal from the output of the photo detector, the second input responsive to a portion of the signal from the output of the oscillator shifted in phase to be in phase quadrature with the signal at the first input of the detector and the output of the detector coupled to the control port of the oscillator.

Abstract: A circuit for stabilizing an oscillator having an oscillator output signal includes a long optical fiber delay line which receives an optical version of the oscillator output signal and a phase detector sensing the oscillator output signal and the delayed optical output signal through the long optical fiber. The output of the phase detector is fed back to the oscillator's frequency control input to stabilize the frequency. The phase detector and the delay line are a delay line discriminator, and the length of the optical fiber is selected so as to optimize the discriminator's sensitivity against signal attenuation in the optical fiber, the optical fiber length typically being on the order of 10 kilometers.

Abstract: A microwave frequency discriminator circuit useful as a frequency lineariion device includes a microstrip input conductor and a pair of microstrip output conductors, a pair of resistors, a pair of microstrip transmission line diplexer stubs of unequal lengths, a pair of detector diodes, and a quad of microstrip filter stubs. Each resistor at one end is connected to the same end of the input conductor and in parallel relation to one another. Each diplexer stub at one end is connected to an opposite end of one resistor and in parallel relation to one another. Each diplexer stub is open-circuited at an opposite end. Each detector diode at one end is connected to the one end of one stub and at an opposite end to one output conductor. The filter stubs are interposed in spaced pairs in one output conductor.

Abstract: Stabilizing a signal generating source by coupling a small amount of the output power through a bandpass filter tuned to the desired frequency and injecting the power back into the source. In another embodiment the filtered power may be increased by injection locking a smaller oscillator and using the output to stabilize the source, or the filtered power may be amplified in a reflection amplifier and injected into the source for stabilization.

Abstract: An improved frequency locking circuit suitable for indirectly locking an optical frequency f.sub.0 to a radio frequency f.sub.1 or of locking the radio frequency to the optical frequency. A beam of optical frequency f.sub.0 is modulated by a compound signal which is the sum of a signal at frequency f.sub.2 and an FM subcarrier at frequency f.sub.1 that is phase modulated at frequency f.sub.3 to produce a phase modulated beam. The phase modulated beam is filtered by a filter having a transfer function having a characteristic frequency f.sub.f. A pair of control signals are generated that are proportional respectively to the amplitudes of two components of the filtered signal at frequencies f.sub.2, f.sub.3. These control signals are separately used in a pair of servo loops to separately establish fixed values of f.sub.0 /f.sub.f and f.sub.1 /f.sub.f. By using an optical cavity of the filter, the frequency locking circuit may be used for measuring the refractive index of a gas.

Abstract: Circuit imperfections in phase modulators will introduce offsets in the servo error signals in frequency locking circuits. Such offsets will also cause a frequency offset. The frequency offset is first reduced by reducing or removing amplitude modulation at the modulating frequency in the modulated carrier signal. In the preferred embodiment, this is accomplished by a coupled servo which includes a matrix loop filter. After the amplitude modulation at the modulating frequency has been removed, sideband imbalance can be corrected by amplitude modulating the modulating signal so that the offset caused by sideband imbalance is reduced or eliminated. This will be the case provided that the integral of at least the third power of the amplitude modulation vanishes.

Abstract: A microwave frequency discriminator, i.e. an electronic device for directly transforming frequency modulation on a microwave carrier into a demodulated lower frequency signal. The discriminator is similar to a Travis discriminator and includes an inlet microstrip line, two resonant circuits (R.sub.1, R.sub.2) constituted by dielectric resonators and coupled to said inlet microstrip line to receive the modulated microwave signal, two outlet microstrip lines coupling each resonator to a respective microwave detector circuit, said detector circuits including loads (r.sub.1, r.sub.2) in series-opposition in the manner of a Travis discriminator. An amplitude limiter suitable for connection to the discriminator includes a three-port circulator having a first port for receiving microwaves, a third port for providing microwaves to the discriminator, and a second port intermediate the first and third ports in the direction of circulation, the second port being coupled to a synchronized oscillator.

Abstract: A frequency discriminator (1) stabilizes a voltage controlled oscillator (5), particularly one operating at microwave frequencies. A single dielectric resonator (2), typically positioned within a housing (8), is excited by an r.f. input (30). The dielectric resonator (2) generates in response to the excitation first and second orthogonal modes of r.f. electromagnetic energy at slightly different frequencies. The two orthogonal modes are converted to d.c. output signals (39, 40) of opposite polarity and substantially the same magnitude, e.g., by diodes (35, 36). Frequency offsets are obtained by tuning screws (43, 44) and/or by changing the amount of dielectric (2) in the path of the characterizing vector corresponding to the mode being frequency-offset.

Abstract: A wavemeter/frequency locking technique suitable for indirectly locking an optical frequency f.sub.0 to a radio frequency f.sub.1 or for locking the radio frequency to the optical frequency. A beam of optical frequency f.sub.0 is phase modulated by a signal of average frequency f.sub.1 that is itself modulated at frequency f.sub.2. The modulated beam is passed through a filter to a detector to produce a detector output signal that has components at linear integral sums of f.sub.1 and f.sub.2. A pair of control signals are generated that are proportional to the amplitude of two of the components of the detector output signal. These control signals are separately used in a pair of servo loops to separately establish fixed values of f.sub.0 /f.sub.f and f.sub.1 /f.sub.f, where f.sub.f is a characteristic frequency of the filter. A method is presented for stepping the value of f.sub.0 /f.sub.f to another value and measuring f.sub.1 /f.sub.2 at each of these values, thereby enabling the value of f.sub.

Abstract: A microwave frequency discriminator, i.e. an electronic device for directly transforming frequency modulation on a microwave carrier into a demodulated lower frequency signal. The discriminator is similar to a Travis discriminator and includes an inlet microstrip line, two resonant circuits (R.sub.1, R.sub.2) constituted by dielectric resonators and coupled to said inlet microstrip line to receive the modulated microwave signal, two outlet microstrip lines coupling each resonator to a respective microwave detector circuit, said detector circuits including loads (r.sub.1, r.sub.2) in series-opposition in the manner of a Travis discriminator.

Abstract: A particle accelerator with frequency correction is provided in which an electromagnetic wave, supplied by a generator, is injected into a cavity through a wave guide. A frequency corrector device comprises two non directional couplers taking directly from said wave guide a standing wave from which an error signal is elaborated and applied to said generator for correcting the frequency of the electromagnetic wave.

Abstract: A voltage controlled oscillator includes a VCO chip that is a monolithic circuit with a Gunn diode and varactor diode intercoupled by a resonant circuit. A detector/discriminator/power divider chip is coupled to the VCO chip through a directional coupler and is a monolithic circuit having a pair of discriminator diodes and amplitude detector diode on a semi-insulating substrate with associated circuit components. Connected-together electrodes of the discriminator diodes are connected to one output of the power divider. An electrode of the amplitude detector diode is connected to the other output of the power divider. Stagger-tuned resonant circuits are coupled to the other electrodes of the discriminator diodes. Conducting portions forming low pass filters couple the amplitude detector diode and the discriminator detector diodes to respective outputs.

Abstract: A wavemeter/frequency locking technique suitable for indirectly locking an optical frequency f.sub.0 to a radio frequency f.sub.1 or for locking the radio frequency to the optical frequency. A beam of optical frequency f.sub.0 is phase modulated by a signal of average frequency f.sub.1 that is itself modulated at frequency f.sub.2. The modulated beam is passed through a filter to a detector to produce a detector output signal that has components at linear integral sums of f.sub.1 and f.sub.2. A pair of control signals are generated that are proportional to the amplitude of two of the components of the detector output signal. These control signals are separately used in a pair of servo loops to separately establish fixed values of f.sub.0 /f.sub.f and f.sub.1 /f.sub.f, where f.sub.f is a characteristic frequency of the filter. A method is presented for stepping the value of f.sub.0 /f.sub.f to another value and measuring f.sub.1 /f.sub.2 at each of these values, thereby enabling the value of f.sub.

Abstract: Receiver comprising at least two output means taking out electric signals corresponding to sound waves propagating in different directions in a surface elastic wave amplifier disposed in the high frequency amplifier stage, wherein phase difference or frequency difference between outputs of said output means is detected and frequency of pumping electric power applied to said surface elastic wave amplifier is controlled in response to output thus detected.

Abstract: A delay line frequency discriminator having application to microwave equipment and particularly used for stabilizing an oscillator, including a first coupler supplied by the oscillator and connected to a second coupler by means of two electromagnetic transmission lines, wherein one of the transmission lines introduces a delay time .tau. compared with the other line. The second coupler delivers a sum signal which is the stabilized output signal of the oscillator and a difference signal to a third coupler which is also fed with a sampled portion of the output signal of the oscillator and supplies the oscillator via a detector and an amplifier.

Abstract: An apparatus for frequency stabilizing a microstrip oscillator using an integrated diplexer as a frequency discriminator. The crossover frequency of the microstrip diplexer is used in a feedback arrangement to stabilize a millimeter-wave oscillator. The diplexer is coupled to the output of the oscillator and detects a shift from the desired oscillator output frequency. This shift in frequency is converted to a voltage for controlling the varactor tuning element of the oscillator to thereby return the oscillator to the desired operating frequency. Means are also provided for sensing a temperature change in the diplexer and for insuring that the oscillator output frequency is maintained at the desired frequency regardless of this temperature change.

Abstract: In order to maintain a plurality of superconducting resonators, each having elastically deformable resonant structural elements, at the same natural frequency and phase position, each resonator is supplied with high frequency power independently of the other resonators forming part of the same system, the natural frequency of each resonator is set to a predetermined value by adjusting the amplitude of the power supplied, mechanical vibrations of the resonant structural elements are aperiodically suppressed by a velocity-dependent attenuation, and the resonator is returned to a predetermined high frequency operating vibration.

Abstract: A frequency discriminator having a bandwidth variable from a relatively narrow range to a very wide range in which the center frequency is simultaneously tunable over an extremely wide frequency range. The discriminator is insensitive to amplitude variations of the input signal and is capable of demodulating low level signals. The frequency discriminator is particularly useful for microwave frequency applications wherein the basic discriminator element is a ferrimagnetic resonator. The frequency discriminator forms a portion of several preferred embodiments including devices for the frequency control of signal sources, frequency measurement of signal sources, demodulation of frequency modulated signals and frequency tracking control for other ferrimagnetic devices.

Abstract: A system and method is disclosed for achieving frequency stabilization. A tunable element, such as a cavity structure, is stabilized through the use of multiple modulation to stabilize both the resonant frequency of the cavity structure and the probe signal coupled to an atomic, molecular or other reference resonance line. Said reference resonance line can be internal or external to the cavity structure. A local oscillator provides a carrier signal, which typically can be at a frequency of 5 MHz, with the carrier signal being phase or frequency modulated by multiple modulating signals, such as, for example, by modulating signals with frequencies of 12.2 KHz and 0.4 Hz, and the multiple modulated carrier signal then processed and the resulting probe signal coupled to the cavity structure substantially at a preselected frequency, which frequency can be approximately 1420 MHz for a hydrogen frequency standard useful for atomic clocks.

Abstract: An arrangement enables the frequency variation of a resonant element (an accelerating section for example) to be followed in dependence upon its temperature and the frequency of the hyperfrequency generator G feeding this resonant element Q to be controlled in dependence upon the frequency variations thereof. The arrangement comprises at least one reference cavity C associated with means for allowing the circulation of cooling fluid along the walls of said reference cavity and with heat supply for bringing it, at any instant, to the temperature of the resonant element Q, means for measuring the amplitude variation .DELTA.a of the signal corresponding to the frequency variation of said reference cavity C in terms of its temperature variation and a frequency variation system controlled by a signal proportional to the amplitude variation .DELTA.a, for modifying the operating frequency of the generator G.

Abstract: 1. A receiver for use in a PSK signal translation system comprising a voltage tunable local oscillator for continuously generating a reference frequency signal from which the suppressed carrier can be reconstructed, input signal means for an incoming PSK signal, means for adding said reference frequency signal to produce a synthesized carrier which is amplitude modulated by said incoming PSK signal, diode switch means for demodulating synthesized PSK amplitude modulated carrier for causing synchronous phase shifts of the PSK signal components of modulated synthetic carrier in response to the demodulated signals, to thereby provide a continuous unmodulated signal synthesizing the suppressed carrier of the incoming PSK signals; a servo loop, including said oscillator, said signal adding means and said phase shifting means, for locking said oscillator onto said synthesized carrier.

Abstract: An input signal, whose frequency is to be detected, is divided and sent i two arms. One arm applies a set phase and amplitude adjustment while the other arm has a phase response that is dependent upon the frequency. Both arms are fed to a phase detector whose output is used to indicate the frequency of the input.

Abstract: A frequency synthesizer or programmable multiple frequency source which uses a voltage-controlled oscillator (VCO) responsive to an independent control variable. The VCO is also responsive to control from an error loop circuit which derives an additional control voltage as a result of comparing the VCO frequency at any time with one of the phase delay multiples of a fiber optic delay line. The independent variable used to select an overall frequency desired controls the VCO directly to an approximate frequency and the fiber optic delay line and error generating loop associated therewith operates as an automatic vernier on the VCO to bring it into phase-lock with the nearest frequency which is a multiple of the reciprocal of the fiber optic line delay time.

Abstract: Frequency stabilization of an oscillator by compensating for slow frequency variations due to ambient temperature variations is achieved by diverting a fraction of the oscillator output to a waveguide line section having a coefficient of thermal expansion/.degree. C which is greater than the coefficient of relative frequency drift/.degree. C of the oscillator comprising, in sequence, a variable attenuator and a movable short. The variable attenuator is used to primarily adjust the amplitude of the diverted signal by one-half the desired amount preferably without varying the phase of the diverted signal. The movable short is primarily used for signal phase adjustment while simultaneously reflecting the attenuated signal back through the attenuator and towards the oscillator output.

Abstract: A controllable oscillator is maintained at a center frequency f.sub.o by the inventive system. The oscillator signal is directly coupled to one input of a diode detector via a first path, and is alternately coupled, at a clock signal rate, to the second detector input via second or third paths. The second path has a selected transfer characteristic such that when it passes the oscillator signal the diode detector output is at a null. The third path includes a resonator whereby the oscillator signal passed therethrough results in a null at the detector output only when the oscillator is tuned to f.sub.o. The diode detector output is then phase detected with the clock signal thus producing an output correction signal which, when integrated, is fed back to the oscillator for precise control thereof. Since the system correction is dependent solely on an AC signal, errors due to the DC characteristics of the components, e.g. the detector diodes, may be eliminated.

Abstract: A phase lock loop configuration having a voltage controlled oscillator utilized, for example, in radar systems wherein false locking is prevented and loop bandwidth is maintained substantially constant. The voltage controlled oscillator includes a cavity resonator within which is located two tuning varactor diodes, one of which is heavily coupled to the resonator and comprises a coarse tuning port and one of which is lightly coupled and comprises the fine tuning port. The configuration is such that when the loop is locked, following a sweep mode of the coarse tuning voltage, the fine tune voltage is held constant at a predetermined DC level thereby making the fine tuning sensitivity essentially constant as the coarse tuning voltage changes the frequency over the band of interest.

Abstract: A Doppler type radio navigation system in which each element of a linear array is energized discretely and sequentially to produce a simulated Doppler effect at a remote location such as an aircraft on landing approach. A reference signal is also transmitted, and a receiver at the remote location "sees" a Doppler frequency shift proportional to the sine of the angle subtended by the receiver normal to the axis of the array by processing of the commutated data against the received reference signal to obtain a beat. A sum and difference transversal tracking filter arrangement is included for tracking the desired beat signal to exclude multi-path spurious beat signals. The tracking arrangement includes a voltage controlled oscillator, the detected beat signal being taken therefrom. Low noise bandwidth is obtained and performance under severe multipath conditions is improved.

Abstract: A highly stable variable frequency oscillator is disclosed which employs a ultitap surface acoustic wave device as a frequency standard. A feedback path which includes a voltage controlled switch for selecting a desired output tap drives a differential amplifier, phase detector, low pass filter, voltage controlled oscillator and phase splitter for driving the input tap of the surface acoustic wave device. Various additional feedback paths are also employed. The variable frequency signal is taken from the output of the voltage controlled oscillator.