Abstract: The invention concerns an oscillator generating a wave composed of a frequency of on the order of terahertz from a beat of two optical waves generated by a dual-frequency optical source. The oscillator includes a modulator the transfer function of which is non-linear for generating harmonics with a frequency of less than one terahertz for each of the optical waves generated by the dual-frequency optical source, an optical detector able to detect at least one harmonic for each of the optical waves generated by the dual-frequency optical source and transforming the harmonics detected into an electrical signal, a phase comparator for comparing the electrical signal with a reference electrical signal, and a module for controlling at least one element of the dual-frequency optical source with a signal obtained from the signal resulting from the comparison.

Abstract: A periodic signal generator is configured to generate high frequency signals characterized by relatively low temperature coefficients of frequency (TCF). A microelectromechanical resonator, such as concave bulk acoustic resonator (CBAR) supporting capacitive and piezoelectric transduction, may be geometrically engineered as a signal generator that produces two periodic signals having unequal resonant frequencies with unequal temperature coefficients. Circuitry is also provided for combining the two periodic signals using a mixer to thereby yield a high frequency low-TCF periodic difference signal at an output of the periodic signal generator.

Abstract: Techniques for detecting and mitigating interference are described. A device (e.g., a cellular phone) senses interference levels and digitally reconstructs the expected interference in the received signal. The device may correlate the reconstructed interference with the received signal and determine interference in the received signal based on correlation results. The device may adjust the operation of one or more circuit blocks (e.g., a mixer, an LNA, etc.) in a receiver based on the detected interference in the received signal. Alternatively or additionally, the device may condition the digital interference to obtain conditioned reconstructed interference matching the interference in the received signal and may then subtract the conditioned interference from the received signal.

Abstract: Provided are a harmonic rejection mixer and a harmonic rejection mixing method. A plurality of oscillator signals having a ? duty cycle and uniform phase differences may be generated and a differential or quadrature mixer with harmonic rejection may be realized by using the oscillator signals.

Abstract: Provided are a harmonic rejection mixer and a harmonic rejection mixing method. A plurality of oscillator signals having a ? duty cycle and uniform phase differences may be generated and a differential or quadrature mixer with harmonic rejection may be realized by using the oscillator signals.

Abstract: A novel and useful apparatus for and method of local oscillator (LO) generation with non-integer multiplication ratio between the local oscillator and RF frequencies. The LO generation schemes presented are operative to generate I and Q square waves at a designated frequency while avoiding the well known issue of harmonic pulling. The signal is input to a synthesizer timed to a rational multiplier of the RF frequency fRF. The signal is then divided to generate a plurality of phases of the divided signal. A plurality of combination signals are generated which are then multiplied by a set of weights and summed to cancel out some undersired products. The result is filtered to generate the LO output signal.

Abstract: A novel and useful apparatus for and method of local oscillator (LO) generation with non-integer multiplication ratio between the local oscillator and RF frequencies. The LO generation schemes presented are operative to generate I and Q square waves at a designated frequency while avoiding the well known issue of harmonic pulling. The input signal is fed to a synthesizer timed to a rational multiplier of the RF frequency L/N fRF. The clock signal generated is divided by a factor Q to form 2Q phases of the clock at a frequency of L(N*Q)fRF, wherein each phase undergoes division by L. The phase signals are input to a pulse generator which outputs a plurality of pulses. The pulses are input to a selector which selects which signal to output at any point in time. By controlling the selector, the output clock is generated as a TDM based signal. Any spurs are removed by an optional filter.

Abstract: Whispering-gallery-mode (WGM) optical resonators made of crystal materials to achieve high quality factors at or above 1010.

Abstract: A second harmonic oscillator has a series positive feedback configuration, suppresses output of a fundamental signal, and outputs a second harmonic signal having a frequency in a range from 1 GHz to 200 GHz generated inside of a circuit. The second harmonic oscillator includes: a transistor having a base terminal, a first emitter terminal, a second emitter terminal, and a collector terminal; a resonator circuit connected to the base terminal; a first transmission line shod-circuiting stub connected to one of the two emitter terminals; and a second transmission line short-circuiting stub connected to the other of the two emitter terminals and having a line length obtained by adding one-fourth of one wavelength of the fundamental signal to an integer multiple of one-half wavelength of the fundamental signal.

Abstract: Multiple carrier frequencies are provided from a phase locked loop, especially closely adjacent quadrature amplitude modulated subcarriers for multiplexed data communications. A quadrature voltage controlled oscillator (VCO) and cascaded frequency dividers provide feedback to a phase comparator to lock the VCO to a reference signal. In addition to frequency divider outputs for use as subcarriers, e.g., binary division factors of the VCO frequency, a quadrature mixer multiplies and adds corresponding quadrature components at two of the frequencies, to generate a differential signal at a difference frequency. The mixer may be outside of the feedback signal path but preferably is in the feedback path to suppress noise. A polyphase filter converts the mixer output to a quadrature signal useful as a subcarrier. The technique efficiently generates sequential integer multiples of a basic frequency, such as sixteen adjacent integer multiples of a frequency reference.

Abstract: An electronic circuit comprises a delay circuit that with a chain of saw tooth delay stages (10a-d), coupled in a loop to form an oscillator for example. Each stage comprises an integrating circuit (104) and a current modulator (106) coupled to the integrating circuit (104). Each stage triggers a transition in the next stage when the integration result reaches a level defined by a reference voltage. Correlating circuitry (102, 30, 32, 34) is provided with current outputs to generate currents to the current modulators (106) and reference voltages for the saw tooth delay stages (10a-d). The reference voltages are generated at least partly from a common reference (102c), so that noise in the currents from the current modulators (106) and reference voltages is correlated in a way that at least partly cancels the effect of the noise on the delay time.

Abstract: An IF input signal corresponding to a selected reception channel is applied through an SAW filter to an IF-AGC circuit, the amplitude of the signal is adjusted to a prescribed level, and the signal is thereafter supplied to a down converter unit. The down converter unit selectively outputs a Low-IF signal provided by down-converting the IF input signal and the High-IF signal amplified without frequency conversion, in accordance with an external instruction. A filter circuit has its cut off frequency selectively set to pass the Low-IF signal only, or both the Low-IF and High-IF signals.

Abstract: The present invention relates generally to communications, and more specifically to a method and apparatus for generating local oscillator signals used for up- and down-conversion of RF (radio frequency) signals. A major problem in the design of modulators and demodulators, if the leakage of local oscillator (LO) signals into the received signal path. The invention presents a number of highly integratable circuits which resolve the LO leakage problem, using regenerative divider circuits acting on oscillator signals which are running at a multiple or fraction of the frequency of the desired LO signal, to generate in-phase (I) and quadrature (Q) mixing signals. Embodiments of these circuits also use harmonic subtraction and polyphase mixers, as well as virtual local oscillator TM (VLO) mixing signals. VLO mixing signals are signal pairs which emulate local oscillator signals by means of complementary mono-tonal and multi-tonal mixing signals.

Abstract: A multi-band local oscillator for generating an output oscillator signal of a desired frequency is implemented with a single voltage controlled oscillator providing an input oscillator signal and a switch divider block. The output signal is passed through a selected one of a set of filters for band switching and through a frequency divider and subsequently mixed with the input oscillator signal of the voltage controlled oscillator.

Abstract: A microwave synthesizer includes a drift-cancel loop having a narrow-band input, a low-frequency comb input, a wide-band input, and an output for providing an adjustable-frequency output signal. A narrow-band synthesizer is coupled to the narrow-band input, and a comb generator is coupled to the low-frequency comb input. Instead of using a wide-band synthesizer to drive the wide-band input, as conventional topologies have done, the instant invention employs a highly stable, low noise high frequency oscillator. The output of the oscillator is mixed with the output of the comb generator to produce low-noise, high frequency combs. The low-noise, high frequency combs are then used to drive the wide-band input of the drift-cancel loop. Significant reductions in phase noise can be achieved as compared with conventional designs.

Abstract: A microwave synthesizer includes a drift-cancel loop having a narrow-band input, a low-frequency comb input, a wide-band input, and an output for providing an adjustable-frequency output signal. A narrow-band synthesizer is coupled to the narrow-band input, and a comb generator is coupled to the low-frequency comb input. Instead of using a wide-band synthesizer to drive the wide-band input, as conventional topologies have done, the instant invention employs a highly stable, low noise high frequency oscillator. The output of the oscillator is mixed with the output of the comb generator to produce low-noise, high frequency combs. The low-noise, high frequency combs are then used to drive the wide-band input of the drift-cancel loop. Significant reductions in phase noise can be achieved as compared with conventional designs.

Abstract: A voltage controlled oscillator comprises first oscillating stage for outputting a first frequency signal, second oscillating stage for outputting a second frequency signal different from the first frequency signal, a buffer stage connected with said first and second oscillating stages, the buffer stage receiving said first and second frequency signals to generate an output signal.

Abstract: A low-power digital frequency synthesizer combining direct digital frequency synthesis techniques with serrodyne frequency translation principles to produce a wideband frequency response with high spectral purity. A conventional direct digital synthesizer is used to generate a high-resolution analog carrier signal from a low-speed digital clock signal. The carrier signal is phase modulated by a low-resolution signal generated from a high-speed digital clock signal. The modulation signal is a higher frequency signal than the carrier signal. The phase modulation is accomplished by exact decoded gain elements. The spectral purity of the resulting high-resolution output signal is unobtainable by conventional direct digital synthesizers, while providing significant power savings.

Abstract: A synthesized oscillation circuit that can relax a limitation of the maximum operational frequency. A mixer (MX), a bandpass filter (BPF), an amplitude limiting amplifier (LIM), a phase detector (PD), a low-pass filter (LPF), and a voltage-controlled oscillator (VCO) are serially connected between a signal input terminal (IN) and a signal output terminal (OUT). The signal output terminal (OUT) is connected the mixer (MX) and the phase detector (PD). The bandpass filter (BPF) has a filtering characteristic which blocks the sum frequency component of the frequency component of an input signal from the signal input terminal (IN) to the mixer (MX) and the frequency component of an output signal from the voltage-controlled oscillator (VCO) to the mixer (MX), but which passes the difference frequency component between them.

Abstract: The ability to achieve ultra-fast frequency settling times with good frequency resolution and high absolute accuracy over significant bandwidth at microwave frequencies ranging over three octaves. The implementation is an open-loop system requiring little or no compensation of temperature. This is accomplished by providing a frequency doubled direct digital synthesizer output to up/down convert a microwave frequency source. A special tracking filter architecture coupled to the microwave source provides the suppression of unwanted products. Fixed frequency set-on and swept bandwidths in excess of 300 MHz have been demonstrated. This is accomplished by using a direct digitally synthesized quadrature phased carrier which can be set to any frequency within a 350 MHz bandwidth to coherently up/down convert a low phase-noise microwave frequency to the sum or the difference frequency product.

Abstract: A frequency synthesizer using a fixed oscillator driving a comb line generator to generate a spectrum of comb lines, one of which is selected by a switched array of fixed-tuned, YIG passband filters. The selected comb line is combined in a mixer with a signal from a local oscillator, which, preferably, is a direct digital synthesizer. The output of the mixer is fed to another switched array of fixed-tuned YIG passband filters where only the desired sideband is selected and the comb line and the other sideband is filtered out. In various alternative embodiments, tunable YIG filters are substituted for each array. Some embodiments also use a reverse slope equalizer to break up the coherent energy in the comb line spectrum at the output of the comb line generator to allow RF amplification to be applied without saturating the amplifier.

Abstract: A multimode oscillator is disclosed which employs a single gain loop for exciting at least two modes of a resonator to cause the oscillator to oscillate simultaneously at at least two frequencies. The multimode oscillator comprises the resonator, an amplifier to provide gain at the appropriate operating frequencies to support simultaneous oscillation at such frequencies and an equalizing network with amplitude and phase characteristics versus frequency to support the simultaneous modes of oscillation. The single loop oscillator permits separate control of the two simultaneous different frequencies of oscillation. In order to minimize thermal hysteresis, at least the active portion of the feedback loop does not include inductors. In some applications, the multimode oscillator may include one or more rejection networks to suppress unwanted oscillations. The useful outputs of the multimode oscillator are one or more of the operating frequencies, harmonics and intermodulation products.

Abstract: A multimode oscillator is disclosed which employs a single gain feedback loop for exciting at least two modes of a resonator to cause the oscillator to oscillate simultaneously at at least two frequencies. The multi-mode oscillator comprises the resonator, an amplifier to provide gain at the appropriate operating frequencies to support simultaneous oscillation at such frequencies and an equalizing network with amplitude and phase characteristics versus frequency to support the simultaneous modes of oscillation. The single loop oscillator permits separate control of the two simultaneous different frequencies of oscillation. In order to minimize thermal hysteresis, at least the active portion of the feedback loop does not include inductors. In some applications, the multimode oscillator may include one or more rejection networks to suppress unwanted oscillations. The useful outputs of the multimode oscillator are one or more of the operating frequencies, harmonics and intermodulation products.

Abstract: A single transistor dual mode crystal oscillator circuit is described which may excite more than one C-mode frquency in a crystal simultaneously such as the fundamental, used as a clock driver frequency, and a beat frequency between the third harmonic and the third overtone frequency, simultaneously. Each signal is thereafter passed through a separate amplifier means to further enhance those outputs for use.

Abstract: A field telephone system having a widely dispersed set of telephone lines including a page line pair and a party line pair, audio processing equipment including telephone handsets, handset amplifiers, receiver amplifiers and paging speaker amplifiers is designed to have improved voice transmission by provision of a narrow band FM carrier system. The FM carrier system includes a device for generating a carrier frequency signal, a modulator for modulating the carrier frequency with an audio signal derived from one of the handsets at a transmitting station and circuitry for transmitting the modulated signal over a line pair to a receiving station. The receiving station includes circuitry responsive to the transmitted signal and the carrier frequency signal for extracting the audio component of the transmitted signal and for processing the extracted audio signal and for providing the processed audio signal to a handset at the receiving station.

Abstract: A frequency converter circuit for converting a high-frequency signal into an intermediate-frequency signal includes a local oscillation with a first transistor having first, second and third terminals. A first terminal of the first transistor is grounded through a first inductance and a first capacitor, while a second capacitor is inserted between the other two terminals. A resonance circuit including variable-capacity diodes and a second inductance is connected to the second terminal through a third capacitor. The frequency converter circuit further includes a mixer formed with a second transistor having a base thereof connected to the grounded terminal of the first transistor and an emitter thereof grounded through impedances offering substantially no resistance to the intermediate-frequency signal. The emitter of this second transistor is connected to a high-frequency input terminal supplied with a high-frequency signal.

Abstract: For eliminating an unwanted leaking local oscillator signal from the output of a double-balanced mixer circuit in a microwave frequency up-converter, a band rejection filter formed of series connected impedance inverter elements and a plurality of tuned cavity resonators is provided. The cavity resonators are integrally formed by the cylindrical walls of an aluminum housing, the top portion of which is formed of a plated printed circuit board. That face of the printed circuit board which faces the cylindrical cavities of the resonators is plated with copper to form the upper surface of each resonator. The other side of the printed circuit board is selectively plated with copper layers which extend through the board to the lower layer to provide an extensive ground plane.

Abstract: The present invention relates to a time and frequency control unit which is apable of compensating for long-term crystal oscillator drift and other errors in a reference oscillator signal by both coarse and fine (vernier) controlling. The invention takes the reference oscillator frequency, f.sub.o, divides it by a controlled factor a and mixes f.sub.o with f.sub.o /a to produce an f.sub.o + f.sub.o /aSignal. The f.sub.o + f.sub.o /aSignal is then divided by a second controlled factor b and mixed again with f.sub.o to yield a signal of frequency f.sub.o .+-. (f.sub.o + f.sub.o /a) 1/b,Where f.sub.f, the final output frequency, is determined after a filter stage sets the operation sign of the above expression (to plus or minus). Where f.sub.f is intended to be constant with a changing f.sub.o, the values of a and b are changed. From the above expression, it is apparent that a change in a makes a fine correction whereas a change in b translates the frequency with a coarse adjustment.