Abstract: An IQ mixer is used in a Pound-stabilized microwave source to detect amplitude modulation of the signal reflected from the reference resonator. By properly configuring the IQ mixer so that the LO and RF inputs are maintained in quadrature at the Q mixer, hence in-phase at the I mixer, lower levels of amplitude modulation may be detected at lower modulation frequencies compatible with optimal choices of resonator coupling and maximal phase to amplitude conversion.

Abstract: An IQ mixer is used in a Pound-stabilized microwave source to detect amplitude modulation of the signal reflected from the reference resonator. By properly configuring the IQ mixer so that the LO and RF inputs are maintained in quadrature at the Q mixer, hence in-phase at the I mixer, lower levels of amplitude modulation may be detected at lower modulation frequencies compatible with optimal choices of resonator coupling and maximal phase to amplitude conversion. With the Q mixer held in quadrature it acts as a broadband phase noise detector. A portion of the Q mixer output is bandpass filtered and summed with the I mixer Pound-server voltage to achieve both center frequency stabilization and broadband phase noise suppression.

Abstract: A fixed-geometry probe for exchanging microwave energy with a cavity resonator is easy to manufacture, reliable and readily adjustable external to the cavity to select a coupling coefficient. The probe includes a transmission line that enters, turns and exits the cavity resonator. A first end of the transmission line lies outside the cavity resonator for connection to a microwave circuit to exchange microwave energy. A portion of the transmission line's outer conductor(s) is removed within the cavity resonator to form a fixed-geometry radiating element to exchange microwave energy with the cavity resonator in accordance with the coupling coefficient. The line's outer conductor is connected to the cavity resonator on either side of the radiating element. A second end of the transmission line is terminated outside the cavity resonator with a terminating impedance creating a mismatch with the line's characteristic impedance to create a reflective stub.

Abstract: Described herein is an apparatus and a method for a low noise infinite radio frequency (RF) delayed-locked loop (DLL). The apparatus comprises a phase detector having a first input configured to receive a first RF signal, a second input, and an output; an infinite phase shifter having a first input configured to receive a second RF signal, an input bus, and an output connected to the second input of the phase detector; and a controller having a first input connected to the output of the phase detector and an output bus connected to the input bus of the infinite phase detector, wherein the output of the infinite phase shifter comprises a low noise signal in phase alignment with the first RF signal.

Abstract: A dual-loop phase-locking circuit combines a conventional phase-frequency-detector (PFD) and frequency-divider based first loop to lock an output signal frequency to a multiple of a reference signal frequency within a first loop bandwidth BW1 with a second loop to simultaneously lock the output signal phase to a second signal independently locked to the same multiple of the reference signal. The second loop integrates the phase error between the output signal and the second signal, and applies an offset at the PFD output in the first loop to reduce the first loop phase errors within a second loop bandwidth BW2 (<BW1). The first loop bandwidth BW1 can be optimized for overall phase-noise performance of the output signal while retaining the excellent capture and hold characteristics of that loop's topology. The second loop provides superior carrier-frequency phase alignment between the output signal and second signal.

Abstract: A reflective microstrip tuning circuit that operatively couples to another circuit to be tuned, in which tuning circuit receives an incident signal from the other circuit and enables adjustment of the amplitude and/or phase of the return signal reflected by the tuning circuit for use in the other circuit. The tuning circuit includes one or more cascaded couplers that divide power from the incident signal unequally among a plurality of adjustable tuning arms, in which the tuning arms may be individually adjusted to change the phase of the signal that is reflected by each arm so that both the amplitude and phase of the signal returned by the tuning circuit is adjusted to achieve the desired tuning result. The difference in the power that is divided among the tuning arms provides a progressive weighting to the adjustment effect of each tuning arm, which provides for a series of coarse through fine adjustments that enables a greater degree of resolution when tuning.

Abstract: A reflective microstrip tuning circuit that operatively couples to another circuit to be tuned, in which tuning circuit receives an incident signal from the other circuit and enables adjustment of the amplitude and/or phase of the return signal reflected by the tuning circuit for use in the other circuit. The tuning circuit includes one or more cascaded couplers that divide power from the incident signal unequally among a plurality of adjustable tuning arms, in which the tuning arms may be individually adjusted to change the phase of the signal that is reflected by each arm so that both the amplitude and phase of the signal returned by the tuning circuit is adjusted to achieve the desired tuning result. The difference in the power that is divided among the tuning arms provides a progressive weighting to the adjustment effect of each tuning arm, which provides for a series of coarse through fine adjustments that enables a greater degree of resolution when tuning.

Abstract: Embodiments of a microwave oscillator and method for amplitude noise reduction are generally described herein. The oscillator may include a resonator and an RF bridge to combine an incident and a reflected RF signal. The oscillator may further comprise an amplitude noise reduction loop, which may be configured to use a first baseband control signal to perform amplitude modulation (AM) of an oscillator feedback signal for reduction of amplitude noise on the oscillator output signal.