A phase rotator calibration system is provided. The phase rotator calibration system includes a phase rotator portion having input for receiving an input signal and an output for providing an output signal. A calibration portion is coupled to the phase rotator portion. The calibration portion is configured to determine a phase error based on a phase estimation. The phase estimation is generated by way of an arccosine function.

A front-end circuit is used to test an RF signal from an RF device. The RF signal is generated by modulating a carrier signal having a carrier frequency with a wideband baseband signal. A variable frequency oscillator generates a local signal having a variable local frequency. The first frequency mixer frequency mixes a local signal and an RF signal to generate an IF signal having a frequency. A band-pass type first filter filters the IF signal. The local frequency can be selected from a plurality of frequencies having a frequency interval equal to or narrower than a bandwidth of the first filter.

A phase coherent synthesizer with good phase noise and spurious performance is described. The phase coherent synthesizer includes digital direct synthesizer (DDS) circuitry, frequency multiplier circuitry, an oscillator, and a mixing stage. The digital direct synthesizer (DDS) circuitry has a first output and a second output. The first output is associated with a fine resolution synthesis. The second output is associated with a step synthesis. A second output signal provided via the second output has a higher frequency compared with a first output signal provided via the first output. The frequency multiplier circuitry is connected with the second output. The frequency multiplier circuitry is configured to multiply the second output signal received via the second output, thereby generating a multiplied output signal. The mixing stage has two input ports connected with the frequency multiplier circuitry and the oscillator respectively. The mixing stage includes, for example, circuitry configured to mix the multiplied output signal and an oscillator output signal of the oscillator, thereby generating an intermediate frequency signal. The first output signal and the intermediate frequency signal are synchronized with each other.

A phase coherent synthesizer with good phase noise and spurious performance is described. The phase coherent synthesizer includes digital direct synthesizer (DDS) circuitry, frequency multiplier circuitry, an oscillator, and a mixing stage. The digital direct synthesizer (DDS) circuitry has a first output and a second output. The first output is associated with a fine resolution synthesis. The second output is associated with a step synthesis. A second output signal provided via the second output has a higher frequency compared with a first output signal provided via the first output. The frequency multiplier circuitry is connected with the second output. The frequency multiplier circuitry is configured to multiply the second output signal received via the second output, thereby generating a multiplied output signal. The mixing stage has two input ports connected with the frequency multiplier circuitry and the oscillator respectively. The mixing stage includes, for example, circuitry configured to mix the multiplied output signal and an oscillator output signal of the oscillator, thereby generating an intermediate frequency signal. The first output signal and the intermediate frequency signal are synchronized with each other.

A magnetoresistive mixer, comprising a spiral coil, a bridge-type magnetoresistive sensor and a magnetic shielding layer, wherein the spiral coil is located between the bridge-type magnetoresistive sensor and the magnetic shielding layer. Four tunnel magnetoresistive sensor units forming the bridge-type magnetoresistive sensor respectively contain N array-type magnetic tunnel junction rows. The magnetic tunnel junction rows are connected in series, parallel, or combination of series and parallel connections to form two port structures. The four tunnel magnetoresistive sensor units are respectively located in two regions of the spiral coil having opposite current directions, sensing axes of magnetic tunnel junctions are perpendicular to the current directions, and in addition, the distribution characteristics of magnetic fields in directions of the sensing axes of the tunnel magnetoresistive sensor units to the magnetic field in the two regions are opposite, and the distribution characteristics in a single region are the same. The first frequency signal is input through the two ends of the spiral coil, the second frequency signal is input between the power and -ground ports of the bridge-type magnetoresistive sensor, and mixing signals are output through a signal output end of the bridge-type magnetoresistive sensor. The magnetoresistive mixer has the characteristics of good linearity, good input signal isolation, and low power consumption.

A magnetoresistive mixer, comprising a spiral coil, a bridge-type magnetoresistive sensor and a magnetic shielding layer, wherein the spiral coil is located between the bridge-type magnetoresistive sensor and the magnetic shielding layer. Four tunnel magnetoresistive sensor units forming the bridge-type magnetoresistive sensor respectively contain N array-type magnetic tunnel junction rows. The magnetic tunnel junction rows are connected in series, parallel, or combination of series and parallel connections to form two port structures. The four tunnel magnetoresistive sensor units are respectively located in two regions of the spiral coil having opposite current directions, sensing axes of magnetic tunnel junctions are perpendicular to the current directions, and in addition, the distribution characteristics of magnetic fields in directions of the sensing axes of the tunnel magnetoresistive sensor units to the magnetic field in the two regions are opposite, and the distribution characteristics in a single region are the same. The first frequency signal is input through the two ends of the spiral coil, the second frequency signal is input between the power and -ground ports of the bridge-type magnetoresistive sensor, and mixing signals are output through a signal output end of the bridge-type magnetoresistive sensor. The magnetoresistive mixer has the characteristics of good linearity, good input signal isolation, and low power consumption.

Aspects of the present disclosure are directed to injection locking and related apparatuses. As may be implemented in accordance with one or more embodiments, an apparatus includes a plurality of injection-locking circuits configured to receive an injection signal, each injection-locking circuit including a mixer and a lock-detection circuit. In each of the injection-locking circuits, the lock-detection circuit detects a lock-status relationship between the injection signal and a signal output from the injection-locking circuit. In response to the lock-status relationship indicating an unlocked condition, a phase/magnitude of the injection signal is adjusted. In response to the lock-status relationship indicating a locked condition, transmission of an FM continuous wave (FMCW) chirp signal is facilitated.

Aspects of the present disclosure are directed to injection locking and related apparatuses. As may be implemented in accordance with one or more embodiments, an apparatus includes a plurality of injection-locking circuits configured to receive an injection signal, each injection-locking circuit including a mixer and a lock-detection circuit. In each of the injection-locking circuits, the lock-detection circuit detects a lock-status relationship between the injection signal and a signal output from the injection-locking circuit. In response to the lock-status relationship indicating an unlocked condition, a phase/magnitude of the injection signal is adjusted. In response to the lock-status relationship indicating a locked condition, transmission of an FM continuous wave (FMCW) chirp signal is facilitated.

A technique relates to a pulse shaping of microwave signals. A nondegenerate mixing device receives signals and a time-varying magnetic flux via input ports. The nondegenerate mixing device uses the signals and the time-varying magnetic flux to generate an output signal on an output port, the output signal having a waveform profile set by the time-varying magnetic flux.

A non-contact self-injection-locked vital sign sensor is disclosed, which includes transmitting antenna, receiving antenna, self-injection-locked integrated circuit and demodulator. The self-injection-locked integrated circuit includes voltage-controlled oscillator, mixer, two amplifiers and harmonic-frequency power combiner. A frequency-multiplied signal is produced by amplifiers and harmonic-frequency power combiner then transmitted to a living body by transmitting antenna. A frequency-divided signal is produced by voltage-controlled oscillator and mixer then transmitted to voltage-controlled oscillator, then a frequency- and amplitude-modulated signal is produced by the voltage-controlled oscillator then transmitted to demodulator to produce a vital sign. So as to detect vital sign with a higher frequency to increase measurement sensitivity by using a low-cost integrated circuit process. A centrifugal compressor includes a volute base block, a volute cover plate, an impeller, a diffuser-adjusting assembly, a radial constraint assembly, an axial constraint assembly and a driving assembly.