Alpha’s series of Sampling Phase Detectors (SPD’s) consist of a hybrid assembly of an SRD comb generator, coupling capacitors and microwave mixer diodes. This module makes an inexpensive way of phase locking a commercial VCO source to a low frequency stable reference. Each part in the series is optimized to operate in standard narrow band commercial systems. All units handle reference frequencies in the 50 to 500 MHz band. Component selection within Alpha allows us to minimize beat note output.

It is easiest to think of the SPD in its two constituent forms; a comb generator and subharmonic mixer.

The comb generator portion consists of the external reference, amplifier and impedance transformer. The external circuit matches into the low impedance of the SRD portion of the SPD. Careful attention to matching by setting the right transformer ratio, detuning the circuit with shunt capacitors will result in larger amplitude beat note signals.

The subharmonic mixer portion is the Schottky series pair. Various drive levels can be used to tailor intermodulation and beat note performance

The basic operation of a SPD is when the reference signal is fed into the SRD. This sets up a strong pulse, rich in harmonics that is used to strobe the mixer diodes on. The balanced mixer design converts the sampled oscillator signal and matching harmonics into an IF beat note. This signal can then be used in feedback loop to correct tuning voltage on the VCO

Typical applications include phase locking of oscillators in TVRO, VSAT, DBS and telecommunications markets.

Photos under microscope upon request

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