Crystal frequency monitor

Claim 2

Apparatus for determining the resonance frequency of a piezoelectric resonator comprising: a. a phase detector, said detector being effective to produce zero output when two coherent signals applied to its input are in quadrature; b. two signal paths, including a resonator in one thereof, connectable at one end for receiving a signal from an external signal source, and connected at the other end to said phase detector, said signal paths comprising transmission lines having a net length difference of less than (1/4 + n/2) lambda and more than approximately (0.005 + n/2) lambda between the two signal paths, where lambda is the wavelength and n any number of the integer sequence 0,1,2,3,.... c. a variable complex impedance terminating one of said transmission lines, and being effective to adjust the phase shift between the two signals applied to said phase detector to 90 degrees.

Claim 3

Apparatus according to claim 1, where said net length difference between the transmission lines forming the two signal paths is less than lambda /4 and more than approximately 0.005 lambda , where lambda is the wavelength.

Claim 4

Apparatus according to claim 1, (wherein the output of the phase detector) and signal indicator means connected to the output of said phase detector and effective to indicate the occurrance of resonance of said resonator.

Claim 5

Apparatus according to claim 1, (wherein the output of the phaSe detector) and voltage sensitive switching means connected to the output of said phase detector and effective to control the frequency adjustment process of said resonator.

Claim 6

Apparatus according to claim 1, wherein the frequency of said signal source is voltage controllable (and wherein a voltage proportional to the output voltage of said detector is applied), and signal transmitting means connectable between the detector output and the signal source, effective to apply a voltage proportional to the output of said detector to said signal source in order to phase lock the signal frequency to the resonator frequency.

Claim 7

Apparatus according to claim 5, (with means for providing switching action when the resonator frequency reaches a predetermined value, said switching action being effective to control the frequency adjustment process) and frequency sensitive switching means effective to sense the difference between the resonator frequency and a preset target frequency and to terminate a resonator frequency adjustment process when said frequency difference is zero.

Claim 8

Apparatus according to claim 1 (wherein the output of the phase detector is effective to provide) and voltage and frequency measuring means effective to determine the ratio of a voltage increment of the detector output to the corresponding frequency increment of the signal source, this ratio providing a measure of the equivalent series resistance of a resonator.

Claim 9

Apparatus for determining the resonance frequency of a piezoelectric resonator, comprising: a. a phase detector, said detector being effective to produce zero output when two coherent signals applied to its input are in quadrature; b. a signal splitter having an input terminal and two output terminals, said input terminal being connectable to an external signal source and said output terminals being effective to provide two coherent signals 90 degrees out of phase; c. two signal paths, including a resonator in one thereof, each said signal path being connectable at one end to one output of said signal splitter, and connected at the other end to one input of said phase detector, said signal paths comprising transmission lines and having substantially equal phase shift; d. a variable complex impedance terminating one of said transmission lines, and being effective to adjust the phase shift between the two signals applied to said phase detector to 90*. e. means for indicating the output voltage of said detector and for providing electrical switching action at a predetermined level of said output voltage.

Claim 10

Apparatus for determining the resonance frequency of a piezoelectric resonator, comprising: a. a phase detector, said detector being effective to produce zero output when two coherent signals applied to its input are in quadrature; b. a signal splitter having an input terminal and two output terminals, said input terminal being connectable to an external signal source and said output terminals being effective to provide two coherent signals 90 degrees out of phase; c. two signal paths, including a resonator in one thereof, each said signal path being connectable at one end to one output of said signal splitter, and connected at the other end to one input of said phase detector, said signal paths comprising transmission lines and having substantially equal phase shift; d. a variable complex impedance terminating one of said transmission lines, and being effective to adjust the phase shift between the two signals applied to said phase detector to 90*. e. means for indicating the output voltage of said detector and for providing electrical switching action at a predetermined level of said output voltage.