Periodic signal generators having microelectromechanical resonators therein that support generation of high frequency low-TCF difference signals

A periodic signal generator, comprising:

• an oscillator comprising at least one microelectromechanical bulk acoustic resonator having a piezoelectric layer therein and drive and sense electrodes on the piezoelectric layer, said oscillator configured to generate first and second periodic signals having unequal first and second frequencies (f1, f2), said first and second periodic signals characterized by respective first and second temperature coefficients of frequency (TCf1, TCf2) that differ by at least about 5 ppm/° C.;
• a frequency multiplier responsive to the first periodic signal, said frequency multiplier configured to generate a periodic output signal having a frequency equal to N times a frequency of the first periodic signal, where N is a positive real number;
• and
• a mixer circuit configured to generate a periodic beat signal in response to the second periodic signal and the periodic output signal, said periodic beat signal having a frequency fb equal to f2−Nf1 and a temperature coefficient of frequency (TCfb) of less than a smaller of the absolute value of TCf1 and TCf2.