Design of a Saw Oscillator at a Harmonic Frequency

Abstract

<p>The use of harmonic mode SAW filters allows the fabrication of UHF oscillators with standard lithographic techniques. However, such devices previously required external filtering to select the desired harmonic. This in turn requires relatively high O circuits with their associated alignment problems and phase sensitivity.</p> <p>This thesis discusses a technique which permits harmonic operation without the external circuitry. By utilizing the theory of the end-fire array antenna a stepped-delay line has been fabricated at frequencies greater than 400 MHz using the fifth harmonic (i.e. fundamental at 80 MHz). The result is a packaged SAW oscillator which exhibited an output power of -15 dBm into a 50 Ω termination at a harmonic frequency of 404.3 MHz. Short term stability measurements made yield a short term stability of better than 1 part in 10⁹ over a period of 1 sec.</p>