> Date: Wed, 19 Jul 2006 20:03:11 -0400 > From: "Hill, John" <[email protected]>
> Mike, [...] > The purpose of the patent was to document the balanced oscillator > circuit used in Keyless Entry Transmitters. This circuit produced > the same radiated power with half the battery voltage. That is > what my employer was interested in patenting. The circuit had been > used to drive mixers so some features of the circuit could not be > claimed in our patent. The doubling of the Q was one such feature. > The mixer circuit already had a doubled Q. > The manufacturing guys liked the circuit because it had a higher > yield. > This was because of the higher Q of the overall circuit. The Q is > doubled due to the RF ground that gets formed in the center of the > Crystal. > As you point out the two Colpitts sections look like standard > Colpitts oscillators. And in fact they are just standard Colpitts > oscillators, but they share a single crystal (SAW Resonator) > between them. The series resistance of the crystal is shared > between the two oscillators. Note the two sections are 180 degrees > out of phase. Each Colpitts section gets half of the series > resistance and hence the Q of the overall circuit is doubled. > This circuit is an example of how the Q of a circuit can be > manipulated. Q is just the resistive loss of a circuit. > My point was to encourage Xilei not to consider Q fix by some act > of Mother Nature. It can be controlled and manipulated. > Best regards, > John John, Your circuit does not double the Q of the crystal. You have placed the Thevenin equivalent of two bias networks R5,R6 and R7,R8 in series with the crystal series resistance. This will drastically reduce the Q of the crystal. I am not even sure it will oscillate reliably. Please see my paper on using SPICE to analyze crystal oscillators. Check the section on measuring the loaded Q of the crystal. Regards, Mike Monett Antiviral, Antibacterial Silver Solution: http://silversol.freewebpage.org/index.htm SPICE Analysis of Crystal Oscillators: http://silversol.freewebpage.org/spice/xtal/clapp.htm Noise-Rejecting Wideband Sampler: http://www3.sympatico.ca/add.automation/sampler/intro.htm -- The Silver List is a moderated forum for discussing Colloidal Silver. Instructions for unsubscribing are posted at: http://silverlist.org To post, address your message to: [email protected] Address Off-Topic messages to: [email protected] The Silver List and Off Topic List archives are currently down... List maintainer: Mike Devour <[email protected]>
