On Mon, 22 Jun 1998 12:14:17 +0800 Regulus Berdin writes: >> From: Tjaart van der Walt >SNIP >> I have a feeling finding 1GHz counters won't be easy. You could >probably >> use an array of /2 prescalers and try to gate the signal, but it >won't be >easy. > >On my case, the value inside the prescaler was not needed. Single-stage (divide by 2) prescalers are made. You could connect a few in series as a ripple counter and have a way to read out the count. After the first few stages the frequency would be low enough for ordinary digital counters, including possibly the PIC's timer. The count-reading circuit can be slow since it would only be used while the count is stopped. It also isn't necessary to reset the counter, just subtract the previous reading from the next one. Probably the gate could be implemented by just throwing the DC bias of the first stage off so it doesn't count, or clamping the 1 GHz clock to ground with a diode. A 1 GHz oscillator can be built with a bipolar transistor. The frequency could be stabilized by any conventional PLL chip used for radio and TV tuning. If a really stable frequency is needed, use a low frequency crystal and multiply up. It is generally folly to attempt to measure distances along the ground by radar. Radio signals reflect off of everything, including the ground itself. Even with the ideal conditions of perfectly flat terrain, there will still be two paths to the target, one direct and one having taken a bounce off the ground at the halfway point. These path distances and signal strengths can be very close to the same and hard to resolve. Usually such measurements are taken by light, using laser beams and/or telescope optics to produce a single path to a specific target. The range-determining methods are the same as used in radar; pulses, chirps, multiple CW frequencies, etc. For light of course the ranging signal is applied as AM to the light. _____________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com Or call Juno at (800) 654-JUNO [654-5866]