Tunnel searcher location and communication equipment

• US 3,906,504 A
• Filed: 10/08/1969
• Issued: 09/16/1975
• Est. Priority Date: 10/08/1968
• Status: Expired due to Term

• Current Assignee: Allan Guster, Jeffrey E. Patterson
• Original Assignee: Allan Guster, Jeffrey E. Patterson
• Inventors: Guster, Allan, Patterson, Jeffrey E.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Berger, Richard E.
• Application Number:
  US04/866,794
• Time in Patent Office: 2,169 Days
• Field of Search: 343/112,112D,719 325/28 324/47
• US Class Current: 342/459
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems

Abstract

A method of locating and plotting tunnels by moving a portable receiving unit in which is an orientatable coil over an area to be searched while locating a transmitting unit in the tunnel itself, transmitting a signal from the transmitting unit which has a short pulse duration but a considerably longer interval between pulses, and measuring the distance between the transmitter and receiver by amplitude calculation, means being provided also to measure the relative angle of the receiver in relation to the transmitter by orientating the coil to permit depth and position calculation to be determined.

Claims

1. A method of locating and plotting tunnels which consists of moving a portable electromagnetic induction field receiving unit, containing a coil which can be orientated, over an area to be searched, locating a transmitting unit in the tUnnel to give pulsed eliptical field lines, determing the location of the transmitter by measuring the horizontal and vertical components of the pulsed field to derive the depth and offset distance of the transmitter in relation to the receiver, and determining direction of the receiver by further orientation of the said coil in the said pulsed field.

2. The method of claim 1 wherein the transmitting unit operates on signals of short pulse duration, using a switched regulator which is switched off during the transmitted pulse periods and including a capacitor which supplies the power for the transmit output pulse and is replenished from batteries via the said regulator during the periods between pulses.

3. The method of claim 2 wherein the pulse duration is approximately 2.5ms at a repetition rate of approximately 2 pulses per second.

4. The method of claim 2 wherein said coil has a resistance and the said regulator is controlled from a temperature dependent reference to compensate for changes in coil resistance with temperature.

5. The method of claim 1 wherein a gated signal is used and the magnetic field from the said transmitter induces a voltage in a broadly tuned receive coil and the signal is applied to a narrow band filter and then amplified in a balanced low noise amplifier and the pulses are then peak-detected to produce a direct current pulse the amplitude of which is proportional to the positive peak of the input signal, the said direct current pulse being then processed by analogue stages to produce an output signal which is directly related to the distance being measured.

6. The method of claim 5 wherein a first logarithmic analogue stage is followed by a one third gain amplifier, and an anti-logarithmic amplifier having a characteristic inverse to the first said stage, whereby the computation allows a display of the inverse cube law function as a proportional metre indication.

7. The method of claim 2 wherein voice communication is included using the same magnetic field at a power level wherein the pulses which control the gating of magnetic field used for location are used also to inhibit the communications while the location field pulse is being transmitted.

8. The method of claim 1 wherein two-way voice communication is achieved by frequency modulation and wherein a single coil in the transmitting unit is used for both location and communication.

9. The method of claim 1 wherein both modulation and demodulation of voice communication is achieved by the use of a common phase locked loop circuit in each of the transmitting and receiving units.