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Physics in Application

Innovative Astro Tegnologies:

  1. Low Noise Amplifiers

A novel Low Noise Amplifier (LNA) technique for radio telescopes (such as the planned SKA), that has lower noise over much broader bandwidths and at higher temperatures than standard LNA's, was developed. Due to the broad bandwidth, this technique makes it possible to bring the sensitivity of radio telescopes to that of commercial measuring instruments such as oscilloscopes and spectrum analysers.

South Africa has been selected to host a large part of the world’s largest radio telescope, the Square Kilometer Array. One of the critical components determining the sensitivity of such telescopes is the low noise amplifiers: It has to amplify the tiny signals detected by a radio telescope, without swamping the signal in the electronic noise that the amplifier generates itself.

Current LNA are good at achieving low noise at narrow bandwidths. However, for broad bandwidths, as required by the SKA, it is very challenging to achieve a low noise over all bandwidths.

By using multiple transistors in parallel in a special way (see figure for an example), low noise can be achieved over arbitrary bandwidths by increasing the number of transistors as the bandwidth increase. The technique has the additional advantages of low cost (by using cheap commercial transistors) and low power consumption compared to standard broadband LNAs.

Because of the low cost, these novel low noise amplifiers can also be used as pre-amplifiers in broadband measuring equipment such as oscilloscopes and spectrum analysers, making the low noise level of radio telescopes available to such instruments.

Articles & Patents:

 

  1. High efficiency power supplies

For calibration of air Cherenkov gamma-ray telescopes in Potchefstroom, fast (nano-second) high power pulses were required, which could not be achieved using normal power devices such as MOSFETs. However, a technique was found to switch the device much faster that normally, enabling it to achieve the short pulses required. It was then realised that this technique can be used in various applications, such as ozone generators, automotive ignition systems etc. The novelty of the technique resulted in several patents being granted in the US (and other countries):

 

  1. Fast switching MOSFET technique:

A fast switching MOSFET technique was developed to generate fast pulses to calibration gamma-ray telescopes. The innovative technique make it possible to switch commercial MOSFETs much faster than in normal applications. Spin-offs of this technique are currently being deployed in various commercial applications such as:

  • High efficient ozone generators
  • High energy plasma and spark discharge automotive ignitions systems
  • Electric fence high voltage generators
  • Ion drive systems and plasma generators

What is a MOSFET?

A MOSFET (Metal Oxide Field Effect Transistor) is used as a switching device in electronic circuits, for instance, almost all electronic devices (such as TV's, computers, VCR, cellphones, induction heaters and other industrial equipment) have a power supply. Almost all of these power supplies use MOSFETs as switching devices.

Current MOSFET disadvantages

Current MOSFET designs have a typical "turn-on" and "turn-off" time (a period after the device has been switched on/off and before it is 100% switched on/off) of about 20 ns. This could be too long for some fast switching / detecting applications.

During the rise and fall time, unwanted heat is generated by the MOSFET, which means that energy is wasted. Getting rid of this unwanted heat mostly calls for expensive, heavy and bulky metal heat sinks.

  1. New Patent

A new patent has been filed by the North-West University (Potchefstroom Campus), which reduces this Turn-on and turn-off time by a factor of up to 10 times, as shown in the graph below. This means the energy loss, mentioned above can also be significantly reduced. The applications in which this patent is used:

  • can be made smaller, lighter and less expensive;
  • use less power (energy); and
  • have prolonged battery life

The patent constitutes an arrangement of standard electronic components in conjunction with a standard MOSFET.

Possible applications:

The following are some examples and benefits that can be achieved by using this new patent:

  1. Synchronous power supplies:
  • Smaller, more efficient and reliable power supplies for laptops, PCs, cell phones, TVs, spacecraft, etc.
  • In certain applications, replacing bulky transformers with electronic circuits thereby reducing cost and space
  1. Induction heating:
  • Reduces size, weight, volume and power consumption of new designs for:
    • Domestic appliances (stoves, kettles, geysers, etc.)
    • Industrial appliances (welding machines, metal melting facilities)
  1. Automotive ignition systems:
  • The replacement of ignitions coils with electronics the size of a spark plug, with the following added advantages:
    • More accurate timing with the duration and intensity of the spark controllable
    • Better combustion stability, resulting in fuel saving and cleaner exhaust gas.
  1. Chemical processing:
  • Ozone generators (already proved) for sterilising applications such as water treatment.
  1. Measurement instruments:
  • High speed and precision instruments

 

  1. Automotive Ignition System

Two automotive ignition systems are currently being industrialised by a commercial partner, a system using a standard sparkplug and a plasma ignition system.

The spark plug ignition system has been tested at various international testing facilities. Its main features are:

  • Power-enhanced spark
    • Variable spark intensity up to hundreds of milli Joules(Normal system deliver about 2mJ)
  • Immediate spark when required
    • Almost no charging time, can produce a 'continuous' spark
    • Guaranteed immediate combustion with every cycle
  • Reliable spark
    • Independent units for each cylinder
    • When one fails the other is still functional
  • Energy efficient spark
    • Less than 20% energy loss (compared to about 99% loss normally)
  • Unique spark
    • Protected by US Patents (6870405, 8063426,  8191540,  8354911).
  • Small and cheap system
    • Totally eliminate large high voltage coils and cables
  • Radio silent system
    • Fully shielded unit, giving minimal EM radiation

There are several existing plasma ignition systems that have shown plasmas to give even better ignition performance that high power sparks.

However, the complexity and cost of such systems has been a barrier to enter the market.

By using the patented MOSFET drive techniques, a cheap and reliable plasma ignition system was demonstrated and are currently being commercialised.

6.      Mobile Neutron Monitors

Cosmic rays are produced by supernova explosions and high energy objects such as neutron stars and black holes.  

These high-energy particles hitting earth from space consist of 90% protons, 9% Helium nuclei and 1% heavier nuclei.

Upon striking the upper atmosphere of the earth, they produce many different types of secondary particles.

With incident cosmic ray energy >1GeV, particles can penetrate to ground level. Neutron monitors are used to detect and count the neutron component at ground level. These Neutron monitors are normally bulky (weighting a few tons) and power hungry (use more than 1000 W).

7.      Mobile Calibration Monitor

A mobile calibration NM was designed and built in 2001/2002, weighting only 300 kg with a power consumption of about 100 Watt. It is used as a calibration platform for fixed NMs worldwide and had done several trips on U.S. Coast Guard ships with latitude surveys.

8.      Mini Neutron Monitor

A next generation mobile NM, called the mini neutron monitor, is currently being developed, having the following specifications:

  • Electronics Head Small (Easily shipped / exchanged - 1kg, 110x110x110 mm) and inexpensive (~ R4500 = € 450).
  • Inexpensive - Complete, single tube NM for approx. € 15000.
  • Solid state reliability – No moving parts.
  • IP 63 Rating – Protection from water and dust ingress.
  • Internal battery backup provides continuous power supply.
  • Internal data backup on high durability flash-drive.
  • Inter-connectable via LAN, easily install and setup complete NM.
  • Remote management of stations/networks.
  • Fully adaptable and versatile system
  • User friendly interface: Easily configured, easily manage, interpret data.

9.      Hardware random number generator

For the detection of pulsars (fast rotation magnetised neutron stars) a statistical test, called the H-test is normally used. However, to prevent false detection, the H-test must be calibrated using a large set of truly random numbers. In order to achieve this, a very high speed, low cost, random number generator (RNG) was developed.

This RNG makes use of electronic noise generated by a quantum process and a special correction algorithm to generate true random numbers at a very high rate.

The RNG’s are also ideal for use in cryptographic algorithms, computer games and Monte-Carlo simulations. For commercialisation, the RNG's are currently being implemented in a USB “plug and play” version that can be plugged into any computer and used as a source of random numbers.