FAST PULSE GENERATOR

Abstract

A pulse generator is disclosed. The pulse generator can include a pulsed switch, such as a diode. The pulsed switched can be connected between an input source, such as an oscillator and a frequency multiplier.

Claims

1. A pulse generator including: an ac source for providing an ac signal; a pulsed switch connected to an output of the ac source; a non-linear frequency multiplier connected to an output of the switch; wherein the pulsed switch is adapted or configured to generate a pulsed ac signal at the output of the switch so that pulses are applied to the non-linear frequency multiplier, wherein the non-linear frequency multiplier shortens the pulses.

2. A pulse generator as claimed in claim 1, being included in a radar system.

3. A pulse generator as claimed in claim 1, wherein the switch comprises a mixer.

4. A pulse generator as claimed in claim 1 including at least one amplifier.

5. A pulse generator as claimed in claim 1 comprising at least one amplifier, the at least one amplifier being provided between the pulsed switch and the frequency multiplier.

6. A pulse generator as claimed in claim 5, wherein the switch is a mixer and the at least one amplifier is provided between the mixer and the frequency multiplier

7. A pulse generator as claimed in claim 1 wherein the pulsed switch is a semiconductor diode.

8. A pulse generator as claimed in claim 1 wherein a plurality of frequency multipliers is provided and the pulsed switch is provide between adjacent such multipliers.

9. A pulse generator as claimed in claim 1 comprising at least one amplifier and a plurality of frequency multipliers, wherein at least one amplifier is provided between two of the multipliers.

10. A pulse generator as claimed in claim 1 comprising at least one amplifier, wherein at least one amplifier is connected to an output of the frequency multiplier.

11. A radar system that includes the pulse generator as claimed in claim 1.

12. A radar-based collision avoidance system that includes the pulse generator as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various aspects of the invention will now be described by way of example only and with reference to the accompanying drawings, of which:

[0013] FIG. 1 shows a conventional radio frequency switch pulse generator;

[0014] FIG. 2 is block diagram of a pulse generator;

[0015] FIG. 3 is modified version of the pulse generator of FIG. 2;

[0016] FIG. 4 is another modified version of the generator of FIG. 2;

[0017] FIG. 5 is yet another modified version of the generator of FIG. 2, and

[0018] FIG. 6 is still another modified version of the generator of FIG. 2.

DETAILED DESCRIPTION

[0019] FIG. 2 shows a pulse generator 10 including a pulsed switch 12 connected between an oscillator 14 and a frequency multiplier 16. Any suitable oscillator 14 could be used, provided it is able to drive the frequency multiplier non-linearly 16. The multiplier 16 may include one or more non-linear devices, for example one or more varactor diodes, FETs, bipolar or other types of diode. Although FIG. 2 shows only a single frequency multiplier 16, there may be a plurality of these, with the pulsed switch 12 connected between adjacent multipliers, as shown in FIG. 3. The pulsed switch 12 may be a semiconductor device or a mixer means, for example, a diode or a four-quadrant multiplier or double balanced mixer or any other relatively fast switch. In any case, the switch 12 may be operable to produce bi-phase pulses. Alternatively, the switch 12 may be operable to produce multi-phasic pulses.

[0020] Because the multiplier 16 of FIGS. 2 and 3 is a nonlinear device that only conducts above a threshold and saturates very quickly, an effective sharpening of the pulse edges is observed. In practice, this means that the pulses are shorter and so faster.

[0021] Various device configurations have been tested. In one example, the oscillator 14 was a YIG (Yttrium Iron Garnet) oscillator tunable from 6.8 to 8.8 GHz with a power output of +15 dBm, followed by a varactor diode multiplier chain. The gating switch pulse width was 600 ps at about 100 MHz. This provided output pulses having a width of 260 ps at 94 GHz. In another example, the oscillator used was a dielectric resonator oscillator, which provided a fixed frequency of 7.833 GHz, followed by a varactor diode multiplier chain. In this case, the gating switch pulse width was 1 ns at about 100 MHz and the output pulses had a width of 650 ps at 94 GHz. These examples are by no means exclusive, but instead are provided for the purposes of illustrating the benefits of the invention. The type of oscillator and required output power are dependant only upon system requirements.

[0022] The pulse generator in which the invention is embodied can be used for many applications, particularly radar applications. For example, the invention could be of particular use in radar based collision avoidance systems. Because of the very high speeds achievable using the generator, the accuracy and resolution of such systems would be greatly improved.

[0023] A skilled person will appreciate that variations of the disclosed arrangements are possible without departing from the invention. For example, because processing by the frequency multiplier will reduced the pulse signal amplitude, at least one amplifier 18 may be provided for recovering that pulse amplitude. This may be provided between the pulsed switch 12 and the frequency multiplier 16, as shown in FIG. 4. Where a plurality of frequency multipliers 16 is provided, the amplifier 18 may provided between two of these multipliers 16, as shown in FIG. 5. Alternatively or additionally, the amplifier 18 may be connected to an output of the frequency multiplier 16, as shown in FIG. 6. Accordingly the above description of the specific embodiment is made by way of example only and not for the purposes of limitation. It will be clear to the skilled person that minor modifications may be made without significant changes to the operation described.