METHOD AND APPARATUS FOR INCREASING DISTRIBUTION OF JITTER WITHIN A RANDOM NUMBER GENERATOR

• US 20110169579A1
• Filed: 11/30/2010
• Published: 07/14/2011
• Est. Priority Date: 01/08/2010
• Status: Abandoned Application

• Current Assignee: MediaTek Singapore Pte. Ltd. (MediaTek, Inc.)
• Original Assignee: MediaTek Singapore Pte. Ltd. (MediaTek, Inc.)
• Inventors: Dodrill, James
• Application Number:
  US12/957,290
• Publication Number:
  US 20110169579A1
• Time in Patent Office: Days
• US Class Current: 331/46
• CPC Class Codes: G06F 7/588 Random number generators, i.e. based on natural stochastic processes
• CPC Class Codes: H03K 3/84 Generating pulses having a predetermined statistical distribution of a parameter, e.g. random pulse generators

Abstract

A random number generator comprises a first high frequency (HF) oscillator, a second low frequency (LF) oscillator, a delay buffer, a multiplexer, and a sampling circuit. The HF oscillator generates a high frequency oscillating signal. The LF oscillator generates a low frequency oscillating signal. The multiplexer selects from the LF oscillating signal and one or more delayed version of the LF oscillating signal to generate a third oscillating signal. The third oscillating signal is then used to sample the HF oscillating signal to output a random bit stream. In one preferred embodiment, the random bit stream is feedback to the multiplexer to make randomized selection. As a result, the original jitter distribution of the LF oscillating signal is increased to a larger jitter distribution of the third oscillating signal to increase the random behavior of the output bit stream.

Claims

1. A random number generator, comprising:

a first oscillator that outputs a first oscillating signal;

a second oscillator that outputs a second oscillating signal, wherein the second oscillating signal has a much lower frequency than the first oscillating signal; and

a sampling circuit that samples the high frequency oscillating signal using a third oscillating signal, and in response generates a sequence of random bits, wherein the third oscillating signal is selected from the second oscillating signal and one or more delayed versions of the second oscillating signal.

2. The random number generator of claim 1, wherein the third oscillating signal is selected based on the sequence of random bits.

3. The random number generator of claim 2, further comprising:

a delay buffer that receives the second oscillating signal and outputs a delayed version of the second oscillating signal; and

a selection circuit that selects from the second oscillating signal and the delayed version of the second oscillating signal based on the sequence of random bits.

4. The random generator of claim 3, wherein the second oscillating signal has a jitter distribution due to thermal noise, and wherein the thermal noise is a true random source.

5. The random number generator of claim 4, wherein the delay buffer and the selection circuit are used such that the third oscillating signal has a larger jitter distribution than the second oscillating signal.

6. The random number generator of claim 4, wherein multiple delay buffers and multiplexers are used such that the third oscillating signal has a larger jitter distribution than the second oscillating signal.

7. The random number generator of claim 1, wherein the sampling circuitry is either a phase detector or a D-type Flip-Flop.

8. The random number generator of claim 1, wherein the sampling circuit further comprises a corrector for assuring the sequence of random bits has approximately equal number of zeros and ones on average.

9. A method for generating a sequence of random bits, comprising:

generating a first high frequency oscillating signal by a first oscillator;

generating a second low frequency oscillating signal by a second oscillator;

generating a third oscillating signal by selecting from the second oscillating signal and one or more delayed versions of the second oscillating signal; and

generating a sequence of random bits by sampling the first oscillating signal using the third oscillating signal.

10. The method of claim 9, wherein the third oscillating signal is selected based on the sequence of random bits.

11. The method of claim 10, wherein the generating of the third oscillating signal further comprises:

receiving the second oscillating signal by a delay buffer and in response outputting a delayed version of the second oscillating signal; and

selecting from the second oscillating signal and the delayed version of the second oscillating signal by a selection circuit based on the sequence of random bits.

12. The method of claim 11, wherein the second oscillating signal has a jitter distribution due to thermal noise, and wherein the thermal noise is a true random source.

13. The method of claim 12, wherein the delay buffer and the multiplexer are used such that the third oscillating signal has a larger jitter distribution than the second oscillating signal.

14. The method of claim 12, wherein multiple delay buffers and multiplexers are used such that the third oscillating signal has a larger jitter distribution than the second oscillating signal.

15. The method of claim 9, wherein the sampling circuit is either a phase detector or a D-type Flip-Flop.

16. The method of claim 9, wherein the sequence of random bits is corrected to have approximately equal number of zeros and ones on average.

17. An oscillator, comprising:

a ring oscillator that generates a first oscillating signal;

a delay buffer that receives the first oscillating signal and outputs a delayed version of the first oscillating signal; and

a selection circuit that outputs a second oscillating signal by selecting from the first oscillating signal and the delayed version of the first oscillating signal based on a sequence of random bits, wherein a jitter distribution of the second oscillating signal is larger than a jitter distribution of the first oscillating signal.

18. The oscillator of claim 17, wherein the ring oscillator comprises a plurality of inverters, each inverter comprises a number of transistors.

19. The oscillator of claim 18, wherein the first oscillating signal has the jitter distribution due to thermal noise present in the transistors of the ring oscillator, and wherein the thermal noise is a true random source.

20. The oscillator of claim 17, wherein the second oscillating signal is used to sample a high frequency oscillating signal to generate the sequence of random bits.