Impulse radio-based ultra wideband (IR-UWB) system using 1-bit digital sampler and bit decision window

• US 7,822,161 B2
• Filed: 05/22/2007
• Issued: 10/26/2010
• Est. Priority Date: 09/01/2006
• Status: Active Grant

• Current Assignee: Korea Electrotechnology Research Institute
• Original Assignee: Korea Electrotechnology Research Institute
• Inventors: Lee, Soon Woo, Kim, Kwan Ho, Park, Hae Soo, Lee, Won Tae, Park, Young Jin
• Primary Examiner(s): Ghebretinsae; Temesghen
• Application Number:
  US11/805,239
• Publication Number:
  US 20080056419A1
• Time in Patent Office: 1,253 Days
• Field of Search: 375/355, 375/219, 375/256, 375/130, 455/550.1
• US Class Current: 375/355
• CPC Class Codes: H04B 1/71632 Signal aspects H04B1/7172 and H04B1/7176 take precedence
• CPC Class Codes: H04B 1/71635 Transmitter aspects H04B1/7174 takes precedence
• CPC Class Codes: H04B 1/71637 Receiver aspects H04B1/7183 takes precedence
• CPC Class Codes: H04L 7/0337 Selecting between two or more discretely delayed clocks or selecting between two or more discretely delayed received code signals
• CPC Class Codes: H04L 7/048 using the properties of error detecting or error correcting codes, e.g. parity as synchronisation signal
• CPC Class Codes: H04W 56/0085 detecting a given structure in the signal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

An impulse radio-based ultra wideband communication system, using an ultra wideband impulse and a 1-bit high-speed digital sampler, includes a transmitting RF module, a receiving RF module, a signal recovery unit, a transmitting signal processor, a receiving signal processor, and an ultra wideband antenna. The transmitting RF module includes an integrated impulse generator capable of implementing on-off-keying modulation and pulse position modulation, and an amplifier for amplifying output of the integrated impulse generator. The receiving RF module includes a two stage envelope detector for detecting a received signal and a comparator for converting the detected signal into a rectangular pulse. The signal recovery unit restores the signal from the receiving RF module to a digital signal using the 1-bit digital sampler. The signal processor includes a receiving signal processor for synchronizing the digital signal and decoding the detected signal. The ultra wideband antenna transmits and receives an ultra wideband signal.

Claims

1. An impulse radio-based ultra wideband communication system using an ultra wideband impulse and a 1-bit digital sampler, comprising:

a transmitting RF module comprising an integrated impulse generator capable of implementing on-off-keying modulation or pulse position modulation, and an amplifier for amplifying output of the integrated impulse generator;

a receiving RF module comprising a two stage envelope detector for detecting an envelope of a received signal and a comparator for converting the detected signal into a rectangular pulse;

a digital signal recovery unit for restoring the signal from the receiving RF module to a digital signal using the 1-bit digital sampler;

a transmitting signal processor for impulse modulation or pulse mapping;

a receiving signal processor for synchronizing the digital signal and tracking symbol synchronization; and

an ultra wideband antenna for transmitting and receiving an ultra wideband impulse signal.

2. The impulse radio-based ultra wideband communication system as set forth in claim 1, wherein the 1-bit digital sampler comprises a clock generator having a time delay component and a pulse detector for detecting the rectangular pulse, wherein the clock generator generates a sequence of clock signals in parallel equally phased from each other from a system clock by gradually delaying the system clock and the pulse detector detects the rectangular pulse by applying the sequence of clock signals to the rectangular pulse.

3. The impulse radio-based ultra wideband communication system as set forth in claim 2, wherein the clock generator includes a time delay or phase conversion element, and generates a plurality of system clocks having a predetermined time difference/phase difference therebetween, wherein the plurality of system clocks are arranged in parallel.

4. The impulse radio-based ultra wideband communication system as set forth in claim 1, wherein the integrated impulse generator of the transmitting RF module comprises:

a D latch for receiving n bits of data to be transmitted through at least one input terminal;

an AND gate for performing an AND operation on an output signal of the D latch and a signal obtained by delaying the output signal of the D latch by a predetermined time; and

an inverter chain for performing current driving in order to prevent distortion of the output signal of the D latch.

5. The impulse radio-based ultra wideband communication system as set forth in claim 4, wherein the D latch outputs an impulse signal each time a data signal is present by fixing one input terminal to digital logic value ‘

HIGH’

when data to be transmitted is applied to another input terminal.

6. The impulse radio-based ultra wideband communication system as set forth in claim 1, wherein the receiving RF module comprises:

a wideband band-pass filter for preventing interference of adjacent frequencies among signals received from the ultra wideband antenna;

a low noise amplifier for low-noise-amplifying a filtered signal passed through the wideband band-pass filter;

an active attenuator for controlling amplitude of the amplified signal from the low noise amplifier; and

an automatic gain control amplifier for amplifying a signal passed through the active attenuator,

wherein the two-stage envelope detector for converting the RF signal, amplified by the automatic gain control amplifier, into the rectangular pulse.

7. The impulse radio-based ultra wideband communication system as set forth in claim 1, wherein the transmitting signal processor comprises:

transmission data memory for temporarily storing data to be transmitted;

a forward error correction encoder for performing forward error correction encoding;

a start/end bits generator for generating start/end signals indicating a start and end of a data packet to be transmitted;

a multiplexer for selecting data to be transmitted and control data;

transmission memory for storing data from the multiplexer; and

a pulse mapper for performing OOK or PPM modulation and transforming a waveform of receiving data into a waveform suitable for the input of the impulse generator.

8. The impulse radio-based ultra wideband communication system as set forth in claim 7, wherein the transmitting signal processor further comprises a controller for applying a control signal to respective elements so as to control a transfer flow of the entire signal.

9. The impulse radio-based ultra wideband communication system as set forth in claim 1, wherein the receiving signal processor comprises:

a symbol synchronizer for processing signal synchronization and synchronization tracking for the digital signal recovered by the signal recovery unit;

a start/end bits checker for checking a start and end of transmitted data;

receiving data memory for storing the transmitted data;

a forward error correction decoder for decoding the signal encoded in the transmitting signal processor; and

receiving memory for storing recovered original data.

10. The impulse radio-based ultra wideband communication system as set forth in claim 9, wherein the receiving signal processor further comprises a controller for applying a control signal to respective elements so as to control transfer flows of the entire signals.

11. The impulse radio-based ultra wideband communication system as set forth in claim 1, wherein the ultra wideband antenna is a square monopole antenna, which is printed in a stepped pattern on a section of a printed circuit board having a sloped ground surface, and has a coplanar waveguide feeding structure.

12. The impulse radio-based ultra wideband communication system as set forth in claim 11, wherein the ultra wideband antenna is formed by inserting a triangular or rectangular transition in a power feed portion so that it has wideband characteristics.

13. The impulse radio-based ultra wideband communication system as set forth in claim 9, wherein:

the digital sampler of the signal recovery unit is a 1-bit digital sampler; and

the symbol synchronizer performs;

a first step of removing noise present in a quantized input signal passed through the 1-bit digital sampler,

a second step of estimating a synchronization time point in the signal from which noise has been removed, and

a third step of determining the synchronization time point by verifying the estimated synchronization time point,

thereby achieving symbol synchronization of an input signal through the respective steps.

14. The impulse radio-based ultra wideband communication system as set forth in claim 13, wherein:

the symbol synchronizer comprises a correlator for increasing a signal to noise ratio of the quantized input signal of the 1-bit digital sampler;

the first step is to remove a signal lower than a predetermined amplitude from the quantized input signal using the correlator;

the second step is to extract sample groups from the signal from which noise has been removed;

to search for a sample having a greatest value in a first of the extracted sample groups; and

to estimate the searched sample to be the synchronization time point; and

the third step is to define a bit decision window in each symbol and to accept the estimated synchronization time point as the synchronization time point through a verification process for testing whether the symbol is included within a predetermined range while moving the bit decision window from the estimated synchronization time point to a time point of a preset number times a predetermined frame time.

15. The impulse radio-based ultra wideband communication system as set forth in claim 14, wherein the correlator is m(n) which satisfies the following equation (1), and the first step is to remove a signal lower than a predetermined amplitude from the quantized input signal {tilde over (r)}(n) using the correlator m(n) in order to increase a signal to noise ratio of the signal {tilde over (r)}(n) quantized by the 1-bit digital sampler,

16. The impulse radio-based ultra wideband communication system as set forth in claim 15, wherein the second step is to define a sample group, having an independent or continuous value higher than zero in the signal {tilde over (r)}_m(n) from which noise has been removed, as ‘

island’

;

to calculate a sample having a greatest value in each sample group ‘

island’ and

define the sample as ‘

flag’

; and

to estimate an index n_flag,1 of a sample ‘

flag’

having the greatest value in the ‘

island’

of the first of the sample groups to be the synchronization time point.

17. The impulse radio-based ultra wideband communication system as set forth in claim 16, wherein the third step is to define a bit decision window having a predetermined width N_BDW centered around a time point of (n_flag,1+i·

N_f), that is, a predetermined frame time i·

N_f after the estimated synchronization time point n_flag,1;

to check whether there is a symbol having a value higher than zero in each BDW while moving the center BDW_cen,i of the BDW to a time point of a preset number of N_i times a frame interval N_f according to the following Equation (2); and

to regard the estimated n_flag,1 to be an exact synchronization time point n_acq when there is a continuous symbol having a value higher than zero in the BDW,

BDW_i=[BDW_cen,i−

N_BDW/2,BDW_cen,i+N_BDW/2] 

 

(2)

where BDW_cen,i=n_flag,1+i·

N_f (i=1, 2, . . . , N_i).

18. The impulse radio-based ultra wideband communication system as set forth in claim 17, wherein a center BDW_cen,i of the BDW_i is moved to a time point of a preset number of N_i times a frame interval N_f, and, when only zero is present in any one BDW, the second step and the third step are repeatedly performed from a next sample to a time at which synchronization is achieved.

19. The impulse radio-based ultra wideband communication system as set forth in claim 18, wherein BDW_cen,1st for the first symbol after a time period for synchronization acquisition is determined based on a synchronization acquisition time n_acq and satisfies the following Equation (3), a center BDW_cen,k+1 of BDW_k+1 for the (k+1)^th symbol is determined based on a previous time point BDW_cen,k and an offset Δ

_k+1 and satisfies the following Equation (4), the offset Δ

_k+1 being a difference between a sample index n_flag,k having a greatest value in the Kth window BDW_k and the center index BDW_cen,k of the window BDW_k, and the acquired synchronization is tracked using the BDW_cen,1 and the BDW_cen,k+1,

BDW_cen,1st=n_acq+α

·

N_f 

 

(3)

where α

is the total number of symbols in a synchronization acquisition time period,

BDW_cen,k+1=(BDW_cen,k+N_f)+Δ

_k+1 

 

(4)

where Δ

_k+1=n_flag,k−

BDW_cen,k.

20. The impulse radio-based ultra wideband communication system as set forth in claim 19, wherein the offset Δ

_k+1 is regarded as zero if the sample index n_flag,k is not found because no symbol is present in the k^th sample group.

21. The impulse radio-based ultra wideband communication system as set forth in claim 20, wherein the symbol synchronization is achieved, and the BDW is set for each symbol through subsequent synchronization tracking, and a bit is identified in each BDW in such a way that, when a sample other than zero is present in the BDW for the signal {tilde over (r)}_m(n), it is determined that the signal {tilde over (r)}_m(n) is “

1(ON)”

, and, if only zero is present in the BDW, it is determined that the signal {tilde over (r)}_m(n) is “

0(OFF)”

.