Inductive communication system with increased noise immunity using low-complexity transmitter

• US 8,155,168 B2
• Filed: 06/20/2006
• Issued: 04/10/2012
• Est. Priority Date: 06/23/2005
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Thijs, Jeroen, Such, Olaf, Pinter, Robert, Muehlsteff, Jens
• Primary Examiner(s): LEE, SIU M
• Application Number:
  US11/917,514
• Publication Number:
  US 20080205489A1
• Time in Patent Office: 2,121 Days
• Field of Search: 375/142, 375/146, 375/242, 375/150, 375/241, 375/254
• US Class Current: 375/142
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 14/04 using pulse code modulation

Abstract

A modulator for a communications system includes a spread spectrum coder and a pulse code modulator having a signal input port connectable to a signal output port of the spread spectrum coder. The modulator performs a robust and error free modulation and coding scheme by using a modified spread spectrum scheme combined with pulse code modulation. The communication system contains a low data rate, noise robust modulation and coding scheme using a very simple transmitter. This results in a very straightforward transmitter circuit, reducing size and costs of the transmitter.

Claims

1. A transmitter comprising:

a pseudo noise generator which provides a pseudo noise signal;

a spread spectrum coder which receives an input signal and the pseudo noise signal and combines the input signal and the pseudo noise signal to generate a spread spectrum signal at a signal output port;

a pulse code modulator having a signal input port connected to the signal output port of the spread spectrum coder to pulse code modulate the spread spectrum coded signal, yielded by the spread spectrum coder, into a pulse-code modulated signal on a pulse code modulator output; and

an output stage connected to an output of the pulse code modulator output to output the pulse code modulated signal to a transducer for transmission.

2. The transmitter according to claim 1, wherein the pulse code modulator modulates an instantaneous value of the spread spectrum coded signal into a sequence that is part of the pulse-code modulated signal.

3. The transmitter according to claim 1, further comprising:

a resonant circuit and a switch which alternatingly energizes and de-energizes the resonant circuit in response to a signal generated by the modulator.

4. The transmitter according to claim 3, wherein the resonant circuit has a resonance frequency in a long wave range.

5. The transmitter according to claim 1, wherein the transducer includes:

a magnetic transducer such that the transmitted pulse code modulated signal has a magnetic field component.

6. A demodulator for a communications system, the demodulator corresponding to a transmitter within said communications system and comprising:

a correlator which performs a correlation of a received signal and a reference signal, the reference signal being representative of a system response of the transmitter when excited by a particular pulse-code modulated sequence, the particular pulse-code modulated sequence being representative of a selected pulse-code modulated value;

a peak detector, an input port of the peak detector being connected to an output port of the correlator; and

a spread spectrum decoder, an input port of the spread spectrum decoder being connected to an output port of the peak detector.

7. A data transmission system for healthcare applications comprising:

an on-body transmitter for mounting adjacent a body which absorbs E-field signals and propagates B-field signals, the transmitter including;

a sent-site spread spectrum encoder which receives a data signal and encodes the data signal into a spread spectrum signal,

a sent-site pulse-code modulator which receives the spread spectrum signal and encodes it into a pulse code modulated signal,

an output stage which receives the pulse code modulated signal and applies the pulse code modulated signal to a transmit transducer to transmit a B-field signal; and

a demodulator including;

an input circuit connected with a receive transducer to receive the transmitted B-field signal,

a pulse code demodulator which demodulates the B-field signal to generate a pulse code demodulated signal, and

a spread spectrum decoder which decodes the pulse code demodulated signal to recover the data signal.

8. The data transmission system according to claim 7, wherein the on-body transmitter output circuit includes:

a resonant circuit; and

a switch which alternatingly energizes and de-energizes the resonant circuit in response to the pulse code modulated signal encoded by the pulse-code modulator.

9. The data transmission system according to claim 7, wherein the pulse-code demodulator includes:

a correlator that generates a correlated signal from the received signal; and

a peak detector connected to the correlator to receive the correlated signal and with the spread spectrum decoder to supply the pulse code demodulated signal thereto.

10. A method for transmitting data from a transmitter to a receiver comprising:

performing a spread spectrum encoding on a signal representative of said data yielding a spread spectrum coded signal;

performing a pulse code modulation on the spread spectrum coded signal yielding a pulse-code modulated signal;

transmitting the pulse-code modulated signal;

receiving the transmitted pulse-code modulated signal;

performing a correlation of the pulse-code modulated signal and a reference signal to obtain a cross-correlation, the reference signal being representative of a system response of the transmitter when excited by a pulse-code modulated sequence, the pulse-code modulated sequence being representative of a selected value out of possible values of the spread spectrum coded signal;

performing a peak detection on the cross-correlation.

11. The method according to claim 10, further comprising:

prior to transmitting the pulse-code modulated signal, alternatingly energizing and de-energizing a resonant circuit in response to the pulse-code modulated signal.

12. The method according to claim 11, further including:

locating the transmitter close to a body that absorbs E-fields.

13. A communications system for operating near a body that absorbs electrical field signals, the communications system comprising:

a transmitter; and

a demodulator including;

an input circuit connected with a receive transducer to receive a transmitted pulse-coded signal,

a pulse code demodulator which demodulates the transmitted pulse-coded signal to generate a pulse code demodulated signal, and

a spread spectrum decoder which decodes the pulse code demodulated signal to recover a data signal.

14. The communications system for operating near a body that absorbs electrical field signals according to claim 13, wherein the transmitter includes:

a spread spectrum coder which generates a spread spectrum coded signal from a data signal carrying data to be transmitted;

a pulse code modulator having an input connected to an output of the spread spectrum coder to pulse code modulate the spread spectrum coded signal;

a transmit transducer;

an output stage which receives the pulse-coded signal from the pulse code modulator and applies the pulse-coded signal to the transmit transducer.