Geometric harmonic modulation (GHM)-digital implementation

• US 5,519,692 A
• Filed: 03/20/1995
• Issued: 05/21/1996
• Est. Priority Date: 03/20/1995
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hassan, Amer A., Saulnier, Gary J., Hershey, John E.
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): NGO, RICKY QUOC
• Application Number:
  US08/407,554
• Time in Patent Office: 428 Days
• Field of Search: 370/11, 370/12, 370/18, 370/19, 370/20, 370/21, 370/23, 370/50, 370/69.1, 370/121, 370/93, 370/94.1, 370/95.1, 370/95.3, 375/200, 375/205, 375/206, 375/295, 375/316, 375/208, 375/358, 455/38.1, 455/91, 455/130, 340/825.03, 340/825.04, 340/825.15, 340/825.52
• US Class Current: 370/210
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems

Abstract

A set of phases defining an `address` and a `spreading key` is selected. These are employed in determining a preamble waveform and a traffic waveform. The preamble carrier waveform is a sum of a set of tones each offset by its phase, whereas the traffic carrier waveform is the product of these same offset tones. The tones have frequencies which are geometrically increasing multiples of a fundamental frequency. The phases and magnitudes of the preamble and traffic carrier waveforms are determined and prestored in a transmit and receive unit storage device. An inverse discrete Fourier Transform unit (IDFT) in the transmit unit receives the phase preamble offsets and magnitudes from the storage unit and creates a preamble carrier signal transmitted to the receive unit which determines if the phases match those which it is to listen to. If not, the following message is ignored; if they are, the following message is despread and decoded. IDFT creates a traffic carrier waveform from the traffic phases and magnitudes. Binary information is encoded in the carrier, processed and transmitted to the receive unit. A discrete Fourier Transform unit converts the received signal into phases and magnitudes. A dot product unit determines a dot product of the phase and magnitudes of the received signal and the traffic carrier waveform over a number of frequencies. A decision unit determines a binary message from the dot product.

Claims

1. A geometric harmonic modulation (GHM) transmit unit for transmitting a binary message to an intended receiver denoted by an address being a set of n+1 phase offsets comprising:

a) a storage device for storing digital information;

b) a calculation unit coupled to the storage device for producing preamble phases and magnitudes (φ

_i^p,M_i^p) defining a preamble carrier waveform, and traffic phases and magnitudes (φ

_j^t,M_j^t) defining a traffic carrier waveform from said set of phase offsets, and for storing the preamble and traffic phases and magnitudes in the storage device;

c) a digital modulation unit coupled to the storage device, for operating in a preamble mode producing a preamble carrier signal from the preamble phases and magnitudes, and for operating in a traffic mode producing a traffic carrier signal from the traffic phases and magnitudes; and

d) a binary encoder coupled to the digital modulation unit for encoding said binary message desired to be transmitted in the traffic carrier waveform when the digital modulation unit is operating in the traffic mode to produce an encoded signal for transmission.

2. A GHM transmit unit of claim 1 wherein the calculation unit comprises:

a) a preamble waveform source for producing samples of a preamble carrier waveform defined by;

##EQU10## where n is an order of the function being one less than the number of phase offsets in said address,

Φ

=(φ

₀,φ

₁, . . . , φ

_n) are said set of phase offsets of said address,

t is time,

and R is an inverse of a rate at which said binary message is to be transmitted;

b) a traffic waveform source for producing samples of a traffic carrier waveform defined by;

##EQU11## c) a transform unit for producing phases and magnitudes (φ

_i^p,M_i^p), (φ

_j^t,M_j^t) from the preamble and traffic carrier waveform samples, respectively, and storing these in the transmit unit storage device.

3. A geometric harmonic modulation (GHM) receive unit for decoding a binary message encoded, along with an address being a set of n+1 phase offsets, in a received signal comprising:

a) storage device for storing digital information;

b) calculation unit coupled to the storage device for producing preamble phases and magnitudes (φ

_i^p,M_i^p) defining a preamble carrier waveform, and traffic phase offsets and magnitudes (φ

_j^t,M_j^t) defining a traffic carrier waveform from a set of n+1 phase offsets of an address desired to be monitored, and for storing the preamble and traffic phases and magnitudes in the storage device;

c) digital demodulation unit coupled to the storage device, for determining a set of received phase offsets and magnitudes from said received signal;

d) a dot product unit coupled to the storage device for determining a dot product between traffic phase offsets and magnitudes and phase offsets and magnitudes provided to it;

e) a logic unit coupled to the digital demodulation unit, the storage device, and the logic dot product unit, for comparing the received phase offsets and magnitudes to the preamble phase offsets and magnitudes for synchronization with the received signal, the logic unit passing the received phase offsets and magnitudes of subsequent signals to the dot product unit when the received phase offsets match the phase offsets of the address desired to be monitored; and

f) a decision device coupled to the dot product unit for receiving the messages passed by the logic unit and for providing a binary message by producing a first logical value when the dot product is above a threshold, and a second logical value otherwise.

4. A GHM receive unit of claim 3 wherein the calculation unit comprises:

a) a preamble waveform source for producing samples of a preamble carrier waveform described by;

##EQU12## where n is an order of the function being one less than the number of phase offsets in said address,

Φ

=(φ

₀ φ

₁, . . . , φ

_n) are said set of phase offsets of said address,

t is time,

and R is an inverse of a rate at which said binary message is to be transmitted.

b) a traffic waveform source for producing samples of a traffic carrier waveform defined by;

##EQU13## c) a transform unit for producing phases and magnitudes from the preamble and traffic carrier waveform samples, respectively, and storing these in the receive unit storage device.