System for coherent demodulation of binary phase shift keying signals (BPSK)

• US 20060193401A1
• Filed: 01/30/2006
• Published: 08/31/2006
• Est. Priority Date: 02/28/2005
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Cairo Molins, Josep Ignasi, Lopez Villegas, Jose Maria, Osorio Marti, Joan Aitor, Sieiro Cordoba, Jose Javier
• Granted Patent: US 7,564,929 B2
• Time in Patent Office: Days
• US Class Current: 375/326
• CPC Class Codes: H04L 27/2276 using frequency multiplication or harmonic tracking

Abstract

A system for the coherent demodulation of Binary Phase Shift Keying (BPSK) signal at a frequency f, comprising means for recovering a carrier signal (C) at a frequency 2f from said BPSK signal; means for injecting said signal having a frequency 2f in an injection locking oscillator (ILO), which has a natural resonant frequency f_r, being f_r substantially equal to f, which provides with differential output (O_p, O_n) signals which recover the original carrier with a phase shift of (θ_e−k)/2, where ${\theta }_e=\arcsin \left(\frac{f_r-f}{\alpha A_{i}f}\right)$
where α and k are parameters that depend on the type of predominant non-linearity in the injection locking oscillator (ILO), and A_i is the amplitude of the recovered carrier signal at a frequency of 2f, and means for combining the differential output (O_p, O_n) signals with a copy of the incoming BPSK signal in order to generate a demodulated signal (DEMOD).

Claims

1. A system for the coherent demodulation of Binary Phase Shift Keying (BPSK) signal at a frequency f, comprising:

means for recovering a carrier signal (C) at a frequency 2f from said BPSK signal,

means for injecting said signal having a frequency 2f in an injection locking oscillator (ILO), which has a natural resonant frequency f_r, being f_r substantially equal to f, which provides with differential output (O_p, O_n) signals which recover the original carrier with a phase shift of (θ

_e−

k)/2, where

${\mathrm{\theta <br><br>}}_e=\arcsin <br><br>\left(\frac{f_r-f}{\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>A_i<br><br>f}\right)$

where α and

k are parameters that depend on the type of predominant non-linearity in the injection locking oscillator (ILO), and A_i is the amplitude of the recovered carrier signal at a frequency of 2f, and

means for combining the differential output (O_p, O_n) signals with a copy of the incoming BPSK signal in order to generate a demodulated signal (DEMOD).

2. System for demodulation according to claim 1, wherein the means for combining the differential output (O_p, O_n) signals with the copy of the incoming BPSK signal comprises:

means for multiplying (Mix₁, Mix₂) the differential output signals (O_p, O_n) of the injection locking oscillator (ILO), with signals (i₁, i₃) which are copy of the incoming BPSK signal, and have the same frequency and very similar amplitudes and phases, which provide with output (IF₁, IF₂) signals respectively,

means for low-pass filtering (LPF₁, LPF₂) said outputs (IF₁, IF₂) signals to produce base-band signals (BB_p, BB_n), respectively,

means of subtracting the base-band signals to generate a demodulated signal (DEMOD).

3. System for demodulation according to claim 1, wherein the means for recovering a carrier signal (C) having a frequency 2f include a squaring circuit.

4. System for demodulation according to claim 3, which further comprises a band-pass filter block connected between the squaring circuit block and the injection locking oscillator (ILO).

5. System for demodulation according to claim 2, wherein the means for multiplying (Mix₁, Mix₂) are equal.

9. System for demodulation according to claim 3, wherein the means for multiplying (Mix₁, Mix₂) are equal.

10. System for demodulation according to claim 4, wherein the means for multiplying (Mix₁, Mix₂) are equal.

6. A method for the coherent demodulation of Binary Phase Shift Keying (BPSK) signals at a frequency f, based on the synchronisation of an oscillator by means of injection of a signal having a frequency of 2f.

7. Method according to claim 6, wherein

the oscillator is synchronized when injected with a signal having a frequency of 2f, and being the natural resonant frequency f_r of the oscillator substantially equal to f.

8. Method according to claim 7, comprising:

recovering a carrier signal (C) at a frequency 2f from said BPSK signal,

injecting said signal having a frequency 2f in an injection locking oscillator (ILO), in order to recover the original carrier with a phase shift of (θ

_e−

k)/2, where

${\mathrm{\theta <br><br>}}_e=\arcsin <br><br>\left(\frac{f_r-f}{\mathrm{\alpha <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>A_i<br><br>f}\right)$

where α and

k are parameters that depend on the type of predominant non-linearity in the injection locking oscillator (ILO), and A_i is the amplitude of the recovered carrier signal at a frequency of 2f, and

combining the differential output (O_p, O_n) signals with the copy of the incoming BPSK signal in order to generate a demodulated signal (DEMOD).