BPSK demodulation
Methods, systems, and apparatus for EM communications. One of the apparatus includes a super-regenerative amplifier (SRA) configured to receive a binary phase shift keying (BPSK) modulated signal and to output an amplitude signal as a function of changes in phase in the BPSK modulated signal; a pseudo synchronous demodulator that rectifies the amplitude signal and generates an envelope of the rectified amplitude signal; and an analog to digital converter that converts the amplitude values of the envelope to digital binary values.
1. An apparatus comprising:
a super-regenerative amplifier (SRA) configured to receive a binary phase shift keying (BPSK) modulated signal and to output an amplitude signal as a function of changes in phase of the BPSK modulated signal;
a synchronous demodulator configured to demodulate the amplitude signal, wherein demodulating the amplitude signal includes generating a bipolar envelope amplitude signal; and
an analog to digital converter that converts amplitude values of the bipolar envelope amplitude signal to digital binary values.
2. The apparatus of claim 1 , wherein the bipolar envelope amplitude signal has value Vmax when there is no phase change of the BPSK modulated signal relative to a local oscillator and —Vmax when there is a phase change of the BPSK modulated signal relative to the local oscillator.
3. The apparatus of claim 1 , further comprising:
a low pass filter coupled between the synchronous demodulator and the analog to digital converter.
4. The apparatus of claim 2 , wherein the local oscillator is provided by a Costas loop such that the local oscillator has substantially the same phase and frequency as the received BPSK modulated signal.
5. The apparatus of claim 1 , wherein amplification by the SRA approaches zero amplitude when a phase change occurs.
6. The apparatus of claim 1 , wherein a carrier extraction circuit is used to create a local oscillator signal that is substantially synchronous with the phase and frequency of the received BPSK modulated signal.
7. The apparatus of claim 6 , wherein the carrier extraction circuit includes a phase lock loop.
8. The apparatus of claim 1 , wherein the amplitude signal refers to a measure of one or more of voltage, current, power, frequency, phase, or temperature.
9. The apparatus of claim 1 , wherein the SRA includes a reset switch that resets amplification in response to a reset signal, wherein the reset signal period is in phase with incoming symbols that encode data in the BPSK modulated signal.
10. The apparatus of claim 9 , wherein providing the reset signal in phase with the incoming symbols includes using a synchronization mechanism to control a gain of an automatic gain control to accelerate or decelerate a speed of regeneration to keep the SRA synchronized with the incoming symbols.
11. The apparatus of claim 9 , wherein a timing of the reset signal is set to place a change of symbol in or near a middle of an SRA regeneration cycle.
12. A method comprising:
receiving a binary phase shift keyed (BPSK) modulated signal;
using a super-regenerative amplifier (SRA) to convert the phase of the BPSK modulated signal to amplitude values; and
performing synchronous demodulation to process the amplitude values into a bipolar envelope amplitude signal.
13. The method of claim 12 , further comprising:
converting the amplitude values of the bipolar envelope amplitude signal to digital binary values using a digital to analog converter.
14. The method of claim 12 , further comprising:
converting the amplitude values of the bipolar envelope amplitude signal to digital binary values using a comparator.
15. The method of claim 12 , wherein the bipolar envelope amplitude signal has value Vmax when there is no phase change relative to a local oscillator and —Vmax when there is a phase change relative to the local oscillator.
16. The method of claim 15 , wherein the local oscillator has substantially the same phase and frequency as the received BPSK modulated signal.
17. The method of claim 15 , comprising: generating the local oscillator using a carrier extraction circuit including a phase lock loop.
18. The method of claim 12 , wherein the SRA includes a reset switch that resets amplification in response to a reset signal, wherein the reset signal period is in phase with incoming symbols.
19. The method of claim 18 , wherein providing the reset signal in phase with the incoming symbols includes using a synchronization mechanism to control a gain of an automatic gain control to accelerate or decelerate a speed of regeneration to keep the SRA synchronized with the incoming symbols.
20. The method of claim 18 , wherein a timing of the reset signal is set to place a change of symbol in or near a middle of an SRA regeneration cycle.