Periodic bandwidth widening for inductive coupled communications
In described examples, a method of inductive coupled communications includes providing a first resonant tank (first tank) and a second resonant tank (second tank) tuned to essentially the same resonant frequency, each having antenna coils and switches positioned for changing a Q and a bandwidth of their tank. The antenna coils are separated by a distance that provides near-field communications. The first tank is driven to for generating induced oscillations to transmit a predetermined number of carrier frequency cycles providing data. After the predetermined number of cycles, a switch is activated for widening the bandwidth of the first tank. Responsive to the oscillations in the first tank, the second tank begins induced oscillations. Upon detecting a bit associated with the induced oscillations, a switch is activated for widening the bandwidth of the second tank and a receiver circuit receiving an output of the second tank is reset.
1. A method of resonant inductive coupled communication, responsive to oscillations generated by a modulated carrier signal from a first resonant tank (first tank) that is tuned to a first resonant frequency and that includes first antenna coils, a first capacitor coupled in parallel to the first antenna coils, a first resistor coupled in series between the first antenna coils, and a first switch coupled in series between the first antenna coils, the first antenna coils transmitting a predetermined number of carrier frequency cycles for providing data that is first transition coded, and the first switch being activated for widening a bandwidth and changing a Q factor of the first tank after the predetermined number of carrier frequency cycles, the method comprising:
responsive to the oscillations in the first tank, beginning induced oscillations in a second resonant tank (second tank) tuned to a second resonant frequency essentially equal the first resonant frequency and that includes: a second antenna coil that is separated from the first antenna coils by a distance that provides near-field communications; a second capacitor coupled in parallel to the second antenna coil; and a second switch coupled in parallel to the second antenna coil; and
with a receiver sense circuit, responsive to detecting a bit associated with the induced oscillations of the second tank, activating the second switch for widening a bandwidth and changing a Q factor of the second tank, and resetting the receiver sense circuit.
2. The method of claim 1 , further comprising: opening the second switch to remove a second resistor from the second tank.
3. The method of claim 1 , wherein the modulated carrier signal is an amplitude-shift keyed (ASK) signal.
4. The method of claim 1 , wherein the receiver sense circuit includes an amplifier:
coupled to receive an output of the second tank at inputs of the amplifier; and coupled in series to a rectifier and peak detector and a delay block.
5. The method of claim 1 , wherein a product of a maximum Q factor for the first tank and a maximum Q factor for the second tank is ≧50.
6. The method of claim 1 , wherein the modulated carrier signal is at a carrier frequency from 500 MHz to 4 GHz.
7. The method of claim 1 , wherein a first die includes the first tank, a second die includes the second tank, and the first antenna coils and the second antenna coil include metal loops.
8. The method of claim 7 , wherein the first die and the second die are positioned lateral to one another on a split leadframe within a multichip package (MCP), and the first die and the second die have mold compound thereover and therebetween.
9. The method of claim 7 , wherein the first die and the second die are in a stacked configuration on a substrate within a multichip package (MCP).
10. The method of claim 1 , wherein the oscillations from the first tank are generated from applying a periodic wave tuned to the first resonant frequency modulated by the data.
11. A resonant inductive coupled communications system, responsive to oscillations generated by a modulated carrier signal from a first resonant tank (first tank) that is tuned to a first resonant frequency and that includes first antenna coils, a first capacitor coupled in parallel to the first antenna coils, a first resistor coupled in series between the first antenna coils, and a first switch coupled in series between the first antenna coils, the first antenna coils transmitting a predetermined number of carrier frequency cycles for providing data that is first transition coded, and the first switch being activated for widening a bandwidth and changing a Q factor of the first tank after the predetermined number of carrier frequency cycles, the system comprising:
a second resonant tank (second tank) to begin induced oscillations responsive to the oscillations in the first tank, the second tank being tuned to a second resonant frequency essentially equal the first resonant frequency and including: a second antenna coil that is separated from the first antenna coils by a distance that provides near-field communications; a second capacitor coupled in parallel to the second antenna coil; and a second switch coupled in parallel to the second antenna coil;
receiver sense circuitry coupled to: responsive to detecting a bit associated with the induced oscillations of the second tank, activate the second switch for widening a bandwidth and changing a Q factor of the second tank, and reset the receiver sense circuitry.
12. The system of claim 11 , the second tank is operable to open the second switch for removing a second resistor from the second tank.
13. The system of claim 11 , wherein the modulated carrier signal is an amplitude-shift keyed (ASK) signal.
14. The system of claim 11 , wherein the receiver sense circuitry includes an amplifier: coupled to receive an output of the second tank at inputs of the amplifier; and coupled in series to a rectifier and peak detector and a delay block.
15. The system of claim 11 , wherein a product of a maximum Q factor for the first tank and a maximum Q factor for the second tank is ≧50.
16. The system of claim 11 , wherein the modulated carrier signal is at a carrier frequency from 500 MHz to 4 GHz.
17. The system of claim 11 , wherein a first die includes the first tank, a second die includes the second tank, and the first antenna coils and the second antenna coil include metal loops.
18. The system of claim 17 , wherein the first die and the second die are positioned lateral to one another on a split leadframe within a multichip package (MCP), and the first die and the second die have mold compound thereover and therebetween.
19. The system of claim 17 , wherein the first die and the second die are in a stacked configuration on a substrate within a multichip package (MCP).
20. The system of claim 11 , wherein the oscillations from the first tank are generated from applying a periodic wave tuned to the first resonant frequency modulated by the data.