Variable bandwidth envelope modulator for use with envelope elimination and restoration transmitter architecture and method
A RF transmitter has at least one amplifier having an input terminal for receiving a phase modulated signal to be transmitted on an RF carrier and an input node for receiving a modulation signal for amplitude modulating the RF carrier. The RF transmitter further includes an amplitude modulator having an output coupled to the input node of the power amplifier through a low-pass filter. The low-pass filter includes at least one variable filter component for varying a bandwidth of the low-pass filter. In a preferred embodiment an envelope elimination and restoration (EER) RF transmitter includes at least one power RF amplifier having the input terminal for receiving the phase modulated signal to be transmitted on the RF carrier, and further including an input power node for receiving a modulated voltage for amplitude modulating the RF carrier. The EER RF transmitter further includes a class-S modulator having a variable bandwidth low-pass filter having an output coupled to the input power node and including at least one first variable capacitance.
1. A apparatus, comprising:
at least one amplifier comprising an input terminal for receiving a phase modulated signal to be transmitted on an RF carrier, said at least one amplifier further comprising an input node for receiving a modulation signal for amplitude modulating the RF carrier; and
an amplitude modulator having an output configurable to be connected with the input node of said at least one amplifier, the output of said amplitude modulator being filtered using a low-pass filter comprised of at least one variable filter component for varying a bandwidth of the low-pass filter;
where the input node of said at least one amplifier comprises a power input node, and where said amplitude modulator is comprised of a variable frequency pulse width modulator comprising a part of a dc to dc converter for supplying operating power to said power input node.
2. An apparatus as in claim 1 , further comprising at least one variable bypass capacitance configurable to be connected with said input node.
3. An apparatus as in claim 1 , where said at least one variable filter component is comprised of a capacitance that is configurable to be switchably connected with said output of said amplitude modulator.
4. An apparatus as in claim 1 , further comprising at least one bypass capacitance that is configurable to be switchably connected with said input node.
5. A RF transmitter as in claim 1 , embodied at least partially in an integrated circuit.
6. An apparatus as in claim 1 , having a polar architecture.
7. An apparatus as in claim 1 , embodied as an envelope elimination and restoration transmitter.
8. An apparatus, comprising:
a plurality of amplifiers each comprising an input terminal for receiving a phase modulated signal to be transmitted on an RF carrier, each of said plurality of amplifiers further comprising an input node for receiving a modulation signal for amplitude modulating the RF carrier; and
an amplitude modulator having an output configurable to be connected with the input node of each of said plurality of amplifiers, the output of said amplitude modulator being filtered using a low-pass filter comprised of at least one variable filter component for varying a bandwidth of the low-pass filter;
further comprising a plurality of variable bypass capacitances individual ones of which are configurable to be connected with said input node of an individual one of said plurality of amplifiers.
9. An apparatus as in claim 8 , embodied at least partially in an integrated circuit.
10. An apparatus as in claim 8 , having a polar architecture.
11. An apparatus as in claim 8 , embodied as an envelope elimination and restoration transmitter.
12. An apparatus, comprising:
at least one power RE amplifier comprising an input terminal for receiving a phase modulated signal to be transmitted on an RE carrier and further comprising an input power node for receiving a modulated voltage for amplitude modulating the RE carrier; and
a class-S modulator comprising a variable bandwidth low-pass filter having an output configurable to supply a filtered signal to said input power node and comprising at least one first variable capacitance;
where said class-S modulator is comprised of a variable frequency pulse width modulator comprising a part of a dc to dc converter for supplying operating power to said input power node.
13. The apparatus as in claim 12 , further comprising at least one second variable capacitance configurable to be connected with said input power node for bypassing said input power node to ground.
14. The apparatus as in claim 13 , where values of said first and second variable capacitances are set as a function of required bandwidth.
15. The apparatus as in claim 12 , embodied in a mobile communication terminal.
16. An apparatus as in claim 12 , embodied at least partially in an integrated circuit.
17. An apparatus as in claim 12 , embodied as a transmitter having a polar architecture.
18. An apparatus as in claim 12 , embodied as an envelope elimination and restoration transmitter.
19. A method comprising:
in a first mode of operation, setting a value of at least one component of a low-pass filter of an amplitude modulator, said amplitude modulator having an output configurable to be connected with an input node of a power amplifier, where setting the value causes the low-pass filter to have a first bandwidth; and
in a second mode of operation, setting the value of the at least one component of the low-pass filter of the amplitude modulator for setting the low-pass filter to have a second bandwidth that differs from the first bandwidth;
where in both the first mode of operation and the second mode of operation further comprising operating the amplitude modulator as a variable frequency pulse width modulator that comprises part of a dc to dc converter configurable to output operating power to the power amplifier.
20. A method as in claim 19 , where the steps of setting are performed by a control unit of a communication terminal operating under control of a stored program.
21. A method as in claim 19 , where setting the value sets the value of at least one capacitance.
22. A method as in claim 19 , where setting the value sets the value of at least one inductance.
23. A method as in claim 19 , where setting the value sets the state of at least one switch that comprises part of a switched capacitance network.
24. An apparatus, comprising:
means for amplifying a phase modulated signal to be transmitted;
means for amplitude modulating a voltage, comprising variable frequency pulse width modulator means comprising a part of dc to dc converter means configurable to output amplifying means operating power; and
means for filtering said amplitude modulated voltage prior to said amplitude modulated voltage being applied to a power input node of said amplifying means, comprising means for varying a bandwidth of said filtering means at least as a function of an operating mode of a communication terminal that comprises said apparatus.
25. An apparatus as in claim 24 , where said varying means comprises means for setting a value of at least one of a capacitance and an inductance that comprises part of said means for filtering.
26. An apparatus as in claim 24 , embodied at least partially in an integrated circuit.
27. An apparatus as in claim 24 , embodied as a transmitter having a polar architecture.
28. An apparatus as in claim 24 , embodied as an envelope elimination and restoration transmitter.
29. An apparatus as in claim 24 , where the operating mode is selected from at least two operating modes each using a different type of modulation.