Bandwidth adaptation in a transmission circuit
Bandwidth adaptation in a transmission circuit is provided. The transmission circuit includes a power amplifier circuit that amplifies a radio frequency (RF) signal based on a modulated voltage, an envelope tracking integrated circuit (ETIC) that generates the modulated voltage based on a modulated target voltage, and a transceiver circuit that generates the RF signal and the modulated target voltage. The RF signal may have a wide modulation bandwidth but the ETIC may have a lower bandwidth limit, which can cause distortion in the modulated voltage and the RF signal. In this regard, the transceiver circuit is configured to generate the modulated target voltage in a lower bandwidth than the bandwidth limit when the modulation bandwidth of the RF signal exceeds the bandwidth limit of the ETIC. As such, the transmission circuit can process the RF signal across the wide modulation bandwidth without causing distortion in the RF signal.
1 . A transmission circuit comprising:
a power amplifier circuit configured to amplify a radio frequency (RF) signal based on a modulated voltage;
an envelope tracking integrated circuit (ETIC) configured according to a defined bandwidth limit to generate the modulated voltage based on a modulated target voltage; and
a transceiver circuit comprising:
a signal processing circuit configured to modulate the RF signal to a signal modulation bandwidth based on a time-variant modulation vector; and
a voltage processing circuit configured to cause the modulated target voltage to be generated in a target voltage bandwidth that is lower than or equal to the defined bandwidth limit of the ETIC when the signal modulation bandwidth is higher than the defined bandwidth limit of the ETIC.
2 . The transmission circuit of claim 1 , wherein the voltage processing circuit is further configured to cause the modulated target voltage to be generated in the target voltage bandwidth that equals the signal modulation bandwidth when the signal modulation bandwidth is lower than or equal to the defined bandwidth limit of the ETIC.
3 . The transmission circuit of claim 1 , wherein the voltage processing circuit comprises:
a frequency equalizer circuit configured to apply a complex filter to the time-variant modulation vector to generate a frequency-equalized modulation vector that can compensate for a voltage distortion filter presented to the power amplifier circuit by coupling the power amplifier circuit to an RF front-end circuit; and
an amplitude detector configured to detect a time-variant amplitude of the frequency-equalized modulation vector.
4 . The transmission circuit of claim 3 , wherein the voltage processing circuit further comprises:
a windowed peak detector circuit configured to:
generate one or more amplitude samples of the frequency-equalized modulation vector in each of a plurality of sampling windows;
detect a peak amplitude among the one or more amplitude samples in each of the plurality of sampling windows; and
generate a sampled modulation vector in the target voltage bandwidth and comprising the peak amplitude detected in each of the plurality of sampling windows; and
an envelope tracking (ET) lookup table (LUT) circuit configured to generate a modulated digital target voltage based on the sampled modulation vector.
5 . The transmission circuit of claim 4 , wherein the windowed peak detector circuit is further configured to:
generate one amplitude sample of the frequency-equalized modulation vector when the signal modulation bandwidth of the RF signal is lower than or equal to the defined bandwidth limit of the ETIC; and
generate multiple amplitude samples of the frequency-equalized modulation vector when the signal modulation bandwidth of the RF signal is higher than the defined bandwidth limit of the ETIC.
6 . The transmission circuit of claim 4 , wherein the signal processing circuit comprises:
a windowing buffer configured to buffer an equal number of amplitude samples of the time-variant modulation vector as a number of the one or more amplitude samples of the frequency-equalized modulation vector that are generated in each of the plurality of sampling windows to thereby generate a windowed modulation vector; and
a modulator circuit configured to generate the RF signal from the windowed modulation vector.
7 . The transmission circuit of claim 4 , wherein the transceiver circuit further comprises:
a current processing circuit configured to generate a compensation term based on the modulated voltage and a total inductive impedance presented at the power amplifier circuit;
a combiner configured to combine the compensation term and the modulated digital target voltage to generate a modified digital target voltage; and
a digital-to-analog converter (DAC) configured to convert the modified digital target voltage into the modulated target voltage.
8 . The transmission circuit of claim 7 , wherein the current processing circuit comprises:
an equalizer circuit configured to apply a complex current filter to the time-variant modulation vector to generate an equalized modulation vector, wherein the complex current filter is different from the complex filter;
an amplitude detector circuit configured to detect a time-variant amplitude of the equalized modulation vector;
a load LUT circuit configured to generate a time-variant digital current term based on the detected time-variant amplitude of the equalized modulation vector; and
a filter circuit configured to convert the time-variant digital current term into the compensation term.
9 . The transmission circuit of claim 3 , wherein the voltage processing circuit further comprises:
an envelope tracking (ET) lookup table (LUT) circuit configured to generate a modulated digital target voltage based on the frequency-equalized modulation vector; and
a windowed peak detector circuit configured to:
generate one or more amplitude samples of the modulated digital target voltage in each of a plurality of sampling windows;
detect a peak amplitude among the one or more amplitude samples in each of the plurality of sampling windows; and
regenerate the modulated digital target voltage in the target voltage bandwidth based on the peak amplitude detected in each of the plurality of sampling windows.
10 . The transmission circuit of claim 9 , wherein the windowed peak detector circuit is further configured to:
generate one amplitude sample of the modulated digital target voltage when the signal modulation bandwidth of the RF signal is lower than or equal to the defined bandwidth limit of the ETIC; and
generate multiple amplitude samples of the modulated digital target voltage when the signal modulation bandwidth of the RF signal is higher than the defined bandwidth limit of the ETIC.
11 . The transmission circuit of claim 9 , wherein the transceiver circuit further comprises:
a current processing circuit configured to generate a compensation term based on the modulated voltage and a total inductive impedance presented at the power amplifier circuit;
a combiner configured to combine the compensation term and the modulated digital target voltage to generate a modified digital target voltage; and
a digital-to-analog converter (DAC) configured to convert the modified digital target voltage into the modulated target voltage.
12 . The transmission circuit of claim 11 , wherein the current processing circuit comprises:
an equalizer circuit configured to apply a complex current filter to the time-variant modulation vector to generate an equalized modulation vector, wherein the complex current filter is different from the complex filter;
an amplitude detector circuit configured to detect a time-variant amplitude of the equalized modulation vector;
a load LUT circuit configured to generate a time-variant digital current term based on the detected time-variant amplitude of the equalized modulation vector; and
a filter circuit configured to convert the time-variant digital current term into the compensation term.
13 . A transceiver circuit comprising:
a signal processing circuit configured to modulate a radio frequency (RF) signal to a signal modulation bandwidth based on a time-variant modulation vector, wherein the RF signal is amplified by a power amplifier circuit based on a modulated voltage generated by an envelope tracking integrated circuit (ETIC) based on a modulated target voltage; and
a voltage processing circuit configured to cause the modulated target voltage to be generated in a target voltage bandwidth that is lower than or equal to a defined bandwidth limit of the ETIC when the signal modulation bandwidth is higher than the defined bandwidth limit of the ETIC.
14 . The transceiver circuit of claim 13 , wherein the voltage processing circuit is further configured to cause the modulated target voltage to be generated in the target voltage bandwidth that equals the signal modulation bandwidth when the signal modulation bandwidth is lower than or equal to the defined bandwidth limit of the ETIC.
15 . The transceiver circuit of claim 13 , wherein the voltage processing circuit comprises:
a frequency equalizer circuit configured to apply a complex filter to the time-variant modulation vector to generate a frequency-equalized modulation vector; and
an amplitude detector configured to detect a time-variant amplitude of the frequency-equalized modulation vector.
16 . The transceiver circuit of claim 15 , wherein the voltage processing circuit further comprises:
a windowed peak detector circuit configured to:
generate one or more amplitude samples of the frequency-equalized modulation vector in each of a plurality of sampling windows;
detect a peak amplitude among the one or more amplitude samples in each of the plurality of sampling windows; and
generate a sampled modulation vector in the target voltage bandwidth and comprising the peak amplitude detected in each of the plurality of sampling windows; and
an envelope tracking (ET) lookup table (LUT) circuit configured to generate a modulated digital target voltage based on the sampled modulation vector.
17 . The transceiver circuit of claim 16 , wherein the windowed peak detector circuit is further configured to:
generate one amplitude sample of the frequency-equalized modulation vector when the signal modulation bandwidth of the RF signal is lower than or equal to the defined bandwidth limit of the ETIC; and
generate multiple amplitude samples of the frequency-equalized modulation vector when the signal modulation bandwidth of the RF signal is higher than the defined bandwidth limit of the ETIC.
18 . The transceiver circuit of claim 16 , wherein the transceiver circuit further comprises:
a current processing circuit configured to generate a compensation term based on the modulated voltage and a total inductive impedance presented at the power amplifier circuit;
a combiner configured to combine the compensation term and the modulated digital target voltage to generate a modified digital target voltage; and
a digital-to-analog converter (DAC) configured to convert the modified digital target voltage into the modulated target voltage.
19 . The transceiver circuit of claim 18 , wherein the current processing circuit comprises:
an equalizer circuit configured to apply a complex current filter to the time-variant modulation vector to generate an equalized modulation vector, wherein the complex current filter is different from the complex filter;
an amplitude detector circuit configured to detect a time-variant amplitude of the equalized modulation vector;
a load LUT circuit configured to generate a time-variant digital current term based on the detected time-variant amplitude of the equalized modulation vector; and
a filter circuit configured to convert the time-variant digital current term into the compensation term.
20 . The transceiver circuit of claim 15 , wherein the voltage processing circuit further comprises:
an envelope tracking (ET) lookup table (LUT) circuit configured to generate a modulated digital target voltage based on the frequency-equalized modulation vector; and
a windowed peak detector circuit configured to:
generate one or more amplitude samples of the modulated digital target voltage in each of a plurality of sampling windows;
detect a peak amplitude among the one or more amplitude samples in each of the plurality of sampling windows; and
regenerate the modulated digital target voltage in the target voltage bandwidth based on the peak amplitude detected in each of the plurality of sampling windows.