Signal amplification and transmission based on complex delta sigma modulator

Patent metadata

Field	Value
Publication number	US-10158382-B2
Application number	US-201415318067-A
Country	US
Kind code	B2
Filing date	Jun 23, 2014
Priority date	Jun 23, 2014
Publication date	Dec 18, 2018
Grant date	Dec 18, 2018

Abstract

Apparatuses and methods for power amplification and signal transmission using complex delta-sigma modulation are disclosed. In one embodiment, a complex delta sigma modulator unit comprising a complex polar quantizer within an integrator loop is disclosed. The complex polar quantizer quantizes the envelope of a complex integrated signal and produces a complex quantized output signal of substantially constant envelope. The complex quantized output signal is used in deriving a complex feedback signal within the integrator loop of the complex DSM. The complex quantized output signal may be used in driving a power amplifier substantially at saturation. In some embodiments, an adjacent channel power ratio (ACPR) enhancement technique is used to reduce the quantization noise in the complex quantized output signal.

First claim

What is claimed is:

1. A complex delta-sigma modulator (DSM) for processing a complex digital input signal, the complex DSM comprising:
a subtractor configured to subtract a complex feedback signal from the complex digital input signal and produce a delta signal;
an integrator configured to integrate the delta signal into an integrated signal; and
a complex polar quantizer that comprises a processor configured to quantize an envelope of the integrated signal and output a complex quantized output signal of substantially constant envelope, wherein the processor is further configured to:
determine the envelope of the integrated signal, based on an in-phase component and a quadrature component of the integrated signal;
calculate a scaling factor, based on the determined envelope of the integrated signal and a selected quantization level; and
produce the complex quantized output signal, by multiplication of the in-phase component and the quadrature component of the integrated signal with the scaling factor, wherein the complex feedback signal is obtained from the complex quantized output signal.

2. A complex delta-sigma modulator (DSM) based transmitter for transmitting a radio-frequency (RF) signal over an RF band, the complex DSM based transmitter comprising:
a digital processing block, wherein the digital processing block comprises:
a signal interpolator configured to oversample a complex digital input signal into a complex oversampled digital signal; and
a complex DSM configured to process the complex oversampled digital signal into a quantized complex oversampled output signal of substantially constant envelope, using a complex polar quantizer provided within an integrator loop, wherein the complex polar quantizer comprises a processor configured to quantize the envelope of an integrated signal, and a complex feedback signal for the integrator loop is obtained from the quantized complex oversampled output signal, and wherein the processor is further configured to:
determine the envelope of the integrated signal, based on an in-phase component and a quadrature component of the integrated signal;
calculate a scaling factor, based on the determined envelope of the integrated signal and a selected quantization level; and
produce the quantized complex oversampled output signal, by multiplication of the in-phase component and the quadrature component of the integrated signal with the scaling factor.

3. The complex DSM based transmitter as in claim 2 , further comprising an adjacent channel power ratio (ACPR) enhancement block configured to reduce an amount of noise in the RF signal.

4. The complex DSM based transmitter as in claim 3 , wherein the ACPR enhancement block comprises:
a first subtractor configured to calculate a total quantization noise as a difference between the quantized complex oversampled output signal and the complex oversampled digital signal;
a low pass filter configured to extract from the total quantization noise a band specific quantization noise; and
a second subtractor configured to subtract the band specific quantization noise from the quantized complex oversampled output signal.

5. A transmitter comprising:
a complex delta-sigma modulator (DSM) providing a complex quantized output signal of substantially constant envelope, the complex DSM comprising:
a subtractor configured to subtract a complex feedback signal from a complex digital input signal and produce a delta signal;
an integrator configured to integrate the delta signal into an integrated signal; and
a complex polar quantizer that comprises a processor configured to quantize an envelope of the integrated signal and output the complex quantized output signal of substantially constant envelope, wherein the processor is further configured to:
determine the envelope of the integrated signal, based on an in-phase component and a quadrature component of the integrated signal;
calculate a scaling factor, based on the determined envelope of the integrated signal and a selected quantization level; and
produce the complex quantized output signal of substantially constant envelope, by multiplication of the in-phase component and the quadrature component of the integrated signal with the scaling factor, wherein the complex feedback signal is obtained from the complex quantized output signal of substantially constant envelope;

a complex up-converter configured to convert the complex quantized output signal of substantially constant envelope to an input radio-frequency signal (RF IN ); and
a power amplifier driven by the RF IN substantially at saturation.

6. The transmitter as in claim 5 , wherein the complex up-converter includes: a first digital-to-analog converter (DAC) for an in-phase (I) component of the complex quantized output signal of substantially constant envelope, a second digital-to-analog converter (DAC) for a quadrature phase (Q) component of the complex quantized output signal of substantially constant envelope, and a frequency up-converter for converting analog outputs of the first DAC for the I component and the second DAC for the Q component into an RF signal in a specific RF band.

7. A method for modulating a complex digital input signal using a complex delta-sigma modulator (DSM), the method comprising:
subtracting, with a subtractor, a complex feedback signal from the complex digital input signal to produce a delta signal;
integrating the delta signal into an integrated signal; and
quantizing an envelope of the integrated signal, using a complex polar quantizer, to produce a complex quantized output signal of substantially constant envelope, wherein quantizing the envelope of the integrated signal comprises:
determining the envelope of the integrated signal, based on an in-phase component and a quadrature component of the integrated signal;
calculating a scaling factor, based on the determined envelope of the integrated signal and a selected quantization level; and
multiplying, the in-phase component and the quadrature component of the integrated signal with the scaling factor, to produce the complex quantized output signal, wherein the complex feedback signal is obtained from the complex quantized output signal.

8. A method for power amplification, the method comprising:
modulating a complex digital input signal to obtain a complex quantized output signal of substantially constant envelope, wherein modulating the complex digital input signal comprises:
subtracting, with a subtractor, a complex feedback signal from the complex digital input signal to produce a delta signal;
integrating the delta signal into an integrated signal; and
quantizing an envelope of the integrated signal, using a complex polar quantizer, to produce the complex quantized output signal of substantially constant envelope, wherein quantizing the envelope of the integrated signal comprises:
determining the envelope of the integrated signal, based on an in-phase component and a quadrature component of the integrated signal;
calculating a scaling factor, based on the determined envelope of the integrated signal and a selected quantization level; and
multiplying, the in-phase component and the quadrature component of the integrated signal with the scaling factor, to produce the complex quantized output signal of substantially constant envelope, wherein the complex feedback signal is obtained from the complex quantized output signal of substantially constant envelope;

performing an adjacent channel power ratio (ACPR) enhancement technique on the complex quantized output signal of substantially constant envelope to obtain a noise reduced quantized complex signal;
up-converting the noise reduced quantized complex signal to a radio-frequency input signal

Assignees

• Ericsson Telefon Ab L M

Inventors

• Ebrahimi Mojtaba
• Helaoui Mohamed
• Ghannouchi Fadhel
• Elsayed Fahmi
• Morris Bradley John

Classifications

• H03F3/19

  with semiconductor devices only · CPC title

• H03M7/3015 Primary

  Structural details of digital delta-sigma modulators · CPC title

• H03M7/302

  characterised by the number of quantisers and their type and resolution · CPC title

• H03F2200/451

  the amplifier being a radio frequency amplifier · CPC title

• H04L27/2614

  Peak power aspects · CPC title