Phase/gain imbalance estimation or compensation
View Patent ↗Apparatus and methods for estimation and compensation of phase imbalance and gain imbalance are provided. A receiver for estimation or compensation of phase imbalance or gain imbalance utilizing a QPSK modulation and a modulation scheme based on a complex scrambling code includes means for estimating the phase imbalance or gain imbalance prior to symbol synchronization. Thus, the phase imbalance and gain imbalance will not introduce losses in subsequent phases of signal processing.
1. A receiver for estimation and compensation of phase imbalance or gain imbalance, the receiver comprising:
a first circuit structured to estimate the phase imbalance or gain imbalance of I and Q components of an incoming complex signal prior to symbol synchronization, the first circuit structured to generate as an output a ratio of the product of compensated I and Q components and the square of the compensated I component, the first circuit including a first multiplier structured to receive the compensated I and Q signals and to generate a product thereof, and a second multiplier structured to generate the square of the compensated I component, a divider structured to divide the product of the first multiplier by the product of the second multiplier, and an integration circuit that is structured to integrate the output of the divider and to output an integration signal; and
a second circuit structured to receive as inputs the uncompensated I and Q components and the output of the first circuit and to output on output terminals the compensated I and Q components.
2. The receiver of claim 1 , wherein the first circuit is structured to receive as inputs the I and Q components of the complex signal after demodulation and compensation.
3. The receiver according to claim 1 , wherein the first circuit comprises a low pass filter structured to low pass filter the product of the compensated I and Q components and low pass filter the square of the compensated I component.
4. The receiver of claim 1 , comprising a synchronizer having input terminals coupled to the output terminals of the second circuit, the synchronizer comprising a UMTS synchronizer.
5. A circuit comprising:
a first circuit having a first multiplier structured to receive I and Q components of an incoming I/Q modulated signal and a second multiplier structured to receive the I component, and a first divider circuit structured to divide an output of the first multiplier by an output of the second multiplier, the first circuit structured to generate as an output a ratio between a cross correlation of the I and Q components and a mean value of a square of the I component;
a second circuit structured to receive an integration signal from the divider circuit and to receive uncompensated I and Q components of the incoming I/Q modulated signal, and to output on an output terminal of the circuit compensated I and Q components; and
a third circuit having a multiplier structured to receive the Q component, and a second divider circuit structured to receive an output of the second multiplier of the first circuit and an output of the multiplier of the third circuit, and further structured to generate as an output a ratio between the output of the second multiplier of the first circuit and the output of the multiplier of the third circuit.
6. The circuit of claim 5 , wherein the first circuit is structured to receive as inputs the I and Q components of a complex signal after demodulation and compensation.
7. The circuit of claim 5 , wherein the first circuit comprises a low pass filter structured to low pass filter the output of the first multiplier and a low pass filter structured to filter the output of the second multiplier, the divider circuit having inputs structured to receive the output of both low pass filters.
8. the circuit of claim 5 , comprising a synchronizer having input terminals coupled to output terminals of the second circuit, the synchronizer comprising a UMTS synchronizer.