A plurality of modulation signals is generated. Each of the plurality of modulation signals includes a pilot symbol sequence having a plurality of pilot symbols. Each pilot symbol sequence is inserted at a same temporal point in each modulation signal, and each pilot symbol in the pilot symbol sequence has a non-zero amplitude. A quantity of the plurality of pilot symbols in each pilot symbol sequence is greater than or equal to a quantity of the plurality of modulation signals to be transmitted. The plurality of modulation signals are transmitted in an identical frequency band from a plurality of antennas. Each of the transmitted plurality of modulation signals includes transmission data and one of the pilot symbol sequences.

The present invention proposes a demodulator device, a receiver and a demodulation method for M-ary amplitude shift keying systems (MASK) that requires partial knowledge of the CSI, namely, the channel attenuation coefficient. Therefore, the new demodulator, receiver and demodulation method do not require the knowledge of the channel phase shift. Consequently, no complicated channel estimation techniques are required, and the system will be very robust to the system impairments such as phase noise, I-Q imbalance, etc. In this sense, the new technique is denoted as semi-coherent demodulation (SCD). To reduce the complexity of the new SCD, a suboptimal demodulator is derived which has much lower complexity than the optimal while providing almost the same error probability.

The present invention provides a method of transmitting broadcast signals. The method includes, processing input streams into plural PLPs; encoding data of the each PLPs according to code rates, wherein the encoding data of the each PLPs further includes, encoding data of at least one PLP with LDPC codes, bit interleaving the LDPC encoded data of the PLP, mapping the bit interleaved data onto a set of constellations according to the code rate, MIMO encoding the mapped data, and time interleaving the MIMO encoded data; building at least one signal frame by mapping the encoded data of the each PLPs; and modulating data in the built signal frame by OFDM method and transmitting the broadcast signals having the modulated data, wherein the bit interelaved data of each PLPs are mapped by using either QAM, NUQ, or NUC.

A compensation circuit is configured to compensate for a loss of low-frequency signal content of an input signal at a receiver input. The compensation circuit includes a switching circuit and a summing circuit coupled to the switching circuit. The switching circuit is configured to receive a first plurality of digitized values sampled from a receiver output signal. The summing circuit is configured to generate a summation signal based on a combination of a first plurality of input values selected by the switching circuit. The selecting is based on the first plurality of digitized values. The compensation circuit is configured to provide to the receiver input a compensation signal to compensate for the loss of the low-frequency signal content from the input signal. The compensation signal is based on the summation signal and is a function of at least one gain value.

A method and apparatus for generating and transmitting modulation signals includes generating a plurality of modulation signals each of which is to be transmitted from a different one of a plurality of antennas. Each modulation signal includes a pilot symbol sequence and/or a pilot subcarrier including a plurality of pilot symbols used for demodulation. Each of the pilot symbol sequences and/or pilot subcarriers is inserted at the same temporal point in each modulation signal. The pilot symbol sequences and/or pilot subcarriers are orthogonal to each other, each pilot symbol having a non-zero amplitude. The quantity of the plurality of pilot symbols in each pilot symbol sequence and/or pilot subcarrier is greater than a quantity of the plurality of modulation signals to be transmitted. The plural modulation signals are transmitted from the plurality of antennas in an identical frequency band. Each modulation signal includes different transmission data and one of the pilot symbol sequences and/or pilot subcarriers.

In accordance with an embodiment, a circuit includes a mixer having a signal input port, a local oscillator input port and an output port, a lowpass filter circuit having an input coupled to the output port of the mixer and a terminal configured to be connected to a shunt capacitor, and a difference circuit having a first input coupled to the output port of the mixer, and a second input coupled to an output of the lowpass filter. The output of the difference circuit substantially rejects a DC signal component at the output port of the mixer.

A measurement apparatus, for example a digital oscilloscope, receives an amplitude modulated (AM) signal comprising a baseband signal, having a baseband waveform, modulating a carrier signal, and reconstructs the baseband waveform. The measurement apparatus: samples the AM signal at a sampling rate which produces a plurality of data samples for each period of the carrier signal; determines the amplitude of the baseband signal for each of a plurality of periods of the carrier signal from at least some of the plurality of data samples for each period; and reconstructs the baseband waveform from the amplitudes of the baseband signal for each of the plurality of periods of the carrier signal. The measurement apparatus may display the reconstructed baseband waveform on a display device.