13.1.11. Real Mixer (Mixer)
The Mixer block multiplies a real input stream by a synchronized complex data stream, sample by sample.
You can use the Mixer block in a digital down converter for a radio system or a general purpose DSP application. The data has fixed-point types, and the output is the implied full precision fixed-point type.
The Mixer performs element-by-element multiplication on n channels and m frequencies.
The system specification, including such factors as the channel count and sample rates, determines the main parameters for this block. The input sample rate of the block determines the number of channels present on each input wire and the number of wires:
Number of Channels per wire = Clock_Rate/Sample_Rate
Number of Wires = ceiling(Chan_Count×Sample_Rate/Clock_Rate)
For example, a sample rate of 60 MSPS and system clock rate of 240 MHz gives four samples to be TDM on to each input wire:
If there are more channels than TDM slots available on a wire, the input wire is a vector of sufficient width to hold all the samples. Similarly, the number of frequencies (the number of complex numbers) determines the width of the sine and cosine inputs. The number of results that the Mixer produces is the product of the sample input vector and the frequency vector. The results are TDM on to the i and q outputs in a similar way to the inputs.
|Input Rate Per Channel (MSPS)||The data rate per channel measured in millions of samples per second.|
|Number of Channels||The number of real input channels.|
|Number of Frequencies||The number of real frequencies in the multiplier.|
|a||Input||The real data input to the block. If you request more channels than can fit on a single bus, this signal is a vector. The width in bits is inherited from the input wire.|
|v||Input||Indicates the validity of the data input signals. If v is high, the data on the a wire is valid.|
|c||Input||Indicates the channel of the data input signals. If v is high, c indicates the data channel.|
|sin||Input||The imaginary part of the complex number. For example, the NCO's sine output.|
|cos||Input||The real part of the complex number. For example, the NCO’s cosine output.|
|i||Output||The in-phase (real) output of the mixer, which is (a × cos). If you request more channels than can fit on a single bus, this signal is a vector. The width in bits is wide enough for the full precision result.|
|q||Output||The quadrature phase (imaginary) output of the mixer, which is (a × sin). If you request more channels than can fit on a single bus, this signal is a vector. The width in bits is wide enough for the full precision result.|
|v||Output||Indicates the validity of the data output signals.|
|c||Output||Indicates the channel of the data output signals.|