Pulse density modulator used for TD-SCDMA and 4G terminal

Abstract

The invention proposes a pulse density modulator used for a TD-SCDMA terminal, a Beyond 3G terminal and a 4G terminal. The pulse density modulator (PDM) comprises a DSP interface, a clock gate control unit, a clock frequency divider, an accumulator, an OR gate, an output register, a reset circuit and an output control circuit. The output of the pulse density modulator is a simulation value generated by a simulation low-pass plate external filter. When the PDM outputs a high level signal, the voltage is very close to the source voltage Vcc; when the PDM outputs a low level signal, the voltage is very close to the ground voltage GND. The pulse density modulator (PDM) can have high resolution expressed by the multi-bit and output all voltage values in the range from the logic low level to the logic high level. The output of the pulse density modulator (PDM) can be set to be in a high resistance state; the refresh speed of the pulse density modulator (PDM) can be set by a DSP or a DSP software / firmware. When a plurality of pulse density modulators (PDM) are in use, all pulse density modulators (PDM) can be divided into groups; each group can include a plurality of pulse density modulators; each group of PDM can be enabled separately; the groups are controlled by the PDM clock enabling signal; each group of PDM is provided with a reset circuit; the PDM is reset and initialized to be in the high resistance state when the pulse density modulator (PDM) receives the reset signal of the DSP each time. When the pulse density modulator (PDM) is set to be the high rail level output or in the high resistance state, the internal clock frequency divider in the pulse density modulator (PDM) stops operating.

Description

technical field [0001] The invention provides a pulse density modulator for TD-SCDMA, B3G (Beyond 3G), 4G (fourth generation mobile communication) terminals, which belongs to the field of mobile communication technology manufacturing. Background technique [0002] In digital signal processing, it is often necessary to convert multi-bit digital signals into one-bit digital signals. For example, in the field of communication, the receiver needs to convert the encoded digital voice signal into an analog signal, that is, restore the original analog voice signal. Coded speech signal, usually a multi-bit bit stream. Therefore, how to convert multi-bit bit streams into analog voice signals has become the key to ensuring communication quality. As another example, in some control circuits, the control signal is a multi-bit digital signal generated by calculation, and these digital signals must be converted into analog signals to control the circuit. Therefore, how to convert multi...

AI Technical Summary

Problems solved by technology

For example, when the number of digits of the digital signal to be modulated increases, the modulation period becomes longer accordingly, and the response speed of the filter becomes slower accordingly.

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