A broadband signal phase modulator and its modulation method

Abstract

The invention provides a broadband signal phase modulator and a modulation method applied to a polar coordinate transmitter, including two parts of a control information memory and a direct digital frequency synthesizer. The output end of the control information memory is connected to the control end of the direct digital frequency synthesizer, and the phase modulation is realized by controlling the frequency division parameters. The direct digital frequency synthesizer synthesizes the fractional frequency division signal based on the idea of ​​time averaging, and consists of a variable frequency divider and a quantization system. The output terminal of the quantization system is connected to the frequency division control terminal of the variable frequency divider to realize the adjustable frequency division value. The output end of the variable frequency divider is connected to the clock control end of the quantization system to ensure that the instantaneous frequency of the output signal of the quantization system will only change at the zero crossing point. The quantization system uses an efficient quantization method to reduce fractional spurs introduced by direct digital frequency synthesizers. Since the present invention is implemented using an open loop structure, the bandwidth of the phase modulation signal is not limited by the loop.

Description

technical field [0001] The technology relates to the field of wireless communication technology, in particular to the phase modulation technology of a coordinate transmitter. By using an open-loop phase modulation structure, the bandwidth of the phase-modulated signal is not limited by the system loop. Background technique [0002] Compared with the traditional Cartesian transmitter using I / Q quadrature modulation, the polar coordinate transmitter evolved from the EER transmitter has received a lot of in-depth research due to its advantages of high efficiency and easy integration. The polar coordinate transmitter is different from the rectangular coordinate transmitter. It needs to convert the I / Q rectangular coordinate information into polar coordinate ρ / θ information and then amplify them separately, and finally combine them into a rectangular coordinate modulation signal for transmission. Therefore, the amplitude and phase of the transmitted signal Information separation...

AI Technical Summary

Problems solved by technology

[0004] However, the phase modulation method based on the phase-locked loop also has some disadvantages: during the modulation process, precise frequency control of the voltage-controlled oscillator is required to prevent the accumulation of phase errors; the frequency division ratio of the phase-locked loop is extremely high, which reduces the phase noise index of the output signal

In the actual application test, the modulation characteristics of this method have good performance at the low end and high end, but there is a fault in the middle section, that is, it cannot be well connected in the entire modulation frequency band.

For another example, a digital predistortion filter can be used to linearly compensate the loop filter. However, the added predistorter will increase the size and weight of the circuit, which is not conducive to the miniaturization of modern communication terminals. On the other hand, simply introducing a predistortion Distortion technology has a certain impact on the insertion and return loss of the filter, and causes the increase of the filter group delay and deteriorates the communication quality

In addition, introducing a phase modulation signal from the output summing node of the voltage controlled oscillator can solve the problem of loop bandwidth limitation, but the resulting output impedance mismatch of the summing node will lead to an increase in the output spur of the phase-locked loop

[0006] From the above analysis, it can be seen that the improvement scheme of the traditional phase modulation method can increase the modulation bandwidth and performance to a certain extent, but these schemes have certain defects themselves, and cannot fully meet the high bandwidth requirements of the phase modulation signal for the circuit

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