JPH0225305B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method of performing phase modulation on a carrier wave of a specific frequency using a modulation signal of a digital signal when transmitting various data. [Prior Art] When using a digital signal as a modulation signal to perform phase modulation, conventionally, the digital signal is converted to an analog signal by a digital-to-analog converter (hereinafter referred to as DAC), and then the digital signal is converted to an analog signal by an analog circuit. is applied to the phase modulator, and finally a phase modulation signal is obtained by an analog circuit. [Problems to be Solved by the Invention] However, the characteristics of the analog circuit phase modulator change depending on changes in temperature, etc., and the value indicated by the modulation signal of the digital signal and the phase angle of the generated phase modulation signal Errors tend to occur between the two, and in order to reduce this error, the configuration of the phase modulator becomes complicated and expensive, etc., resulting in problems. [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention is constituted by the following means. That is, a first clock pulse having a high frequency that is an integral multiple of the carrier wave frequency, and a frequency corresponding to the phase change rate of the phase modulation signal, are applied to a microcomputer that has first and second counters inside. A second clock pulse having a value of The second counter is successively added or subtracted in response to the second clock pulse until the value indicated by the modulation signal and the count value of the second counter match, and each count value of the first and second counters is The processor of the microcomputer is made to repeatedly convert the added value into sine wave data and send it out, converting the sine wave data into an analog signal and generating a phase modulation signal. [Function] Therefore, the first counter repeats addition up to a certain value in response to the first clock pulse, and the count value indicates each instantaneous value of the carrier wave, while the value of the modulation signal Accordingly, the second counter performs addition or subtraction according to the second clock pulse, and the count value thereof indicates the phase modulation angle, and if the respective count values of the first and second counters are added, Since each instantaneous value of the phase modulation signal is obtained, if this is converted into sine wave data and then further converted into an analog signal, a phase modulation signal is obtained. [Example] Hereinafter, details of the present invention will be explained with reference to figures showing examples. Figure 1 is a block diagram of the entire configuration. A microcomputer (hereinafter referred to as μCP) 1 includes a processor (hereinafter referred to as CPU) 11 and a fixed memory (hereinafter referred to as ROM).
12, variable memory (hereinafter referred to as RAM) 13, and interfaces (hereinafter referred to as I/F) 15 and 16. The CPU 11 executes instructions in the ROM 12, and the required data is accessed from the RAM 13 while being predetermined. It has become a device that performs the operations of the CPU 11 or the RAM 1.
A first and a second counter are configured by specific areas in 3, which are used to generate a phase modulation signal. In addition, the data of the sine wave signal is stored as a table for at least 1/2 period in the ROM 12 or RAM 13, and this is used to control the CPU.
11 is for converting into sine wave data. In addition, μCP1 has the first and second interrupt inputs.
INT ₁ and INT ₂ , including a first clock pulse P C1 having a frequency N· _T that is an integer N times higher than the carrier frequency T of the phase modulation signal, and a first clock pulse P _C1 having a frequency N· _T that is an integer N times higher than the carrier frequency T of the phase modulation signal, Frequency _S according to
A second clock pulse P _C2 having a _value of The specified operation is repeated according to this, and the sine wave data D _S is
It is set to be sent from 16. The sine wave data D _S is converted into an analog signal by the DAC 2, but this includes quantization noise due to the digital processing of the μCP 1, which is removed by the low frequency filter (hereinafter referred to as LPF) 3 and then converted to an analog signal. ,
It is sent out as a phase modulated signal S _PM . FIG. 2 is a flowchart of steady processing by the CPU 11, in which each count value "n ₁ + n ₂ = n" 101 of the above-mentioned first and second counters is calculated,
According to the above table, “convert to D _S based on n”
Step 102 is performed, and the sine wave data thus obtained is " _Sent out" 103, and then steps 101 and subsequent steps are repeated. Here, if the constant value is N-1 and this is represented by, for example, a 3-digit binary number [111], then the count value n ₁ is [000] as described below.
~N-1 is repeated at a constant cycle according to the clock pulse P _C1 , and when the count value n ₂ is a 3-digit binary number [010] and [100], it is added to each count value n ₁ and n ₂ . The relationship with the value n is as shown in the following table.

〔Effect of the invention〕

As is clear from the above explanation, according to the present invention, when a digital signal is used as a modulation signal, a phase modulation signal is generated by digital processing, so there is an error between the value of the modulation signal and the phase angle of the phase modulation signal. Therefore, high-fidelity phase modulation can be performed without causing any distortion, and a remarkable effect can be obtained in phase modulation using digital signals.

[Brief explanation of drawings]

The figures show an embodiment of the present invention; FIG. 1 is an overall block diagram, FIGS. 2 to 4 are flowcharts showing the operating status of the processor, and FIG. FIG. 6, which is a diagram showing the relationship with count values, is a timing chart showing changes in each value and data. 1...μCP (microcomputer), 2...
DAC (digital-to-analog converter), 11...
CPU (processor), 12...ROM (fixed memory), 13...RAM (variable memory), 15, 16
...I/F (interface), INT ₁ , INT ₂ ...
...Interrupt input, P _C1 , P _C2 ...Clock pulse, S _M ...
...Modulation signal, D _S ...Sine wave data, S _PM ...Phase modulation signal.

Claims (1)

[Claims] 1 A microcomputer having first and second counters is provided with a first clock pulse having a frequency that is an integral multiple of the frequency of the carrier wave and a second clock pulse having a frequency corresponding to the phase change rate of the phase modulation signal. 2 clock pulses are applied to the first and second interrupt inputs respectively, and a modulated signal of a digital signal consisting of a plurality of bits is applied as data, and a constant value is sequentially input to a first counter in response to the first clock pulse. The second counter is successively added or subtracted in response to the second clock pulse until the value indicated by the modulation signal and the count value of the second counter match, and each count of the first and second counters is A processor of the microcomputer repeatedly performs an operation of converting the added value into sine wave data and sending it out, converting the sine wave data into an analog signal and generating a phase modulation signal. digitally controlled phase modulation method.