ERM HR C6000, Руководство пользователя

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Compression
The audio compander consists of a compressor and a decompressor to reduce the effects of noise on
audio quality.
A compressor is used at the transmitting end to reduce the dynamic range of the audio signal by
amplifying the small signal and reducing the large signal.
The Syllabic compander is used in the HR_C6000 to change the amplitude of the average envelope
of the signal according to the time constant t. The steady-state output of the compressor is the root
mean square of the input signal, that is, when the input signal is increased or decreased by 2dB, the
output signal is correspondingly increased or decreased by 1dB. Generally, in a voice
communication system, the dynamic range can be converted from 60 dB of the input signal to 30
dB of the output signal by audio compression technology. The user can open the compression
module by configuring register 0x34[6]=1’b1. It should be noted that the compressor should be
used in conjunction with decompression.
OMISSIS
Figure 6.3 Compressed Time Domain Response
At the same time, the user can set the compressor's 0dB compression point by configuring Register
0x2D[3:0].
Aggravation
The HR_C6000 provides an optional weighting module that meets the requirements of the TIA. The
weighting module processes the audio signal in the 300Hz to 3000Hz band at +6dB/Oct. The
weighting module can be turned on by configuring register 0x34[5]=1'b1.
OMISSIS
Figure 6.4 Weighted frequency response curve
Filter
The HR_C6000 provides two sets of low-pass filters with embedded soft limiters, 2.55KHz and
3KHz low-pass filters, of which 2.55KHz can be used for 12.5KHz channel spacing to provide
better ACPR specifications; 3KHz low The pass filter is typically used for channel spacing of
25KHz. Select by configuration register 0x34.
FM modulation
If the transmit RF interface of the HR_C6000 is configured for baseband IQ or IF mode, FM signal
modulation of the audio signal is performed using the FM modulator inside the HR_C6000. The
modulation offset is adjusted by configuring 0x3E and Mic gain 0x0F, while preventing
overmodulation by configuring the soft limit register 0x3F of the transmit low pass filter.
6.1.1 CTCSS send
The system determines the sub-tone rate (62.5~254.1Hz) according to the set CTCSS sending
address code (1~51). The sub-tone signal is generated by querying the sine table. Different