Kenwood NX-220 Service Manual

Also see for NEXEDGE NX-220: Instruction manual Instruction manual Instruction manual Instruction manual Instruction manual

NX-22023of 18.432MHz (the same as the IC610), the I/O section op-erates at 3.3V and the core section operates at 1.5V. TheDSP carries out the following processes:• 4 Level FSK processing• Analog FM pre-emphasis/de-emphasis• Vocoder processing between audio codec and modula-tion/demodulation• CAI processing, such as error correction encoding• QT/DQT encoding/decoding• LTR encoding/decoding• DTMF encoding/decoding• MSK encoding/decoding• 2-tone encoding/decoding• Compressor/expander processing• Voice scrambler processing• Transmit/receive audio filtering processing• Microphone amplifier AGC processing• Audio mute processing• Modulation level processing7. Power Supply CircuitThe battery voltage (+B) is provided from the batteryterminal on the TX-RX unit (X57). The battery voltage passesthrough the 2.5A fuse (F1), and goes to the RF final ampli-fier, AVR ICs (IC504, IC902), DC/DC converter (IC506), andvoltage detector IC (IC507). The voltage detector watchesthe battery voltage. If the battery voltage is 5.6V or higher,the detector outputs High.When the VOL SW is turned on, SB1 becomes high (bat-tery voltage). DC/DC (IC506) operates if both SB1 and theoutput of the detector are high. IC506 outputs 3.8V andactivates IC502 (33M), IC503 (15M), IC501 (33A) and IC505(33C). As a result, the ASIC and DSP operate.The SBC signal becomes High after the ASIC operates,IC504 (50C), IC902 (50V) and Q501 (SB2) are turned on.When the /SAVE signal becomes High, Q512 (50C) oper-ates. Switches (Q503, Q505) are controlled by the ASIC.Q505 (50T) is turned on in transmit mode. Q503 (50R) isturned on in receive mode.When the VOL SW is turned off, the /PSW signal be-comes Low. After detecting the /PSW signal, the ASICchanges the SBC signal to Low.50C is fed to IC509 (100C). IC509, D511 and D512 con-sist of a voltage doubler. C543 is charged to 5V by 50C andswitched to C545 by the “DDCLK” control signal. The 100Ccircuit then outputs approximately +10VDC.8. Signaling Circuit8-1. Encode (QT/DQT/LTR/DTMF/2-tone/MSK)Each signaling data signal of QT, DQT, LTR, DTMF, 2-toneand MSK is generated by the DSP circuit, superimposed ona modulation signal and output from IC610. Each deviationof the TX QT, DQT, LTR, DTMF, 2-tone and MSK tone is ad-justed by changing the output level of IC603 and the result-ing signal is routed to the VCO and PLL.8-2. Decode (QT/DQT/LTR/DTMF/2-tone/MSK)The audio signal is removed from the FM detection signalsent to the DSP circuit and the resulting signal is decoded.CIRCUIT DESCRIPTION / 电路说明3.3V 运行，核心部分以 1.5V 运行。DSP 进行以下处理：• 4 级 FSK 处理• 模拟 FM 预加重 / 去加重• 音频编解码器和调制 / 解调之间的声码器处理• CAI 处理，例如纠错编码• QT/DQT 编码 / 解码• LTR 编码 / 解码• DTMF 编码 / 解码• MSK 编码 / 解码• 2 音编码 / 解码• 压缩器 / 扩展器处理• 语音扰频器处理• 发射 / 接收音频滤波处理• 麦克风放大器 AGC 处理• 音频静音处理• 调制电平处理7. 电源电路电池电压 ( + B ) 从收发单元 ( X57) 上的电池端子提供。电池电压通过 2.5A 保险丝 ( F1)，进入 R F 末级放大器、A V RI C ( I C504、I C902)、D C / D C 转换器 ( I C506) 和电压检测IC(IC507)。电压检测器监测电池电压。如果电池电压为 5.6V或更高，则检测器输出高。V O L S W 打开时，S B1 变高 ( 电池电压 )。如果 S B1 和检测器的输出都为高，D C / D C ( I C506) 将会运行。I C506 输出3.8V 电压并激活 I C502(33M )、I C503(15M )、I C501(33A ) 和IC505(33C)。从而使 ASIC 和 DSP 运行。在 ASIC 运行，IC504(50C)、IC902(50V) 和 Q501(SB2) 开启后，SBC 信号变高。当 / S A V E 信号变高时，Q512(50C ) 运行。开关 ( Q503、Q505) 由 CPU 控制。在发射模式中开启 Q505(50T)。在接收模式中开启 Q503(50R)。V O L S W 关闭时，/ P S W 信号变低。检测 / P S W 信号之后，ASIC 将 SBC 信号改为低。50C 馈送至 I C509(100C )。I C509、D511 和 D512 组成电压倍增器。C543 由 50C 充电至 5V，并由“D D C L K”控制信号切换为 C545。100C 电路随即输出约 +10VDC。8. 信令电路8-1. 编码 (QT/DQT/LTR/DTMF/2 音 /MSK)DSP 电路生成 QT、DQT、LTR、DTMF、2 音和 MSK 的各信令信号，这些信号被叠加到调制信号上并从 IC610 输出。TX QT、DQT、LTR、DTMF、2 音和 MSK 音各自的频偏通过改变 IC603 的输出电平进行调整，产生的信号被送至 VCO 和 PLL。8-2. 解码 (QT/DQT/LTR/DTMF/2 音 /MSK)音频信号从发送到 DSP 电路的 FM 检测信号中提取，产生的信号被解码。