IC-756Pro2_Technical_report.pdf

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1、TECHNICAL REPORTTECHNICAL REPORTTECHNICAL REPORT 2 CONTENTS 11. Profile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 12. Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 13. Front and rear panel . . . . . .

2、. . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3-1 Front panel 3-2 Rear panel 14. What is DSP in radio Communication? . . . . . . . . . . . . . . . . 10 15. Circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5-1 Digital IF filter 5-2 Digital functions 5

3、-3 PSN modulation 5-4 Manual notch 5-5 Speech compressor 5-6 Microphone equalizer 5-7 RTTY demodulator 5-8 Receiver 5-9 Transmitter 5-10 Dual-watch function 5-11 Real-time spectrum scope 5-12 Voice record/playback function 5-13 PLL circuit 16. Connection to option/peripheral units . . . . . . . . .

4、. . . . . . . . 25 6-1 ACC Sockets 6-2 HF/50MHz, 1kW linear amplifier 6-3 Interface for digital mode 6-4 External control unit for voice memory keyer 6-5 Installation of UT-102 optional Voice Synthesizer Unit 17. CI-Vcontrol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5、 . 28 7-1 Remote jack 7-2 Data format of CI-V 7-3 List of commands 18. Inside Views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 19. Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 10. Specifications . . . . . . . . . .

6、 . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 10-1 General 10-2 Transmitter 10-3 Receiver 10-4 Antenna tuner 11. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . foldout 3 The IC-756PROII is the high performance HF transceiver of choice for todays discrim

7、inating amateur radio operator. Icoms engineers took cutting-edge digital technology and paired it with Icoms extensive experience with analog technology. The result is a major advancement of Icoms original digital IF filter which, in the earlier IC-756PRO model, enjoyed a great reputation around th

8、e world. The IC-756PROII uses the same 32-bit floating point DSP and a 24-bit A/D-D/A converter as the IC- 756PRO. It is now possible to execute the digital IF filter, noise reduction and the digital IF filter in the AGC loop processing, and to select the soft/sharp filter shapes. The IC-756PROII em

9、ploys exclusive DSP/analog circuit matching to further improve receiver performance. Icoms engineers analyzed the influence of the AGC loop upon the received audio, matching it to an analog circuit suitable for the dynamic range of the A/D converter and the other parts used, and also re-examined the

10、 core stage of the receiver (ranging from RF top to mixer circuit), to distribute the mixer levels properly. As a result, the matching of digital and analog technology has attained a level never before achieved. This technical report does not explain in depth all the digital engineering with its man

11、y calculations and formulas. Instead, it focuses on the DSP engineering in an easy-to-understand manner. This report also explains why the 32-bit floating point DSP and 24-bit A/D-D/A converter are included. The dynamic range of the 32-bit floating point DSP and the 24-bit A/D-D/A converter may seem

12、 to be an over specification for amateur radio. But this is not the case. This technical report helps clarify these points. It is Icoms hope that in providing you with this report you will discover the IC-756PROIIs many digital advantages. Enjoy! 4 32-bit floating point DSP and 24-bit A/D-D/A conver

13、ter The adoption of a 32-bit floating point DSP and 24-bit A/D-D/A converter in the IF stage (36kHz) was originally developed by Icom. It enables various digital functions which amateur radio operators desire. I 51 types of digital IF filtering The digital IF filter has superior filtering performanc

14、e and a distinguished shaping factor that demonstrates the power of 32-bit floating point DSP. The digital filter is completely free from deterioration due to deviations in band characteristics, temperature change, or mechanical vibration, all of which have been observed in analog filters. It also p

15、rovides excellent ripple characteristics that have never been available with analog filters. The passband (50Hz3.6kHz) of the digital IF filters used for IC-756PROII come in 51 types. This function allows 3 of these 51 types to be pre-set for each mode and to be changed instantaneously by using the

16、filter button, depending on the situation. I 2 types of filter shape (Sharp/Soft) Changing the IF filter shape is a feature that is not available with analog radios. Select the filter shape from two types, Sharp and Soft, depending on the purpose, operating band, band conditions, etc. It is possible

17、 to set CW and SSB filter characteristics independently and also select the filter shape while actually receiving a signal. I Digital IF filter in AGC loop The digital IF filter, manual notch filter, etc. are located in the AGC loop, using DSP, which completely eliminates interference from adjacent

18、strong signals. This allows the AGC to be operated only on the selected frequency. It is also possible to pre-set the operation of AGC in each mode in accordance with 13 types of time constants. I Digital twin PBT The IC-756PROII is equipped with DSP based twin PBT filtering. It provides excellent p

19、erformance on a completely different level than analog filters. Set the frequency, and then adjust the passband width of the received signal in steps of 50Hz using the dedicated two- position knob. The passband width and direction of shift may be graphically displayed on the LCD, if the operator cho

20、oses. I High-accuracy digital modulation and demodulation in all modes The DSP unit allows you to increase transmit/receive audio levels, modulation, and demodulation even while decoding RTTY. This makes it possible to set the passband width of the IF filter for SSB transmit to 3 different stages. T

21、he DSP unit also provides a demodulation level suitable for high-grade HF performance and high- fidelity sound. I Manual notch with superior attenuation level The IC-756PROIIs manual notch filter has extremely sharp characteristics for processing in the DSP and provides tremendous performance for at

22、tenuation levels 70dB. Analog notch circuits are susceptible to fluctuations in attenuation or changes in temperature. The DSP-based manual notch provides stable performance and is not susceptible to such changes. Also, the DSP signal processing executed within the AGC loop completely shuts off unde

23、sirable signals, even with the AGC set to high speed. An automatic notch is included to further enhance receiver performance. I Demodulator/decoder for RTTY This transceiver is equipped with a demodulator and a decoder for BAUDOT RTTY as a standard feature. On-air station calls may be recognized ins

24、tantaneously by reading the received RTTY message directly on the IC-756PROIIs LCD no personal computer or external components are required. The transceiver is fitted with an on-screen tuning indicator that allows the RTTY to be fine tuned with ease. A DSP based twin-peak audio filter further improv

25、es the S/N ratio. This filter will reduce interference that appears between each tone (mark and space), which cannot be removed by conventional analog filters. This twin-peak audio filter works to capture noise-level signals accurately and to significantly reduce the generation of noise distortion.

26、I New-generation speech compressor The DSP based speech compressor enhances the readability of your transmitted signal at a receiving station without any distortion, even when the compression is set to a high level. The gradation of voice processing is extremely close to the original sound. This ass

27、ures superior sound quality at all compression levels. I Microphone equalizer (enables 121 different settings) The IC-756PROII is equipped with a microphone equalizer that makes it possible to set the frequency characteristics of the transmitted signal in 11 different stages for both the high-tone r

28、ange and the low-tone range. Considering all permutations, this provides for a total of 121 different settings. With this flexibility of DSP based waveform shaping, it is possible to adjust transmit audio quality depending on the application. For example, it is possible to set the dynamic sound qual

29、ity for “Pileup” or to set pleasant sound for “Ragchewing”. I Variable level type noise reduction The 32-bit floating point DSP has excellent calculation performance, which processes complex and sophisticated algorithms. This allows the DSP to attenuate noise without delay and extracts noise-level s

30、ignals. It is possible to vary the suppression level in 16 stages. I CW keying waveform shaping function DSP controls the rise and fall of the CW transmit waveform. The result is a proper CW waveform. The rise/fall timing is selectable to 4 stages of 2ms, 4ms, 6ms and 8ms. This makes it possible to

31、set a “Soft” or “Hard” CW signal, depending on your preference. 455 kHz 36 kHz 3Lo Manual NOTCH IF Filter DET AGC AGC DSP DAC DACADCAF 100W 2.5ms/Div2.5ms/Div 100W Speech compressor onSpeech compressor off RTTY reception screen 2. Features 5 Enhanced functions I Advanced receive functions The RF sta

32、ges front-end receive mixer is designed in a 4-element configuration. In the IC-756PROII, this configuration is used in the BPF stage at the RF top. Each element is examined to tune the circuit after RF stage to mixer, which makes it possible to enhance the receive performance. This significantly re

33、duces 3rd and other order distortion and provides a wide dynamic range. This means the IC-756PROII will accurately capture weak signals that analog type radios cannot hear, even in low bands with high noise levels. I Real-time spectrum scope A real-time spectrum scope is recognized as indispensable

34、for DX hunting. The IC-756PROIIs spectrum scope uses two colors to display all RF signal activity within a user-selectable bandwidth. One color indicates real-time RF signal activity, while the other color provides peak hold indication. The spectrum scope may be used for sophisticated applications s

35、uch as identifying the band conditions, quick discovery of stations, and confirmation of interval or call-back frequency. Additionally, you may monitor normal band conditions, while you display sub readout or transmit markers. In case of high- band noise, the IC-756PROII is equipped with an attenuat

36、or (10/20/30dB) dedicated to the spectrum scope, which allows a reduction of total signal level at the band scope without affecting the received signal. I Exceptionally clear SSB transmit signal Using Icoms advanced digital PSN modulation, the IC-756PROII emits high-quality signals, which makes its

37、transmitter suitable for use as the exciter of a linear amplifier. Unwanted sidebands and carrier leaks are almost completely eliminated. Further, the transmitter employs a wide band power amplifier that incorporates highly reliable bipolar transistors (2SC5125 2). The linearity and IMD characterist

38、ics achieve superior signal quality never before seen in any amateur redio transceiver. This makes it possible to transmit RF signals with significantly reduced distortion. I Built-in high-stability reference crystall oscillator The IC-756PROIIs transceiver exhibits excellent frequency stability of

39、0.5ppm. This assures stable communication even for RTTY and SSTV modes for which particularly high frequency stability is required. The best in operating convenience and features I Dual-watch Dual-watch enables simultaneous two-frequency receive in the same band, providing identical band and filter

40、configurations in both receive systems. This makes it possible to receive two signals simultaneously as if two separate receivers are being used. This greatly enhances split frequency operation; enjoy enhanced DX-operation by searching for pickup frequencies while watching the transmit frequency of

41、a DX station experiencing pile-up. Or have a QSO while simultaneously monitoring a DX net. I Triple band stacking register With the push of a band button, get quick memory recall of three preferred operating settings (including antenna port) per band. Band or mode hopping has never been easier. Its

42、the ultimate in multi- mode flexibility. I Digital Voice Recorder (DVR) The DVR feature is an indispensable function for DX hunting and contests. The IC-756PROII is equipped with a DVR with 4 channels for transmit and 4 channels for receive, for a total of 8 channels. High quality digital mapping of

43、 the transmitted or received analog signal provides high quality audio reproduction, resulting in a natural sounding voice without any noticeable degradation. It is also possible to use these 4 communication channels by allotting them freely with a total recording time of 90 seconds. Each of the 4 c

44、hannels for receive has a recording time of 15 seconds, or 60 seconds total. Press the key once in any TFT display mode and it becomes possible to not only record or reproduce voice but also to record for up to 30 minutes continuously. The receive audio may be reproduced for the most recent 15 secon

45、ds back to an interruption in recording. By constructing the simplified control unit (page 26) and connecting it to the microphone connector, digital voice recorder function may also be operated. I Full-scale electronic keyer Plug a CW, iambic paddle into the electronic keyer jack on the front panel

46、. Especially handy during long hours of operation, it is possible to set the CW speed between 7 and 56WPM. The discriminating operator may also set the dot/dash keying ratio (2.8:1 to 4.5:1) and polarity, depending on preference. The keyer may also be set for either right or left hand use. For the C

47、W operator who prefers not to use the IC-756PROIIs built-in electronic keyer, an ordinary key jack is available on the rear panel, for bug or straight key and is fully compatible with external keyers or PC keying. I Multi-function memory keyer Enhance your contest operations. The IC-756PROII is full

48、y equipped with a convenient memory keyer, offering features such as memory content editing function, auto-repeat function, serial contest number automatic count-up function, contest number abbreviating function, and more. These features will reduce effort when repeating a formatted contents for cal

49、ling CQ, continuous transmission of call sign, or contests. Since it is possible to confirm the contents of memory on the display, transmission mistakes are eliminated. Construct the simplified control unit (page 26) and connect it to the microphone connector to enhance operation of these memory keyer functions. Real-time spectrum scope screen DVR key High-stability reference crystal oscillation unit 6 I Quick split function When the split button is pressed and held, the frequency of the sub- VFO is adjusted to the frequency in the main VFO. Using the split function, it is also p