Analysis of 2017 Signal Source Competition Topic

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Analysis of 2017 Signal Source Competition Topic [Copy link]

1 Previous "Signal Source" Competition Topics

In the 11th National Undergraduate Electronic Design Competition, there were only 5 signal source questions:

① Signal Generator (8th session, 2007, Topic H, Vocational and Technical College Group)

② Sine signal generator (7th session, 2005, Topic A)

③ Voltage-controlled LC oscillator (6th session, 2003, Topic A)

④ Waveform Generator (5th, 2001, Topic A)

⑤ Practical Signal Source (2nd, 1995)

Signal source questions have not appeared as independent questions in recent competitions, but have appeared as part of other questions.

Example 1: 2013 Undergraduate Group E Topic “Simple Frequency Characteristics Tester” Design Requirements:

According to the zero-IF quadrature demodulation principle, a two-port network frequency characteristic tester is designed and manufactured, including amplitude-frequency characteristics and phase-frequency characteristics. An orthogonal sweep frequency signal source is designed and manufactured, with a frequency range of 1MHz~40MHz, a frequency stability of ≤10-4, and a frequency that can be set, with the minimum setting unit being 100kHz. The frequency characteristic tester has an input impedance of 50Ω and an output impedance of 50Ω. Point frequency measurement can be performed, with the absolute value of the amplitude-frequency measurement error being ≤0.5dB, and the absolute value of the phase-frequency measurement error being ≤5.

The RLC series resonant circuit is used as the network under test. The DDS chip used as the signal source is specified, AD9854ASVZ (with

AD9854ASQ equivalent).

Example 2: Design requirements for the 2011 undergraduate group E topic “Simple digital signal transmission performance analyzer”:

Design and make a simple digital signal transmission performance analyzer to realize digital signal transmission performance testing; at the same time, design and make three low-pass filters and a pseudo-random signal generator to simulate the transmission channel.

Design and make a digital signal generator: the digital signal V1 is an m sequence of f1(x) =1+x2 +x3 +x4+x8, and its clock signal is V1-clock; the data rate is 10~100kbps, adjustable in 10kbps steps. The output signal is TTL level.

Design and create a pseudo-random signal generator to simulate channel noise: the pseudo-random signal V3 is f2(x)

=1+x+x4+x5+x12 m sequence; the data rate is 10Mbps, the peak-to-peak value of the output signal is 100mV, and the clock signal V1-clock generated by the digital signal generator is used for synchronization. The signal eye diagram of the digital signal V2a is displayed, and the eye amplitude is tested.

Example 3: 2013 National Undergraduate Electronic Design Competition Comprehensive Assessment Question Design Requirements:

Use the 555 chip on the comprehensive test board specified in the question and a general-purpose quad op amp 324 chip to design and make a waveform generator. The design and production requirements are as follows:

At the same time, the four channels output, each channel outputs one of the waveforms of pulse wave, sawtooth wave, sine wave I, and sine wave II, and the load resistance of each channel output is 600 ohms. The frequency relationship of the four waveforms is 1:1:1:3 (3rd harmonic): the output frequency range of pulse wave, sawtooth wave, and sine wave I is 8kHz-10kHz, and the peak-to-peak value of the output voltage amplitude is 1V; the output frequency range of sine wave II is 24kHz-30kHz, and the peak-to-peak value of the output voltage amplitude is 9V; the output waveforms of pulse wave, sawtooth wave and sine wave should have no obvious distortion (when measured with an oscilloscope). The frequency error is not more than 10%; the peak-to-peak error of the output voltage amplitude in the passband is not more than 5%. The duty cycle of the pulse wave can be adjusted. The power supply can only use a +10V single power supply, which is supplied by a regulated power supply.

Note: Do not add 555 and 324 chips, and do not use any other devices or chips except those on the integrated test board.

2. Key knowledge points of previous “Signal Source” competition questions

Based on the previous "Signal Source" competition questions, the main knowledge points that students who focus on the "Signal Source" competition questions need to understand are as follows:

Use MCU + DAC to generate various signals

Use dedicated DDS chip + MCU to generate various signals Use FPGA to generate various signals DAC circuit design and production Filter circuit design and production DDS interface circuit design and production Power amplifier circuit design and production Power supply circuit design and production MCU minimum system design and production

Design and manufacture of frequency, period and other parameter measurement circuits

Example 1: Signal Generator (2007 H, Vocational and Technical College Group)

You are required to design and make a signal generator (Note: this question is based on the sine signal generator in Question A in 2005). Knowledge points to be mastered:

Use dedicated DDS chips (such as AD9834, AD9852, etc.) and microcontrollers to generate sine, square and triangle wave signals

Implemented using FPGA (Xilinx's DDS v5.0 DDS IP core, Altera's DDS IP core)

Design and manufacture of DDS function DAC (e.g. MAX5181/MAX5184, AD9740) circuits Design and manufacture of variable gain amplifier circuits (e.g. AD603) Design and manufacture of power amplifier circuits (e.g. THS3001 current feedback amplifier) Design and manufacture of power supply circuits

Design and production of single chip microcomputer minimum system

Example 2: Sine Signal Generator (2005 Problem A)

It is required to design and make a sine signal generator. Knowledge points to be mastered:

Use a dedicated DDS chip (such as AD9852, etc.) and a single-chip microcomputer to generate a sine wave signal

Use FPGA (Xilinx's DDS v5.0 DDS IP core, Altera's DDS IP core) to implement DDS function

Design and manufacture of filter circuits (e.g. 7th order Chebyshev filter using inductors and capacitors) Design and manufacture of DDS interface circuits

Design and manufacture of amplifier circuits (e.g. AD8320) Design and manufacture of power supply circuits

Design and production of single chip microcomputer minimum system

Example 3: Voltage-controlled LC oscillator (2003 Problem A)

You are required to design and make a voltage-controlled LC oscillator. Knowledge points to master: Design and make voltage-controlled oscillator circuits (e.g. voltage-controlled oscillator chip MC1648 + varactor diode MV209)

Digital phase-locked loop frequency synthesizer circuit (for example, PLL MC145152 + pre-divider MC12022 + VCO

Design and production of MC1648+loop filter LM358 and RC) Design and production of FPGA minimum system Design and production of peak-to-peak detection circuit Design and production of frequency measurement circuit Design and production of high-frequency power amplifier circuit

Filter circuit design and production Power supply circuit design and production Single chip microcomputer minimum system design and production

LED or LCD display circuit design and production Example 4. Waveform generator (2001 A question)

Required to design and make a waveform generator. Knowledge points to master: Generating waveforms using direct digital frequency synthesis (DDFS) technology Design and production of crystal oscillator and phase-locked loop circuits Design and production of special memory dual-port RAM circuits Design and production of waveform generation circuits Design and production of filter circuits Design and production of amplitude-stabilized output circuits Design and production of single-chip microcomputer minimum system 5. Practical signal source (1995)

You are required to design and make a practical signal source. Knowledge points to be mastered: Using a single chip microcomputer + DAC to generate a sine wave signal. Design and make a comparator circuit. Design and make a filter circuit.

3. Some suggestions for training on “Signal Source” competition questions

Although signal source topics have not appeared in recent competitions, they may appear as signal sources in works in radio, instrumentation, data acquisition and processing, etc. Therefore, they are still an important training content that cannot be ignored in competition training.

Each team must master several basic knowledge and techniques related to signal generation, circuit design and production (for example: DDS, FPGA, oscillator circuit composed of operational amplifiers, power amplifier circuits, filter circuits, impedance matching, etc.).

These contents serve as basic training for the competition and can be carried out before grouping (dividing the competition topics).

According to the design requirements of the comprehensive assessment questions of the National College Student Electronic Design Competition in 2011 and 2013, teams that have the opportunity to win the national first prize need to strengthen training in this area after completing the 4-day and 3-night competition.