Chapter : Principle of FMCW Radars, PPT, Semester, Engineering - Electronics and Communication Engineering (ECE) PDF Download

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Principle of FMCW Radars

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Contents

I. Principle of FMCW radar
II. FMCW radar signal processing
III. Block diagram of an FMCW radar for precipitation measurements

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Principle of FMCW radar

frequency-modulated
continuous-wave
A radar transmitting a continuous carrier modulated by a periodic function such as a sinusoid or sawtooth wave to provide range data (IEEE Std. 686-2008).
Modulation is the keyword, since this adds the ranging capability to FMCW radars with respect to unmodulated CW radars.
We will concentrate in this talk on linear FMCW radar (LFMCW

Principle of FMCW Radars --------------------------------------------------------------------------------------------- Next Slide

Principle of FMCW radar

frequency-modulated
continuous-wave
A radar transmitting a continuous carrier modulated by a periodic function such as a sinusoid or sawtooth wave to provide range data (IEEE Std. 686-2008).
Modulation is the keyword, since this adds the ranging capability to FMCW radars with respect to unmodulated CW radars.
We will concentrate in this talk on linear FMCW radar (LFMCW).

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Single target

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Single target

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Moving single target

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Atmospheric FMCW radar

When the expected Doppler frequency shift of the target has a negligible effect on the range extraction from the beat frequency, it can be estimated by comparing the phase of the echoes of successive sweeps, e.g. for meteorological applications.
the phase of the received signal is and the change of the phase of the received signal from sweep to sweep is given as

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FMCW radar signal processing

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FMCW radar signal processing

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General block diagram of an FMCW radar

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IDRA – TU Delft IRCTR Drizzle radar

Specifications

•9.475 GHz central frequency
•FMCW with sawtooth modulation
•transmitting alternately horizontal and vertical polarisation, receiving simultaneously the co- and the cross-polarised component
•20 W transmission power
•102.4 μs – 3276.8 μs sweep time
•2.5 MHz – 50 MHz Tx bandwidth
•60 m – 3 m range resolution
•1.8° antenna half-power beamwidth

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IDRA - IRCTR Drizzle radar

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IDRA - IRCTR Drizzle radar (transmitter)

- GPS stabilised 10 MHz oscillator, for synchronisation of the whole system and data timestamp
-direct digital synthesizer (DDS) that generates the sawtooth modulation (other waveforms can be easily programmed)
-first up-conversion to the 350-400 MHz band, filtering and amplification / a power splitter provides the signal reference for the down-conversion in the receiver
-second up-conversion to the radar frequency 9.45 – 9.5 GHz (X-band)
-switch for transmitting either horizontal or vertical polarisation, and high-power solid-state microwave amplifiers

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IDRA - IRCTR Drizzle radar (transmitter)

- GPS stabilised 10 MHz oscillator, for synchronisation of the whole system and data timestamp
-direct digital synthesizer (DDS) that generates the sawtooth modulation, other waveforms can be easily programmed
-first up-conversion to the 350-400 MHz band, filtering and amplification / a power splitter provides the signal reference for the down-conversion in the receiver
-second up-conversion to the radar frequency 9.45 – 9.5 GHz (X-band)
-switch for transmitting either horizontal or vertical polarisation, and high-power solid-state microwave amplifier

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IDRA - IRCTR Drizzle radar (receiver)

receiver
- two-channel receiver to receive simultaneously the horizontal and vertical polarised echoes, that first undergo the low noise amplification and first filtering stage
-first down-conversion to the 350-400 MHz band followed by filtering and amplification
-I/Q receiver, i.e. the received signal is splitted and mixed with 90° phase difference realisations of the transmitted signal at 400 MHz in order to obtain the in-phase and the quadrature-phase components of the received signal
-after the analog-to-digital conversion, the received signal is sent to the radar control computer for signal processing