DOCSLIB.ORG

Generating Precise FMCW and Chirp Radar Test Signals with Low-Cost Devices

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Generating Precise FMCW and Chirp Radar Test Signals with Low-Cost Devices TECHNICAL BRIEF Generating Precise FMCW and Chirp Radar Test Signals with Low-cost Devices RF/microwave signal generators offering high speed frequency modulated continuous wave (FMCW) and frequency modulation on pulse (FMOP), or “chirp” capabilities, are depended on by radar system engineers in many fields. In particular, those designing microwave test sets for receivers in highly precise radar systems, such as anti-spoofing and anti-jamming applications. To achieve the reliable FMCW and chirp modulation necessary, one would typically rely on a full-featured bench-top unit. But many are discovering that today’s robust, portable, and programmable RF/microwave signal generators offer a real, low-cost, and flexible alternative. This Tech Brief provides insight on this self-managed approach and offers tips and tricks on how to get up and running fast and with confidence in every pulse. TECHNICAL BRIEF Generating Precise FMCW and Chirp Radar Test Signals with Low-cost Devices Intoduction ........................2 FMCW and Chirp Modulation Radar .....3 The Signal Generator’s Key Role ........5 Chirp Radar Field Test Challenges .......6 Anti-jamming/Anti-spoofing Radar Test with Multiple Signal Generators .....6 Conclusion ........................7 Testing in Remote Locations or in Harsh Conditions is a Challenge for Traditional Bench-top Test Instruments. Frequency modulated continuous wave However, there are still uses and the laboratory or the field. In the (FMCW) radar technology was devel- benefits to older radar techniques, case of field testing, chirp radar can oped back in the 1950s following such as linear FMCW for aircraft height be found in harsh environments from World-War II to provide better resolu- measurement during landing proce- remote radar locations, naval plat- tion and discrimination of radar dures, automotive radar, smart ammu- forms, aircraft maintenance facilities, targets. Once unclassified in the 1960s, nition sensors, liquid filling levels of or even servicing land-mobile systems there has been steady development of tanks and bulk solids in silos, and wherever they may be. radar technology beyond a simple naval tactical navigation radar. linear FMCW chirp to more advanced Given that a significant amount of radar technologies, such as coherent An extremely useful tool in develop- FMCW and chirp radars use frequen- pulsed radar using pulse compression ment and testing of FMCW radar and cies well into the microwave and techniques. These techniques have more advanced chirp radar is a signal millimeter-wave spectrum, such as resulted in frequency modulated chirp generator with frequency sweeping C-band, X-band, and Ku-band, the test (FM Chirp), barker codes, and other and with chirp modulation, which may equipment used to develop and test more complex modulated pulse also be used to develop and test pulse these radars are general large bench- compression radar techniques. compression techniques and devices in top devices with a wide range of www.vaunix.com Page 2 TECHNICAL BRIEF Generating Precise FMCW and Chirp Radar Test Signals with Low-cost Devices built-in features and a price-tag to re-calibrate, which most often must be modulation. Fortunately, Vaunix match their size. Moreover, large done at a certified facility taking weeks produces LabBrick signal generators bench-top signal generators are of lead time on repairs. that are portable, programmable, and typically designed for laboratory can produce self-triggered and exter- conditions, and usually don’t operate A modern and much more viable nally triggered chirp modulation, phase well in extreme environments. This is solution for many space constrained continuous linear frequency sweep, especially true if there is a substantial and rugged applications is the use of and pulse modulation. These devices amount of vibration or shock forces a portable signal generator. However, aren’t much larger than a standard occurring during transportation of most of the portable signal generators wallet, and are available at a fraction these units. Along with a high price- on the market do not reach common of the cost of repairing a typical tag, these bench-top units are also FMCW and chirp radar bands, and bench-top signal generator with generally expensive to repair and don’t offer any form of chirp or pulse the same capabilities. FMCW and Chirp Modulation Radar FMCW modulation is similar to contin- FMCW waveforms are sawtooth, The basic concept of FMCW modula- uous wave (CW) radar modulation triangular, square-wave, and stepped, tion is that the received signal from with the exception that instead of or staircase, modulation, though the an object is mixed with the transmitted holding a single tone the frequency most common is saw-toothed or signal producing an intermediate of the CW radar increases or decreases “swept-frequency” FMCW radar. frequency (IF) tone that is proportional linearly, or non-linearly. Common to the delay, hence distance to the object. Multiple objects will produce multiple tones, which can be separated f f and identified using a Fourier Trans- t Δ TX Chirp form. The result is an FMCW radar that RX Chirp consists of a relatively simple circuit with a transmitter, receiver, FMCW Δ f synthesizer, mixer, digitizer, signal fD S processor, and display. In the case of t1 t t a radio altimeter, the IF signal is sent f directly to an analog gauge with a A TC frequency dependent coil meter that exhibits greater inductive impedance at higher frequencies (though not linear, IF Signal this is still an effective method for t S determining relative altitude). f t (Top) FMCW “chirp” signal as a function of time and FMCW radar response and processing. frequency. (Bottom) FMCW “chirp” signal as a function of amplitude and time www.vaunix.com Page 3 TECHNICAL BRIEF Generating Precise FMCW and Chirp Radar Test Signals with Low-cost Devices The benefits of FMCW over CW is that function of pulse width. However, high range resolution experienced by pulse the frequency modulation allows for pulse powers and short pulse widths radars with long pulse widths while much closer minimum range measur- require specialized high power modula- maintaining a high energy pulse ing capability, which is roughly limited tors and transmitters, which are without extremely high peak power to the transmitted signals wavelength. generally large and expensive. Using levels. Frequency modulation on pulse, Moreover, FMCW radar enables the solid-state technology, a pulsed radar or FMOP, is often referred to as “chirp” simultaneous measurement of a can be made much smaller at a radar, though somewhat confusingly, target’s range and its relative velocity possible cost savings, though sol- linear frequency modulation is also with much higher accuracy range id-state technology typically doesn’t often called a chirp signal. measurements than CW. FMCW outperform vacuum tubes in high modulation also can be used to frequency and high pulse power Additional benefits of chirp radar discriminate between multiple targets, applications. is that the broadband and random requires relatively simple circuitry, and distributed noise in the receiver is doesn’t require any pulsing with high Hence, the use of intrapulse modula- greatly reduced by the pulse compres- peak powers. tion and pulse compression allows for sion filtering process, which allows for longer pulse widths at relatively high the sensing of signal returns that are An advancement of this technique is power levels. By modulating a pulse, below the noise floor of the pulse. to combine pulse radar concepts with the benefits of range resolution and This is commonly known as the pulse intrapulse modulation/pulse compres- multi-object discrimination can be compression gain (PCG). Moreover, sion. Pulsed radar performance achieved. Pulse compression is a the pulse compression filter adjusts benefits from extremely high pulsed technique where a longer pulse is the relative phases of the receive signal power and short pulse width, as a processed in shorter sub-pulse seg- frequency components, which actually pulse radar’s range resolution is a ments, thus mitigating the loss of yields better maximum range than -3dB f1 ∑ f2 ∑ f3 VCO ∑ f4 ∑ f5 f5 f4 f3 f t 2 f1 t D A A D f1 f2 f3 f4 f5 FMCW radar block diagram A diagram of the pulse compression circuitry for a linear FM chirp radar. www.vaunix.com Page 4 TECHNICAL BRIEF Generating Precise FMCW and Chirp Radar Test Signals with Low-cost Devices t t The input and output signals of a pulse compression state with the receive signal within the noise and output echo clearly discernible. would be predicted by the standard advanced driver assistance systems circuitry. Long test ranges and precise radar range equation. This phenome- (ADAS), and aerospace altimeter and positioning of radar targets would non is known as the pulse compression other sensing applications. There are otherwise be required to test radar in ratio (PCR). also many legacy radar systems that the field, where a signal generator with are still in use today in aircraft and the appropriate modulation could be The performance of FMCW and chirp naval ships that require servicing used instead to simulate radar targets. radar depend on the performance of and retrofit testing. Moreover, high purity signal generators the radar components. Hence, added can also be used to test the radar noise/noise figure, linearity, phase Signal generators are a key test receivers signal-to-noise (SNR) perfor- noise, and spurious harmonics are all instrument for radar testing, and mance, which can be used to deter- key parameters for the active compo- are most often used to gauge the mine the maximum range capability nents within a radar system. While any performance of the radar receiver of the radar and if that falls within the of the active and passive components within a radar’s transmit/receive signal chain can substantially degrade the Transmitter performance of the radar system, it is Up Conversion extremely important that the frequency Base-band signal synthesizer excels.
Load more

Recommended publications
  • Chirp Presentation
    Seminar Agenda • Overview of CHIRP technology compared to traditional fishfinder technology – What’s different? • Importance of proper transducer selection & installation • Maximize the performance of your electronics system • Give feedback, offer product suggestions, and ask tough transducer questions Traditional “Toneburst” Fishfinder • Traditional fishfinders operate at discrete frequencies such as 50kHz and 200kHz. • This limits depth range, range resolution, and ultimately, what targets can be detected in the water column. Fish Imaging at Different Frequencies Koden CVS-FX1 at 4 Different Frequencies Range Resolution Comparison Toneburst with separated targets Toneburst w/out separated targets CHIRP without separated targets Traditional “Toneburst” Fishfinder • Traditional sounders operate at discrete frequencies such as 50kHz and 200kHz. • This limits resolution, range and ultimately, what targets can be detected in the water column. • Tone burst transmit pulse may be high power but very short duration. This limits the total energy that is transmitted into the water column CHIRP A major technical advance in Fishing What is CHIRP? • CHIRP has been used by the military, geologists and oceanographers since the 1950’s • Marine radar systems have utilized CHIRP technology for many years • This is the first time that CHIRP technology has been available to the recreational, sport fishing and light commercial industries….. and at an affordable price CHIRP Starts with the Transducer • AIRMAR CHIRP-ready transducers are the enabling technology for manufacturers designing CHIRP sounders • Only sounders using AIRMAR CHIRP-ready transducers can operate as a true CHIRP system CHIRP is a technique that involves three principle steps 1. Use broadband transducer (Airmar) 2. Transmit CHIRP pulse into water 3.
    [Show full text]
  • Programming Chirp Parameters in TI Radar Devices (Rev. A)
    Application Report SWRA553A–May 2017–Revised February 2020 Programming Chirp Parameters in TI Radar Devices Vivek Dham ABSTRACT This application report provides information on how to select the right chirp parameters in a fast FMCW Radar device based on the end application and use case, and program them optimally on TI’s radar devices. Contents 1 Introduction ................................................................................................................... 2 2 Impact of Chirp Configuration on System Parameters.................................................................. 2 3 Chirp Configurations for Common Applications.......................................................................... 7 4 Configurable Chirp RAM and Chirp Profiles.............................................................................. 7 5 Chirp Timing Parameters ................................................................................................... 8 6 Advanced Chirp Configurations .......................................................................................... 11 7 Basic Chirp Configuration Programming Sequence ................................................................... 12 8 References .................................................................................................................. 14 List of Figures 1 Typical FMCW Chirp ........................................................................................................ 2 2 Typical Frame Structure ...................................................................................................
    [Show full text]
  • The Digital Wide Band Chirp Pulse Generator and Processor for Pi-Sar2
    THE DIGITAL WIDE BAND CHIRP PULSE GENERATOR AND PROCESSOR FOR PI-SAR2 Takashi Fujimura*, Shingo Matsuo**, Isamu Oihara***, Hideharu Totsuka**** and Tsunekazu Kimura***** NEC Corporation (NEC), Guidance and Electro-Optics Division Address : Nisshin-cho 1-10, Fuchu, Tokyo, 183-8501 Japan Phone : +81-(0)42-333-1148 / FAX : +81-(0)42-333-1887 E-mail: * [email protected], ** [email protected], *** [email protected], **** [email protected], ***** [email protected] BRIEF CONCLUSION This paper shows the digital wide band chirp pulse generator and processor for Pi-SAR2, and the history of its development at NEC. This generator and processor can generate the 150, 300 or 500MHz bandwidth chirp pulse and process the same bandwidth video signal. The offset video method is applied for this component in order to achieve small phase error, instead of I/Q video method for the conventional SAR system. Pi-SAR2 realized 0.3m resolution with the 500 MHz bandwidth by this component. ABSTRACT NEC had developed the first Japanese airborne SAR, NEC-SAR for R&D in 1992 [1]. Its resolution was 5 m and this SAR generates 50 MHz bandwidth chirp pulse by the digital chirp generator. Based on this technology, we had developed many airborne SARs. For example, Pi-SAR (X-band) for CRL (now NICT) can observe the 1.5m resolution SAR image with the 100 MHz bandwidth [2][3]. And its chirp pulse generator and processor adopted I/Q video method and the sampling rate was 123.45MHz at each I/Q video channel of the processor.
    [Show full text]
  • Analysis of Chirped Oscillators Under Injection Signals
    Analysis of Chirped Oscillators Under Injection Signals Franco Ramírez, Sergio Sancho, Mabel Pontón, Almudena Suárez Dept. of Communications Engineering, University of Cantabria, Santander, Spain Abstract—An in-depth investigation of the response of chirped reach a locked state during the chirp-signal period. The possi- oscillators under injection signals is presented. The study con- ble system application as a receiver of frequency-modulated firms the oscillator capability to detect the input-signal frequen- signals with carriers within the chirped-oscillator frequency cies, demonstrated in former works. To overcome previous anal- ysis limitations, a new formulation is presented, which is able to band is investigated, which may, for instance, have interest in accurately predict the system dynamics in both locked and un- sensor networks. locked conditions. It describes the chirped oscillator in the enve- lope domain, where two time scales are used, one associated with the oscillator control voltage and the other associated with the II. FORMULATION OF THE INJECTED CHIRPED OSCILLATOR beat frequency. Under sufficient input amplitude, a dynamic Consider the oscillator in Fig. 1, which exhibits the free- synchronization interval is generated about the input-signal frequency. In this interval, the circuit operates at the input fre- running oscillation frequency and amplitude at the quency, with a phase shift that varies slowly at the rate of the control voltage . A sawtooth waveform will be intro- control voltage. The formulation demonstrates the possibility of duced at the the control node and one or more input signals detecting the input-signal frequency from the dynamics of the will be injected, modeled with their equivalent currents ,, beat frequency, which increases the system sensitivity.
    [Show full text]
  • Femtosecond Optical Pulse Shaping and Processing
    Prog. Quant. Elecrr. 1995, Vol. 19, pp. 161-237 Copyright 0 1995.Elsevier Science Ltd Pergamon 0079-6727(94)00013-1 Printed in Great Britain. All rights reserved. 007%6727/95 $29.00 FEMTOSECOND OPTICAL PULSE SHAPING AND PROCESSING A. M. WEINER School of Electrical Engineering, Purdue University, West Lafayette, IN 47907, U.S.A CONTENTS 1. Introduction 162 2. Fourier Svnthesis of Ultrafast Outical Waveforms 163 2.1. Pulse shaping by linear filtering 163 2.2. Picosecond pulse shaping 165 2.3. Fourier synthesis of femtosecond optical waveforms 169 2.3.1. Fixed masks fabricated using microlithography 171 2.3.2. Spatial light modulators (SLMs) for programmable pulse shaping 173 2.3.2.1. Pulse shaping using liquid crystal modulator arrays 173 2.3.2.2. Pulse shaping using acousto-optic deflectors 179 2.3.3. Movable and deformable mirrors for special purpose pulse shaping 180 2.3.4. Holographic masks 182 2.3.5. Amplification of spectrally dispersed broadband laser pulses 183 2.4. Theoretical considerations 183 2.5. Pulse shaping by phase-only filtering 186 2.6. An alternate Fourier synthesis pulse shaping technique 188 3. Additional Pulse Shaping Methods 189 3.1. Additional passive pulse shaping techniques 189 3. I. 1. Pulse shaping using delay lines and interferometers 189 3.1.2. Pulse shaping using volume holography 190 3.1.3. Pulse shaping using integrated acousto-optic tunable filters 193 3.1.4. Atomic and molecular pulse shaping 194 3.2. Active Pulse Shaping Techniques 194 3.2.1. Non-linear optical gating 194 3.2.2.
    [Show full text]
  • Improved Spectrograms Using the Discrete Fractional Fourier Transform
    IMPROVED SPECTROGRAMS USING THE DISCRETE FRACTIONAL FOURIER TRANSFORM Oktay Agcaoglu, Balu Santhanam, and Majeed Hayat Department of Electrical and Computer Engineering University of New Mexico, Albuquerque, New Mexico 87131 oktay, [email protected], [email protected] ABSTRACT in this plane, while the FrFT can generate signal representations at The conventional spectrogram is a commonly employed, time- any angle of rotation in the plane [4]. The eigenfunctions of the FrFT frequency tool for stationary and sinusoidal signal analysis. How- are Hermite-Gauss functions, which result in a kernel composed of ever, it is unsuitable for general non-stationary signal analysis [1]. chirps. When The FrFT is applied on a chirp signal, an impulse in In recent work [2], a slanted spectrogram that is based on the the chirp rate-frequency plane is produced [5]. The coordinates of discrete Fractional Fourier transform was proposed for multicompo- this impulse gives us the center frequency and the chirp rate of the nent chirp analysis, when the components are harmonically related. signal. In this paper, we extend the slanted spectrogram framework to Discrete versions of the Fractional Fourier transform (DFrFT) non-harmonic chirp components using both piece-wise linear and have been developed by several researchers and the general form of polynomial fitted methods. Simulation results on synthetic chirps, the transform is given by [3]: SAR-related chirps, and natural signals such as the bat echolocation 2α 2α H Xα = W π x = VΛ π V x (1) and bird song signals, indicate that these generalized slanted spectro- grams provide sharper features when the chirps are not harmonically where W is a DFT matrix, V is a matrix of DFT eigenvectors and related.
    [Show full text]
  • Advanced Chirp Transform Spectrometer with Novel Digital Pulse Compression Method for Spectrum Detection
    applied sciences Article Advanced Chirp Transform Spectrometer with Novel Digital Pulse Compression Method for Spectrum Detection Quan Zhao *, Ling Tong * and Bo Gao School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China; [email protected] * Correspondence: [email protected] (Q.Z.); [email protected] (L.T.); Tel.: +86-18384242904 (Q.Z.) Abstract: Based on chirp transform and pulse compression technology, chirp transform spectrometers (CTSs) can be used to perform high-resolution and real-time spectrum measurements. Nowadays, they are widely applied for weather and astronomical observations. The surface acoustic wave (SAW) filter is a key device for pulse compression. The system performance is significantly affected by the dispersion characteristics match and the large insertion loss of the SAW filters. In this paper, a linear phase sampling and accumulating (LPSA) algorithm was developed to replace the matched filter for fast pulse compression. By selecting and accumulating the sampling points satisfying a specific periodic phase distribution, the intermediate frequency (IF) chirp signal carrying the information of the input signal could be detected and compressed. Spectrum measurements across the entire operational bandwidth could be performed by shifting the fixed sampling points in the time domain. A two-stage frequency resolution subdivision method was also developed for the fast pulse compression of the sparse spectrum, which was shown to significantly improve the calculation Citation: Zhao, Q.; Tong, L.; Gao, B. speed. The simulation and experiment results demonstrate that the LPSA method can realize fast Advanced Chirp Transform pulse compression with adequate high amplitude accuracy and frequency resolution.
    [Show full text]
  • A Fully Electronic System for the Time Magnification of Ultra-Wideband
    IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 55, NO. 2, FEBRUARY 2007 327 A Fully Electronic System for the Time Magnification of Ultra-Wideband Signals Joshua D. Schwartz, Student Member, IEEE, José Azaña, Member, IEEE, and David V. Plant, Senior Member, IEEE Abstract—We present the first experimental demonstration of Recent demonstrations of time-stretching systems intended a fully electronic system for the temporal magnification of signals for the aforementioned microwave applications have almost ex- in the ultra-wideband regime. The system employs a broadband clusively invoked the optical domain [1]–[5]. This presents a analog multiplier and uses chirped electromagnetic-bandgap structures in microstrip technology to provide the required signal problem for microwave systems from an integration standpoint, dispersion. The demonstrated system achieves a time-magnifica- as signal conversion to and from the optical domain necessi- tion factor of five in operation on a 0.6-ns time-windowed input tates the cumbersome element of electrooptic modulation, and signal with up to 8-GHz bandwidth. We discuss the advantages the referenced works require costly mode-locked or supercon- and limitations of this technique in comparison to recent demon- tinuum laser sources. strations involving optical components. The decision to perform time-stretching operations in the Index Terms—Analog multipliers, frequency conversion, mi- optical domain was motivated in part by a perceived lack of crostrip filters, signal detection, signal processing. a sufficiently broadband low-loss dispersive element in the electrical domain such as that which is readily available in optical fiber [2]. In our recent study [6], we proposed a fully I.
    [Show full text]
  • On the Lora Modulation for Iot: Waveform Properties and Spectral Analysis Marco Chiani, Fellow, IEEE, and Ahmed Elzanaty, Member, IEEE
    ACCEPTED FOR PUBLICATION IN IEEE INTERNET OF THINGS JOURNAL 1 On the LoRa Modulation for IoT: Waveform Properties and Spectral Analysis Marco Chiani, Fellow, IEEE, and Ahmed Elzanaty, Member, IEEE Abstract—An important modulation technique for Internet of [17]–[19]. On the other hand, the spectral characteristics of Things (IoT) is the one proposed by the LoRa allianceTM. In this LoRa have not been addressed in the literature. paper we analyze the M-ary LoRa modulation in the time and In this paper we provide a complete characterization of the frequency domains. First, we provide the signal description in the time domain, and show that LoRa is a memoryless continuous LoRa modulated signal. In particular, we start by developing phase modulation. The cross-correlation between the transmitted a mathematical model for the modulated signal in the time waveforms is determined, proving that LoRa can be considered domain. The waveforms of this M-ary modulation technique approximately an orthogonal modulation only for large M. Then, are not orthogonal, and the loss in performance with respect to we investigate the spectral characteristics of the signal modulated an orthogonal modulation is quantified by studying their cross- by random data, obtaining a closed-form expression of the spectrum in terms of Fresnel functions. Quite surprisingly, we correlation. The characterization in the frequency domain found that LoRa has both continuous and discrete spectra, with is given in terms of the power spectrum, where both the the discrete spectrum containing exactly a fraction 1/M of the continuous and discrete parts are derived. The found analytical total signal power.
    [Show full text]
  • Parameter Estimation of Linear and Quadratic Chirps by Employing the Fractional Fourier Transform and a Generalized Time Frequency Transform
    Sadhan¯ a¯ Vol. 40, Part 4, June 2015, pp. 1049–1075. c Indian Academy of Sciences Parameter estimation of linear and quadratic chirps by employing the fractional fourier transform and a generalized time frequency transform 1 2, 3 SHISHIR B SAHAY , T MEGHASYAM ∗, RAHUL K ROY , GAURAV POONIWALA2, SASANK CHILAMKURTHY2 and VIKRAM GADRE2 1Military Institute of Technology, Girinagar, Pune 411 025, India 2Indian Institute of Technology Bombay, Mumbai 400 076, India 3INS Tunir, Mumbai 400 704, India e-mail: [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected] MS received 10 April 2014; revised 8 January 2015; accepted 23 January 2015 Abstract. This paper is targeted towards a general readership in signal processing. It intends to provide a brief tutorial exposure to the Fractional Fourier Transform, followed by a report on experiments performed by the authors on a Generalized Time Frequency Transform (GTFT) proposed by them in an earlier paper. The paper also discusses the extension of the uncertainty principle to the GTFT. This paper discusses some analytical results of the GTFT. We identify the eigenfunctions and eigenvalues of the GTFT. The time shift property of the GTFT is discussed. The paper describes methods for estimation of parameters of individual chirp signals on receipt of a noisy mixture of chirps. A priori knowledge of the nature of chirp signals in the mixture – linear or quadratic is required, as the two proposed methods fall in the category of model-dependent methods for chirp parameter estimation. Keywords. Mixture of chirp signals; time–frequency plane; instantaneous fre- quency (IF); model-dependent methods for chirp parameter estimation; Fractional Fourier Transform (FrFT); Generalized Time-Frequency Transform (GTFT); Uncer- tainty principle; Eigenfunction.
    [Show full text]
  • Radar Measurement Fundamentals
    Radar Measurement Fundamentals Radar Measurement Fundamentals Primer Table of Contents Chapter I. Introduction . .1 Chapter III. Pulse Measurements Methods . .10 Overview . .10 Radar Measurement Tasks Through the life Automated RF Pulse Measurements . .12 cycle of a radar system . .1 Short Frame Measurements — The Pulse Model . .12 Challenges of Radar Design & Verification . .1 Sampling the RF . .12 Challenges of Production Testing . .2 Choosing Measurement Parameters . .12 Signal Monitoring . .2 Measurement Filter Type . .13 Basic RF Pulsed Radar Signals . .2 Detection Threshold and Minimum OFF Time . .13 Compressed Pulse signal types and purposes . .3 Maximum Number of Pulses to Measure . .14 Linear FM Chirps . .3 Frequency Estimation Method . .14 Frequency Hopping . .3 Measurement Point Definitions . .14 Phase Modulation . .4 Droop Compensation and Rise/Fall Definitions . .15 Digital Modulation . .4 50% Level Definitions . .15 Radar Pulse Creation . .4 Finding the Pulse . .15 Transmitter Tests . .4 Minimum Pulse Width for Detection . .15 Receiver Tests . .4 Using the Threshold Setting . .16 Chapter II. Pulse Generation – Baseband and Finding the Pulse Carrier Amplitude . .17 RF Modulated Pulses . .5 Method One: Magnitude Histogram . .18 Method Two: Local Statistics . .20 Overview . .5 Method Three: Moving Average . .20 Baseband Pulse Generation . .5 Noise Histogram (preparation for method four) . .21 Pulse Modulated RF . .6 Method Four: Least Squares Carrier Fit . .21 RF Pulses Directly from an Arbitrary Waveform Generator . .6 Locating the Pulse Cardinal Points . .23 Synthesizing Signals Directly in the AWG Series Interpolation . .24 with RFXpress¤ . .7 Estimating the Carrier Frequency . .24 The Carrier Parameters . .7 Constant Phase . .24 Adding Impairments . .7 Changing Phase . .25 Adding Interference . .7 Linear Chirp .
    [Show full text]
  • CHIRP Technology
    CHIRP Technology Airmar Technology NMEA 2013 San Diego Seminar Agenda • Overview of CHIRP technology compared to traditional fishfinder technology – What’s different? • Advantages vs disadvantages of CHIRP technology • Give feedback, offer product suggestions, and ask tough transducer questions Traditional “Toneburst” Fishfinder • Traditional sounders operate at discrete frequencies such as 50kHz and 200kHz. • This limits range resolution, and ultimately, what targets can be detected in the water column. Fish Imaging at Different Frequencies Resolution Comparison Traditional “Toneburst” Fishfinder • Traditional sounders operate at discrete frequencies such as 50kHz and 200kHz. • This limits resolution, range and ultimately, what targets can be detected in the water column. • Tone burst transmit pulse may be high power but very short duration. This limits the total energy that is transmitted into the water column. CHIRP A major technological advance in Sounder Technology CHIRP is a technique that involves three principle steps 1. Use broadband transducer (Airmar) 2. Transmit CHIRP pulse into water 3. Processing of return echoes by method of pattern matching (pulse compression) CHIRP Starts with the Transducer • AIRMAR CHIRP-ready transducers are the enabling technology for manufacturers designing CHIRP sounders • Only sounders using AIRMAR CHIRP-ready transducers can operate as a true CHIRP system DFF1-UHD GSD-26 CP450C BSM-2 It’s all about BANDWIDTH! 1. Use of a broadband transducer (Airmar) What is bandwith? Why is it important? 50 & 200 kHz 42-65 kHz 130-210 kHz 80 kHz 1 kHz Sound Amplitude per Drive Volt per Drive Amplitude Sound Frequency (kHz) CHIRP is a technique that involves three principle steps 1. Use broadband transducer (Airmar) 2.
    [Show full text]