Waveform modulation is an important part of radar technology that determines how well a radar will communicate data. Without clear incoming data from radar, military personnel can be left defenseless in enemy territory. After reading this, you’ll know the basics of a modulated waveform, which will make it easier to pick the correct type of radar for your mission.
What Is a Modulated Waveform?
A modulated waveform is defined as the process of converting data into radio waves by adding information to an electronic or optical carrier signal. When data is being transferred, modulation encodes the information by changing the shape of a carrier wave.
Modulation involves changing parts of the waveform to include a signal, which contains data that will help end-users make sense of what the system is receiving.
When speaking about radars, waveform modulation is used to:
- Improve range resolution (how accurately you measure the range of a target)
- Increase target echo signal return
- Reduce the probability of intercept and/or detection by an enemy receiver
- High-resolution imaging
There are two methods for transmitting waveforms. The first is continuous wave (CW) where energy is continuously transmitted and received. The other is a pulse in which energy is transmitted for short durations of time continuously in pulses.
Types of Common Radar Modulations
The most common types of modulations are FM and AM (frequency and amplitude modulation). FM is typically used for continuous wave operation.
Frequency and Amplitude Modulation (FM/AM)
Frequency modulation (FM) is the modulation of the carrier wave frequency in agreement with a signal or speech.
Amplitude modulation (AM) is modulation of the amplitude of a radio carrier wave in accordance with the strength of the audio or other signal.
There are a few common examples of FM/AM modulation including Frequency-Modulated Continuous-Wave (FMCW) and Linear Frequency Modulation (LFM), both of which are used in RADA radars.
Frequency-Modulated Continuous-Wave (FMCW)
Frequency-Modulated Continuous-Wave (FMCW) is a type of radar system that measures both the distance and velocity of moving objects. This is achieved by continuously changing the frequency of the transmitted signal by a set signal at a specific rate over a fixed time period.
Radar devices without FMCW are at a disadvantage since they cannot determine the target range. This is because the radar device doesn’t have the necessary timing device to allow the system enough time to transmit and receive data, then convert it into an accurate measurement of range.
FMCW radars can be used in unmanned aircraft, like altimeters, and in transportation situations. Some features include reliability, non-contact distance measurements (especially in harsh conditions), and accuracy. These radar types can also be used for security sensors and human detection systems by looking like vital signs, and imaging.
Linear Frequency Modulation (LFM)
Linear Frequency Modulation (LFM), also known as chirp, is the most popular type of pulse compression and is used for many radar systems due to its easy hardware setup and range resolution.
Since there are increasing demands for mobile communications and remote sensing, the frequency resources that could be assigned to radar systems and that employ LFM waveform are in short supply. Increasing the time span of a transmitted pulse increases the pulse’s energy and improves its target detection capability. However, reducing the time span can improve the radar’s range resolution.
PSK/FSK Modulation(Phase/Frequency Shift Keying)
Phase shift keying (PSK) is the digital modulation technique where the phase of the carrier signal is changed by alternating the sine and cosine inputs at a certain time. There are only a finite number of phases. It is widely used for wireless LANs, and biometrics along with Bluetooth communication and RFID. It is also the most commonly used modulation in satellite communications.
Frequency shift keying (FSK) is the digital equivalent of frequency modulation. It also uses a finite number of frequencies. FSK modulation also refers to a type of frequency modulation that assigns bit values to separate frequency levels.
Barker Code was one of the first waveform modulations used in radar and is used in RADA radars today. It is a finite sequence of digital values with the ideal autocorrelation property and is used as a synchronizing pattern between sender and receiver.
How Modulation Technology Impacts Decision-Makers
When looking into which radar best fits a mission, there are several factors to consider. Once an objective is established, it can be easier to determine what product will work best for the operation.
One factor to consider is distance. Do you need a way to determine a short-range distance or do you need something with more long-range capabilities?
How a unit will use the modulation technology is another point to consider. Some can be used in unmanned aircraft but others need humans to operate them. Others are meant to search out human vital signs.
Another factor to consider is how easy it is to implement. For example, FMCW has a low-cost implementation and doesn’t require a pulsed operation. Conversely, LFM is more costly but has an increased resolution and capability performance.
However, a disadvantage to LFM technology is that some companies are discontinuing the use of LFM technology and developing new avenues. This new technology would allow for a sensor to do multiple actions in one and will be easier to hide from the enemy since they won’t see the “chirp.”
Barker Code (phase modulation) has an easier implementation process than LFM but the performance isn’t as competitive.
So looking at all of these factors, what seems to be a simple question becomes more complicated with research.
How RADA Uses Modulated Waveform
All types of modulated waveform can be used in radar technology depending on what the situation demands. While some instances need close-range detection, others are looking for more long-range security. In addition, some are designed to detect human vital signs rather than incoming projectiles.
Since each modulation has different ranges and capabilities, companies need to consider what their client’s needs are before deciding which one to use. In transmitted signals, modulation helps with encoding data and providing more detail on the waves sent out.
RADA, Inc. incorporates FMCW, LFM, and Barker Code into their radars to create the most advanced technology to help protect not only military personnel but civilians as well. Because the most important part of our mission is to keep everyone on your mission safe, so they can go home safely when the assignment is complete.
Looking for a provider of cutting-edge radar technology? Learn more about RADA USA’s suite of tactical radars designed to meet the highest SWaP-C industry standards.