First Person View (FPV) System

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Overview

The First Person View (FPV) system is used to transmit real-time video wirelessly from the UAV to a ground station. The video feed can be used to pilot the aircraft and/or to aid in aerial filming. Since most FPV systems transmit low-definition video and the signal is often lost and regained sporadically, UAVs often carry a separate non-FPV HD camera to record high quality video. A number of different antenna styles and frequencies are used for transmitting the video signal, and each has its own advantages and disadvantages. An on-screen display (OSD) system can also be added to superimpose real-time flight data onto the video feed such as airspeed, heading, altitude and other parameters.

Types

FPV systems are categorized based on the frequency they operate in. A number of different frequencies are popularly used in FPV, and they are divided into four frequency bands: 900 Mhz, 1.3 GHz, 2.4 GHz, and 5.8 GHz . A number of aspects must be considered when selecting an appropriate FPV frequency: interference, penetration, quality and legality. Firstly, no two wireless systems must be operating on the same frequency at the same time or there will be interference. For example, if the UAV's control system is 2.4 GHz, the FPV system should not use that same frequency. Also, two UAVs cannot use FPV systems on the same frequency at the same time. Penetration refers to how well can a video signal transmit through obstacles like trees or other objects. Lower frequencies will penetrate easily through obstacles, while high frequencies will lose signal when there is an obstacle between the UAV's antenna and the ground station's antenna. Also, lower frequencies transmit farther than high frequencies for the same transmitter power. Higher frequencies also provide better signal quality. Finally, since countries have laws regulating the use of radio frequencies, the legality of the frequency must be considered. The user should research which frequencies are allowed in his specific country. Some countries might require having an amateur radio license for operating FPV systems.

Components

FPV Camera

The fpv camera captures the image and send it to the transmitter. Small and lightweight 'security cameras' are often used for this task. A good FPV camera should be able to capture a good image even if it is being pointed directly at the sun, and should have good low-light image quality. The field of view of the lens is also an important factor. Some users prefer wide angle lenses while other prefer narrower fields of view.

Video Transmitter

An FPV video transmitter (VTX) is a device that generates a wireless video signal and transmits it to the ground using an antenna. Although some video transmitters are able to switch between a few working frequencies, most operate at a single specific frequency. The most important characteristic of a video transmitter besides its frequency is its power. Higher powered transmitters produce more powerful signals that can travel further, but consume more power and are usually heavier. Most video transmitters can also transmit sound, although this feature is often not used in FPV flight.

Video Receiver

An FPV video receiver (VRX) is a device that is used to receive a wireless video signal using a specialized antenna, and transmit that signal to a viewing device like a monitor or fpv goggle.

Antenna

FPV antennas are connected to the video transmitter and receiver to generate and capture the wireless radio signal. Proper antenna selection is critical to the performance of an FPV systems, and has a large impact on the range and quality of the video signal. A number of different antennas styles are used in FPV systems including the cloverleaf, patch, helical, crosshair and others. Some are designed for the receiver, and others for the transmitter. They can be categorized according to the signal polarization they provide. Polarization refers to the way the signal is propagated in 3D space, which has an important effect on how well the signal is transmitted to the ground station. Popular polarizations include linear and circular. Receiver and transmitter antennas should use the same polarization type.

FPV Monitor

The FPV monitor is simply a small screen used to view the live video feed from the ground. They are usually small so they can be powered by a battery and used in remote places. Some FPV monitors have integrated video receivers, and digital video recorders. Since an FPV signal is commonly lost and regained sporadically, a monitor used for FPV should not change configuration or turn off when it detects the signal has been lost.

FPV Goggles

An FPV goggle is a type of head-mounted display commonly used for FPV flight. They are able to provide a more immersive flight experience. Head movement trackers can be added to rotate the UAV's camera based on the direction the user is looking. Also, some FPV goggles have integrated video receivers. FPV goggles are more expensive than FPV monitors.

On-Screen Display

An On-Screen Display (OSD) system is a small chip mounted on the UAV that is able to display real-time flight information and super-impose it on the video signal to provide a heads-up display for the pilot. The flight information can include an artificial horizon, altitude, velocity, distance to the pilot, heading, and others. Some OSD systems have the necessary sensors to measure this information, and others are designed to get this information from the UAV's flight controller (if it has one).


Setup

An FPV system can be divided into the ground station, and the on-board FPV system. The various ways of connecting FPV components for each of these systems are outlined below.


Ground Station FPV System


Goggle-Integrated Receiver Setup

Schematic for FPV ground station with goggle-integrated receiver

The simplest way to set up a ground station is to use FPV goggles that come with an integrated video receiver. Just set up the system as described in the product's instructions. FPV monitors with integrated receivers are also available. Make sure that the integrated receiver is of the desired frequency, and that a proper antenna is being used.


External Receiver Setup

Schematic for FPV ground station with dedicated external receiver

Many people prefer to use a separate video receiver instead of an integrated one. This makes the ground station more modular and flexible. For this setup, buy a video receiver of the desired frequency, and an appropiate FPV antenna set (avoid the 'whip' or linearly polarized antennas that usually come with video receivers and transmitters). Connect the video signal (yellow cable) from the receiver to one or more FPV display devices such as FPV goggles or monitors. Then use a battery to power all three components by connecting the red and black cables in parallel to all components. This will likely require you to solder your own custom cables. Make sure the voltage of the battery matches the required voltage for all components. Ground station FPV components usually work at 12 volts, so a 3-cell lithium polymer battery is sometimes used, but other voltages might require other batteries. Try to find components that operate on the same voltage. If this is not the case, you can use a voltage regulator can be used to adjust the voltage supplied to a component.


On-Board FPV System


Dedicated Battery Setup

Schematic for on-board FPV system using dedicated battery

The on-board FPV system can be powered by a dedicated FPV battery, or by the same battery that powers the UAV's electric motors. If a dedicated battery will be used, make sure its voltage range matches the voltage requirements of the camera and receiver. Select the battery capacity based on the current draw of the components to provide the desired operating time (a 2 mAh battery can provide 2 mA for one hour). Connect the red and black cables from the battery to the camera and receiver. You might need to solder your own cables to do this. Then connect the camera's video signal cable (yellow cable) to the receiver. Some video transmitters can also transmit sound. If the camera captures sound, connect the sound cable (often times white) to the receiver. If the camera does not capture sound, simply do not connect the receiver's sound cable to anything.


Main Battery Setup

Schematic for on-board FPV system using the UAV's main battery to power the FPV system

To save weight, you might want to power the FPV system using the same battery used to power the motors. Since the motors can draw a lot of power from the battery and can induce variations in its voltage, this setup will require the use of a 'power filter' to stabilize the power supplied to the FPV system. If the FPV components work at a different voltage than the battery, you will also need a voltage regulator to adjust the voltage appropriately.


External Resources