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UHF duplexers have different types and configurations according to product specifications and buyer preferences. They include the following types:
Bandpass duplexers
A bandpass duplexer is a device that contains two filters, each for the transmitting and receiving frequency ranges. The transmission filter only allows the transmitting frequency, while the reception filter only allows the receiving frequency. Bandpass duplexers are mainly used in mobile and satellite communication systems.
Forced symmetrical duplexers
Forced symmetrical UHF radio duplexers use a symmetrical filtering configuration to eliminate the co-channel interference that occurs when two signals share the same frequency band. They force the signal to a particular frequency outside its desired passband. They are mainly used in applications that require a high level of interference rejection.
Pole-angled duplexers
Angle pole duplexers use filters with angled poles to achieve the desired frequency separation. One or more filter poles are angled to create a sharper cutoff for the unwanted frequencies. This helps narrow the bandwidth of the desired signal. They are mainly used in applications that require high selectivity and bandwidth.
Asymmetrical duplexers
Asymmetrical duplexers have one bandpass filter with a narrower bandwidth and higher frequency than the other filter. An asymmetrical duplexer is ideal for communication systems operating on different frequency ranges.
Hybrid duplexers
Hybrid duplexers combine the features of both the resonator and cavity duplexers. They are very compact in size and offer a wide range of frequency bands. They are usually found in mobile phones and other handheld devices. Due to their compact size, they are often incorporated into hybrid circuits.
Impedance
The UHF diplexer works best at the standard 50-ohm impedance. This is for matching RF circuits to ensure maximum power transfer without reflections. The duplexer's impedance must be compatible with the transmitter and receiver.
Power handling capacity
This is the maximum amount of RF power the duplexer can handle without damage or performance degradation. For most UHF duplexers, power handling capacity ranges from 10 watts for low-power applications to more than 100 watts for high-power installations. Examples of high-power UHF duplexers are those found in broadcast and commercial radio stations.
Frequency range
UHF duplexers are designed for multiple frequency bands within the UHF range of 300 MHz to 3 GHz. In most cases, frequency duplexers often cover 100 MHz to 1 GHz or even higher. But UHF satellite duplexers are specially designed for lower frequency bands, around 1-2 GHz.
Insertion loss
This is the loss of signal strength that occurs when transmitting a signal through the duplexer. UHF duplexers have an average insertion loss of 1-3 dB. The broadcast equipment usually has less than 1 dB.
Rejection
This refers to the duplexer's ability to attenuate unwanted signals. It is measured in dB. UHF duplexers are between 40 and 60 dB. But high-performance duplexers can reach up to 90 dB.
Temperature stability
The filters in the duplexer should maintain stable performance over a wide range of temperatures. Most UHF duplexers used in outdoor applications work well in temperatures of about -40 degrees Celsius to 55 degrees Celsius.
Maintaining the UHF duplexer ensures it meets the required standards and performs its functions well. Here are some of the maintenance tips for UHF duplexer basics:
Regular inspection
Users should regularly check the duplexer for signs of physical damage. People should look for things like corrosion, bent connectors, or damaged casings. The filters should also be inspected for wear from constant use. Any damage or wear will result in a decline in performance.
Proper cooling
The duplexers should be housed in a space with proper ventilation to prevent overheating. If the duplexers overheat, they will be unable to regulate their temperatures. This causes damage to internal components. This is especially for high-power duplexers that are often in heavy work.
Monitor seal integrity
For duplexers used in outdoor or harsh environments, their environmental seals should be monitored to ensure they are intact. This is to prevent dust, moisture, and other contaminants from entering the system.
Regular testing
Routine testing of the UHF duplexers should be done to verify their performance. This is measured in things like insertion loss, frequency response, and power handling. Using RF test equipment to compare the measured values with the manufacturer specifications. If there's any performance degradation, then replacement or repair is needed.
Keep the system grounded
Proper grounding of the duplexer ensures safety during electrical surges or lightning strikes. It also helps minimize the risk of RF interference. The grounding system should be checked regularly to ensure it has no signs of corrosion.
Keep their RF cables clean
The RF cables connected to the duplexers should be regularly checked for wear or damage. Avoid using coaxial cables that have kinks or water damage. Clean the connectors before connecting them to avoid dust or other contaminants.
Mobile communication systems
In mobile communication, the UHF duplexers are used in towers to enable the same frequency channel to be used for simultaneous transmission and reception. This allows mobile phones to make calls or use data and stay connected to cell towers. UHF duplexers for mobile communication are designed to handle low to medium power levels. They feature compact designs, high insertion, and frequency range. All these features make them suitable for small installations.
Sattelite communication systems
UHD duplexers are used for satellite communication to separate the uplink and downlink signals. They allow communication satellites to receive signals from the ground, process them, and beam them back to different targets. The UHF duplexers used in this application are designed to handle wider frequency ranges. They also feature high power handling capacity and low insertion loss.
Broadcasting systems
Broadcasting stations use VHF UHF duplexers to separate the transmission of audio or video content and monitor signals. The VHF and UHF duplexers help minimize interference and ensure the receiver and transmitter operate on different but close frequency ranges. Broadcasting duplexers are not selective like satellite or mobile duplexers. They are designed to handle very high power levels, often exceeding 100 watts.
Two-way radio communication systems
Two-way radios used by police, firefighters, and other first responders rely on UHF duplexers for communication. The duplexers allow them to receive and transmit signals on the same frequency. This enables operations like voice communication and data transmission to be carried out seamlessly. The fh UHF duplexers are usually compact and portable. They also feature high power handling and robust designs to withstand harsh environments.
Remotely operated vehicle systems
The UHF duplexers enable command and telemetry data to be transferred between the ground control station and the vehicle. This makes them suitable for applications such as military drones or robotic exploration. The duplexers used in this application are designed to withstand extreme environmental conditions.
Power handling capacity
The power handling capacity of a duplexer determines the level of RF power it can handle without performance degradation. For applications like broadcast or industrial two-way radios that require high power, then the duplexer should have a higher power rating. For low-power applications like mobile communications, a lower power rating is sufficient.
Insertion loss
UHF duplexers with low insertion loss should be considered to ensure maximum signal strength is transferred from the antenna to the receiver. High insertion loss results in weak signals, causing poor performance. Insertion loss is especially critical in satellite or wireless system applications, where distance and signal strength are vital.
Frequency range
UHF duplexers should be selected based on how well they can accommodate the specific operating frequency range of the communication system being used. The frequency range can vary widely depending on the application, from 300 MHz for television broadcasting to 3 GHz for satellite communication. The duplexer selected must match the frequency range of the transmitter and receiver.
Environmental conditions
The duplexer used for outdoor or harsh environment applications like marine or military should have robust environmental sealing. The UHF duplexer should be durable enough to prevent water, dust, and other contaminants from entering the unit.
Filter selectivity and rejection
Selectivity is the duplexer's ability to distinguish between the desired and unwanted signals. This is also known co-channel interference. High filter selectivity ensures good signal quality by minimizing interference from adjacent channels. Rejection should be high enough to attenuate unwanted signals.
UHF duplexers are used for satellite communications, wireless internet, and television broadcasts. They work by separating transmission and reception paths for the antennas used in these systems. A duplexer consists of filters that allow the antenna to send and receive signals simultaneously on different frequencies or within slightly overlapping frequency ranges.
Duplexers are used to separate transmission and reception signals simultaneously on UHF frequencies, while diplexers are used for the transmission or reception of a single signal. Diplexers work by splitting or combining signals with different frequencies or within distinct frequency ranges. They act as frequency splitters or combiners, whereas duplexers are more complex devices designed specifically for two-way communication.
The user begins by analyzing the existing system design to locate the most accessible area for installation. They ensure the antenna cable is disconnected from the antenna before connecting the duplexer. The duplexer is then mounted securely, usually at the antenna mast or near the antenna base.
In this process, the duplexer input is connected to the antenna, and the outputs are connected to the RF cables leading to the transmitter and receiver. After securing all connections, the user performs a system check to ensure proper signal routing.
One common mistake is failing to secure the duplexer properly. This allows environmental elements like dust and moisture to enter and degrade performance. Neglecting to use proper coaxial connectors will cause there to be increased insertion loss. Poor cable management leads to electrical interference.
UHF devices should be replaced when there are visible signs of physical damage, like corrosion or bent connectors. They can also be replaced when there is continuous high insertion loss that cannot be corrected by repairs. If the duplexers fail to maintain the required frequency accuracy or filtering capability, there will be poor performance.
Frequent temperature fluctuations cause thermal stress on components. If there are extreme variations in temperatures, the duplexer can be damaged by either overheating or extreme cold. The environmental seals are checked. If they are worn or damaged, they should be replaced. Failure to replace them will allow dust and moisture to enter the unit.
