BASIC PRODUCT DETAILS
An RF and Microwave detector is a passive two-terminal device used in an RF circuit to detect the RF power in the transmission medium. It is also called RF power detectors, which are generally available in module or device package
- RF Power Detectors are available as RMS Detectors, Peak or Envelope Detectors and Successive Detection Log Video Amplifiers (SDLVAs), etc.
- In general, RF detectors are available in the detection ranges up to 100 dB.
RF power detectors are mainly used in Transmit/Receive chain for Power Measurement, RF Pulse Detection for Protection, Return Loss Measurement in the test laboratories. It is also used in systems like Radar and other Electronic Warfare systems for precise RF Power detection and Measurement application.
RF detectors are available as an active coaxial component, which is used to convert RF signal strength which they receive at the input port to proportional DC voltage signal at its output terminal.
On this page about RF and Microwave detectors, you will learn more about the following.
- What is an RF detector?
- Types of RF detectors?
- Applications of RF and Microwave detectors?
- What are the specifications that need to consider in the selection of an RF detector?
- RF and Microwave detector Manufacture.
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Design and Application
RF detectordesign concept?
An RF detector samples the received signal and generates dc output voltage directly proportional to the RF power at that point. It is used to measure the RF power in wired or wireless systems.
In the microwave and millimeter-wave technology waveguide or coaxial transmission, line detectors are used for power or SWR measurement. These detectors are typically incorporate surface barrier Schottky diodes for power detection.
RF detector as an Envelope detector:
The simplest form of RF detector is the diode detector, which is designed using a diodeconnected between the output and input of the circuit, with acapacitor and resistorin parallel from the output of the circuit to the ground. This capacitor is used to charge whenever the diode is in positive bias.
When the peak signal reaches the input of the diode it becomes active and passes the received signal to the capacitor and the capacitor gets charged until the input voltage of the diode dropdown. Once the capacitor is charged, it will hold the charge until the next peak signal is reached the input of the diode. if a new peak signal comes, the capacitor will charge to its peak.
The output of the detector is taken across the parallel resistor to the capacitor. The resistor and capacitor need to chose correctly, in such a way that the output of this circuit will be equal to the identical voltage peak of the original signal.
RF and Microwave Detectors types:
In general RF detectors are of two main types - logarithmic and RMS. In addition, RF detectors can be classified into three basic types.
Log detectors.
RF Log detectors are used to convert a wide dynamic range signal into a logarithmic output.
Zero bias Schottky diode detectors.
RF Zero Bias detectors are used for low-power and passive applications, and they don’t require a bias current or voltage for their operation.
Bias Schottky diode detectors:
RF Threshold detectors convert a specific frequency range RF signal to a DC equivalent voltage.
- The logarithmic RF detector converts the RF power received into a DC voltage which is proportional to the log of the value. In the RMS detector convert the received signal into DC output proportional to the RMS value of the received signal.
RF and microwave detectors are available with RF connectors like SMA, N, and BNC… with 50 or 75 Ohm varieties. RF detectors are available with a negative or positive output bias.
The other two categorizations of RF detectors are peak and RMS- Root Mean Square detectors.
- Peak RF detectors provide information about peak power.
- RMS RF detectors provide information on received average power.
Peak detectors:
Peak RF detectors are also called envelope detectors. It is used to capture the extreme voltage signal strength at its input. The peak detector circuit tracks the peak of the input voltage until it reaches the extreme point and holds that peak value until the next peak comes in. Ideally, the peak detector performs regardless of the input signal speed but is limited to the capability by the bandwidth of the input signal.
Peak RF detectors are of 2 types.
- Positive peak detector: It captures the most positive point in the input signal
- Negative peak detector: It captures the most negative point in the input signal.
A peak RF detector uses a diode, amplifier, and capacitor to capture and hold the signal peak of the input RF signal. The capacitor in the detector charges through the amplifier and the diode in the detector prevents its discharge of it. This is used to detect the peak signal in an RF circuit.
RMS detectors:
RMS detector is also called square law detectors, thermal detectors or power detectors, etc.
- RMS detectors use the characteristics of semiconductors diodes or transistors to convert a voltage input signal into a proportional RF power. RMS detector is particularly very useful for low-cost and high-frequency applications.
Eg: Thermal detectors like thermistors or thermocouples are used to convert the electrical power in RF signal into thermal energy by using a resistive component and then temperature variation is measured with respect to the ambient temperature.
Advantages :
- Very wide bandwidth.
- Good accuracy.
RF detectors are also classified on the base of the package.
- Inline coaxial assemblies RF detector
- Waveguide RF detectors.
Waveguide RF Detectors, are RF detectors built into a waveguide assemble and inline RF detectors are of co-axial packages and can be used in series with other coaxial assemble lines.
Applicationsof Bias Tee:
RF detectors areused to measure the signal strength and control RF power flow in RF wired and wireless systems.
- In receivers, an RF detector is used to identify and convert the amplitude-modulated RF and microwave signals to baseband (or video) signals in either wired or wireless systems.
- In transmitters, RF and microwave detectors are used to measure the transmitter output power of the communication systems and generate the feedback signal to the control circuit to avoid the excess flow of RF power over a certain maximum transmitter power level, allowed in a region.
Radio Detector:
Inradio, an RF detector help to extract informationfrom amodulatedRF signal as correspondingcurrent or voltage. A variety of different types of detector devices, such as theelectrolytic detector, coherer,magnetic detector, andcrystal detector, were used in the old wireless telegraphy era.
Today world RF detector is used to extract the audio signalfrom the RF and microwavecarrier wave usually consisting of transistors,semiconductor diodes, orintegrated circuits.
Envelope detector:
The simplest envelope detectoris the diode detector connected between the input and output with aresistorandcapacitorin parallel. This detector will hold the input peak signal in the capacitor.
Product detector:
Aproduct detector isused forSSB or AM signals detection in radios. In the product detector, the original carrier RF signal is multiplied with the local signal and removed from the carrier frequency, and covert to the baseband signal. The product detector generates the resultant signal of the local signal and modulated signal like an RF and microwave mixer.
Slopdetectors:
Slop detectors are basically used for the FMandPMsignals. Slope detectors have inferior noise rejection and distortion compared to dedicated FM detectors that are normally used in Radio communication systems.
Phase detector:
A phase detector is anonlinearRF device, whose output corresponds to the phase difference between the two input signals. For the phase detector, it needs a reference signal on one input and the phase-modulated signal is applied to the other input port. The output signal of the phase detector is proportional to the phase difference between the two inputs.
Quadrature detector:
In quadrature detectors, the input FM signal is split into two signals. Then one signal passed through a high-reactance capacitor, to shift the phase of that signal by 90 degrees. The two-phase varied signals are then multiplied together in a phase detector, the output is proportional to the phase difference between the two signals.
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Basics & Selection Feature
Main selection specifications for RF detectors.
When selecting an RF detector needs to select the suitable type of detector with a matching RF connector type for their installation. RF detectors are available with different coupling mechanisms in a wide frequency range.
Frequency:
RF detector is usually optimized for a particular operating frequency. It is important to select an RF detector that covers the lower and higher frequency band of operation.
FrequencyResponse:
The frequency response of the RF detector indicates the variation of the detector output with respect to the variation in the frequency band. If the variation is less in the range of less than 0.5 dB for the entire band, it is a better detector.
Low-Level Sensitivity:
The low-level sensitivity of the RF detector indicates the lowest power it can detect, 0.5 mV/mW is an ideal figure for the normal detector over the entire band of operation.
Power Handling:
Power handling of the RF detector is the maximum signal input power it can handle before breaking down. Need to select as per the system requirement. Need to select an RF detector with power handling higher than the maximum expected power flow through it.
Maximum VSWR & Insertions loss:
VSWR indicates the internal reflection of the detector. If the VSWR is lower, for the entire band it is a better RF detector.
Insertion Loss is the measure of loss in the RF Signal power when it passes through the Detector. Need to select an RF detector with lower insertion loss, In an ideal detector, this would be zero.
Impedance:
The characteristic Impedance of the detector should be matched to the impedance of the system in which it is used. A perfect match of 50 ohms and 75 ohms will help to reduce the internal return loss.
RF connectors and Dimensions:
RF connectors of the detectors need to select as per the application where it is going to use. RF detectors are available with many connector options like SMA, N, BNC, 2.92, etc are available from different manufacturers.
The physical size of the RF detector is another prime factor that needs to consider in the selection process.
Conclusion:
RF detector is an RF component used to detect the peak signal in the RF transmission chain. It is available with different package types and dimensions.
Below is the list of top-rated RF and Microwave detectors manufacturers listed with the RF and Microwave Community. If you would like to add any new manufacturer or any specific detector to the list, feel free to recommend us through the submit article button on the top of the RFMWC website.
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