In wireless systems, interference in the wireless channel always causes a lot of trouble for users, and it reduces the reception rate of the specified signal. Interference may come from intentional, unintentional or accidental radiators and occur in different frequency bands.
The use of wireless communications has increased 100-fold in the last 10 years, but the number of available license-free bands has not grown in tandem, meaning that anyone using a license-free band needs to share that spectrum with others in their area. As radio spectrum resources become increasingly scarce, manufacturers are insisting on improving spectrum utilization for maximum capacity and performance (sharing or reuse). As a result, there is necessarily limited radio interference in the work of wireless communication systems.
Δ Classification of interference signals
The frequency of the interference signal is the most common parameter to identify the source of interference, and usually the interference signal can be classified according to the frequency characteristics. There are many different types of interference in wireless communication systems, which are listed below.
（1）Same frequency interference: the frequency of the useless signal is the same as the frequency of the useful signal and causes interference to the receiver receiving the useful signal of the same channel, also known as co-channel interference.
（2）Adjacent channel interference: interference caused by the power of the adjacent channel of the interfering station (station) falling into the receiver channel, also known as adjacent channel interference.
（3）Out-of-band interference: interference caused by harmonic or spurious radiation from the transmitter in the pass-band of the received useful signal, also known as out-of-band interference.
（4）Inter-modulation interference: Inter-modulation interference is divided into transmitter inter-modulation interference and receiver inter-modulation interference.
● Transmitter inter-modulation interference refers to multiple transmitter signals falling into another transmitter, and in the final stage of the amplifier non-linear modulation of each other, resulting in unwanted combination of frequencies, interference caused to receivers with the same received signal frequency.
● Receiver inter-modulation interference refers to multiple strong signals into the receiver at the same time, in the receiver front-end nonlinear circuitry under the effect of inter-modulation frequencies, inter-modulation frequencies fall into the receiver IF band caused by interference.
（5）Blocking interference: radio equipment to receive weak useful signal, received on both sides of the frequency, high-frequency circuit band interference with strong interference signals, known as blocking interference. Blocking interference is light to reduce the reception sensitivity, or lead to communication interruptions.
The interference classification of a wireless system has a decisive impact on the response of the engineer. For example, out-of-band interference occurs when harmonics from a simple design or inadequately filtered transmitter enter a higher frequency band. Filtering out harmonics from transmitters ensures that wireless systems do not affect other systems operating in higher frequency bands.
Δ Interference Detection
However, as spectrum demand increases, so does wireless system interference. Therefore, in order for all wireless systems to work properly, interference identification and reduction is particularly important. In the worst case scenario, interference interrupts the communication of the entire wireless system, which motivates engineers to test radio interference effectively.
The interference classification of a wireless system has a decisive impact on the engineer’s response. For example, out-of-band interference occurs when harmonics from a simple design or inadequately filtered transmitter enter the higher frequency bands. Filtering out harmonics from transmitters ensures that wireless systems do not affect other systems operating in higher frequency bands.
In the process of wireless signal testing, the most likely cause of high noise is interference, and the source of interference is difficult to locate with the naked eye, especially in urban environments with dense building distribution, the use of multi-meters can not solve this problem.
Hongke log-periodic antennas are also commonly used for interference detection, with a standard 1/4 inch nut mounting interface on the bottom of the antenna, which can be flexibly assembled with various brackets, such as with handheld brackets; small size, light weight, and very portable, suitable for outdoor testing.
Frequency range: 650MHz-8GHz
Gain: 13.7dBi (maximum), 8.27dBi (average)
Calibration point: 108 (50MHz step)
VSWR: < 1:2.5
Standard impedance: 50 Ohm
Dimensions (L/W/D): 293x209x27mm