The Conducted Emissions performance of a transmitter is basically the ratio in dB of how far down any unwanted outputs are with respect to the wanted signal at the antenna connector.
As we have seen previously, unwanted frequencies can be present on the output of the transmitter for a number of reasons. Noise on DC Power supplies is one reason, but by far the most common and strongest unwanted products are the harmonics produced by the Transmitter itself. Harmonics are simply integer multiples of the wanted frequency, and are produced because the... Continue Reading
As discussed in our previous blog post, the Transient Adjacent Channel Power (TACP) is simply an extension of the ratio of the energy produced in the wanted and adjacent channels when the Transmitter is keyed up or down. In reality, the unwanted energy produced by the Transmitter doesn’t just spread into the adjacent channel, it also spreads out far beyond that point. Tx Noise, therefore, is a measure of the unwanted transmitted energy at some specified offset from the wanted frequency.
Eventually, as we go further and further away from the carrier, the... Continue Reading
Adjacent Channel Power (ACP) is basically the ratio of the energy produced in the wanted and adjacent channels when the Transmitter is in steady state mode. Transient Adjacent Channel Power (TACP) is simply an extension of this, being the ratio of the energy produced in the wanted and adjacent channels when the Transmitter is keyed up or down. Transient ACP is measured in the frequency domain. A related parameter “Transient Behaviour” is measured in the time domain.
When the transmitter is keyed up or down (in other words, the user... Continue Reading
Before explaining Adjacent channel power, it is necessary to make mention of Electrical Noise. This subject will be covered more deeply later, but for now understand simply that noise, as it relates to communications systems, is defined as an unwanted random fluctuation in an electrical signal.
As we have seen previously, the Tx signal is produced by a locked oscillator within the Synthesizer. However, the output produced by such oscillators is not totally “clean.” That is to say that it does not just contain energy at the wanted frequency (the... Continue Reading
The Frequency Stability of a Transmitter is a measure of how close the actual frequency transmitted is to the wanted.
Frequency Stability is directly determined by the Crystal Oscillator, as all frequencies produced in the Synthesizer are locked to this reference. Frequency Stability is generally quoted in Parts per Million (ppm) but can sometimes be quoted as a discrete number of Hertz (Hz). The difference between the wanted frequency and that actually produced is known as the Frequency Error or Frequency Drift.
To illustrate this, consider the diagram... Continue Reading
We’re at the end of a 3 part series on RF Performance with Ian Graham, Principal Engineer for the Systems Engineering group. In the first video, Ian defined the different specifications for RF Performance. In the second video, he discussed RF performance for Transmitters.
In this final video, Ian defines the specifications of receivers. Ian delves into the desired performance aspects, regulations, and system costs. Ian also talks about the benefits a customer will receive by choosing a system that supports better RF performance, and how to identify that performance in... Continue Reading
We’re in the middle of a 3 part series on RF Performance with Ian Graham, Principal Engineer for the Systems Engineering group. In the first video, Ian defined the different specifications for RF Performance, such as reliability vs cost, the minimum acceptable performance by the regulatory authorities, and how Tait exceeds these levels of performance.
Today we’ve got video two of the series, where Ian explains the key RF specifications for transmitters. In this video, Ian delves into adjacent channel power and how sideband noise can affect neighboring receivers,... Continue Reading
One of the great advantages of choosing Tait is our RF Performance. We pride ourselves in both transmitting and receiving technology, and this series will look at the technical data that demonstrates why.
We recently interviewed Ian Graham, Principal Engineer for the Systems Engineering group, about RF Performance. The results of the interview were three videos which will be shared here over the next few weeks. At the end of the series, you should be able to look at specification sheets for different products and determine for yourself which one has an RF performance... Continue Reading
The Transmitter Output Power is defined as the power produced in to a 50 Ohm load connected at the radio antenna port.
In transmit mode, the Synthesizer produces the desired Tx frequency with the FM modulation (speech or data) super-imposed. This part is called the Exciter. The transmitter then amplifies this signal up to the final power level to be transmitted, after which the signal passes through the Tx/Rx Switch before being filtered to remove any unwanted harmonics. Ideally then, all that is transmitted is the desired signal at the required... Continue Reading
Before we get into the detail of each RF performance parameter, this week, let us discuss the parts that make up a typical radio. This is absolutely crucial to understanding the parameters that affect RF performance.
Shown below is a very simplified block diagram of the RF part of a typical Tait FM Mobile or Portable radio. Two commonly used abbreviations are introduced here -Tx (ie: Transmitter), and Rx (ie: Receiver). These abbreviations will be used throughout the remainder of this series.
The heart of the RF section is the Synthesizer. Here,... Continue Reading