Programs used in a test vehicle to measure digital radio (DAB) and television (DVB) signal coverage. The measurement is performed during car run.
- electromagnetic field intensity,
- bit error rate indicators of the received data stream,
- geographic coordinates and time + date of measurement.
These values are measured dynamically while the test vehicle is moving. The role of our company, the system integrator, was to develop software that would meet these requirements and that would use existing hardware (instruments, computer, communication devices, etc.). Moreover, the preparation of the program was complicated by the fact that it is used in a measuring car used for routine measurements already. This implies that the programs developed must not in any way affect existing measurements carried out by the vehicle. It means set the measuring instruments into an “unusual” state is not allowed as well requirement to switch the cabling is not possible. Another consequence of using the car for routine measurements was that the vast majority of debugging was performed on weekends when the car was not in use.
The picture shows an example of measurement output (measured value is terminal voltage of FM radio at standard autoantena output, red: 30dBµV <= U <50dBµV; blue: 50dBµV <= U <70dBuV; green: U> = 70dBµV):
An ESVN receiver is connected to the computer via GP-IB bus to measure electromagnetic field strength in the DAB signal band. Measured bandwidth is narrower than the transmitted bandwidth, so the measured values are recalculated. The current position of the car is obtained from the GPS receiver via the serial interface. The DAB measuring receiver is also connected to the control computer via the RS232 serial interface and provides bit error rate data of the received data stream. OFDM analyzer and demodulator are used to measure DVB-T digital television signal. When measuring with OFDM analyzer, the ESVN receiver is not used because its function is already included in the analyzer.
Measuring program permanently records all listed data. At the cost of some deceleration, it even allows simultaneous measurements at two frequencies. The data is recorded in a suitable format to allow post-processing by specialized programs that plot the measured data into maps.
The measured frequency is entered either by the frequency value or by selecting the channel (TV) or block (DAB) or by the network name (the program maintains a database of detected network names).
Program allows custom setting of measuring instruments according to immediate needs. The program includes a series of windows called “Additional Settings”. With these windows it is possible to make further adjustments of the instruments before measurement. The program remembers this setting and repeats it before any further measurement.
Due to the use of the calibrated receiving antenna for DAB and DVB, the program also allows you to enter all parameters needed to convert the output voltage to the corresponding level of electromagnetic field intensity.
Example of input window:
More information request here.