1. GSC: Standardization Advancing Global Communications
SOURCE:
GRSC Working Party 1
TITLE:
Resolution GSC-10/08 Radio Microphone and Cordless Audio Standardization
AGENDA ITEM:
GRSC 5.5
CONTACT:
Brian Copsey
GRSC(06)_27
Resolution GSC-10/08 Radio Microphone and Cordless Audio Standardization
Progress report
GSC: Standardization Advancing Global Communications

2. GSC: Standardization Advancing Global Communications
Resolution GSc-10/8
Considering:
that various countries and regions have established differing standards and test methods for these devices.
Resolves:
to facilitate a strong and effective global radio standards collaboration on Radio Microphones and cordless Audio standardization in a technology neutral environment;
that given the World wide appeal and use of band 2 micro transmitters, : That GRSC Working Party 1 should examine existing standards and limits and prepare a draft documents for GRSC#11;
that given the ITU limits are different in the three regions,: The GRSC Working Party1 should examine the cost benefits of using the most stringent limits for the GRSC standards;
that GRSC Working Party 1 should examine the “EMC” method of testing and report back to GRSC#11;
that GRSC Working Party 1 should seek members views and comments on band sharing with other services now that the broadcast bands have become congested with simulcasting of analogue and digital transmissions.
GSC: Standardization Advancing Global Communications

3. Resolves 2: Band II Micro Transmitters
Following both practical tests and Compatibility studies a power of 50nW appears to strike the right balance between the quality of reception experienced by the user and the prevention of interference to other broadcast reception.
GSC: Standardization Advancing Global Communications

4. Band II Micro Transmitters
Measurements on a range of devices from a number of countries suggest that this power is also a mean average of those tested.
ETSI TS has been modified to incorporate these devices and await approval by WP1 and GRSC
GSC: Standardization Advancing Global Communications

5. Resolves 3: Spurious Limits
Consideration has been given to the cost /benefit of the most stringent spurious limits, for all Radio Microphone and the ETSI TS will reflect the most stringent, leaving NSO’s to insert any changes required by national legislation
GSC: Standardization Advancing Global Communications

6. Resolves 4:EMC method of Testing
Considerable work has been undertaken to validate this method of testing low power devices, Band II micro transmitters are the first to have used the method in the ETSI standard EN (which is now out for public enquiry ) and this has been reflected in the ETSI TS
Copies of EN available in WP1 docbox
GSC: Standardization Advancing Global Communications

7. GSC: Standardization Advancing Global Communications
EMC method
For low power devices:
Maximum erp/eirp is converted to dBmicroVolts/metre at a distance of three metres
The new value is given as a relaxation of the EMC limit at the frequency of operation
The transmitter mask (modulated) is adapted to the new EMC mask
Spurious emissions from the transmitter shall meet the EMC limit
GSC: Standardization Advancing Global Communications

8. GSC: Standardization Advancing Global Communications
EMC example: Tx mask
GSC: Standardization Advancing Global Communications

9. GSC: Standardization Advancing Global Communications
EMC example
Transmitter mask 0 – 90dBc
EMC limit at 4 nW erp:
+40 3 metres
Relaxed EMC limit for 50 nanoWatts erp
metres
GSC: Standardization Advancing Global Communications

10. Resolves 5: Bandsharing
Information from the UK Cave Review has been placed in the WP1 docbox:
Conclusion of review “sharing is the default position”
Following slides show the DVB-T “problem”
Work continues in identifying potential spectrum for sharing
GSC: Standardization Advancing Global Communications

11. GSC: Standardization Advancing Global Communications
DVB-T introduction
UHF TV frequencies today
TV transmitters
Radio microphones
Today:
Analogue TV only
Transition:
Analog. + DVB-T
UHF TV frequencies by 2010
Target:
Full DVB scenario
New
Services
GSC: Standardization Advancing Global Communications

12. GSC: Standardization Advancing Global Communications
UHF spectrum sharing
Today we share frequencies...
Radio microphones and TV share the UHF frequencies
Exclusive frequency ranges for radio microphones do not exist world wide and in Europe.
The main goal of regulation is to save frequency resources with DVB-T!
The distribution of TV signal concept has changed from roof antenna to in door receiving equipment. As result the radio microphone receiver interferences will be increased.
TV will give up UHF frequencies by 2010 to new services!
That reduces the available frequencies for radio microphones tomorrow we will struggle
GSC: Standardization Advancing Global Communications

13. GSC: Standardization Advancing Global Communications
Basic interference principle for radio microphones
Interference to radio microphones generated by DVB-T Transmitter:
A DVB signal in same channel like radio microphone (e.g. Transmitter on wide distance).
DVB adjacent channel noise (Unwanted transmitter side band or wideband noise).
Interference generated by radio microphone components:
Receiver desensitising by multi channel microphones system to them self.
Unwanted signals generated by Intermodulation.
Additional receiver noise (e.g. blocking).
Intermodulation on microphone transmitter output.
GSC: Standardization Advancing Global Communications

14. GSC: Standardization Advancing Global Communications
The effect of external interference produced by DVB-T noise
DVB-T transmitters, which use same channel as radio microphones, affect the reception of radio microphones only with a part of their spectrum (IF BW).
Outside of the DVB-T channel the transmitter emissions decrease rapidly.
Out of band DVB-T emissions can only be filtered at the DTV transmitter!
All Interferences reduce the range of the wireless microphones substantially.
GSC: Standardization Advancing Global Communications

15. GSC: Standardization Advancing Global Communications
The unwanted emissions between two DVB-T transmitters
Between two DVB-T transmitters the noise floor is much higher.
Here is the wireless microphone quality of reception substantially reduced.
GSC: Standardization Advancing Global Communications

16. DVB-T is a multi carrier signal
DVB-T signal interferes with radio microphone receiver with about 7000 carriers
GSC: Standardization Advancing Global Communications

17. GSC: Standardization Advancing Global Communications
Typically protection distance caused by noise & Intermodulation
In which frequency spacing can a microphone be used again?
---- Left DVB-T edge ETSI DVB-T spectrum Mask st applicable microphone channel
Radio microphones need to be separated by 800 kHz from the edge of the DVB-T mask!
GSC: Standardization Advancing Global Communications

18. GSC: Standardization Advancing Global Communications
Wireless microphones RF performance made by hardware
Important components in the microphone receiver
A high signal quality reduce adjacent channel disturbance
This units are fundamentally for the RX sensitivity and the receiver interference immunity
Oscillator
UHF filter
Pre Amp
UHF filter
Mixer
IF-Filter
Band pass filters define the receiver frequency range and reduce out of band disturbances
Filter for the used signal and adjacent channel disturbance
The quality of each and every component in this chain define the audio quality and performance of a wireless microphone system
GSC: Standardization Advancing Global Communications

19. GSC: Standardization Advancing Global Communications
Simplified test arrangement for interference examination
Test procedure:
An artificial microphone signal is fed into the free field and thus the effects of the DVB-T transmitter with different frequencies is observed.
The quality limit for a radio microphone receiver is the S/N of at least 80dB(a). The FM generator level will be tuned to 80dB(a) on receiver.
GSC: Standardization Advancing Global Communications

20. GSC: Standardization Advancing Global Communications
Examples of measurement results
Interference to wireless microphones by DVB-T transmitters
Two TV channels are occupied by DVB-T. Each color shows another test receiver.
Shown is the receiver input signal for 80dB(a) measures by spectrum analyzer:
GSC: Standardization Advancing Global Communications

21. Required frequency resource @ multi channel operation
(MHz)
( Ch )
Every receiver gets the same input level / Intermodulation product distance = 100kHz
GSC: Standardization Advancing Global Communications

22. Sharing Spectrum in the UHF band: That’s a practical situation
UHF frequency allocation by TV at Athens in May 2006:
The situation: Almost all UHF channels are used by TV stations
The Job: Installation and operation of multi channel radio microphones and IEM
GSC: Standardization Advancing Global Communications

23. GSC: Standardization Advancing Global Communications
Conclusion
DVB-T is coming and continues to grow.
Spectrum is getting rare day by day.
Clever spectrum management is the way forward in the DVB-T environment.
For the microphone manufacturers substantial investments are necessary to fulfill the rising customer requirements and allow sharing spectrum between DVB-T transmitters. New frequency resources are required.
Don’t forget the multiplicity of the applications called “Radio Microphone”
Consider the immense length of the creation of value added chain begun with wireless microphones to the home TV, MP3 player, Sport event and much more.
GSC: Standardization Advancing Global Communications

24. GSC: Standardization Advancing Global Communications
Future:
Resolves 1:to facilitate a strong and effective global radio standards collaboration on Radio Microphones and cordless Audio standardization in a technology neutral environment
Continue work on the issues of digital equipment and appropriate test methods
Continue work on bandsharing
GSC: Standardization Advancing Global Communications