SOURCE GRSC Working Party 1 TITLE Resolution GSC1008

SOURCE: GRSC Working Party 1 TITLE: Resolution GSC-10/08 Radio Microphone and Cordless Audio Standardization AGENDA ITEM: GRSC 5. 5 CONTACT: Brian Copsey bc@copsey-comms. com GRSC(06)_27 Resolution GSC-10/08 Radio Microphone and Cordless Audio Standardization Progress report

Resolution GSc-10/8 Considering: • that various countries and regions have established differing standards and test methods for these devices. Resolves: 1. to facilitate a strong and effective global radio standards collaboration on Radio Microphones and cordless Audio standardization in a technology neutral environment; 2. 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; 3. that given the ITU limits are different in the three regions, : The GRSC Working Party 1 should examine the cost benefits of using the most stringent limits for the GRSC standards; 4. that GRSC Working Party 1 should examine the “EMC” method of testing and report back to GRSC#11; 5. 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.

Resolves 2: Band II Micro Transmitters • Following both practical tests and Compatibility studies a power of 50 n. W appears to strike the right balance between the quality of reception experienced by the user and the prevention of interference to other broadcast reception.

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 102 192 has been modified to incorporate these devices and await approval by WP 1 and GRSC

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 102 192 will reflect the most stringent, leaving NSO’s to insert any changes required by national legislation

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 301 -357(which is now out for public enquiry ) and this has been reflected in the ETSI TS 102 192. • Copies of EN 301 -357 available in WP 1 docbox

EMC method • For low power devices: – Maximum erp/eirp is converted to d. Bmicro. Volts/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

EMC example: Tx mask

EMC example • Transmitter mask 0 – 90 d. Bc • EMC limit at 4 n. W erp: – +40 d. Bmicro. Volts/metre @ 3 metres • Relaxed EMC limit for 50 nano. Watts erp – +52. 2 d. Bmicrovolts/metre @ 3 metres

Resolves 5: Bandsharing • Information from the UK Cave Review has been placed in the WP 1 docbox: • Conclusion of review “sharing is the default position” • Following slides show the DVB-T “problem” • Work continues in identifying potential spectrum for sharing

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

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

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.

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.

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.

DVB-T is a multi carrier signal DVB-T signal interferes with radio microphone receiver with about 7000 carriers

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 ---- 1 st applicable microphone channel Radio microphones need to be separated by 800 k. Hz from the edge of the DVB-T mask!

Wireless microphones RF performance made by hardware Important components in the microphone receiver This units are fundamentally for the RX sensitivity and the receiver interference immunity UHF filter Pre Amp UHF filter Band pass filters define the receiver frequency range and reduce out of band disturbances A high signal quality reduce adjacent channel disturbance Oscillator Mixer IF-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

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 80 d. B(a). The FM generator level will be tuned to 80 d. B(a) on receiver.

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

Required frequency resource @ multi channel operation (MHz) ( Ch ) Every receiver gets the same input level / Intermodulation product distance = 100 k. Hz

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

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, MP 3 player, Sport event and much more.

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