High Qaulity Radio Mic design - Braodcast quality

Hi,

I am trying to design a true diversity radio mic receiver with roughly this spec.

power = 3volts

RF UHF 550mhz - 700mhz ( minimum 606.5mhz - 613.5mhz 10 channels )
Bandwidth 200khz per channel

Dual receiver & antenna

WBFM demodulator IC mono ?
audio output at 300mv ( THD less than 0.1% )
Compander ( expander ) 4:1 ? possibly THAT 4316

Low power Pic micro-controller with small LCD display for;
Frequency selection 25khz steps
Compander settings maybe
Monitor RSSI level from each receiver and switch modulator to receiver with higher signal

The PIC would need to be able to read rssi and change frequencies of the PLL

Would a hard switch of the RF from receiver to receiver create a click in demodulated audio?
should I fast pan from one RF receiver to another an back etc to the demodulator IC?
Is there such a think as a soft switch? I read somewhere in a patent that sure where using diode switches to make a soft switch?

My question is does anyone know of a good low power RF IC with integrated PLL rssi etc that can work in these frequencies ?

Many I have found so far such as TI cc1101 or adf1720-1 all transmit FSK etc.. but I'm looking to use the receiver for wbfm !

Also, any good choices for a WBFM demodulator IC mono ?

any ideas would be greatly appreciated!

thanks, ben

Out of curiosity, which national/regional/international regulations are considered in your band choice? Analog FM seems to me as a legacy technology regarding recent wireless microphone standards. 608 MHz to 614 MHz is said to be reserved for radio astronomy (See ETSI TR 102 546). The subband is also excluded for wireless microphone usage according to FCC.

WBFM (FM) is used by most if not all the high end radio mics used in tv production / stages. Some claim to be partly digital ( lectrosonic, sony etc ) but then at the most complex they would compress the audio to data rate below 200kbps with DSP codec ( bandwidth is limited to 200mhz per channel in licensing ) and in a purely digital system you would need to use use GFSK FSK ASK etc over Wide Band FM.
compression codecs in FPGA maybe? but then you have the power issue . how long are your 2x 1.5 aa batteries going to last? you can rule out OFDM not really workable or possibly not allowed. When you say FM is legacy do you mean its better to use 2.4/5ghz ? 2.4ghz is unreliable, leaking microwave ovens / overcrowded spectrum especially at large live events! also reconnect time in a dropout situation can be long!

I have thought about using linux / fpga / arm cpu boards so you can push udp over ip networks but your into the realm of using too much power. A high end radio mic can transmit audio for over 8 hours. I haven't completely ruled this idea out but have not yet found a board that is low power enough and powerful enough to compress with AAC codec or equiv. and run an RF link.

Also think about latency/ delay.. digital compression takes cpu time.. anything above 10ms point to point is considered slow in the lip sync world of tv production.

frequencies are all over the place around the globe. Its a complete mess!! but on the whole the higher 700 - 900 is being used by mobile phones although there's a few mhz in there
for license free somewhere..

in FM uhf mic systems the audio is compressed / expanded to fit into the 200mhz. Its analogue compression instead of digital. i am not sure if that makes it worse quality. there can be compander noises.

i have looked for IC's capable of realtime audio compression.. there is VS1005 ic encoding ogg vorbis/ mp3 ( too slow )

so anyway I am looking for a PLL FM demodulator IC that can work in UHF.. any ideas ?


anyway here is a few frequencies and they are limited to 10mw, 50mw or about 100mw depending where you are on the planet..

606 - 614Mhz uk = ( called TV channel 38 there ) licensed JFMG

606-608MHz plus 614-630MHz in the USA.

470-550MHz (TV Channels 21-30)
and 630-790MHz (TV Channels 41-60) require a unique license UK

here is some other frequencies used around the world in various places. blocks are by lectrosonic

Block 470 470.100 to 495.600 MHz
Block 19 486.400 to 511.900 MHz
Block 20 512.000 to 537.500 MHz
Block 21 537.600 to 563.100 MHz
Block 22 563.200 to 588.700 MHz
Block 23 588.800 to 614.300 MHz

Lastly I am also working on an SDR multichannel receiver but again battery power and latency will be the problem at the moment. GUradio blocks work party in FPGA that may in the future help with latency
but isn't solving power.

Is there a better way ? QPSK ? BPSK ?