One Radio To Rule Them All

Since the dawn of wireless, the military has fantasized about one radio that can do everything. In January of this year Wired magazine called this their "doomed quest."  The goal was to create a single radio device that can replace the numerous types of radios they use daily. In October of 2011 the U.S. Army terminated their  Joint Tactical Radio System (JTRS). The idea was to develop a software-programmable and hardware-configurable radio. Some of the spec flat out write that "The JTRS radio is to be a telephone, computer and router in one box." That sounds like a big box to me. Ultimately even reducing the requirements wasn't enough to control costs. One billion dollars later it was cancelled. So here is why it failed, and will continue to fail. More here.

• The Unified Antenna

 The problem is that this goal works against the laws of physics. One of the more obvious goals is to have one unified antenna. Having multiple antennas on a single radio is about as ungainly as having multiple radios in the first place. But using one antenna for many dissimilar wavelengths is...well it's just dumb. Any ham will tell you that a tuned antenna is more efficient than just a random length of metal. When you design an antenna  to be effective within one wavelength, you do so to the loss of effectiveness in other wavelengths. JTRS was originally planned to use frequencies from 2 megahertz to 2 gigahertz. That's not a small piece of RF real estate. Here's a complete list :

1. Soldier Radio Waveform (SRW)
2. Single Channel Ground Air Radio System (SINCGARS) with Enhanced SINCGARS Improvement Program (ESIP), 30-88 MHz, FM, frequency hopping and single frequency
3. HAVE QUICK II military aircraft radio, 225-400 MHz, AM, frequency hopping
4. UHF SATCOM, 225-400 MHz, MIL-STD-188-181, -182, -183 and -184 protocols
5. Mobile User Objective System (MUOS): It is important to note that the JTRS HMS manpack is the only radio program of record that will deliver terminals supporting the next generation UHF TACSAT MUOS program. 85% of all MUOS terminals are expected to be ground radios, so if JTRS HMS fails, MUOS (funded in the billions) fails as well - unless a COTS solution is developed...of course MUOS has also had its share of problems, recently announcing yet another 6 month slip for launching its first satellite.
6. Enhanced Position Location Reporting System (EPLRS), 420-450 MHz spread spectrum
7. Wideband Networking Waveform (WNW) (under development)
8. Link-4A, -11B, - 16, -22/TADIL tactical data links, 960-1215 MHz+
9. VHF-AM civilian Air Traffic Control, 108-137 MHz, 25 (US) and 8.33 (European) kHz channels
10. High Frequency (HF) - Independent Side Band (ISB) with automatic link establishment (ALE), and HF Air Traffic Control (ATC), 1.5-30 MHz
11. VHF/UHF-FM Land Mobile Radio (LMR), low-band 25-54 MHz, mid-band 72-76 MHz, high-band 136-175 MHz, 220-band 216-225 MHz, UHF/T 380-512 MHz, 800-band 764-869 MHz, TV-band 686-960 MHz, includes P25 public safety and homeland defense standard
12. civilian marine VHF-FM radio, 156 MHz band
13. Second generation Anti-jam Tactical UHF Radio for NATO (SATURN), 225-400 MHz PSK Anti-jam
14. Identification Friend or Foe (IFF), includes Mark X & XII/A with Selective Identification Feature (SIF) and Air Traffic Control Radar Beacon System (ATCRBS), Airborne Collision Avoidance System (ACAS) and Traffic Alert & Collision Avoidance System (TCAS), and Automatic Dependent Surveillance – Addressable (ADS-A) and Broadcast (ADS-B) functionality, 1030 & 1090 MHz
15. Digital Wideband Transmission System (DWTS) Shipboard system for high capacity secure & nonsecure, line-of-sight (LOS), ship-to-ship, and ship-to-shore, 1350-1850 MHz
16. Soldier Radio & Wireless Local Area Network (WLAN), 1.755-1.850, 2.450-2.483.5 GHz, Army Land Warrior program 802.11
17. Cellular telephone & PCS, includes multiple US and overseas standards and NSA/NIST Type 1 through 4 COMSEC (SCIP)
18. Mobile Satellite Service (MSS), includes both VHF and UHF MSS bands and both fielded and emerging low Earth orbit and medium Earth orbit systems and standards, such as Iridium, Globalstar, et al. Includes capability for NSA/NIST Type 1 through 4 COMSEC, 1.61-2 [2.5] GHz. May allow use of geosynchronous satellites with special antenna.
19. Integrated Broadcast Service Module (IBS-M). Currently three legacies UHF military broadcasts (TIBS, TDDS, and TRIXS) which will be replaced in the future with a Common Interactive Broadcast (CIB).
20. BOWMAN, the UK Tri-Service HF, VHF and UHF tactical communications system.

Antenna efficiency measures the electrical losses that occur while it is operating at a given frequency, or averaged over its operation across a frequency band. This metric depends on three kinds of loss: coil losses, ground losses, and other losses. (Let's not get into 'other') The antenna's total resistance is the sum of these losses plus the radiation resistance , which is the effective resistance representing emitted RF power. Antenna efficiency is the ratio between its radiation resistance and its total resistance. This will always vary with the type of antenna, the dimensions of the antenna etc. !

• A Unified Amplifier

If you are using one amplifier, it has to operate across the whole spectrum of signals you may be tuning. But the fact is that wide-band amplifiers consume much more power than narrow band amplifiers. In this case efficiency simply describes the ratio of power in to power out. Then consider that virtually all power lost in an amplifier is converted directly into heat.You can only radiate so much of that out with a heat sink and a fan. Now try to imagine doing that in a desert. Houston we have a problem.

• Tuner Selectivity

No matter how you receive a signal, that signal must be rectified. In modern hardware we use an DPLL (Digital Phase Lock Loop) circuit, sometimes an ADPLL (All Digital Phase Lock Loop).  Undoubtedly JTRS was more vested in the even more ragged edge tech toy the SPLL (Software Phase Lock Loop.)  With these, in theory, tuning is implemented by software rather than specialized hardware.In reality it has to control hardware and it's usually just synchronizing a VFO (variable frequency oscillator) or VCO (voltage-controlled oscillator.) Spectral purity is more or less contrary to the goals of wide spectrum width, producing an inevitable loss of frequency stability, and phase noise.

But there is a solution. They should be looking at this from a manufacturing point of view. In supply chain management the answer was vertical integration. The problem here is resource management, so the answer is horizontal integration. Instead of trying a one-size-fits-all solution, merging all services, instead merge only similar services. Belligerent MBAs asking engineers to fight against the laws of physics will produce a radio the size of a refrigerator that does ten things poorly for half a million dollars each.  If you begin instead with the immutable laws of physics, start with signals that are decoded by software, who's signals can be rectified from the same or similar antennas or even modular antennas —you can reduce 20 radios to 10 or even 5.

Homodyne ≠ Synchrodyne

I thought I'd found a horrible incongruity in history. Here we have an early PLL tuner and one book claims D.G. Tucker invented it, another book claims Francis Morley Colebrook did. It's my worst-case research scenario, both sources are credible, and I have to tease out the truth. Strangely it was a datasheet in a Chinese parts catalog that first reconciled my problem.
Colebrook was writing papers in the 1920s about rectifying detection. This work was derivative of Karl Braun and Jadadis Bose and a paper by E.V. Appleton on the synchronization of oscillators. But he made progress in calculating radiation resistance. Like a good researcher he built on the existing information and made some progress. Colebrook made the original homodyne receiver in 1924. His design mixed the received signal with a locally generated sine wave at the same frequency as the carrier wave to extract the signal from the carrier in a simple detector. Wikipedia completely skips this in their entry. Krzysztof Iniewski book Wireless Technology affirms my assertion. (His English is poor, I correct it in the quote)

"The use of PLL-based frequency synthesis has it's roots in the evolution of coherent communication systems. ...In 1924, a team of British engineers led my F.M. Colebrook the Homodyne (later renamed Synchrodyne) method, which consisted of a local oscillator, a mixer and an audio amplifier."

The Homodyne suffered from the fact that reception was valid only when the oscillators phase and frequency were very close to the incoming signal. Any slight shift in phase would cause the frequency to drift which in turn would cause signal strength to deteriorate. This short coming is what spurred later research in Automatic Frequency Control (AFC.) In 1931 Henri de Bellescize applied to patent an improved homodyne tuning circuit with AFC. That was the first PLL. henri cannot have derived his work from Tucker as he predates it. But before Colebrook was Robinson.

In March 1922, F.N. H. Robinson applied for a patent on a tuning circuit in which the carrier of the incoming signal is filtered out in a path separate from the main signal path. That signal was amplified in a regenerative tuned amplifier before being recombined with the original input signal. The basic idea is to reinforce the carrier signal, in other words a homodyne... J. Evans points out plainly what this is and also that nobody noticed.

So if Colebrook invented the precursor to the PLL, and Henri derived the true PLL, what did D.G. Tucker do? there were a series of small modifications by different invetors.. some plainly redundant. Walton in 1930, Reimann 1932, Jarvis 1933, Urte 1934?, Starnecki 1934, Oltze 1938. These primarily improve selectivity. More here.

In 1932 D.G. Tucker with R.A. Seymour and J. Garlick were co-authoring academic papers on the Synchrodyne. They did not in one step invent the synchrodyne. A series of small improvements led it to them. There were no new engineering principles here. Zero. This page addresses the confusion. Regenerative tuning circuits were called homodynes. That's where the erroneous idea that one homodyne became the synchrodyne arose. The synchrodyne wasn't even a radio, it was designed for measurement!

First of all, the technical name for this device is the Zero-IF Receiver. The name refers to it's zero intermediate frequency (IF). In this circuit the oscillator phase, is the reference for the PLL frequency synthesizer. It's controlled by the DC output voltage of the quadrature detector. Received frequencies are detected directly, without the need for super-heterodyne conversion. It's elegant and much less noisy than the homodyne models that led to it.

Colebrook went on to work at The national Physical Laboratory Radio Division in the 1940s. There he worked on the "Pilot ACE" one of the UKs first computers. D.G. Tucker became a member of the Newcomen Society and wrote some very detailed academic texts on the history of electrical engineering.

PLL to ADLL

So after all that hubbub about crystal radio, I thought I'd explain what a modern solid state tuner is like. The PLL was invented in 1932, that's after Armstrong's superheterodyne. There is a huge difference in the tuners concepts. A superheterodyne is a tube driven tuner. It was the best of tube technology, but it's still a tube with a filament that eventually burns out. A PLL is a solid-state tuner: no tubes*, no crystals, no nada. It's just a linear circuit.

*While this version used vacuum tubes, it's latter implementation used semi-conductors. That's a diagram of his version to the upper right.

It was first conceived by Henri de Bellescize, (sometimes spelled Bellescise) in the French journal Onde Electrique. he described it in detail, but never implemented the design as far as we know. I have read that some British scientists fleshed out working models, but the first large-scale commercial applications weren't for another 20 years. In the 1940s they were used in AM radio synchronous demodulation. In the 1950s a PLL Circuit was used to recover the color data from the analog TV signal.

So what is it? A PLL is a circuit synchronizing an output signal with another one. In this case the output signal is generated by an oscillator. This is a reference" signal. When these two signals are synchronized [having a phase error of zero or of constant error] we describe them as "locked." If phase error changes, a control mechanism adjusts the frequency of the oscillator
so that error will again approach zero. A phase-locked loop is an example of a control system using negative feedback. it is so elegant yet complex that I can see why Bellescize conceived it but never built it.

There are 3 basic parts:
1. Voltage Controlled Oscillator
2. Phase Detector
3. Loop Filter

WARNING THIS REQUIRES MATH: The Voltage Controlled Oscillator (VCO) operates at an angular frequency. That just means it is the scalar measure of the rotation rate. I.E. this angular frequency sets the frequency with which phase changes. [magnitude of the vector quantity.] The Phase Detector (PD) compares the phase of the output signal with the phase of the reference signal. The out put of this function is a measure of the root error between their phases. The output of the PD has both AC and DC components. The Loop Filter then is applied to remove the undesired AC component. If error is not compensated for in this way, the VCO cannot operate at it's center frequency. The Loop Filter feeds back to the VCO to adjust it's operating frequency to eliminate phase error.Once the center frequency of the input signal is frequency modulated by an arbitrary low frequency signal the output signal of the loop Filter is the demodulated signal. And where did he get thsi crazy idea? He saw his own work as an improvement on the first homodyne receiver designed in 1924 by a British engineer named F.M. Colebrook... there is no end to this.

The first digital PLL appeared in 1969, from a company called Signetics. RCA debuted the CD4046, their own version 3 years later. It's phase detector was digital and all other components were analog. But that was the start. Quickly other components were replaced until we had a fully ADPLL (All Digital Phase Locked Loop. ) Today we're trying for the SPLL, A purely software device.