WO2008017844A2

WO2008017844A2 - Headset

Info

Publication number: WO2008017844A2
Application number: PCT/GB2007/003024
Authority: WO
Inventors: Lewis Davies; Paul Winter
Original assignee: The Technology Partnership Plc
Priority date: 2006-08-09
Filing date: 2007-08-09
Publication date: 2008-02-14
Also published as: WO2008017844A3; GB0615830D0; EP2055137A2

Abstract

A headset comprising at least one earphone; at least one antenna arranged to receive radio frequency signals; and low noise amplifier circuitry for amplifying the received radio frequency signals.

Description

HEADSET

Field of the Invention

The present invention relates to a headset and in particular, but not exclusively, to a headset arranged to receive radio frequency signals such as digital audio broadcasting (DAB) signals. The present invention also relates to a circuit for use in a headset.

Background

Mobile telephones, handsets or similar user equipment are known. In this document the term "user equipment" will be used, which is intended to include these devices as well as other items such as PDAs (personal digital assistant), portable computers or the like. Such user equipment is able provide wireless communications.

It is know to incorporate radios into user equipment. It is proposed allow DAB radio to be received with such user equipment. However there is a problem. DAB signals are weak because the network operator, who provides the infrastructure, has to operate at a minimum signal in order to minimize the number of towers dotted across the countryside. However, the electromagnetic interference from the handset (resulting from the wireless communication) tends to be at frequencies around the DAB frequencies.

DAB radios are known, which can be used with a headset or head phones.

Earlier DAB products (in DAB radios) used for the antenna: i) the bottom part of the headphone; or ii) off-the-shelf headsets with built-in resonant chokes.

However neither of these options would address the problem associated with electromagnetic interference. It is an aim of embodiments of the present invention to address or at least mitigate the problem described above.

According to one aspect of the present invention, there is provided a headset comprising: at least one earphone; at least one antenna arranged to receive radio frequency signals; and a first cable arranged to carry multiplexed signals, said multiplexed signals comprising said radio frequency signals and at least one other signal.

According to another aspect of the present invention, there is provided a headset comprising at least one earphone; at least one antenna arranged to receive radio frequency signals; and low noise amplifier circuitry for amplifying the received radio frequency signals.

According to yet another aspect of the present invention, there is provided a headset comprising: at least one earphone; at least one antenna arranged to receive radio frequency signals, said at least one antenna comprising a cable; low noise amplifier circuitry for amplifying the received radio frequency signals, said cable providing said antenna being coupled between one earphone and said low noise amplifier circuitry; and a connection cable coupled at one end to said low noise amplifier circuitry and at the other end being connectable to a device, wherein at least one of said connection cable and said cable providing said antenna is arranged to carry said radio frequency signals multiplexed with at least one other signal.

Brief Description of Drawings

For a better understanding of the present invention and as to how the same may be carried into effect, reference will now be made by way of example only to the accompanying drawings in which:

Figure 1 shows a headset embodying the present invention; Figure 2 shows a circuit incorporated in the headset of Figure 1;

Figure 3 shows the headset of Figure 1 when connected to user equipment.

Figure 4 shows a first method embodying the invention for adjusting the resonant length of the antenna; Figure 5 shows a second method embodying the invention for adjusting the resonant length of the antenna;

Figure 6 shows a dipole type antenna arrangement used in an alternative embodiment of the invention;

Figure 7 shows a loop type antenna arrangement used in an alternative embodiment of the invention;

Figure 8 shows an arrangement using two antennas and one LNA to cover different frequency bands, in an alternative embodiment of the invention;

Figure 9 shows an arrangement using two antennas and two LNAs to cover different frequency bands, in an alternative embodiment of the invention; and Figure 10 shows an arrangement for a spatial diversity system using two antennas and two LNAs, in an alternative embodiment of the invention.

Detailed description of preferred embodiments of the Invention

Reference is first made to Figure 1 which shows a headset 1 embodying the present invention. The headset 1 comprises a left earphone 2a and a right earphone 2b. In this embodiment, the earphones 2 are the type that are placed in the ear of the user but in alternative embodiments of the invention can take any other suitable form and may for example be of the type which are placed over the ear. The earphones thus comprise any suitable earpiece.

The left earphone 2a is connected via a cable 4 to a circuit 6. The circuit 6 is shown in more detail in Figure 2 and will be described later. The right earphone 2b is connected via a cable 8 to the circuit 6. The length of the left cable 4 is x and may for example be of the order of 200mm ± 20mm. The length of the left cable is selected for the convenience of the user. In contrast, the length of the right cable is y and may for example be of the order of 560mm ± 20mm. The length of the right cable 8 is selected such that the right cable is able to act as an antenna. The right cable can be made an appropriate dimension (length) to resonate in the DAB band III frequency band (174 to 239MHz) and therefore act as a good antenna whilst still being a comfortable size for the user to use. .As the field strength of the broadcast DAB signal tends to be greater further above the ground level,, it is desirable to place the receive antenna as high as possible. In normal operation the highest part of the user equipment is the earphone. It is therefore desirable to place the antenna between one of the headphones and the circuit 6.

Of course the antenna can be provided between the left headphone and the circuit in alternative embodiments of the invention.

It should be appreciated that the length of the cable acting as an antenna will be selected on the basis of the frequency range to be received. Embodiments of the invention can be used with any suitable DAB or non DAB frequency. In one embodiment of the invention, the length of the cable acting as the antenna is not adjustable and is selected to be of an appropriate length to receive the signals of intended frequency.

Reference is now made to Figure 4 which shows a modification to the arrangement shown in Figure 1. In particular, it can be seen that an inductor 80 is inserted into the cable 8, between the circuit 6 and the earphone 2b. This may be done where it is not possible to find an appropriate dimension (length) that allows the antenna to resonate in the chosen frequency, and be a comfortable size for the user. The inductor 80 or other suitable electrical tuning element or elements, can be inserted into the cable to adjust the apparent electrical length and therefore resonant frequency of the antenna whilst keeping the physical length of the antenna at a suitable length for the user. Figure 5 shows an alternative to the arrangement of Figure 4. In Figure 4, electrical components are used to extend the effective length of the antenna. Figure 5 shows electrical components used to reduce the effective length of the antenna. In the modification shown in Figure 5, part of the cable can be "choked off by inserting a parallel resonant circuit, or series of parallel resonant circuits, each comprising a capacitor 82 and inductor 81 in each wire in the cable. The resonant circuit is inserted in the cable 8, between the circuit 6 and the earphone 2b. Each resonant circuit should be resonant at the desired frequency to be received. This causes the portion 83 of the cable between the resonant circuits and low noise amplifier (circuit 6) to act as an antenna with electrical length A whilst the portion 84 of the cable between the resonant circuits and earphone is not part of the antenna.

Referring back to Figure 1 , the circuit 6 is connected via a main cable 10 to an audio plug 22. The main cable has a length z which may be of the order of 1000mm + 20mm. The length of the main cable is set to be of a length which is convenient for the user. The audio plug 22 allows the headset 2 to be plugged into user equipment. The audio plug 22 has a ground connection 12 and a power connection 14. Additionally there is an audio right input 20, an audio left input 18 and a microphone/RF (radio frequency output 16 from the circuit 6.

Thus in the arrangement of Figure 1 , the main 'active' element of the antenna for the DAB signals or the like is the right headphone cable y. This acts as a monopole, with the main headset cable ground along with the handset ground planes and shielding acting as a counterpoise to this active element.

By using the headphone cable as the active element advantages are achieved.

The user equipment electronics tends to radiate some electromagnetic interference (EMI) at DAB frequencies. Although shielding and other design methods are used to reduce this radiation, it cannot be eliminated completely. If this EMI is at the same frequency as the received DAB signal it reduces the signal to noise ratio of the DAB signal, effectively reducing the sensitivity of the receiver. By placing the antenna as far from the user equipment as possible, the effects of EMI are reduced. Additionally this arrangement is such that the antenna counterpoise, which theoretically should be an infinitely big, is as large as possible

Reference is now made to Figure 2 which shows the circuit 6 in more detail. The circuit has a first interface 30 which is arranged to be connected to the earphone 4 and 8. The first interface 30 comprises a first pin 34 which is arranged to provide an audio left output to the left cable 4 and a second pin 32 which is arranged to be connected to the audio left return of the left cable. The first interface 30 also has a third pin 35 which is arranged to provide an audio right output to the right cable and a fourth pin 36 arranged to receive an audio right return and 'active element¹ of antenna from the right cable. The cables 4 and 8 connected to these pins are formed from multi stranded enamelled copper wire.

The second input pin 32 is connected via a first inductor 40 to a volume control circuitry 44. The fourth input pin 36 is connected via a second inductor 42 to the volume control circuitry 44. The volume control circuitry is arranged to control the volume of the audio signal in the earphones 2a and 2b. The volume control circuitry is controlled by a volume control provided on the headset. Additional volume control may be provided by the user equipment to which the headset is connected.

A second interface 46 is provided which is connects the headset to user equipment via a coaxial cable. The second interface 46 has a first pin 48, which is arranged to provide a left audio signal to the left earphone, is connected via a third inductor 56 to the first pin 34 of the first interface 30. Similarly the second interface has a fourth pin 54 which is connected via a fourth inductor 58 to the third output pin 35 of the first interface. This provides the right audio signal for the right earphone.

A second output 50 of the second interface 46 provides a power input for a low noise amplifier circuit 64 which will be discussed in more detail later.

A third pin 52 is arranged to receive a combined signal from the output of a microphone circuit 62 and the output of the low noise amplifier circuit 64. The microphone circuit 62 is arranged to permit a call to be answered from the headset and the voice of the user to be picked up so a telephone conversation can be conducted. This third pin 52 is connected to the core of the coaxial cable extending between the headset and the user equipment. A fifth inductor 60 is arranged between the microphone circuit 62 and the node 70 at which it is connected to the output of the low noise amplifier circuit 64.

The second interface has a fifth pin 55 which is connected to ground. This pin is connected to the outer layer of the coaxial cable between the second interface and the user equipment, and is arranged to act as a shield for micrpphone/RF cable. This defines the coaxial cable characteristic impedance for the RF and ground return for the audio signals and the low noise amplifier power.

Wires attached to the first, second and fourth pins are formed from multi stranded enamelled copper wire, for good flexibility. They are combined together with the coaxial cable into one cable which is terminated into a plug. This plugs into the phone or other user equipment.

The low noise amplifier LNA circuit 64 is incorporated into the headset microphone / volume assembly to amplify the signal from the antenna. The low noise amplifier circuit 64 is connected to the fourth pin of the first interface and thus receives the RF component received by the right cable 6 acting as an antenna. The LNA circuit 64 receives power from the pin 50 and thus amplifies the received RF signal. The amplified RF signal is combined at point 70 with the output of the microphone circuit 62 and is output via pin 52. The LNA is constructed from a common emitter amplifier 66 with series feedback between the base and collector. The RF signal is input into the base of the common emitter amplifier 66.

To avoid loss in audio signal levels, any inputs or outputs of the LNA that are connected to RF cables, which also carry audio signals, have high impedance at audio frequencies. This can be achieved in one embodiment of the invention by connecting series capacitors to the relevant inputs and outputs of the LNA. In particular, capacitors 67 and 68 are arranged in series between the input to the LNA 64 and the node 43 which connects the inductor 43 to the input 36. Capacitors 63 and 65 are arranged in series between the output of the LNA 64 and the node 70. The value of the capacitors should be chosen so that it has a low impedance at the RF frequency and high impedance at audio frequencies. In the embodiments shown in Figure 2, two capacitors in series are shown. In alternative embodiments of the invention, the two capacitors may be replaced by a single respective capacitor. In alternative embodiments of the invention, more than two capacitors may be provided.

It should be noted that the LNA circuit 64 makes the antenna into a receive only antenna.

The DAB RF signal picked up by the antenna provided by cable 8 is amplified by the LNA circuit 64. The amplified signal is multiplexed with the microphone audio signal. The microphone coaxial cable is then used to pass the RF signal and microphone signal to the handset where it is de-multiplexed back into separate RF and audio signals.

The RF signal may be multiplexed with the microphone signal using a multiplexer or simply by combining the signals at a node. A single cable thus carries the two or more different signals. This is in the cable between the LNA and the user equipment or similar device.

In other embodiments, the RF signal could be multiplexed with other convenient, audio or signal wires required to pass from the headset to handset, or indeed from the handset to headset.

There are advantages in multiplexing the audio and RF signals and using the microphone coaxial cable. A coaxial cable or other transmission line type structure is needed to pass an RF signal between two points with low loss. The outer shielding of the cable stops the signal on the inner conductor being radiated and stops other signals from outside being picked up. Using the microphone cable is therefore an efficient way of passing the RF from the LNA to the handset as it minimizes the attenuation of the low level DAB RF signal and also stops EMI radiated from the phone being picked up on the cable reducing the signal to noise ratio of the RF DAB signal.

The microphone coaxial cable is incorporated into a standard audio only headset. By multiplexing the two signals together only one coaxial cable is need in the main headset lead. This allows a reasonably standard headset cable to be used, minimizing cost and also minimizes the diameter of the cable needed.

Other types of RF transmission lines could be used instead of a coaxial cable, such as a balanced twisted pair. A balanced twisted pair transmission line could have relative low loss at the RF frequency and would resist the pick up of noise and other signals on the cable. A balanced cable may not form a counterpoise to the antenna as a coaxial cable could. Therefore if a balanced type of antenna such as a dipole is used, a balanced transmission line approach may be more appropriate than if a monopole type antenna, needing a counterpoise, is used. Thus, the connection cable comprises at least a part having RF transmission line properties.

It should be appreciated that the RF signals can additionally or alternatively be multiplexed with at least one other signal in the cable between the LNA and the respective earphone. In this example, the at least one signal may comprise an audio signal

There are advantages in using a LNA circuit. An LNA built from discrete components can have a lower noise figure than an LNA when incorporated into an integrated single chip RF receiver. This is largely as the discrete LNA is susceptible to less conducted and radiated EMI. Therefore by using a separate discrete amplifier the noise figure and therefore sensitivity of the overall receiver system is improved.

The microphone coaxial cable has some loss, typically 3dB/m at DAB Band III RF frequencies. Therefore amplifying the DAB signal before passing it down the cable helps maintain the receiver sensitivity.

By the maximum power transfer theorem, maximum power is transferred from the source to the load when the load impedance is "matched' to the source impedance, i.e. the load impedance is the complex conjugate of the source impedance. Using an appropriately designed common emitter amplifier with series feedback between the base and collector allows: • The LNA input to provide a 'matched' impedance load for the antenna.

• The LNA output to be the appropriate source impedance for the coaxial cable. The characteristic impedance of a coaxial cable is defined by its geometry and dielectric constant of the material, if any, between the inner and outer conductors. As a 'standard' coaxial cable originally designed just for audio use is being used, in some embodiments, there may be no control over defining dimensions and material type. Therefore the amplifier output impedance is matched to the coaxial's characteristic impedance.

• The LNA input and output impedance to be fairly constant over a broad frequency band.

• Series feedback makes the LNA more unilateral, the output and input are decoupled. Therefore the input impedance of the LNA is relatively unaffected by changes in the amplifier load impedance and vice versa.

The input impedance of the LNA is maintained, in preferred embodiments of the invention, even if the coaxial cable's characteristic impedance changes slightly as it is 'scrunched' up by the user, or varies due to manufacturing tolerances. This is important as any power lost in the match between the antenna and LNA has a direct effect on the sensitivity of the system.

In some embodiments, the antenna impedance will change quite radically as it moves closer or further away from the user. This change will have little effect on the match between the LNA and coaxial cable. As this match is after the LNA, any loss of power in the match between the LNA and coaxial cable will have a small effect on the system sensitivity.

The first to fifth inductors act as RF chokes, thus acting as an RF block at the desired RF frequency but allowing DC/audio to pass.

Reference is made to Figure 3 which shows a mobile telephone 90 connected to the headset of Figure 1. The mobile telephone can be replaced by any other suitable device which may or may not have wireless communication capabilities.

Thus in embodiments of the invention, there is an antenna, tuned to an operating frequency (radiates / receives radiation well at desired frequency). Antenna tuning means that its length is adjusted so that it radiates well at the desired frequency. For DAB frequencies this happens to be about the length that would be required between the speakers and microphone. The antenna is formed from one of the leads to the headphone (the cable needs to be exposed for the user to listen to radio, and therefore also a good antenna position). Audio signals are multiplexed onto the same cable which acts as an antenna, thus limiting the number of cables needed. Embodiments of the invention have the advantage that the antenna is isolated from radiated and conducted EMI, degrading system sensitivity. The headset embodying the present invention can be used with a mobile phone. There are the advantages that there is isolation from radiated and conducted EMI which degrades system sensitivity, blocking potentially caused by phone transmissions is reduced and, simultaneous phone use/DAB reception is permitted. The RF transmission line (coaxial in this embodiment) provides relatively low losses, shields signal from external EMI, and stops positive feed back across the LNA circuitry. Blocking is overloading of receiver with large signal at another frequency causing desensitization of the receiver.

Embodiments of the invention also have audio, control and DC power multiplexed onto the same cable as the RF frequency signals, having the advantages of small cable diameter, lower cost, and allows a near standard headset connector to be used. Using the LNA has the advantages that losses in transmission line cable do not degrade system sensitivity, an isolated LNA can have a better Noise Figure, and therefore better system sensitivity than one incorporated in radio receiver IC, and the isolated LNA is well away from noise current loops in the phone. In preferred embodiments of the invention, the input impedance is matched to the antenna impedance thus providing optimum power transfer between antenna and LNA and therefore maximising sensitivity. In preferred embodiments of the invention, the output impedance matched to the transmission line characteristic impedance provides optimum power transfer between the LNA and transmission line. By using an LNA design incorporating negative feedback, there are the advantages of isolating the input and output of the amplifier to minimize the effects of mismatch between the input and the antenna, and the output and the transmission line. Another advantage is that broader frequency band match is provided than that obtainable using an Open loop¹ LNA and passive massive components. There may be better defined gain than open loop design so more consistent performance e.g. for consistently meeting other receiver parameters such as adjacent channel and large signal handling which would be adversely affected by variations in the LNA gain.

In embodiments of the invention, the headset is powered from a mobile phone or other user equipment or device to which the headset is attached. By using a supply with noise filtering in the phone, it is possible to have a lower noise figure and better system sensitivity.

The LNA circuitry is preferably incorporated into headset volume/ microphone/call answering button assembly for convenience and size etc, as there is one assembly.

Preferred embodiments of the present invention use a right and a left earphone. However, in alternative embodiments of the invention, only a single earphone may be provided.

One modification to the invention is illustrated in Figure 6 which shows two antenna elements 108. The two antenna elements 108 are arranged one between each respective earphone 2a and 2b, and the circuit 6. The two antenna elements 108 could be of the same length and be used to form a dipole. Circuit 6 would be modified to incorporate a differential input. In particular, the LNA would be modified to receive a differential input.

A further modification to the invention is illustrated in Figure 7. This shows a loop antenna arrangement where the antenna is formed from the cable 107 and 109 to each earphone 2a and 2b, and also from the headband 110 joining the two earphones together. Both ends of the cable would be joined to the LNA. Thus a single cable can be used which loops for one input to the LNA, to a first earphone 2a, via the headband 110 to the second earphone 2b to a second input of the LNA.

In alternative embodiments of the invention, the antennas could be of different lengths, or different apparent electrical lengths, and therefore tuned to receive different frequencies. In one embodiment, shown in Figure 8, a first embodiment, a cable 120 is of a first electrical length and connected to the first earphone 2a whilst a second cable 122 is of a second electrical length and connected to the second earphone 2b. In this embodiment, both antennas are couple to the input of the LNA. 124.

Figure 9 shows a modification to the arrangement of Figure 8, two LNAs 126 and 128 are used. Each LNA would amplify the signal from a single antenna minimising the interactions between each antenna. If at different frequencies, the outputs of each LNA could be multiplexed together before connection to the transmission line. The arrangement of Figure 9 can be used with arrangements where the antennas are of the same or different electrical lengths.

A further alternative shown in Figure 10 is to implement a spatial diversity scheme where two sets of antenna 130 and 132 connected to respective LNAs 134 and 136 are used. Both antennas 130 and 132 and LNA 134 and 136 pairs operate at the same frequency. The amplified received signal at the output of each LNA 134 and 136 will vary in time as the position of the respective antenna 130 and 132 and RF field strength in a particular location changes. The outputs of the LNAs 134 and 136 could be combined by a diversity combiner 138 in several well known different ways such as maximum ratio or switched so as to maximise the signal quality and reduce the average signal strength the receiver can successfully operate in. It should be appreciated that in the description of modifications to embodiments of the present invention, reference has been made to LNAs. It should be appreciated that in practice, other elements of the circuit 6 shown in Figure 2 may, but not necessarily, be present.

Claims

CLAIMS:

1. A headset comprising: at least one earphone; at least one antenna arranged to receive radio frequency signals; and a first cable arranged to carry multiplexed signals, said multiplexed signals comprising said radio frequency signals and at least one other signal.

2. A headset as claimed in claim 1, comprising low noise amplifier circuitry for amplifying the received radio frequency signals

3. A headset as claimed in claim 2, wherein said antenna comprises a cable, coupled between one earphone and said low noise amplifier circuitry.

4. A headset as claimed in claim, wherein said cable coupled between one earphone and said low noise amplifier comprises said first cable.

5. A headset as claimed in claims 2, 3 or 4, wherein two earphones are provided and said antenna comprises two cables, one end of each cable being coupled differentially to the low noise amplifier circuitry to form a dipole antenna, the other end of each cable being coupled to a respective one of said earphones.

6. A headset as claimed in claims 2, 3 or 4, wherein said antenna comprises a single cable, in which a first end and a second end of the single cable is coupled differentially to the low noise amplifier circuitry to form a loop antenna, at least one earphone being coupled to the cable at a location -between said first and second ends.

7 A headset as claimed in any of claims 1 to 4, wherein two antennas are provided.

8. A headset as claimed in claim 7, wherein said antennas comprise respective cables, each antenna being coupled to a respective earphone.

9. A headset as claimed in claim 7 or 8, when appended to claim 2, wherein said first and second antennas are coupled together at an input of a low noise amplifier of said low noise amplifier circuitry.

10. A headset as claimed in claims 7, 8 or 9, when appended to claim 2, wherein said low nose amplifier circuitry comprises a first and a second low noise amplifier, each one of said antennas being connected to a respective one of said first and second low noise amplifiers.

11. A headset as claimed in any preceding claim, wherein at least one antenna is arranged to provide audio signals to an earphone connected thereto.

12 A headset as claimed in claim 3 or any claim appended thereto, comprising component means for adjusting an electrical length of at least one of said antennas.

13. A headset as claimed in claim 12, wherein said component means comprises at least one of electrical tuning components for increasing said electrical length.

14. A headset as claimed in claim 12 or 13, wherein said component means comprises resonant circuitry for decreasing said electrical length.

15 A headset as claimed in any preceding claim, wherein said first cable is configured to connect said headset to a further device.

16. A headset as claimed in claim 15, wherein said first cable is arranged, in use, to provide radio frequency signals from the LNA to said further device.

17. A headset as claimed in claim 16, wherein said first cable is arranged to provide said at least one other signal to and/or from said further device.

18. A headset as claimed in any of claims 15 to 17, wherein said first cable is arranged, in use, to provide headset signals to said headset from said further device, said headset signals comprising said at least one other signal.

19. A headset as claimed in claim 18, wherein headset signals comprise at least one of audio signals to be output by at least one earphone, power for powering said headset, and control signals.

20. A headset as claimed in any preceding claim, comprising microphone circuitry.

21. A headset as claimed in claim 20, wherein said at least one signal comprise output signals from said microphone circuitry.

22. A headset as claimed in any preceding claim, wherein said first cable comprises at least a coaxial cable.

23. A headset as claimed in claimed in claim 22, where an outer screen of the coaxial cable forms at least part of a counterpoise for the antenna.

24. A headset as claimed in any of claims 1 to 21, wherein said first cable comprises at least a balanced structure.

25. A headset as claimed in claim 2 or any claim appended thereto, wherein said low noise amplifier circuitry is provided by discrete components.

26. A headset as claimed in claim 2 or any claim appended thereto, wherein said low noise amplifier circuitry comprises a common emitter amplifier.

27. A headset as claimed in claim 2 or any claim appended thereto, wherein said low noise amplifier circuitry comprises negative feedback.

28. A headset as claimed in claim 2 or any claim appended thereto, wherein said low noise amplifier circuitry is arranged such that input impedance thereof is matched to impedance of said antenna.

29. A headset as claimed in claim 2 or any claim appended thereto, wherein said low noise amplifier circuitry is arranged such that output impedance is matched to said first cable.

30. A headset as claimed in claim 2 or any claim appended thereto, wherein said low noise amplifier circuitry comprises series feedback.

31. A headset as claimed in claim 2 or any claim appended thereto, wherein said low noise amplifier circuitry is arranged to be incorporated into an assembly comprising at least one of: a headset volume controller; microphone circuitry; and call answering circuitry.

32. In combination, a headset as claimed in any previous claim and a device.

33. A combination as claimed in claim 32, wherein said device comprises a radio receiver.

34. A combination as claimed in claim 32 or claim 33, wherein said device is capable of wireless communications.

35. A combination as claimed in any of claims 32 to 34, wherein said device is arranged to power said headset, in use.

36. A headset comprising: at least one earphone; at least one antenna arranged to receive radio frequency signals; low noise amplifier circuitry for amplifying the received radio frequency signals.

37. A headset comprising: at least one earphone; at least one antenna arranged to receive radio frequency signals, said at least one antenna comprising a cable; low noise amplifier circuitry for amplifying the received radio frequency signals, said cable providing said antenna being coupled between one earphone and said low noise amplifier circuitry; and a connection cable coupled at one end to said low noise amplifier circuitry and at the other end being connectable to a device, wherein at least one of said connection cable and said cable providing said antenna is arranged to carry said radio frequency signals multiplexed with at least one other signal.